Optical detection and measurement of hematocrit and free hemoglobin concentration

Background

Field of the Disclosure

0001The present disclosure relates to optical detection and measurement of hematocrit and free hemoglobin concentration. More particularly, the present disclosure relates to non-invasive colorimetric approaches to measuring hematocrit and free hemoglobin concentration using diffuse reflectance spectroscopy.

Description of Related Art

0002Various blood processing systems now make it possible to collect particular blood constituents, instead of whole blood, from a blood source such as, but not limited to, a container of previously collected blood or other living or non-living source. Typically, in such systems, whole blood is drawn from a blood source, the particular blood component or constituent is separated, removed, and collected, and the remaining blood constituents are returned to the blood source. Removing only particular constituents is advantageous when the blood source is a human donor, because potentially less time is needed for the donor's body to return to predonation levels, and donations can be made at more frequent intervals than when whole blood is collected. This increases the overall supply of blood constituents, such as plasma and platelets, made available for transfer and/or therapeutic treatment.

0003Whole blood is typically separated into its constituents (e.g., red cells, platelets, and plasma) through centrifugation, such as in the AMICUS® separator from Fenwal, Inc. of Lake Zurich, III., which is an affiliate of Fresenius Kabi AG of Bad Homburg, Germany, or other centrifugal separation devices, or a spinning membrane-type separator, such as the AUTOPHERESIS-C® and AURORA® devices from Fenwal, Inc.

0004Systems of this type typically include one or more optical devices for monitoring the composition of the blood or a component thereof. One common approach to non-invasive blood and blood constituent analysis is based on the amount of light transmitted through the fluid. Different blood constituents absorb different wavelengths of light to different degrees, which may be used to determine certain characteristics of a fluid. However, light transmission through fluid containing even low quantities of red blood cells (i.e., fluids having a relatively low hematocrit) may be minimal due to significant scattering of the light. Another possible disadvantage of such transmission-based approaches is that they require access to opposing sides of a fluid path, which may not be available for certain fluid paths in certain systems.

0005<patcit id="pcit0001" dnum="US9164078B"><text>U.S. Patent No. 9,164,078</text></patcit> describes a system in which hematocrit of whole blood may be predicted using infrared light. The hematocrit of whole blood is useful information to have for an apheresis system and method because it indicates the red blood cell and plasma quantities available for collection, while the hematocrit of a separated blood component indicate the purity of a component that should contain red blood cells or the contamination of a component that should be free of red blood cells. Furthermore, when mononuclear cells are to be collected, the hematocrit of fluid exiting a separation device may be indicative of the quantity of mononuclear cells exiting the separation device.

0006The optical devices of these systems may also be configured for measuring the concentration of free hemoglobin of a constituent fluid. For example, <patcit id="pcit0002" dnum="US9833557B"><text>U.S. Patent No. 9,833,557</text></patcit> describes a system in which the concentration of free hemoglobin in separated plasma may be determined, followed by the determination of an amount of free hemoglobin in a concentrated fluid separated from the plasma. Reliable measurement of free hemoglobin concentration of separated plasma, for example, is useful in determining whether red blood cells are being damaged during separation.

0007Conventional approaches to free hemoglobin detection involve the measurement of red and green light transmitted through a fluid. While such techniques are capable of producing reliable results, they may be susceptible to disturbances, such as when air bubbles are present in the fluid. When light being transmitted through a fluid encounters air bubbles, the light is scattered, which reduces the amount of light transmitted through the fluid to a light detector and may lead to erroneous measurements. Additionally, plasma or supernatant obtained from a product after separation or during storage is conventionally evaluated using specific free hemoglobin measurement assays, which may be time-consuming and costly. Further, as noted above, it may be impracticable to access opposing sides of a fluid-containing vessel, as required for transmission-based approaches.

Summary

0008There are several aspects of the present subject matter which may be embodied separately or together in the devices and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto.

0009In one aspect, a method of measuring a hematocrit or a free hemoglobin concentration of a fluid includes providing a fluid in a vessel. The fluid in the vessel is exposed to a light emitted by a broadband light source so as to cause at least a portion of the light to be reflected by the fluid. At least a portion of the reflected light is received, with at least a portion of the received light being analyzed to determine a main wavelength of the received light. The main wavelength is correlated to a hematocrit or a free hemoglobin concentration, with an output indicative of the hematocrit or the free hemoglobin concentration corresponding to the main wavelength being generated.

0010In another aspect, a colorimetric optical sensor device is configured for use in combination with a fluid-containing vessel. The colorimetric optical sensor device includes a broadband light source configured to emit a light, with at least a portion of the light being exposed to a fluid in the vessel and reflected. An optical spectrometer is configured to receive at least a portion of the reflected light and analyze at least a portion of the received light to determine a main wavelength of the received light. A controller is configured to correlate the main wavelength to a hematocrit or a free hemoglobin concentration and generate an output indicative of the hematocrit or the free hemoglobin concentration corresponding to the main wavelength.

0011These and other aspects of the present subject matter are set forth in the following detailed description of the accompanying drawings.

Brief Description of the Drawings

0012<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a side elevation view, with portions broken away and in section, of a centrifugal fluid separation assembly employing aspects of the present disclosure, with a centrifuge bowl and spool of the assembly being shown in their operating position;</li><li><figref idref="f0002">Fig. 2</figref> is a side elevation view, with portions broken away and in section, of the assembly shown in <figref idref="f0001">Fig. 1</figref>, with the bowl and spool shown in an upright position for receiving a separation chamber;</li><li><figref idref="f0003">Fig. 3</figref> is a top perspective view of the spool of the centrifuge shown in <figref idref="f0002">Fig. 2</figref> in its upright position and carrying the separation chamber;</li><li><figref idref="f0003">Fig. 4</figref> is a plan view of the separation chamber shown in <figref idref="f0003">Fig. 3</figref>, out of association with the spool;</li><li><figref idref="f0004">Fig. 5</figref> is an enlarged perspective view of an interface ramp carried by the centrifuge in association with the separation chamber, showing the centrifugally separated red blood cell layer, plasma layer, and interface within the separation chamber when in a desired location on the ramp;</li><li><figref idref="f0004">Fig. 6</figref> is an enlarged perspective view of the interface ramp shown in <figref idref="f0004">Fig. 5</figref>, showing the red blood cell layer and interface at an undesired high location on the ramp;</li><li><figref idref="f0004">Fig. 7</figref> is an enlarged perspective view of the interface ramp shown in <figref idref="f0004">Fig. 5</figref>, showing the red blood cell layer and interface at an undesired low location on the ramp;</li><li><figref idref="f0005">Fig. 8</figref> is a side perspective view of the bowl and spool of the centrifuge when in the operating position, showing a viewing head, which forms a part of an interface controller, being carried by the centrifuge to view the interface ramp during rotation of the bowl;</li><li><figref idref="f0005">Fig. 9</figref> is a perspective view of the viewing head, with portions broken away and in section, showing the light source and light detector, which are carried by the viewing head, in alignment with the interface ramp, as viewed from within the spool and bowl of the centrifuge;</li><li><figref idref="f0005">Fig. 10</figref> is a side section view of the bowl, spool, and viewing head when the viewing head is aligned with the interface ramp;</li><li><figref idref="f0006">Fig. 11</figref> is a schematic view of components of the interface controller including a colorimetric optical sensor device;</li><li><figref idref="f0007">Fig. 12</figref> is a front elevational view of an exemplary disposable fluid flow circuit that may be used in combination with the separation assembly of <figref idref="f0001">Figs. 1</figref> and <figref idref="f0002">2</figref> for carrying out biological fluid separation procedures according to the present disclosure;</li><li><figref idref="f0008">Fig. 13</figref> is a schematic view of light from a broadband light source of the colorimetric optical sensor device of <figref idref="f0006">Fig. 11</figref> entering into a fluid-containing vessel;</li><li><figref idref="f0008">Fig. 14</figref> is a cross-sectional view of an optical bundle of the colorimetric optical sensor device of <figref idref="f0006">Fig. 11</figref>;</li><li><figref idref="f0009">Fig. 15</figref> is a schematic view of light reflecting off of the fluid in the vessel of <figref idref="f0008">Fig. 13</figref> for receipt and analysis by the colorimetric optical sensor device of <figref idref="f0006">Fig. 11</figref>;</li><li><figref idref="f0009">Fig. 16</figref> is a chart illustrating an exemplary optical spectrum produced by a colorimetric optical sensor device in measuring the hematocrit of a fluid;</li><li><figref idref="f0010">Fig. 17</figref> is a chart illustrating an exemplary optical spectrum produced by a colorimetric optical sensor device in measuring the free hemoglobin concentration of a fluid;</li><li><figref idref="f0010">Figs. 18</figref> and <figref idref="f0011">19</figref> are charts illustrating a relationship between the main wavelength of a broadband light reflected by a fluid and the hematocrit of that fluid; and</li><li><figref idref="f0011">Fig. 20</figref> is a chart illustrating a relationship between the main wavelength of a broadband light reflected by a fluid and the free hemoglobin concentration of that fluid.</li></ul>

