17th Annual ECSS-Congress, Bruges 2012

Abstract details

Abstract-ID: 703
Session: [PO-CPP-17] Physiology
Lecture room: Gallery
Date & time: 07.07.2016 / -
Title of the paper: The combined exposures between intermittent hypoxia and cold is associated with enhanced respiratory long-term facilitation and peripheral chemoreflex sensitivity with an elevated CO2 in human
Authors: Fukuoka, Y., Kimura, A., Hojyo, T., Nakamura, M., Ebine, N.
Institution: Doshisha University
Department: Faculty of Health and Sports Science
Country: Japan
Abstract text Introduction: Long-term facilitation of ventilation (vLTF) following acute intermittent hypoxic (IH) maneuver is only expressed when CO2 maintained above isocapnic levels in humans (Harris et al. 2005). vLTF might be characterized by promoting the serotonin neural pathways of respiratory plasticity (Gonzalez-Rothni et al., 2015). We investigated effects of cold in ventilatory responses at IH exposure with an elevated CO2. Methods: Nine healthy males (years: 22.63.3yrs) experienced a series of IH breathing the hypoxic air (FIO2: 10%) and the room air (FIO2: 21%) seven times alternating every four minutes with two temperature conditions: normal temperature (34 deg) and low temperature (11 deg). Subjects wear the perfused suits. The rectal temperature (Tre) and four skin temperatures (chest, upper arm, thigh and calf) were measured to calculate mean skin body temperature (Tb), temperature (Tsk), respectively. Breath-by-breath ventilation (VE) and O2 saturation (SpO2) were monitored by the metabolic chart. End-tidal CO2 pressure (PETCO2) was maintained at basal level (isocapnia) and higher level (+4 mmHg, hypercapnia). Results: Low temperature induced the unchanged Tre and the remarkable decreased Tsk and Tb (p <0.01), otherwise normal temperature made unchanged Tre and Tsk throughout the experiment. The VE was fluctuated at low temperature during IH with the occurrence of vLTF independent of CO2. Greater VE response at low temperature was also gradually increased at hypercapnia compared with isocapnia. Acute hypoxia ventilatory responsiveness (HVR: ΔVE/ΔSpO2) tended to be increased with the repeated hypoxia. A significantly reduction in Tb at low temperature was related to the augmented VE during isocapnic IH (r = 0.88, p<0.05), however, the hypercapnic IH would depress the slopes of this relationship. Discussion: At normal temperature, the enhancement in vLTF could appear following IH maneuver at an elevated CO2 in human. Besides this, further progression HVR by cold exposure could produce the tight linkage between Tb and VE. On the other hand, this relationship was inhibited by hypercapnia associated with the enhanced basal VE. In conclusion, the IH induced the repeated enhancement in the VE response with long-term facilitation associated with cold and an elevated CO2. Hypoxic induced VE response could be linearly enhanced by cold exposure. References: Harris DP1, Balasubramaniam A, Badr MS, Mateika JH (2006) Am J Physiol 291, R1111-1119. Gonzalez-Rothi EJ, Lee KZ, Dale EA, Reier PJ, Mitchell GS, Fuller DD (2015) J Appl Physiol 119, 14551465.
Topic: Physiology
Keyword I: cold
Keyword II: hypoxia
Keyword III: ventilation