Etiology
Chronic respiratory failure is mostly caused by bronchial and pulmonary diseases such as chronic obstructive pulmonary disease (COPD), severe pulmonary tuberculosis, interstitial lung fibrosis, and pneumoconiosis. Thoracic and neuromuscular disorders, such as chest surgery, trauma, extensive pleural thickening, thoracic deformities, and amyotrophic lateral sclerosis, can also lead to chronic respiratory failure.
Clinical manifestations
The clinical manifestations of chronic respiratory failure are similar to those of acute respiratory failure but differ in the following aspects:
Dyspnea
In dyspnea caused by COPD, mild cases show labored breathing with prolonged expiration, while severe cases develop into tachypnea. If CO2 retention occurs and PaCO2 rises rapidly or significantly, leading to CO2 narcosis, patients may shift from tachypnea to shallow, slow breathing or Cheyne-Stokes respiration.
Neurological symptoms
In chronic respiratory failure with CO2 retention, increasing PaCO2 can initially cause excitation followed by suppression. Excitation symptoms include insomnia, irritability, agitation, and day-night reversal. Sedatives or hypnotics should be contraindicated to prevent exacerbating CO2 retention and triggering pulmonary encephalopathy. Pulmonary encephalopathy is characterized by apathy, muscle tremors or asterixis, intermittent convulsions, drowsiness, and even coma, as well as reduced or absent tendon reflexes and positive pyramidal signs. It should be distinguished from concurrent cerebral lesions.
Circulatory system manifestations
CO2 retention can cause peripheral venous distension, skin hyperemia, warmth, diaphoresis, hypertension, and increased cardiac output, leading to bounding pulse. Most patients experience tachycardia, and pulsatile headaches may occur due to cerebral vasodilation.
Diagnosis
The diagnostic criteria for chronic respiratory failure in blood gas analysis are similar to those for acute respiratory failure. However, in clinical practice, Type II respiratory failure is often seen in the settings of PaO2 > 60 mmHg but PaCO2 above normal levels after oxygen therapy.
Treatment
The treatment principles, such as addressing the primary disease, maintaining airway patency, and appropriate oxygen therapy, are essentially the same as for acute respiratory failure.
Oxygen therapy
COPD is a common respiratory disease leading to chronic respiratory failure, often accompanied by CO2 retention. Oxygen therapy should be administered with low-concentration oxygen to prevent excessive blood oxygen levels. CO2 retention results from poor ventilation. In patients with chronic hypercapnia, the chemoreceptors in the respiratory center have a reduced response to CO2, and breathing is mainly maintained by hypoxemia stimulating the carotid and aortic body chemoreceptors. High-concentration oxygen intake can rapidly increase blood oxygen, removing the hypoxic stimulus to peripheral chemoreceptors, inhibiting breathing, deteriorating ventilation, increasing CO2 levels, and potentially leading to CO2 narcosis.
Positive pressure mechanical ventilation
Depending on the condition, noninvasive or invasive mechanical ventilation can be chosen. Early use of noninvasive mechanical ventilation during acute exacerbations of COPD can prevent exacerbations of respiratory insufficiency, relieve respiratory muscle fatigue, reduce the need for later intubation, and improve prognosis.
Anti-infection
Infection is a common trigger for acute exacerbations of chronic respiratory failure, and respiratory failure induced by non-infectious factors can also easily lead to secondary infections.
Correction of acid-base imbalance
Chronic respiratory failure is often accompanied by CO2 retention, leading to respiratory acidosis. This condition usually develops chronically, with the body compensating by increasing base reserves to maintain a relatively normal pH. Rapid correction of respiratory acidosis with methods like mechanical ventilation can cause the already increased base reserves to raise the pH, potentially harming the body. Therefore, the correction speed of respiratory acidosis should be monitored, aiming to quickly restore pH to normal and PaCO2 to baseline levels.
The treatment of primary disease and management of complications in chronic respiratory failure are similar to those in acute respiratory failure.
Long-term management
Chronic respiratory failure is generally incurable, and patients often require long-term home oxygen therapy and/or home mechanical ventilation after discharge. This requires oxygen tanks, oxygen concentrators, ventilators, respiratory circuits, masks, and other consumables at home. The use and maintenance of these devices and materials are highly specialized and should be handled by professional medical personnel, as misuse could pose life-threatening risks to patients. These patients experience rapid changes in condition, numerous mechanical ventilation complications, and frequent patient-ventilator asynchrony. Additionally, patients with chronic respiratory failure have limited mobility and require regular home visits by professionals for airway maintenance and management, medication guidance, rehabilitation training, psychological support, and smoking cessation education.