Ventilatory responses to independent and combined hypoxia, hypercapnia and hypobaria in healthy pre-term-born adults

Narang, Benjamin J. (author), Manferdelli, Giorgio (author), Bourdillon, Nicolas (author), Millet, Grégoire P. (author), Debevec, Tadej (author)

Pre-term birth is associated with physiological sequelae that persist into adulthood. In particular, modulated ventilatory responsiveness to hypoxia and hypercapnia has been observed in this population. Whether pre-term birth per se causes these effects remains unclear. Therefore, we aimed to assess pulmonary ventilation and blood gases under various environmental conditions, comparing 17 healthy prematurely born individuals (mean ± SD; gestational age, 28 ± 2 weeks; age, 21 ± 4 years; peak oxygen uptake, 48.1 ± 11.2 ml kg$^{−1}$ min$^{−1}$) with 16 well-matched adults born at term (gestational age, 40 ± 1 weeks; age, 22 ± 2 years; peak oxygen uptake, 51.2 ± 7.7 ml kg$^{−1}$ min$^{−1}$). Participants were exposed to seven combinations of hypoxia/hypobaria (equivalent to ∼3375 m) and/or hypercapnia (3% CO$_2$), at rest for 6 min. Pulmonary ventilation, pulse oxygen saturation and the arterial partial pressures of O$_2$ and CO$_2$ were similar in pre-term and full-term individuals under all conditions. Higher ventilation in hypoxia compared to normoxia was only observed at terrestrial altitude, despite an equivalent (normobaric) hypoxic stimulus administered at sea level (0.138 F$_{iO_2}$). Assessment of oscillations in key variables revealed that combined hypoxic hypercapnia induced greater underlying fluctuations in ventilation in pre-term individuals only. In general, higher pulse oxygen saturation fluctuations were observed with hypoxia, and lower fluctuations in end-tidal CO$_2$ with hypercapnia, despite similar ventilatory oscillations observed between conditions. These findings suggest that healthy prematurely born adults display similar overall ventilation to their term-born counterparts under various environmental stressors, but that combined ventilatory stimuli could induce an irregular underlying ventilatory pattern. Moreover, barometric pressure may be an important factor when assessing ventilatory responsiveness to moderate hypoxic stimuli.

• Language: English
• Keywords: altitude, chemosensitivity, hypercapnia, hypobaria, hypoxia, prematurity, ventilation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FŠ - Faculty of Sport
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: Str. 5943–5958
• Numbering: Vol. 602, iss. 21
• PID: 20.500.12556/RUL-164611
• UDC: 612
• ISSN on article: 0022-3751
• DOI: 10.1113/JP285300
• COBISS.SI-ID: 167257091
• Publication date in RUL: 05.11.2024

Record is a part of a journal

• Title: The journal of physiology
• Shortened title: J. physiol.
• Publisher: Wiley, The Physiological Society
• ISSN: 0022-3751
• COBISS.SI-ID: 1582095

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: N5-0152
• Name: Mehanizmi hipoksične (in)tolerance pri predčasno rojenih posameznikih

• Funder: SNSF - Swiss National Science Foundation
• Project number: 320030L_192 073