The pressure-time scalar shown in the figure could be caused by ...

[saliriagwu]

The pressure-time scalar shown in the figure could be caused by which of the following?
 
  a. Inspiratory hold
  b. Clogged expiratory filter
  c. Excessive secretions in the airway
  d. Negative end expiratory pressure

Question 2

A ventilator is set to deliver a 600 mL tidal volume. The flow rate is set at 40 L/min and the fre-quency is set at 10 breaths/min. If the flow rate is doubled and the patient is not assisting, which of the following will occur?
 
  a. The frequency will decrease.
  b. The tidal volume will increase.
  c. The expiratory time will increase.
  d. The inspiratory time will increase.

[katkat_flores]

Answer to Question 1

ANS: B
What is being shown in the figure is a peak pressure of 20 cm H2O and then a very slow drop in the pressure over the course of approximately 1 second. Normally, as soon as the peak inspiratory pressure is reached, the pressure drops rapidly and remains at baseline until the next breath is given. A clogged expiratory filter will increase the resistance in the filter. This will cause there to be difficulty exhaling through this filter, showing up as a slow drop in pressure during the exha-lation period. An inspiratory hold would cause there to be a plateau in the pressure-time scalar. Excessive secretions in the airway would elevate the peak inspiratory pressure to a point where the maximum safety pressure may be reached. The presence of negative end-expiratory pressure (NEEP) would pull the pressure down rapidly from the peak and drop it slightly below the base-line during that time.

Answer to Question 2

ANS: C
If you manipulate the formula: Flow = Volume change/Time to Volume/Flow = Time, and use the numbers from this example, it can be shown that by increasing the flow rate the inspiratory time will decrease. Since the frequency remains constant, then the inspiratory time will decrease, thereby increasing expiratory time.