Table 2– Physiological parameters during mechanical ventilation (MV) and the spontaneous breathing trial (SBT) among patients with SBT failure or success

	All trials^#			COPD trials^¶
	MV	SBT	p-value⁺	MV	SBT	p-value⁺
f_R breaths·min⁻¹
SBT failure	17±6	24±11	0.009	17±7	20±9	0.11
SBT success	17±4	20±5	0.002	17±4	19±4	0.07
Heart rate beats·min⁻¹
SBT failure	82±20	95±24	0.08	84±23	89±28	0.61
SBT success	88±19	79±32	0.18	89±18	90±32	0.71
P̄_sa mmHg
SBT failure	84±13	99±16	<0.001	87±15	101±16	0.002
SBT success	86±15	98±17	<0.001	89±12	100±17	0.001
P_a,CO₂ mmHg
SBT failure	46±11	50±14	0.13	50±12	56±16	0.24
SBT success	43±8	44±9	0.07	47±9	48±11	0.44
Arterial pH
SBT failure	7.44±0.05	7.37±0.08	0.006	7.43±0.05	7.37±0.09	0.05
SBT success	7.44±0.04	7.42±0.06	0.006	7.43±0.04	7.39±0.06	0.02
P_a,O₂ mmHg
SBT failure	91±19	83±26	0.07	93±18	76±20	0.05
SBT success	101±19	92±26	0.01	102±24	92±32	0.05
f_R/V_T
SBT failure		100±70			58±27
SBT success		73±40			77±35
MIP cmH₂O
SBT failure		42±18			51±21
SBT success		52±19			44±13
MEP cmH₂O
SBT failure		66±29			78±28
SBT success		68±22			68±25

Data are presented as mean±sd, unless otherwise stated. COPD: chronic obstructive pulmonary disease; f_R: respiratory frequency; P̄_sa: mean systemic arterial pressure; P_a,CO₂: arterial carbon dioxide tension; P_a,O₂: arterial oxygen tension; V_T: tidal volume; MIP: maximal inspiratory pressure; MEP: maximal expiratory pressure. ^#: n=49; ^¶: n=23; ⁺: paired comparisons between MV and SBT in each group.