Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
2000-10-16
2003-12-30
Lo, Weilun (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204220
Reexamination Certificate
active
06668828
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the general art of surgery, and to the particular field of introducing material to a patient for therapeutic or diagnostic purposes, most specifically, the invention relates to NO therapy.
BACKGROUND OF THE INVENTION
The use of therapeutic gases to treat a human or animal patient has been known in the art for many years. A number of different gases may be added to a respiratory gas that is inhaled by a spontaneously breathing, non-ventilated patient. These gases may be used to achieve some therapeutic effect, service a diagnostic function or have some other desirable purpose. Such gases will be referred to herein as “therapeutic gases.” One skilled in the delivery of therapeutic gas will understand that the disclosure can be used to teach either human or animal patients. Accordingly, no limitation to human is intended by references to patient in this disclosure.
One therapeutic gas is nitric oxide (NO), which is administered by inhalation in low concentrations to treat primary or secondary pulmonary hypertension or other diseases. In many cases, nitric oxide or other therapeutic gases come from a high concentration source such as a high concentration compressed gas cylinder. The gas source may be pure or may contain some concentration of therapeutic gas in a carrier gas. There may also be cases where more than one therapeutic gas is used, with or without a carrier gas or gases. It is often necessary to dilute therapeutic gas to a lower concentration and mix it with air and/or oxygen prior to delivery to the patient. This dilution may be necessary to achieve a desired dosage concentration and/or to avoid or reduce adverse bioeffects that may occur if high concentration gas is delivered to the patient. If the therapeutic/carrier gas is not sufficiently oxygenated, it is necessary to mix it with air prior to delivery to the patient. In some cases, it is necessary to add supplemental oxygen to the mixture to avoid a hypoxic respiratory mixture or to enrich the oxygen content of the respiratory gas above twenty-one percent. In the latter case, the oxygen will also be considered as a therapeutic gas.
NO is one of a number of therapeutic gases that are administered to a patient and require dilution from a high concentration form to a lower, safer concentration before administration to a patient. No will be the primary focus of this disclosure; however, one skilled in the surgical arts will understand that the disclosure can be used to teach other gases as well. Accordingly, no limitation to NO is intended by the references to NO in this description.
The art contains several devices and systems to deliver therapeutic gas to a spontaneously breathing, non-ventilated patient. However, as will be discussed, each of the known systems and devices has drawbacks.
A system that has continuous flow to a mask is one such known system. A therapeutic gas, oxygen and air are supplied from sources such as compressed gas cylinders or a hospital wall. A continuous flow of these gases is titrated together before delivery to a patient. The flow rate of each gas is set to achieve the desired concentration of the therapeutic gas and oxygen in the respiratory gas. The total flow rate is set greater than the peak inspiratory flow rate. If a reservoir bag is added to the inspiratory portion of the overall circuit, then the total flow can be reduced, but must still be greater than the minute volume of the patient. The mixed gas is connected into the mask, from which the patient inhales. Exhaled gas and excess inhalation gas flow from an outlet side of the mask and may be scavenged. This system has the disadvantage of wasting gas since not all therapeutic gas is inhaled by the patient. Scavenging is required to prevent the therapeutic gas from entering the environment. In addition, large volumes of air and/or oxygen must be supplied to dilute/mix the therapeutic gas. Also, therapeutic gas is delivered to the entire respiratory tract, not just the areas where it is needed. This may increase adverse bioeffects and the possibility of undesirable reaction products from the therapeutic gas. The mask also makes eating and talking difficult and is also aesthetically unappealing. Still further, a mask may make some patients nervous and cause anxiety by making them feel confined.
Yet another system uses a bolus pulse of therapeutic gas to a mask. In this system, therapeutic gas is delivered to the patient as a bolus of gas that is delivered via the mask. The bolus of therapeutic gas is delivered over a short period of time and is not significantly diluted by inhaled air or supplemental oxygen. Supplemental oxygen may also be delivered via the mask. The patient's breathing waveform is monitored and the bolus of therapeutic gas is delivered to the mask intermittently, in synchronization with the respiratory waveform so that the therapeutic gas is inhaled at a set phase of the respiratory waveform. The bolus is preceded and/or followed into the respiratory tract by air/oxygen. This system and method has the disadvantage that it does not dilute the therapeutic gas, so a high concentration source cannot be used. In addition, the short duration of the bolus means that a higher concentration of therapeutic gas is required to deliver the same number of molecules of the gas to the patient. This could have adverse bioeffects. This method does not have the flexibility of varying the concentration of the therapeutic gas at various times during inspiration. The mask has the same drawbacks as heretofore discussed.
Yet another system and method uses an undiluted pulse via a nasal cannula. A nasal cannula is a device that can be used to transmit therapeutic gas from one or more therapeutic gas sources to the nose of a patient for inhalation. It includes one or more connectors at one end of the device to connect to one or more therapeutic gas sources, one or more long lumens to transmit the gas, and nasal prongs at the other end to inject one or more therapeutic gases into the patient's nose. The word “lumen” will be used in this disclosure to represent a long, narrow, flexible fluid conduit that is less than 0.8 cm in internal diameter. A nasal cannula is typically much less obtrusive than a mask and allows the patient to talk and eat while receiving gas therapy. In the method of undiluted pulse delivery via a nasal cannula, therapeutic gas is delivered via a nasal cannula as an intermittent flow pulse during inspiration. Air pressure in the nares drops at the start of inspiration. This pressure drop is transmitted through the cannula and is detected in the pulse delivery device. Therapeutic gas flow is turned on for a period of time during inspiration. The therapeutic gas flows directly into the nares from the cannula. While overcoming many disadvantages associated with a mask, this method also has disadvantages as practiced in the known art. For example, the therapeutic gas is not diluted prior to entering the nares in many known systems. If a high concentration source is used, high concentration gas may contact the tissues before it is diluted in the respiratory tract. This may have adverse bioeffects. If lower concentration gas is used, the source lifetime/size advantages of a high concentration source are lost. Also, the final dilution concentration in the respiratory tract is limited. It is lower for any given volume of therapeutic/carrier gas, and this volume must be limited to avoid a hypoxic respiratory gas mixture. Still further disadvantages will be discussed below in reference to the use of known cannulas.
Still another known method and system for administering therapeutic gas to a patient includes an undiluted pulse via a nasal cannula and oxygen via another lumen. In this method, gas may be delivered as discussed above, with the addition of supplemental oxygen delivered via a second lumen in a dual lumen cannula. This method has all the disadvantages discussed above, except that it allows a higher diluted concentration to be delivered to the re
Figley Curtis B.
Hunt Darin W.
Miller Christopher C.
Gernstein Terry M.
Lo Weilun
Mitchell Teena
Pulmonox Technologies Corporations
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