PMID- 32421248 OWN - NLM STAT- MEDLINE DCOM- 20220221 LR - 20220221 IS - 1469-445X (Electronic) IS - 0958-0670 (Linking) VI - 106 IP - 1 DP - 2021 Jan TI - Cardiorespiratory hysteresis during incremental high-altitude ascent-descent quantifies the magnitude of ventilatory acclimatization. PG - 139-150 LID - 10.1113/EP088488 [doi] AB - NEW FINDINGS: What is the central question of this study? We assessed the utility of a new metric for quantifying ventilatory acclimatization to high altitude, derived from differential ascent and descent steady-state cardiorespiratory variables (i.e. hysteresis). Furthermore, we aimed to investigate whether the magnitude of cardiorespiratory hysteresis was associated with the development of acute mountain sickness. What is the main finding and its importance? Hysteresis in steady-state cardiorespiratory variables quantifies ventilatory acclimatization to high altitude. The magnitude of cardiorespiratory hysteresis during ascent to and descent from high altitude was significantly related to the development of symptoms of acute mountain sickness. Hysteresis in steady-state chemoreflex drive can provide a simple, non-invasive method of tracking ventilatory acclimatization to high altitude. ABSTRACT: Maintenance of arterial blood gases is achieved through sophisticated regulation of ventilation, mediated by central and peripheral chemoreflexes. Respiratory chemoreflexes are important during exposure to high altitude owing to the competing influence of hypoxia and hypoxic hyperventilation-mediated hypocapnia on steady-state ventilatory drive. Inter-individual variability exists in ventilatory acclimatization to high altitude, potentially affecting the development of acute mountain sickness (AMS). We aimed to quantify ventilatory acclimatization to high altitude by comparing differential ascent and descent values (i.e. hysteresis) in steady-state cardiorespiratory variables. We hypothesized that: (i) the hysteresis area formed by cardiorespiratory variables during ascent and descent would quantify the magnitude of ventilatory acclimatization; and (ii) larger hysteresis areas would be associated with lower AMS symptom scores during ascent. In 25 healthy, acetazolamide-free trekkers ascending to and descending from 5160 m, cardiorespiratory hysteresis was measured in the partial pressure of end-tidal CO(2) , peripheral oxygen saturation, minute ventilation, chemoreceptor stimulus index (end-tidal CO(2) /peripheral oxygen saturation) and the calculated steady-state chemoreflex drive (SS-CD; minute ventilation/chemoreceptor stimulus index) using portable devices (capnograph, peripheral pulse oximeter and respirometer, respectively). Symptoms of AMS were assessed daily using the Lake Louise questionnaire. We found that: (i) ascent-descent hysteresis was present in all cardiorespiratory variables; (ii) SS-CD is a valid metric for tracking ventilatory acclimatization to high altitude; and (iii) the highest AMS scores during ascent exhibited a significant, moderate and inverse correlation with the magnitude of SS-CD hysteresis (r(s) = -0.408, P = 0.043). We propose that ascent-descent hysteresis is a new and feasible way to quantify ventilatory acclimatization in trekkers during high-altitude exposure. CI - (c) 2020 The Authors. Experimental Physiology (c) 2020 The Physiological Society. FAU - Leacy, Jack K AU - Leacy JK AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. AD - Department of Physiology, School of Medicine, College of Medicine & Health, University College Cork, Cork, Ireland. FAU - Linares, Andrea M AU - Linares AM AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. FAU - Zouboules, Shaelynn M AU - Zouboules SM AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. FAU - Rampuri, Zahrah H AU - Rampuri ZH AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. FAU - Bird, Jordan D AU - Bird JD AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. FAU - Herrington, Brittney A AU - Herrington BA AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. FAU - Mann, Leah M AU - Mann LM AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. FAU - Soriano, Jan E AU - Soriano JE AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. FAU - Thrall, Scott F AU - Thrall SF AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. FAU - Kalker, Anne AU - Kalker A AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. AD - Radboud University, Nijmegen, The Netherlands. FAU - Brutsaert, Tom D AU - Brutsaert TD AD - Syracuse University, Syracuse, NY, USA. FAU - O'Halloran, Ken D AU - O'Halloran KD AUID- ORCID: 0000-0002-8832-1153 AD - Department of Physiology, School of Medicine, College of Medicine & Health, University College Cork, Cork, Ireland. FAU - Sherpa, Mingma T AU - Sherpa MT AD - Kunde Hospital, Khunde, Solukhumbu, Nepal. FAU - Day, Trevor A AU - Day TA AUID- ORCID: 0000-0001-7102-4235 AD - Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20200630 PL - England TA - Exp Physiol JT - Experimental physiology JID - 9002940 RN - S88TT14065 (Oxygen) SB - IM MH - Acclimatization/*physiology MH - Adult MH - *Altitude MH - Altitude Sickness/*physiopathology MH - Humans MH - Hypoxia/physiopathology MH - Lung/physiopathology MH - Oxygen/blood MH - Oxygen Saturation/*physiology OTO - NOTNLM OT - acute mountain sickness OT - high altitude OT - hypoxia OT - respiratory chemoreflexes OT - ventilatory acclimatization EDAT- 2020/05/19 06:00 MHDA- 2022/02/22 06:00 CRDT- 2020/05/19 06:00 PHST- 2020/02/14 00:00 [received] PHST- 2020/05/13 00:00 [accepted] PHST- 2020/05/19 06:00 [pubmed] PHST- 2022/02/22 06:00 [medline] PHST- 2020/05/19 06:00 [entrez] AID - 10.1113/EP088488 [doi] PST - ppublish SO - Exp Physiol. 2021 Jan;106(1):139-150. doi: 10.1113/EP088488. Epub 2020 Jun 30.