TABLE 3

Cardio- and cerebrovascular responses to euoxic isocapnia and hyperoxic hypercapnia in young healthy (Younger), older healthy (Older) and chronic obstructive pulmonary disease (COPD) subjects

	*Younger*		*Older*		COPD
	Saline	Vitamin C	Saline	Vitamin C	Saline	Vitamin C
Euoxic isocapnia
V¯¯_P cm·s⁻¹	67.0±18.1^*	69.1±18.1^*	50.9±9.2	51.7±9.9	50.1±11.9	52.7±11.2
CVC cm·s⁻¹·mmHg⁻¹	0.74±0.21^*	0.78±0.24^*	0.50±0.13	0.51±0.12	0.48±0.12	0.48±0.10
SBP mmHg	123±8^*	121±9^*	140±17	142±14	138±11	144±14
DBP mmHg	73±7^*	74±7^*	86±10	83±8	91±8	95±11^*
MBP mmHg	90±6^*	90±6^*	104±11	103±8	107±7	111±11
f_C beats per min	64±9	64±9	61±8	63±9	73±11^*	75±12^*
Hyperoxic hypercapnia
V¯¯_P cm·s⁻¹	87.5±24.4^*	90.1±25.0^*	65.5±16.5	68.7±17.3	65.8±14.3	68.7±14.3
CVC cm·s⁻¹·mmHg⁻¹	0.92±0.24^*	0.97±0.30^*	0.62±0.18	0.63±0.16	0.57±0.12	0.57±0.11
SBP mmHg	128±10^*	125±11^*	142±15	150±12	150±14^*	157±16^*
DBP mmHg	77±8^*	78±7^*	91±8	90±5	98±8^*	102±8^*
MBP mmHg	94±7^*	94±6^*	108±9	110±4	115±9	121±9^*
f_C beats per min	67±10	67±10	63±9	65±12	74±10^*	76±11^*#

Data are presented as mean±sd. V¯_P: peak cerebral blood flow velocity; CVC: cerebrovascular conductance (CVC=V¯_P/MBP); SBP: systolic blood pressure; DBP: diastolic blood pressure; MBP: mean arterial blood pressure; f_C: cardiac frequency. *: p≤0.5 versus Older under the same condition; ^#: p≤0.05 versus saline, within group.