Fiber optic analyte sensor with integrated in situ total pressure correction

BACKGROUND

Photoluminescent sensors or probes are a widely employed method of measuring analyte concentration, typically oxygen, within a defined space, typically an enclosed space such as the headspace of a package or container. See, for example <patcit id="pcit0001" dnum="US20090029402A"><text>United States Published Patent Applications 2009/0029402</text></patcit>, <patcit id="pcit0002" dnum="US20088242870A"><text>2008/8242870</text></patcit>, <patcit id="pcit0003" dnum="US2008215254A"><text>2008/215254</text></patcit>, <patcit id="pcit0004" dnum="US2008199360A"><text>2008/199360</text></patcit>, <patcit id="pcit0005" dnum="US2008190172A"><text>2008/190172</text></patcit>, <patcit id="pcit0006" dnum="US2008148817A"><text>2008/148817</text></patcit>, <patcit id="pcit0007" dnum="US2008146460A"><text>2008/146460</text></patcit>, <patcit id="pcit0008" dnum="US2008117418A"><text>2008/117418</text></patcit>, <patcit id="pcit0009" dnum="US20080051646A"><text>2008/0051646</text></patcit>, and <patcit id="pcit0010" dnum="US20060002822A"><text>2006/0002822</text></patcit>, and <patcit id="pcit0011" dnum="US7569395B"><text>United States Patents 7,569,395</text></patcit>, <patcit id="pcit0012" dnum="US7534615B"><text>7,534,615</text></patcit>, <patcit id="pcit0013" dnum="US7368153B"><text>7,368,153</text></patcit>, <patcit id="pcit0014" dnum="US7138270B"><text>7,138,270</text></patcit>, <patcit id="pcit0015" dnum="US6689438B"><text>6,689,438</text></patcit>, <patcit id="pcit0016" dnum="US5718842A"><text>5,718,842</text></patcit>, <patcit id="pcit0017" dnum="US4810655A"><text>4,810,655</text></patcit>, and <patcit id="pcit0018" dnum="US4476870A"><text>4,476,870</text></patcit>.

Briefly, analyte concentration within a package or container can be measured by placing an analyte-sensitive photoluminescent probe within the package or container, allowing the probe to equilibrate within the package or container, exciting the probe with radiant energy, and measuring the extent to which radiant energy emitted by the excited probe is quenched by the presence of the target analyte. Such optical sensors are available from a number of suppliers, including PreSens Precision Sensing, GmbH of Regensburg, Germany, Oxysense of Dallas, Texas, United States, and Mocon, Inc. of Minneapolis, Minnesota, United States.

In order to permit impromptu testing of a defined space, the photoluminescent probe can be provided as a coating on the distal tip of a fiber optic filament which is threaded into the lumen of a needle and protectively retained in a fixed position within the lumen by a target analyte permeable encapsulant. One example of such a fiber optic sensing needle for use in measuring the concentration of oxygen within living tissue is described in United States Patent Application Publication <patcit id="pcit0019" dnum="US20090075321A"><text>US 2009/0075321</text></patcit>, the entire disclosure of which is hereby <i>incorporated by reference.</i>

While fiber optic sensing needles, such as that described in <patcit id="pcit0020" dnum="US20090075321A"><text>US 2009/0075321</text></patcit>, are effective for impromptu measurement of analyte concentration within a defined space, they can result in inaccurate measurements when the total pressure within the defined space is significantly different than the environment surrounding the defined spaced as the fiber optic sensing needles measure analyte partial pressure - not concentration of analyte, from which a concentration of analyte is then calculated using the general equation ANALYTE % = P_ANALYTE / P_TOTAL. Hence, lack of an accurate assumption as to the total pressure P_TOTAL of the defined space can result in an inaccurately calculated analyte concentration.

Hence, a need exists for a fast response fiber optic sensing needle that can quickly and easily measure both analyte partial pressure P_ANALYTE and total pressure P_TOTAL in a defined space and thereby consistently provide a pressure correct measurement of analyte concentration (ANALYTE %).

SUMMARY OF THE INVENTION

The invention is a fiber optic analyte-sensing instrument, method of measuring analyte concentration within an enclosed space using the fiber optic analyte-sensing instrument, and method for monitoring changes in analyte concentration within an enclosed space using the fiber optic analyte-sensing instrument.

A first embodiment of the instrument is an in situ analyte-sensing fiber optic instrument that includes (i) a tube defining a lumen, (ii) an analyte-partial-pressure-sensitive photoluminescent probe located proximate a distal end of the lumen and in fluid communication with a volume external to the distal end of the tube, and (iii) at least one fiber optic filament extending axially along the length of the lumen and in optical communication with the analyte-partial-pressure-sensitive photoluminescent probe. The instrument is characterized by (A) a void volume channel extending axially along the length of the lumen between the inner surface of the tube and the outer surface of the at least one fiber optic filament, and (B) a pressure sensor in pressure communication with the fluid communicating with the analyte-partial-pressure-sensitive photoluminescent probe via the void volume channel in the lumen of the tube. The pressure sensor permits pressure compensation of analyte-concentration values calculated from analyte-partial-pressure readings taken from the analyte-partial-pressure-sensitive photoluminescent probe.

