Comparative effects of flow vs. volume-controlled one-lung ventilation on gas exchange and respiratory system mechanics in pigs

Intensive Care Medicine Experimental

Table 5 Distribution of tidal impedance changes and centre of ventilation in the therapy lung

Parameter	Mode	Therapy			ANOVA (P=)
Group	Mode	20′	40′	60′	Seq	Group	Mode	Time	Mixed
Indepen (%)					0.791	0.596	0.238	0.291	0.791
Normo	VCV	41.4 ± 8.71	41.5 ± 8.45	41.9 ± 8.47
Normo	FCV	41.1 ± 10.5	42.7 ± 10.8	44 ± 10.4
Hypo	VCV	39.1 ± 11	39.4 ± 10.9	38.4 ± 11.3
Hypo	FCV	39.1 ± 11.9	39.7 ± 12.2	40.1 ± 12.8
Semidep (%)					0.922	0.616	0.145	0.437	0.127
Normo	VCV	56.3 ± 7.61	56.2 ± 7.38	55.7 ± 7.34
Normo	FCV	56.4 ± 9.59	54.9 ± 9.91	53.6 ± 9.62
Hypo	VCV	58.1 ± 10.2	57.8 ± 10.2	58.4 ± 10.2
Hypo	FCV	58.1 ± 11.2	57.6 ± 11.6	57.3 ± 12.3
Depend (%)					0.962	0.408	0.698	0.731	0.561
Normo	VCV	2.28 ± 1.25	2.29 ± 1.23	2.31 ± 1.33
Normo	FCV	2.53 ± 1.07	2.4 ± 0.974	2.4 ± 0.927
Hypo	VCV	2.83 ± 1.69	2.83 ± 1.76	2.57 ± 1.75
Hypo	FCV	2.8 ± 1.56	2.63 ± 1.55	2.58 ± 1.55
Centre of ventilation (%)					0.208	0.585	0.103	0.090	0.208
Normo	VCV	60.5 ± 3.88	60.5 ± 3.77	61.2 ± 3.16
Normo	FCV	60.8 ± 3.51	62.2 ± 2.63	62.3 ± 3.09
Hypo	VCV	60.2 ± 4.28	60.4 ± 4.46	60.3 ± 4.68
Hypo	FCV	60.3 ± 5.02	60 ± 4.03	60.4 ± 3.92

Values in mean ± standard deviation; Statistical P values according to linear mixed-effects repeated measures ANOVA with within subject factors: mode of ventilation (volume or flow-controlled ventilation) and time of therapy in minutes; and between subject factors group of therapy (normovolaemia or hypovolaemia) and randomization sequence (volume or flow-controlled ventilation first). Significance was accepted for P < 0.05. Statistical analysis was performed in R statistical programming language and the package lme4
FCV flow-controlled ventilation, VCV volume-controlled ventilation, Indep independent lung regions, semidep semidependent lung regions, dpend dependent lung regions. Centre of ventilation was calculated with the base at dorsal part of the lung. 0% would mean ventilation (change of impedance due to ventilation) is concentrated on the most dependent layer