Effects of ambient temperature and altitude on ventilation and gas exchange in deer mice (Peromyscus maniculatus)

Summary

The effects of different ambient temperatures (T _a) on gas exchange and ventilation in deer mice (Peromyscus maniculatus) were determined after acclimation to low and high altitude (340 and 3,800 m).

At both low and high altitude, oxygen consumption ($\dot V_{O_2 }$) decreased with increasingT _a atT _a from −10 to 30 °C. The$\dot V_{O_2 }$ was 15–20% smaller at high altitude than at low altitude atT _a below 30 °C.

Increased$\dot V_{O_2 }$ atT _a below thermoneutrality was supported by increased minute volume ($\dot V{\text{I}}$) at both low and high altitude. At mostT _a, the change in$\dot V{\text{I}}$ was primarily a function of changing respiration frequency (f); relatively little change occurred in tidal volume (V _T) or oxygen extraction efficiency (O₂EE). AtT _a=0 °C and below at high altitude,$\dot V{\text{I}}$ was constant due to decliningV _T and O₂EE increased in order to maintain high$\dot V_{O_2 }$.

At high altitude,$\dot V{\text{I}}$ (BTP) was 30–40% higher at a givenT _a than at low altitude, except atT _a below 10 °C. The increased$\dot V{\text{I}}$ at high altitude was due primarily to a proportional increase inf, which attained mean values of 450–500 breaths/min atT _a below 0 °C. The$\dot V{\text{I}}$ (STP) was equivalent at high and low altitude atT _a of 10 °C and above. At lowerT _a,$\dot V{\text{I}}$ (STPD) was larger at low altitude.

At both altitudes, respiratory heat loss was a small fraction (<10%) of metabolic heat production, except at highT _a (20–30 °C).