This site became the new on June 19th. Learn more.
Show more Menu IMPORTANT: Listing of a study on this site does not reflect endorsement by the National Institutes of Health. Talk with a trusted healthcare professional before volunteering for a study. Read more... Menu IMPORTANT: Talk with a trusted healthcare professional before volunteering for a study. Read more... Menu
Give us feedback

Effects of Chronic Acid-Base Changes on Ventilatory and Perceptual Responses

This study has been completed.
Information provided by (Responsible Party):
Dr. Denis O'Donnell, Queen's University Identifier:
First received: July 23, 2009
Last updated: December 14, 2012
Last verified: December 2012

Approximately 30% of people aged 65 years and older experience breathlessness (perceived respiratory difficulty) during daily activity. The main causes of increased breathlessness in the healthy elderly are poorly understood and are the main focus of the proposed study. Some possible contributing factors include abnormalities in the control and/or mechanics of breathing. To evaluate these possible contributory factors, the investigators will compare ventilatory and perceptual responses to: 1) exercise, 2) increased levels of inspired carbon dioxide, and 3) reduced levels of inspired oxygen under strictly-controlled experimental conditions where the investigators increase or decrease breathing requirements by altering dietary salt intake in healthy 40-80 year old men and women.

Exercise and rebreathing tests will be performed at baseline and at the end of each 3 day treatment period. Breathlessness intensity will be measured and compared at a standardized work rate, ventilation or end-tidal PCO2 during these tests.

Condition Intervention
Healthy Dietary Supplement: NH4Cl (ammonium chloride) Dietary Supplement: placebo

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary Purpose: Basic Science
Official Title: Effects of Chronic Acid-Base Changes on the Ventilatory and Perceptual Response to Hypercapnia, Hypoxia and Exercise in Healthy Older Adults

Resource links provided by NLM:

Further study details as provided by Dr. Denis O'Donnell, Queen's University:

Primary Outcome Measures:
  • Breathlessness intensity (10-point Borg scale) [ Time Frame: Measured at the end of each 3 day treatment period ]

Secondary Outcome Measures:
  • Exercise capacity (peak VO2) [ Time Frame: Measured at the end of each 3 day treatment period ]

Enrollment: 20
Study Start Date: November 2009
Study Completion Date: September 2010
Primary Completion Date: September 2010 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Placebo Comparator: Placebo
0.025 g/kg/day of NaCl (sodium chloride)
Dietary Supplement: placebo
0.025 g/kg/day of NaCl (sodium chloride)
Active Comparator: High salt diet
0.2 g/kg/day of NH4Cl (ammonium chloride)
Dietary Supplement: NH4Cl (ammonium chloride)
0.2 g/kg/day of NH4Cl (ammonium chloride)


Ages Eligible for Study:   20 Years to 80 Years   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • healthy, regularly active adults
  • non-smoking
  • BMI 18-30 kg/m2

Exclusion Criteria:

  • history of lung and/or heart disease (including cardiac arrhythmias) or other comorbidity which could interfere with proper conduct of the intervention or tests
  • hypotension or hypertension
  • hypercholesterolemia
  • sleep disordered breathing
  • inability to perform cycle exercise or comply with other testing procedures
  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: NCT00946933

Canada, Ontario
Respiratory Investigation Unit at Kingston General Hospital
Kingston, Ontario, Canada, K7L 2V7
Sponsors and Collaborators
Queen's University
Principal Investigator: Denis E O'Donnell, MD, FRCPC Queen's University and Kingston General Hospital
  More Information

Responsible Party: Dr. Denis O'Donnell, Principal Investigator, Queen's University Identifier: NCT00946933     History of Changes
Other Study ID Numbers: DSS-16198
Study First Received: July 23, 2009
Last Updated: December 14, 2012

Keywords provided by Dr. Denis O'Donnell, Queen's University:
acid-base balance
ventilatory control
modified rebreathing procedure
older processed this record on September 19, 2017