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RE: Respiratory turbinates and human water loss
On Jan. 3, Terry D. Jones wrote:
>According to our data, and that of others, the savings is 30-40% in
>humans (not 20%).
The total range of percentages of water recovery from the nasal
passages in humans in 20-50% (Walker et al 1961; Cole, 1953). One study,
though (Schmidt-Nielsen, Hainsworth & Murrish, ) found still
smaller savings. Part of this variability is due to differences in
methodology, but a significant portion is due to the well documented
influence of ambient air temperature on exhaled air temperature, and
therefore respiratory water loss (RWL). In general, there is an inverse
relationship between water loss and inspired air temperature (Hoppe, 1981),
so the colder the inspired air, the greater the water savings upon
One of the difficulties in knowing whether or not respiratory
turbinates (RT) function to reduce RWL is that almost no direct measurements
of RWL exist for reptiles. The entire database at present consists of a
single lizard species (Murrish & Schmidt-Nielsen, 1970). The results of
this study indicate that the lizard _Dipsosaurus dorsalis_ can recover up
to 31% of the water that would be lost upon exhalation, at an ambient
temperature of 30C. This value overlaps recorded measurements of water
recovery in humans (see refs above) and also overlaps values for sheep
and wildebeest (24% at about 24C ambient temp.) reported by Langman et al
It's very hard to generalize about RWL in reptiles when only a single
data point exists. However, the fact that _D. dorsalis_ can recover as much
water as some mammals, plus the observation that whales have low rates of
RWL (Kasting et al 1989), despite a lack of RT, suggests, as I have mentioned
in earlier postings, that the primary function of RT may not be to reduce
RWL in endotherms.
Kasting, N. W., Adderley, S.A.L., Safford, T., & Hewlett, K.G.
(1989). Thermoregulation in beluga (_Delphinapterus leucas_) and killer
(_Orcinus orca_) whales. Physiological Zoology, 62 (3), 687-701.
Hoppe, P. (1981). Temperatures of expired air under varying
climatic conditions. International Journal of Biometeorology, 25 (2),
Langman, V.A., Maloiy, G.M.O., Schmidt-Nielsen, K. & Schroter,
R.C. (1979). Nasal heat exchange in the giraffe and other large mammals.
Respiration Physiology, 37, 325-333.
Murrish, D. E., & Schmidt-Nielsen, K. (1970). Exhaled air
temperature and water conservation in lizards. Respiration Physiology,
Cole, P. (1953). Further observations on the conditioning of
respiratory air. Journal of Laryngology and Otology, 67, 669-681.
Walker, J.E.C., Wells, R.E. & Merrill, E.W. (1970). Counter-
current heat exchange in the respiratory passages: effect on water and
heat balance. Respiration Physiology, 9, 263-276.
Dept. of PEHR
Western Washington University
Bellingham, WA 98225