Description of the Illustrated Embodiments

0013The embodiments disclosed herein are for the purpose of providing a description of the present subject matter, and it is understood that the subject matter may be embodied in various other forms and combinations not shown in detail. Therefore, specific designs and features disclosed herein are not to be interpreted as limiting the subject matter as defined in the accompanying claims.

0014<figref idref="f0001">Figs. 1</figref> and <figref idref="f0002">2</figref> show a biological fluid processing system that may be used in practicing the hematocrit and free hemoglobin concentration measurement principles of the present disclosure. The system is currently marketed as the AMICUS® separator of Fenwal, Inc. and is described in greater detail in <patcit id="pcit0003" dnum="US5868696A"><text>U.S. Patent No. 5,868,696</text></patcit>. The system can be used for processing various fluids, but is particularly well suited for processing whole blood, blood components, or other suspensions of biological cellular materials. While hematocrit and free hemoglobin concentration principles will be described herein with reference to one particular system, it should be understood that these principles may be employed with other biological fluid processing systems without departing from the scope of the present disclosure. For example, these principles may be practiced with other centrifugal separation systems (including those of the type described in greater detail in <patcit id="pcit0004" dnum="US7297272B"><text>U.S. Patent No. 7,297,272</text></patcit>, with "spinning membrane"-type separation systems (including those of the type described in greater detail in <patcit id="pcit0005" dnum="US9895482B"><text>U.S. Patent No. 9,895,482</text></patcit> and <patcit id="pcit0006" dnum="WO2017048673A1A"><text>PCT Patent Application Publication No. WO 2017/048673 A1</text></patcit>,), and with biological fluid separation systems based on other separation principles.

A. The Centrifuge

0015The biological fluid processing system comprises a reusable hardware component or separation assembly 10 (<figref idref="f0001">Figs. 1</figref> and <figref idref="f0002">2</figref>) and a disposable fluid flow circuit 12 (<figref idref="f0007">Fig. 12</figref>) that is configured to be mounted to the separation assembly 10 during use. The illustrated separation assembly 10 includes a separation device 14 (illustrated as a centrifuge) used to separate a biological fluid into two or more fluid components or constituents. The separation assembly 10 may be programmed to separate blood or a biological fluid into a variety of components (e.g., platelet-rich plasma and red blood cells), with an exemplary mononuclear cell ("MNC") collection procedure, in which the system separates and collects MNCs (e.g., lymphocytes and monocytes) from whole blood, being described herein. As noted above, it should be understood that centrifugation is only one possible separation technique that may be practiced in combination with the hematocrit and free hemoglobin concentration measurement principles described herein.

0016The illustrated centrifuge 14 is of the type shown in <patcit id="pcit0007" dnum="US5316667A"><text>U.S. Patent No. 5,316,667</text></patcit>. The centrifuge 14 comprises a bowl 16 and a spool 18. The bowl 16 and spool 18 are pivoted on a yoke 20 between an operating position (<figref idref="f0001">Fig. 1</figref>) and a loading/unloading position (<figref idref="f0002">Fig. 2</figref>).

0017When in the loading/unloading position, the spool 18 can be opened by movement at least partially out of the bowl 16, as <figref idref="f0002">Fig. 2</figref> shows. In this position, the operator wraps a flexible separation chamber 22 (see <figref idref="f0003">Fig. 3</figref>) of the fluid flow circuit 12 about the spool 18. Closure of the spool 18 and bowl 16 encloses the chamber 22 for processing. When closed, the spool 18 and bowl 16 are pivoted into the operating position of <figref idref="f0001">Fig. 1</figref> for rotation about an axis.

B. The Separation Chamber

0018The separation chamber 22 can be variously constructed. <figref idref="f0003">Fig. 4</figref> shows a representative embodiment, while <figref idref="f0007">Fig. 12</figref> shows the separation chamber 22 in the context of a disposable fluid flow circuit 12 that is configured for use in combination with the separation assembly 10 to define a fluid flow path for a biological fluid (e.g., blood), separated fluid components or constituents (e.g., separated blood components), and other fluids (e.g., anticoagulant). It should be understood that the hematocrit and free hemoglobin concentration measurement techniques described herein are not limited to monitoring of any particularly configured extracorporeal biological fluid flow circuit, but may be applied to any fluid flow circuit having an optically appropriate portion or vessel or any other optically appropriate fluid-containing vessel.

0019The chamber 22 shown in <figref idref="f0003">Fig. 4</figref> allows for either single- or multi-stage processing. When used for multi-stage processing, a first stage 24 separates a biological fluid (e.g., whole blood) into first and second components. Depending on the nature of the separation procedure, one of the components may be transferred into a second stage 26 for further separation. When used for single-stage processing, only the first stage 24 is used for separating a biological fluid into its constituents, while the second stage 26 may be filled with saline or the like to balance the chamber 22.

0020As <figref idref="f0003">Figs. 3 and 4</figref> best show, there are three ports 28, 30, and 32 associated with the first stage 24. Depending on the particular biological fluid processing procedure, the ports may have different functionality but, in an MNC collection procedure, the port identified at 28 is used for conveying fluids into the first stage 24. During such an MNC collection procedure, the other two ports 30 and 32 serve as outlet ports for separated fluid components exiting the first stage 24. More particularly, the first outlet port 30 conveys a low density fluid component from the first stage 24, while the second outlet port 32 conveys a high density fluid component from the first stage 24.

