Category Archives: Airway Pressure

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure Treatment: Discussion

Results of the present study show that there is a lower amount of SWA across the night, and especially in the first two NREM episodes, before treatment compared to posttreatment values. Comparison between control subjects and untreated apneic patients did not reach the significance, even though control subjects had values that were even higher than those of treated apneic patients. This result can first be explained by the small sample size and large SDs in SWA values for each group. The latter could be related to the large age range of subjects selected for the study, since it is known that SWA varies greatly with age.> The lack of statistically significant differences is also due to the different statistical tests used to assess the differences between conditions in apneic patients (within-group test) on one hand and between control subjects and untreated patients (between-group test) on the other hand. Nonetheless, these results showed that SWA is a more sensitive index of change in slow-wave sleep organization throughout the night than is the proportion of stages 3 and 4 sleep, which was not different from pretreatment to posttreatment recordings. These results show that the general pattern of SWA distribution across the night is normal in CPAP-treated apneic patients. These results also suggest that the decrease in SWA found in untreated apneic patients is at least partly reversible with CPAP treatment. This is consistent with previous findings of an increase in SWS with CPAP treatment. Similarly, a slowing of the EEG during wakefulness had been found in untreated apneic subjects in frontal, central, parietal, occipital, and temporal regions, which was corrected after CPAP. buy asthma inhalers online

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure Treatment: NREM

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure Treatment: NREMThe distributions of SWA for three sleep cycles for control subjects vs untreated SAS patients and for treated vs untreated patients are presented in Figure 2, top and bottom, respectively. There was no interaction effect between group (control subjects and untreated patients) and NREM episode (1, 2, 3). However, an effect of NREM episode (F[2,30]), 13.1; Huynh-Feldt, p = 0.0001) was found, as can be seen in Figure 2, top.
A second ANOVA with two repeated measures (SAS patients before and after CPAP treatment and SWA in successive NREM episodes) showed an interaction between the two factors (F[2,12], 4.97; Huynh-Feldt, p = 0.027). To decompose this interaction effect, an analysis of simple effects was performed and showed a significant pretreatment to posttreatment difference for the first (p = 0.024) and second NREM episodes (p = 0.002); the difference for the third NREM episode was not significant.
As shown in Table 2, the mean sleep latency on the MSLT was significantly correlated with SWA in the first NREM cycle (r = 0.56; p = 0.045) before treatment. The microarousal index was significantly correlated (negatively) with the SWA in the first NREM episode and the total accumulation of SWA for the entire night. There was no significant correlation between the MSLT and either the percentage of REM sleep, the AHI, the Sa02 minimum, or the time spent with Sa02 < 90%.

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure Treatment: Statistical Analyses

Between-group differences in sleep variables and in total SWA were assessed by either Mann-Whitney U tests (control subjects vs SAS patients) or Wilcoxon matched-pair tests (treated vs untreated SAS patients). A two-way analysis of variance (ANOVA) with one independent and one repeated measure was used to compare SWA between SAS patients and control subjects for three successive NREM episodes. A two-way ANOVA with two repeated measures was used to compare SAS patients before and after treatment for three successive NREM episodes. The degrees of freedom were corrected according to Huynh-Feldt adjustments for sphericity violation. Post hoc comparisons were performed for the three episodes. Because 3 untreated patients did not complete their third cycle, the ANOVAs were performed using only 7 patients (before and after treatment and for all cycles) and 10 control subjects. emergency severe sepsis
In order to assess the relationship between the MSLT and different sleep parameters including SWA, Pearson product-moment correlations (unilateral) were used. Wilcoxon matched-pair tests were performed to compare sleep parameters and MSLT results before and after CPAP treatment, and Mann-Whitney U tests to compare control subjects with SAS patients before treatment and with patients after CPAP treatment. Data are presented as mean ± SEM. All statistic analyses have been performed using a software package (Statistica 5.1; StatSoft; Tulsa, OK).

