2007, Piran, Slovenia

Altitude Physiology
HYPOXIA INDUCED ALTERATIONS IN
THERMOREGULATORY CUTANEOUS THRESHOLDS
Uriëll Malanda 1 , Jos Reulen 2 , Wim Saris 1 , Wouter van Marken Lichtenbelt 1 ,
1 Department of Human Biology, NUTRIM, Maastricht University, The Netherlands
2 Department of Clinical Neurophysiology, Maastricht University Hospital, The
Netherlands
Contact person: markenlichtenbelt@hb.unimaas.nl
INTRODUCTION
Hypoxia can affect perception of temperature stimuli by impeding thermoregulation at
a neural level and may cause widened zones of thermal comfort. Whether this impact
on the thermoregulatory response is solely due to an affected thermal regulatory
window is not sure, since reaction-time may also be affected by hypoxia. Therefore,
the effect of hypoxia is studied on thermal perception thresholds corrected for
reaction-time.
METHODS
Thermal perception thresholds were determined in 11 healthy adult males using two
methods for small nerve fibre functioning, according to Reulen et al. 2003, with a
thermo-stimulator (Medoc TSA 2001, Ramat Yishai, Israel). The measurement
procedure is based on both reaction-time inclusive method of limits (MLI) and
reaction time exclusive method of levels (MLE). MLI is characterised on an
increasing or decreasing stimulus temperature with a constant rate of change. MLE is
characterised by confirming or denying a temperature.
Before the thermal threshold tests were conducted, the acclimatized subjects stayed
overnight (8h) in a hypoxic tent system (Colorado Altitude Training) under normoxic,
respectively hypoxic (4000 m) conditions. Measurements were performed in the early
morning in the tent.
RESULTS
Methods of limits: Cold sensation threshold under normoxia decreased significantly
from 30.3±0.4 ºC (mean±SD) to 29.9±0.7 ºC when exposed to hypoxia (p < 0.05).
Mean warm sensation threshold increased from 34.0±0.9 ºC to 34.5 ±1.1 ºC (p <
0.05).
Methods of levels: The threshold for cutaneous sensation of cold measured was
31.4±0.4 ºC and 31.2±0.9 ºC for normoxia and hypoxia (not significant, p > 0.05). No
significant change in the sensation of warm threshold was observed in normoxic
conditions (32.8±0.9 ºC) compared to hypoxic conditions (32.9±1.0 ºC) (P > 0.05).
DISCUSSION
The observed diminished cutaneous temperature threshold sensitivity that is caused by
exposure to normobaric hypoxia is a result of an increase in reaction time.
REFERENCES
Reulen, J.P., Lansbergen M.D., Verstraete E., Spaans F., 2003. Comparison of
thermal threshold tests to assess small nerve fiber function: limits vs. levels. Clin.
Neurophysiol. 114: 556-563
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