Table 2.

Results table

		Baseline (n = 35)	Acclimatized (n = 35)
Chemosensitivity
HvR1	100–90% $\mathrm{S}{\mathrm{a}}_{{\mathrm{O}}_{\mathrm{2}}}$>	0.26 (0.21)	0.64 (0.54)ab	l·min−1·%sat−1
HvR2	90–80% $S{a}_{O_2}$ (1)	0.12 (0.15)c	0.26 (0.26)ab	l·min−1·%sat−1
HvR3	90–80% $S{a}_{O_2}$ (2)	0.19 (0.20)	0.29 (0.37)	l·min−1·%sat−1
HcvR	(100%)–(100% + CO2)	1.08 (0.95)	1.63 (1.30)ad	l·min−1·Torr−1
HHcvR	(90%)–(90% + CO2)	1.79 (1.09)e	2.21 (2.62)	l·min−1·Torr−1
HcbfR1	100–90% $S{a}_{O_2}$	0.88 (0.75)	0.88 (0.66)	ml·100 ml−1·min−1·%sat−1
HcbfR2	90–80% $S{a}_{O_2}$ (1)	1.03 (0.44)	1.02 (0.52)	ml·100 ml−1·min−1·%sat−1
HcbfR3	90–80% $S{a}_{O_2}$ (2)	0.83 (0.57)	0.99 (0.64)	ml·100 ml−1·min−1·%sat−1
HccbfR	(100%)–(100% + CO2)	1.62 (1.80)	2.74 (1.97)	ml·100 ml−1·min−1·Torr−1
HHccbfR	(90%)–(90% + CO2)	2.51 (1.81)e	4.74 (7.72)	ml·100 ml−1·min−1·Torr−1
Resting V̇ and CBF
V̇100%	HvR1 at 100% $S{a}_{O_2}$	5.88 (1.68)	7.28 (2.37)a	l/min
V̇100% (CO2 reset)	CO2-corrected HcvR		18.47 (19.70)	l/min
V̇85%,HvR2	HvR2 at 85% $S{a}_{O_2}$	8.82 (2.82)	13.58 (6.27)	l/min
V̇85%,HvR3	HvR3 at 85% $S{a}_{O_2}$	7.55 (2.37)	10.89 (4.81)	l/min
∆V̇85%,HvR2– HvR3	HvR2– HvR3 at 85%	1.27 (1.76)f	2.69 (3.30)ad	l/min
CBF100%	HcbfR1 at 100%	57.50 (13.01)	60.98 (14.53)	ml·100 ml−1·min−1
CBF100% (CO2 reset)	CO2-corrected HccbfR		81.08 (32.09)	ml·100 ml−1·min−1
CBF85%,HcbfR2	HcbfR2 at 85% $S{a}_{O_2}$	70.32 (16.21)	73.65 (16.58)	ml·100 ml−1·min−1
CBF85%,HcbfR3	HcbfR3 at 85% $S{a}_{O_2}$	71.10 (16.50)	73.74 (16.32)	ml·100 ml−1·min−1
∆CBF85%,HcbfR2–3	HcbfR2–HcbfR3 85%	−0.78 (3.44)	−0.08 (3.37)	ml·100 ml−1·min−1

Sensitivity of ventilation (V̇) and cerebral blood flow (CBF) to hypoxia and hypercapnia and absolute values of V̇ and CBF breathing different gases before (Baseline) and after acclimatization to 2 days of sustained hypoxia. Data are means (1 SD). HvR1, -2, and -3 and HcbfR1, -2, and -3 are the terms that describe the HvRs to O₂ desaturation from 100 to 90%, 90 to 80%, and 90 to 80% for a second time (respectively; see Fig. 1). H_cvR is the ventilatory sensitivity to an increase in $\mathrm{P}\mathrm{E}{\mathrm{T}}_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}$ by ~5 Torr during normoxia (50). HH_cvR is the ventilatory sensitivity to combined hypoxic and hypercapnic changes [~5 Torr increase in $\mathrm{P}\mathrm{E}{\mathrm{T}}_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}$, $S{a}_{O_2}$ decreased to 90%]. HcbfR, H_ccbfR, and HH_ccbfR are the equivalent sensitivities for CBF. V̇_100% and V̇_85% are ventilation at 100 and 85% $S{a}_{O_2}$, respectively. V̇_{100%(CO2 reset)} defines the equivalent resting ventilation referred back to the baseline CO₂ set point (i.e., “corrected” set point) to assess the full impact on ventilation of both acclimatization and the altered CO₂ set point (see Figs. 4 and 5); ΔV̇_85% defines the change in ventilation due to hypoxic ventilatory decline assessed at 85% saturation between HvR2 and HvR3. Equivalent measurements were made for CBF responses.

^aP < 0.05 (relative to baseline).

^bP = 0.06 (greater change for no-AMS, trend only).

^cP < 0.05 (relative to HvR1 at baseline).

^dP < 0.05 (greater change for no-AMS).

^eP < 0.05 (relative to normoxic hypercapnia at baseline).

^fP < 0.05.