Sildenafil and Exercise Capacity in the Elderly at Moderate Altitude.
OBJECTIVE
Hypobaric hypoxia decreases exercise capacity and causes hypoxic pulmonary vasoconstriction and pulmonary hypertension. The phosphodiesterase-5 inhibitor sildenafil is a pulmonary vasodilator that may improve exercise capacity at altitude. We aimed to determine whether sildenafil improves exercise capacity, measured as maximal oxygen consumption (peak V̇o2), at moderate altitude in adults 60 years or older.


METHODS
The design was a randomized, double-blind, placebo-controlled, crossover study. After baseline cardiopulmonary exercise testing at 1400 m, 12 healthy participants (4 women) aged 60 years or older, who reside permanently at approximately 1400 m and are regularly active in self-propelled mountain recreation above 2000 m, performed maximal cardiopulmonary cycle exercise tests in a hypobaric chamber at a simulated altitude of 2750 m after ingesting sildenafil and after ingesting a placebo.


RESULTS
After placebo, mean peak V̇o2 was significantly lower at 2750 m than 1400 m: 37.0 mL · kg(-1) · min(-1) (95% CI, 32.7 to 41.3) vs 39.1 mL · kg(-1) · min(-1) (95% CI, 33.5 to 44.7; P = .020). After placebo, there was no difference in heart rate (HR) or maximal workload at either altitude (z = 0.182; P = .668, respectively). There was no difference between sildenafil and placebo at 2750 m in peak V̇o2 (P = .668), O2 pulse (P = .476), cardiac index (P = .143), stroke volume index (z = 0.108), HR (z = 0.919), or maximal workload (P = .773). Transthoracic echocardiography immediately after peak exercise at 2750 m showed tricuspid annular plane systolic velocity was significantly higher after sildenafil than after placebo (P = .019), but showed no difference in tricuspid annular plane systolic excursion (P = .720).


CONCLUSIONS
Sildenafil (50 mg) did not improve exercise capacity in adults 60 years or older at moderate altitude in our study. This might be explained by a "dosing effect" or insufficiently high altitude.
University of Utah School of Nursing, Salt Lake City, UT (Dr Rodway). Electronic address: gwrodway@ucdavis.edu.
George W
GW
Rodway
Department of Pulmonary and Critical Care (Ms Lovelace, Drs Lanspa and Grissom, and Mr Briggs).
Anne J
AJ
Lovelace
Department of Pulmonary and Critical Care (Ms Lovelace, Drs Lanspa and Grissom, and Mr Briggs).
Michael J
MJ
Lanspa
Division of Emergency Medicine (Dr McIntosh).
Scott E
SE
McIntosh
Intermountain Medical Center (Mr Bell and Dr Weaver), Murray, UT; Hyperbaric Medicine (Mr Bell), LDS Hospital, Salt Lake City, UT.
James
J
Bell
Department of Pulmonary and Critical Care (Ms Lovelace, Drs Lanspa and Grissom, and Mr Briggs).
Ben
B
Briggs
Intermountain Medical Center (Mr Bell and Dr Weaver), Murray, UT; Department of Pulmonary and Critical Care (Dr Weaver); School of Medicine (Drs Weaver and Yanowitz), University of Utah, Salt Lake City, UT.
Lindell K
LK
Weaver
and ECG Services and Cardiac Rehabilitation (Dr Yanowitz); School of Medicine (Drs Weaver and Yanowitz), University of Utah, Salt Lake City, UT.
Frank
F
Yanowitz
Department of Pulmonary and Critical Care (Ms Lovelace, Drs Lanspa and Grissom, and Mr Briggs).
Colin K
CK
Grissom
D000368:Aged; D000531:Altitude; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D000068677:Sildenafil Citrate / Q000494:pharmacology*; D016896:Treatment Outcome; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D000068677:Sildenafil Citrate
elderly; exercise; high altitude; peak V̇o(2); sildenafil