Pulmonary artery and intestinal temperatures during heat stress and cooling.
OBJECTIVE
In humans, whole body heating and cooling are used to address physiological questions where core temperature is central to the investigated hypotheses. Core temperature can be measured in various locations throughout the human body. The measurement of intestinal temperature is increasingly used in laboratory settings as well as in athletics. However, it is unknown whether intestinal temperature accurately tracks pulmonary artery blood temperature, the gold standard, during thermal stimuli in resting humans, which is the investigated hypothesis.


METHODS
This study compared pulmonary artery blood temperature (via thermistor in a pulmonary artery catheter) with intestinal temperature (telemetry pill) during whole body heat stress (n = 8), followed by whole body cooling in healthy humans (mean ± SD; age = 24 ± 3 yr, height = 183 ± 8 cm, mass = 78.1 ± 8.2 kg). Heat stress and subsequent cooling were performed by perfusing warm followed by cold water through a tube-lined suit worn by each subject.


RESULTS
Before heat stress, blood temperature (36.69°C ± 0.25°C) was less than intestinal temperature (36.96°C ± 0.21°C, P = 0.004). The increase in blood temperature after 20 min of heat stress was greater than the intestinal temperature (0.70 ± 0.24 vs 0.47 ± 0.18, P = 0.001). However, the increase in temperatures at the end of heat stress was similar between sites (blood Δ = 1.32°C ± 0.20°C vs intestinal Δ = 1.21°C ± 0.36°C, P = 0.30). Subsequent cooling decreased blood temperature (Δ = -1.03°C ± 0.34°C) to a greater extent than intestinal temperature (Δ = -0.41°C ± 0.30°C, P = 0.04).


CONCLUSIONS
In response to the applied thermal provocations, early temperature changes in the intestine are less than the temperature changes in pulmonary artery blood.
Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas, Dallas, TX, USA.
James
J
Pearson
Matthew S
MS
Ganio
Thomas
T
Seifert
Morten
M
Overgaard
Niels H
NH
Secher
Craig G
CG
Crandall
D001831:Body Temperature / Q000502:physiology*; D002404:Catheterization; D003080:Cold Temperature; D018882:Heat Stress Disorders / Q000503:physiopathology*; D006801:Humans; D007422:Intestines; D008297:Male; D011651:Pulmonary Artery; D013686:Telemetry; D013821:Thermometers; D055815:Young Adult