An auto-continuous positive airway pressure device controlled exclusively by the forced oscillation technique.

The forced oscillation technique (FOT) has been demonstrated to be a very sensitive tool for the assessment of upper airway obstruction during nasal continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea (OSA). The present study was designed to evaluate the therapeutic efficacy of a novel auto-CPAP device based exclusively on the FOT. Following manual CPAP titration, 18 patients with OSA (mean apnoea/hypopnoea index (AHI) 48.0+/-28.1) were allocated to conventional CPAP and auto-CPAP treatment under polysomnographic control in randomized order. The patients were asked to assess their subjective daytime sleepiness using the Epworth Sleepiness Scale (ESS). The mean AHI during auto-CPAP treatment was 3.4+/-3.4 and was comparable with that obtained during conventional CPAP treatment (4.2+/-3.6). The analysis of sleep architecture, the arousal index (6.6+/-2.1 versus 7.3+/-4.4) or the ESS (5.6+/-1.8 versus 7.3+/-4.4) did not reveal any significant differences. However, the mean CPAP pressure during auto-CPAP treatment (0.84+/-0.26 kPa) and in particular the pressure applied in the lateral body position (0.74+/-0.35 kPa), was significantly lower than that employed in conventional CPAP treatment (0.93+/-0.16 kPa, both comparisons: p<0.05). The auto-continuous positive airway pressure device proved equally as effective as conventional continuous positive airway pressure. However, the mean treatment pressure was significantly reduced, especially when patients were sleeping in the lateral position.     

Sensitivity of a simplified forced oscillation technique for detection of upper airway obstruction

The sensitivity of a simplified variant of forced oscillation technique (FOT) was studied for assessment of dynamic upper airway obstruction during nasal continuous positive airway pressure (nCPAP) therapy for obstructive sleep apnoea (OSA). The airway impedance P[FOT] was measured by FOT and the oesophageal pressure (P(oes)) was recorded during stable stage II sleep in 11 patients with OSA. The CPAP level was initially set high enough to completely abolish upper airway obstruction. To induce gradually increasing upper airway re-obstruction, the CPAP pressure was then lowered stepwise. Thirty six such manoeuvres were analysed, blind, to define the first inspiration at which upper airway re-obstruction was detectable by analysis of P[FOT](t(FOT)) and by P(oes)(t(oes)), respectively. On seven occasions t(FOT) and t(oes) occurred together, in the remaining 29 cases t(FOT) preceded t(oes) with a mean latency of 6.0+/-7.7 (0-32) breath cycles. In no case did t(oes) preceed t(FOT). FOT is a highly sensitive tool for the assessment of incipient upper airway obstruction during nCPAP therapy.     

Genioglossus activity during sleep in normal control subjects and children with obstructive sleep apnea

Children with obstructive sleep apnea syndrome (OSAS) have more collapsible airways compared with normal subjects, yet sustain stable breathing during wakefulness and part of sleep. This indicates successful neuromuscular compensation. Using a custom intraoral surface electrode to record pharyngeal dilator muscle activity (the genioglossus [EMGgg] normalized to the wakeful baseline), we performed overnight polysomnograms in three groups of children: (1) patients with OSAS without continuous positive airway pressure (CPAP) (n = 13); (2) patients with OSAS with CPAP (n = 5); and (3) control subjects without CPAP (n = 13). Our objective was to evaluate the EMGgg as a function of sleep state and during disordered breathing, compared with stable sleep and wakefulness. In control subjects, the EMGgg decreased from wakefulness to Stage 2 (mean +/- SD, 65 +/- 6%), and further during REM (51 +/- 9%) (p < 0.05). In patients with OSAS, the EMGgg for apneic breaths during REM (37 +/- 9%) was lower than during stable breathing (83 +/- 17%) (p < 0.05) and wakefulness (p < 0.05). CPAP lowered the EMGgg in patients with OSAS during all sleep states. These data indicate that (1) EMGgg compensatory mechanisms remain active during sleep in patients with severe OSAS; (2) EMGgg reductions are temporally associated with sleep apnea events; and (3) REM sleep is associated with the lowest and most variable EMGgg.     

Evaluation of a simplified oscillation technique for assessing airway obstruction in sleep apnoea.

