Utility and safety of draining pleural effusions in mechanically ventilated patients: a systematic review and meta-analysis

Table 2 Summary of studies of oxygenation after thoracentesis in mechanically ventilated patients

Study	N on MV ^a	PEEP ^b (cm H ₂ O)	Volume Drained (mean ± SD)	Time of Outcome Measurement	Variable	Outcome ^d
						Before	After	P-value
Ahmed 2004	22	Not reported	1,262 ± 762 mL (Initial drainage)	<1 hour before and after drainage	P_aO₂:F_iO₂	245 ± 103	270 ± 101	0.31^c
					A-a Gradient	236 ± 170	211 ± 153	0.52^c
					Shunt Fraction	26.6 ± 15.1	21.0 ± 7.8	0.03
De Waele 2003	24	Not reported	1,077 mL (SD not reported) (Over first 24 hours)	Before and 24 hours after drainage	P_aO₂:F_iO₂	190 ± 84	216 ± 74	0.16^c
Doelken 2006	9	0	1,575 ± 450 mL (Initial drainage)	Immediately before and after procedure	P_aO₂:F_iO₂^e	96 ± 29.7	102 ± 21.9	0.37
					A-a Gradient	226 ± 99.6	217 ± 85.2	0.34
Guinard 1997	36	12 ± 3	n/a	6 to 12 hours post-optimization procedure	Predefined gas exchange response ^d		53% responded
Roch 2005	44	6 ± 2	730 ± 440 mL (first three hours)	Before and 12 hours after drainage	P_aO₂:F_iO₂ (effusion <500 mL) (N = 20)	214 ± 83	232 ± 110	0.47^c
					P_aO₂:F_iO₂ (effusion >500 mL) (N = 24)	206 ± 62	251 ± 91	<0.01
Talmor 1998	19	17 ± 1	863 ± 164 mL (first eight hours)	Immediately before and 24 hours after drainage	P_aO₂:F_iO₂	151.0 ± 66.7	244.5 ± 126.8	<0.0001

^aMV, mechanical ventilation.
^bPEEP, positive end-expiratory pressure.
^cP-value not provided in the original paper; we calculated the P-value based on the data provided, assuming a correlation between the before and after measurements of 0.4
^dP_aO₂ >100 mm Hg on F_iO₂ 1.0 for at least six hours.
^aValues are reported as mean ± standard deviation.
^eOriginal paper reported P_aO₂ but all patients were on F_iO₂ 1.0; we calculated P_aO₂:F_iO₂ from these data.

ISSN: 1364-8535