Chronic respiratory failure definition
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Definition of Chronic Respiratory Failure
Chronic respiratory failure is a condition where the respiratory system is unable to perform its essential gas exchange functions—specifically, oxygenating the blood and/or removing carbon dioxide—over a prolonged period. This failure is typically identified by a persistent reduction in arterial oxygen tension (PaO2) below 60 mmHg (8.0 kPa) and/or an increase in arterial carbon dioxide tension (PaCO2) above 45 mmHg (6.0 kPa) while breathing room air. These values serve as general guidelines, and the diagnosis is confirmed through arterial blood gas analysis, taking into account the patient’s clinical history and presentation 123459.
Key Features and Diagnostic Criteria
Chronic respiratory failure is distinguished from acute respiratory failure by the presence of compensatory mechanisms, such as the kidneys retaining bicarbonate to help maintain normal blood pH. This adaptation is a hallmark of the chronic form and helps differentiate it from acute episodes 45. The diagnosis relies on laboratory findings, particularly arterial blood gas measurements, and is supported by clinical suspicion based on symptoms and risk factors 13459.
Causes and Pathophysiology
The most common causes of chronic respiratory failure include chronic obstructive pulmonary disease (COPD), interstitial lung diseases, chest wall and neuromuscular disorders, and morbid obesity. The underlying mechanisms often involve ventilation-perfusion (V/Q) mismatch, hypoventilation, diffusion limitation, or true shunt, with V/Q mismatch being the most significant contributor to hypoxemia. Hypercapnia, or elevated CO2, results from inadequate alveolar ventilation or V/Q abnormalities 23457.
Clinical Presentation
Patients with chronic respiratory failure may experience symptoms such as shortness of breath, fatigue, reduced exercise tolerance, and sleepiness. These symptoms develop gradually, allowing time for the body to activate compensatory mechanisms 456.
Conclusion
Chronic respiratory failure is a laboratory-defined condition marked by the inability of the lungs to maintain normal levels of oxygen and/or carbon dioxide in the blood over time. It is characterized by specific blood gas thresholds, the presence of compensatory physiological mechanisms, and is most commonly caused by chronic lung, chest wall, or neuromuscular diseases. Diagnosis is based on a combination of clinical assessment and arterial blood gas analysis, with management focused on treating the underlying cause and correcting gas exchange abnormalities 12345679.
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