Definition of RERA

Based on our initial investigations on RERAs (4), the development of a calibrated nasal pneumotachograph sensor with a small deadspace that could be comfortably worn throughout the polysomnographic study would be desirable. This sensor was developed by the Johns Hopkins sleep research group. Figure 1 shows the sensor with amplifier, and Figure 2 shows the correlation between values obtained with the sensor in comparison with a pneumotachograph. In Dortmund, we have used this sensor in 158 full-night sleep studies. This sensor allows quantitatively defining RERAs based on our initial investigations of peak inspiratory flow decrement (4).

FIGURE 2 Relationship between a novel flow sensor and pneumotachograph.

This decrement was 43 ± 14% compared to silent unobstructed breathing. The decrement in VT was 22% or 100 mL. These changes were often seen only within the last three breaths prior to arousal. In fact, during the early stages of periods with increased upper airway resistance (namely during slow wave sleep) we noted an increase in VT and VI suggesting a compensated state with higher metabolic demand that ultimately decompensates, leading to arousal from sleep. Based on the above mentioned studies, it seems appropriate to use cannula or pneumotachograph flow decrements of 30% (~ mean -1 SD as reported) (4) and/or esophageal pressure increments with Pes reversal (34) at arousal to determine RERAs when the arousal is taken as endpoint in the chain of events. In comparison to the definition of hypop-nea, the distinct nature of RERA scoring lies in the fact that this event can be shorter than 10 seconds (one or two breaths) (4).

Guilleminault (26,35) and others (36) have suggested that an even subtler central endpoint may exist to increased upper airway resistance during sleep, which is not readily visible to the human eye in polysomnographic recordings. An article published in 2004, however, has challenged the arousal as endpoint for upper airway obstruction during sleep in OSA (37). More studies are needed to better define this endpoint and to develop simple methods for its assessment.

Sleep Apnea

Sleep Apnea

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