The forced oscillation technique (FOT) is a noninvasive method that is useful for assessing airway obstruction and for titrating continuous positive airway pressure (CPAP) in patients with sleep apnoea. The aim was to evaluate the routine applicability of a simplified FOT set-up based on recording pressure and flow at the level of the CPAP device, i.e. obviating the need for connecting the transducers to the nasal mask. A correction to account for the tubing and the exhaust port was applied. This simplified FOT was evaluated on nine patients with moderate or severe sleep apnoea during routine CPAP titration. Patient impedance measured by the simplified FOT ([Z]) was compared with actual patient impedance ([Zrs]) measured simultaneously with a reference FOT based on recording pressure and flow at the nasal mask. An excellent agreement was found between [Z] and [Zrs] over the wide range of airway obstruction explored (4.8-72.1 cmH2O x s x L(-1)): [Z] = [Zrs] x 0.86 + 1.3 cmH2O x s x L(-1) (r = 0.99). Moreover, the simplified and the conventional FOT settings detected the same respiratory events during sleep. These results demonstrate that this simplified FOT is applicable for measuring airway obstruction during routine sleep studies in patients with sleep apnoea.     

Automatic CPAP titration with different self-setting devices in patients with obstructive sleep apnoea.

Autotitrating continuous positive airway pressure (CPAP) devices automatically adjust the pressure according to upper airway obstructions. The aim of this study was to compare the treatment effects of different automatic CPAP devices (AutoSet, Horizon and Virtuoso) with conventional CPAP in patients with obstructive sleep apnoea independently of financial manufacturer support. Twelve male patients with obstructive sleep apnoea were submitted to a crossover study protocol with overnight polysomnography for 6 consecutive nights. After diagnostic polysomnography, the CPAP pressure was manually titrated. Over the next 4 nights, the patients were treated with any one of the three automatic CPAP devices or fixed CPAP in random order. The apnoea/hypopnoea index on the diagnostic night was 67.3+/-21.7 events h(-1), and was significantly reduced to 0.7+/-1.2, 3.0+/-2.9, 2.3+/-2.5 and 12.0+/-13.6 events x h(-1) with the fixed CPAP, AutoSet, Horizon and Virtuoso devices respectively. An apnoea/ hypopnoea index of <5 events h(-1), an indicator of optimal treatment, was achieved in all patients with fixed CPAP and in 10 patients using the Autoset and Horizon devices, but in only six of the 12 using the Virtuoso. The mean pressure was significantly lower with the AutoSet and Virtuoso devices, but not with the Horizon as compared to fixed CPAP. The maximum pressure was significantly higher with the Horizon. It is concluded that automatic continuous positive airway pressure devices produce a significant reduction in apnoea/hypopnoea index; however, there is considerable difference in the efficacy of the various devices.     

Importance of sleep stage- and body position-dependence of sleep apnoea in determining benefits to auto-CPAP therapy.

The influence of sleep stage- and body position-dependence of sleep apnoea on treatment efficacy and compliance between conventional continuous positive airway pressure (CPAP) and auto CPAP therapy was evaluated. Thirty-three newly treated sleep apnoea hypopnoea syndrome (SAHS) patients were randomly allocated to conventional or auto-CPAP therapy. Six patients of each treatment group were classified as having sleep stage- and body position-dependent obstructive breathing abnormalities according to the results of the baseline sleep study. After 3 weeks of treatment, the Epworth sleepiness score tended to be higher (p = 0.08) and the ability to stay awake lower (p = 0.02) in patients with dependent breathing abnormalities treated with fixed CPAP, than in the other patients. The effective pressure/time index was significantly lower in sleep stage- and body position-dependent patients treated with fixed CPAP, than in the other patients (p = 0.02). The number of hours the machine was turned on and a positive pressure applied, tended to be smaller in dependent patients treated with fixed CPAP than in independent patients of this treatment group and in patients treated with auto-CPAP. A night-to-night variability index (VI) of positive pressure changes was obtained in the auto-CPAP group. This index significantly decreased with time in the dependent patients while it remained unchanged in the independent group. It is concluded that auto-continuous positive airway pressure may have specific indications in a subset of obstructive sleep apnoea patients with sleep stage- and body position dependent nocturnal breathing abnormalities.     

