Acute respiratory failure

Acute respiratory failure is a condition characterized by a violation of the normal gas composition of the arterial blood: the delivery of a sufficient amount of oxygen to the arterial blood and the removal of an appropriate amount of carbon dioxide from the venous blood into the alveoli. Violation of pulmonary gas exchange leads to a decrease of p _and O ₂ (hypoxemia) and p increase _and CO ₂ (hypercapnia). Diagnostic criteria of acute respiratory failure - reducing p _and O ₂ is below 50 mm Hg and / or p _a CO _{2 is} greater than 50 mm Hg. In the absence of intracardiac shunting. However, even with normal blood gas composition indicators, acute respiratory failure may develop due to the exertion of the external respiration apparatus; The diagnosis in such cases is made only on the basis of clinical data. Respiratory failure is a syndrome characteristic of various diseases. Certain anatomical and physiological features of the respiratory organs in children predispose to the emergence of acute respiratory failure syndrome.

Anatomical and physiological features of the respiratory system in children:

• "Expiratory" structure of the chest;
• low absolute values of the respiratory volume and "dead space";
• physiological tachypnea;
• narrow airways;
• weakness of the respiratory muscles;
• relatively less surfactant activity.

Three types of acute respiratory failure:

• hypoxemic;
• hypercapnic;
• mixed.

Hypoxemic (shunt-diffusion) acute respiratory failure - low blood oxygenation at relatively adequate ventilation: low p _and O ₂ in combination with normal or somewhat reduced p _and CO ₂. The main feature is the violation of alveolar-capillary perfusion with intrapulmonary shunting of the blood without altering the alveolar ventilation. Alveolar-capillary difference in oxygen is increased.

Hypercapnic (ventilation) acute respiratory failure - reduction of p _and O ₂ with increasing p _and CO ₂ from primary hyperventilation, followed by a sharp decrease in volume ventilation and marked hypercapnia. The basis is a pathological increase in ventilation-perfusion relations with sharp alveolar hypoventilation.

Mixed acute respiratory failure is manifested by hyperventilation, an increase in alveolar-capillary difference. Hypoxemia is less pronounced than with hypoxemic acute respiratory failure.

Pathophysiological mechanisms of acute respiratory failure.

• Insufficient ventilation.
• Violation of ventilation-perfusion relations.
• Intra-pulmonary right-left shunting.
• Disturbance of alveolar-capillary diffusion.

In pediatric practice, the most frequent violation of ventilation-perfusion relations, rarely - violation of alveolar-capillary diffusion.

For each age, its most common causes of acute respiratory failure are characteristic. Among newborns, acute respiratory failure is more often observed in premature infants and children with congenital heart and lung defects. In children aged 1 to 2 years, the most common causes of acute respiratory failure are respiratory infections and heart diseases, in children 7-12 years of age - bronchial asthma.

[1], [2], [3],

Emergency help for acute respiratory failure

Acute subcompensated and decompensated stenosis of the larynx, often caused by mechanical trauma, is a critical condition that, if not adequately provided with emergency care, can lead to fatal consequences. As a rule, the problems arising in the performance of a therapeutic action aimed at restoring the patency of the upper respiratory tract, most often occur in conditions that are not suited to emergency care, that is, at the prehospital stage.

According to the Bureau of Forensic Medical Examination of St. Petersburg, for 1995-1997. From mechanical asphyxiation, 4474 people died, which amounted to more than 20% of the total number of violent deaths. Directly from aspiration of foreign bodies, the fatal outcome for three years occurred in 252 patients, which amounted to approximately 6% of the total number of asphyxia caused by mechanical factors.

One of the possible causes of breathing disorders in victims with mechanical trauma can be tongue lagging due to coma, medication sleep and other causes. To ensure airway patency in this case, it is necessary to perform Safar techniques:

• Extension of the head (performed with caution, since injury may damage the cervical spine);
• traction of the mandible anteriorly and upward;
• turn of the head.

If these simple techniques do not fully restore the patency of the airways, then with sufficient depth of anesthesia, the victim is provided with an oropharyngeal air duct with a rigid mouthpiece.

Often, the cause of acute respiratory failure, resulting from mechanical damage, is aspiration syndrome. The leakage of acidic gastric contents into the tracheobronchial tree represents a real threat to the lives of victims with a shock injury. Emergency measures for the prevention of aspiration are; probing the stomach, performing Selik's reception - giving the head of the victim an elevated position, carefully removing the contents from the oral cavity, and, finally, a quickly performed intubation. The latter allows, firstly, to protect the airways from re-entering the contents of the oral cavity in them, and secondly, it creates favorable conditions for carrying out artificial ventilation of the lungs and sanitation of the tracheobronchial tree.

