Data from six to ten representative consecutive minutes of wakefulness, steady stage 2 non-REM (NREM) sleep (S2), stage 3/4 NREM (S3/4), and REM sleep were obtained for both air and oxygen nights and a mean ± SEM derived. The “minute to minute” within-subject coefficient of variation for each sleep stage was also derived from these data. Comparisons between means were made using the Student t test. life without allergy com
Daytime Pulmonary Function
The mean seated vital capacity of the six subjects was 1.48 L (range, 0.8 to 3.0 L) with a mean fall of 6.7 ( — 3.3 to 20 percent) when supine. The mean total lung capacity was 3.56 L (2.5 to 6.3 L). Residual volume ranged from 1.2 to 3.8 L (mean, 2.18 L) and functional residual capacity from 1.5 to 4.3 L (mean, 2.5 L). Maximum static mouth pressures were low in all subjects, the mean MIP being 37.5 (25 to 65 cm H20) and MEP being 29.2 (15 to 50 cm H20). Daytime blood gas tensions, however, were within normal limits (mean Po2, 14.5 kPa [13.2 to 17.9 kPa]; Pco2, 5.23 kPa [4.7 to 6.05 kPa]).
The mean saturation in NREM sleep was 95.3 (93.5 to 96.5 percent). The mean frequency of desaturations exceeding 5 percent was 1.92 h l (0 to 4.2 h*) of total sleep, the saturation falling to a mean nadir of 80.1 (58 to 93 percent).
In a previous report that included data from four of these subjects, sleeping oxygen saturation was shown to improve markedly with oxygen treatment despite a significant overall prolongation of underlying hypopnea/apnea (HA) events by 19 percent. In the present study, no subject desaturated while breathing oxygen, but the mean proportion of REM sleep occupied by HA rose from 31.3 percent (5 to 49 percent) breathing air to 38.2 percent (9 to 54 percent) breathing oxygen. Mean values of Ve, f, Vt, Vt/Ii, Ti/ Ttot, and AC for the group are given in Table 1. Data from S3/4 usually preceded that from REM sleep, and data from all sleep stages were obtained without a change in patient position. A representative six- to ten-minute consecutive period of stable NREM sleep was available for analysis in all subjects, but the period of REM sleep analyzed was interrupted by NREM sleep in two subjects. Where brief periods of arousal (<20 s) occurred following desaturations in REM sleep, this was still taken to represent a continuous period of REM sleep.
The Ve was significantly lower in both S3/4 and REM sleep compared with wakefulness on both air and oxygen owing to falls in both Vt and f. The Vt/R was also reduced from awake values in both S3/4 and REM sleep, but this difference was significant only with oxygen. Abdominal paradoxical movement, present intermittently when awake and persisting into NREM sleep, was observed in one subject, and another had abdominal paradox develop only in NREM sleep (Fig 1). The mean values of abdominal (diaphragmatic) contribution during S3/4 NREM sleep while breathing air ranged between 35 percent and — 27 percent (Table 1); a relationship (p<0.05) existed between these NREM abdominal contributions and the extent of oxygen desaturation that subsequently occurred in REM sleep (Fig 2).
Table 1—Mean±SD Minute Volume (VeJ, Frequency (f\ Tidal Volume (Vt), Mean Inspiratory Flow (Vr/Ti), Respiratory Duty Cycle Time (TeJTtotX and Abdominal Contribution (AC) to Breathing During ‘Wakefulness, Stage 2 NREM (S2 NREMX Stage 3-4 NREM (S3!4 NREM% and REM Sleep on Air and Oxygen (Bold Type) in the Six Subjects with Duchenne MD
|VE (L min)||6.9± 1.8||5.1 ±0.6||4.9±0.8t||4.5 ± 1.5t|
|6.4 ±0.9||5.1 ±0.7||4.7 ±0.6**||4.3 ±0.7**|
|f(min~‘)||17.6 ±4.1||14.2 ±0.9||14.5± 1.0||13.0 ±4.4|
|16.0 ±3.0||13.5±1.34||13.4 ±0.9||12.6 ±3.6|
|VT (L)||0.4 ±0.1||0.4 ±0.1||0.3 ±0.1||0.4 ±0.1|
|0.4±0.1||0.4 ±0.02||0.35 ±0.04||0.35±0.1|
|VT/Ti(L min)||16.9 ±3.4||13.7±3.4||13.9±3.2||12.3±4.2|
|17.2 ±2.8||14.5 ±1.9||13.6 ± 2.7t||12.0 ±2. I**|
|Ti/Ttot||0.4 ±0.1||0.4 ±0.04||0.4 ±0.1||0.4 ±0.03|
|0.4 ±0.04||0.4 ±0.04||0.4±0.1||0.4 ±0.02|
|AC||0.4±0.4||0.1 ±0.2||0.1 ±0.2||0.4 ±0.2 + #|
|0.4 ±0.2||0.1 ±0.2||0.1 ±0.2||0.4 ±0.2#|
Figure 1. Pblysomnogram from a subject with Duchenne MD aged 18 years (VC, 0.7 L; MIP, 30 cm H80). The abdominal RIP signal indicates paradoxical inward (downward signal) movement during chest inflation (upward signal) in slow wave sleep.
Figure 2. The relationship between the mean abdominal contribution to breathing (expressed as a percentage) during stage 3/4 NREM sleep and the subsequent maximum fall in oxygen saturation (SaO*) during REM sleep. The linear relationship (y= -0.45x + 22.8) shows a significant (p<0.05) correlation.