TABLE 1

Exhaled carbon dioxide detected with four machines and three circuit configurations

Circuit	Breas Vivo 50	Breas NIPPY 3+	Philips Respironics A40	ResMed AirSense CPAP
Exhalation port	2.9	3.1	3.2	3.7
Active valve
0 cmH₂O PEEP	2.1	1.6
4 cmH₂O PEEP	1.5
Vented mask	2.7	2.8	2.7	3.6

Data are given in kPa. CPAP: continuous positive airway pressure; PEEP: positive end-expiratory pressure.