Artificial ventilation of the lungs

Description:

Artificial ventilation of the lungs — provides gas exchange between air (or specially picked up mix of gases) and alveoluses of lungs.

Modern methods of the artificial ventilation of the lungs (AVL) can be divided conditionally on simple and hardware. Simple methods usually apply in emergency situations: in the absence of independent breath (apnoea), at sharply developed disturbance of a respiratory rhythm, its pathological rhythm, breath of agonal type: at breath increase more than 40 in 1 min. if it is not connected with a hyperthermia (body temperature higher than 38,5 °) or the expressed not eliminated hypovolemia; at the accruing anoxemia and (or) a hypercapnia if they do not disappear after anesthesia, recovery of passability of respiratory tracts, oxygen therapy, elimination of life-threatening level of a hypovolemia and gross violations of metabolism.

Expiratory ways IVL (artificial respiration) from a mouth in a mouth and from a mouth in a nose first of all belong to simple methods. At the same time the head of the patient or victim shall be in the provision of the maximum occipital extension for prevention of retraction of language and ensuring passability of respiratory tracts; the root of language and an epiglottis are displaced kpered and open an entrance to a throat. Giving help becomes sideways from the patient, one hand squeezes wings of his nose, rejecting the head back, other hand slightly slightly opens a mouth for a chin.

Having made a deep breath, it densely presses the lips to a mouth of the patient and does a sharp vigorous exhalation then takes the head aside. The exhalation of the patient occurs passively due to elasticity of lungs and a thorax. It is desirable that the mouth giving help was isolated by a gauze napkin or a piece of bandage, but not dense fabric. At IVL from a mouth in a nose air is blown into the nasal courses of the patient.

At the same time his mouth is closed, pressing a mandible to upper and trying to tighten a chin up. Inflation of air is carried out usually with a frequency of 20 — 25 of 1 min.; at IVL combination to a cardiac massage — with a frequency of 12 — 15 of 1 min. Carrying out simple IVL is considerably facilitated by introduction to an oral cavity of a sick S-shaped air duct, use of a bag of Ruben (Ambu, RDA-1) or RPA-1 furs through a mouth-nose mask. At the same time it is necessary to provide passability of respiratory tracts and to densely press a mask to a face of the patient.

Hardware methods (by means of special devices respirators) apply in need of long IVL (from several hours to several months and even years). The USSR is most extended by RO-6A in its modifications (RO-6N for an anesthesia and RO-6R for an intensive care), and also the simplified PO-6-03 model. The respirator "Phase-50" has great opportunities. For pediatric practice the office of Vit-1 is issued. The first domestic device for jet high-frequency IVL is the respirator of "Spiron-601".

The respirator is usually attached to respiratory tracts of the patient through an endotracheal tube or a tracheostomy cannula. More often hardware IVL is carried out in the normochastotny mode — 12 — 20 cycles in 1 min. Also IVL in the high-frequency mode enters practice (more than 60 cycles in 1 min.) at which respiratory volume considerably decreases (to 150 ml and less), decrease positive pressure in lungs at the end of a breath and intrathoracic pressure, inflow of blood to heart is less complicated. Besides, at IVL in the high-frequency mode accustoming (adaptation) of the patient to a respirator is facilitated.

There are three ways of high-frequency IVL (volume, oscillation and jet). Volume carry out usually with a respiration rate 80 — 100 in 1 min., oscillation — 600 — 3600 in 1 min., providing vibration continuous or discontinuous (in the normochastotny mode) a gas flow. The greatest distribution was gained by jet high-frequency IVL with a respiration rate 100 — 300 in 1 min. at which the stream of oxygen or gas mix under pressure of 2 — 4 atm is blown into respiratory tracts through a needle or a catheter with a diameter of 1 — 2 mm. Jet IVL can be carried out through an endotracheal tube or a tracheostoma (at the same time there is an injection — a podsasyvaniye of atmospheric air in respiratory tracts) and through the catheter entered into a trachea through the nasal course or chreskozhno (punktsionno). The last is especially important when there are no conditions for implementation of an intubation of a trachea or the medical staff has no skill of holding this procedure.

