Clinical trial NCT06399575: Characterizing Hypoxic Apnea Intra-individual Repeatability
Official title: Characterizing the Repeatability and Reproducibility of Cardiovascular Responses to Hypoxic Apneas
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Hypoxia
Apnea
Keywords: Repeatability
Reproducibility
Heart Rate
Lead sponsor: University of Alberta
Sponsor class: OTHER
First posted: 2024-05-06
Enrollment: 16
Sex: ALL
Minimum age (years): 18
Maximum age (years): 70
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: NA
Intervention model: SINGLE_GROUP
Primary purpose: BASIC_SCIENCE

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.


Eligibility criteria: 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

Primary outcomes:
measure: Heart Rate
timeFrame: 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).
Secondary outcomes:
measure: Blood Pressure
timeFrame: 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).
measure: Cardiac Arrhythmias
timeFrame: 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).
measure: Peripheral Oxygen Saturation
timeFrame: 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).
measure: Rating of Perceived Exertion
timeFrame: Apnea (immediately following apnea)
measure: Apnea Duration
timeFrame: 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.
Other outcomes:
measure: End-Tidal Oxygen
timeFrame: Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea).
measure: End-Tidal Carbon Dioxide
timeFrame: Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea).
measure: Minute Ventilation
timeFrame: Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea).
Locations:
city: Edmonton
country: Canada
facility: University of Alberta
state: Alberta
Study officials:
References:
citation: Busch SA, Davies H, van Diepen S, Simpson LL, Sobierajski F, Riske L, Stembridge M, Ainslie PN, Willie CK, Hoiland R, Moore JP, Steinback CD. Chemoreflex mediated arrhythmia during apnea at 5,050 m in low- but not high-altitude natives. J Appl Physiol (1985). 2018 Apr 1;124(4):930-937. doi: 10.1152/japplphysiol.00774.2017. Epub 2017 Dec 21.
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