Characterizing Hypoxic Apnea Intra-individual Repeatability

Hypoxia Clinical Trial

— CHAIR  

Official title:

Characterizing the Repeatability and Reproducibility of Cardiovascular Responses to Hypoxic Apneas

Clinical Trial Details — Status: Recruiting

Administrative data

• NCT number: NCT06399575
• Other study ID #: Pro00138947
• Status: Recruiting
• Phase: N/A
• Start date: May 2, 2024
• Est. completion date: May 2025

Study information

• Verified date: May 2024
• Source: University of Alberta
• Contact: Desmond A Young, BScKIN
• Phone: 780-492-5553
• Email: dayoung[@]ualberta.ca
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial 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.

Recruitment information / eligibility

• Status: Recruiting
• Enrollment: 20
• Est. completion date: May 2025
• Est. primary completion date: December 2024
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 18 Years to 70 Years

Eligibility

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

Related Conditions & MeSH terms

• Apnea
• Hypoxia

Intervention

Other:
• Apnea 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.

Locations

Country	Name	City	State
Canada	University of Alberta	Edmonton	Alberta

Sponsors (1)

Lead Sponsor	Collaborator
University of Alberta

Country where clinical trial is conducted

Canada, 

References & Publications (5)

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. — View Citation

Busch SA, van Diepen S, Steele AR, Meah VL, Simpson LL, Figueroa-Mujica RJ, Vizcardo-Galindo G, Villafuerte FC, Tymko MM, Ainslie PN, Moore JP, Stembridge M, Steinback CD. Global REACH: Assessment of Brady-Arrhythmias in Andeans and Lowlanders During Apnea at 4330 m. Front Physiol. 2020 Jan 22;10:1603. doi: 10.3389/fphys.2019.01603. eCollection 2019. — View Citation

Hopkins WG. Measures of reliability in sports medicine and science. Sports Med. 2000 Jul;30(1):1-15. doi: 10.2165/00007256-200030010-00001. — View Citation

Stanforth PR, Gagnon J, Rice T, Bouchard C, Leon AS, Rao DC, Skinner JS, Wilmore JH. Reproducibility of resting blood pressure and heart rate measurements. The HERITAGE Family Study. Ann Epidemiol. 2000 Jul;10(5):271-7. doi: 10.1016/s1047-2797(00)00047-8. — View Citation

Weir JP. Quantifying test-retest reliability using the intraclass correlation coefficient and the SEM. J Strength Cond Res. 2005 Feb;19(1):231-40. doi: 10.1519/15184.1. — View Citation

Outcome

Type	Measure	Description	Time frame	Safety issue
Other	End-Tidal Oxygen	S-3A/I Oxygen Analyzer & Model N-22M Sensor, AEI Technologies	Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea).
Other	End-Tidal Carbon Dioxide	CD-3A Carbon Dioxide Analyzer & P-61B Sensor	Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea).
Other	Minute Ventilation	Pneumotachometer	Continuous collection during both visits (2 hours on back-to-back days). Data will be extracted during free breathing (1 minute average before apnea).
Primary	Heart Rate	Electrocardiogram (lead II)	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	Blood Pressure	Finger Photoplethysmography	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	Cardiac Arrhythmias	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.	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).
Secondary	Peripheral Oxygen Saturation	Pulse Oximetry	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).
Secondary	Rating of Perceived Exertion	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 (immediately following apnea)
Secondary	Apnea Duration	Time, in seconds, from the end of the last breath preceding the apnea to the resumption of breathing.	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.