Fig. (8) Illustration of the Tritube^® used in conjunction with the Ventrain^® and attached to a test lung. A manometer connected to the Tritube^®’s pressure measurement lumen enables continuous monitoring of intratracheal pressures. In this arrangement the test lung pressure ranges from a minimum of 6.1 cm H₂O (PEEP) (top image) to a peak inspiratory pressure of 20.5 cm H₂O (bottom image).