The first embodiment of the instrument preferably has a pressure sensor that generates a P_TOTAL electronic signal representative of the total-pressure of a fluid in fluid communication with the probe, and further includes (1) a detector in optical communication with the analyte-partial-pressure-sensitive photoluminescent probe via the at least one fiber optic filament for receiving radiant energy emitted by the probe and generating a P_ANALYTE electrical signal representative of the analyte-partial-pressure of a fluid in fluid communication with the probe, and (2) a microprocessor in electrical communication with the pressure sensor and the detector for receiving temporally paired P_TOTAL and P_ANALYTE electrical signals respectively, and calculating an analyte concentration from the temporally paired electrical signals based upon the algorithm ANALYTE % = P_ANALYTE / P_TOTAL, and (3) an electronic display in electrical communication with the microprocessor for displaying calculated analyte concentration values.

A second embodiment of the instrument is a handheld instrument for impromptu in situ concomitant sensing of analyte partial pressure, preferably oxygen partial pressure, and total pressure of a hermetically sealed volume that includes an integrated combination (i) a hollow shank having a proximal and distal ends with a lumen in fluid communication with a volume external to the distal end, (ii) an oxygen-partial-pressure-sensitive photoluminescent probe within the lumen proximate the distal end of the shank and in fluid communication with a volume external to the distal end of the shank, (iii) an electronics package proximate the proximal end of the shank that includes (α) a source of excitation radiant energy, (β) a photoluminescence detector, and (γ) a pressure sensor, and (iv) at least one fiber optic filament extending axially along the length of the lumen operable for (α) transmitting excitation radiant energy from the source of excitation radiant energy to the oxygen-partial-pressure-sensitive photoluminescent probe, and (β) transmitting radiant energy emitted by the oxygen-partial-pressure-sensitive photoluminescent probe to the photoluminescence detector, and configured relative to the lumen to form a void volume channel extending axially along the length of the lumen between the inner surface of the shank and the outer surface of the at least one fiber optic filament, wherein the pressure sensor is in pressure communication with the fluid communicating with the analyte-partial-pressure-sensitive photoluminescent probe via the void volume channel in the lumen of the shank.

The second embodiment of the instrument preferably has an electronics package that includes a photoluminescence detector that generates a P_ANALYTE electrical signal representative of the analyte-partial-pressure of a fluid in fluid communication with the probe, and a pressure sensor that generates a P_TOTAL electronic signal representative of the total-pressure of a fluid in fluid communication with the probe. The electronics package preferably further includes (i) a microprocessor in electrical communication with the photoluminescence detector and the pressure sensor for receiving temporally paired P_ANALYTE and P_TOTAL electrical signals respectively, and calculating an analyte concentration from the temporally paired electrical signals based upon the algorithm ANALYTE % = P_ANALYTE / P_TOTAL, and (ii) an electronic display in electrical communication with the microprocessor for displaying calculated analyte concentration values.

The method of measuring analyte concentration within a space enclosed by a structure includes the steps of: (1) obtaining an analyte-sensing fiber optic instrument according to the invention, (2) penetrating the structure with the tube of the instrument so as to place the distal end of the lumen into fluid communication with the space enclosed by the structure, whereby both the analyte-partial-pressure-sensitive photoluminescent probe and the pressure sensor on the instrument are placed into sensible communication with the enclosed space, (3) allowing the concentration of analyte in sensible communication with the photoluminescent probe to equilibrate with the analyte concentration within the enclosed space, (4) allowing the pressure in sensible communication with the pressure sensor to equilibrate with the pressure of the enclosed space, and (5) ascertaining an analyte concentration within the enclosed space by: (i) measuring the total pressure of the enclosed space with the equilibriated pressure sensor, (ii) exposing the equilibriated photoluminescent probe to excitation radiation, (iii) measuring radiation emitted by the excited photoluminescent probe, and (iv) converting the measured emission to an oxygen concentration based upon a known pressure compensated conversion algorithm that employs the value of the measured total pressure of the enclosed space.

The method for monitoring changes in analyte concentration within a space enclosed by a structure includes the steps of (1) obtaining an analyte-sensing fiber optic instrument according to the invention, (2) penetrating the structure with the hollow shank of the instrument so as to place the distal end of the lumen into fluid communication with the space enclosed by the structure, whereby both the analyte-partial-pressure-sensitive photoluminescent probe and the pressure sensor on the instrument are placed into sensible communication with the enclosed space, (3) allowing the concentration of analyte in sensible communication with the photoluminescent probe to equilibrate with the analyte concentration within the enclosed space, (4) allowing the pressure in sensible communication with the pressure sensor to equilibrate with the pressure of the enclosed space, (5) ascertaining an analyte concentration within the enclosed space over time by: (α) coincidentally and repeatedly measuring the total pressure of the enclosed space with the equilibriated pressure sensor, and the partial pressure of analyte in the enclosed spaced with the equilibriated photoluminescent probe, (β) measuring passage of time during the repeated coincidental measurements, and (γ) converting at least some of the coincidental measurements to an analyte concentration based upon a known pressure compensated conversion algorithm that employs the value of the measured total pressure of the enclosed space, and (6) reporting at least one of (α) at least two ascertained analyte concentrations and the time interval between those reported concentrations, and (β) a rate of change in analyte concentration within the enclosed space calculated from data obtained in step (5).

