A drug delivery and monitoring system for a ventilator

FIELD OF THE INVENTION

This invention relates to ventilators and to drug delivery systems.

BACKGROUND OF THE INVENTION

Mechanical ventilation is a method of mechanically assisting or replacing spontaneous breathing when patients cannot do so. One type of ventilation system employs the use of an endotracheal or tracheostomy tube secured into a patient's upper respiratory tract. Gas is mechanically delivered to the patient via the tube. In many cases, mechanical ventilation is used in acute settings such as an intensive care unit for a short period of time during a serious illness. Currently, the main form of mechanical ventilation is positive pressure ventilation, which works by increasing the pressure in the patient's airway and thus forcing additional air into the lungs. To aid in the treatment of ventilated patients, aerosol medicines are aspirated in situ through an access point in the ventilator system. This process is manual, requiring the medical professional to deliver the aerosols on a regular basis.

Bronchodilator and corticosteroid medications for the treatment of reversible airway obstruction are often delivered via inhalation to the lower respiratory tract in both spontaneously breathing and mechanically ventilated patients. The devices typically used for delivery of aerosols to ventilated patients are small-volume nebulizers and pressurized metered-dose inhalers. Small-volume nebulizers and metered-dose inhalers can effectively deliver aerosols in a ventilator model and aerosol delivery can be significantly improved when a proper technique of administration is followed. To enhance lung deposition of aerosols from metered-dose inhalers, several accessory devices have been developed.

The accessory devices most commonly used to deliver aerosols from metered-dose inhalers into ventilator circuits are inline non-chamber devices and inline holding chambers. The advantage of a holding chamber inserted in the ventilator circuit is that the actuated aerosol cloud is retained within the chamber and hence impaction of the drug within the ventilator circuit is reduced.

Goals of this invention include reducing healthcare costs and improving patient safety by automatically administering medication to mechanically ventilated patients. The document <patcit id="pcit0001" dnum="GB2055046A"><text>GB2055 046A</text></patcit> discloses apparatus for determining hypersensitivity of the respiratory system. The document does not disclose a flow sensor in communication with an actuator for actuating a medicine container. The document <patcit id="pcit0002" dnum="WO9831413A"><text>WO 98/31413 A</text></patcit> discloses an apparatus for delivering airborne substances, in which no net airflow is created. The document <patcit id="pcit0003" dnum="US4558710B"><text>US 4558710 B</text></patcit> discloses apparatus for testing the airways of a patient.

SUMMARY OF THE INVENTION

The invention provides a drug delivery and monitoring system for a ventilator according to claim 1.

An automated drug delivery and monitoring system for use on mechanically ventilated patients in the intensive care unit is presented. Medication in the form of respirable particles is transported through ventilator circuitry by a delivery unit. Multiple medications may be delivered into the gas flow of the ventilator, with each medication delivered in a defined dose for a frequency and interval as specified by an operator. The particles mixed into the gas flow of the ventilator are inhaled and ingested by the patient's lungs.

The device combines monitoring and automated administration to facilitate control of drug delivery. The dispensed medications are preferred to be government approved and accepted as standard of care.

DESCRIPTION OF THE DRAWINGS

<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001"><b>Figure 1</b></figref> is a schematic view showing a control unit <b>2</b> connected to a delivery unit <b>4.</b></li><li><figref idref="f0001"><b>Figure 2</b></figref> is a perspective view of the delivery unit.</li><li><figref idref="f0002"><b>Figure 3</b></figref> is a top plan view of the delivery unit.</li><li><figref idref="f0002"><b>Figure 4</b></figref> is a sectioned view taken essentially along line A-A of <figref idref="f0002"><b>Figure 3</b></figref><b>.</b></li><li><figref idref="f0003"><b>Figure 5</b></figref> is a perspective view isolating an index table of a delivery unit and showing metered dose inhalers in position on the index table.</li><li><figref idref="f0003"><b>Figure 6</b></figref> illustrates an example of a control unit display.</li><li><figref idref="f0005"><b>Figure 8</b></figref> is a schematic illustrating control functions of an example</li><li><figref idref="f0004"><b>Figure 7</b></figref> is a schematic of an example.</li></ul>

