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

Status

Completed

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT00946933

Enrollment

Registered

2009-07-27

Start date

2009-11-30

Completion date

2010-09-30

Last updated

2012-12-17

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Healthy

Keywords

acid-base balance, ventilatory control, dyspnea, exercise, modified rebreathing procedure, Normal, older

Brief summary

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.

Interventions

DIETARY_SUPPLEMENTNH4Cl (ammonium chloride)

0.2 g/kg/day of NH4Cl (ammonium chloride)

DIETARY_SUPPLEMENTplacebo

0.025 g/kg/day of NaCl (sodium chloride)

Study design

Allocation

RANDOMIZED

Intervention model

CROSSOVER

Primary purpose

BASIC_SCIENCE

Masking

TRIPLE (Subject, Investigator, Outcomes Assessor)

Eligibility

Sex/Gender

ALL

Age

20 Years to 80 Years

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

Design outcomes

Primary

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

Secondary

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

Countries

Canada

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 4, 2026