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Definition, Etiology, Pathogenesis Top
Chronic respiratory failure develops progressively and is usually punctuated by acute exacerbations that may or may not be fully reversible.
2) Chronic interstitial lung diseases, including idiopathic pulmonary fibrosis, sarcoidosis, pneumoconioses, postinfectious pulmonary fibrosis (eg, posttuberculosis or other pneumonias).
3) Primary and metastatic tumors of the respiratory system.
4) Chest deformities (eg, severe kyphoscoliosis).
5) Extreme obesity.
6) Neuromuscular diseases: Multiple sclerosis, Parkinson disease, chronic polyneuropathies, persistent posttraumatic damage of the phrenic nerves or the cervical or thoracic spinal cord, amyotrophic lateral sclerosis, chronic myopathies (muscular dystrophies).
7) Cardiovascular diseases: Chronic pulmonary embolism, cyanotic congenital heart disease, chronic congestive heart failure.
Clinical Features Top
1) Chronic progressive dyspnea on exertion or at rest with reduced exercise tolerance.
2) Somnolence and headache (in patients with hypercapnia).
3) Other symptoms of underlying conditions (eg, productive cough in COPD).
1) Signs of hypoxemia (tachypnea, tachycardia, cyanosis, clubbing of digits, symptoms of right ventricular failure (see Chronic Heart Failure).
2) Signs of increased accessory respiratory muscle use: Muscle hypertrophy, increased anteroposterior diameter of the chest and flattening of the diaphragms on chest radiograph (in COPD).
3) Vasodilatation due to hypercapnia: Conjunctival injection and skin erythema.
4) Signs of the underlying condition.
Diagnosis is based on the chronicity of signs, symptoms, and abnormalities on specific tests of pulmonary function (see Respiratory Failure). To determine the cause and severity, perform chest radiography, spirometry, arterial blood gas analysis, and other diagnostic tests as required, depending on the suspected underlying condition. To assess the consequences of chronic respiratory failure, measure complete blood count (look for polycythemia) and perform electrocardiography (ECG) and echocardiography (look for signs of pulmonary hypertension [see Pulmonary Hypertension] and right ventricular failure [see Chronic Heart Failure]).
For those with chronic hypercapnic respiratory failure that is bordering on the need for chronic mechanical ventilation, a sleep study may be helpful. Hypoventilation worsens during sleep and nocturnal noninvasive ventilation may be indicated while avoiding complete ventilator dependency.
In differential diagnosis, consider other causes of chronic dyspnea (see Dyspnea).
1. Treatment of the underlying disease.
2. Oxygen therapy during acute exacerbations (in hospital) or long-term oxygen therapy (at home).
3. Rehabilitation: Respiratory physiotherapy (including postural drainage), general rehabilitation (eg, physical therapy, exercise), and education of the patient and family/caregivers are mainstays of treatment.
4. Nutrition support to prevent malnutrition is important. However, the role for a high fat/low carbohydrate diet in minimizing the production of CO2 remains controversial.
5. Long-term mechanical ventilation in selected patients (mostly with neuromuscular diseases and COPD), at home (ideally with intermittent noninvasive ventilation) or in a clinical setting. Patients may initially require mechanical ventilation only while sleeping but over time progress to full-time chronic ventilation.
Note: It is often difficult to distinguish an acute exacerbation from a chronic progression to end-stage disease. In the latter situation, invasive treatments and mechanical ventilation have limited benefit and may cause unnecessary suffering. Ideally, a decision to undertake (or not) invasive support is discussed well in advance of end-stage disease, with both the patient and his or her caregivers, and a consultative body of physicians.
1. Pulmonary hypertension. Treatment: Oxygen therapy.
2. Right ventricular heart failure (see Chronic Heart Failure). Treatment: Oxygen therapy, diuretic therapy (potassium and magnesium supplementation, as needed).
3. Secondary polycythemia and hyperviscosity: Treatment: Oxygen therapy.
4. Malnutrition and cachexia.