ARDS (acute respiratory deficiency syndrome) designates a sudden respiratory failure, which develops due to an acute inflammatory process of the lung tissue, in which the lungs extensively lose their ability to exchange gas. The permeability of the blood vessels in the pulmonary alveoli increases in ARDS and the pressure in the vessels drops, whereas it rises in other parts of the lung tissue. This leads to a life-threatening shortness of breath and to insufficient oxygen supply for the blood. The life-threatening hypoxia in the blood must be treated as quickly as possible by mechanically supporting breathing, i.e., artificial respiration with air enriched with oxygen. However, noninvasive respiration methods with merely increasing the oxygen concentration in the breathing air being supplied are often insufficient for the treatment of ARDS, because respirated ARDS patients have atelectatic (i.e., collapsed) lung areas, which can be opened (recruited) and made usable for gas exchange with a high respiration pressure only. However, the patient must be intubated for this, i.e., a tube (flexible tube) is pushed into the patient's trachea through the mouth or through the nose. The respiration is preferably carried out via an endotracheal tube or via a tracheotomy cannula. An endotracheal tube normally comprises a thin flexible tube, which is opened at both ends and whose lower end is pushed into the trachea. A cuff, which can be inflated via a thin flexible tube, which extends on the side of the tube, is located a short distance above the lower end. The trachea is sealed hereby. At the upper end, the endotracheal tube is equipped with a standardized connection piece, which makes possible connection to a respirator. A tracheotomy cannula is used in case of tracheotomy. The tracheotomy cannula also has an inflatable “block,” which makes respiration possible and at the same time prevents pharyngeal secretion from entering the lungs downwards.
A residual pressure (PEEP=positive end-expiratory pressure) is preferably maintained at the end of expiration during the artificial respiration of ARDS patients. The pressure in the pulmonary alveoli is increased by the PEEP respiration, as a result of which the pulmonary alveoli are expanded, which leads to an enlargement of the area for the gas exchange and thus to an improvement of oxygen uptake. Furthermore, the risk of collapse of the pulmonary alveoli during expiration is reduced. The end-expiratory pressure in PEEP respiration frequently equals 10 mbar or higher in ARDS patients in order to prevent the lung areas opened with difficulty from recollapsing. It is necessary in most cases to artificially respirate an ARDS patient over several days or even weeks. However, some steps are necessary in the course of respiration in routine clinical practice, for example, suction of fluids from the lungs, repositioning of the patient, changing of the tube system, of the filter or of the respirator. The necessary pressure in the lungs cannot be continuously maintained during the performance of these clinically necessary steps, so that the damaged lung areas must be recruited time and time again.
U.S. Pat. No. 4,351,328 describes an adapter, which is designed to connect a respirator and an endotracheal tube. The adapter is provided, furthermore, with an opening, which is closed by means of a valve. The valve is designed as a slot valve and can be pierced by the suction tube when the latter is introduced into the opening from the outside.
U.S. Pat. No. 4,416,273 discloses a connection adapter for an endotracheal tube. The adapter has a port provided with a lamellar valve in order to make it possible to insert a suction catheter into the tube from the outside.
DE 32 04 110 C2 pertains to a tracheal tube for artificial respiration. The lower part of the tracheal tube is surrounded by a balloon cuff, which can be inflated via an inflating cannula to the extent that it comes into contact with the tracheal wall. A breathing tube connected to a respirator and a pressure-measuring cannula are provided in the interior space of the tracheal tube in order to make it possible to measure the pressure drop in the breathing tube or the intratracheal pressure.
DE 198 38 370 C1 describes a device for removing sputum from a tracheal catheter. The device has three openings, wherein a first opening is connected to the end of the catheter projecting from the trachea, a second opening can be coupled with an air filter for cleaning and sterilizing the air to be breathed in, and a third opening is connected to a collecting bag into which the sputum can flow. A spring-tensioned piston for closing the third opening is controlled by the breathing air during inspiration and expiration.
DE 41 42 295 C2 pertains to a valve for generating a control pressure in a pneumatic switching circuit. The valve has the embodiment of a circular closing element and has incisions, so that eight circle segments are formed, which can be bent up around the circumferential line of the closing segment. The extent of bending up changes depending on the pressure of the fluid acting on one side of the valve.
DE 10 2005 014 650 B3 discloses a connection piece with a distal end and a proximal end for connecting a tracheal tube and a respirator as well as with a branch for inserting a catheter. A valve made of material deformable elastically at least in some areas is provided in the branch, and said valve forms a beak section with a slot, which is opened during the insertion of the catheter. Closed suction systems, as they are shown in this document, prevent only the pressure during suction. Changing of the device and changing of the closed suction system itself, which is necessary at 48-hour intervals for hygienic reasons, continue to lead to collapse of the lungs and to a subsequent stressful recruitment maneuver.
None of the above-mentioned documents pertains to the respiration of ARDS patients, and none of these documents discloses respirators or respirating means in the pneumatic switching circuit between a respirator and a patient, which are designed to maintain a certain air pressure in the lungs of the patient to be respirated even when, for example, the respirator is being replaced.