Obstructive sleep apnea syndrome (OSAS) is characterized by repeated
episodes of partial or complete pharyngeal obstruction during sleep. Its
main treatment is ventilation by continuous positive airway pressure
(CPAP), that is applied during sleep. Although the required pressure
changes within each night, a constant pressure is traditionally applied.
By contrast, "autoCPAP" machines deliver continuously variable pressure
levels in relationship to needs automatically identified by their
software. A relationship between sleep stage and pressure delivered by an
autoCPAP has been demonstrated in a previous study of ours. Simply
applying autoCPAP during the night could replace the expensive and complex
titration procedure. Classically, titration is performed during nocturnal
polysomnography by a technician who modifies air pressure until a level
preventing respiratory disorders for almost all night is identified.
AutoCPAP machines provide a wide range of pressure values preventing
respiratory disorders during each night they are applied, so that they
could suggest which constant pressure level could be prescribed, making
polysomnographic monitorings and technical attendance unnecessary.
Besides, treatment by autoCPAP should result in the application of high
pressures only when they are really necessary, so that ventilatory
treatment could become easier to tolerate. As yet, few data about autoCPAP
advantages have been published.
One study is being performed at the IBIM sleep center to verify whether
CPAP titration may be performed by means of an autoCPAP alone and if
technical attendance is necessary during its application. Although in most
of subjects titration by autoCPAP alone was reliable, it was
unsatisfactory in too many of them. Most errors came from an insufficient
sleep duration, that could be demonstrated by electroencephalography
monitoring. Failures due to insufficient correction of respiratory
disorders were identified by oxyhemoglobin saturation monitored by non-invasive oximetry; addition of respiratory movements and oro-nasal airflow
to oximetry did not improve appreciably titration reliability. A
technician in constant attendance proved necessary only in a small
percentage of cases.
In a single-blinded cross-over study, OSAS treatments by fixed-level CPAP
and by autoCPAP were compared. Use of each treatment by the patients,
subjective preference, and possible predictors of greater use and
preference were evaluated. On average, use of the two treatments did not
differ. However, a small number of subjects preferred and used much more
autoCPAP than fixed-level CPAP. Therefore, in a minority of subjects
autoCPAP may be an effective alternative to fixed-level CPAP. As autoCPAP
is more expensive than fixed-level CPAP, it may be considered a second
choice when compliance to fixed-level CPAP is not satisfactory.
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