Acute respiratory failure (ARF) is a pathological syndrome characterized by a sharp decrease in the level of blood oxygenation. It refers to life-threatening, critical conditions that can lead to death. Early signs of disease are: tachypnea, suffocation, feeling of lack of air, agitation, cyanosis. As hypoxia progresses, a violation of consciousness develops, convulsions, hypoxic coma. The fact of the presence and severity of respiratory disorders is determined by the gas composition of the blood. First aid consists in eliminating the cause of ARF, conducting oxygen therapy, if necessary, ventilator.
J96.0 Acute respiratory failure
Acute respiratory failure is a syndrome of respiratory disorders accompanied by arterial hypoxemia and hypercapnia. Diagnostic criteria are indicators of partial pressure of oxygen in the blood (pO2) < 50 mmHg, and partial pressure of carbon dioxide (pCO2) > 50 mmHg. In contrast to chronic respiratory failure, with ARF, the compensatory mechanisms of respiration, even at maximum stress, cannot maintain the optimal gas composition of the blood for vital activity and are rapidly depleted, which is accompanied by pronounced metabolic disorders of vital organs and hemodynamic disorders. Death from acute respiratory failure can occur within a few minutes or hours, so this condition is among the urgent ones.
Causes of acute respiratory failure
Etiological factors of acute respiratory failure are very diverse, therefore, doctors working in the departments of intensive care, pulmonology, traumatology, cardiology, toxicology, infectious diseases, etc. can face this condition in their practice. Depending on the leading pathogenetic mechanisms and the immediate causes, primary acute respiratory insufficiency of centrogenic, neuromuscular, thoraco-diaphragmatic and bronchopulmonary origin is distinguished.
At the heart of ARF of the central genesis is the suppression of the activity of the respiratory center, which, in turn, can be caused by poisoning (overdose of drugs, tranquilizers, barbiturates, morphine, etc. drugs), TBI, electrotrauma, cerebral edema, stroke, compression of the corresponding area of the brain by a tumor.
Violation of neuromuscular conduction leads to paralysis of the respiratory muscles and can cause acute respiratory failure in botulism, tetanus, polio, overdose of muscle relaxants, myasthenia gravis. Thoracophrenic and parietal ARF are associated with limited mobility of the chest, lungs, pleura, diaphragm. Acute respiratory disorders can accompany pneumothorax, hemothorax, exudative pleurisy, chest injuries, rib fractures, posture disorders.
The most extensive pathogenetic group is bronchopulmonary acute respiratory failure. ARF of the obstructive type develops due to a violation of the patency of the respiratory tract at various levels. The cause of obstruction may be foreign bodies of the trachea and bronchi, laryngospasm, status asthmaticus, bronchitis with hypersecretion of mucus, strangulation asphyxia, etc. Restrictive ARF occurs in pathological processes accompanied by a decrease in the elasticity of the lung tissue (caseous pneumonia, hematomas, lung atelectasis, drowning, conditions after extensive lung resections, etc.). The diffuse form of acute respiratory failure is due to a significant thickening of the alveolo-capillary membranes and, consequently, difficulty in oxygen diffusion. Such a mechanism of respiratory failure is more typical for chronic lung diseases (pneumoconiosis, pneumosclerosis, diffuse fibrosing alveolitis, etc. However, it can also develop acutely, for example, with respiratory distress syndrome or toxic lesions.
Secondary form occurs due to lesions that do not directly affect the central and peripheral organs of the respiratory apparatus. Thus, acute respiratory disorders develop with massive bleeding, anemia, hypovolemic shock, arterial hypotension, PE, heart failure and other conditions.
The etiological classification divides ARF into primary (due to a violation of the mechanisms of gas exchange in the lungs – external respiration) and secondary (due to a violation of oxygen transport to tissues – tissue and cellular respiration).
Primary acute respiratory failure:
- pleurogenic or thoraco-diaphragmatic
- bronchopulmonary (obstructive, restrictive and diffuse)
Secondary acute respiratory failure caused by:
- hypocirculatory disorders
- hypovolemic disorders
- cardiogenic causes
- thromboembolic complications
- by shunting (depositing) of blood in various shock conditions
These forms of acute respiratory failure will be discussed in detail in the section “Causes”.
In addition, there are ventilation (hypercapnic) and parenchymal (hypoxemic) acute respiratory failure. Ventilation DN develops as a result of a decrease in alveolar ventilation, accompanied by a significant increase in pCO2, arterial hypoxemia, respiratory acidosis. As a rule, it occurs against the background of central, neuromuscular and thoraco-diaphragmatic disorders. Parenchymal DN is characterized by arterial hypoxemia; at the same time, the level of CO2 in the blood may be normal or slightly elevated. This type of acute respiratory failure is a consequence of bronchopulmonary pathology.
