Table 5. Forward stepwise regression analysis: relationship between the decline in pulmonary function and study variables.

Outcome variable	Independent variables	Unstandardized coefficient		P	RR	95%CI
		B	SE
Decline in pulmonary function*	P(A-a)O2 ≥22 mmHg	4.25	1.60	0.001	70.0	3.03-161.3
	Breathing reserve ≤40%	3.03	1.63	0.014	20.8	0.85-507.6

SE = standard error; RR = relative risk; 95%CI = 95% confidence interval; P(A-a)O₂ = alveolar-arterial oxygen pressure gradient at peak exercise. ^*Decrease of >10% from the values initially measured in the forced vital capacity or in the single-breath diffusion of carbon monoxide across the lung.