Positive end-expiratory airway pressure does not aggravate ventilator-induced diaphragmatic dysfunction in rabbits

Table 3 In vitro diaphragm muscle contractile properties with various modes of mechanical ventilation, with and without applied positive end-expiratory airway pressure ^a

	Control	CPAP	CPAP-8	AMV	AMV-8	CMV	CMV-8
Lo (cm)	3.2 ± 0.1	3.1 ± 0.1	3.4 ± 0.1	3.2 ± 0.1	3.2 ± 0.2	2.9 ± 0.2	3.2 ± 0.1
TPT (ms)	67 ± 3	68 ± 3	73 ± 9	71 ± 3	71 ± 2	70 ± 4	66 ± 6
RT_1/2 (ms)	84 ± 4	116 ± 11	115 ± 17	98 ± 5	96 ± 5	118 ± 8	89 ± 11
Ptw (N/cm²)	7.4 ± 0.5	5.9 ± 0.5	6.0 ± 0.8	6.2 ± 0.8	7.2 ± 0.6	5.7 ± 0.9	3.7 ± 0.4^b
Po (N/cm²)	24.3 ± 0.4	23.3 ± 1.0	23.0 ± 1.6	22.6 ± 0.8	23.0 ± 1.1	15.8 ± 1.0^c	15.0 ± 1.1^c

^aValues are mean ± SE (n = 6 animals in each group). Ptw and Po are normalized for cross-sectional area (see Material and methods for calculation). AMV, Assist-control mechanical ventilation; CMV, Controlled mechanical ventilation (numerical value of 8 next to ventilatory mode denotes the set CPAP or PEEP of 8 cmH₂O); CPAP, Continuous positive airway pressure; Lo, Length at which diaphragm muscle strip produced maximal isometric tension; Po, Maximum tetanic force; Ptw, Peak twitch force; RT_1/2, Time required for peak twitch force to relax to one-half of peak twitch force; TPT, Time from onset of muscle contraction to peak twitch force. ^bFor Ptw, P < 0.01 for CMV-8 compared with control and AMV-8. ^cFor Po, P < 0.01 for CMV compared with control, CPAP and AMV, as well as for CMV-8 compared with control, CPAP-8 and AMV-8.

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