Depending on the partial voltage of O2 and CO2 in the blood , there are three stages of acute respiratory disorders:
- ARF stage I – pO2 decreases to 70 mmHg, pCO2 to 35 mmHg
- ARF stage II – pO2 decreases to 60 mmHg, pCO2 increases to 50 mmHg
- ARF stage III – pO2 decreases to 50 mmHg and below, pCO2 increases to 80-90 mmHg and above.
Symptoms of acute respiratory failure
The sequence, severity and rate of development of signs of acute respiratory failure may vary in each clinical case, however, for the convenience of assessing the severity of disorders, it is customary to distinguish three degrees of ARF (in accordance with the stages of hypoxemia and hypercapnia).
ARF of the I degree (compensated stage) is accompanied by a feeling of lack of air, anxiety of the patient, sometimes euphoria. The skin is pale, slightly moist; there is a slight cyanosis of the fingers, lips, and tip of the nose. Objectively: tachypnea (BH 25-30 per minute), tachycardia (HR 100-110 per minute), moderate increase in blood pressure.
With ARF II degree (stage of incomplete compensation), psychomotor agitation develops, patients complain of severe suffocation. Possible confusion, hallucinations, delirium. The color of the skin is cyanotic (sometimes with hyperemia), profuse sweating is observed. At the II stage of acute respiratory failure, BH continues to increase (up to 30-40 in 1 min.), pulse (up to 120-140 in min.); arterial hypertension.
ARF III degree (decompensation stage) is marked by the development of hypoxic coma and tonic-clonic seizures, indicating severe metabolic disorders of the central nervous system. The pupils dilate and do not react to light, a mottled cyanosis of the skin appears. BH reaches 40 or more per minute, respiratory movements are superficial. A formidable prognostic sign is the rapid transition of tachypnea to bradypnea (BH 8-10 per minute), which is a harbinger of cardiac arrest. Blood pressure drops critically, heart rate is over 140 per minute. with the phenomena of arrhythmia. Acute respiratory failure of the III degree, in fact, is the preagonal phase of the terminal state and without timely resuscitation leads to a rapid fatal outcome.
Often, the picture of acute respiratory failure unfolds so rapidly that it leaves almost no time for an extended diagnosis. In these cases, the doctor (pulmonologist, resuscitator, traumatologist, etc.) quickly assesses the clinical situation to find out the possible causes of ARF. When examining a patient, it is important to pay attention to the patency of the respiratory tract, the frequency and characteristics of breathing, the involvement of auxiliary muscles in the act of breathing, the color of the skin, heart rate. In order to assess the degree of hypoxemia and hypercapnia, the diagnostic minimum includes the determination of the gas composition and acid-base state of the blood.
If the patient’s condition allows (with ARF degree I), a study of FER (peak flowmetry, spirometry) is performed. To find out the causes of disease, chest x-ray, bronchoscopy, ECG, blood test, toxicological examination of urine and blood may be important.
Treatment of acute respiratory failure
The sequence of first aid measures is determined by the cause of acute respiratory failure, as well as its severity. The general algorithm includes provision and maintenance of airway patency, restoration of pulmonary ventilation and perfusion disorders, elimination of concomitant hemodynamic disorders.
At the first stage, it is necessary to examine the patient’s oral cavity, remove foreign bodies (if any), aspirate the contents from the respiratory tract, eliminate tongue entanglement. In order to ensure the patency of the respiratory tract, it may be necessary to apply a tracheostomy, conicotomy or tracheotomy, therapeutic bronchoscopy, postural drainage. With pneumothorax or hemothorax, the pleural cavity is drained; with bronchospasm, glucocorticosteroids and bronchodilators are used (systemically or inhaled). Then it is necessary to immediately ensure the supply of moistened oxygen (using a nasal catheter, mask, oxygen tent, hyperbaric oxygenation, ventilator).
In order to correct concomitant disorders caused by acute respiratory failure, drug therapy is carried out: analgesics are prescribed for pain syndrome; respiratory analeptics and cardiac glycosides are used to stimulate respiration and cardiovascular activity; infusion therapy is used to eliminate hypovolemia, intoxication, etc.
The consequences of acute respiratory failure are always serious. The prognosis is influenced by the etiology of the pathological condition, the degree of respiratory disorders, the speed of first aid, age, initial status. With rapidly developing critical disorders, death occurs as a result of respiratory arrest or cardiac activity. With less severe hypoxemia and hypercapnia, rapid elimination of the cause of acute respiratory failure, as a rule, a favorable outcome is observed. To exclude repeated episodes of ARF, intensive treatment of background pathology is necessary, which entailed life-threatening respiratory disorders.
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