Artificial ventilation of the lungs can be carried out in the automatic mode when independent breath of the patient is completely suppressed by pharmacological drugs or specially picked up parameters of ventilation of the lungs. Perhaps also carrying out auxiliary IVL at which independent breath of the patient remains. Supply of gas is carried out after feeble attempt of the patient to make a breath (the trigger mode of auxiliary IVL), or the patient adapts to individually picked up operating mode of the device.

There is also a mode of the periodic forced ventilation of the lungs (PFVL) which is usually used in the course of gradual transition from IVL to independent breath. At the same time the patient breathes independently, but in respiratory tracts the continuous flow of the warmed-up and moistened gas mix creating iskotory positive pressure in lungs throughout all respiratory cycle moves. On this background with the set frequency (usually from 10 to 1 times in 1 min.) the respirator makes the artificial breath which is matching (synchronized PPVL) or not matching (not synchronized LLVL) with the next independent breath of the patient. Postepenioye to the urezheena of artificial breaths allows to prepare the patient for independent breath.

The IVL mode with positive pressure at the end of an exhalation (PDKV) from 5 to 15 cm w.g. was widely adopted. and more (according to special indications!), at which vnu-trilegochny pressure during all respiratory cycle remains positive in relation to atmospheric. This mode promotes the best distribution of air in lungs, to reduction of shunting of blood in them and to decrease in an alveolar and arterial difference on oxygen.

At artificial ventilation of the lungs with PDKV atelectases finish, the fluid lungs is eliminated or decreases that promotes improvement of oxygenation of an arterial blood at the same content of oxygen in the inhaled air. However at IVL with positive pressure at the end of a breath intrathoracic pressure significantly increases that can lead to difficulty of inflow of blood to heart.

Did not lose the value rather seldom used IVL method — electrostimulation of a diaphragm. Periodically irritating either phrenic nerves, or directly a diaphragm through outside or needle electrodes, it is possible to achieve its rhythmical reduction that provides a breath. To electrostimulation of a diaphragm resort as to a method of auxiliary IVL in the postoperative period more often, and also when training patients for operative measures.

At a modern anesthesiology grant of IVL carry out first of all due to the need of providing a muscular relaxation with kurarepodobny drugs. Against the background of IVL use of a number of analgetics in doses, sufficient for full-fledged anesthesia, which introduction in the conditions of independent breath would be followed by an arterial anoxemia is possible.

Supporting good oxygenation of blood, IVL helps an organism to cope with an operational injury. At a number of operative measures on bodies of a thorax (lungs, a gullet) use a separate intubation of bronchial tubes that allows to switch off during operation one lung from ventilation for simplification of work of the surgeon. Such intubation also warns flowing in a healthy lung of contents from operated. At operative measures on a throat and airways with success use the chreskateterny jet high-frequency IVL facilitating survey of a surgery field and allowing to support adequate gas exchange at the opened trachea and bronchial tubes.

Considering what in the conditions of the general anesthesia and a muscular relaxation of the patient cannot react to a hypoxia and hypoventilation, control of the maintenance of blood gases, in particular continuous monitoring of indicators of partial pressure of oxygen (ro2) and the partial pressure of carbon dioxide (rso2) by means of special sensors is in the transdermal way of particular importance. When carrying out the general anesthesia at the exhausted, weakened patients, especially with respiratory insufficiency before operation, at the expressed hypovolemia, development in the course of the general anesthesia of any complications promoting developing of a hypoxia (decrease in the ABP, a cardiac standstill, etc.), continuation of IVL within several hours after the end of surgery is shown. In case of clinical death or an agony of IVL is an obligatory component of a resuscitation grant. It is possible to stop it only after a complete recovery of consciousness and full independent breath.

In a complex of an intensive care of IVL is the most powerful tool of fight against acute respiratory insufficiency. Usually it will be out through a tube which is entered into a trachea through the lower nasal course or a tracheostoma. Careful care of respiratory tracts, their full drainage is of particular importance. At a fluid lungs, pneumonia, a distress syndrome respiratory adults artificial ventilation of the lungs with PDKV sometimes to 15 cm w.g. is shown. and more. If the anoxemia remains even at high PDKV, the combined use of traditional and jet high-frequency IVL is shown.