0021In a method of carrying out single-stage processing, at least a portion of one or more of the separated components is returned to the fluid source or to some other recipient (either of which may be a living patient or donor or a non-living source, such as a fluid container), while at least a portion of at least one of the other separated components is removed from the first stage 24 and stored. For example, a conventional MNC collection procedure (as described in greater detail in <patcit id="pcit0008" dnum="US5980760A"><text>U.S. Patent No. 5,980,760</text></patcit>) begins with a plasma collection phase. During this initial phase, whole blood in the first stage 24 is separated into a plasma constituent (i.e., a low density component, which may include platelets), an interface or buffy coat or MNC-containing layer (i.e., an intermediate density component, which includes MNCs and may also include smaller red blood cells), and packed red blood cells (i.e., a high density component). The plasma constituent and packed red blood cells are removed from the first stage 24 (via the first and second outlet ports 30 and 32, respectively), while the MNC-containing layer builds up in the first stage 24. The plasma constituent is collected, while the packed red blood cells are returned to the blood source.

0022When a target amount of plasma has been collected, an MNC accumulation phase begins. During this phase, the position of the interface within the first stage 24 is moved closer to the spool 18, such that platelet-rich plasma and packed red blood cells are removed from the first stage 24 (via the first and second outlet ports 30 and 32) while the MNC-containing layer continues to build up in the first stage 24. Portions of the platelet-rich plasma and the packed red blood cells are returned to the blood source, with the remainder of the platelet-rich plasma and packed red blood cells being recirculated through the first stage 24 to maintain a proper hematocrit.

0023When a target or preselected amount of blood has been processed, the assembly 10 transitions to a red blood cell collection phase. During this phase, blood separation continues as in the MNC accumulation phase, with recirculation and return of the platelet-rich plasma continuing, while the separated red blood cells are conveyed from the first stage 24 and collected for later use rather than being recirculated or returned to the source.

0024When a target amount of red blood cells have been collected, the assembly 10 transitions to an MNC harvest phase. To harvest the MNCs in the MNC-containing layer, the second outlet port 32 is closed to temporarily prevent packed red blood cells from exiting the first stage 24. At least a portion of the collected red blood cells is conveyed into the first stage 24 via the inlet port 28, which forces the MNC-containing layer to exit the first stage 24 via the first outlet port 30 for collection in an MNC collection container as an MNC product.

0025Following the MNC harvest phase, a plasma flush phase begins. During this phase, collected plasma is used to flush any MNC-containing layer positioned between the separation chamber 22 and the MNC collection container back into the first stage 24. A portion of the collected plasma may be conveyed into the MNC collection container as a storage or suspension medium for the MNC product.

0026If additional MNC product is to be collected, the various phases may be repeated. Following collection, the MNC product may be treated to further processing, such as extracorporeal photopheresis.

0027In a different separation procedure, in which multi-stage processing is required, one of the separated fluid components or constituents will be transferred from the first stage 24 to the second stage 26 via a port 34 associated with the second stage 26. The component transferred to the second stage 26 is further fractionated into sub-components, with one of the sub-components being removed from the second stage 26 via an outlet port 36 and the other sub-component remaining in the second stage 26.

0028As best shown in <figref idref="f0003">Fig. 3</figref>, a tubing umbilicus 38 is attached to the ports 28, 30, 32, 34, and 36. The umbilicus 38 interconnects the first and second stages 24 and 26 with each other and with pumps and other stationary components located outside the rotating components of the centrifuge 14 (not shown). As <figref idref="f0001">Fig. 1</figref> shows, a non-rotating (zero omega) holder 40 holds the upper portion of the umbilicus 38 in a non-rotating position above the spool 18 and bowl 16. A holder 42 on the yoke 20 rotates the mid-portion of the umbilicus 38 at a first (one omega) speed about the suspended spool 18 and bowl 16. Another holder 44 (<figref idref="f0002">Figs. 2</figref> and <figref idref="f0003">3</figref>) rotates the lower end of the umbilicus 38 at a second speed twice the one omega speed (the two omega speed), at which speed the spool 18 and bowl 16 also rotate. This known relative rotation of the umbilicus 38 keeps it untwisted, in this way avoiding the need for rotating seals.

0029As <figref idref="f0003">Fig. 4</figref> shows, a first interior seal 46 is located between the low density outlet port 30 and the inlet port 28. A second interior seal 48 is located between the inlet port 28 and the high density outlet port 32. The interior seals 46 and 48 form a fluid passage 50 (an inlet for whole blood or the like) and a low density collection region 52 in the first stage 24. The second seal 48 also forms a fluid passage 54 (a high density blood component outlet in an MNC collection procedure) in the first stage 24.

0030In an MNC collection procedure, the fluid passage 50 channels blood directly into the circumferential flow path immediately next to the low density collection region 52. As shown in <figref idref="f0004">Fig. 5</figref>, the blood separates into an optically dense layer 56 containing cellular components, which forms as cellular components move under the influence of centrifugal force toward the high-G (outer) wall 62. The optically dense layer 56 will include red blood cells (and, hence, will be referred to herein as the "RBC layer") but, depending on the speed at which the centrifuge 14 is spun, other cellular components (e.g., larger white blood cells and platelets) may also be present in the RBC layer 56.

0031The movement of the component(s) of the RBC layer 56 displaces less dense blood components radially toward the low-G (inner) wall 64, forming a second, less optically dense layer 58. The less optically dense layer 58 includes plasma (and, hence, will be referred to herein as the "plasma layer or plasma constituent") but, depending on the speed at which the centrifuge 14 is rotated and the length of time that the blood is resident in the centrifuge, other components (e.g., smaller platelets) may also be present in the plasma layer 58.

0032The transition between the RBC layer 56 and the plasma layer 58 is generally referred to as the interface or buffy coat or MNC-containing layer 60, as described above and shown in <figref idref="f0004">Fig. 5</figref>. Platelets and white blood cells (including MNCs) typically occupy this transition region.

0033The location of the interface 60 within the chamber 22 can dynamically shift during blood processing, as <figref idref="f0004">Figs. 6 and 7</figref> show. If the location of the interface 60 is too high (that is, if it is too close to the low-G wall 64 and the removal port 30, as <figref idref="f0004">Fig. 6</figref> shows), red blood cells can spill over and into the low density collection region 52, adversely affecting the quality of the plasma constituent 58. On the other hand, if the location of the interface 60 is too low (that is, if it resides too far away from the low-G wall 64, as <figref idref="f0004">Fig. 7</figref> shows), the collection efficiency of the assembly 10 may be impaired.

0034As <figref idref="f0004">Fig. 5</figref> shows, a ramp 66 extends from the high-G wall 62 of the bowl 16 at an angle across the low density collection region 52. The angle, measured with respect to the axis of the first outlet port 30 is about 30° in one embodiment. <figref idref="f0004">Fig. 5</figref> shows the orientation of the ramp 66 when viewed from the low-G wall 64 of the spool 18. <figref idref="f0003">Fig. 4</figref> shows, in phantom lines, the orientation of the ramp 66 when viewed from the high-G wall 62 of the bowl 16.

