Multiple lumen monitored drug delivery nasal cannula system

A multiple lumen nasal cannula that can be used to delivery two separate supplies of gases to a patient. The multiple lumen nasal cannula includes a first lumen for delivering a first gas and a second lumen for delivering a second gas. The first lumen includes support structure that reduces the tendency of the cannula to kink and lock the delivery of gas to a patient. The cannula assembly includes a mixing chamber positioned near the patient such that the two supplies of gas are not mixed until a location approximate to delivery to the patient. The nasal cannula assembly includes a connecting device that allows the two separate supplies of gas to be correctly delivered to the two different lumens of the nasal cannula.

FIELD OF THE INVENTION

The present invention relates to a medical device for providing medical gasses from at least one gas source to a patient. More specifically, the present invention relates to a multiple lumen cannula for delivering multiple medical gasses to a patient and mixing the gasses at a location proximal to the patient.

BACKGROUND OF THE INVENTION

Patients that have respiratory difficulties often must be placed on a mechanical ventilator. These difficulties may be pathological in nature or may be due to the fact that a patient is too weak or sedated to independently proper respiration functions. Often, the patient may be spontaneously attempting to breathe but not able to complete a full respiratory cycle. In these cases mechanically assisted ventilation is provided. In mechanically assisted ventilation a combination and pressure and/or flow sensors detect a patient's breath attempt. This detection triggers the delivery of a mechanical breath. This breath is provided by the delivery of a pulse or plug of medical gases under a pressure that is sufficient to overcome the resistance of the patient's airway to fill the lungs. When this pulse of medical gas is discontinued the natural compliance of the patient's chest wall forces the delivered breath out of the patient in an expiratory phase.

Mechanical ventilation can comprise the delivery of air, but often the breath that is delivered is formed of a mixture of various medical gasses. These gasses may include oxygen, helium, nitric oxide (NO), a drug aerosol, or, in the case of anesthesia delivery, an anesthetic agent. The proper combination of medical gasses would be decided upon by the clinician in response to the ailments of the patient.

Efficient mechanical ventilation requires a quality ventilator-patient interface. This requires a quality seal around the patient airway thereby providing efficient delivery of the medical gasses. There are many varieties of ventilator-patient interfaces. These varieties include face masks which cover the patient's mouth and nose, an endotracheal tube, or a nasal cannula. While there are advantages to each of the patient interfaces a nasal cannula presents the advantage of providing a higher quality connection to the patient's respiratory system than a face mask while being less invasive than an endotracheal tube.

In the delivery of some medical gasses to a patient it is desirable to keep the gasses separate until shortly before they are delivered to the patient. This may arise due to properties desired in each of the gasses, structural components of the mechanical ventilator, or because of adverse reactions between different medical gasses. One example of such adverse reactions is the reaction that takes place when oxygen is mixed with nitric oxide. Nitric oxide is a gas that, when inhaled, acts to dilate blood vessels in the lungs, improving oxygenation of the blood and reducing pulmonary hypertension. Therefore it is often desired to deliver a combination of nitric oxide to improve lung function with an increased concentration of oxygen to improve oxygen transfer. However, oxygen and nitric oxide react to form nitrogen dioxide (NO2), a toxic substance. Therefore, to reduce the production of nitric oxide it is desirable to keep the supply of oxygen and nitric oxide separate until just before it is delivered to the patient.

In many clinical or critical care situations a patient is connected to a wide variety of monitoring and/or support devices. These devices may include patient monitoring such as ECG, EMG, or EEG, fluid and/or nutritional support in the form of a catheter, patient waste removal, or respiratory support in the form of a mechanical ventilator. A challenge arises with this multitude of patient connections in keeping them tangle free and properly connected to the patient. This becomes difficult when the patient is moving, clinicians are moving about the patient, or the patient (and connected equipment) must be moved within the treatment facility. While data connections are more susceptible to disconnection from the patient gasses or fluid delivery connections are susceptible to kinks or entanglements in the lines resulting in restricted or interrupted delivery to the patient.

Therefore it is desirable in the field of mechanical ventilation to provide a kink resistant nasal cannula that can separately deliver multiple medical gasses to a location proximal to a patient.

SUMMARY OF THE INVENTION

In general, the present invention provides a kink resistant delivery means for medical gasses. A nasal cannula is provided with multiple lumens for the separate delivery of multiple medical gases. More specifically, a second lumen is disposed within a first lumen to provide for multiple medical gasses and additional structures within the cannula to provide kink resistance.

An additional aspect of the present invention comprises the monitoring of each of the medical gasses within the nasal cannula. This monitoring detects the pressure within the lumen of the medical gas being delivered to the patient. This pressure may be monitored as a differential pressure between the multiple lumens of the nasal cannula. As a further aspect of the present invention, the differential pressure measurement may be used to determine the state of the medical gas delivery to the patient via the nasal cannula. This state may include the detection of normal operation, a kink in the nasal cannula, or disconnection of the ventilator-patient interface.