The following aspects are preferred embodiments of the invention. <ol id="ol0001" ol-style=""><li>1. An in situ analyte-sensing fiber optic instrument, comprising (i) a tube defining a lumen, (ii) an analyte-partial-pressure-sensitive photoluminescent probe located proximate a distal end of the lumen and in fluid communication with a volume external to the distal end of the tube, and (iii) at least one fiber optic filament extending axially along the length of the lumen and in optical communication with the analyte-partial-pressure-sensitive photoluminescent probe, characterized by: <ol id="ol0002" compact="compact" ol-style=""><li>(a) a void volume channel extending axially along the length of the lumen between the inner surface of the tube and the outer surface of the at least one fiber optic filament, and</li><li>(b) a pressure sensor in pressure communication with the fluid communicating with the analyte-partial-pressure-sensitive photoluminescent probe via the void volume channel in the lumen of the tube.</li></ol></li><li>2. The in situ analyte-sensing fiber optic instrument of aspect 1 wherein the pressure sensor generates a P_TOTAL electronic signal representative of the total-pressure of a fluid in fluid communication with the probe, and the instrument further comprises: <ol id="ol0003" compact="compact" ol-style=""><li>(a) a detector in optical communication with the analyte-partial-pressure-sensitive photoluminescent probe via the at least one fiber optic filament for receiving radiant energy emitted by the probe and generating a P_ANALYTE electrical signal representative of the analyte-partial-pressure of a fluid in fluid communication with the probe,</li><li>(b) a microprocessor in electrical communication with the pressure sensor and the detector for receiving temporally paired P_TOTAL and P_ANALYTE electrical signals respectively, and calculating an analyte concentration from the temporally paired electrical signals based upon the algorithm ANALYZE % = P_ANALYTE / P_TOTAL, and</li><li>(c) an electronic display in electrical communication with the microprocessor for displaying calculated analyte concentration values.</li></ol></li><li>3. The in situ analyte-sensing fiber optic instrument of aspect 2 further comprising a user activatable trigger operable for simultaneously generating temporally paired P_TOTAL and P_ANALYTE electrical signals each time the trigger is activated.</li><li>4. The in situ analyte-sensing fiber optic instrument of aspect 1 wherein the tube is a blunt-tipped needle with a nominal inner diameter of 1.0 to 3.5 mm.</li><li>5. The in situ analyte-sensing fiber optic instrument of aspect 1 wherein the tube is a sharp-tipped needle with a nominal inner diameter of 1.0 to 3.5 mm.</li><li>6. The in situ analyte-sensing fiber optic instrument of aspect 1 wherein the void volume channel is an amorphous channel.</li><li>7. The in situ analyte-sensing fiber optic instrument of aspect 1 wherein the pressure sensor is in fluid communication with fluid communicating with the analyte-partial-pressure-sensitive photoluminescent probe via the void volume channel in the lumen of the tube.</li><li>8. A handheld instrument for impromptu in situ concomitant sensing of oxygen partial pressure and total pressure of a hermetically sealed volume, comprising an integrated combination of at least: <ol id="ol0004" compact="compact" ol-style=""><li>(a) a hollow shank having a proximal end, a distal end and defining a lumen in fluid communication with a volume external to the distal end,</li><li>(b) an oxygen-partial-pressure-sensitive photoluminescent probe within the lumen proximate the distal end of the shank and in fluid communication with a volume external to the distal end of the shank,</li><li>(c) an electronics package proximate the proximal end of the shank, including at least: <ol id="ol0005" compact="compact" ol-style=""><li>(i) a source of excitation radiant energy,</li><li>(ii) a photoluminescence detector, and</li><li>(iii) a pressure sensor, and</li></ol></li><li>(d) at least one fiber optic filament extending axially along the length of the lumen operable for (i) transmitting excitation radiant energy from the source of excitation radiant energy to the oxygen-partial-pressure-sensitive photoluminescent probe, and (ii) transmitting radiant energy emitted by the oxygen-partial-pressure-sensitive photoluminescent probe to the photoluminescence detector, and configured relative to the lumen to form a void volume channel extending axially along the length of the lumen between the inner surface of the shank and the outer surface of the at least one fiber optic filament, wherein</li><li>(e) the pressure sensor is in pressure communication with the fluid communicating with the analyte-partial-pressure-sensitive photoluminescent probe via the void volume channel in the lumen of the shank.