Table 1.

Gas composition and inhalation method for each of the six experimental conditions

Condition name	Gas composition	Administration	Respiration rate	Condition code	Scans/subject
CO2FM	8% CO2, 92% O2	FM	Involuntarily high	CO2FM	2
CO2MP	8% CO2, 92% O2	MP	Involuntarily high	CO2MP	2
PB	79% N2, 21% O2	FM	Voluntarily high	PBFM	1
PB	79% N2, 21% O2	MP	Voluntarily high	PBMP	1
O2FM	9% N2, 91% O2	FM	Normal	O2FM	2
Eyes closed rest	79% N2, 21% O2	None	Normal	R	2