Introduction to Respiratory Care Practice Test 2025 – Your Comprehensive All-in-One Guide to Exam Success!

The condition characterized by oxygen desaturation accompanying platypnea is orthodeoxia. Platypnea refers to the shortness of breath that occurs when a person is in an upright position, which can lead to a decreased arterial oxygen saturation. Orthodeoxia specifically describes this phenomenon, where oxygen levels drop due to changes in posture, often related to intrapulmonary shunting or ventilation-perfusion mismatches.

This situation is distinct from other respiratory conditions. For instance, hemoptysis pertains to coughing up blood, which does not inherently cause a position-dependent change in oxygen saturation. Similarly, purulent sputum is indicative of infection and inflammation in the lungs, where the sputum is thick and yellow or green, but again, does not relate to changes in oxygen saturation with posture. Mucoid sputum, typically clear or white, is more indicative of bronchitis or other chronic conditions and does not involve the specific desaturation phenomenon seen with orthodeoxia. Thus, orthodeoxia is the term that correctly describes the relationship between oxygen saturation changes and body posture in this context.