Mechanical respiration and mechanical breathing assistance are usually used in respiration if the spontaneous breathing of a patient is insufficient or even not present at all. If spontaneous breathing is insufficient, mechanical breathing assistance is often sufficient. The patient must be respirated with a machine in the absence of spontaneous breathing. There are a number of different forms of respiration, in case of both mechanical respiration and mechanical breathing assistance, but they all have in common the fact that a breathing gas stream is fed to the patient to be treated in a controlled manner.
One or more therapeutically active substances may also be added to such a breathing gas stream, and these substances can be administered to the patient in this manner by inhalation. Such therapeutically active substances may be, for example, anti-infectious agents, for example, substances with antibacterial action, e.g., antibiotics; substances with antiviral action, or substances with antimycotic action. Immunomodulators or substances for the treatment of the lung surface, for example, artificial pulmonary surfactants, may also be administered.
Corresponding substances to be administered are usually transformed into a state in which they are carried by the gas from a liquid or solid, for example, powdered state by means of an atomizer, so that they can be fed as an aerosol into the breathing gas stream. An aerosol is usually defined here as a dispersion of a solid or of a liquid, especially of solid or liquid suspended particles (aerosol particles), in a gas (carrier gas). The aerosol prepared can then be fed into the breathing gas stream and flow together with the breathing gas stream into the patient's airways. For example, so-called “metered dose inhalers” (MDI) are used for atomization. The aerosol particles can reach, for example, the alveoli in the lungs, where they are taken up by the patient via the lung epithelium.
Besides the treatments of special pulmonary diseases in adults, the administration of therapeutic active substances to newborn and premature babies in this way is of great interest as well. For example, the administration of surfactant can make a decisive contribution to the treatment of the so-called Neonatal Respiratory Distress Syndrome (NRDS). Pulmonary surfactants are developed too weakly in premature and newborn babies who have this disease. This implies the risk that the alveoli of the not yet fully matured lungs collapse in themselves and stick together. The gas exchange area of the lungs can thus decrease considerably, so that respiratory distress syndrome develops. A deficiency of pulmonary surfactants may lead to respiratory distress syndrome (adult respiratory distress syndrome, ARDS) in adults as well. Respiratory distress syndrome can be treated or prevented in both cases by the administration of an artificial surfactant. This artificial surfactant to be administered is typically a phospholipid protein composition, which affects the surface tension at the interface between lung tissue and air in the alveoli.
Independently from the administration of therapeutic substances, it is usually necessary during the artificial respiration or breathing assistance of a patient to humidify the breathing gas stream administered in a physiologically adequate manner. This is important to prevent the ciliary epithelium from drying out and an increased risk for pneumonia, which is associated therewith. Moisture is therefore usually fed to the breathing gas stream in a controlled manner.
For example, EP 0 535 952 B1 provides for an air humidifier, in which a breathing gas stream is sent through a humidifying chamber having a gas inlet and a gas outlet. The humidifying chamber is arranged above a hot plate, so that the breathing gas stream leaving the humidifying chamber is humidified in a physiological manner and is brought to an adequate temperature.
U.S. Pat. No. 3,871,373 also describes a device for humidifying and administering a gas to a patient. The device has a gas line, which delivers oxygen as well as optionally an anesthetic. The gas line has a wall, which may be permeable to water vapor. The device has, furthermore, a water chamber, which extends along a common section with the gas line and through which liquid water is transported. The water chamber is likewise defined by the water vapor-permeable wall, so that the liquid water can evaporate through this wall into the gas line. The oxygen stream flowing through the gas line is humidified in this manner before it reaches the respiratory tract of the patient to be treated.
For administering an aerosol to a patient with simultaneous breathing assistance, WO 2012/020004 A1 provides for a device, which comprises a source for a breathing gas, on the one hand, and a source for an aerosol, on the other hand. A so-called aerosol flow, i.e., an aerosol stream, which is led into the device tangentially, i.e., at right angles to the breathing gas stream originating from the breathing gas source, is generated from the aerosol source in this device. This device is used especially to prevent deposits from forming in the device or in the upper airways during the administration of surfactant.
Even though it is known in all these solutions that the breathing gas itself is humidified, it is problematic that the part of the stream that carries the therapeutically active substance, i.e., the aerosol, is not humidified or is not humidified sufficiently or cannot be humidified or cannot be humidified sufficiently. In particular, the problem may frequently occur that the therapeutically active substances are present as dry solids before they can be atomized. However, the risk that the substance will form lumps may develop as soon as this dry solid substance comes into contact with moisture, so that the aerosol particles formed become much too large and cannot enter the alveoli of the lungs any longer. The substance may already become stuck in this atomized state in this manner in the worst case. However, there is a risk in both cases that a specific and controlled metering of the therapeutically active substance cannot be ensured any more to the extent at which this is often necessary. Conventional devices, which provide for feeding therapeutically active substances to a humidified breathing gas stream, therefore often fall back on humidification by means of special devices, which is usually expensive and complicated. This may also be associated with the use of a large amount of consumable materials. Provisions may also be made, as an alternative, for eliminating humidifying altogether. However, this does, in turn, lead to the risk that the ciliary epithelium will dry out, which implies an increased risk for pneumonia. Finally, It is also possible to do away with an actually undesired longer duration of administration of therapeutically active substances. However, this does, in turn, imply a marked curtailment of the desired therapeutic possibilities.