In another aspect of the present invention, the patient triggering means or means for detecting a patient breath attempt may be disposed within the nasal cannula to provide more accurate detection of patient breath attempts and triggering of the delivery of pulses of medical gas to the patient.

In a still further aspect of the present invention, the multiple lumen cannula of the present invention comprises a mixing chamber disposed at one end of the cannula proximal to the patient interface. The mixing chamber provides for the mixing of medical gasses at a location proximal to the patient for delivery to the patient.

In a final aspect of the nasal cannula of the present invention, the nasal cannula comprises a connection assembly that facilitates the connection of the sources of medical gas to the multiple lumen cannula of the present invention. This connection assembly provides the low resistance delivery of the medical gasses from their source to the multiple lumens of the cannula. The connection means for each lumen of the multiple lumen cannula is morphologically different thus insuring the proper connection of the multiple lumens of the cannula.

DETAILED DESCRIPTION

Referring toFIG. 1, a ventilator system10for delivering one or more medical gasses to a patient12is shown. The ventilator system10delivers a quantity of medical gas from supply tanks14and16to a patient12via a mechanical ventilator18. The medical gases in supply tanks14and16may comprise, but are not limited to, air, oxygen, nitrogen dioxide (NO2) helium, and a drug aerosol. Within the mechanical ventilator18is a CPU20that controls the electrical and mechanical components of the mechanical ventilator18, including a first valve22and a second valve24disposed within conduits26and28respectively to control the flow of medical gas from supply tanks14and16. In an embodiment of the present invention, first valve22and second valve24may be solenoid valves but it is understood that any valve with the suitable time response to control medical gas flow may be used. First t-connector30and second t-connector32are disposed along conduits26and28respectively and provide a connection via conduits34and26respectively to differential pressure transducer38. Differential pressure transducer38relays the differential pressure information to CPU20via electrical connection40. CPU20may use this differential pressure data to control elements of the mechanical ventilator18including the ventilator engine42via electrical connection44, first valve22via electrical connection46, and second valve24via electrical connection48.

After first t-connector30and second t-connector32, the medical gasses travel via conduit50and52respectively to cannula assembly54. The cannula assembly54generally includes a connection assembly56, a cannula58, a mixing chamber60and patient interface62. The conduits50and52connect to connection assembly56of the cannula assembly54. Connection assembly56supplies the medical gas from the conduits50and52to the first and second lumens of cannula58, the details of which will be discussed below. Cannula58may be approximately two meters in length to provide adequate gas connection between the patient12and the mechanical ventilator18with a suitable range of motion and connection. The gas mixing chamber60is disposed at the end of cannula58proximal to the patient12. Within gas mixing chamber60, the first and second lumens of the cannula58provide the gaseous connection to facilitate the mixing of the two previously separate medical gasses. Gas mixing chamber60allows for the medical gasses to be delivered to patient12via patient interface means62as a homogenous mixture. Patient interface means62in the present embodiment comprises a nasal cannula, but it is understood that alternative patient interface means may be used, including a face mask or an endotracheal tube.

Referring toFIG. 2, cannula assembly54comprises connection assembly56, cannula58, and gas mixing assembly60. Medical gas is supplied to connection assembly56via conduits50and52. Conduits50and52are respectively attached to first supply port64and second supply port66of the connection assembly56. Connection assembly56is connected to cannula58via a cannula supply port68.

FIG. 3illustrates a section view of the connection assembly taken along line3-3ofFIG. 2. As illustrated inFIG. 3, the connection assembly56includes a first supply port64that receives the oxygen conduit50and the second supply port66that receives the gas conduit52. The first supply port64directs the supply of oxygen into the lumen chamber80through the passageway88. The lumen chamber80is in fluid communication with the annular supply port68, which receives the cannula58.

The second supply port66receives the therapeutic gas and directs the gas to an internal passageway83that receives an extended portion of the cannula58in a manner to be described in great detail below.

In the preferred embodiment of the invention, the connection assembly56is formed from PVC, which is appropriate for transmitting medical gases. However, other appropriate materials could be utilized while operating with the scope of the present invention.

The multiple lumen design90of a first embodiment of the present invention can be seen inFIG. 4with a first outer lumen70and disposed within it a second lumen72.FIG. 4bdepicts the first lumen70stripped away from second lumen72to facilitate proper insertion of the dual-lumen cannula90into cannula supply port68. Referring back toFIG. 3, upon insertion of cannula into cannula supply port68, the extended portion74of second lumen72extends through lumen chamber80to conduit78leading from second supply port66. The extended portion75is sealed within the passageway83, such as with a solvent bond, to provide a gaseous connection from supply tank to second lumen72.