When blood, liquor and gastric juice flow into the trachea and bronchi, they are washed with a 1% soda solution and, if possible, complete removal of the wash solution from the lungs (sanation bronchoscopy) followed by the introduction of antibiotics and glucocorticoid hormones into the tracheobronchial tree.

In those rare cases when intubation of the trachea for some reason fails (traumatic deformation of the cartilage of the larynx, difficulty in identifying the location of the glottis due to pronounced edema, anatomical features, etc.), it is necessary to resort to emergency cone-tracheostomy, which conditions of shortage of time are most conveniently made with the aid of a device for conical tracheostomy. It is a thin-walled cannula bent at an angle of 90 0 with an internal diameter of at least 4 mm and a mandril located in its lumen, the double-edged end of which extends beyond the cannula by 8-10 mm.

As can be seen, even small diameter cannulas used in children's practice may be suitable for restoring the patency of the upper respiratory tract in situations that are considered resuscitative. A valid choice of the diameter of the cannula is crucial to ensure adequate spontaneous as well as forced ventilation, and should be as minimal and least traumatic as possible for conical tracheocentesis. The universal kit for conical tracheostomy consists of five instruments of different diameters (from 2 to 8 mm) placed in a container in which the abacterial medium is maintained.

Conicotracheotomes are located in a container around the circumference on special support areas, which perform protective functions and allow long-term preservation of the cutting properties of the lancet-shaped mandril tip. The container is hermetically sealed with a lid with a fastener, which ensures the sterility of the device in the transport state. The reliability of this part of the device is extremely important for maintaining the integrity of the tool during transportation.

Influence of internal diameter on the value of gas mixture pressure on inspiration

Diameter of the cannula, mm	Pressure on inspiration, cm of water. Art.
2	20-22
4	10-12
6th	5-6
8	3-4

The technique of the puncture of the conical ligament or the inter-ring gap is simple, and all manipulation takes a few seconds. The sequence of actions is as follows: after processing the puncture site with an antiseptic solution, the trachea is fixed between the first and second fingers of the left hand. Then, a notch in the skin in the longitudinal direction of about 4-5 mm in length is made and the puncture of the trachea is performed strictly along the median line with the mandrel perforator inserted into the cannula (the instrument in the assembled state). After penetration of the tip of the perforator into the lumen of the trachea, a sensation of "failure" appears and then as the tool moves, when the "entrance" part of the mandrel and the cannula are in the lumen of the trachea, the mandrone is removed.

The control of the correct position of the cannula is the appearance of sound caused by the flow of air when the mandrel is extracted from it. Then the cannula moves forward (already without the mandrel with a perforator) to the end of the flange to the surface of the neck, after which it is fixed with a bandage or an adhesive patch.

A set of conicotracheotomes extends the capabilities of the caregiver by allowing the ventilator to be enlarged by sequential use of devices of different diameters, using conicotomes of each subsequent size as a dilator.

The use of the device with acute obstruction of the upper respiratory tract has significant advantages over the operation of tracheostomy, especially in conditions not adapted for its implementation (prehospital stage).

[4], [5], [6], [7], [8]

Support breathing in patients with restored airway patency

The choice of the method of respiratory therapy for patients with restored upper respiratory passages, suffering from hypoxic hypoxia, depends on many factors, the main of which are:

• degree of breathing disorders;
• presence of other types of damage;
• conditions for emergency assistance;
• qualification of medical personnel;
• equipped with respiratory equipment.

Along with the traditional methods of correcting hypoxic hypoxia, high-frequency ventilation (high-frequency ventilation) can be used. Its introduction into the practice of providing emergency medical care has significantly increased the effectiveness of resuscitation at the prehospital stage, that is, in the most difficult and naive conditions adapted to provide qualified care.

A significant obstacle in the spread of this type of artificial ventilation is the lack of serially produced devices, whose design requires requirements that take into account the working conditions and the amount of assistance at the prehospital stage. The device should be simple in operation, compact enough, have a universal power source and a low oxygen consumption.

