Table 2.

Effects of acetazolamide, antioxidants and placebo on normocapnic and hypercapnic hypoxic responses

	Aox group			Placebo group
	Control	Actz	Actz + Aox	Control	Actz	Actx + Aox
Resting ventilation (l min−1)	8.9 ± 0.4	9.3 ± 0.5	9.4 ± 0.4	9.1 ± 0.8	9.4 ± 0.5	9.2 ± 0.3
Resting PET,CO2 (kPa)	5.6 ± 0.1	5.5 ± 0.1	5.3 ± 0.2	5.4 ± 0.2	5.3 ± 0.2	5.2 ± 0.2
Normocapnic experiments
Clamped PET,CO2 (kPa)	5.9 ± 0.1	5.9 ± 0.1	5.9 ± 0.1	5.7 ± 0.2	5.7 ± 0.2	5.7 ± 0.2
Normoxic ventilation (l min−1)	11.1 ± 0.5	12.1 ± 0.8	14.0 ± 0.7c	10.6 ± 0.8	11.7 ± 0.9	13.7 ± 0.6e
Hypoxic ventilation (l min−1)	20.4 ± 0.7	17.0 ± 1.0	22.8 ± 1.0	23.7 ± 0.9	16.8 ± 0.9	19.5 ± 0.9
Hypoxic response (l min−1%−1)	0.65 ± 0.1	0.41 ± 0.0*	0.67 ± 0.1	0.61 ± 0.1	0.41 ± 0.1*	0.46 ± 0.1*
Hypoxic Sa,O2 (%)	85.0 ± 0.8	84.0 ± 0.7	84.8 ± 0.6	85.1 ± 0.8	83.1 ± 0.6	83.0 ± 1.0
Hypercapnic experiments
Clamped PET,CO2 (kPa)	6.4 ± 0.1	6.4 ± 0.1	6.4 ± 0.1	6.2 ± 0.2	6.2 ± 0.2	6.2 ± 0.2
Normoxic ventilation (l min−1)	16.0 ± 0.8	18.1 ± 1.0	20.0 ± 0.8d	15.9 ± 1.0	17.3 ± 1.5	18.2 ± 0.7f
Hypoxic ventilation (l min−1)	27.3 ± 0.8	23.1 ± 1.2	29.8 ± 1.1	27.6 ± 1.1	23.8 ± 1.6	24.3 ± 0.8
Hypoxic response (l min−1%−1)	0.86 ± 0.1†	0.39 ± 0.0*‡	0.74 ± 0.1§	0.82 ± 0.1†	0.44 ± 0.1*,a	0.53 ± 0.1*,b
Hypoxic Sa,O2 (%)	85.1 ± 0.8	85.1 ± 0.6	84.8 ± 1.0	84.6 ± 0.5	82.9 ± 0.8	82.9 ± 0.8

Effect of acetazolamide (Actz) and placebo on resting ventilatory parameters and the acute normocapnic and hypercapnic hypoxic responses. Data are means ± s.e.m. Note that in the Aox group Actz reduces the hypoxic response both in normocapnia and hypercapnia and that these effects are reversed by Aox. In the placebo group, no reversal is seen.

^*P < 0.010 versus control

^†P = 0.0002 versus normocapnia

^‡P = 0.52 versus normocapnia

^§P = 0.02 versus normocapnia

^aP = 0.24 versus normocapnia

^bP = 0.19 versus normocapnia

^cP = 0.004 versus control

^dP = 0.015 versus control

^eP = 0.016 versus control

^fP = 0.015 versus control.