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

Study Overview
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Brief Summary
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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.

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

Conditions
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Healthy

Intervention / Treatment
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* Dietary Supplement: NH4Cl (ammonium chloride)
* Dietary Supplement: placebo


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

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


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: Placebo<br>0.025 g/kg/day of NaCl (sodium chloride) | Dietary Supplement: placebo<br>* 0.025 g/kg/day of NaCl (sodium chloride)<br>|
| Active Comparator: High salt diet<br>0.2 g/kg/day of NH4Cl (ammonium chloride) | Dietary Supplement: NH4Cl (ammonium chloride)<br>* 0.2 g/kg/day of NH4Cl (ammonium chloride)<br>|

What is the study measuring?
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Primary Outcome Measures

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

Secondary Outcome Measures

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

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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acid-base balance, ventilatory control, dyspnea, exercise, modified rebreathing procedure, Normal, older