As extended portion74extends into the passageway83, the leading edge81of the first lumen70is disposed within cannula supply port68until the leading edge81abuts the annular ring82. The first lumen70is sealingly connected to the cannula supply port68by means of an adhesive, such as a solvent bond. Annular ring82provides an additional seal between connection assembly56and cannula58while allowing for a gaseous connection between first lumen70and lumen chamber80. As can be understood inFIG. 3, the medical gas, such as oxygen, from the supply tank is supplied to the lumen chamber80by the first supply port64and the passageway88. The medical gas flows through the lumen chamber80and into the first, outer lumen70through the opening defined by the annular ring82. The second, therapeutic drug is supplied to the connection assembly56through the second supply port66and passes through the conduit78. The second gas enters the extended portion74of the second, inner lumen72such that the two separate supplies of gases can be delivered to the respective inner and outer lumens70,72.

Referring back toFIG. 2, the dual lumen cannula58provides the gaseous connection between connection assembly56and gas mixing chamber60. As depicted in the cross-section view ofFIG. 4, the cannula90may comprise a coaxial design. In the coaxial multiple lumen cannula90, kink resistance and structural support is provided by a plurality of ridges92that extend from the outer wall93of the first lumen70to the outer wall95of the second lumen72. These ridges92are preferably made of the same PVC material as the rest of the cannula58.

As can be understood inFIGS. 4aand4b, the outer lumen70includes a series of flow passageways97positioned between the series of ridges92. The flow passageways97provide an area for the gas to flow between the first lumen70and the second lumen72. The second lumen72includes a center passageway99that allows gases to flow through the second lumen72. In the first embodiment shown inFIGS. 4aand4b, the flow passageways97and center passageway99are coaxial.

In the dual-lumen cannula90depicted inFIG. 4, the cross-sectional area of the center passageway99of the second lumen72and the combined area of the series of flow passageways97contained within the outer lumen70are selected based upon the flow rate of the gases being delivered through each of the first and second lumens70,72. The flow area within each of the first and second lumens is proportional to the lumen resistance, which in turn is proportional to the gas flow through the lumen. In order to equalize the pressure differential between the first and second lumens, the flow area included in each of the lumens is selected to produce a very small pressure differential during typical gas flow rates. For example, if the gas flow rate through the center passageway99is significantly less than the flow rate through the series of flow passageways97, the flow area of the center passageway99should be small to create approximately the same back pressure as the outer lumen70. The selection of the flow areas allows a differential pressure sensor to be used to monitor the pressures within the first and second lumens70,72.

Referring now toFIG. 5, the cannula94may alternatively comprise a double lumen cannula design in which the lumens are not coaxial. The double lumen cannula94comprises a first lumen101with an outer wall103and a second lumen105with an outer wall107. However, as opposed to the coaxial multiple lumen cannula discussed previously, in the double lumen cannula94, the first lumen101and the second lumen105share a portion of their outer walls103and107, respectively, so that the first lumen101and second lumen105are in a parallel relationship along the length of the cannula94. The double lumen cannula94of the second embodiment provides the same structural and kink resistance properties as the coaxial multiple lumen cannula90. The kink resistance and structural support of the double lumen94is supplied by a thicker outer wall of the second lumen105, as well as by the plurality of ridges109that extend from the outer wall of the first lumen101towards the central axis98, as shown inFIG. 5b.

As discussed above, the flow areas contained within the first lumen101and the second lumen105are selected to create an equal back pressure for the preferred gas flow rates through both of the first and second lumens101,105. The matching pressures within the first and second lumens103,105allow a differential pressure sensor to be utilized to monitor the flow through the double lumen cannula94.

The double lumen cannula94shown inFIG. 5utilizes an alternative connection assembly100, depicted inFIG. 6, rather than the connection assembly56for use with coaxial multiple lumen cannula90. Connection assembly100is depicted inFIG. 6withFIG. 6adepicting the ventilator side102andFIG. 6bdepicting the patient side104of connection assembly100. Ventilator side102comprises a first supply port106for gaseous connection with conduit50and a second supply port108for gaseous connection with conduit52. Patient side104of connection assembly100comprises a cannula supply port110. However, because the double lumen cannula94has an asymmetrical cross section, the potential exists for misconnection of the double lumen cannula94to the cannula supply port110. Therefore, as depicted inFIG. 5b, the outer wall107of second lumen105comprises a morphologically different region112at the ventilator connection end of the double lumen cannula94. The morphologically different region112is complementary to morphologically different receptor116formed in the connection assembly100. The complementary nature of morphologically distinctive receptor116thus insures that the ventilator end of double lumen cannula94may only be connected to connection assembly100in a single, proper orientation.