Health utilities in evaluating intervention in the sleep apnoea/hypopnoea syndrome.

Formulating a rational health policy necessitates the ability to compare between different healthcare interventions and disease scenarios. Continuous positive airway pressure (CPAP) therapy with a conservative lifestyle strategy in sleep apnoea/hypopnoea syndrome (SAHS) was evaluated using health utility and quality-adjusted life years (QALYs) as outcome measures. A total 71 SAHS (apnoea/hypopnoea index > or = 15 h(-1)) patients completed a randomised, parallel group study over 3 months using utilities derived by the standard gamble approach (Usg) and European quality of life questionnaire (Euroqol) (Ueq). The severely impaired health status at baseline improved by 23% (Usg 0.32 to 0.55) adding 8 QALYs in the CPAP group, compared to a 4% improvement with 4.7 QALYs added in the lifestyle group (Usg 0.31 to 0.35). The Ueq showed a marginal change with CPAP (0.73 to 0.77) but did not demonstrate any improvement with lifestyle intervention. The health status impairment in sleep apnoea/hypopnoea syndrome patients is markedly improved by continuous positive airway pressure compared to a modest improvement with conservative lifestyle strategies using the standard gamble utility, which may be incorporated in effectiveness and economic analyses. The European quality of life questionnaire did not reflect a similar degree of impact and is probably not useful in this population.     

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

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. Split-night 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 x night-1, interquartile range (IQR) 3.8-7.4, full-night; 6.2 h x 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.     

The sleep apnoea/hypopnoea syndrome depresses waking vagal tone independent of sympathetic activation.

The modest daytime hypertension and sympathetic upregulation associated with the sleep apnoea/hypopnoea syndrome (SAHS), does not explain the relatively large increased risk of cardiac morbidity and mortality in the SAHS patients population. Therefore, efferent vagal and sympathetic activity was evaluated during wakefulness in SAHS subjects and matched healthy controls, in order to determine if vagal downregulation may play a role in the aetiology of cardiac disease in the SAHS. The awake autonomic nervous system function of 15 male subjects, with mild-to-moderate SAHS was compared to that of 14 healthy controls matched for age, body mass index, gender and blood pressure. All subjects were free from comorbidity. Vagal activity was estimated from measurements of heart rate variability high frequency power (HF) and sympathetic activity was measured from urine catecholamine excretion. The %HF power was significantly (p < 0.03) reduced in SAHS patients (10+/-1.6 (mean+/-SEM)) as compared to controls (17 +/- 3). In addition, HF power correlated with the apnoea/hypopnoea index in the SAHS subjects (R = -0.592, p = 0.02). There was no statistically significant difference in the daytime excretion of nonadrenaline between control (242 +/- 30 nmol x collection(-1)) and SAHS (316 +/- 46 nmol x collection(-1)) subjects (p = 0.38). In these sleep apnoea/hypopnoea syndrome patients there was limited evidence of increased waking levels of urine catecholamines. The principal component altering waking autonomic nervous system function, in the sleep apnoea/hypopnoea syndrome subjects, was a reduced daytime efferent vagal tone.     

Influence of airway pressure on genioglossus activity during sleep in normal children

RATIONALE: Most children with obstructive sleep apnea are able to sustain stable breathing during portions of sleep, despite an anatomic predisposition toward airway collapse. This suggests that additional determinants of airway patency are active, such as neuromuscular compensation. OBJECTIVES/METHODS: Using a custom intraoral surface electrode to record pharyngeal dilator muscle activity (the genioglossus [EMGgg]), we evaluated the muscle, ventilatory, and arousal responses to negative-pressure challenges during sleep in 19 healthy control children. MEASUREMENTS AND MAIN RESULTS: In response to these challenges, we observed (1) marked variability in individual EMGgg responsiveness (peak EMGgg [mean+/-SD], 214+/-101% baseline), which was consistent within subjects; (2) a relationship between EMGgg activity and inspiratory flow and airway collapsibility; (3) reflex increases in flow (peak flow increase from challenge breaths 1-5 [mean+/-SD], 49+/-41% baseline) and respiratory rate often sufficient to sustain minute ventilation near baseline levels, without arousal; and (4) arousal threshold to be highest in stage 4, intermediate in stage 2, and lowest in REM sleep. CONCLUSIONS: Healthy children have wide variation in upper airway neuromuscular compensatory responses and arousal thresholds that could represent intermediate phenotypes affecting the expression of sleep apnea. Children with robust upper airway neuromuscular responsiveness, or a very high arousal threshold, may be able to sustain minute ventilation when challenged with negative airway pressure.     

