Figure 3. Physiological responses to inspiration of hypoxic air.

Acute hypoxia (10% oxygen for 60 s) increased phrenic nerve activity (PND) and integrated sympathetic nerve activity (int. SNA), with variable effects on MAP in a control rat (A) and a rat exposed to CIH (B). The increase in PND rate was comparable between groups (C). In contrast, the increases in PND amplitude (D) and in SNA (E) were exaggerated in rats exposed to CIH (n = 11) compared to control rats (n = 9). *Significantly different from control rats, P < 0.05, unpaired t test.