Table 2.

Baseline (21% O₂ / 0% CO₂) ventilatory and metabolic measurements for adult rats immediately following 4 d and 14 d of chronic hyperoxia (Experiments #2 and 3 combined).

	Female		Male		Statistical comparisons a
	Control	Hyperoxia	Control	Hyperoxia	Treatment (comparison, P)	Sex (comparison, P)
After 4 d in hyperoxia:
n	26	23	18	20
Mass (g)	240±7	234±4	372±13	386±14	n.s.	F<M, <0.001
Tb (°C)	37.2±0.1	37.0±0.1	37.3±0.1	37.1±0.1	H<C, 0.047	n.s.
fr (breaths min−1)	65.3±2.1	63.4±2.2	74.7±2.1	75.3±2.9	n.s.	F<M, <0.001
Vt (ml 100g−1)	0.49±0.01	0.50±0.02	0.35±0.01	0.35±0.01	n.s.	F>M, <0.001
$\stackrel{.}{\mathbf{V}}I$ (ml min−1 100g−1)	31.3±0.8	31.8±1.4	26.0±0.8	25.9±0.9	n.s.	F>M, <0.001
n b	17	14	13	14
$\stackrel{.}{\mathbf{V}}{O}_2$ (ml min−1 100g−1)	1.84±0.11	1.73±0.0.09	1.59±0.07	1.67±0.10	n.s.	n.s.
$\stackrel{.}{\mathbf{V}}{\mathrm{CO}}_2$ (ml min−1 100g−1)	1.48±0.08	1.43±0.08	1.40±0.06	1.51±0.08	n.s.	n.s.
RER	0.82±0.02	0.83±0.02	0.88±0.02	0.91±0.02	n.s.	F<M, <0.001
$\stackrel{.}{\mathbf{V}}I$ / $\stackrel{.}{\mathbf{V}}{O}_2$	17.4±1.1	18.9±1.3	17.2±1.1	16.9±1.2	n.s.	n.s.
$\stackrel{.}{\mathbf{V}}I$ / $\stackrel{.}{\mathbf{V}}{\mathrm{CO}}_2$	21.4±1.2	22.5±1.3	19.5±1.1	18.5±1.2	n.s.	F>M, 0.017
After 14 d in hyperoxia:
n	26	23	19	21
Mass (g)	249±7	243±4	382±13	393±12	n.s.	F<M, <0.001
Tb (°C)	37.3±0.1	37.2±0.2	37.4±0.1	36.8±0.1	H<C, 0.008	n.s.
fr (breaths min−1)	68.0±2.5	57.5±1.7	70.4±2.2	68.2±2.7	H<C, 0.008	F<M, 0.007
Vt (ml 100g−1)	0.50±0.01	0.55±0.02	0.37±0.01	0.40±0.03	H>C, 0.027	F>M, <0.001
$\stackrel{.}{\mathbf{V}}I$ (ml min−1 100g−1)	33.2±1.3	31.0±1.2	25.8±0.6	26.7±1.2	n.s.	F>M, <0.001
n b	18	16	15	19
$\stackrel{.}{\mathbf{V}}{O}_2$ (ml min−1 100g−1)	1.66±0.10	1.87±0.10	1.65±0.11	1.63±0.08	n.s.	n.s.
$\stackrel{.}{\mathbf{V}}{\mathrm{CO}}_2$ (ml min−1 100g−1)	1.46±0.07	1.65±0.10	1.43±0.10	1.42±0.07	n.s.	n.s.
RER	0.89±0.02	0.88±0.02	0.88±0.02	0.87±0.01	n.s.	n.s.
$\stackrel{.}{\mathbf{V}}I$ / $\stackrel{.}{\mathbf{V}}{O}_2$	19.7±1.1	18.2±1.0	16.2±1.1	17.3±0.9	n.s.	F>M, 0.038
$\stackrel{.}{\mathbf{V}}I$ / $\stackrel{.}{\mathbf{V}}{\mathrm{CO}}_2$	21.9±0.9	20.6±1.1	18.3±0.9	19.9±1.1	n.s.	F>M, 0.038

Values are mean±SEM. T_b, body temperature; fr, respiratory frequency; Vt, tidal volume; $\stackrel{.}{\mathrm{V}}I$, minute ventilation; $\stackrel{.}{\mathrm{V}}{O}_2$, O₂ consumption; $\stackrel{.}{\mathrm{V}}{\text{CO}}_2$, CO₂ production; RER, respiratory exchange ratio; $\stackrel{.}{\mathrm{V}}I$ / $\stackrel{.}{\mathrm{V}}{O}_2$, O₂ convection requirement; $\stackrel{.}{\mathrm{V}}I$ / $\stackrel{.}{\mathrm{V}}{\text{CO}}_2$, CO₂ convection requirement.

^aNo significant Treatment × Sex interactions were detected (all P>0.05), so only main effects from the ANOVA model are reported. n.s., nonsignificant; F, Female; M, Male; C, Control; H, Hyperoxia.

^bMetabolism was not assessed for every individual, so sample sizes differed between breathing and metabolism measurements.