Long-term treatment with continuous positive airway pressure improves quality of life in obstructive sleep apnoea syndrome.

Continuous positive airway pressure (CPAP) is an established treatment of obstructive sleep apnoea syndrome (OSAS). While it is known that CPAP reverses the pathological breathing pattern and improves daytime sleepiness, there are no sufficient data on the long-term influence of CPAP on quality of life in patients with OSAS. Thirty-nine patients with polysomnographically verified OSAS (apnoea/hypopnoea index (AHI): (mean+/-SD) 46.8+/-21.8 events x h(-1)) were prospectively studied. All patients answered three quality of life measures (Complaint List, Nottingham Health Profile Part 1 (NHP), and Verbal Analogue-Scale "quality of life") prior to the initiation of CPAP therapy. After a mean of 9 months they were re-evaluated by polysomnography, and completed the questionnaires once again. As expected, CPAP was effective in treating the sleep-related breathing disorder. AHI decreased significantly from (mean+/-SD) 46.8+/-21.8 events x h(-1) to 3.3+/-6.3 events x h(-1), and minimum oxygen saturation increased from 77.1+/-9.3% to 89.9+/-3.4%, while body mass index did not change significantly (31.3+/-5.4 versus 30.8+/-4.8 kg x m(-2)). During long-term treatment with CPAP the Complaint List revealed a significant improvement of the extent of subjective impairment due to physical and general complaints (26.4+/-9.9 versus 20.4+/-11.1), and NHP a significant improvement of emotional reactions (19.8+/-21.7 versus 11.1+/-14.0) and energy (50.8+/-36.6 versus 32.1+/-36.7), but not of pain, physical mobility, sleep, social isolation, and quality of life as assessed by the It is concluded that long-term continuous positive airway pressure therapy is effective in improving not only pathological breathing patterns but also parameters that estimate quality of life in patients with obstructive sleep apnoea syndrome.     

Mortality in severe sleep apnoea/hypopnoea syndrome patients: impact of treatment.

The aim of this study was to determine mortality in patients with sleep apnoea/hypopnoea syndrome (SAHS) according to the treatments employed and comorbidity. An historical cohort of patients with SAHS diagnosed at a university hospital between 1982 and 1992 and followed until 1996 was studied. From a total of 475 SAHS patients, 444 (94%), with a mean+/-SD apnoea/hypopnoea index at diagnosis of 55+/-27, were located and included in the study. SAHS treatments employed were: surgery (88), weight loss (134), continuous positive airway pressure (124) and 98 patients were not treated. By the end of follow-up, 49 patients had died. According to Cox regression analysis, mortality in treated patients was lower than in those not treated, but higher in those with a history of severe chronic obstructive pulmonary disease. Mortality in nontreated patients compared with that of the general population, adjusted for age and sex, showed excessive mortality, which decreased in treated patients. Stratification by age showed a greater mortality rate ratio in patients <50 yrs. These findings were maintained when mortality from cardiovascular causes was compared. In conclusion, a rise in mortality was found in nontreated sleep apnoea/hypopnoea syndrome patients compared with the general population, whereas mortality in those treated for sleep apnoea/hypopnoea syndrome did not differ significantly from that of the general population.     

Assisted ventilation for heart failure patients with Cheyne-Stokes respiration.

