Table 1.

Ventilatory and cardiovascular measures for peripheral and central chemoreflex sensitivity in supine position

	Central Chemoreflex				Peripheral Chemoreflex
	Eucapneic normoxia		Hyperoxic hypercapnia		Eucapneic hyperoxia		Eucapneic hypoxia
Supine	Controls	POTS	Controls	POTS	Controls	POTS	Controls	POTS
Arterial oxygen saturation, %	97.5 ± 0.6	97.2 ± 0.2	99.2 ± 0.6	98.9 ± 0.2	99.2 ± 0.6	98.9 ± 0.2	80.8 ± 2.3*	84.7 ± 1.4*†
Minute ventilation, l/min	4.1 ± 0.4	5.5 ± 0.4	20.1 ± 2.4*	14.3 ± 2.1*	6.1 ± 0.9*	6.8 ± 0.6*	6.5 ± 0.6*	7.5 ± 1.0*
Respiratory rate, beats/min	16.7 ± 1.1	16.8 ± 0.7	15 ± 1.0	14.8 ± 0.8	18.6 ± 1.0	16.9 ± 0.9	14.3 ± 0.9	16.9 ± 1.0
ETCO2, Torr	43.0 ± 0.7	42.2 ± 1.0	57.3 ± 4.7*	55.3 ± 6.6*	44.3 ± 1.6	42.2 ± 1.1	43.2 ± 0.8	42.3 ± 2.0
Heart rate, beats/min	63.7 ± 3.2	75.4 ± 3.2	76.5 ± 3.4*	84.5 ± 3.1*	60.1 ± 2.7	72.8 ± 3.7	71.6 ± 3.4	83.5 ± 3.2*
Systolic arterial pressure, mmHg	121.2 ± 2.8	112.7 ± 1.9†	129.6 ± 4.2	125.25 ± 2.7	117.7 ± 3.1	120.3 ± 2.3	116.6 ± 3.1	116.9 ± 1.9
Diastolic arterial pressure, mmHg	62.9 ± 1.7	61.7 ± 1.6	70.3 ± 2.1*	67.9 ± 1.9	62.2 ± 1.9	66.2 ± 2.0	61.4 ± 2.3	64.0 ± 2.2
Mean arterial pressure, mmHg	84.0 ± 1.9	79.0 ± 1.5	93.6 ± 2.5*	88.3 ± 1.9	83.4 ± 2.4	84.1 ± 1.7	81.8 ± 2.6	84.2 ± 1.9
Cardiac output, l/min	4.9 ± 0.4	4.9 ± 0.2	6.2 ± 0.3*	5.6 ± 0.3	5.3 ± 0.4	4.8 ± 0.3	5.8 ± 0.5	5.2 ± 0.3
TPR, mmHg·l−1·min−1	17.9 ± 1.3	16.6 ± 1.1	16.2 ± 1.1	18.2 ± 1.1	16.3 ± 1.1	18.3 ± 1.1	14.8 ± 1.1	17.5 ± 1.1
Stroke volume, ml	81.1 ± 8.1	66.1 ± 2.1†	81.1 ± 5.1	68.1 ± 3.1	93.1 ± 8.1*	69.1 ± 5.1	88.1 ± 11.1	66.1 ± 2.1†

Values are means ± SE.

POTS, postural tachycardia syndrome; ETCO₂, end-tidal CO₂; TPR, total peripheral resistance.

^*P < 0.05 compared with eucapneic normoxia;

^†P < 0.05 compared with controls.