Author Question: An increase in peak inspiratory pressure (PIP) without an increase in plateau pressure (Pplateau) is ... (Read 81 times)

elizabeth18 · **on:** Jul 16, 2018

An increase in peak inspiratory pressure (PIP) without an increase in plateau pressure (Pplateau) is associated with which of the following?

a. Increase in static compliance (CS)
b. Decrease in static compliance (CS)
c. Increase in airway resistance
d. Decrease in airway resistance

Question 2

The values below pertain to a patient who is being mechanically ventilated with a measured ex-haled tidal volume (VT) of 700 mL.

Time Peak Inspiratory Pressure (cm H2O) Plateau Pressure (cm H2O)
0800 35 30
1000 39 34
1100 45 39
1130 50 44

Analysis of this data points to which of the following conclusions?
a. Airway resistance is increasing.
b. Airway resistance is decreasing.
c. Lung compliance is increasing.
d. Lung compliance is decreasing.

lauravaras · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: C
The PIP represents the amount of pressure needed to overcome both elastance and airway re-sistance. The Pplateau is the amount of pressure required to overcome elastance alone. Since the Pplateau has remained constant in this situation, the static compliance is unchanged. The difference between the PIP and the Pplateau is the transairway pressure (PTA) and represents the pressure re-quired to overcome the airway resistance. If PTA increases, the airway resistance is also increasing, when the gas flow rate remains the same.

Answer to Question 2

ANS: D
To evaluate this information the transairway pressure (PTA) is calculated for the different times: 0800 PTA = 5 cm H2O, 1000 PTA = 5 cm H2O, 1100 PTA = 6 cm H2O, and 1130 PTA = 6 cm H2O. This data shows that there is no significant increase or decrease in this patient's airway resistance. Analysis of the patient's plateau pressure (Pplateau) reveals an increase of 15 cm H2O over the three and a half hour time period. This is directly related to a decrease in lung compliance. Calculation of the lung compliance (CS = VT/(Pplateau EEP) at each time interval reveals a steady decrease from 20 mL/cm H2O to 14 mL/cm H2O.