Patients with chronic congestive cardiac failure (CCF) frequently suffer from central sleep apnoea syndrome (CSAS). Continuous positive airway pressure (CPAP) has been suggested as a treatment. The authors hypothesised that bilevel ventilation might be easier to initiate and superior to CPAP at correcting the sleep-related abnormality of breathing in patients with CCF. After excluding those with a history suggestive of obstructive sleep apnoea, 35 patients with CCF (left ventricular ejection fraction <35%) were screened with overnight oximetry and the diagnosis of CSAS was established with polysomnography in 18. Two 14-day cycles of CPAP (0.85 kPa (8.5 mbar)) or bilevel ventilation (0.85/0.3 kPa (8.5/3 mbar)) in random order, were compared in a crossover study. Sixteen patients (13 males), mean age 62.0+/-7.4 yrs completed the study. The pretreatment apnoea/hypopnoea index of 26.7+/-10.7 was significantly reduced by CPAP and bilevel ventilation to 7.7+/-5.6 and 6.5+/-6.6, respectively. The arousal index fell from 31.1+/-10.0 per hour of sleep to 15.7+/-5.4 and 16.4+/-6.9, respectively. Significant and equal improvements with CPAP and bilevel ventilation were found for sleep quality, daytime fatigue, circulation time and New York Heart Association class. The authors conclude that continuous positive airway pressure and bilevel ventilation equally and effectively improve Cheyne-Stokes respiration in patients with congestive cardiac failure.     

A simplified method for monitoring respiratory impedance during continuous positive airway pressure.

The forced oscillation technique is useful in detecting changes in upper airway obstruction in patients with sleep apnoea undergoing continuous positive airway pressure (CPAP) ventilation. The aim of this study was to implement and evaluate a method for estimating respiratory impedance (Zrs) from the pressure and flow recorded at the inlet of the CPAP tubing. The method is based on correcting impedance measured at the inlet of the CPAP tubing (Zi) for the effect of the tubing and the exhalation port. The method was evaluated in mechanical analogues and in a healthy subject. Sinusoidal oscillation of 5, 10 and 20 Hz were superimposed on CPAP (5-15 cmH2O). At 5 Hz, the changes in airflow obstruction were substantially underestimated by Zi. Furthermore, Zi exhibited a negative dependence on Zrs at 20 Hz. The assessment of Zrs was greatly improved after correcting Zi for the effects of the CPAP tubing and the exhalation port. Zrs was well estimated at low frequencies, reaching very high values during total occlusion (>60 cmH2O x s x L(-1) at 5-10 Hz). These results indicate that changes in airflow obstruction can be detected using the forced oscillation technique from pressure and flow recorded on the continuous positive airway pressure device. This facilitates the clinical application of the forced oscillation technique for monitoring upper airway patency during sleep.     

Effect of obesity and erect/supine posture on lateral cephalometry: relationship to sleep-disordered breathing.

Craniofacial and upper airway anatomy, obesity and posture may all play a role in compromising upper airway patency in patients with the sleep apnoea/hypopnoea syndrome. The aim of this study was to investigate the relationship between obesity, facial structure and severity of sleep-disordered breathing using lateral cephalometric measurements and to assess the effect of body posture on cephalometric measurements of upper airway calibre variables in obese and non-obese subjects. Lateral cephalometry was carried out in erect and supine postures in 73 awake male subjects randomly selected from patients referred for polysomnography who had a wide range of apnoea/hypopnoea frequencies (1-131 events x h sleep(-1)). Subjects were divided into non-obese (body mass index (BMI) < 30 kg x m(-2); n=42) and obese (BMI > or = 30 kg x m(-2); n=31) groups. Significant but weak correlations were found between apnoea/hypopnoea index (AHI) and measurements reflecting upper airway dimensions: uvular protrusion-posterior pharyngeal wall (r=-0.26, p<0.05) and hyoid-posterior pharyngeal wall (r=0.26, p<0.05). Multiple regression using both upper airway dimensions improved the correlation to AHI (r=0.34, p=0.01). Obese subjects had greater hyoid-posterior pharyngeal wall distances than non-obese subjects, both erect (42+/-5 versus 39+/-4 mm, respectively (mean+/-SD) p<0.01) and supine (43+/-5 versus 40+/-4 mm, p<0.05). Skeletal craniofacial structure was similar in obese and non-obese subjects. In conclusion, measurements reflecting upper airway size were correlated with the severity of sleep-disordered breathing. Differences in upper airway size measurements between obese and non-obese subjects were independent of bony craniofacial structure.     

Baroreflex control of heart rate during sleep in severe obstructive sleep apnoea: effects of acute CPAP.

