Ventilator complications are the negative consequences of artificial lung ventilation that occur immediately after its onset or are the result of prolonged respiratory support. The symptoms are determined by the type of disorders. Signs of respiratory failure, emphysema, inflammatory phenomena, changes in the work of internal organs may be detected. Pathology is diagnosed on the basis of the clinical picture and objective examination data: radiography, ultrasound, computer or magnetic resonance imaging, determination of blood pH. Specific treatment includes adjustment of equipment parameters, relief of inflammation, suturing of lung tissue damage, drainage of the thoracic cavity.
Ventilator complications with its proper implementation are relatively rare. Most often, patients who are in the ICU for a long time develop congestive pneumonia. Aspiration type of lung inflammation is sometimes diagnosed in patients who are supported by a non-invasive type (through a facial mask) for more than a day. If the mode is chosen incorrectly, gas acidosis or alkalosis of varying severity is detected in 100% of cases. Hardware respiration for 2-3 weeks or more potentiates the formation of pathological processes in internal organs. Barotrauma is the rarest type of complications, it occurs mainly in children and patients with asthenic physique.
As a rule, concomitant pathological conditions are the result of violation of the rules of ventilation. In the absence of such disorders, difficulties caused by inevitable changes in the body are detected in individual patients who are forced to stay on external life support for a long time. This happens with severe injuries, exo- or endotoxic damage to the respiratory center, croup pneumonia. Ventilator complications develop for the following reasons:
- High pressure on inspiration. Increased pressure provokes ruptures of the lung tissue, usually occurs at a reading above 50 mm Hg, however, it can also occur at lower numbers if ventilation is carried out to elderly patients or young children. The wrong choice of pressure is one of the reasons leading to the most severe malfunctions in the body.
- Violation of respiratory hygiene. Removal of mucus accumulated in the intubation or tracheostomy tube should be performed every 2-3 hours or as needed. If this rule is not followed, mucus containing bacterial strains accumulates in the trachea, bronchi, lungs, which increases the likelihood of infectious processes.
- Irregular control of the ABB. Determination of acid-base balance and electrolyte content in blood plasma is the main type of laboratory monitoring of the patient’s condition. According to its results, the pH of the internal environment is evaluated, the presence of acidosis or alkalosis is determined before the development of clinical manifestations, and the operating mode of the device is adjusted. In the absence of data from this study, it is impossible to diagnose ventilator complications at an early stage.
- Insufficient visual control. If the staff of the medical institution does not provide constant visual monitoring of the condition of the equipment and the patient, the risk increases that the patient will independently disconnect the respiratory circuit, remove the intubation tube, undergo hypoxia and die. Special attention is required for patients suffering from encephalopathy of any origin and who are in a post-acute state.
- Long-term hardware gas exchange. It leads to a gradual disorder of metabolic processes, maladaptation of the respiratory center, violation of the electrolyte balance. It is almost impossible to prevent such phenomena, since they are a natural reaction of the body to long-term hardware respiration and insufficient mobility.
The pathogenesis of ventilator complications is determined by their nature and causes. Infectious processes develop when a large amount of sputum containing pathogenic microorganisms accumulates in the alveoli and bronchi. The weakening of immunity due to the underlying pathology dramatically increases the likelihood of inflammation of the affected areas. Aspiration varieties of pneumonia are the result of incomplete expansion of the lung with insufficient volume of inspiration and prolonged lying position. At the same time, anaerobic flora develops rapidly in poorly ventilated areas.
Respiratory acidosis occurs when the level of oxygenation decreases and the partial pressure of carbon dioxide increases. The hemoglobin dissociation curve shifts to the right, the H+ concentration increases, and the pH shifts to the acidic side. The reverse process associated with hyperventilation, a decrease in pCO2 and H+ levels leads to the formation of gas-type alkalosis. In barotrauma, the pathogenesis is based on the mechanical rupture of lung tissues with the release of air and blood into the paropulmonary space and subcutaneous adipose tissue. The lung can be compressed by the spilled liquid and gas, which initiates its incomplete participation in the breathing process.