</li></ol></li><li>9. The handheld instrument of aspect 8 wherein (i) the photoluminescence detector generates a P_ANALYTE electrical signal representative of the analyte-partial-pressure of a fluid in fluid communication with the probe, (ii) the pressure sensor generates a P_TOTAL electronic signal representative of the total-pressure of a fluid in fluid communication with the probe, and the electronics package further comprises: <ol id="ol0006" compact="compact" ol-style=""><li>(a) a microprocessor in electrical communication with the photoluminescence detector and the pressure sensor for receiving temporally paired P_ANALYTE and P_TOTAL electrical signals respectively, and calculating an analyte concentration from the temporally paired electrical signals based upon the algorithm ANALYTE % = P_ANALYTE / P_TOTAL, and</li><li>(b) an electronic display in electrical communication with the microprocessor for displaying calculated analyte concentration values.</li></ol></li><li>10. The handheld instrument of aspect 9 further comprising a user activatable trigger operable for simultaneously generating temporally paired P_TOTAL and P_ANALYTE electrical signals each time the trigger is activated.</li><li>11. The handheld instrument of aspect 8 wherein the tube is a blunt-tipped needle with a nominal inner diameter of 1.0 to 3.5 mm.</li><li>12. The handheld instrument of aspect 8 wherein the tube is a is a sharp-tipped needle with a nominal inner diameter of 1.0 to 3.5 mm.</li><li>13. The handheld instrument of aspect 8 wherein the void volume channel is an amorphous channel.</li><li>14. The handheld instrument of aspect 8 wherein the pressure sensor is in fluid communication with fluid communicating with the analyte-partial-pressure-sensitive photoluminescent probe via the void volume channel in the lumen of the tube.</li><li>15. A method for measuring the analyte concentration within a space enclosed by a structure, comprising the steps of: <ol id="ol0007" compact="compact" ol-style=""><li>(a) obtaining an analyte-sensing fiber optic instrument according to aspect 1,</li><li>(b) penetrating the structure with the tube of the instrument so as to place the distal end of the lumen into fluid communication with the space enclosed by the structure, whereby both the analyte-partial-pressure-sensitive photoluminescent probe and the pressure sensor on the instrument are placed into sensible communication with the enclosed space,</li><li>(c) allowing the concentration of analyte in sensible communication with the photoluminescent probe to equilibrate with the analyte concentration within the enclosed space,</li><li>(d) allowing the pressure in sensible communication with the pressure sensor to equilibrate with the pressure of the enclosed space, and</li><li>(e) ascertaining an analyte concentration within the enclosed space by: (i) measuring the total pressure of the enclosed space with the equilibriated pressure sensor, (ii) exposing the equilibriated photoluminescent probe to excitation radiation, (iii) measuring radiation emitted by the excited photoluminescent probe, and (iv) converting the measured emission to an analyte concentration based upon a known pressure compensated conversion algorithm that employs the value of the measured total pressure of the enclosed space.</li></ol></li><li>16. The method of aspect 15 wherein the analyte is oxygen.</li><li>17. The method of aspect 16 wherein the space is a retention chamber of a hermetically sealed package containing an oxygen labile pharmaceutical or foodstuff.</li><li>18. A method for monitoring changes in oxygen concentration within a space enclosed by a structure, comprising the steps of: <ol id="ol0008" compact="compact" ol-style=""><li>(a) obtaining an instrument according to aspect 9,</li><li>(b) penetrating the structure with the hollow shank of the instrument so as to place the distal end of the lumen into fluid communication with the space enclosed by the structure, whereby both the oxygen-partial-pressure-sensitive photoluminescent probe and the pressure sensor on the instrument are placed into sensible communication with the enclosed space,</li><li>(c) allowing the concentration of oxygen in sensible communication with the photoluminescent probe to equilibrate with the oxygen concentration within the enclosed space,</li><li>(d) allowing the pressure in sensible communication with the pressure sensor to equilibrate with the pressure of the enclosed space,</li><li>(e) ascertaining an oxygen concentration within the enclosed space over time by: (i) coincidentally and repeatedly measuring the total pressure of the enclosed space with the equilibriated pressure sensor, and the partial pressure of oxygen in the enclosed spaced with the equilibriated photoluminescent probe, (ii) measuring passage of time during the repeated coincidental measurements, and (iii) converting at least some of the coincidental measurements to an oxygen concentration based upon a known pressure compensated conversion algorithm that employs the value of the measured total pressure of the enclosed space, and</li><li>(f) reporting at least one of (i) at least two ascertained oxygen concentrations and the time interval between those reported concentrations, and (ii) a rate of change in oxygen concentration within the enclosed space calculated from data obtained in step (e).</li></ol></li><li>19. The method of aspect 18 wherein the space is a retention chamber of a hermetically sealed package containing an oxygen labile pharmaceutical or foodstuff.</li></ol>