DESCRIPTION OF PREFERRED EMBODIMENTS

In one example, an automatic drug delivery device for mechanical ventilator tubing circuitry is disclosed. Metered dose inhalers may be used to deliver drugs into the mechanical ventilator tubing circuitry. The metered dose inhalers may be aerosols. A control unit, which may incorporate a microprocessor, delivers the drugs or other therapeutic agents at a specified time, frequency, dose, and flow triggered to maintain a monitored and consistent delivery of medicaments into the air stream. The device may provide multiple ports to hold and dispense aerosols, which may be in the form of metered dose inhalers. Indicators on an operator interface panel may display delivery and status information, and provide configuration capability to the operator. Patient identification, date, time, medication type, and dose may be logged by the system and can be used for dosage reporting. "Drug" and "medicine" as used herein can mean a drug, medicine, medicament or therapeutic agent dispensed by the device for patient inhalation as delivered through the ventilator circuit.

In one embodiment a control unit <b>2</b> communicates with a delivery unit <b>4.</b><figref idref="f0001"><b>Figure 1</b></figref><b>.</b> These components may be linked via a cable <b>6</b> carrying both serial communications and power between them. Power may be provided to the operator interface panel via a medical grade AC to DC power supply. A battery system, such as an uninterruptable power source, allows the device to function during times of AC power interruption. The delivery unit, and the point of medication, is preferred to be positioned relatively near the patient, while the control unit may be positioned further away from the patient, which is facilitated by cable <b>6.</b> The lower voltage DC current of the preferred control unit allows it to be hand held.

The control unit <b>2</b> may contain an operator interface panel. The control unit may comprise a microprocessor. The operator interface panel will typically provide for operator input, and will provide output to the delivery unit <b>4,</b> and it may provide data output. The control unit may be separated from the delivery unit by a power/control cable <b>6.</b> This configuration facilitates access to the programming features of the system and reduces the size and weight of the section that needs to be in close proximity to the patient and ventilator tubing.

The delivery unit may directly interface with the sensing and control hardware for delivery of medicaments to the air stream. Operation of the delivery unit is under command and control of the control unit, which may be via a serial communications link. The interface provides a means of manual control, status, and data transfer from the operator interface panel.

The delivery unit may be contained in a housing. The housing <b>8</b> protects the delivery unit, and also limits access to the drugs or medicaments contained in the housing. The housing may be designed to be tamper-proof, so that it is accessible by hospital staff, such as by providing a lock <b>12.</b> The top panel <b>10</b> of the housing allows access to the internal mechanism of the delivery unit so that drugs may be replaced or replenished. In one embodiment, drugs or other therapeutic agents are delivered in an aerosol form, and the drugs or agents may be delivered by metered dose inhalers.

<figref idref="f0002"><b>Figure 4</b></figref> is a sectioned view of the delivery unit, which is cut away to show internal features of an example of the delivery unit. This example of the delivery unit includes a rotatable index table <b>14.</b> A rotation device <b>16</b> is used to rotate the index table as controlled by the control unit. The rotation device could be a motor, such as a stepper motor, or a rotary solenoid. This rotation device communicates with the index table to rotate the index table by a shaft that rides in a support bearing <b>18.</b> A coupling <b>20</b> may be used to couple the shaft <b>22</b> to the rotation device.

An agitator or shaker may be integrated into the index table. Many medications must be agitated before delivery. The control unit causes the agitator to agitate the medication just prior to delivery according to the selected interval for delivery of the particular medication.

Linear actuator <b>24</b> may be disposed above a metered dose inhaler <b>30A</b> that is rotated into position by the index table. The metered dose inhalers exemplified by <b>30A, 30C</b> are selectively rotated by the index table, as controlled by the control unit, to be in position above the conduit <b>26</b> of the mechanical ventilator tubing circuitry. The linear actuator, which may be a linear solenoid, is connected to an actuator, such as actuation jaws <b>28.</b> In the embodiment shown, the solenoid, acting through the actuation jaws, applies a downward force to the metered dose inhaler <b>30A.</b> A valve <b>42</b> of the metered dose inhaler is opened and dispenses a metered dose into the conduit of the mechanical ventilator tubing circuitry. The control unit times actuation so that the drug or agent is dispensed while the flow of gas through the conduit is toward the patient; that is, while the patient inhales.

