Noninvasive ventilation of the lungs — a method of respiratory support which means refusal of an intubation of a trachea and a tracheostomy and carrying out ventilation of the lungs by means of special front masks. The method allows to lower number of complications of an intubation, tracheostomy and also to reduce need for sedation of patients.
Historically noninvasive ventilation of the lungs appeared the first — to remember the first models of respirators like "iron lungs" (Iron Lung) enough. Actually the intubation of a trachea was entered into practice of respiratory support a bit later. In the next years recession of interest in the field of noninvasive ventilation and prevalence of invasive techniques was noted. However emergence recently of modern respirators with work on the principle of the active valve and development of an electronic and computing component of the equipment, interest in noninvasive ventilation increased again. Further development of the NIVL method is connected with introduction in practice of comfortable tight or partially tight masks, since 1981.
In the early nineties in the medical market the portable, convenient and inexpensive respirators which are specially developed for NIVL were designated. It allowed to conduct the new researches devoted to NIVL by means of front masks at ODN of various nature in which advantages of this method of respiratory support were proved.
It is known that a main objective of therapy of patients with respiratory insufficiency is achievement of adequate oxygenation. In the majority of the researches devoted to NIVL considerable improvement of parameters of oxygenation was shown. At an anoxemia during NIVL involvement in process of ventilation of not ventilated or badly ventilated earlier alveolar units is the cornerstone of improvement of gas exchange that leads to improvement of the ventilating and perfusion relations and decrease in the shunt.
In comparison with traditional artificial ventilation of the lungs, NIVL has a number of essential features. First, at noninvasive ventilation there is always this or that leak of respiratory mix. If leak high, then can lead it to considerable falling of minute ventilation. Prevention of it is careful selection of a mask for the patient and its reliable fixing. Unlike traditional artificial ventilation of the lungs, installation of parameters at NIVL is always made taking into account leak. The second feature of NIVL is need of accounting of the changing resistance of the upper airways.
If to speak about the ventilation modes which can be used at NIVL then practically all modes theoretically can be used, however preference is usually given some of them: CPAP (constant positive pressure in respiratory tracts), PSV (support by pressure on a breath), BiPAP (the mode with two levels of positive pressure on a breath) and PAV (proportional assisted ventilation).
For carrying out noninvasive ventilation of the lungs two types of respirators can be used: traditional respirators for an intensive care and specialized portable devices for NIVL. The first type of respirators has some shortcomings which are connected with impossibility of compensation of leak as such device is intended for carrying out ventilation and a tight system. Portable devices have lower cost, can compensate even high leak, but they have no all opportunities for respiratory monitoring.
If to speak about masks for NIVL, then nasal or front masks can be used. The first are more easily had by patients, but do not give the chance to provide due tightness when opening by the patient of a mouth. Front masks allow to avoid big leak, but are worse transferred by patients. It is also necessary to mean that the position of a mouth is of great importance at NIVL. In particular, during sleep at the patient the open mouth can lead to considerable leakages and decrease in efficiency of ventilation. One more type of the interface is a special helmet which completely covers the patient's face.
NIVL can be applied at patients from giperkapnichesky and hypoxemic ODN of various genesis. Major candidates for NIVL are patients at whom traditional invasive IVL can be the dangerous procedure owing to high risk of possible complications. NIVL is contraindicated at instability of a hemodynamics, an apnoea, problems with ensuring protection of respiratory tracts, the consciousness disturbances, anatomic and other disturbances interfering correct placement of a mask.
To shortcomings of NIVL a possibility of development of specific complications, for example, of conjunctivitis, face skin necroses, an aerophagia and so on belong. This type of ventilation demands good contact with the patient, his motivation and control for a positive take of treatment.