With independent disconnection from the equipment, the main problem is the lack of adequate gas exchange in the lungs and the development of hypoxia. Oxidative processes in cells are disrupted, carbon dioxide accumulates. The brain and myocardium experience oxygen starvation, culminating in the death of the patient. If the disconnection occurred due to the removal of the intubation tube, tracheal injuries occur. This provokes swelling and mechanical obstruction of the respiratory tract. It is not always possible to re-intubate patients, often the doctor has to resort to emergency tracheostomy.
All ventilator complications are considered severe and may threaten the patient’s life, so systematization by severity is not used. A classification can be applied according to the flow rate, according to which all conditions are divided into lightning-fast (independent extubation against the background of the absence of spontaneous breathing, barotrauma), acute (pneumonia), chronic (stress ulcers, edema). Such a principle of division is extremely conditional and has no clinical significance. In practice, specialists usually rely on systematization according to the pathogenetic principle:
- Barotrauma. Depending on the localization and size of the rupture, it can lead to the formation of interstitial emphysema, pneumomediastenum, subcutaneous emphysema, pneumothorax. The most dangerous is considered to be the valve variety of the latter, in which the air accumulated in the pleural cavity squeezes the lung and completely excludes it from the breathing process.
- Infectious complications. The main varieties are aspiration and stagnant pneumonia. They are characterized by a severe course, they do not respond well to therapy. Since the causative agent is nosocomial strains, antibiotic therapy is not always effective. The selection of drugs is carried out according to the results of sputum analysis for sensitivity to antimicrobial drugs. In addition, tracheitis, bronchitis, abscesses of the respiratory tract or lungs may occur.
- Violations of the ABB. In the compensated version (pH shift by hundredths) do not pose a threat to life. Subcompensated and decompensated forms lead to disruption of the structure of proteins, including hormones and receptors. The consequence is systemic failures in the work of all body systems, multiple organ failure.
- Pathomimia. Independent intervention of the patient in the process of lung ventilation, removal of the tube, disconnection of the circuit, disconnection of the device. Critically dangerous to life, should be stopped by medical personnel up to the soft fixation of the patient to the bed and the introduction of neuroleptic drugs to relieve psychomotor agitation.
- Exchange violations. Complications of ventilation that occur with prolonged support and lead to the formation of chronic pathological processes. They include cholestasis, edema, urolithiasis, stress ulcers of the stomach and duodenum. They remain for the entire period of artificial ventilation, require separate treatment after the restoration of independent breathing.
Barotrauma is manifested by sharp chest pain, signs of respiratory failure against the background of ongoing ventilation. The chest of the patient can visually increase in volume, take a barrel shape. The skin is cyanotic or pale, covered with sweat. During the formation of subcutaneous emphysema, palpation reveals a characteristic crunch that occurs due to air bubbles accumulated in the subcutaneous tissue. The device can work normally or signal a violation of the design parameters. With a large blood loss, tachycardia, hypotension, disorders of consciousness occur, in severe cases – coma.
Pneumonia is manifested by an increase in body temperature, a general deterioration in well-being, pain and aching in the muscles, hyperemia of the face on the side of inflammation, a feeling of lack of air. There may be hemodynamic disorders, the development of infectious and toxic shock. In weakened patients, clinical manifestations are poorly expressed, the picture is blurred. A large amount of fetid purulent sputum is separated through the intubation tube. Vomiting is possible. The patient is thirsty, drinks a lot, if the equipment allows it.