The results of the gas analysis of arterial blood testify to the normalization of the voltage of carbon dioxide and a significantly greater increase in the oxygen tension (more than 1.5 times) with HF IVL in comparison with the traditional method. Proceeding from this, the prospects for using the HF IVL method in providing emergency care at the prehospital stage consist in the adequate elimination of hypoxemia and thereby creating favorable conditions for the restoration and normalization of heart function during resuscitation.

Correction of breathing disorders with thoracic trauma

The most severe components of thoracic trauma (according to their clinical course) are bruises and lung ruptures, which are often accompanied by pneumo- and hemothorax. Tense pneumothorax is especially dangerous for life due to an increase in intrapleural pressure, which leads not only to compression of the lung, but also to the displacement of the mediastinal organs with the subsequent rapid development of pulmonary heart failure.

If it is necessary to transfer the victim to artificial respiratory apparatus (according to vital indications) and the presence of hectic pneumothorax, the first-line emergency measure according to the Belau method is the drainage of the pleural cavity in the second intercostal space along the sredneklyuchichnoy line with a needle with a valve or plastic tube, the free end of which is immersed in a vessel with a liquid. The procedure for draining the pleural cavity with a strained pneumothorax should be made regardless of the nature of the ventilation, but always before or simultaneously with the onset of mechanical ventilation.

Expressed respiratory disorders are also characteristic of open pneumothorax. In this case, the severity of the course of the trauma is determined by the rapidly growing hypoxemia, which develops as a result of gas exchange disturbances, mainly in the collapsed lung. The difference in intrapleural pressure, which occurs during the act of breathing, leads to the flotation of the mediastinum and the movement of air from the asleep lung into the functioning by inhalation and in the opposite direction - on exhalation.

The disturbances that arise in these cases require an urgent drainage of the pleural cavity by two drains in the second and sixth intercostal spaces, respectively - along the midclavicular and back axillary lines, followed by active aspiration until the collapsed lung is fully expanded and respiratory therapy is performed.

A frequent cause of development of post-traumatic respiratory failure with closed chest trauma are multiple fractures of the ribs and sternum. Violations of the carcass of the chest lead to significant changes in the biomechanics of the act of breathing, limiting the mobility of the chest, and as a result - to gas exchange disorders, manifested in rapidly increasing hypoxemia. That is why the restoration of the broken thoracic cage is one of the most important medical measures aimed at correction of gas exchange disorders and normalization of ventilation-perfusion ratios in the lungs. One of the effective ways to eliminate the rib valve is extramedullary osteosynthesis.

[9], [10]

Epidural and retropleural anesthesia in patients with thoracic trauma

The severity of the condition of the victims with a thoracic trauma is exacerbated by a pronounced pain syndrome, which significantly disturbs the ventilation-perfusion relationships in the lungs. It is especially difficult to bear the pain that occurs in the victims with multiple fractures of the ribs and pleural injuries.

For the relief of pain syndrome, various analgesics and their combinations with sedatives are traditionally used, as well as various types of blockades. With fractures of 1-2 ribs, it is advisable to use intercostal blockades, and in patients with multiple fractures of ribs - epidural blockades that provide effective anesthesia and contribute to the normalization of ventilation-perfusion ratios in the lungs. However, anesthesia performed in the early period of traumatic disease (against the background of infusion therapy and stabilization of hemodynamic parameters) can not be considered safe in connection with the likely development of arterial hypotension, which can be caused by relative hypovolemia, even in cases when the dose of local anesthetic is selected strictly individually taking into account the severity of the patient's condition.

A good therapeutic effect under these conditions is retropleural anesthesia (RPA). As with epidural anesthesia, an anesthetic injected into the retropleural space affects the sensory and motor roots of the spinal cord, as well as the sympathetic ganglia, thus exerting a beneficial effect on the function of external respiration, without significantly altering the indices of systemic hemodynamics.

The active introduction into practice of intensive care of this type of conductive anesthesia was determined not only by its good analgesic effect and rather simple technique of performance, but also by the minimum number of complications, the risk of which is very significant in victims with shock.

The use of retropleural anesthesia as a method of anesthesia with closed combined trauma of the breast has an obvious clinical effect, which consists in less pronounced but quite sufficient analgesia and milder hemodynamic action compared with epidural blockade, which undoubtedly indicates the priority of this method in the treatment injured with a shock injury.

In clinical situations, in which (despite restoration of the thoracic cage, complete analgesia and rational oxygen therapy), the phenomena of respiratory failure continue to increase, it is necessary to resort to prolonged artificial ventilation as an unavoidable means of stabilizing the rib cage.

[11], [12], [13], [14], [15], [16]