Page 230 - Clinical Application of Mechanical Ventilation

196 Chapter 7

TABLE 7-2 Indication and Contraindications for Continuous Positive Airway Pressure

Indication Contraindication

Obstructive sleep apnea Apnea due to neuromuscular causes
Progressive hypoventilation
Fatigue of respiratory muscles
Facial trauma
Claustrophobia
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CPAP is the treatment of choice for obstructive sleep apnea without significant
CPAP is the treatment of carbon dioxide retention (Henderson & Strollo, 1999; Rosenthal, Nykamp &
choice for obstructive sleep
apnea without significant CO 2 Guido et al., 1998). CPAP should be used with care and close monitoring of the
retention. patient as it is not effective in apnea due to neuromuscular causes. Table 7-2 outlines
the indication and contraindications for CPAP therapy.

Obstructive Sleep Apnea

Sleep apnea is defined as a temporary cessation of breathing that lasts at least 10 sec
during sleep (Wilkins & Dexter, 1998). Sleep apnea may be caused by airflow ob-
struction (obstructive sleep apnea), loss of neurologic breathing effort (central sleep
obstructive sleep apnea (OSA): apnea), or a combination of these two conditions (mixed sleep apnea). Obstructive
OSA is caused by severe air flow sleep apnea (OSA) is diagnosed by nocturnal polysomnography and the severity
obstruction during sleep.
is determined by the apnea and desaturation index (Arai et al., 1998; Redline &
Strohl, 1998; Waite, 1998).
apnea index: Average number The severity of OSA is quantified by the apnea index (respiratory disturbance
of apneas in each hour of sleep
during a test. index). The apnea index represents the average number of apneas in one hour of
sleep during a test. For example, if a patient slept for 8 hours during a test and had
160 apneas, the apnea index would be 20 (160/8). Apnea-hypopnea index refers
apnea-hypopnea index: to the average number of apnea or hypopnea in each hour of sleep during a test.
Average number of apnea and
hypopnea in each hour of sleep Desaturation index describes the average number of oxygen desaturations of 4%
during a test. or more from baseline (measured by pulse oximeter) in each hour of sleep during a
test (Mooe et al., 2000).
Approximately 40 million Americans have chronic sleep disorders and the
hypopnea: Reduction in airflow
for 10 or more seconds that is at number of persons affected by OSA ranges from 2% to 4% of middle-aged
least 50% below an estimated
baseline amplitude, usually associ- adults. The distribution between genders is 4% to 9% in men and 1% to 2%
ated with oxygen desaturation or in women. The incidence of OSA among morbidly obese patients is 12 to 30
pulse alteration.
times higher (Kyzer & Charuzi, 1998; Piccirillo et al., 1998; Skomro & Kryger,
1999).
desaturation index: Average Risk factors for OSA include history of snoring and witnessed apneas, obesity,
number of oxygen desaturations of
4% or more from baseline in each increased neck circumference, hypertension, and family history of OSA (Skomro
hour of sleep during a test.
& Kryger, 1999). In patients with OSA, the major clinical signs and symptoms
are snoring, daytime sleepiness, restless sleep, morning fatigue, and headaches. If
untreated, OSA can lead to hypertension, left and right ventricular hypertrophy,

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