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Blood Flow and Vascular Function in Cystic Fibrosis (CF-FLOW)

This study is ongoing, but not recruiting participants.
Information provided by (Responsible Party):
Ryan Harris, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Identifier:
First received: February 4, 2014
Last updated: September 13, 2017
Last verified: September 2017
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.

Condition Intervention Phase
Cystic Fibrosis Drug: Acute (1 hour) Sildenafil Drug: Sub-Chronic (4 weeks) Sildenafil Drug: Placebo Phase 2

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary Purpose: Treatment
Official Title: Role of Blood Flow and Vascular Function on Exercise Capacity in Cystic Fibrosis

Resource links provided by NLM:

Further study details as provided by Ryan Harris, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK):

Primary Outcome Measures:
  • Exercise Capacity [ Time Frame: 1 hour ]
    Exercise Capacity will be determined one hour after ingestion of 50 mg Sildenafil

  • Exercise Capacity [ Time Frame: 4 weeks ]
    Exercise capacity will be determined after taking 20 mg of Sildenafil thrice daily for four weeks.

Secondary Outcome Measures:
  • Flow-Mediated Dilation (FMD) [ Time Frame: 1 hour and 4 weeks ]
    Brachial artery FMD induced by reactive hyperemia will be used to assess vascular endothelial function.

  • Arterial Stiffness Evaluation (PWV) [ Time Frame: 1 hour and 4 weeks ]
    A tonometer will be gently applied on the carotid artery and then the femoral artery and the radial artery to record how fast blood flows between each of the points.

  • Physio Flow [ Time Frame: 1 hour and 4 weeks ]
    Six surface electrodes will be placed on the body. 2 on the neck, 2 on the chest, and 2 on the back in order to measure parameters of the heart during exercise.

Estimated Enrollment: 50
Study Start Date: April 2014
Estimated Study Completion Date: December 2017
Estimated Primary Completion Date: December 2017 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: Acute (1 hour) Sildenafil & Placebo
In randomized order, on two separate days, exercise capacity and endothelial function will be determined 1 hour following a single dose of either sildenafil (50 mg) or placebo.
Drug: Acute (1 hour) Sildenafil
Exercise capacity and vascular function will be assessed 1 hour following oral ingestion of sildenafil (50 mg)
Other Names:
  • Viagra
  • Revatio
Drug: Placebo
Sugar pill designed to mimic the sildenafil treatment
Experimental: Sub Chronic (4 weeks) Sildenafil
Following the acute study, patients will be instructed to take 20 mg of sildenafil, three times a day, for 4 weeks. Exercise capacity and endothelial function will be determined within 48 hours following the last dose.
Drug: Sub-Chronic (4 weeks) Sildenafil
Exercise capacity and vascular function will be assessed 4 weeks following 20 mg three times per day (TID) of sildenafil for four weeks
Other Names:
  • Viagra
  • Revatio

Detailed Description:
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.

Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria.

  • Diagnosis of CF and healthy controls
  • Men and women (greater than 18 yrs. old)
  • Resting oxygen saturation (room air) greater than 90%
  • Forced expiratory volume (FEV1) percent predicted greater than 30%
  • Patients with or without CF related diabetes
  • Traditional CF-treatment medications
  • Ability to perform reliable/reproducible pulmonary function tests (PFT)
  • Clinically stable for 2 weeks (no exacerbations or need for antibiotic treatment within 2 weeks of testing or major change in medical status)

Exclusion Criteria.

  • Children less than 17 years old
  • Body mass less than 20 kg
  • A diagnosis of pulmonary arterial hypertension (PAH)
  • FEV1 less than 30% of predicted
  • Resting oxygen saturation (SpO2) less than 90%
  • Self-reported to be a smoker
  • Current use of any vaso-active medications
  • History of migraine headaches
  • Pregnant or nursing at the time of the investigation
  • A clinical diagnosis of cardiovascular disease, hypertension, or CF related diabetes
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT02057458

United States, Georgia
Georgia Regents University
Augusta, Georgia, United States, 30912
Sponsors and Collaborators
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Principal Investigator: Ryan Harris, Ph.D. Augusta University
  More Information

Additional Information:
Responsible Party: Ryan Harris, Assistant Professor, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Identifier: NCT02057458     History of Changes
Other Study ID Numbers: DK100783
Study First Received: February 4, 2014
Last Updated: September 13, 2017
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: Yes

Keywords provided by Ryan Harris, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK):
arterial stiffness
flow-mediated dilation
endothelial function
pulse wave velocity
oxidative stress
pulmonary function test
Cystic Fibrosis
Lung Disease
Nitric Oxide
Exercise Capacity
Muscle Function

Additional relevant MeSH terms:
Cystic Fibrosis
Pathologic Processes
Pancreatic Diseases
Digestive System Diseases
Lung Diseases
Respiratory Tract Diseases
Genetic Diseases, Inborn
Infant, Newborn, Diseases
Sildenafil Citrate
Vasodilator Agents
Phosphodiesterase 5 Inhibitors
Phosphodiesterase Inhibitors
Enzyme Inhibitors
Molecular Mechanisms of Pharmacological Action
Urological Agents processed this record on September 21, 2017