Page 594 - Clinical Application of Mechanical Ventilation

560 Chapter 17

volume. This requires that time constants be low to allow exhalation and prevent
HFPPV increases the risk air trapping. Continuous monitoring of PaCO and PaO will help the practitioner
of barotrauma and cardiac 2 2
compromise. achieve the frequency needed to attain the desired minute ventilation.
Hazards. As the frequency of positive pressure breaths increases, the mean airway
pressure (mPaw) increases concurrently. The increasing mPaw greatly heightens
mean airway pressure (mPaw): the risk for barotrauma and cardiac compromise. The neonate is also at a higher risk
The average airway pressure during
a complete respiratory cycle. It is of developing intracranial bleeding with increasing mPaw. The ability to suction the
directly affected by the respiratory airway is diminished, as even short-term removal from the ventilator may result in
frequency, inspiratory time, peak
inspiratory pressure, and positive severe hypoxemia and hypercapnia.
end-expiratory pressure.
f * I time
mPaw = s a b * (PIP - PEEP2 t + PEEP
60
See Appendix 1 for
example. mPaw: Mean airway pressure
f: respiratory frequency
I time: Inspiratory time
PIP: Peak inspiratory pressure
PEEP: Positive end-expiratory pressure
High Frequency Jet Ventilation (HFJV)

High frequency jet ventilators generally operate at frequencies between 240 and
high frequency jet ventilation
(HFJV): Ventilation through a spe- 660/min (4 to 11 Hz). The high frequency jet ventilator delivers a high pressure
cially designed endotracheal tube,
generally at a frequency between pulse of gas to the patient’s airway. This is done through a special adaptor attached
240 and 660/min (4 to 11 Hz). to the endotracheal tube, or through a specially designed endotracheal tube that
allows the pulsed gas to exit inside the endotracheal tube, depicted in Figure 17-2.
Indications. The indications for using HFJV include severe pulmonary disease that
The indications for
using HFJV include severe is complicated by air leaks, such as pulmonary interstitial emphysema (PIE), pul-
pulmonary disease that is
complicated by air leaks and monary hypoplasia, restrictive lung disease, and persistent pulmonary hypertension
other pulmonary problems. (Gordin, 1989).

Attachment for HFJV
Distal Airway Pressure
Measurement

Jet Ventilation Exit Measurement of
© Cengage Learning 2014
Distal Airway Pressure

Figure 17-2 The high frequency jet ventilator (HFJV) delivers a high pressure pulse of gas to
the patient’s airway through a specially designed endotracheal tube that allows the pulsed gas to
exit inside the endotracheal tube.

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