BRIEF DESCRIPTION OF THE DRAWINGS

<ul id="ul0001" list-style="none"><li><figref idref="f0001">Figure 1</figref> is a perspective view of one embodiment of the invention.</li><li><figref idref="f0002">Figure 2</figref> is a cross-sectional side view of the invention depicted in <figref idref="f0001">Figure 1</figref> penetrating a structure with schematic depiction of the electronic components of the instrument.</li><li><figref idref="f0003">Figure 3</figref> is an enlarged cross-sectional side view of the needle and collar components of the invention depicted in <figref idref="f0001">Figure 1</figref>.</li><li><figref idref="f0004">Figure 4</figref> is an enlarged cross-sectional side view of the distal end portion of the needle component of the invention depicted in <figref idref="f0001">Figure 1</figref>.</li></ul>

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

<i>Nomenclature</i>

<dl id="dl0001" compact="compact"><dt><b>10</b></dt><dd>Fiber Optic Analyte-Sensing Instrument</dd><dt><b>10a</b></dt><dd>Collared Needle Subassembly of Instrument</dd><dt><b>10b</b></dt><dd>Optical Block Subassembly of Instrument</dd><dt><b>10c</b></dt><dd>Handle Portion of Instrument</dd><dt><b>20</b></dt><dd>Tube or Hollow Shank (Collectively Needle)</dd><dt><b>20₁</b></dt><dd>Proximal End of Needle</dd><dt><b>20₂</b></dt><dd>Distal End of Needle</dd><dt><b>20₃</b></dt><dd>Inner Surface of Needle</dd><dt><b>28</b></dt><dd>Ports in Needle</dd><dt><b>29</b></dt><dd>Lumen of Needle</dd><dt><b>29₁</b></dt><dd>Proximal End of Lumen</dd><dt><b>29₂</b></dt><dd>Distal End of Lumen</dd><dt><b>30</b></dt><dd>Collar</dd><dt><b>40</b></dt><dd>Thread Fitting<b>41</b> Outer O-Ring</dd><dt><b>42</b></dt><dd>Inner O-Ring</dd><dt><b>50</b></dt><dd>Fiber Optic Filament</dd><dt><b>50₁</b></dt><dd>Proximal End of Fiber Optic Filament</dd><dt><b>50₂</b></dt><dd>Distal End of Fiber Optic Filament</dd><dt><b>50₄</b></dt><dd>Outer Surface of Fiber Optic Filament</dd><dt><b>60</b></dt><dd>Void Volume Channel Sealing O-Rings</dd><dt><b>68</b></dt><dd>Void Volume Channel</dd><dt><b>69</b></dt><dd>Branch Channel</dd><dt><b>70</b></dt><dd>Photoluminescent Analyte-Partial-Pressure-Sensitive Probe</dd><dt><b>80</b></dt><dd>Photoluminescence Detector</dd><dt><b>81</b></dt><dd>Source of Excitation Radiant Energy</dd><dt><b>90</b></dt><dd>Pressure Sensor</dd><dt><b>100</b></dt><dd>Microprocessor</dd><dt><b>110</b></dt><dd>Display</dd><dt><b>120</b></dt><dd>Activation Trigger</dd><dt><b>S</b></dt><dd>Structure</dd><dt><b>V</b></dt><dd>Volume Enclosed by Structure</dd></dl>

<i>Description</i>

Construction

Referring generally to <figref idref="f0001">Figure 1</figref>, the invention is a fiber optic analyte-sensing instrument <b>10</b> employing a photoluminescent analyte-partial-pressure-sensitive probe <b>70</b> located proximate the distal end <b>20₂</b> of a needle <b>20</b> having a lumen <b>29</b>, and at least one fiber optic filament <b>50</b>, preferably a single nonjacketed fiber, that extends axially along the length of the lumen <b>29</b>. The instrument <b>10</b> is characterized by a void volume channel <b>68</b> that extends along the length of the lumen <b>29</b> between the inner surface <b>20₃</b> of the needle <b>20</b> and the outer surface <b>50₄</b> of the at least one fiber optic filament <b>50</b>, and a pressure sensor <b>90</b> in pressure communication with the same fluid communicating with the photoluminescent analyte-partial-pressure-sensitive probe <b>70</b> via the void volume channel <b>68</b>. The pressure sensor <b>90</b> permits pressure compensation of analyte-concentration values calculated from analyte-partial-pressure readings taken from the photoluminescent analyte-partial-pressure-sensitive probe <b>70</b>.

The instrument <b>10</b> is capable of measuring a variety of analytes including oxygen (O₂) and carbon dioxide (CO₂), with oxygen of most widespread interest.

Referring generally to <figref idref="f0002">Figures 2</figref>, <figref idref="f0003">3</figref> and <figref idref="f0004">4</figref> the needle <b>20</b> has a longitudinal lumen <b>29</b> with at least one port <b>28</b> proximate the distal tip <b>20₂</b> of the needle <b>20</b>. The port <b>28</b> is preferably a lateral side port <b>28</b> with the needle <b>20</b> preferably having at least two diametrically opposed lateral side ports <b>28</b>. The needle <b>20</b> can be a sharp tipped or blunt tipped needle <b>20</b> and preferably has a nominal inner diameter (<i>i.e.</i>, lumen <b>29</b>) of between 1.0 to 3.5 mm.

