A. Incorrect response: See explanation C.
B. Incorrect response: See explanation C.
C. Correct response: Studies have demonstrated that children with severe croup treated with heliox experience a significant decrease in croup score and improvement in gas exchange. Other studies have shown a decrease in respiratory distress with the use of heliox. Heliox seems to decrease the work of breathing and improve gas exchange in nonintubated infants who have bronchiolitis. However, it may not confer benefit in those who are intubated.
The evidence for the use of heliox in patients with COPD exacerbation is not robust or mature. Most of the peer-reviewed literature consists of case reports, case series, and physiologic studies in small samples of carefully selected patients. Some patients with COPD exacerbation have a favorable physiologic response to heliox therapy, whereas others do not. Determining who as a COPD patient will be a responder and who will not is difficult.
D. Incorrect response: See explanation C.