. 2020 Feb 14;42(4):420–430. doi: 10.1590/1516-4446-2019-0717

Table 4. Studies assessing CO₂ sensitivity in RS subjects.

Study	CO₂ responders, n	CO₂ nonresponders, n	RS among CO₂ responders, n (%)	RS among CO₂ nonresponders, n (%)	p-value
Nardi20	62	29	43 (69.3)	12 (41.4)	0.022
Nardi21	50	26	31 (62.0)	8 (30.8)	0.011
Nardi22	51	32	38 (74.5)	15 (36.9)	0.008
Freire25	66	51	31 (47)	4 (5.9)	0.001

CO₂ responders = subjects in whom CO₂ induced a panic attack; RS = respiratory subtype.

All studies used the Briggs et al. criteria²⁹ to define RS and double-breath 35% CO₂ inhalation as the CO₂ challenge test.

Table 4. Studies assessing CO2 sensitivity in RS subjects.