Dyspnea and Acute Respiratory Failure

Posted by e-Medical PPT
Respiratory failure is a condition in which the respiratory system fails in one or both of its gas exchange functions: oxygenation and carbon dioxide elimination. In practice, respiratory failure is defined as a PaO2 value of less than 60 mm Hg while breathing air or a PaCO2 of more than 50 mm Hg. Furthermore, respiratory failure may be acute or chronic. Although acute respiratory failure is characterized by life-threatening derangements in arterial blood gases and acid-base status, the manifestations of chronic respiratory failure are less dramatic and may not be as readily apparent.
Hypoxemic respiratory failure (type I) is characterized by a PaO2 of less than 60 mm Hg with a normal or low PaCO2. This is the most common form of respiratory failure, and it can be associated with virtually all acute diseases of the lung, which generally involve fluid filling or collapse of alveolar units.
Hypercapnic respiratory failure (type II) is characterized by a PaCO2 of more than 50 mm Hg. Hypoxemia is common 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. Common etiologies include drug overdose, neuromuscular disease, chest wall abnormalities, and severe airway disorders.


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