Surgery – Respiratory method or device – Inhaled gas heated or humidified by exhaled gas
Reexamination Certificate
1998-07-10
2002-04-02
Weiss, John G. (Department: 3761)
Surgery
Respiratory method or device
Inhaled gas heated or humidified by exhaled gas
C128S205120, C128S203160
Reexamination Certificate
active
06363930
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus useful to exchange heat and moisture in respiratory gas applications. More particularly, the invention relates to apparatus for heating and humidifying respiratory gases which exchange heat and moisture with respiratory gases, and preferably provide, e.g., generate, additional heat and/or moisture available to the respiratory gases.
During surgery and other medical procedures, a patient is frequently connected to an anesthesia machine or ventilator to provide respiratory gases to the patient. The respiratory gases passed to the patient are advantageously heated and humidified so that the gases entering the patient are of a suitable temperature and humidity so as not to adversely impact the patient. Heat and moisture exchangers (HMES) are often used to provide heat and humidity to the respiratory gases entering the patient. Typically, these HMEs are located so that respiratory gases from the patient pass through a tracheal tube into the HME, often a fibrous or other gas permeable material, which accumulates or collects heat and moisture from the exhaled gases. During the inhaling of respiratory gases, for example, from an anesthesia machine, the HME provides both heat and moisture to these respiratory gases prior to the gases entering the patient. Over a period of time, the HME is effective to maintain a certain level of temperature and humidity in the respiratory gases entering the patient.
Such HMEs do, however, have certain drawbacks. Thus, standard HME units currently commercially available are often less than satisfactory in delivering heat and/or moisture to the patient, for example, during the initial operation of the unit, and have configurations and structures which can cause clinician anxiety and patient trauma, for example, when the patient or HME unit is moved and the like situations. Also, during the initial or start up phase of the operation of a HME member, the amount of heat and moisture being exchanged out of the HME member to the respiratory gases being passed back to the patient is relatively low, for example, because the HME member is at a reduced temperature and a reduced moisture content. This “start up” problem can adversely affect the patient. One approach to overcoming at least a portion of this problem is to provide the HME member with a hygroscopic component, for example, calcium chloride and the like components, which is effective to generate a limited amount of heat as the exhaled gases leaving the patient pass through the HME member. This provides a “quick warm up” HME member and at least provides a heated respiratory gas stream to the patient relatively quickly. However, the degree of humidification of the respiratory gases being passed to the patient still is relatively low during the first portion of the HME member operation, in part because of the water held by the hygroscopic component.
In addition, the inefficiencies of the typical HME member are such that a certain portion of the heat and moisture collected by the HME is lost, for example, to the environment, rather than being passed back to the patient by exchange with respiratory gases. The degree of heating and/or humidification of the respiratory gases varies over time which can adversely impact the patient.
In short, although the current commercial HME units provide certain benefits, they are not very user friendly to the patient.
It would be advantageous to provide apparatus by which respiratory gases can be effectively and reliably heated and humidified so that the comfort and safety of the patient is enhanced.
SUMMARY OF THE INVENTION
New apparatus for heating and humidifying respiratory gases have been discovered. Such apparatus provide for exchanging heat and moisture with respiratory gases exhaled by the patient and providing heat and moisture to the respiratory gases being inhaled by the patient. In general, the present apparatus are more patient friendly, that is provide for increased comfort and/or reduced trauma to the patient undergoing surgery or other treatment, than the current commercially available HMEs. Various features of the present invention provide enhancements as to the comfort and safety of the patient. Thus, the use of the present apparatus effectively provides heat and moisture to respiratory gases with reduced, if any, adverse effects on the patient. One important feature of the present apparatus is enhanced start up effectiveness so that the “warm up” or “break in” time period of the system is reduced or even eliminated. These benefits are obtained with apparatus which are straightforward in construction, easy and relatively inexpensive to manufacture and use, and are effectively controlled to provide the results desired.
Generally, the present invention is directed to apparatus for heating and humidifying respiratory gases.
In one broad aspect of the present invention, apparatus for heating and humidifying respiratory gases comprise a housing, a filter element, and a gas permeable member. The housing has an inlet adapted for connection to a tracheal tube device and an outlet adapted for connection to a tube or tubes for passing respiratory gases, for example, to and from an anesthesia machine, ventilator and the like. The inlet and the outlet are positioned so that respiratory gases passing through the housing pass therebetween. The filter element is located in the housing and is adapted to filter respiratory gases passing through the housing. The gas permeable member is positioned in the housing between the inlet and the outlet and is adapted to exchange heat and moisture with respiratory gases passing through the housing. In general, the housing is designed to be compact and to reduce the amount of dead space between the tracheal tube device and the tube (or tubes) for passing respiratory gases. The compact housing allows the apparatus to be used and perform its functions more unobtrusively, relative to prior art HME devices. The reduced dead space increase the use efficiency of heat and moisture passing into and/or generated in the housing.
The present apparatus preferably are of modular design. This reduces manufacturing costs and provides performance benefits which inure to the patient. For example, the housing has an inlet portion including the inlet and an outlet portion including the outlet. The inlet portion of the housing is detachably secured to the remainder of the housing and is adapted to be replaced, preferably together with the filter element, while the outlet portion of the housing remains connected to the tube(s) for passing respiratory gases. This detachable or separable inlet portion of the housing is very effective in providing for reduced resistance to flow of respiratory gases through the housing. For example, after a period of time, material such as mucous from the patient tends to collect and/or settle on the filter element, creating a flow resistance. Rather than having to replace the entire apparatus, the inlet portion of the housing is removed, together with the filter element. A new inlet portion/filter element combination is substituted and the resistance to respiratory gas flow is reduced.
The filter element preferably is secured to the inlet portion of the housing. In one very useful embodiment, the inlet portion of the housing includes a first portion of a dogging assembly and the outlet portion of the housing includes a second portion of the dogging assembly positioned to matingly engage the first portion to detachably secure the inlet portion to the outlet portion of the housing. The inlet portion of the housing preferably includes a peripheral ring or rim extending radially outwardly of the first portion of the dogging assembly. This peripheral rim is adapted to prevent the inlet portion of the housing from snagging other objects, for example, on the patient in the operating or treatment room. This feature allows for movement of the apparatus on or about the patient without the apparatus being snagged or otherwise caught up on such other objects. This f
Clawson Burrell E.
Weigl James
Enternet Medical, Inc.
Srivastava V.
Stout, Uxa Buyan & Mullins, LLP
Uxa Frank J.
Weiss John G.
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