A neonate is being ventilated with PRVC. The respiratory ...

[PhilipSeeMore]

A neonate is being ventilated with PRVC. The respiratory therapist responds to a low volume alarm. After checking the patient and the ventilator, the respiratory therapist finds no discon-nects. The most appropriate action is which of the following?
 
  a. Draw a sample for arterial blood gas eval-uation.
  b. Increase the target volume.
  c. Put the patient in the PC-CMV mode.
  d. Recommend surfactant replacement ther-apy.

Question 2

Which of the following is the term used to describe the exchange of gas between lung units with different time constants?
 
  a. Streaming
  b. Pendelluft
  c. Taylor-type dispersion
  d. Diffusion

[lkoler]

Answer to Question 1

ANS: B
In the PRVC mode, if the ET tube has a leak, the level of support will be reduced; this occurs because the ventilator is sensing more volume is being delivered for a given pressure, when actu-ally the gas is escaping around the cuffless ET tube. With the alarms set properly, this problem is caught. The patient should be switched to the PC-CMV mode, in which the set pressure is not automatically altered by the ET tube leak.

Answer to Question 2

ANS: B
Pendelluft, which is the exchange of gas between lung units with different time constants, is ob-served through photographic studies or by the measurement of different pressure values in the airways.
Streaming, or asymmetric velocity profiles, is thought to occur because the velocity of gas flow is higher in the center of the airway.
Taylor-type dispersion is the enhanced diffusion of gases caused by the turbulence of high gas flows reaching small airways. With this type of enhanced gas transport, simple molecular diffu-sion likely is enhanced as well because more mixing of inspired and expired gas occurs at more distal points in the tracheobronchial tree.