Chronic respiratory failure is usually recognized by a combination of chronic hypoxemia, hypercapnea and compensatory metabolic alkalosis (elevated bicarbonate levels). Whenever a patient's medical problems include this condition, it is very important to document it in the medical record, as chronic respiratory failure contributes significantly to the severity level, complexity and costs of care.
Many patients with severe or long-standing chronic obstructive pulmonary disease (COPD) also have chronic respiratory failure. If a patient is admitted for an acute exacerbation of COPD, always look for findings consistent with chronic respiratory failure. Typically patients with chronic respiratory failure require supplemental home oxygen therapy, so the diagnosis should be strongly considered for any patient using home oxygen.
In pure chronic respiratory failure, the pH value on arterial blood gases will be normal (7.35-7.45). Any degree of respiratory acidosis or worsening of respiratory symptoms indicates that acute respiratory failure is now superimposed on the chronic state. The appropriate diagnostic term for this circumstance is “acute on chronic respiratory failure”—a very important distinction to make since the acute state represents a much more serious condition.
Even if the patient's chronic respiratory failure is stable, unchanged or at baseline, however, it should be documented in the medical record as a significant comorbid condition that needs to be coded.