0035Further details of the angled relationship of the ramp 66 and the first outlet port 30 can be found in <patcit id="pcit0009" dnum="US5632893A"><text>U.S. Patent No. 5,632,893</text></patcit>.

0036The ramp 66 forms a tapered wedge that restricts the flow of fluid toward the first outlet port 30. The top edge of the ramp 66 extends to form a constricted passage 68 along the low-G wall 64. The plasma layer 58 must flow through the constricted passage 68 to reach the first outlet port 30.

0037As <figref idref="f0004">Fig. 5</figref> shows, the ramp 66 makes the interface 60 between the RBC layer 56 and the plasma layer 58 more discernible for detection, displaying the RBC layer 56, plasma layer 58, and interface 60 for viewing through the high-G wall 62 of the chamber 22.

0038Further details of the separation chamber 22 and its operation may be found in <patcit id="pcit0010" dnum="US5316667A"><text>U.S. Patent No. 5,316,667</text></patcit>.

C. The Interface Controller

0039An interface controller (<figref idref="f0006">Fig. 11</figref>) includes a viewing head or interface optical sensor device 70 carried on the yoke 20 (see <figref idref="f0001">Figs. 1</figref> and <figref idref="f0005">8</figref>) and a colorimetric optical sensor device 72, which is shown as being associated with tubing connected to the first outlet port 30 (but which may be variously positioned, as will be described in greater detail herein). Alternatively, rather than being carried on the yoke 20, the interface optical sensor device 70 may be mounted to a radial location of the centrifuge bucket or enclosure, as described in <patcit id="pcit0011" dnum="US20140057771A"><text>U.S. Patent Application Publication Nos. 2014/0057771</text></patcit> and <patcit id="pcit0012" dnum="US20150219558A"><text>2015/0219558</text></patcit>. The interface optical sensor device 70 is oriented to optically view the transition in optical density between the RBC layer 56 and the plasma layer 58 on the ramp 66. The colorimetric optical sensor device 72 measures the hematocrit and/or free hemoglobin concentration of fluid in an associated portion or vessel of the fluid flow circuit 12 (fluid flowing out of the first stage 24 via the first outlet port 30 in the illustrated embodiment), as will be described in greater detail herein.

0040The interface controller is functional to determine the location of the interface 60 on the ramp 66 and, if the interface 60 is located at an improper location (e.g., in the locations of <figref idref="f0004">Figs. 6 or 7</figref>), to correct the location of the interface 60.

(1) The Interface Optical Sensor Device

0041Referring to <figref idref="f0005">Figs. 8-10</figref>, the interface optical sensor device 70, carried by the yoke 20 or mounted to a stationary radial location of the centrifuge bucket or enclosure, includes a light source 74, which emits light that is scattered and absorbed by red blood cells. In the illustrated embodiment, the light source 74 includes a circular array of red light emitting diodes 76, but other wavelengths scattered or absorbed by red blood cells, like green or infrared, could also be used.

0042In the illustrated embodiment, seven light emitting diodes 76 comprise the light source 74. More diodes 76 may be used, or fewer diodes 76 can be used, depending upon the optical characteristics desired. Further, non-LED lights may also be employed without departing from the scope of the present disclosure.

0043The interface optical sensor device 70 also includes a light detector 78 (<figref idref="f0005">Figs. 9 and 10</figref>), which is mounted adjacent to the light source 74. In one embodiment, the light detector 78 comprises a PIN diode detector, which is located generally in the geometric center of the circular array of light emitting diodes 76. Other types of light detectors may also be employed.

0044If mounted to the yoke 20, the yoke 20 and the interface optical sensor device 70 rotate at a one omega speed, as the spool 18 and bowl 16 rotate at an average speed of two omega. If mounted to a stationary portion of the centrifuge bucket or enclosure, the interface optical sensor device 70 remains stationary while the yoke 20 rotates at a one omega speed and the spool 18 and bowl 16 rotate at an average speed of two omega. The light source 74 directs light onto the rotating bowl 16. In the illustrated embodiment, the bowl 16 is transparent to the light emitted by the source 74 only in the region 80 where the bowl 16 overlies the interface ramp 66 (<figref idref="f0005">Fig. 8</figref>). In the illustrated embodiment, the region 80 comprises a window cut out in the bowl 16. The remainder of the bowl 16 that lies in the path of the interface optical sensor device 70 comprises an opaque or light absorbing material.

0045The interface ramp 66 is made of a light transmissive material. The light from the source 74 will thereby pass through the transparent region 80 of the bowl 16 and the ramp 66 every time the rotating bowl 16 and interface optical sensor device 70 align. The spool 18 may also carry a light reflective material 82 (<figref idref="f0005">Figs. 9 and 10</figref>) behind the interface ramp 66 to enhance its reflective properties. The spool 18 reflects incoming light received from the source 74 out through the transparent region 80 of the bowl 16, where it is sensed by the detector 78. In the illustrated embodiment, light passing outward from the source 74 and inward toward the detector 78 passes through a focusing lens 84 (shown in <figref idref="f0005">Figs. 9 and 10</figref>), which forms a part of the viewing head 70.

0046Such an arrangement optically differentiates the reflective properties of the interface ramp 66 from the remainder of the bowl 16. This objective can be achieved in other ways. For example, the light source 74 could be gated on and off with the arrival and passage of the ramp 66 relative to its line of sight. As another example, the bowl 16 outside the transparent region 80 could carry a material that reflects light, but at a different intensity than the reflective material 82 behind the interface ramp 66.

0047As the transparent interface region 80 of the bowl 16 comes into alignment with the interface optical sensor device 70, the detector 78 will first sense light reflected through the plasma layer 58 on the ramp 66. Eventually, the RBC layer 56 adjacent the interface 60 on the ramp 66 will enter the optical path of the interface optical sensor device 70. The RBC layer 56 scatters and absorbs light from the source 74 and thereby reduces the previously sensed intensity of the reflected light. The length of time that the higher intensity of reflected light is sensed by the detector 78 represents the amount of light from the source 74 that is not scattered or absorbed by the RBC layer 56 adjacent to the interface 60. With this information, a processing element or module 86 (<figref idref="f0006">Fig. 11</figref>) can determine the location of the interface 60 on the ramp 66 relative to the constricted passage 68. A more detailed discussion of the algorithms by which the interface controller receives and processes signals to determine the location of the interface 60 on the ramp 66 may be found in <patcit id="pcit0013" dnum="US6312607B"><text>U.S. Patent No. 6,312,607</text></patcit>.

0048When the location of the interface 60 on the ramp 66 has been determined, the processing element 86 outputs that information to an interface command element or module 88 (<figref idref="f0006">Fig. 11</figref>). The command element 88 includes a comparator, which compares the interface location output with a desired interface location to generate an error signal. The error signal may take a number of forms but, in one embodiment, is expressed in terms of a targeted red blood cell percentage value (i.e., the percentage of the ramp 66 which should be occupied by the RBC layer 56).

