Characterizing Hypoxic Apnea Intra-individual Repeatability

Not Applicable

Completed

• Conditions: Hypoxia; Apnea
• Interventions: Other: Apnea Following Isocapnic Hypoxia

• Registration Number: NCT06399575
• Lead Sponsor: University of Alberta

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.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2024-04-21
• Study Start: 2024-05-02
• Study First Submitted QC: 2024-05-03
• Study First Posted: 2024-05-06
• Primary Completion: 2024-06-28
• Study Completion: 2024-06-28
• Status Verified: 2024-07
• Last Update Submitted: 2024-07-01
• Last Update Posted: 2024-07-03

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 16

Inclusion Criteria

• Males and females between the ages of 18-70

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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

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
Apnea Following Isocapnic Hypoxia	Apnea Following Isocapnic Hypoxia	-

Primary Outcome Measures

Name	Time	Method
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 Outcome Measures

Name	Time	Method
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
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.
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.
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
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.

Trial Locations

Locations (1)

University of Alberta; 🇨🇦 Edmonton, Alberta, Canada