Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
2001-07-09
2003-09-30
Bennett, Henry (Department: 3743)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204270
Reexamination Certificate
active
06626174
ABSTRACT:
The invention relates to a device for assessing the applied or exerted air pressure during automatic respiration through positive airway pressure. The device can be used in the CPAP (continuous positive airway pressure) therapy. The CPAP therapy is described in more detail in Chest, vol. 110, pages 1077 to 1088, October 1996 and Sleep, vol. No. 19, pages 184 to 188.
In the CPAP therapy, a patient is supplied, e.g. at night, with a constant positive pressure via a nose mask. This positive pressure should guarantee that the upper airways remain completely open during the entire night and thus no obstructive respiratory disorders occur. Since the required pressure can change at night depending on the sleep stage and the body position, either a variable pressure must be supplied to the patient or the highest pressure which is required at night. It is advantageous if the patient can be supplied with an optimal pressure. An optimal pressure P
opt
, or also effective pressure P
effective
is the pressure at which the patient is supplied with a normal respiratory flow and an increase in the pressure does not lead to an increase in the respiratory gas flow.
FIG. 1
shows that the optimal air pressure is the kink of the curve of the respiratory gas flow {dot over (V)} depending on the pressure.
The device according to the invention can be used in the therapy device (AutoSet) in which a maximal respiratory pressure is automatically adjusted. This device is intended for the therapy adjustment in a hospital.
A further application of the device according to the invention is a therapy device (AutoCPAP) in which the air pressure is adjusted to the different requirements of the patient during the night. In this device the optimal pressure is continuously adjusted in accordance with the requirements of the patient. This means that the pressure is increased, maintained or reduced.
In a device with an algorithm for the adjustment or adaptation of the positive air pressure in the CPAP therapy, an initial respiratory pressure can be compared with a threshold value for the respiratory gas flow. In the device the critical pressure P
crit
and the airway resistance are calculated, and then the desired value of the positive air pressure is controlled such that it is either maintained or changed accordingly.
It is the object of the present invention to provide a device for assessing the applied air pressure during automatic respiration through positive airway pressure by means of which it can be determined whether the applied pressure is the optimal air pressure or deviates therefrom.
For achieving this object, the invention starts out from the basic idea of changing the positive air pressure being applied by means of an adjusting means such that at least three different pressure values can be adjusted, and measuring the respiratory gas flow for the three different pressure values by means of a measuring means. On the basis of the relation of the respiratory gas values to each other, an assessing means assesses whether the applied air pressure lies below or above the optimal air pressure, or whether it is the optimal air pressure.
The invention is advantageous in that already after a few minutes, i.e. without unnecessary discomfort for the patient, it can be determined in which range the applied air pressure lies, so that the air pressure can be adjusted to the optimal air pressure in case of a possible deviation.
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Dtsch. Med. Wsch.r, 122, pp 1482-1488 (1997) English Abstract.
Dtsch. Med. Wschr., 122, pp 789-793 (1997).
Jul. 16, 1999 Office Action from Germany priority application No. 19849571.4.
Drumm Peter
Genger Harald
Bennett Henry
Dagostino Sabrina
Map Medizintechnik fur Arzi und Patient GmbH & Co. KG
Ohlandt Greeley Ruggiero & Perle LLP
Rauchfuss, Jr. George W.
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