(8) Expiratory venturi. The expiratory venturi part of the shuttle valve
assembly shown in figure 1-11 is designed to lower pressures above the exhalation
valve within the shuttle valve assembly. The amount of pressure drop is proportional to
the velocity of flow from the expiratory venturi jet, which is controlled by the expiratory
flow gradient control knob. The expiratory venturi functions actively only during the
expiratory phase of controlled IMV.
Figure 1-11. Expiratory venturi.
Section II. THEORY OF OPERATION
Spontaneous breathing is the breathing rate the patient sets. A continuous flow
of gas is sent through the circuit. Continuous positive airway pressure (spontaneous
breathing) exists within the breathing circuit at all times. This mode is used when the
patient is capable of normal or nearly normal respiration. In spontaneous breathing,
both inspiratory and expiratory phases can be mechanically assisted to increase the
tidal volume during inspiration and enhance the expiratory flow of gases from the lungs
a. Controlled IMV superimposes controlled ventilation upon the patient's
breathing pattern. The patient breathes at his own rate and tidal volume, but at
predetermined intervals receives a breath from the ventilator.
b. The operational procedures printed on the side of the Babybird cabinet serve
as a minimum guide or checkout list. It is not a complete maintenance checkout
procedure, nor is it a complete operating procedure.