Pilbeams Chapter 6 Flashcards
Higher flows
Result in shorter inspiratory times but higher peak pressures and poor gas distribution.
Slower flows
May reduce peak pressures, improve gas distribution and increase airway pressure at the expense of increasing inspiratory times.
Longer expiratory time
Can cause cardiovascular effects
Shorter expiratory time
Can lead to air-trapping.
In general, the goal should be to….
Use the shortest inspiratory time possible
Inspiratory range
(0.8-1.2)
-I/E ratio of 1:2 or 1:4
How to obtain an I:E ratio of 1:2
Flow: 60 Lpm (40 to 80) Lpm
A long inspiratory time has been shown to improve oxygenation in what patients?
ARDS patients
Faster flows are most beneficial in what patients?
COPD and patients with increased airway resistance providing a longer expiratory time which will reduce or prevent air trapping.
What can occur with flows that are set too high?
Uneven distribution of air and cause tachypnea and increased peak pressures.
Rectangular and square flow patterns
Constant Flow pattern provides the shortest ins. times.
A decelerating waveform has the greatest advantage because the flow rate is highest at the beginning of inspiration when patient flow demand is highest.
Descending Ramp
(Pressure ventilation)
Provides a progressive increase in flow, not used by many clinicians.
Ascending Ramp
Produces a tapered flow at the end of the inspiratory phase, not commonly used.
Sine Flow
Descending versus Constant flow
As one changes from a constant to a descending ramp, peak pressure is lower, and the airway pressure is higher.
-Studies suggest that the descending flow ramp pattern improves the distribution of gas in the lungs, reduces dead space and improves oxygenation by increasing the mean and plateau pressures. Also, changing to a descending flow to reduce the peak pressures may increase the Paw.
