Page 232 - Clinical Application of Mechanical Ventilation

198 Chapter 7

TABLE 7-3 Indications and Contraindications for Noninvasive Positive Pressure
Ventilation

Indication Contraindication
Reduction of respiratory workload in Apnea
obesity

Acute respiratory failure Unable to handle secretions
Acute hypercapnic exacerbations of Facial trauma
COPD
Claustrophobia
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COmmON INTERfACES fOR CPAP ANd BIlEVEl PAP

Since CPAP or NPPV is done without an artificial airway, the interface between
Nasal mask, oronasal the patient and ventilator is typically an external device connecting the ventilator
mask, nasal pillows, and
full-face mask are interfaces tubing to the patient’s nose, mouth, or face. NPPV interfaces include nasal mask,
for NPPV. oronasal mask, nasal pillows, and full-face mask.

Nasal mask

nasal mask: A mask that covers The nasal mask is the most common interface used in NPPV for obstructive
only the nose. sleep apnea. A typical nasal mask has a soft cushion that surrounds and makes
contact with the patient’s nasal area. The soft cushion provides comfort to the
patient while maintaining a seal to keep gas from leaking. While a tight seal is
desirable, a minor leak is acceptable as it is not likely to compromise the effective-
ness of NPPV. A common error is selecting a nasal mask that is too large for the
A minor leak is accept-
able when using a nasal mask. patient. There are many nasal masks available. For patient comfort and compli-
An oronasal mask should be ance, it is a good practice to let the patient try out different sizes for maximal
considered when the leak is
significant. comfort and minimal leakage. Figure 7-1 shows the structure of a typical nasal
mask (A) and when it is in use (B).
Since a nasal mask does not cover the mouth, leakage through the mouth is a
common problem. This is particularly true when PPV is provided at high positive
pressures. A minor leak is acceptable as long as ventilation and oxygenation are not
compromised. An oronasal mask should be considered when the leak is significant
or when ventilation is the primary indication for NPPV. During the initial setup
of a nasal mask, pulse oximetry may be used to check for improvement in oxygen-
ation and adequacy of oxygen saturation. Soon after stabilization of the patient,
blood gases should be done to fine-tune settings on the ventilator so as to verify
proper oxygenation, ventilation, and acid-base balance. Table 7-4 shows the advan-
tages and disadvantages of the nasal mask.

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