Page 590 - Clinical Application of Mechanical Ventilation

556 Chapter 17

TABLE 17-5 General Indications for Initiating Neonatal Mechanical Ventilation

1. Apnea
a. due to prematurity
b. secondary to intraventricular hemorrhage
c. due to drug depression

2. PaCO acutely rising with concurrent decrease in pH
2
3. PaO acutely below 50 mm Hg with supplemental oxygen
2
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overcome. It is also indicated when the patient is unable to maintain normal blood
gases during spontaneous breathing. The exact criteria used to determine the need
for mechanical ventilation are difficult to define. Each institution establishes its own
criteria for initiation of mechanical ventilation. Table 17-5 lists general indications
for mechanical ventilation.

Initial Ventilator Settings

The initial ventilator settings depend on several factors, including the gestational
The initial pressure age and weight of the neonate, the disease state present, and the type of ventila-
setting is higher for neonates
with low compliance; lower tor being used. In general, the smaller the neonate, the higher the incidence of
for air leaks. barotrauma. Therefore, it is desirable to initiate these patients at lower pressures
when possible. Disease states in which lung compliance is reduced will require
higher initial pressures than normal or high compliance states. The presence of air
leak requires low pressure and high frequency. Finally, some ventilators may require
a tidal volume to be set by the clinician.

Initial Settings Based on Compliance. With respect to the above factors, Table 17-6
lists suggested starting ventilation based on compliance.
Since the tidal volume (V ) control is not available when using pressure-controlled
T
ventilation, an estimated V can be calculated by multiplying the inspiratory time
T
(I time) and flow rate.
Example: During pressure-controlled ventilation, the I time and flow rate are set
at 0.5 sec and 6 L/m, respectively. What is the calculated V ?
T
V 5 I Time (second) 3 Flow Rate (liters per minute)
T
5 0.5 sec 3 6 L/min
5 0.5 sec 3 6000 mL/60 sec
5 0.5 sec 3 100 mL/sec
5 50 mL
Initial Settings Based on Birth Weight. In addition to the previous settings for neona-
tal mechanical ventilation, alternatives are possible by using the birth weight as a
guide to determine the initial settings. Four primary parameters are discussed here
for volume-controlled ventilation: frequency, inspiratory time, volume, and PEEP.

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