Date of Graduation

12-11-2012

Degree Type

Capstone Project

Degree Name

Master of Science in Physician Assistant Studies

Abstract

Background: Many people work and play at higher altitudes where hypoxia can cause altitude sickness and hamper one’s ability to carry out physical tasks. Nifedipine is currently the adjunct drug of choice for altitude sickness, but it carries the risk for hypotension. There is evidence that sildenafil can be used to prevent high altitude pulmonary edema (HAPE), and given its excellent safety profile, may prove to be a viable alternative. What is the usefulness of sildenafil in the prevention of HAPE and the improvement of aerobic capacity in young healthy adults at high altitudes?

Methods: An exhaustive search of available literature was conducted using the search terms: [sildenafil or PDE or phosphodiesterase] and [altitude or altitude sickness] and [hypoxia or anoxia] and pulmonary hypertension. Only studies that also analyzed some component of athletic performance were considered.

Results: Five studies met the final inclusion criteria investigating the effects of sildenafil during hypoxic exercise. The Lalande et al study found that sildenafil caused a blunted respiratory drive with no change in peripheral oxygen saturation (SpO2) and a decrease in right ventricle systolic pressure (RVSP). The Hsu et al study found that sildenafil increased cardiac output (Q), SpO2, and improved cycling performance as well. The Ghofrani study found that sildenafil improved Q and cycling power while decreasing pulmonary artery pressure (PAP) in both acute and chronic hypoxia. The Ricart study found that sildenafil reduced PAP and slightly improved SpO2. The Richalet study found improved SpO2, PAP, Q, and maximum oxygen consumption (VO2 max).

Conclusion: The data from these 5 studies suggests that sildenafil can be used to prevent pulmonary hypertension and therefore reduce the risk for HAPE during hypoxic exercise. It also suggests that sildenafil can prevent hypoxia-induced decreases in exercise tolerance and aerobic capacity. There is no data comparing the efficacy of sildenafil and nifedipine and clinical experience with sildenafil for this purpose is limited. At this time sildenafil should only be considered an alternative to nifedipine in the prevention of HAPE and aerobic decline.

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