Soru

A 68-year-old man is brought to the emergency department due to acute-onset, severe shortness of breath. He reports a dry cough and diffuse wheezing that began 2 hours prior to arrival. His medical background includes severe chronic obstructive pulmonary disease (COPD), essential hypertension, and a previous anterior myocardial infarction. At home, he used his albuterol inhaler three times with no improvement. Vital signs include a temperature of $37.0^\circ\text{C}$ ($98.6^\circ\text{F}$), blood pressure of $178/104\text{ mm Hg}$, heart rate of $114/\text{min}$, and respiratory rate of $28/\text{min}$. Pulse oximetry reveals an oxygen saturation of $86\%$ on room air. Physical examination shows a diaphoretic man in a tripod position, utilizing accessory muscles of respiration. The jugular venous pressure is visually elevated to $11\text{ cm H}_2\text{O}$. Cardiac auscultation reveals a regular tachycardia with a prominent early diastolic extra heart sound. Lung auscultation demonstrates bilateral expiratory wheezing; notably, no crackles are auscultated. A chest radiograph reveals hyperinflated lung fields, an enlarged cardiac silhouette, and cephalization of the pulmonary vasculature, without any focal consolidation. The patient is immediately initiated on noninvasive positive pressure ventilation (NIPPV). Over the next 15 minutes, his work of breathing and oxygen saturation improve significantly. Which of the following mechanisms best explains the primary physiological basis for this patient's rapid clinical improvement?