0049When the control value is expressed in terms of a targeted red blood cell percentage value, a positive error signal indicates that the RBC layer 56 on the ramp 66 is too small (as <figref idref="f0004">Fig. 7</figref> shows). The interface command element 88 generates a signal to adjust an operational parameter accordingly, such as by increasing the rate at which plasma is removed through the first outlet port 30 under action of a pump 90 (<figref idref="f0006">Fig. 11</figref>). The interface 60 moves toward the constricted passage 68 to the desired control position (as <figref idref="f0004">Fig. 5</figref> shows), where the error signal is zero.

0050A negative error signal indicates that the RBC layer 56 on the ramp 66 is too large (as <figref idref="f0004">Fig. 6</figref> shows). The interface command element 88 generates a signal to adjust an operational parameter accordingly, such as by decreasing the rate at which plasma is removed through the first outlet port 30. The interface 60 moves away from the constricted passage 68 to the desired control position (<figref idref="f0004">Fig. 5</figref>), where the error signal is again zero.

(2) The Colorimetric Optical Sensor Device

0051The interface controller may further include a colorimetric optical sensor device 72 (<figref idref="f0006">Fig. 11</figref>), which is shown as being configured to monitor the fluid exiting the first stage 24 of the separation chamber 22 via the first outlet port 30. The fluid exiting the first stage 24 via the first outlet port 30 is typically platelet-poor plasma or platelet-rich plasma, but depends on the procedure being executed by the system. For example, the MNC-containing layer will and the RBC layer may exit the first outlet port 30 during the MNC harvest phase of an MNC collection procedure of the type described herein.

0052While the colorimetric optical sensor device 72 is shown as monitoring a tube 92 connected to the first outlet port 30, it should be understood that the colorimetric optical sensor device 72 may be located and configured to monitor fluid in any optically appropriate portion or vessel of the fluid flow circuit 12. This may include vessels in which fluid is in motion (e.g., flowing through a tube or through the separation chamber 22 or a cassette) and vessels in which fluid is substantially stationary (e.g., a collection or storage bag or container or a cuvette or test tube), as well as vessels positioned either upstream or downstream of the separation chamber 22. Furthermore, while the illustrated colorimetric optical sensor device 72 is shown as being incorporated into the interface controller, it is also within the scope of the present disclosure for the colorimetric optical sensor device 72 to be separately provided and either work cooperatively with the interface controller or entirely independently.

0053The colorimetric optical sensor device 72 detects the color of the fluid in the associated vessel of the fluid flow circuit 12 to assess the hematocrit and/or free hemoglobin concentration of the fluid. If platelet-poor plasma or some other cell-free supernatant is present in the vessel and the color of the fluid is more red than it should be, then it may be indicative of conditions of hemolysis or contamination by red blood cells. The colorimetric optical sensor device 72 may also detect a change in the nature of the fluid exiting the first outlet port 30, such as when the fluid transitions from the MNC-containing layer to the RBC layer during the MNC harvest phase of an MNC collection procedure. The information obtained and output by the colorimetric optical sensor device 72 may be used to modify the separation procedure, such as by changing the speed at which a pump 90 operates or causing the transition from one phase of a separation procedure to another phase. For example, if the output is indicative of the presence of red blood cells in a subject fluid that is intended to be substantially free of red blood cells, the output may be used modify the separation procedure in a way that reduces contamination of the fluid by red blood cells (e.g., by moving the position of the interface 60 within the separation chamber 22). If the output is indicative of an elevated free hemoglobin concentration, the output may be used to modify the separation procedure in a way that reduces the incidence of hemolysis (e.g., by reducing the rate at which the separation device is rotated).

0054The colorimetric optical sensor device 72 includes a broadband light source 94, an optical spectrometer 96, and a controller 98. The broadband light source 94 is configured to emit a light including at least all wavelengths in the visible range (from approximately 400 nm to approximately 700 nm), but may also include wavelengths above and/or below the visible range. In one embodiment, the broadband light source 94 is provided as a stabilized tungsten-halogen light source (configured to emit a light having all wavelengths between 360 nm and 2600 nm) of the type marketed by Thorlabs, Inc. of Newton, New Jersey, but the broadband light source 94 may also be differently configured without departing from the scope of the present disclosure.

0055The broadband light source 94 is oriented to emit light toward a vessel of the fluid flow circuit 12 (the tube 92 in <figref idref="f0006">Fig. 11</figref>) in which fluid is present. <figref idref="f0008">Fig. 13</figref> shows the light 100 emitted by the broadband light source 94, with a first portion 102 of the light 100 reflecting off of a surface 104 of the vessel 106 (specular reflection), while a second portion 108 of the light 100 is transmitted through the surface 104 and into the vessel 106. As shown in <figref idref="f0006">Figs. 11</figref> and <figref idref="f0008">13</figref>, the light 100 may be directed to strike the surface 104 of the vessel 106 at an angle θ, which may be selected to reduce the degree of specular reflection. For example, if the angle θ is 90°, there will tend to be a significant amount of specular reflection. On the other hand, if the angle θ is 0° (i.e., if the light 100 is parallel to the surface 104), then the fluid 110 in the vessel 106 will not be exposed to any light. It has been found that an angle in the range of 30-60° (which may be approximately 45°, in one embodiment) may be advantageous for reducing the degree of specular reflection and producing more sensitive color measurements.

0056The broadband light source 94 itself may be oriented to direct the light 100 at a particular angle θ with respect to the surface 104 of the vessel 106. Alternatively, at least one transmitting optical fiber may be provided to direct at least a portion of the light 100 from the broadband light source 94 to the surface 104 of the vessel 106 at a particular angle θ. <figref idref="f0006">Fig. 11</figref> shows an optical fiber bundle 112, which includes a plurality of optical fibers. In one embodiment, the optical fiber bundle 112 is provided as a fiber bundle reflection probe of the type marketed by Thorlabs, Inc., having optical fibers with a 200 µm diameter. A cross-sectional view of the optical fiber bundle 112 is shown in <figref idref="f0008">Fig. 14</figref>, which shows seven optical fibers, with six outer optical fibers 114 and one inner optical fiber 116 positioned centrally with respect to the other optical fibers 114. In the illustrated embodiment, the outer optical fibers 114 comprise transmitting optical fibers configured to transmit light from the broadband light source 94 to the surface 104 of the vessel 106, while the central or inner optical fiber 116 comprises a receiving optical fiber configured to transmit reflected light to the optical spectrometer 96. It should be understood that the illustrated configuration of the optical fiber bundle 112 is merely exemplary and that other configurations may also be employed if an optical fiber bundle is provided. For example, in other embodiments, there may be only a single transmitting optical fiber, a plurality of receiving optical fibers, and/or optical fibers differently arranged than as shown in <figref idref="f0008">Fig. 14</figref>.

0057The light 100 strikes the surface 104 of the vessel 106 and the portion 108 not reflected is transmitted through the surface 104 and into the vessel 106 at an angle according to Snell's Law. The portion 108 of light that enters the fluid 110 is absorbed and scattered based on the unique optical properties of the fluid 110, with a portion 118 of the transmitted light 108 being reflected back out of the vessel 106 (<figref idref="f0009">Fig. 15</figref>) for receipt by the optical spectrometer 96. If a receiving optical fiber 116 is provided, at least a portion of the reflected light 118 is directed to the optical spectrometer 96 by the receiving optical fiber 116.

