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

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.