Page 600 - Clinical Application of Mechanical Ventilation

566 Chapter 17

a lower initial mPaw is used for nonhomogenous lung disease. Changes should be
made in increments of 1 to 2 cm H O unless the PO demands require dynamic
2
2
changes for increasing or decreasing the mPaw. When lung compliance and oxy-
genation improve, a subtle drop in the mPaw may be observed.
During weaning, changes in the mPaw should be done every 6 hours, more often
if rib expansion of greater than nine ribs posterior continues.
Flow. The initial flow settings are 20 L/min for infants weighing more than 2,000 g.
For infants less than 2,000 g, 10 to 15 L/min should be adequate.

Power. The power setting determines the amplitude of oscillation (∆P) and thus the
power: A setting during HFOV
that determines the amplitude of tidal volume and degree of ventilation. In HFOV, the tidal volume produced by
oscillation, tidal volume, and degree
of ventilation. the power setting is less than the deadspace volume. The CO is drawn out actively
2
during oscillation. Initially, the power setting should be increased in increments of
2 to 4 cm H O unless the PCO demands require dynamic changes for increasing
Changes in the 2 2
power setting will affect or decreasing the amplitude.
the mPaw, thus requiring Changes in the power setting will affect the mPaw, thus requiring readjustment
readjustment of the mPaw.
of the mPaw. The piston should be centered continuously when changes are made.
Frequency. The initial frequency setting is 8 to 15 Hz depending on the size of the
The frequency may need infant and the diagnosis. The frequency may need adjustment when changes are
adjustment when changes are made to amplitude or mPaw. The piston should be centered continuously when
made to amplitude or mPaw.
changes are made. Increasing the power (amplitude of oscillation or ∆P) or decreas-
ing the frequency (Hz) increase delivered tidal volume and decrease PaCO .
2
Increasing the power Inspiratory Time %. The inspiratory time % determines the I:E ratio and is usually set at
(amplitude of oscillation or
∆P) or decreasing the 33%. This setting provides an I:E ratio of 1:2. This parameter is not routinely changed.
frequency (Hz) increase
delivered tidal volume and F O . The initial F O may be set at 100%. After stabilization of the patient, the
decrease PaCO 2 . I 2 I 2
F O is titrated to keep SpO between 90% and 95%.
I
2
2
OTHER METHODS OF VENTILATION

There has been much research, development, and use of dual control ventilation.
Dual control refers to a Dual control refers to a breath type that combines the useful features of volume-
breath type that combines the
useful features of volume- controlled ventilation (VCV) and pressure-controlled ventilation (PCV). Typi-
controlled ventilation (VCV) cal VCV delivers a set tidal volume and the breath type has a fixed flow rate. In
and pressure-controlled
ventilation (PCV). high-volume demand situations, insufficient inspiratory flow may lead to patient-
ventilator dysychrony. In PCV, the patient’s flow requirement is supplied instanta-
neously. One major limitation of PCV is inconsistent tidal volume in conditions of
changing airflow resistance and compliance.
Examples of dual control mode that are used in neonatal mechanical ventilation
include pressure-regulated volume control (PRVC), volume-assured pressure sup-
port (VAPS), airway pressure release ventilation (APRV), machine volume (MV),
and volume guarantee (VG). PRVC, VAPS, and APRV are outlined in Chapter 4.
The following sections provide an overview of machine volume, volume guarantee,
and liquid ventilation.

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