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

Table 2 Body weight, diazepam dose, total volume of fluid infused, mean arterial pressure and arterial blood gas at baseline and after 2 days 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
Body weight (kg)
Baseline	3.4 ± 0.1	3.7 ± 0.3	3.6 ± 0.4	3.7 ± 0.3	3.4 ± 0.2	3.8 ± 0.4	3.5 ± 0.2
Diazepam dose (mg/kg/h)
		1.2 ± 0.0	1.3 ± 0.1	1.2 ± 0.1	1.3 ± 0.0	1.2 ± 0.1	1.3 ± 0.0
Total volume of fluid infused (ml/24 h)
		408 ± 14	499 ± 30	402 ± 14	517 ± 34^b	421 ± 20	545 ± 7^b
Mean arterial pressure (mmHg)^c
Baseline	84.0 ± 1.4	88.0 ± 3.9	79.9 ± 4.0	87.2 ± 4.1	90.1 ± 5.8	86.8 ± 4.4	82.5 ± 1.2
2 days		97.9 ± 2.3	91.4 ± 4.9	95.6 ± 4.2	93.4 ± 4.3	88.4 ± 4.1	83.6 ± 3.8
Arterial blood gas (pH units)^c
Baseline^d	7.45 ± 0.01	7.43 ± 0.02	7.46 ± 0.02	7.43 ± 0.02	7.45 ± 0.02	7.46 ± 0.03	7.47 ± 0.03
2 days		7.50 ± 0.04	7.48 ± 0.03	7.46 ± 0.02	7.48 ± 0.01	7.51 ± 0.03	7.49 ± 0.02
PaCO₂ (mmHg)
Baseline^d	43.5 ± 2.0	44.3 ± 3.5	46.4 ± 1.5	47.6 ± 2.1	42.1 ± 2.8	47.7 ± 2.9	42.0 ± 3.2
2 days		37.2 ± 3.3	40.7 ± 2.9	35.8 ± 3.6	39.4 ± 2.2	30.5 ± 2.9	42.0 ± 1.2
HCO₃⁻ (mEq/L)
Baseline^d	32.3 ± 1.8	28.5 ± 2.4	35.1 ± 1.3	32.3 ± 2.2	30.6 ± 1.8	33.6 ± 0.6	33.0 ± 2.0
2 days		28.8 ± 1.7	29.7 ± 1.3	26.0 ± 3.0	29.6 ± 1.6	24.3 ± 2.0	32.2 ± 1.7
PaO₂/FIO₂ (mmHg)
Baseline^d	379 ± 24	322 ± 10	375 ± 18	354 ± 17	367 ± 13	354 ± 21	371 ± 20
2 days		384 ± 13	389 ± 13	389 ± 15	384 ± 6	387 ± 12	383 ± 12

^aValues are mean ± SE, except mean ± SD for body weight (n = 6 animals in each group). 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; HCO₃⁻, Bicarbonate; PaCO₂, Partial pressure of carbon dioxide in arterial blood; PaO₂/FIO₂, Ratio of partial pressure of oxygen in arterial blood to fraction of inspired oxygen; PEEP, Positive end-expiratory airway pressure. ^bP < 0.01 for AMV-8 and CMV-8 compared with the corresponding mode without PEEP. ^cData obtained at 12 hours, 24 hours and 36 hours are not shown, but they were included in statistical analysis. ^dBaseline arterial blood gas values were obtained during spontaneous breathing while the animals were under general anesthesia.

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