0058The optical spectrometer 96 is configured for measurement and wavelength differentiation of at least a portion of the reflected light that it receives. In one embodiment, the optical spectrometer 96 is provided as a compact CCD spectrometer capable of measuring the intensity of light at each wavelength in the range of 200 nm - 1000 nm of the type marketed by Thorlabs, Inc., but it may also be differently configured without departing from the scope of the present disclosure.

0059The optical spectrometer 96 analyzes at least a portion of the received light and differentiates the wavelengths contained within the light to produce an optical spectrum of the light, as shown in <figref idref="f0009">Figs. 16</figref> and <figref idref="f0010">17</figref>. <figref idref="f0009">Figs. 16</figref> and <figref idref="f0010">17</figref> show the intensity of the light at different wavelengths for a fluid having a hematocrit of 8.5% and for a fluid having a free hemoglobin concentration of 400 mg/dL, respectively. In each case, the greatest intensities are displayed for wavelengths above 600 nm, indicating that the fluids are some shade of red in color. The main wavelength is then determined from the optical spectrum, such as by using a conventional color specification system, which may be software of the type marketed by Thorlabs, Inc.

0060The controller 98 then correlates the main wavelength to a corresponding hematocrit or free hemoglobin concentration. The controller 98 may be variously configured without departing from the scope of the present disclosure. In one embodiment, the controller 98 may include a microprocessor (which, in fact may include multiple physical and/or virtual processors). According to other embodiments, the controller 98 may include one or more electrical circuits designed to carry out the actions described herein. In fact, the controller 98 may include a microprocessor and other circuits or circuitry. In addition, the controller 98 may include one or more memories. The instructions by which the microprocessor is programmed may be stored on the memory associated with the microprocessor, which memory/memories may include one or more tangible non-transitory computer readable memories, having computer executable instructions stored thereon, which when executed by the microprocessor, may cause the microprocessor to carry out one or more actions as described below.

0061<figref idref="f0010">Fig. 18</figref> shows an experimentally determined correlation between main wavelength and hematocrit in a range between 0% and 60%, while <figref idref="f0011">Fig. 19</figref> more particularly shows an experimentally determined correlation between main wavelength and hematocrit in a range between 0% and 9.5%. <figref idref="f0011">Fig. 20</figref> shows an experimentally determined correlation between main wavelength and free hemoglobin concentration in a range between 0 mg/dL and 400 mg/dL. The correlations shown in <figref idref="f0010 f0011">Figs. 18-20</figref> may be generated by determining the main wavelength of a fluid having a known hematocrit (in the case of <figref idref="f0010">Figs. 18</figref> and <figref idref="f0011">19</figref>) or a known free hemoglobin concentration (in the case of <figref idref="f0011">Fig. 20</figref>). As confirmed by <figref idref="f0010 f0011">Figs. 18-20</figref>, a greater hematocrit or a higher free hemoglobin concentration results in fluid having a darker shade of red (i.e., a higher main wavelength within the visible range). The main wavelength is, thus, determined by the particular hematocrit or free hemoglobin concentration of the subject fluid, meaning that knowledge of the main wavelength of a fluid in a vessel allows for determination of the hematocrit or free hemoglobin concentration of that fluid.

0062<figref idref="f0011">Fig. 19</figref> shows the results of testing carried out using samples derived from five different blood sources to evaluate the repeatability of the method and the impact that variation in red blood cell characteristics (e.g., mean corpuscular volume and mean corpuscular hemoglobin concentration) may have on the variation of the measurement. The results show promising repeatability from person-to-person, while also showing that a sample containing high concentrations of white blood cells (the fifth sample) does not alter the color measurement technique. <figref idref="f0011">Fig. 19</figref>, thus, confirms the correlation between main wavelength and hematocrit.

0063Whether the redness of the subject fluid is due to the presence of red blood cells or free hemoglobin is determined by the most likely cause of redness in view of a number of factors, which may include the nature of the fluid, the location of the portion or vessel being monitored with respect to the separation device, and the nature of the separation device. For example, when monitoring the plasma or supernatant outlet line of a "spinning membrane"-type separator (such as one of the type described in <patcit id="pcit0014" dnum="US9895482B"><text>U.S. Patent No. 9,895,482</text></patcit> and <patcit id="pcit0015" dnum="WO2017048673A1A"><text>PCT Patent Application Publication No. WO 2017/048673 A1</text></patcit>), it is expected that the fluid will be free of cellular blood components (including red blood cells), such that any redness of the fluid will be understood to be on account of free hemoglobin. Conversely, when monitoring the low density outlet of a centrifuge (e.g., the tube 92, as in <figref idref="f0006">Fig. 11</figref>), the incidence of contamination by red blood cells is more common than hemolysis, such that any redness of the fluid will be understood to be on account of the presence of red blood cells.

0064When the controller 98 has correlated the main wavelength to a corresponding hematocrit or free hemoglobin concentration, it may generate an output that is indicative of that value. The output of the controller 98 may be directed to the interface command module 88 or some other module of the interface controller to control separation of the biological fluid or may be put to some other use.

0065As can be seen in <figref idref="f0010">Fig. 18</figref>, the correlation between main wavelength and hematocrit may be greater between 0% and 20% than above 20%. Accordingly, the best results may be achieved when monitoring fluid having (or intended to have) a relatively low hematocrit (e.g., plasma or other supernatant, buffy coat, MNC-containing layer, and other cellular components with a low red blood cell content) rather than a higher hematocrit (e.g., whole blood and packed red cells). However, it should be understood that the hematocrit measurement principles described herein may be employed for fluids having a relatively high hematocrit. In these cases, it may be advantageous for the fluid in the vessel to comprise a diluted fluid, which has been diluted from an undiluted or less diluted condition of interest to reduce the hematocrit (preferably to a level below 20%). The main wavelength and hematocrit of the (diluted) fluid are determined, as described above. Then, the hematocrit of the fluid of interest (i.e., the fluid in its undiluted or less diluted state) may be determined, followed by the controller 98 generating an alternative or additional output that is indicative of the hematocrit of the fluid of interest.

0066For example, to use this approach to measure the hematocrit of whole blood (having an unknown hematocrit, which is 45% in this example), a 2:1 dilution (two parts solution, such as saline, to one part whole blood) may be used to dilute the blood by a factor of three to bring the (unknown) hematocrit to a level that is within the 0-20% range (15% in this example). The controller 98 would determine the hematocrit of the diluted fluid to be 15% (based on the main wavelength of the diluted fluid), followed by the controller 98 multiplying the determined hematocrit by three (due to the known dilution factor of three) to arrive at the 45% value of the whole blood (i.e., the fluid of interest). While this approach is described with respect to a fluid having a relatively high hematocrit, it should be understood that it is equally applicable to a fluid having a relatively high free hemoglobin concentration.

