TABLE 1. Variable Names and Corresponding Questionnaire Items^a.

Variable name	Questionnaire item
constrict	My chest feels/felt constricted
smother	I feel/felt I am/was smothering
notout	My breath does not/did not go out all the way
tight	My chest feels/felt tight
shallow	My breathing is/was shallow
couldnot	I feel/felt that I cannot/could not breathe
work	My breathing requires/required work
notin	My breath does not/did not go in all the way
oob	I feel/felt out of breath
hunger	I feel/felt a hunger for air
heavy	My breathing is/was heavy
effort	My breathing requires/required effort
More b	I feel/felt I am/was breathing more
rapid	I feel/felt my breathing is/was rapid
suffocate	I feel/felt that I am/was suffocating
notenough	I cannot/could not get enough air in

^aAll descriptors scaled from 0-10 (0 = no [absent]; 1 = just barely noticeable; 10 = as intense or severe as that sensation could possibly be). Bold type = descriptors included in 3-factor / 7-indicator measurement model.

^bDeleted from factor analyses because of questionable item performance (cf. Ref. 23).