The proximal end <b>20₁</b> of the needle <b>20</b> is preferably attached to a collar <b>30</b> via brazing, soldering or gluing, suitable for threadable attachment to the optical block subassembly <b>10b</b> of the instrument <b>10</b> via a thread fitting <b>40</b>.

The at least one fiber optic filament <b>50</b> extends axially along the length of the lumen <b>29</b> from a proximal end <b>50₁</b> proximate the proximal end <b>29₁</b> of the lumen <b>29</b> to a distal end <b>50₂</b> proximate the distal end <b>29₂</b> of the lumen <b>29</b> and in sensing communication with the photoluminescent analyte-partial-pressure-sensitive probe <b>70</b>. The outside diameter of the at least one fiber optic filament <b>50</b> is smaller than the inside diameter of the needle <b>20</b> so as to form a void volume channel <b>68</b> along the length of the lumen <b>29</b>. As a result of the inherent axial curvature and flexibility of typical fiber optic filaments <b>50</b>, the void volume channel <b>68</b> may be an amorphous channel. The proximal end <b>50₁</b> of the fiber optic filament <b>50</b> is preferably sealingly engaged to the inner surface <b>20₃</b> of the needle <b>20</b> or the inner surface (not separately numbered) of the bore (not separately numbered) of the collar <b>30</b> by a suitable sealing means such as a sealant (<i>e.g.</i>, epoxy) or one or more o-rings <b>60</b>, to secure the at least one fiber optic filament <b>50</b> within the lumen <b>29</b> and prevent the atmosphere located outside a structure <b>S</b> being tested from reaching and contaminating the photoluminescent analyte-sensitive probe <b>70</b> and/or the pressure sensor <b>90</b> through the annular interface between the inner surface <b>20₃</b> of the needle <b>20</b> and the outer surface <b>50₄</b> of the fiber optic filament <b>50</b>.

The photoluminescent analyte-sensitive probe <b>70</b> is located within the lumen <b>29</b> between the distal tip <b>50₂</b> of the at least one fiber optic filament <b>50</b> and the distal tip <b>20₂</b> of the needle <b>20</b>, and is in sensing fluid communication with the external environment, such as a volume <b>V</b> enclosed by a structure <b>S</b>, through the at least one port <b>28</b> in the needle <b>20</b>.

The photoluminescent analyte-partial-pressure-sensitive probe <b>70</b> can be selected from the numerous commercially available types of such probes. Generally, such probes comprise a carrier substrate coated with an analyte-sensitive photoluminescent dye, often with the analyte-sensitive photoluminescent dye embedded within an analyte-permeable polymer matrix.

When employed, the carrier substrate may be selected from any material possessing sufficient structural integrity to physically support the analyte-sensitive photoluminescent dye and capable of withstanding extended exposure to the environment into which the probe <b>70</b> is to be used (<i>e.g.</i>, high humidity, low humidity, submerged in water, submerged in an acidic solution, etc). Materials suitable for use as the carrier substrate, dependent of course upon the environment to which the probe <b>70</b> is to be exposed during normal usage, include specifically but not exclusively, cellulosics such as paper, wax paper, cardstock, cardboard, wood and wood laminates; plastics such as polyethylene, polypropylene and polyethylene terephthalate; metals such as aluminum sheets, aluminum foil, steel and tin; woven and unwoven fabrics; glass; and various combinations and composites thereof such a mylar.

The analyte-sensitive photoluminescent dye may be selected from any of the well-known analyte-sensitive photoluminescent dyes. One of routine skill in the art is capable of selecting a suitable dye based upon the intended use of the fiber optic analyte-sensing instrument <b>10</b>. For example, a nonexhaustive list of suitable oxygen-sensitive photoluminescent dyes includes specifically, but not exclusively, ruthenium(II)-bipyridyl and ruthenium(II)-diphenylphenanothroline complexes, porphyrin-ketones such as platinum(II)-octaethylporphine-ketone, platinum(II)-porphyrin such as platinum(II)-tetrakis(pentafluorophenyl)porphine, palladium(II)-porphyrin such as palladium(II)-tetrakis(pentafluorophenyl)porphine, phosphorescent metallocomplexes of tetrabenzoporphyrins, chlorins, azaporphyrins, and long-decay luminescent complexes of iridium(III) or osmium(II).

Typically, the analyte-sensitive photoluminescent dye is compounded with a suitable analyte-permeable polymer matrix. Again, one of routine skill in the art is capable of selecting a suitable analyte-permeable polymer matrix based upon the intended use of the fiber optic analyte-sensing instrument <b>10</b>. For example, a nonexhaustive list of suitable polymers for use as an oxygen-permeable polymer matrix includes specifically, but not exclusively, polystryrene, polycarbonate, polysulfone, polyvinyl chloride and some co-polymers.

