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Central chemosensitivity is augmented during 2 h of thermoneutral head‐out water immersion in healthy men and women
Author(s) -
Sackett James R.,
Schlader Zachary J.,
O'Leary Morgan C.,
Chapman Christopher L.,
Johnson Blair D.
Publication year - 2018
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/ep086870
Subject(s) - immersion (mathematics) , medicine , psychology , mathematics , pure mathematics
New FindingsWhat is the central question of the study? Is central chemosensitivity blunted during thermoneutral head‐out water immersion in healthy humans?What is the main finding and its importance? Central chemosensitivity is augmented during thermoneutral head‐out water immersion in healthy men and women. Thus, we suggest that the central chemoreceptors do not contribute to CO 2 retention during head‐out water immersion.Abstract Carbon dioxide retention occurs during water immersion. Therefore, we tested the hypothesis that central chemosensitivity to hypercapnia is blunted during 2 h of thermoneutral head‐out water immersion (HOWI) in healthy young adults. Twenty‐six participants (age 22 ± 2 years; body mass index 24 ± 3 kg m −2 ; 14 women) participated in two experimental visits: a HOWI visit (HOWI) and a dry time‐control visit (Control). Central chemosensitivity was assessed via a rebreathing test at baseline, 10, 60, 90 and 120 min and after HOWI and Control. End‐tidal CO 2 tension ( PET , C O 2), minute ventilation, blood pressure and heart rate were recorded continuously. The PET , C O 2increased from baseline throughout HOWI (peak increase at 120 min 2 ± 2 mmHg; P < 0.001), and the change in PET , C O 2was greater throughout HOWI than Control ( P < 0.001). The change in minute and alveolar ventilation was not different throughout time ( P ≥ 0.173) or between conditions ( P ≥ 0.052). Central chemosensitivity was greater than at baseline throughout HOWI (peak increase 0.74 ± 1.01 l min −1 mmHg −1 at 120 min; P < 0.001), and the change in central chemosensitivity was greater throughout HOWI than Control ( P ≤ 0.006). We also divided the cohort into tertiles based on baseline central chemosensitivity (i.e. Low, Intermediate and High) and compared Low versus High during HOWI. Low demonstrated an increase in PET , C O 2starting at 10 min (2 ± 3 mmHg; P < 0.001), whereas High did not exhibit an increase in PET , C O 2until 60 min (2 ± 2 mmHg; P = 0.018). These data indicate that CO 2 retention occurs throughout HOWI despite augmented central chemosensitivity and that having a high baseline central chemosensitivity might delay the onset of CO 2 retention.