Cystic fibrosis (CF) has many health consequences. A reduction in the ability to perform exercise in patients with CF is related to greater death rates, steeper decline in lung function, and more frequent lung infections. However, the physiological mechanisms for this reduced exercise capacity are unknown. The investigators laboratory recently published the first evidence of systemic vascular dysfunction in patients with CF. Therefore, it is reasonable to suspect that the blood vessels are involved with exercise intolerance in CF. This study will look at how 1) blood flow and 2) artery function contribute to exercise capacity in CF.
The most disturbing aspect of Cystic Fibrosis (CF) is the associated premature death. Low exercise capacity predicts death in patients with CF and is also associated with a steeper decline in lung function and more lung infections. A critical barrier to improving exercise tolerance in patients with CF is the investigators lack of knowledge regarding the different physiological mechanisms which contribute to their lower exercise capacity. We have compelling data to indicate that the blood vessels may contribute to the low exercise capacity in CF. The impact of this proof of concept investigation will test Phosphodiesterase Type 5 inhibitors (PDE5) inhibitors as a potential therapy in CF and will explore blood flow and endothelial function as potential mechanisms which contribute to exercise intolerance in CF. Improvements in exercise capacity will not only contribute to a better quality of live for patients with CF, it will also increase longevity in these patients.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
19
Vascular function will be assessed 1 hour following oral ingestion of sildenafil (50 mg)
Vascular function will be assessed 4 weeks following 20 mg three times per day (TID) of sildenafil for four weeks
Sugar pill designed to mimic the sildenafil treatment
Augusta University
Augusta, Georgia, United States
Acute Study: Percentage Flow-Mediated Dilation (FMD)
FMD determined one hour after ingestion of 50 mg Sildenafil or placebo
Time frame: pre-treatment Baseline and 1 hour post-treatment
Baseline Diameter
Brachial Artery Diameter during FMD (pre-occlusion or "baseline")
Time frame: pre-treatment Baseline and following 4 weeks sub-chronic treatment
Peak Diameter
Peak Brachial Artery Diameter during FMD (post-occlusion)
Time frame: pre-treatment Baseline and following 4 weeks sub-chronic treatment
Absolute Change in Diameter
Absolute change in brachial artery diameter taken from the FMD assessment
Time frame: pre-treatment Baseline and following 4 weeks sub-chronic treatment
FEV1 (% Predicted)
Forced Expiratory Volume in the first second expressed as a percent predicted.
Time frame: pre-treatment Baseline, 1 hour post-treatment, and following 4 weeks sub-chronic treatment
VO2 Peak (Absolute)
absolute (L/min) peak oxygen consumption during maximal exercise test
Time frame: pre-treatment Baseline, 1 hour post-treatment, and following 4 weeks sub-chronic treatment
VO2 Peak (Relative)
relative (mL/kg/min) peak oxygen consumption during maximal exercise test
Time frame: pre-treatment Baseline, 1 hour post-treatment, and following 4 weeks sub-chronic treatment
VO2 Peak (Percent Predicted)
Maximal Oxygen consumption expressed as percent predicted taken from maximal exercise test.
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Time frame: pre-treatment Baseline and 1 hour post-treatment, and 4 weeks sub-chronic treatment
VE Peak
peak ventilation (L/min) during maximal exercise test
Time frame: pre-treatment Baseline, 1 hour post-treatment, and following 4 weeks sub-chronic treatment
RER Peak
peak respiratory exchange ratio during maximal exercise test
Time frame: pre-treatment Baseline, 1 hour post-treatment, and following 4 weeks sub-chronic treatment