Referring to <figref idref="f0003">Figure 3</figref>, the proximal end <b>50₁</b> of the at least one fiber optic filament <b>50</b> is in optical communication with a photoluminescence detector <b>80</b> for transmitting excitation radiant energy from a source of excitation radiant energy <b>81</b> to the photoluminescent analyte-partial-pressure-sensitive probe <b>70</b>, and thereafter transmitting radiant energy emitted by the excited probe <b>70</b> back to the photoluminescence detector <b>80</b> where a P_ANALYTE electrical signal, representative of the analyte-partial-pressure of a fluid in fluid communication with the probe <b>70</b> is generated. The radiant energy emitted by the excited probe <b>70</b> can be measured in terms of intensity and/or lifetime (rate of decay, phase shift or anisotropy), with measurement of lifetime generally preferred as a more accurate and reliable measurement technique when seeking to establish analyte concentration via measurement of the extent to which an analyte-sensitive photoluminescent dye has been quenched by the analyte.

Referring to <figref idref="f0003">Figure 3</figref>, the void volume channel <b>68</b> is in pressure communication with a pressure sensor <b>90</b> for communicating sample-fluid total pressure (<i>i.e.</i>, the total pressure of the fluid in sensing fluid communication with the photoluminescent analyte-partial-pressure-sensitive probe <b>70</b>) to the pressure sensor <b>90</b>, whereby the pressure sensor <b>90</b> can generate a P_TOTAL electronic signal representative of the sample-fluid total-pressure in fluid communication with the probe <b>70</b>. A diaphragm (not shown) may be interposed between the pressure sensor <b>90</b> and a sample-fluid in communication with the probe <b>70</b>, but is generally unnecessary. Hence, the pressure sensor <b>90</b> may typically be in direct fluid communication with the sample-fluid communicating with the probe <b>70</b>. Referring to <figref idref="f0003">Figure 3</figref>, in order to facilitate placement of the pressure sensor <b>90</b> at a convenient location in the handle of the instrument <b>10</b>, a branch channel <b>69</b> may be provided to fluidly connect a remotely located pressure sensor <b>90</b> with the void volume channel <b>68</b>.

A user actuated trigger <b>120</b> is provided for initiating the taking of temporally paired readings of P_TOTAL and P_ANALYTE by the pressure sensor <b>90</b> and the photoluminescence detector <b>80</b>, respectively. The P_TOTAL and P_ANALYTE readings may be taken in serial or parallel fashion, but are preferably taken simultaneously.

Temporally paired readings of P_total and P_ANALYTE are transmitted from the pressure sensor <b>90</b> and the photoluminescence detector <b>80</b>, respectively, to a microprocessor <b>100</b> programmed to calculate an analyte concentration (A_NALYTE %) from these temporally paired electrical signals based at least in part upon the algorithm ANALYTE % = P_ANALYTE / P_TOTAL, and display the calculated analyte concentration on an electronic display <b>110</b>. The microprocessor <b>100</b> and display <b>110</b> may be located remotely from the instrument <b>10</b> and wired or wirelessly communicate with the pressure sensor <b>90</b> and the photoluminescence detector <b>80</b>, but are preferably integrated into the handle of the instrument <b>10</b>.

<u>Manufacture</u>

The fiber optic analyte-sensing needle <b>10</b> can be assembled by (a) affixing the needle <b>20</b> to the collar <b>30</b>, such as by brazing, (b) inserting the probe <b>70</b> into the lumen <b>29</b> of the needle <b>20</b> from the open proximal end <b>29₁</b> of the lumen <b>29</b> and tamping the probe <b>70</b> into the lumen <b>29</b> until it is positioned proximate the distal tip <b>20₂</b> of the needle <b>20</b>, (c) threading the at least one fiber optic filament <b>50</b> into the lumen <b>29</b> of the needle <b>20</b> from the open proximal end <b>29₁</b> of the lumen <b>29</b> until the distal tip <b>50₂</b> of the at least one fiber optic filament <b>50</b> is positioned proximate the probe <b>70</b> at the distal tip <b>20₂</b> of the needle <b>20</b>, (d) sliding the void volume channel sealing o-ring(s) <b>60</b> onto the proximal end <b>50₁</b> of the at least one fiber optic filament <b>50</b> projecting from the bore (not separately numbered) of the collar <b>30</b> and into seated arrangement into the annular interface between the inner surface (not separately numbered) of the collar <b>30</b> and the outer surface <b>50₄</b> of the fiber optic filament <b>50</b> to form a collared needle subassembly <b>10a</b>, (e) sealing securing the proximal end of the collared needle subassembly <b>10a</b> to an optical block housing the photoluminescence detector <b>80</b> and source of excitation radiant energy <b>81</b> employing a thread fitting <b>40</b> and inner and outer o-rings <b>41</b> and <b>42</b> respectively, to form an optical block subassembly <b>10b</b>, and (f) attaching the optical block subassembly <b>10b</b> to the balance of the electronics housed within a handle subassembly <b>10c</b> with the pressure sensor <b>90</b> in the handle subassembly <b>10c</b> in sealed pressure communication with the void volume channel <b>68</b> in the optical block subassembly <b>10b</b> and the microprocessor <b>100</b> in the handle subassembly <b>10c</b> in electrical communication with the photoluminescence detector <b>80</b> in the optical block subassembly <b>10b</b>.

