Table 2.

Relation between arterial/alveolar PO₂ ratio and dead-space components

Surfactant group	Variable	Correlation coefficients
		r	r2	P
Synsurf	VDalv	0.37	0.13	0.2704
	VDalv/VT	0.31	0.10	0.3510
	VDphys	0.94	0.88	0.0000
	VDphys/VT	0.90	0.80	0.0001
Exosurf	VDalv	0.49	0.24	0.0928
	VDalv/VT	0.31	0.10	0.2675
	VDphys	0.93	0.86	0.0000
	VDphys/VT	0.93	0.86	0.0000
Exosurf + Ca2+	VDalv	0.60	0.36	0.0497
	VDalv/VT	0.58	0.33	0.0307
	VDphys	0.85	0.72	0.0006
	VDphys/VT	0.83	0.69	0.0009

Abbreviations: V_Dalv, alveolar dead space; V_Dalv/V_T, alveolar dead-space/tidal volume ratio; V_Dphys, physiologic dead space; V_Dphys/V_T, physiologic dead space/tidal volume ratio.