Referring now toFIGS. 2 and 7, the cannula58, which inFIG. 7is depicted as coaxial multiple lumen cannula90, is inserted into ventilator end118of gas mixing assembly60. The cannula90is inserted until its outer end119abuts annular ring122, which separates the ventilator end118from the patient end120of the gas mixing assembly60. Patient end120of gas mixing assembly60includes a mixing chamber124for the mixing of the medical gasses separately supplied by first lumen70and the second lumen72. The mixing assembly60allows the gasses to remain separate until a location proximate to the patient wherein a homogenous mixture of the medical gasses may be formed just prior to delivery to the patient via a patient connection means62. InFIG. 7, the connecting means62is shown as a nasal cannula; however it is understood that alternative suitable patient connection means may also be used.

In a further aspect of the invention, a patient trigger sensor126may be disposed within mixing chamber124so that in the absence of gas flow through either of the nasal cannula lumens, a patient trigger may be detected. This provides a location proximate to the patient for the detection of a patient breath attempt, is used to trigger the delivery of a breath of medical gas from the ventilator, which would then be supplemented with a pulse of medical gas from supply tanks14and/or16. The detection of this patient trigger would be sent along connection128to CPU20to facilitate the control over the ventilator system10. Alternatively, the patient trigger sensor126may be disposed within one or both of the nasal cannulas130. In the absence of gas flow through one of the nasal cannula channels, that particular lumen is used to measure the pressure in the mixing chamber or end of the cannula. The pressure at the base of the alternate gas tube is measuring the pressure at the point of the t-connector. In a further aspect of the present invention, the patient trigger sensor126may be replaced by an additional function by differential pressure transducer38wherein the differential pressure detected by differential pressure transducer38is used to detect the patient breathing attempt trigger when there is an absence of gas flow through either of the nasal cannula lumens70and74respectively.

In another aspect of the present invention, the differential pressure transducer38may provide data for the monitoring of the connection and/or gas flow within the cannula56of the present invention. As depicted inFIGS. 8a-d, deviations from a normal or expected gas flow or pressure profile would be indicative of inadequate flow, cannula disconnection, or cannula kinking.FIG. 8adepicts the normal, expected differential pressure profile within the gas mixing chamber60of the cannula assembly54. The gasses are delivered through first and second lumens at their different patterns, therefore the differential pressure profile exhibits five regions a-d in a differential pressure detection cycle. Regions a and e are representative of when there is no gas flow being supplied from supply tanks14or16. Region b is representative of the period when a proper gas flow is being supplied by supply tank14to the patient. This gas supply continues throughout region c as well, but in region c proper gas supply from supply tank16is also provided thereby producing the shift in differential pressure within the gas mixing chamber60. In region d, the pulse of medical gas supplied from supply tank14has ceased and as such the only medical gas supply is that supplied from supply tank16as the differential pressure indicates. Finally in region e both pulses of medical gas from the supply tanks14and16have ceased and no differential pressure in the gas mixing chamber60is sensed by differential pressure transducer38.

FIG. 8bdepicts the differential pressure profile that would be indicative of an alarm condition and/or system failure because of inadequate gas flow through one or both of the lumens. When the pulse of medical gas in the first lumen begins to flow in region b, the signal from the differential pressure transducer is only half the amplitude of that same portion of the cycle inFIG. 8a. Because the resistance within the cannula is assumed to be linear, it can be expected that only half the requested flow has been achieved. This indication is visible throughout the entire pulse of the first medical gas by the reduced differential pressure signal detected in regions b and c.

FIG. 8cdepicts the differential pressure profile of the alarm condition of a disconnected nasal cannula. InFIG. 8cthe same sequence of gas pulsing through the nasal cannula is present that was seen inFIGS. 8aandb; however, because of the near absence of back pressure when one or both of the nasal cannulas are disconnected, there is very little change in the signal during the gas pulsing. Therefore a differential pressure profile such as shown inFIG. 8cis indicative of a disconnected nasal cannula.

Finally inFIG. 8danother differential pressure profile indicative of the alarm condition of a kinked nasal cannula is shown. Once again, the differential pressure profile has the same sequence of gas pulses that are seen in the normal operation differential pressure profile; however, in the event of a kinked nasal cannula, the result will be a spike in the signal from the differential pressure transducer. The spike in the signal in region b is indicative of a kink in the first lumen and the spike in the signal in region d is indicative of a kink in the second lumen. Therefore,FIG. 8ddepicts a complete kink of both the first and second lumens of the cannula of the present invention.

The differential pressure profile detected by the differential pressure transducer38thus provides a means for detecting a patient breath attempt thus triggering the delivery of a ventilator breath and pulses of supplemental medical gasses. The differential pressure transducer38also provides the additional functionality of monitoring the gas flow in the lumens of the multiple lumen cannula of the present invention as well as monitoring the quality of the patient connection to the cannula of the present invention.