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure Treatment: MSLT

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure Treatment: MSLTThe MSLT consists of five opportunities to nap administered at 10:00 am, 12:00 noon, 2:00 pm, 4:00 pm, and 6:00 pm.18 As for PSG, sleep onset in the modified MSLT was defined as three consecutive epochs (1 min) of stage 1 sleep or one epoch (20 s) of any other sleep stage. Participants were awakened after 10 min of sleep, or the test was stopped after 20 min if they did not fall asleep. Participants were not allowed to drink alcohol or beverages containing caffeine, nor were they allowed to sleep between the five tests.
EEG Spectral Analysis
EEGs were low-pass filtered and digitized on-line at a sampling rate of 128 Hz. Quantitative analysis of the EEG was performed by fast Fourier transform calculated on 4-s miniepochs for the nights preceding the MSLT. SWA was defined as the power (in microvolts squared) in the 0.75- to 4.5-Hz frequency band. The 4-s mini-epochs containing an artifact were rejected and were considered as missing data to preserve sleep continuity. Two visual inspections were performed according to two different criteria. First, “classical artifacts” such as movement, ocular, or muscle artifacts were removed. The second time, “prearousal” slow waves distinguishable from the background activity that occurred from 4 s prior, to 8 s after the end of the respiratory events were also removed. An example of these prearousal slow waves is shown in Figure 1. Interrater reliability between two experienced scorers was tested for the two patients with the highest AHI. To do so, a homemade computer program compares the scorings of the two scorers epoch by epoch and determines the percentage of similarly scored epoch. Between-scorer correlation rates of 98% and 93% were obtained for the first and the second patients, respectively.

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure Treatment: Materials and Methods

Subjects
Ten men (mean age, 42.7 ± 1.87 years; age range, 36 to 57 years; mean body mass index [BMI], 37.54 ± 1.98 kg/m2) with a diagnosis of severe SAS who showed a good clinical and polysomnography (PSG) response to CPAP after 9 ± 0.7 months of treatment were included in the study. Inclusion criteria were as follows: (1) an apnea plus hypopnea index (AHI) of > 30 events/h during the diagnosis night; (2) a good response to CPAP treatment, defined as an AHI of < 10 events/h; and (3) an index of periodic limb movements during sleep of < 10 movements/h of sleep. Exclusion criteria were the presence of any other sleep disorder or pulmonary disease and the use of any medication likely to affect sleep, EEG, or respiratory functions in the month prior to entering the study. Ten normal male subjects (mean age, 43.9 ± 2.2 years; age range, 36 to 55 years; mean BMI, 26.9 ± 1.15 kg/m2) were used as control subjects and were studied with the same procedure. None of the control subjects had a AHI > 5 events/h. Exclusion criteria were the same as those of the SAS group. All subjects signed a consent form prior to starting the experiment, and the study was approved by the ethics committee of the hospital and university. COPD
Nocturnal Sleep Studies
All subjects underwent 1 night of PSG, followed by a modified MSLT the next day; for the SAS patients, the same procedure was repeated after 9 ± 0.7 months of CPAP treatment (Tranquility Plus 7100; Healthdyne; Marietta, GA). Sleep was monitored using two EEG leads (C3-A2, O2-A1), right and left electrooculogram, chin electromyogram, and ECG. To assess apneas and hypopneas, nasal and oral airflow were recorded with thermistors, and respiratory movements with abdominal and thoracic strain gauges. An apnea was defined as a cessation of the respiratory airflow of at least 10-s duration, and an hypopnea as reduction of the airflow > 50% (lasting > 10 s). The AHI represents the number of apneas and hypopneas per hour of sleep. Arterial oxygen saturation (Sao2) was measured continuously with a finger oximeter (Biox III; Ohmeda; Boulder CO); both time < 90% and minimum Sao2 were calculated. Surface electromyogram of anterior tibialis muscles was recorded to quantify periodic leg movements during sleep.

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure Treatment

Slow-Wave Activity in Sleep Apnea Patients Before and After Continuous Positive Airway Pressure TreatmentSleep apnea syndrome (SAS) is a chronic illness characterized by recurrent apneas and hypopneas during sleep, resulting in repetitive arousals and disruption of normal sleep architecture. Several studies have shown a strong deprivation of rapid eye movement (REM) sleep and of stages 3 and 4 nonrapid eye movement (NREM) sleep in SAS patients, even though their sleep efficiency seems to be preserved or minimally changed. Among the various symptoms associated with this condition, the most prevalent is excessive daytime sleepiness (EDS). Critical care
SAS is commonly treated with nasal continuous positive airway pressure (CPAP), which was found to restore normal airflow and sleep architecture and to suppress episodes of nocturnal hypoxemia. CPAP also improves daytime sleepiness as measured by the multiple sleep latency test (MSLT), especially with long-term use, although some degree of daytime somnolence remains.
According to a proposed model of sleep regulation, sleep and vigilance are regulated by two processes: a circadian process (process C) and a homeostatic process (process S). Slow-wave activity (SWA) is considered a marker or an objective measure of process S and has been shown, in normal subjects, to increase with the duration of prior wakefulness and to decline exponentially during the night from the first to the last sleep cycle. Unlike the quantification of slow-wave sleep, which requires an amplitude criterion (> 75 ?ьгжV) and a minimum quantity of these slow waves (20% of the epoch), SWA has no such criteria (thus also takes into account lower-amplitude slow waves and slow waves present in stage 2 sleep) and has a broader frequency definition (0.75 to 4.5 Hz).