The linear actuator may have a position sensor <b>40</b> that verifies the position of the linear actuator. This sensor verifies movement of the linear actuator to deliver a dose, and verifies return of the linear actuator after actuation. Return of the linear actuator and the actuation jaws is critical to positioning of the index table for receiving the required metered dose inhaler.

The delivery unit communicates with a conduit <b>26</b> that is part of the mechanical ventilator tubing circuitry. The conduit communicates with the index table as shown.

A plurality of metered dose inhalers is present in the delivery unit. As is shown in <figref idref="f0003"><b>Figure 5</b></figref><b>,</b> in one embodiment of the invention, four (4) metered dose inhalers engage the index table. Fewer than four metered dose inhalers may be used with the device as shown in the drawings. The device could be designed for more than four metered dose inhalers.

As shown in <figref idref="f0002"><b>Figure 4</b></figref><b>,</b> a non-metal, non-allergic deformable insert <b>32</b> is present within the index table. The insert may be formed of plastic, synthetic rubber or similar deformable materials. Not all metered dose inhalers are of identical dimensions at the valve. The insert is deformable, and allows metered dose inhalers and other similar dispensers of various sizes and configurations to be used with the device. Rubber inserts configured for a particular dispenser may be used with the index table.

In another example, a manifold is used rather than the index table. The manifold may receive a plurality of metered dose inhalers, such as four (4) metered dose inhalers. In this example, the manifold has four inlets, and a single outlet, with the single outlet communicating with the conduit of the mechanical ventilator tubing circuitry. In another example, the device could have an equal number of inlets and outlets.

In one example, four linear actuators, each with associated actuation jaws, may be used to selectively actuate the metered dose inhalers. The number of linear actuators will correspond to the number of inlets in the manifold for drug dispensing. The manifold may arrange the metered dose inhalers in an "in line" configuration, or other geometric configurations such as "V" and radial arrangements. The advantage of the index table over the manifold is believed to be that the metered dose inhaler to be actuated may be placed directly above, and in close approximation to, the conduit, leading to an efficient dispensing of the medication as opposed to a manifold, which prevents possible mixing of drugs within a manifold. The use of the insert <b>32</b> also allows the device to be cleaned by simply replacing the insert, as opposed to cleaning a manifold into which a plurality of drugs or other materials are dispensed. However, the use of a manifold means that a rotary device is not required, and operation of the device is simplified. The manifold is preferred to have an agitator or shaker for agitating the medication prior to delivery.

The delivery unit may continuously monitor the air pathway flow via a gas flow sensor <b>34.</b> A flow profile may be established that contains frequency, peak flow, peak flow timing, and duration for both inhalation and exhalation.

Dosage delivery timers are preferred to be maintained for each port. Delivery frequency information may be calculated and configured by the control unit. Dosage counters are preferred to be maintained, with this information conveyed from the delivery unit to the control unit. The dose release sensor <b>36</b> may be monitored to detect if the aerosol was delivered into the air stream.

The delivery unit is preferred to have a sensor <b>44</b> to determine if an index position presents a drug canister, such as a metered dose inhaler canister. The sensor may be part of the index table.

The delivery unit is preferred to comprise an index sensor <b>38.</b> The index sensor verifies the position of the index table and the associated drug or agent.

A gas flow sensor <b>34</b> is preferred to be used. The gas flow sensor communicates with the conduit. The gas flow sensor measures the direction of flow of gas through the conduit. The gas flow sensor may measure the pressure and/or the rate of change of pressure in the conduit, and may measure other gas flow characteristics such as volumetric gas flow rate and temperature. A primary function of the gas flow sensor is to communicate with the control unit to indicate the direction of flow of gas through the conduit. The release of the drug or agent into the conduit should be timed so that the drug or agent flows with the gas toward the patient. Upon actuation, the air pathway may be monitored by the gas flow sensor to detect the start of the mechanical ventilator gas delivery (inhale). The port may be actuated and the dosage delivered to the conduit at the optimum flow delivery point. The control unit actuates the metered dose inhaler or other device so that drug or agent is released when the flow of gas in the conduit is toward the patient.

