Recovery of Alertness After CPAP in Apnea: Results

16 Jan

Recovery of Alertness After CPAP in Apnea: ResultsThe three groups were not different at baseline for sleep parameters or sleep-related respiratory and oxygenation measurements. Sleep stage measurements before and after treatment for the one-night, 14-night and 42-night groups are presented in Table 1. The analysis of the sleep stage data shows that the main effect of treatment was significant but that the treatment duration and the interaction of the two factors were not. The pretreatment diagnostic polysomnogram revealed the disruptive effects of OSAS as evident in the dramatic alterations in normal sleep architecture. The percentage of stage 1 sleep was elevated, while the percentages of stage 2, stage 3/4, and stage REM were greatly reduced. Following CPAP treatment, sleep stages all were improved, with a significant decrease in percentage stage 1 and significant increases in percentage stage 2, 3/4, and REM (p<.001). The recovery of normal sleep staging occurred on the first night of treatment and showed no further improvement.

The pretreatment disturbance of sleep in the three groups is related to the presence of continuous obstructive respiratory events. The baseline values of REI and the associated changes in oxygen saturation were similar among the three groups (Table 2). As with sleep stages, the only significant effect was the main effect of treatment. The mean baseline value for the REI of the three groups was 73, which significantly decreased to a mean value of 10 after CPAP (F = 387.7; df = 1.36; p <.001). Pretreatment nocturnal Sa02 fell below 85 percent for 15.2 min per h of TST and significantly improved to 5.9 min with CPAP (F = 43.4; df= 1.36; p C.001).
The MSLT results for the three groups of patients are presented in Figure 1. As with all other parameters, the baseline values do not differ among the three groups. The mean latency to sleep onset for the one-night group is 3 min, for the 14-night group 3.4 min, and for the 42-night group 4.1 min. These levels of daytime somnolence indicate a pathologic and potentially disabling sleepiness. Following treatment with CPAP, daytime alertness significantly improved (F = 61.1; df=1.36; p <.001). However, unlike all of the nocturnal parameters (which only showed a main effect of treatment), the MSLT results showed a duration of treatment (F = 5.29; df = 2.36; p < .01) and an interaction of treatment and duration (F = 3.29; df=2.36; p <.05). Post hoc comparisons (Duncan) showed a significant increase in mean MSLT after one night of CPAP (p <.01). After one night of CPAP, mean MSLT increased to 6 min, a significant improvement (p <.01). Following two weeks of therapy, the level of daytime sleepiness continued to improve significantly as shown by significant differences from baseline as well as the one-night values (p <.01). The increase after two weeks to 9.6 min places patients in the functionally alert range. The extension of treatment for an additional four weeks did not yield further significant improvement.
Table 1 Sleep Stage Barometers: Before and After CPAP Treatment m 1-, 14-, and 42-Night Groups

Treatment Duration Group
1 Night14 Nights42 Nights
Pre412.5 ±55.9415.9 ±45.0415.1 ±49.6
Post*383.2 ±65.0405.0 ±39.6389.9 ±75.8
% Stage 1
Pre67.1 ±19.161.6±23.754.4±21.7
Post*18.9 ±10.418.6 ±12.619.5 ±12.5
% Stage 2
Pre23.8± 18.526.9 ±17.734.8±22.1
Post*50.1 ±14.755.6 ±14.152.1 ±10.6
% Stage 3/4
Pre0.0.74 ±1.41.3± 1.9
Post*10.5 ±10.54.8 ±7.09.9±9.6
% Stage REM
Pre9.2 ±6.410.7±6.39.5 ±5.5
Post*20.4±8.720.9 ±4.318.5 ±7.9

Table 2—Sleep-related Bespiratory Barometers Before and After CPAP Treatment in 1-, 14-, and 42-Nigjht Groups

Treatment Duration Group
1 Night14 Nights42 Nights
BM135.6±9.537.9 ±6.541.1 ±9.3
Pre72.9±21.572.0 ±16.779.1 ±20.1
Post*12.7 ±10.710.8± 11.56.5 ±9.2
Min <85/h TST
Pre16.5 ±16.614.2 ±10.414.8 ±13.6
Post*7.2± 14.53.2± 11.4.01 ±.03
Times <85/h TST
Pre42.7 ±28.645.9 ±29.644.7 ±32.7
Post*13.6±27.23.6 ±12.5.09 ±.03


Figure 1. Mean latency to sleep (min) before (pre) and after (post) 1,14, and 42 nights of CPAP treatment. * vs pretreatment p <.01, Omnibus F test; ** vs 1 night group p <.01 Duncans post hoc.

Figure 1. Mean latency to sleep (min) before (pre) and after (post) 1,14, and 42 nights of CPAP treatment. * vs pretreatment p <.01, Omnibus F test; ** vs 1 night group p