VII.
T H E O R Y O F O P E R A T I O N - C O N T .
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D- CPAP (Continuous Positive Airway Pressure)
In the CPAP mode, the breaths are delivered in exactly the same manner as a spontaneous breath in the SIMV mode. Each
breath is triggered by the patient’s inspiratory effort. Gas flows to the patient for a period of time equal to the inspiratory
time of a normal assisted breath (established with the Tidal Volume and Flow controls). The flow rate during a CPAP
breath is set with the Flow control. During CPAP breaths, PIP is inactive and the gas is delivered at zero or CPAP
pressure. The full volume is made available at the proximal airway, with additional boluses available with continued effort
until the patient is satisfied. Whatever gas is not inspired by the patient is vented to atmosphere.
Pressure Support: See SIMV above.
When Constant Flow is on, the gas flows to the patient continuously rather than being triggered on by the patient. The
flow rate is set by the Flow control and is provided at the CPAP level.
WARNING: IT IS EXTREMELY IMPORTANT THAT THE FLOW TRIGGER
CONTROL BE CAREFULLY ADJUSTED TO ASSURE PROPER OPERATION
IN THE CPAP MODE.
WARNING: UNDER CERTAIN CONDITIONS IN CPAP, IN PARTICULAR
WITH HIGH FLOWS AND LOW CPAP PRESSURES, IF THE LOW PEAK
PRESSURE ALARM IS SET SO THAT NO FALSE ALARMS OCCUR, THIS
ALARM MAY BE INOPERATIVE IF A DISCONNECT OCCURS. IT IS
THEREFORE EXTREMELY IMPORTANT TO HAVE THE LOW PEEP/CPAP
AND LOW EXHALED TIDAL VOLUME ALARMS SET CORRECTLY.