0067The foregoing approach to measuring hematocrit and/or free hemoglobin concentration has several advantages. For example, as can be seen in <figref idref="f0006">Fig. 11</figref>, the broadband light source 94 and the optical spectrometer 96 (i.e., the light detector) are positioned on the same side of the vessel, rather than requiring access to opposing sides of the vessel, which makes it more readily used in combination with any portion or vessel of a fluid flow circuit 12 (or any other fluid-containing vessel). Additionally, this approach is not sensitive to the presence of air bubbles in the fluid. Furthermore, if the hematocrit of the MNC-containing layer exiting the separation chamber 22 is known (by using the colorimetric optical sensor device 72 to monitor an appropriate vessel, as in the embodiment of <figref idref="f0006">Fig. 11</figref>), it is more practicable to replace the above-described batch collection of MNCs with a continuous collection approach because collection efficiency and MNC product purity may be improved by continuous monitoring and procedure modification (e.g., changing the rate of operation of a pump 90 in response to an output from the controller 98).

D. Fluid Flow Circuit

0068<figref idref="f0007">Fig. 12</figref> shows an exemplary fluid flow circuit 12 that may be used in carrying out the hematocrit and/or free hemoglobin concentration measurement techniques described herein. The illustrated fluid flow circuit 12 has a "two needle" configuration, which includes a pair of fluid source access devices 120 and 122 (e.g., phlebotomy needles) configured for direct connection to a fluid source. The fluid source access devices 120 and 122 are connected by tubing 124 and 126 (referred to herein as a draw line and a return line, respectively) to a first or left cassette 128a. One of the fluid source access devices 120 is used to draw fluid (e.g., blood in an MNC collection procedure) from the fluid source into the fluid flow circuit 12 and is connected to the left cassette 128a through a y-connector 130. The other leg of the y-connector 130 is connected to tubing 132 which leads to a second or middle cassette 128b. The tubing 132 is connected, through the middle cassette 128b, to additional tubing 134, which includes a container access device 136 (e.g., a sharpened cannula or spike connector) for accessing the interior of a container, which may be an anticoagulant container in the case of a blood treatment operation. During a blood treatment operation (e.g., an MNC collection procedure), anticoagulant from the anticoagulant container is added to the blood from the fluid source at the y-connector 130 prior to entering the left cassette 128a.

0069The other fluid source access device 122 is used to deliver or return the original drawn fluid, a component of that fluid, and/or some other fluid to the fluid source (or to some other fluid recipient) and is also connected to the left cassette 128a through a y-connector 138. The other leg of the y-connector 138 is connected to tubing 140 in fluid communication at its other end with a container access device 142. Although not illustrated, the container access device 142 may be associated with a container having an amount of fluid (e.g., saline) to be used to prime the fluid flow circuit 12 and/or delivered to the fluid source (or some other fluid recipient) via the fluid source access device 122.

0070The left cassette 128a is also connected to tubing 144 in fluid communication with the separation chamber 22, which separates the fluid into its constituent parts and returns the fluid components to the fluid flow circuit 12, as described above. One of the fluid components (which may be separated red blood cells in an MNC collection procedure) is conveyed to the middle cassette 128b from the separation chamber 22 via tubing 146, while another separated component (which may be a plasma constituent in an MNC collection procedure) is conveyed to a third or right cassette 128c of the fluid flow circuit 12 from the separation chamber 22 via tubing 94. The first separated component (e.g., red blood cells) may be pumped to the left cassette 128a via tubing 148, where it is returned to the fluid source (or to some other fluid recipient), or may instead exit the middle cassette 128b via tubing 150 to a collection container 152 (referred to as a red blood cell collection container, in the context of a blood separation procedure) for storage or later use or may be recirculated from the middle cassette 128b through the separation chamber 22, as described above. The second separated component (e.g., the plasma constituent) may be pumped back to the left cassette 128a via tubing 154 for return to the fluid source (or to some other fluid recipient) and/or it may be pumped into a collection container 156 (referred to as a plasma collection container, in the context of a blood separation procedure) via different tubing 158 or recirculated from the right cassette 128c through the separation chamber 22, as described above. The destination of the various fluids passing through the cassettes depends upon the actuation of the various valves of the cassettes 128, as described in greater detail in <patcit id="pcit0016" dnum="US5462416A"><text>U.S. Patent No. 5,462,416</text></patcit>.

0071Each illustrated cassette 128 includes an injection-molded body that is compartmentalized by an interior wall to present or form a topside (which faces away from the separation assembly 10, during use) and an underside (which faces toward the separation assembly 10, during use). A flexible diaphragm overlies and peripherally seals the underside of each cassette 128, while a generally rigid upper panel overlies the topside of each cassette 128 and is sealed peripherally and to raised, channel-defining walls in the cassette 128.

0072The top- and undersides of the cassettes 128 contain preformed cavities. On the underside of the cassettes 128, the cavities form an array of valve stations and an array of pressure sensing stations. On the topside of the cassettes 128, the cavities form an array of channels or paths for conveying fluids. The valve stations communicate with the flow paths through the interior wall to interconnect them in a predetermined manner. The sensing stations also communicate with the flow paths through the interior wall to sense pressures in selected regions. The number and arrangement of the flow paths, the valve stations, and the sensing stations can vary without departing from the scope of the present disclosure.

0073In the illustrated embodiment, ten pre-molded tube connectors extend out along opposite side edges of each cassette 128. The tube connectors are arranged five on one side edge and five on the other side edge. The other side edges of the cassettes 128, as illustrated, are free of tube connectors. The tube connectors are associated with external tubing to associate the cassettes 128 with the remainder of the fluid flow circuit 12 (e.g., to a plasma collection container 156, an MNC collection container 160, or a red blood cell collection container 152) or to define tubing loops 162 that interact with pumps 90 of the separation assembly 10 to convey fluid through the fluid flow circuit 12, as described in greater detail in <patcit id="pcit0017" dnum="US5462416A"><text>U.S. Patent No. 5,462,416</text></patcit>.

0074The tube connectors communicate with various interior flow paths, which constitute the flow paths of the cassettes 128 through which a fluid enters or exits the cassette 128. The remaining interior flow paths of the cassette 128 constitute branch paths that link the flow paths associated with the tube connectors to each other through the valve stations and sensing stations. The particular configuration of one suitable cassette is described in greater detail in <patcit id="pcit0018" dnum="US5462416A"><text>U.S. Patent No. 5,462,416</text></patcit>.

0075The fluid flow circuit 12 may also include a number of other components, including clamps or valves, an air detector 164, and a drip chamber 166 that fluid passes through before entering the separation chamber 22.

0076As described above, the colorimetric optical sensor device 72 may be oriented to monitor fluid in any optically appropriate portion or vessel of the fluid flow circuit 12 (i.e., any portion or vessel in which fluid may be present and which is configured to allow for the passage of broadband light). This may include one of the tubes or conduits through which fluid flows, one of the cassettes, one of the containers, and the separation chamber 22. Additionally, the separation assembly 10 may include a plurality of colorimetric optical sensor devices 72, with each one being configured to be associated with a different portion or vessel of the fluid flow circuit 12. Finally, it should be understood that the hematocrit and free hemoglobin concentration measurement techniques described herein are not limited to monitoring of any particularly configured extracorporeal biological fluid flow circuit, but may be applied to any fluid flow circuit having an optically appropriate portion or vessel or to any other optically appropriate fluid-containing vessel.

