Table 1.

Ventilatory and hemodynamic variables before hypercapnia and after attainment of steady state at rest and during exercise

	Rest		Exercise		P
	Pre	Steady state	Pre	Steady state	Pre vs. steady state	Condition	Interaction
Fraction of inspired CO2, %	0.07±0.01	5.32±0.01	0.05±0.01	5.37±0.08	<0.001	0.604	0.356
HR, beats/min	70±6	73±6	97±8*	112±9†‡	0.002	<0.001	0.002
MCA Vmean, cm/s	51±4	64±4*	60±4*	83±4†‡	<0.001	<0.001	0.01
Minute ventilation, l/min	10.8±0.7	24.9±2.9*	23.6±1.7*	47.0±4.6†‡	<0.001	<0.001	0.009
VT, ml	910±118	1,512±196	1,357±103	2,100±113	<0.001	0.006	0.445
End-tidal PCO2, Torr	37.7±1.8	50.2±1.0	44.5±2.2	59.7±3.2	<0.001	0.003	0.183
Predicted arterial PCO2, Torr	37.4±1.4	47.5±0.8*	42.9±2.0*	54.7±2.7†‡	<0.001	0.013	0.271

Values are means ± SE. HR, heart rate; MCA V_mean, middle cerebral artery mean blood velocity; V_T, tidal volume.

^*P < 0.05 vs. Pre at rest.

^†P < 0.05 vs. steady state at rest.

^‡P < 0.05 vs. Pre during exercise.