A dive into the physiological responses to maximal apneas, O 2 and CO 2 tables in apnea novices.

Purpose: Apnea duration is dependent on three factors: oxygen storage, oxygen consumption, hypoxia and hypercapnia tolerance. While current literature focuses on maximal apneas to improve apnea duration, apnea trained individuals use timed-repeated submaximal apneas, called "O ₂ and CO ₂ tables". These tables claim to accommodate the body to cope with hypoxia and hypercapnia, respectively. The aim of this study was twofold. First, to investigate the determinants of maximal apnea duration in apnea novices. Second, to compare physiologic responses to maximal apneas, O ₂ and CO ₂ tables.
Methods: After medical screening, lung function test and hemoglobin mass measurement, twenty-eight apnea novices performed three apnea protocols in random order: maximal apneas, O ₂ table and CO ₂ table. During apnea, peripheral oxygen saturation (SpO ₂ ), heart rate (HR), muscle (mTOI) and cerebral (cTOI) tissue oxygenation index were measured continuously. End-tidal carbon dioxide (EtCO ₂ ) was measured before and after apneas.
Results: Larger lung volumes, higher resting cTOI and lower resting EtCO ₂ levels correlated with longer apnea durations. Maximal apneas induced greater decreases in SpO ₂ (- 16%) and cTOI (- 13%) than O ₂ (- 8%; - 8%) and CO ₂ tables (- 6%; - 6%), whereas changes in EtCO ₂ , HR and mTOI did not differ between protocols.
Conclusion: These results suggest that, in apnea novices, O ₂ and CO ₂ tables did not induce a more profound hypoxia and hypercapnia, but a similar reduction in oxygen consumption than maximal apneas. Therefore, apnea novices should mainly focus on maximal apneas to improve hypoxia and hypercapnia tolerance. The use of specific lung training protocols can help to increase oxygen storage capacity.
Competing Interests: Declarations Competing interests The authors declare that they have no competing interest. Consent to participate A written informed consent was obtained from all individual participants included in the study. Consent to publish Not applicable. Ethics approval “All procedures performed in studies involving human participants were in accordance with the ethical standards of the ethical committee of the Ghent University Hospital (EC UZG 2018/0221) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
(© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)