Chronic respiratory failure is a secondary syndrome that occurs when the respiratory system is unable to maintain gas homeostasis, which leads to a decrease in RaO2 and an increase in RaSO2 in arterial blood. It develops over a number of years; it is manifested by signs of dyspnea (shortness of breath), hypoxemia and hypercapnia (cyanosis, tachycardia, effects from the central nervous system), weakness of the respiratory muscles (changes in RR, participation of auxiliary muscles). Blood gas analysis, FER tests, pulse oximetry helps to assess the degree of chronic respiratory failure. Therapy includes correction of causal factors, the appointment of bronchodilators, mucoregulators, long-term O2 therapy. The issue of lung transplantation is being decided on an individual basis.
J96.1 Chronic respiratory failure
Chronic respiratory failure (CRF) is a symptom complex caused by the inability of the respiratory system to provide an adequate ratio of arterial blood gases. It is characterized by gradual development against the background of the progression of the underlying disease. With exacerbations of causally significant pathology, it may acquire signs of acute respiratory failure.
According to approximate data, the number of people suffering from chronic respiratory failure and requiring long-term oxygen therapy or home ventilation in economically developed countries is 0.08-0.1%. CRF is characterized by the following features: development over several months or years; gradual onset and progressive course. The solution of clinical issues related to chronic respiratory failure is mainly in the competence of clinical pulmonology and resuscitation.
Causes of chronic respiratory failure
The most common causal factors that cause the occurrence of chronic respiratory failure are bronchopulmonary diseases. These include:
- obstructive sleep apnea;
- smoker’s bronchitis and other forms of chronic bronchitis;
- bronchiectatic disease;
- bronchial asthma;
- COPD, interstitial lung diseases;
- cystic fibrosis;
- emphysema, pneumosclerosis;
- late stages of pulmonary hypertension.
Chest diseases that limit the depth of inspiration can lead to CRF (kyphoscoliosis, fibrothorax, the consequences of thoracoplasty, obesity, etc.). Among other things, chronic respiratory failure can be a consequence of damage to the neuromuscular apparatus in Duchenne muscular dystrophy, ALS, polio, paralysis of the diaphragm, spinal injuries. Possible causes of CRF also include anemia, congenital heart defects, hypothyroidism, incomplete recovery after an episode of ARF.
The main pathophysiological mechanisms of the formation of chronic respiratory failure are alveolar hypoventilation, ventilation-perfusion imbalance, violation of the diffusion of gases through the alveolar-capillary membrane. The consequence of these processes is the development of hypercapnia and hypoxemia, in response to which the body triggers a number of compensatory reactions designed to ensure the transport of O2 to tissues.
On the part of the cardiovascular system, tachycardia and an increase in cardiac output are noted. In response to alveolar hypoxia, pulmonary vasoconstriction occurs, accompanied by an improvement in ventilation-perfusion relations. Erythrocytosis develops in the blood, which increases the oxygen capacity of the blood. However, along with positive effects, compensatory mechanisms also play a negative role. All of these adaptive reactions eventually lead to the formation of pulmonary hypertension, pulmonary heart disease and heart failure.
Taking into account the differences in pathogenesis, there are two types of CRF: hypoxemic (pulmonary, parenchymal, type I RF) and hypercapnic (ventilation, type II RF).
Hypoxemic. The criteria for type I RF are hypoxemia in combination with hypo- or normocapnia. This type of chronic respiratory failure is formed against the background of diseases accompanied by damage to the pulmonary parenchyma (alveolitis, pneumoconiosis, lung sarcoidosis, etc.).
Hypercapnic. Type II RF is characterized by hypercapnia and hypoxemia (the latter lends itself well to oxygen therapy). The causes of ventilation respiratory failure may be COPD, respiratory muscle damage, decreased activity of the respiratory center, etc.
According to the type of respiratory disorders, chronic respiratory failure is classified into obstructive, restrictive and mixed. In the obstructive form, there is a decrease in the Tiffno index, flow values, an increase in bronchial resistance and pulmonary volumes. Restrictive syndrome is characterized by a decrease in VCL<80% and pulmonary volumes with a normal Tiffno index. With a combination of obstructive and restrictive disorders, they speak of a mixed form of RF.
The severity of chronic respiratory failure is estimated based on gasometric indicators:
- HDN I st. – RaSO2 <50 mm Hg., RaO2 >70 mm Hg.
- HDN II st. – RaSO2 50-70 mm Hg.; RaO2 70-50 mm Hg.
- HDN III st. – RaSO2 >70 mm Hg., RaO2 <50 mm Hg.
Hypercapnic coma occurs when RaSO2 increases to 90-130 mmHg, hypocapnic coma occurs when RaO2 decreases to 39-30 mmHg.
Symptoms of chronic respiratory failure
The clinical course of chronic respiratory failure depends on the underlying pathology, type and severity of RF. Its most typical manifestations are dyspnea, the effects of hypoxemia/hypercapnia and dysfunction of the respiratory muscles.
The earliest and universal symptom of CRF is dyspnea, or shortness of breath. Subjectively, this is perceived by patients as a feeling of lack of air, discomfort when breathing, the need to make a breathing effort, etc. With obstructive RF, shortness of breath is expiratory (exhalation is difficult), with restrictive – inspiratory (inhalation is difficult). Shortness of breath with physical exertion for many years can serve as the only sign of chronic respiratory failure.
