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Respiratory Failure

Common causes/etiologies of respiratory failure include neuromuscular disease, drug overdose, chest wall abnormalities, and critical airway disorders such as chronic obstructive pulmonary disease (COPD) and asthma.

Respiratory failure is a condition in which the patient’s respiratory system fails in both or one of its gas exchange functions: carbon dioxide elimination and oxygenation. It may be classified as either hypercapnic (high carbon dioxide) or hypoxemic (low oxygen).

Hypoxemic respiratory failure (Type I) and is defined by an arterial oxygen tension (Pa O2) lower than 60 mm Hg with a normal or low arterial carbon dioxide tension (Pa CO2) of 35-45 mm Hg. This is the most standard form of respiratory failure, and it can be affiliated with virtually all acute diseases of the lung, which typically involve collapse of alveolar units or fluid filling.

A few examples of type I respiratory failure are non-cardiogenic or cardiogenic pulmonary edema, pulmonary hemorrhage and pneumonia.

Hypercapnic respiratory failure (type II) is characterized by a PaCO2 (carbon dioxide) higher than 50 mm Hg. Hypoxemia is customary in patients with hypercapnic respiratory failure who are breathing room air. The pH depends on the level of bicarbonate, which, in turn, is dependent on the duration of hypercapnia.

Respiratory failure may also be additionally defined as either chronic or acute. Despite acute respiratory failure being classified by life threatening unsettled arterial blood gases and acid-base status, the presentations of chronic respiratory failure are less apparent and may not be as readily dramatic.

Acute hypercapnic respiratory failure evolves over minutes to hours. Consequently, pH is less than 7.3. Chronic respiratory failure usually develops over several days or more, allowing time for renal counteraction and therefore compensation and an accumulation of bicarbonate level/concentration. Accordingly, the pH typically is only slightly diminished.

The diagnosis between chronic and acute hypoxemic respiratory failure cannot immediately be made on the basis of arterial blood gases. The clinical markers of chronic hypoxemia, such as cor pulmonale (right-sided heart failure) or polycythemia (over-production of red blood cells), present a long-standing disease.

Arterial blood gases (ABG’s) will be evaluated in all whom respiratory failure is suspected or are seriously ill. Chest radiography (Chest X-Ray) is crucial. Echocardiography is sometimes useful but not routine. Pulmonary functions tests (PFTs) may be useful. Electrocardiography (ECG) should be completed to assess the potential of a cardiovascular etiology of respiratory failure; it also may identify dysrhythmias caused from severe hypoxemia or acidosis.

Hypoxemia is the dominate threat to organ function. Following the patient’s corrected hypoxemia and the hemodynamic and ventilatory status have balanced, every attempt will be made to distinguish and correct the primary pathophysiologic process that forced the patient into respiratory failure initially. The specialized medical treatment depends on the etiology of respiratory failure.