Page 409 - Clinical Application of Mechanical Ventilation

Management of Mechanical Ventilation 375

Identify the normal values and describe methods to provide normal fluid
balance, electrolyte balance, and nutrition.
Describe the rationale and procedure to initiate: low tidal volume, prone
positioning, and tracheal gas insufflations.

INTRODUCTION

The primary function of mechanical ventilation is to support the ventilatory and oxygen-
ation requirement of a patient until such time that the patient becomes self-sufficient.
During mechanical ventilation, it is essential to maintain a patient’s acid-base balance,
nutritional and resting needs, and fluid and electrolyte balance, because these factors
can affect management strategies of mechanical ventilation and patient outcome.
This chapter discusses strategies to provide optimal ventilation and oxygenation
during mechanical ventilation, as well as other methods to maintain essential physi-
ologic functions through nutritional, fluid, and electrolyte support.

BASIC MANAGEMENT STRATEGIES

The primary goals of mechanical ventilation are to improve ventilation and oxygen-
ation. Essentially all ventilators incorporate designs and features with these two goals
in mind. Besides the many modes of ventilation that are available, common settings
that are available in most ventilators include frequency (f), tidal volume (V ), fraction
T
of inspired oxygenation concentration (F O ), positive end-expiratory pressure (PEEP),
I
2
pressure support ventilation (PSV), and pressure gradient (DP). These settings and
their intended effects on ventilation and oxygenation are summarized in Table 12-1.

TABLE 12-1 Effects of Ventilator Setting Changes on Ventilation and Oxygenation When Changes Are Indicated

Setting Ventilation* Oxygenation**

c Frequency (f) c c c

c Tidal volume (V ) c c c
T
c Fraction of inspired oxygen Unchanged or T c c
concentration (F O )
I
2
c Positive end-expiratory pressure (PEEP) Unchanged or T c c

c Pressure support ventilation (PSV) c c c

c Pressure gradient (DP) (e.g., Bilevel c c c
positive-airway pressure, airway pres-
sure release ventilation)

* c Ventilation = T PaCO 2 ; T Ventilation = c PaCO 2
** c Oxygenation = c PaO 2 , c SpO 2 , c SaO 2
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