A 12-year-old boy is brought to the clinic for a follow-up examination. The patient was admitted to the hospital 3 months ago after a nonfatal drowning event that resulted in severe acute respiratory distress syndrome. He was intubated and mechanically ventilated for 1 week and then discharged 2 weeks later. The patient currently feels well and reports mild dyspnea with exertion. Which of the following parameters is most likely increased in this patient compared to a child with normal cardiopulmonary function?

Question

A 12-year-old boy is brought to the clinic for a follow-up examination.  The patient was admitted to the hospital 3 months ago after a nonfatal drowning event that resulted in severe acute respiratory distress syndrome.  He was intubated and mechanically ventilated for 1 week and then discharged 2 weeks later.  The patient currently feels well and reports mild dyspnea with exertion.  Which of the following parameters is most likely increased in this patient compared to a child with normal cardiopulmonary function?

Quizplus · Accepted Answer

11ec160b_3b2a_baff_9249_bf3becdfccc5_MD0001_00 Acute respiratory distress syndrome (ARDS) refers to inflammatory lung damage triggered by alveolar injury (eg, aspiration of water) or intense systemic inflammation (eg, sepsis, pancreatitis). ARDS has a mortality rate of approximately 40%; those who survive often have reduced lung function that persists for months or years and is sometimes permanent. The pathogenesis of ARDS can progress through 3 phases, although most patients move through only the first 2. The exudative phase (phase 1) involves inflammatory disruption of the alveolar-capillary membrane with leakage of protein-rich fluid from the alveolar capillaries into the alveoli and surrounding interstitium. Gas exchange is acutely impaired by alveolar edema and by hyaline membranes that develop on the alveolar surface. After 1-2 weeks, ARDS progresses to the proliferative phase (phase 2), during which endothelial cells, pneumocytes, and fibroblasts proliferate in an attempt to repair damage. Collagen is deposited in the interstitium and may lead to scarring. The majority of ARDS survivors have a persistent reduction in diffusion capacity that eventually normalizes after several years (Choice B). These patients may remain in a prolonged proliferative phase in which interstitial collagen deposition and remodeling impair gas diffusion across the alveolar-capillary membrane, causing an increased alveolar-arterial oxygen gradient that manifests clinically with mild dyspnea. A small percentage of surviving patients likely enter and remain in the fibrotic phase (phase 3) of ARDS, during which severe interstitial fibrosis develops and manifests as an irreversible reduction in diffusion capacity with marked clinical symptoms (eg, severe dyspnea). (Choices C and E) Collagen deposition during recovery from ARDS typically leads to decreased lung compliance, which in some patients manifests as a restrictive defect with reductions in both forced vital capacity and forced expiratory volume in 1 second on pulmonary function testing. The reductions in expiratory lung volumes typically normalize within 6 months. (Choice D) The pulmonary edema in ARDS is noncardiogenic, meaning it does not result from heart failure and involves normal left atrial pressure (estimated by pulmonary capillary wedge pressure) during both the acute disease and recovery. Educational objective: Survivors of acute respiratory distress syndrome commonly have reduced lung function that persists for months or years and is sometimes permanent. The majority of patients have reduced diffusion capacity that eventually normalizes after several years, whereas a small percentage develop extensive fibrosis with a marked and permanent reduction in diffusion capacity.

A 12-Year-Old Boy Is Brought to the Clinic for a Follow-Up