Negative- versus positive-pressure ventilation in intubated patients with acute respiratory distress syndrome

Table 3 Ventilatory pressures during continuous positive-pressure ventilation and continuous external negative-pressure ventilation at inspiration and expiration^a

	Airway pressure (cmH₂O)		Tank pressure (cmH₂O)	Transrespiratory pressure (cmH₂O)	Oesophageal pressure (cmH₂O)		Transpulmonary pressure (cmH₂O)
Patient	CPPV	CENPV	CENPV	CENPV	CPPV	CENPV	CPPV	CENPV
1
Inspiration	33	-3 (27)	-30	27	20	-9 (21)	13	6
Expiration	16	5 (20)	-15	20	15	4 (19)	1	1
2
Inspiration	36	-2 (31)	-33	31	22	-9 (24)	14	7
Expiration	16	5 (20)	-15	20	15	5 (20)	1	0
3
Inspiration	30	0 (31)	-31	31	19	-8 (23)	11	8
Expiration	16	2 (17)	-15	17	15	2 (17)	1	0
4
Inspiration	33	-1 (31)	-32	31	25	-9 (23)	8	8
Expiration	16	4 (19)	-15	19	16	4 (19)	0	0
5
Inspiration	39	-2 (38)	-40	38	23	-10 (30)	16	8
Expiration	16	4 (19)	-15	19	16	3 (18)	0	1
6
Inspiration	47	0 (43)	-43	43	32	-10 (33)	15	10
Expiration	23	5 (24)	-19	24	22	5 (24)	1	0
Mean ± SD
Inspiration	36 ± 6	-1.3 ± 1.2* (33.5 ± 5.9)	-35 ± 5	34 ± 6	24 ± 5	-9 ± 0.8* (25.7 ± 4.7)	13 ± 3	8 ± 1.3^†
Expiration	17 ± 3	4.2 ± 1.2* (19.5 ± 2.3)	-16 ± 1.6	20 ± 2*	17 ± 3	4 ± 1.2* (19.5 ± 2.4)	1 ± 0.5	0 ± 0.5

^aIn parentheses, both airway and oesophageal pressures are shown in reference to tank pressure to enable calculation of transpulmonary pressures (airway pressure - oesophageal pressure) in reference to both atmospheric and body surface pressure inside the tank. Transrespiratory system pressures during CENPV (airway pressure - tank pressure) were compared to airway pressures during CPPV. CENPV, continuous external negative-pressure ventilation; CPPV, continuous positive-pressure ventilation. *P = 0.03 and ^†P = 0.04 compared to the corresponding inspiratory or expiratory value during CPPV.

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