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

Effects of Chronic Acid-Base Changes on the Ventilatory and Perceptual Response to Hypercapnia, Hypoxia and Exercise in Healthy Older Adults

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.

Study Overview

• Status: Completed
• Conditions: Healthy
• Intervention / Treatment: Dietary supplement: placebo; Dietary supplement: NH4Cl (ammonium chloride)

• Study Type: Interventional
• Enrollment (Actual): 20
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Kingston, Ontario, Canada, K7L 2V7
      • Respiratory Investigation Unit at Kingston General Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 20 years to 80 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
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)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Breathlessness intensity (10-point Borg scale)	Measured at the end of each 3 day treatment period

Secondary Outcome Measures

Outcome Measure	Time Frame
Exercise capacity (peak VO2)	Measured at the end of each 3 day treatment period

Collaborators and Investigators

• Sponsor: Queen's University
• Investigators: Principal Investigator: Denis E O'Donnell, MD, FRCPC, Queen's University and Kingston General Hospital

Study record dates

Study Major Dates

• Study Start: November 1, 2009
• Primary Completion (Actual): September 1, 2010
• Study Completion (Actual): September 1, 2010

Study Registration Dates

• First Submitted: July 23, 2009
• First Submitted That Met QC Criteria: July 24, 2009
• First Posted (Estimate): July 27, 2009

Study Record Updates

• Last Update Posted (Estimate): December 17, 2012
• Last Update Submitted That Met QC Criteria: December 14, 2012
• Last Verified: December 1, 2012

More Information

Terms related to this study

• Keywords: exercise; dyspnea; Normal; older; ventilatory control; acid-base balance; modified rebreathing procedure
• Other Study ID Numbers: DSS-16198