Apnea, Hypoxia
Conditions
Keywords
Repeatability, Reproducibility, Heart Rate
Brief summary
Apneas (breath-holds) are increasingly being tested in human subjects to understand how the human body operates. Apneas decrease heart rate and increase blood pressure. These findings are driving current research into the effects of oxygen concentrations on the heart rate and blood pressure responses to apneas and the effect of breath-hold training on these responses. The interest in apnea research is three-fold: 1. Apneas are a nervous system stressor that can help researchers better understand the fundamental operation of the human body; 2. Elite divers can use findings from research to better their training and performance; and 3. The scientific understanding of apneas may translate to a better understanding of sleep apnea. Despite this interest, little is known about the repeatability (the consistency within a single day) and reproducibility (the consistency between days) in the heart rate and blood pressure responses to apneas. This uncertainty limits the scientific interpretations from previous results. This study aims to determine the repeatability and reproducibility of heart rate and blood pressure responses to apneas. The goals of the study are: 1. To provide greater certainty to previous results; and 2. Inform best practices for future studies. The study requires 20 healthy volunteers (10 females) and will measure heart rate, blood pressure, breathing parameters (expired gas concentrations, breathing volume and rate), and oxygen saturation. During the protocol, participants will complete two maximal voluntary apneas and five test apneas. The test apneas will all be the same length based on the longer of the two maximal voluntary apneas. Before each apnea, participants will also breathe low oxygen concentrations (hypoxia). Hypoxia provides a bigger decrease in heart rate during apneas than room air which makes it easier to see changes in heart rate responses between apneas (i.e., bigger signal-to-noise ratio). Participants will complete two identical test sessions on back-to-back days. The differences in heart rate and blood pressure responses to the five apneas within each session will determine repeatability and the differences between sessions will determine reproducibility. The investigators hypothesize that repeatability will be good and that repeatability within a session will be better than reproducibility between sessions.
Interventions
OTHERApnea Following Isocapnic Hypoxia
Decreasing end-tidal partial pressure of oxygen to 50 mmHg for five minutes, targeting 80-85% peripheral oxygen saturation. The end-tidal partial pressure of carbon dioxide will remain +1 mmHg above baseline levels. After five minutes of hypoxia, participants will complete an apnea.
Sponsors
University of Alberta
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 70 Years
Healthy volunteers
Yes
Inclusion criteria
* Males and females between the ages of 18-70
Exclusion criteria
* Having known cardiovascular or nervous system disease * Low or high blood pressure (\< 90/60 or \>139/85, respectively) * Taking any prescribed medications (other than oral contraceptives) that may affect cardiovascular system function * Females who may be pregnant (self-reported) * Involved in other studies
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Heart Rate | Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before each apnea) and during apneas (beat-by-beat extraction from the 10 beats preceding resumption of breathing). | Electrocardiogram (lead II) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Cardiac Arrhythmias | Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during apneas (beat-by-beat observation from the 10 beats preceding the resumption of breathing). | Assessed using electrocardiogram (lead II) by a trained researcher and reviewed by a cardiologist. Arrhythmias observable in lead II will be reported as a binary (i.e., yes/no) for each individual for each apnea. Example arrhythmias are premature atrial contractions and sinus pauses, though many more exist. |
| Peripheral Oxygen Saturation | Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before each apnea) and during apneas (10 beats preceding the resumption of breathing to 1 minute after apnea end). | Pulse Oximetry |
| Rating of Perceived Exertion | Apnea (immediately following apnea) | Participants Rate the Effort of their Apnea using the Modified Borg Scale with scores from 1 to 10 with 1 representing no effort and 10 representing a maximal effort. |
| Apnea Duration | Start to end of apnea: apnea start determined using cessation of flow through the pneumotachometer, apnea end determined using respiratory belt strain gauge. Estimated apnea durations are 15-30 seconds. | Time, in seconds, from the end of the last breath preceding the apnea to the resumption of breathing. |
| Blood Pressure | Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before each apnea) and during apneas (beat-by-beat extraction from the 10 beats preceding resumption of breathing). | Finger Photoplethysmography |
Other
| Measure | Time frame | Description |
|---|---|---|
| Minute Ventilation | Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea). | Pneumotachometer |
| End-Tidal Carbon Dioxide | Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea). | CD-3A Carbon Dioxide Analyzer & P-61B Sensor |
| End-Tidal Oxygen | Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea). | S-3A/I Oxygen Analyzer & Model N-22M Sensor, AEI Technologies |
Countries
Canada
Outcome results
None listed