The main clinical sign indicating hypoxemia is cyanosis. Its severity and prevalence indicates the severity of chronic respiratory failure. So, if in the subcompensated stage only cyanosis of the lips and nail beds is noted in patients, then in the decompensation stage it takes on a widespread, and in the terminal stage it takes on a generalized character. Hemodynamic changes in hypoxemia include tachycardia, arterial hypotension. When RaO2 decreases to 30 mmHg, syncopal episodes occur.
Hypercapnia in chronic respiratory failure is accompanied by an increase in heart rate, disorders of the central nervous system (night insomnia and daytime drowsiness, headache). Signs of respiratory musculature dysfunction are changes in RR and respiratory pattern. In most cases, chronic respiratory failure is accompanied by increased breathing (tachypnea). RR reduction to 12 v min. and less serves as a formidable harbinger, indicating the possibility of respiratory arrest. Altered breathing patterns include the involvement of additional muscle groups that are not normally involved in breathing (inflating the wings of the nose, neck muscle tension, participation in exhalation of abdominal muscles), paradoxical breathing, thoracoabdominal asynchrony.
The clinical classification of respiratory failure provides for the allocation of its four stages.
- I (initial) – carries a latent course, masking the symptoms of the underlying disease. Feelings of lack of air and increased breathing occur with physical effort.
- II (subcompensated) – shortness of breath occurs at rest, the patient constantly complains of lack of air, experiences a feeling of anxiety and anxiety. Additional muscles are involved in the act of breathing, cyanosis of the lips and fingertips takes place.
- III (decompensated) – shortness of breath is pronounced and causes the patient to take a forced position. Auxiliary muscles are involved in breathing, there is widespread cyanosis, psychomotor agitation.
- IV (terminal) – characterized by depression of consciousness, diffuse cyanosis, superficial arrhythmic breathing, bradycardia, arterial hypotension, oligoanuria. It can go into a hypoxemic or hypercapnic coma.
The algorithm of examination of patients with chronic respiratory failure involves an assessment of the physical status, a study of laboratory blood parameters and respiratory mechanics. In all cases, patients should be examined by a pulmonologist (if necessary, by other specialists: a therapist, cardiologist, neurologist, etc.) to identify the underlying disease. To assess changes in the lung tissue, lung x-ray is performed.
Analysis of the gas composition of the blood allows you to assess the degree of CRF based on the most important indicators: RaO2 RaSO2, pH and bicarbonate levels. Dynamic study of arterial blood gases plays an important role, not only during the day, but also at night. Pulse oximetry is used for noninvasive measurement of arterial oxygen saturation (SpO2).
In order to assess the severity and type of CRF, monitoring the patient’s condition, FER tests are carried out (measurement of VCL, forced exhalation, Tiffno index, MOD, etc.). To assess the function of the respiratory muscles, inspiratory and expiratory pressure in the oral cavity is measured. Additional characteristics can be obtained during polysomnography.
Chronic respiratory failure treatment
Therapy of chronic respiratory failure involves simultaneous work in several directions. One of them is the correction of causally significant factors, i.e. the impact on the primary disease. On an outpatient basis, treatment is prescribed and monitored by a specialized specialist (pulmonologist, phthisiologist, occupational pathologist, therapist). Hospitalization of patients with chronic respiratory failure is carried out only in case of exacerbation of the underlying pathology or with decompensation of RF. Adequate etiotropic therapy can restrain the progression of CRF for a long time and even lead to a decrease in its severity.
- Drug therapy. Since bronchial obstruction is often the basis of chronic respiratory failure, bronchodilators (theophylline, salbutamol, phenoterol), mucoregulators (ambroxol, acetylcysteine) are widely used. Caution should be taken when prescribing sleeping pills and sedatives to such patients, since they can reduce the activity of the respiratory center.
- Methods of physical rehabilitation. Work in the direction of respiratory rehabilitation involves physical therapy with the inclusion of breathing exercises, vibration and percussion chest massage, halotherapy, physiotherapy.
- Oxygen therapy. Chronic respiratory failure, accompanied by persistent hypoxemia, is the basis for the use of long-term oxygen therapy (LTOT). The procedure involves inhalation of a gas mixture containing up to 95% oxygen for 15-18 or more hours a day. The duration of the oxygen therapy course is determined based on the indicators of blood saturation and oxygen partial pressure. LTOT makes it possible to increase the effectiveness of pharmacotherapy and physical performance of patients, reduce the number of hospitalizations, and increase the life expectancy of patients with CRF by 5-10 years. LTOT can be performed even at home using portable oxygen sources.
- SIPAP therapy. Ventilator with constant positive pressure is used for the treatment of patients with chronic respiratory failure caused by tracheomalacia, sleep apnea syndrome, because it prevents the collapse of the respiratory tract. Patients with increasing hypercapnia need long-term home ventilation (LTHV), which can be both non-invasive (mask) and invasive (through a tracheostomy).
- Lung transplantation. With CRF caused by COPD, cystic fibrosis of the lungs, interstitial pulmonary fibrosis, etc., the question of the feasibility of lung transplantation is being resolved.
Prognosis and prevention
The long-term prognosis for chronic respiratory failure is unsatisfactory. With a decrease in RaO2 to 60 mmHg, the survival rate of patients is about 3 years. Timely and rational CRF therapy can improve the prognosis. Preventive work is reduced to the prevention and prevention of complicated course of primary diseases.