Changes in Obstructive Sleep Apnea Characteristics Through the Night

Investigation and treatment of sleep apnoea/hypopnoea syndrome (SAHS) is placing increasing demands on healthcare resources. This workload may be reduced by using split-night studies instead of the standard full-nights of diagnostic polysomnography and continuous positive airway pressure (CPAP) titration. Splitnight studies involve polysomnography in the first half of the night followed, if there is an abnormal frequency of apnoeas and hypopneas, by CPAP titration for the remainder of the night.The authors' database of all patients prescribed a CPAP trial 1991±1997 was used to compare long-term outcomes in all 49 (46 accepting CPAP) patients prescribed split-night studies with those in full-night patients, matched 1:2 using an apnoea/ hypopnoea index (AHI) of 15% and Epworth score of 3 units.Classical symptoms of SAHS were the main reason for the split-night studies (n=27). There were no differences between the groups in long-term CPAP use, median nightly CPAP use (split-night 6.0 h . night -1 , interquartile range (IQR) 3.8±7.4, fullnight; 6.2 h . night -1 , IQR 3.7±7.0, p=0.9), post-treatment Epworth scores and frequency of nursing interventions/clinic visits required. The median time from referral to treatment was less for the split-night patients (13 months, IQR 11±20 months) than for full-night patients (22 months, IQR 12±34 months; p=0.003).Split-night studies, in selected patients, result in equivalent long-term continuous positive airway pressure use to full-night studies with shorter treatment times and less healthcare utilization. Eur Respir J 2000; 15: 670±675. Sleep apnoea/hypopnoea syndrome (SAHS) is a common condition, affecting 2±4% of the middle-aged population [1]. The consequences of SAHS include daytime sleepiness, altered mood and impaired cognitive function [2,3] leading to reduced quality of life [4,5] and an increased risk of accidents at work and on the road [6±8]. Many sleep centres are struggling to cope with the number of patients being referred and the financial restrictions placed on their investigation. One way of reducing the time taken to investigate and treat patients is to use splitnight studies whereby diagnostic polysomnography and continuous positive airway pressure (CPAP) titration are accomplished on the same night rather than the standard two nights consisting of a diagnostic polysomnography night and subsequent CPAP titration night (full-night patients).Despite the potential savings, split-night studies are not widely used in all countries, at least partly because of concerns about the unknown long-term outcome of these studies [9]. The few evaluations that have included clinically relevant outcomes have not used a control group [10], or, when a control group was used, the numbers were small (n=12, in each group) and the outcome evaluation was limited to mean nightly CPAP use at the initial clinic visit [11]. Therefore, a larger scale study of the value of split-night studies was performed. MethodsUsing the authors' database of 1,211 patients booked for CPAP tit...

Section: Discussionmentioning

confidence: 99%

Split-night versus full-night studies for sleep apnoea/hypopnoea syndrome

McArdle¹,

Grove²,

Devereux³

et al. 2000

“…However, we observed that the rate of increase in Pdi during apnoeas was unchanged, and the peak Pdi at end-apnoea, in fact, increased significantly, in association with an increase in apnoea duration over the course of the night. The issue of lengthening of apnoea is discussed in detail elsewhere (12)(13)(14). However the finding that generation of inspiratory effort during apnoeas is preserved over the course of the night provides a strong argument against the development of overt inspiratory muscle fatigue.…”

Section: Discussionmentioning

confidence: 99%

“…The data were obtained from seven males with documented OSA, who were recruited from the Royal Victoria Hospital Sleep Disorders Clinic during the course of studies on the mechanisms of lengthening of apnoea during the course of the night [12][13][14]. Patients were eligible if they had not yet received treatment for OSA, had no other active medical problems, and had no major pulmonary dysfunction on routine pulmonary function testing (forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) >70% of predicted).…”

Section: Subjectsmentioning

confidence: 99%

Lack of evidence for diaphragmatic fatigue over the course of the night in obstructive sleep apnoea

Montserrat¹,

Kosmas²,

Cosio³

et al. 1997

“…Accordingly, a study that investigated: 1) the plasma levels of oxidized LDL (and its susceptibility to oxidation) in patients with untreated OSAS, as compared to healthy subjects was designed. Because the duration of apnoeas and the severity of the H/R episodes increases throughout the night [11,12], these same variables were analysed before, during and after sleep; and 2) the effects of long-term treatment (>1 yr) with CPAP upon these indices of lipid peroxidation were also examined.…”

mentioning

confidence: 99%

Abnormal lipid peroxidation in patients with sleep apnoea

Barceló¹,

Miralles²,

Barbé³

et al. 2000

207

111

The prevalence of cardiovascular diseases is increased in patients with the obstructive sleep apnoea syndrome (OSAS). The fall and rise of arterial oxygenation that follows each apnoea may increase lipid peroxidation and contributes to explaining this association. In the present study, the authors determined lipid peroxidation in patients with OSAS and the effect of treatment with continuous positive airway pressure (CPAP).Fourteen male patients with severe OSAS (59 5 apnoea . h -1 ) ( SEM) and 13 healthy nonsmoking, male volunteers of similar age were studied. Patients were studied at diagnosis and after treatment with CPAP for more than 1 yr (>4 h . night -1 ). A venous blood sample was obtained early in the morning after fasting all night. In patients with OSAS, a sample before and during sleep was also obtained. Low density lipoprotein (LDL) particles were isolated by sequential ultracentrifugation. Their level of oxidation was determined by the thiobarbituric acid assay (TBARs), and their susceptibility to oxidation by the lag phase measurement.Patients with OSAS showed higher TBARs (28.1 2.8 versus 20.0 1.8 nmol . malondialdehyde . mgLDL protein -1 , p=0.02) and shorter lag phase values (83.8 3.4 versus 99.7 3.4 min, p=0.005) than controls. These differences were not due to the smoking status of the patient. Likewise, these values did not change significantly throughout the night yet, the lag phase value was significantly improved by treatment with CPAP (124.9 8.5 min; p<0.001).These results indicate that obstructive sleep apnoea syndrome is associated with abnormal lipid peroxidation and that this is improved by chronic use of Continuous positive airway pressure. These results can contribute towards explaining the high prevalence of cardiovascular diseases seen in Obstructive sleep apnoea syndrome.