Clinical manifestations of ABB disorders and metabolic failures vary widely. The symptoms depend on the type and degree of damage to a particular organ. Most often there is anuria, diarrhea or constipation, the color of the stool changes, the skin becomes yellowish. Nausea and vomiting are noted. The patient refuses food, water. Tachyarrhythmia, bradycardia, extrasystole, and a decrease in blood pressure are detected. Signs of endotoxic encephalopathy are detected. Pathomimia, accompanied by the cessation of the supply of the respiratory mixture, leads to the appearance of signs of acute respiratory failure: cyanosis of the skin and lips, rare or completely absent breathing, depression of consciousness.
Diagnosis of ventilator complications is made by an anesthesiologist-resuscitator. Consultations of other specialists are required, in particular – a hepatologist, a pulmonologist, a cardiologist. In addition, X-ray examination, ultrasound, electrocardiography are performed on the patient in the ward. Measures to determine complications should be implemented in a short time, optimally – within 1-2 hours from the moment of onset of symptoms. Then they begin emergency therapy or transport the patient to the operating unit. Diagnostic measures include:
- Examination and physical examination. During the examination, pay attention to the clinical signs of respiratory failure, circulatory failure, kidney or liver function. With pneumothorax, percussion reveals tympanitis, the sound of a cracked pot, with emphysema – a box sound. With pneumonia, wheezing is heard in the lungs, breathing is not carried out in all departments. With self-extubation, symptoms of suffocation are noted.
- Laboratory examination. In the results of the analysis for ABB, an increase or decrease in pH, disturbances in the gas and electrolyte composition of the blood are determined. Usually, the more pronounced the laboratory changes, the more severe the patient’s condition is. In biochemical analysis, deviations from the norm occur with the development of systemic pathological processes. An increase in the activity of liver enzymes, an increase in the concentration of creatinine and urea is possible.
- Instrumental examination. In pneumonia, lung radiography allows you to identify foci of inflammation, which are visualized as areas of darkening. With ruptures of the lung, the displaced mediastinum, the collapse of the organ is visible. Respiratory tract injuries are detected during bronchoscopy. To clarify the diagnosis, computer tomography of the affected area is used.
Treatment of barotrauma is carried out by surgical methods. With pneumothorax, a puncture of the pleural cavity with the installation of drainage is indicated. Thoracocentesis is used to straighten the lung. Hemostatic drugs are indicated to stop bleeding. If minimally invasive treatment is ineffective, the patient is transported to the operating unit for thoracotomy and revision of the chest organs. The defect is sutured, coagulation is performed, accumulated exudate and blood are removed from the pleural cavity.
Complications of ventilation of an infectious nature require the appointment of antibacterial and mucolytic drugs that facilitate the discharge of sputum. It is permissible to use immunostimulating agents, bacteriophages. A prerequisite is timely sanitation of the trachea with the removal of separating sputum. It is possible to stimulate its withdrawal with the help of vibration massage, tapping in the area of the shoulder blades. If necessary, a therapeutic bronchoscopy is prescribed.
Correction of ABB disorders is performed by adjusting the breathing apparatus. With acidosis, the volume and frequency of inhalation increase, with alkalosis – decrease. Oxygenation by increasing the percentage of oxygen in the respiratory mixture to more than 40% is allowed only for a short time (no more than 5-10 minutes), otherwise the so-called oxygen intoxication occurs. Metabolic disorders during the patient’s stay in intensive care are eliminated asymptomatically. With edema, loop diuretics are administered, with functional cholestasis – choleretic drugs. Constipation requires the appointment of laxatives and a cleansing enema. In case of renal insufficiency, hemodialysis is indicated.
Prognosis and prevention
The prognosis of ventilator complications depends on the type and severity of the violation. In most cases, timely detected negative changes can be stopped without serious consequences. Prevention consists in the competent selection of ventilation modes, regular cleaning of the respiratory tract, early activation of the patient within the bed. Patients in a state of psychomotor agitation should be fixed to the bed, an alternative option for the resuscitator in such cases is the introduction of psychotropic drugs and hypnotics. When using artificial respiratory support, all patients require round-the-clock supervision by the nursing staff.