Auxiliary IVL is applied sessions up to 30 — 40 min. at treatment of patients with chronic respiratory insufficiency. It can be used in out-patient and polyclinic and even house conditions after the corresponding training of the patient.
IVL use at the patients who are in coma (an injury, brain operation) and also at peripheral damage of respiratory muscles (a polyradiculoneuritis, an injury of a spinal cord, a side amyotrophic sclerosis). In the latter case IVL should carry out it is very long — months and even years that demands especially careful nosotrophy. Widely use IVL and at treatment of patients with a thorax injury, a puerperal eclampsia, various poisonings, disturbances of cerebral circulation, tetanus, botulism.

Control of adequacy of IVL. When carrying out the emergency IVL by simple methods there is enough observation of skin color and movements of a thorax of the patient. The wall of a thorax has to rise at each breath and fall down at each exhalation. If instead the epigastric area rises, the blown air means comes not to respiratory tracts, and to a gullet and a stomach. The wrong position of the head of the patient happens the reason most often.

When carrying out long hardware IVL about its adequacy judge by a number of signs. If independent breath of the patient is not suppressed pharmacological, one of the main signs is good adaptation of the patient to a respirator. At clear consciousness the patient should have no feeling of shortage of air, discomfort.

Respiratory noise in lungs have to be identical on both sides, skin has usual coloring, dry. Signs of inadequacy of IVL are the accruing tachycardia, a tendency to arterial hypertension, and when using artificial ventilation with PDKV — to hypotension that is a sign of decrease in inflow of blood to heart. Control for ro2 is extremely important, rso2 and an acid-base condition of blood, ro2 in the course of IVL it is necessary to support not lower than 80 mm of mercury.

At heavy disturbances of a hemodynamics (massive blood loss, traumatic or cardiogenic shock) increase ro2 to 150 mm of mercury is desirable. above. rso2 it is necessary to support, changing the minute volume and a respiration rate, at the maximum level at which there occurs full adaptation of the patient to a respirator (usually 32 — 36 mm of mercury.). In the course of long IVL there should not come the metabolic acidosis or a metabolic alkalosis. The first most often demonstrates disturbances of peripheric circulation and microcirculation, the second — about a hypopotassemia and a cellular hydropenia.

Complications. At long IVL often there are tracheobronchitis, pneumonia; a dangerous complication is pheumothorax since in the conditions of IVL air quickly accumulates in a pleural cavity, squeezing a lung, and then and displacing a mediastinum. During IVL sliding of an endotracheal tube in one of bronchial tubes is possible (more often in right). Quite often it happens at transportation and movement of the patient.

In the course of IVL in a razduvny cuff of an endotracheal tube protrusion which covers an opening of a tube and interferes with carrying out IVL can be formed.

Features of artificial ventilation of the lungs in pediatrics. Children, especially early age, easily have laryngitis, hypostasis of a throat and other complications connected with an intubation. Therefore they are recommended to carry out a trachea intubation by a tube without razduvny cuff. The respiratory volume and a respiration rate are chosen according to age and body weight. At newborns establish a respiration rate 30 — 40 and more in 1 min. At asphyxia of newborns, the aspiration of meconium and disturbances of breath caused by cerebral palsy along with traditional simple and the IVL hardware methods with success use oscillation high-frequency IVL with a frequency of 600 and more in 1 min.

Features of artificial ventilation of the lungs in field conditions. In field conditions, and also at assistance to victims at accidents of peace time (the fires, earthquakes, accidents in mines, train accidents, plane crashes) carrying out IVL can be complicated by existence in different atmosphere of harmful impurity (toxic gases and products of burning, radioactive materials, biological agents, etc.). Giving help, being in a gas mask, an oxygen mask or a protective suit, cannot resort to IVL on a way from a mouth in a mouth or from a mouth in a nose. Even after removal of the defeat which was injured from a zone it is dangerous to use these ways since toxic or biological agents can already be in his lungs and get into airways of the rescuer.

Therefore manual devices for IVL — the self-finishing bags and furs are of particular importance. All of them as well as automatic respirators, have to be supplied with special filters deactivators for the prevention of hit in respiratory tracts of the patient of harmful impurity. The exception is made by drugs for jet high-frequency IVL if they have an autonomous source of the compressed gas and are used in the chreskateterny way (without air injection).