The delivery unit signals the control unit to restart the port timer and decrements the dosage counter. The process repeats until commanded to stop or the aerosol cartridge is emptied. Indicators on the delivery unit may indicate actuation, status, alarm and exceptional conditions.

The gas flow sensor, or an additional sensor, may be used to measure pressure and/or the rate of change of pressure in the conduit, and may measure other gas flow characteristics such as volumetric gas flow rate and temperature, that indicate the patient's ability to receive the drug or agent. The gas flow sensor measures circuit conditions and patient airway resistance, which may be used to determine the need for additional medication dosing and timing or modulation of the current specified dosing and timing of the medication. Higher pressure and/or a relatively short cycle time on reversal of gas flow indicate that the ability of the patient to consume the drug or agent through the lungs is impaired. In such case, the control unit may be programmed to increase the dosage frequency to the patient. The programming may occur manually or automatically by an algorithm utilized by the control unit.

The delivery unit may comprise a dose release sensor <b>36.</b> This sensor verifies that a dose of a drug or agent was actually dispensed and delivered. Verification may be provided and recorded in a data base collection at the control unit or another computer that is in communication with the delivery unit. Similarly, data from other sensors as disclosed herein may be collected and stored in a data base at the control unit or in another computer drive or storage device.

A spectrometer may be disposed in the conduit. The spectrometer measures ultraviolet, optical and near-infrared spectra to determine particle size reflectance and deposition/detection. Raman spectroscopy and optical frequency comb spectroscopy may be incorporated. The spectrometer may be placed at the distal end of the device. The device may also analyze device/ventilator and patient effluent gases.

A dedicated industry standard serial communications interface may communicate with the delivery unit. The protocol may be ASCII text based, with sufficient checks to verify message delivery and integrity. A USB interface may provide operator updates of the medications database, and provide patient information and system logs. An Ethernet interface to the control unit may provide remote access from other computer systems for remote monitoring and configuration upload/download. <figref idref="f0004"><b>Figure 7</b></figref><b>.</b>

An operator interface panel <b>50</b> may comprise a touch screen, flat panel display that will be used to control the delivery unit, and to display system status. <figref idref="f0003"><b>Figure 6</b></figref><b>.</b> The panel and control unit may allow configuring drug dispensing, such as inputting the desired delivery time and frequency of the plurality of drugs present in the delivery unit. The control unit may maintain logs of usage, medications delivered to the patient, and a drug configuration library.

The operator interface panel may comprise visual data on the screen. A status of each delivery port of the delivery unit is provided. The information may include the number of doses remaining, time to next actuation, frequency of delivery, delivery status, and a manual actuation control.

A menu may display control and configuration selections. A configuration screen may provide controls and methods for configuring the operator interface panel or delivery unit components. The drug database screen will allow monitoring and maintenance of the drug identification, dosage and delivery frequency. The operator may amend entries into the data base. Entries in this database are for use on the main screen when selecting drugs or agents for the delivery port. A reporting screen may display statistics/logs concerning delivery of medications by the system overall and on a per-patient basis. Printing, upload/download will be options provided to the operator. Status/Service screen provides detailed status and diagnostic information about the system. Low level access may be provided through this screen.

The operator interface may comprise a computer with the following components and interfaces: 1) nonvolatile memory for both dosing schedules and dosing data logging; 2) bidirectional serial interface for communicating with the delivery unit. 3) USB interface for data transfer; 4) Ethernet interface for remote monitoring and configuration; 5) touch screen input interface; 6) a color Liquid Crystal Display (LCD) interface; 7) a battery backed real-time clock shall provide a reference for scheduled dosing events; 8) a barcode reader for patient and medication identification, with input into the control unit, hospital databases and/or medication administration records. Output to the operator may be provided by a LCD. Input from the operator may be provided by a touch screen integrated with the LCD.