A 65-year-old woman with chronic obstructive pulmonary disease comes to the emergency department due to worsening shortness of breath and cough. She has a mild productive cough for the past 2 years but she noticed that her sputum is more yellow than usual over the past 2 days. She has not had any recent fevers, chills, sore throat, or a runny nose. Her only medication is a salmeterol inhaler that she uses twice daily. Pulse oximetry shows an oxygen saturation of 85% on room air. Expiratory wheezes are heard throughout the lungs. The patient is started on high-flow oxygen supplementation. Shortly afterward, she becomes increasingly lethargic and confused. This patient's clinical decline is most likely attributable to an increase in which of the following parameters?

Question

A 65-year-old woman with chronic obstructive pulmonary disease comes to the emergency department due to worsening shortness of breath and cough. She has a mild productive cough for the past 2 years but she noticed that her sputum is more yellow than usual over the past 2 days. She has not had any recent fevers, chills, sore throat, or a runny nose. Her only medication is a salmeterol inhaler that she uses twice daily. Pulse oximetry shows an oxygen saturation of 85% on room air. Expiratory wheezes are heard throughout the lungs.  The patient is started on high-flow oxygen supplementation.  Shortly afterward, she becomes increasingly lethargic and confused.  This patient's clinical decline is most likely attributable to an increase in which of the following parameters?

Quizplus · Accepted Answer

Eductional Objective: Supplemental oxygen administration in patients with chronic obstructive pulmonary disease can lead to increased CO₂ retention (oxygen-induced hypercapnia), resulting in confusion and depressed consciousness. The major cause is reversal of hypoxic pulmonary vasoconstriction, which increases physiologic dead space as blood is shunted away from well-ventilated alveoli.

A 65-Year-Old Woman with Chronic Obstructive Pulmonary Disease Comes to the Emergency