<u>Use</u>

The fiber optic analyte-sensing instrument <b>10</b> can be used to quickly, easily, accurately and reliably measure analyte concentration within a defined space, typically an enclosed volume <b>V</b>, even though the enclosed volume <b>V</b> may have a total pressure (P_TOTAL) which differs substantially from surrounding atmospheric pressure. Briefly, the fiber optic analyte-sensing instrument <b>10</b> can be used to measure analyte concentration within a defined volume <b>V</b> by (A) placing the distal end portion <b>20₂</b> of the needle <b>20</b> into fluid communication with a defined space to be tested, such as by placing the distal end portion <b>20₂</b> of the needle <b>20</b> into fluid communication with the volume <b>V</b> of a hermetically sealed package <b>S</b> so as to place the distal end <b>29₂</b> of the lumen <b>29</b> into fluid communication with the volume <b>V</b> enclosed by the package <b>S</b>, whereby both the analyte-partial-pressure-sensitive photoluminescent probe <b>70</b> and the pressure sensor <b>90</b> on the instrument <b>10</b> are placed into sensible communication with the enclosed volume <b>V</b>, (B) allowing the concentration of analyte in sensible communication with the photoluminescent probe <b>70</b> to equilibrate with the analyte concentration within the enclosed volume <b>V</b>, (C) allowing the pressure in sensible communication with the pressure sensor <b>90</b> to equilibrate with the pressure of the enclosed volume <b>V</b>, and (D) ascertaining an analyte concentration within the enclosed volume <b>V</b> by: (i) measuring the total pressure of the enclosed volume <b>V</b> with the equilibriated pressure sensor <b>90</b>, (ii) exposing the equilibriated photoluminescent probe <b>70</b> to excitation radiation, (iii) measuring radiation emitted by the excited photoluminescent probe <b>70</b>, and (iv) converting the measured emission to an analyte concentration based upon a known pressure compensated conversion algorithm that employs the value of the measured total pressure (P_TOTAL) of the enclosed volume <b>V</b> to pressure correct the converted measured emission.

The fiber optic analyte-sensing instrument <b>10</b> can also be used to quickly, easily, accurately and reliably monitoring changes in analyte concentration within a defined space, typically an enclosed volume <b>V</b>, even though the enclosed volume <b>V</b> may have a total pressure (P_TOTAL) which differs substantially from surrounding atmospheric pressure. Briefly, the fiber optic analyte-sensing instrument <b>10</b> can be used to monitoring changes in analyte concentration within a defined volume <b>V</b> by (A) placing the distal end portion <b>20₂</b> of the needle <b>20</b> into fluid communication with a defined space to be tested, such as by placing the distal end portion <b>20₂</b> of the needle <b>20</b> into fluid communication with the volume <b>V</b> of a hermetically sealed package <b>S</b> so as to place the distal end <b>29₂</b> of the lumen <b>29</b> into fluid communication with the volume <b>V</b> enclosed by the package <b>S</b>, whereby both the analyte-partial-pressure-sensitive photoluminescent probe <b>70</b> and the pressure sensor <b>90</b> on the instrument <b>10</b> are placed into sensible communication with the enclosed volume <b>V</b>, (B) allowing the concentration of analyte in sensible communication with the photoluminescent probe <b>70</b> to equilibrate with the analyte concentration within the enclosed volume <b>V</b>, (C) allowing the pressure in sensible communication with the pressure sensor <b>90</b> to equilibrate with the pressure of the enclosed volume <b>V</b>, and (D) ascertaining an analyte concentration within the enclosed volume <b>V</b> by: (α) coincidentally and repeatedly measuring the total pressure (P_TOTAL) of the enclosed volume <b>V</b> with the equilibriated pressure sensor <b>90</b>, and the partial pressure of analyte (P_ANALYTE) in the enclosed volume <b>V</b> with the equilibriated photoluminescent probe <b>70</b>, (β) measuring passage of time (At) during the repeated coincidental measurements, and (γ) converting at least some of the coincidental measurements to an analyte concentration (A_NALYTE %) based upon a known pressure compensated conversion algorithm that employs the value of the measured total pressure (P_TOTAL) of the enclosed volume <b>V</b>, and (E) reporting at least one of (α) at least two ascertained analyte concentrations (A_NALYTE %) and the time interval (Δt) between those reported concentrations, and (β) a rate of change in analyte concentration within the enclosed volume <b>V</b> calculated from data obtained in step (D).