Aspects

0077<ul id="ul0002" list-style="none" compact="compact"><li>Aspect 1. A method of measuring a hematocrit or a free hemoglobin concentration of a fluid, comprising: providing a fluid in a vessel; exposing the fluid in the vessel to a light emitted by a broadband light source so as to cause at least a portion of the light to be reflected by the fluid; receiving at least a portion of the reflected light; analyzing at least a portion of the received light to determine a main wavelength of said at least a portion of the received light; correlating the main wavelength to a hematocrit or a free hemoglobin concentration; and generating an output indicative of the hematocrit or the free hemoglobin concentration corresponding to said main wavelength.</li><li>Aspect 2. The method of Aspect 1, wherein the light from the broadband light source includes at least all wavelengths in the visible range.</li><li>Aspect 3. The method of any one of the preceding Aspects, wherein the light emitted by the broadband light source is transmitted through a surface of the vessel to be exposed to the fluid in the vessel, and the light emitted by the broadband light source is configured to strike the surface of the vessel at an angle.</li><li>Aspect 4. The method of Aspect 3, wherein the angle is between 30° and 60°.</li><li>Aspect 5. The method of Aspect 3, wherein the angle is approximately 45°.</li><li>Aspect 6. The method of any one of the preceding Aspects, wherein the fluid is in motion within the vessel when exposed to the light emitted by the broadband light source.</li><li>Aspect 7. The method of any one of Aspects 1-5, wherein the fluid is substantially stationary within the vessel when exposed to the light emitted by the broadband light source.</li><li>Aspect 8. The method of any one of the preceding Aspects, wherein the light emitted by the broadband light source is transmitted through a transmitting optical fiber before being exposed to the fluid in the vessel, and/or said at least a portion of the reflected light is transmitted through a receiving optical fiber before being analyzed.</li><li>Aspect 9. The method of any one of the preceding Aspects, wherein the light emitted by the broadband light source is transmitted through a plurality of transmitting optical fibers before being exposed to the fluid in the vessel, said at least a portion of the reflected light is transmitted through a receiving optical fiber before being analyzed, and the receiving optical fiber is centrally located with respect to said plurality of transmitting optical fibers.</li><li>Aspect 10. The method of any one of the preceding Aspects, wherein said analyzing said at least a portion of the received light includes producing an optical spectrum of said at least a portion of the received light to determine an intensity of different wavelengths in the visible range of said at least a portion of the received light, and determining the main wavelength based at least in part on said optical spectrum.</li><li>Aspect 11. The method of any one of the preceding Aspects, wherein said correlating the main wavelength to a hematocrit or a free hemoglobin concentration includes correlating the main wavelength to a hematocrit between 0% and 20%.</li><li>Aspect 12. The method of any one of the preceding Aspects, further comprising diluting an undiluted or less diluted fluid to a degree so as to form said fluid prior to the fluid being exposed to the light emitted by the broadband light source in the vessel, determining the hematocrit or the free hemoglobin concentration of the undiluted or less diluted fluid based at least in part on the main wavelength and the degree to which the undiluted or less diluted fluid was diluted, and generating a second output indicative of the hematocrit or the free hemoglobin concentration of the undiluted or less diluted fluid.</li><li>Aspect 13. A colorimetric optical sensor device configured for use in combination with a fluid-containing vessel, the colorimetric optical sensor device comprising: a broadband light source configured to emit a light, with at least a portion of the light being exposed to a fluid in the vessel and reflected; an optical spectrometer configured to receive at least a portion of the reflected light and analyze at least a portion of the received light to determine a main wavelength of said at least a portion of the received light; and a controller configured to correlate the main wavelength to a hematocrit or a free hemoglobin concentration and generate an output indicative of the hematocrit or the free hemoglobin concentration corresponding to said main wavelength.</li><li>Aspect 14. The colorimetric optical sensor device of Aspect 13, wherein the broadband light source is configured to emit light including at least all wavelengths in the visible range.</li><li>Aspect 15. The colorimetric optical sensor device of any one of Aspects 13-14, wherein the light emitted by the broadband light source is configured to be transmitted through a surface of the vessel to be exposed to the fluid in the vessel, and the light emitted by the broadband light source is configured to strike the surface of the vessel at an angle.</li><li>Aspect 16. The colorimetric optical sensor device of Aspect 15, wherein the angle is between 30° and 60°.</li><li>Aspect 17. The colorimetric optical sensor device of Aspect 15, wherein the angle is approximately 45°.</li><li>Aspect 18. The colorimetric optical sensor device of any one of Aspects 13-17, wherein colorimetric optical sensor device is associable with a vessel in which the fluid contained therein is in motion.</li><li>Aspect 19. The colorimetric optical sensor device of any one of Aspects 13-17, wherein colorimetric optical sensor device is associable with a vessel in which the fluid contained therein is substantially stationary.</li><li>Aspect 20. The colorimetric optical sensor device of any one of Aspects 13-19, further comprising a transmitting optical fiber through which the light emitted by the broadband light source is transmitted before being exposed to the fluid in the vessel.</li><li>Aspect 21. The colorimetric optical sensor device of any one of Aspects 13-20, further comprising a receiving optical fiber through which said at least a portion of the reflected light is transmitted before being received by the optical spectrometer.</li><li>Aspect 22. The colorimetric optical sensor device of any one of Aspects 13-21, further comprising an optical fiber bundle including a plurality of transmitting optical fibers through which the light emitted by the broadband light source is transmitted before being exposed to the fluid in the vessel, and a receiving optical fiber through which said at least a portion of the reflected light is transmitted before being received by the optical spectrometer, wherein the receiving optical fiber is centrally located with respect to said plurality of transmitting optical fibers.</li><li>Aspect 23. The colorimetric optical sensor device of any one of Aspects 13-22, wherein the optical spectrometer is configured to produce an optical spectrum of said at least a portion of the received light to determine an intensity of different wavelengths in the visible range of said at least a portion of the received light, and determine the main wavelength based at least in part on said optical spectrum.</li><li>Aspect 24. The colorimetric optical sensor device of any one of Aspects 13-23, wherein the controller is configured to correlate the main wavelength to a hematocrit between 0% and 20%.</li><li>Aspect 25. The colorimetric optical sensor device of any one of Aspects 13-24, wherein the fluid comprises an undiluted or less diluted fluid that has been diluted to a degree so as to form said fluid prior to the fluid being exposed to the light emitted by the broadband light source in the vessel, the controller is configured to determine the hematocrit or the free hemoglobin concentration of the undiluted or less diluted fluid based at least in part on the main wavelength and the degree to which the undiluted or less diluted fluid was diluted, and the controller is configured to generate a second output indicative of the hematocrit or the free hemoglobin concentration of the undiluted or less diluted fluid.</li></ul>

0078It will be understood that the embodiments and examples described above are illustrative of some of the applications of the principles of the present subject matter. Numerous modifications may be made by those skilled in the art without departing from the spirit and scope of the claimed subject matter, including those combinations of features that are individually disclosed or claimed herein. For these reasons, the scope hereof is not limited to the above description but is as set forth in the following claims, and it is understood that claims may be directed to the features hereof, including as combinations of features that are individually disclosed or claimed herein.