Chest
Volume 118, Issue 4, October 2000, Pages 1018-1024
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Clinical Investigations
SLEEP AND BREATHING
Association of Body Position With Severity of Apneic Events in Patients With Severe Nonpositional Obstructive Sleep Apnea

https://doi.org/10.1378/chest.118.4.1018Get rights and content

Study objective:

To compare the severity of sleepapneic events occurring in the supine posture vs the severity of sleepapneic events occurring in the lateral posture in patients with severeobstructive sleep apnea (OSA).

Design:

A retrospectiveanalysis of apneic event variables in a group of 30 OSA patients whounderwent a complete polysomnographic evaluation in our sleep disordersunit.

Patients:

Thirty patients with severe OSA(respiratory disturbance index [RDI] = 70.1 ± 18.2) who werenonpositional patients (NPP), ie, in whom the ratio of the supine RDI to the lateral RDI is < 2 (supineRDI = 85.7 ± 11.7, lateral RDI = 64.8 ± 17.3), and who had≥30 apneic events in the lateral position and 30 apneic events inthe supine position during sleep stage 2 were included in thestudy.

Measurements:

For the 30 apneic events in eachbody position, the following variables were evaluated: apnea duration(ApDur), minimum desaturation (MinDes), Δ desaturation (Δ-Des),duration of arousal (DurArous), maximum snoring loudness (MaxSL), and Δheart rate (Δ-HR). In addition, three other variables assessed asa ratio of ApDur (Rate-D = Δ-Des/ApDur, R-HR =Δ-HR/ApDur, andR-Arous = DurArous/ApDur) were also calculated.

Results:

For all variables evaluated, apneicevents occurring in the supine posture were significantly more severethan those apneic events occurring in the lateral posture during sleepstage 2. ApDur of both body postures correlated significantly withDurArous, Δ-HR, and MaxSL, but not with Δ-Des and MinDes. ApDurcorrelated linearly with DurArous for both postures. The slopes of thetwo regression lines were similar (p = 0.578) but the regression lineintercept for the supine apneas was significantly higher than that of lateral apneas (p < 0.0001). In addition, the average number of supine apneic events that did not end with an arousal was smaller thanthe average number of lateral apneic events not ending with an arousal(4.4 ± 6.0 vs 10.5 ± 6.7, respectively; p < 0.0001). Also, only 4 of 900 (0.44%) apneic events analyzed in the lateral postureended with an awakening (> 15 s), whereas in the supine posture, there were 37 (4.1%) such events (p < 0.001).

Conclusions:

These results show that even in patients withsevere OSA who have a high number of apneic events in the supine andlateral posture, the apneic events occurring in the supine position are more severe than those occurring while sleeping in the lateralposition. Thus, it is not only the number of apneic events that worsenin the supine sleep position but, probably no less important, thenature of the apneic events themselves.

Section snippets

Patients

The polysomnograms of NPP with severe OSA who underwent acomplete polysomnography (PSG) evaluation in our sleep disorders unitwere reviewed. To find 30 polysomnograms without major artifacts andwith ≥ 30 apnea episodes in the lateral position and 30 apneaepisodes in the supine position during sleep stage 2, we had to reviewPSG records of 92 consecutive OSA NPP diagnosed in our sleep disordersunit. The 30 apneic events in each position included samples of 10consecutive apneic events in the

Results

Table 1summarizes the comparison of severity variables for apneic eventsoccurring in the supine posture vs apneic events occurring in thelateral posture. For each of the variables evaluated (unadjusted andadjusted for ApDur), apneic events occurring in the supine posture werefound to be significantly more severe than apneic events occurring inthe lateral posture during sleep stage 2.

Table 2showed the Pearson correlation coefficients between ApDur and the othermeasures of apnea severity. ApDur

Discussion

The results of this study demonstrate that in patients with severeOSA, who have a large number of apneic events in both the supine andthe lateral posture, the apneic events occurring in the supine postureare more severe than the apneic events occurring in the lateralposture. The difference in the degree of severity between apneic eventsin both postures was consistent for all apnea variables analyzed. Thesedata of 30 NPP with severe OSA relate to apneic events occurring duringsleep stage 2

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    This work was performed at the Sleep Disorders Unit, LoewensteinHospital—Rehabilitation Center, Raanana, Israel.

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