Surgery – Respiratory method or device – Means for cooling respiratory gas or respiration device
Reexamination Certificate
1997-11-03
2001-12-25
Lewis, Aaron J. (Department: 3761)
Surgery
Respiratory method or device
Means for cooling respiratory gas or respiration device
C128S204180
Reexamination Certificate
active
06332462
ABSTRACT:
Nasal, positive-pressure respiratory devices are used for avoiding so-called obstructive sleep apnea.
Obstructive sleep apnea describes a collapse of the respiratory passages in the pharyngeal region that repeatedly occurs during sleep and that leads to respiratory arrests and, when it occurs frequently, instigates lasting damage to one's health due to lack of sleep and lack of oxygen.
In the positive-pressure respiratory devices known under the name nCPAP (nasal continuous positive airway pressure), a fan creates a constant pressure that is fed into the respiratory passages via a tube and a nasal mask. The positive pressure in the respiratory passages prevents the sealing of the pharyngeal musculature and thus eliminates the respiratory arrests.
For drawing off the expirated, consumed air, a continuous stream of exhaust air is exhausted via fine exit openings along the breathing mask. The exhaust air exit openings must be made narrow so that a throttling effect is provided and the positive pressure does not collapse but rather only a predetermined amount of exhaust air exits.
In order to completely draw off the consumed air, the amount of exhaust air must be as large as the amount of expirated air.
A health damaging effect results from positive-pressure respiration in that the air is warmed through the compression in the fan and that the relative humidity of the air is consequently reduced in accordance with the laws of nature. The dry air flowing continuously as a result of the stream of exhaust air dries out the mucous membranes of the respiratory passages and results thereby in continuous complaints (symptoms) comparable to a cold.
In order to avoid these problems, it is known to employ an air humidifier between the fan and the breathing mask.
In the early time of nasal, positive-pressure respiration, complex, regulated respiratory air humidifiers were used for this purpose, i.e. as are used in intensive care medical treatment.
In the meantime, a home, positive-pressure respiration during sleep has been shown to be a matter of life or death for tens of thousands of sleep apnea sufferers.
For this purpose, the complex, respiratory air humidifiers of intensive care medical treatment are too complicated and too expensive.
It thus became known to use so-called cold air humidifiers, wherein the air stream coming from the fan flows through a closed housing in which water is bubbled by means of a pump.
Since, however, it was shown during their use that the drying out of the mucous membranes in the respiratory passages could not be sufficiently avoided using the cold air humidifiers, so-called warm air humidifiers are primarily used at the present time, as is described in the instruction manual for PRIESS med. Technik's “Sullivan Atemgasanfeuchter (respiratory gas humidifier) Model HC 100,” said firm residing at Karstrasse 17a, 41068 Mönchengladbach, Germany.
In
FIG. 1
of the drawings, this prior art is illustrated schematically.
The fan
1
creates an air stream with a positive pressure of approx. 3 to 18 mbars, whereby the air stream heats up by approx. 1 to 2° C. over the ambient temperature. The air stream is fed via a tube
4
from the fan
1
to the air humidifier
5
and is further led from there, again via a tube
6
, to the nose mask
7
and the fine exit openings
8
for the exhaust air stream
9
, In the evaporation container
2
of the air humidifier, the water filled thereinto is evaporated by an electric heater
3
. The air stream flowing therethrough accepts this water vapor in the evaporation container
2
and is thus simultaneously warmed by approx. 4 to 60° C. over the ambient temperature.
With such warm air humidifiers, a sufficient humidification of the respiratory air is achieved to avoid the drying out of the mucous membranes.
The warm humidification of the respiratory air, however, creates the following serious problems:
Through the warm humidification, the air that had already been warmed by the fan is warmed even more. The inhalation of this warm and humid air results in subjective respiratory distress and results thus in frequent sleep interruption and subsequently in significant problems in falling asleep.
Since the temperature of the warm, humidified air is higher than the ambient room temperature when it exits the humidifying container, condensation forms in the respiratory tube
6
and in the nose mask
7
. In order to avoid the formation of (bacterial) cultures (colonies) that are dangerous to one's health as a result of this humidity, the tube
6
must be thoroughly washed and dried daily.
A serious problem results furthermore along the fine exit openings
8
for the exhaust air
9
. Since the exhaust air
9
expands when it exits and, as a result, cools down adiabatically, further condensation from the humidity-saturated air forms in the fine exit air openings
8
and partially blocks these. As a result, the expirated air is no longer sufficiently exhausted. The result is sleep and health disorders due to lack of oxygen.
Regarding the prior art, further reference is made to DE-C-6 34 919, which relates to a breathing chamber with cooled air, and to WO-A-9 320 874, which relates to an apparatus for destroying microorganisms.
The object of the invention is to provide an apparatus for creating respiratory air for home positive pressure—CPAP (Continuous positive pressure) respiration of persons with obstructive sleep apnea syndrome such that the occurrence of condensation is avoided during the creation of medically sound air humidity of the respiratory air.
For solving this problem, the features cited in claim
1
are provided. Preferred embodiments of the invention can be found in the dependent claims.
Before going into further advantages of the invention, it will be noted in regard to the aforementioned prior art that an air stream under positive pressure is created by the apparatus in accordance with the invention that is subjected to treatment prior to its introduction to the nose mask and the exit openings, said treatment being a humidifying treatment in the case of the prior art.
The sufficient air humidity is achieved by simple means without having to accept the deficiencies of the known positive-pressure respiration devices: the increased temperature of the respiratory air; the danger of the formation of health-threatening bacteria and lack of oxygen due to the blockage of the air exit openings through condensation.
The relative air humidity is known to be determined by the air temperature for invariant, absolute air humidity. This law of nature results in the damaging reduction of the relative air humidity through the warming by approx. 1 to 20° C. during the creation of the positive pressure in the fan of the positive-pressure respiratory device.
If the air supplied by the fan is now cooled with suitable means by approx. 5° C., the relative air humidity is then higher than prior to the compression. Since the temperature of the cooled air is then approx. 3° C. lower than the ambient temperature, condensation does not form in either the breathing tube or in the exhaust air slits of the nose mask due to the high relative air humidity.
The air tube must not longer be washed out and dried daily. The exhausting of the consumed respiratory air is not hindered by condensation in the exhaust air openings. The lack of oxygen as a result of insufficient drawing off of the exhaust air is thus avoided.
The cooled respiratory air gives the subjective impression of being fresh and allows a restful sleep.
Furthermore, the cooled air stream in accordance with the invention draws less humidity from the mucous membranes in accordance with the laws of nature than an air stream of the same relative air humidity but higher temperature of the known methods.
The cooling of the respiratory air is carried out in accordance with the invention via a heat exchanger, whereby the air stream supplied by the fan flows through a cooling profile or section (heat sink) in a closed housing.
The amount of heat that is to be drawn off from the air stream of max.
Connolly Bove & Lodge & Hutz LLP
Lewis Aaron J.
LandOfFree
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