Baroreflex control of heart rate during sleep (baroreflex sensitivity; BRS) has been shown to be depressed in obstructive sleep apnoea (OSA), and improved after treatment with continuous positive airway pressure (CPAP). Whether CPAP also acutely affects BRS during sleep in uncomplicated severe OSA is still debatable. Blood pressure was monitored during nocturnal polysomnography in 18 patients at baseline and during first-time CPAP application. Spontaneous BRS was analysed by the sequence method, and estimated as the mean sequence slope. CPAP did not acutely affect mean blood pressure or heart rate but decreased cardiovascular variability during sleep. Mean BRS increased slightly during CPAP application (from 6.5+/-2.4 to 7.5+/-2.9 ms x mmHg(-1)), mostly in response to decreasing blood pressure. The change in BRS did not correlate with changes in arterial oxygen saturation or apnoea/hypopnoea index. The small change in baroreflex control of heart rate during sleep at first application of continuous positive airway pressure in severe obstructive sleep apnoea was unrelated to the acute resolution of nocturnal hypoxaemia, and might reflect autonomic adjustments to positive intrathoracic pressure, and/or improved sleep architecture. The small increase in baroreflex control of heart rate during sleep may be of clinical relevance as it was accompanied by reduced cardiovascular variability, which is acknowledged as an independent cardiovascular risk factor.     

Upper airway collapsibility, dilator muscle activation and resistance in sleep apnoea.

The calibre of the upper airway is thought to be dependant upon its passive anatomy/collapsibility and the activation of pharyngeal dilator muscles. During awake periods, the more collapsible upper airway in obstructive sleep apnoea (OSA) increases the dilator muscle activity through a negative-pressure reflex. A direct correlation between the critical closing pressure (P(crit)), as a measure of anatomy/collapsability and electromyogram (EMG) activity of genioglossus EMG (GG-EMG) and tensor palatini EMG (TP-EMG), was hypothesised. The relationship between these indices and pharyngeal resistance (R(phar)) was also examined. The study involved eight males with a mean age of 48 (interquartile range 46-52) yrs with OSA, and an apnoea/hypopnoea index of 75 (65-101).hr(-1) on two nights breathing normally and on nasal continuous positive airway pressure (nCPAP). The P(crit )was measured during nonrapid eye movement sleep on nCPAP using brief, incremental reductions in mask pressure. GG-EMG and TP-EMG were measured breath-by-breath, awake, during sleep onset and on nCPAP. R(phar) was measured using airway pressures and flow. Wakeful GG-EMG, early sleep TP-EMG and the sleep decrement in TP-EMG were directly related to P(crit). Muscle activation was negatively correlated with R(phar) for TP-EMG awake and GG-EMG early in sleep. In conclusion these results confirm that dilator muscle activation is directly related to airway narrowing and reduces resistance across patients with obstructive sleep apnoea.     

Positive effect of CPAP treatment on the control of difficult-to-treat hypertension.

The aim of the present study was to analyse the role of continuous positive airway pressure (CPAP) treatment in patients with difficult-to-control hypertension (DC-HT) and sleep apnoea. An Autoset (ResMed, Sydney, Australia) study was performed in 60 patients diagnosed with DC-HT based on two 24-h ambulatory blood pressure monitorisation (ABPM) studies. CPAP was offered to patients with an apnoea/hypopnoea index (AHI) > or =15 events.h(-1). After 3 months of treatment, repeat ABPM was performed to evaluate the effect of CPAP upon the blood pressure values. A total of 39 (65%) patients received CPAP treatment, but only 33 completed the study. The mean+/-sd systolic and diastolic blood pressures (SBP and DBP, respectively) were 154.8+/-14 and 90+/-8.8 mmHg. Patients had a mean+/-sd AHI of 37.7+/-18.2 events.h(-1). Only three patients presented a dipper nocturnal pressure pattern. CPAP treatment significantly reduced SBP (-5.2 mmHg), and particularly the nocturnal values (-6.1 mmHg), but not DBP. Considering only those patients who tolerated CPAP, the decrease in SBP was greater (-7.3 mmHg). Furthermore, CPAP treatment significantly increased the percentage of patients who recovered the dipper pattern (three (9.1%) out of 33 versus 12 (36.4%) out of 33). Continuous positive airway pressure treatment significantly reduces systolic blood pressure, particularly at night, and normalises the nocturnal pressure pattern in patients with difficult-to-control hypertension and sleep apnoea.     

Proportional positive airway pressure: a new concept to treat obstructive sleep apnoea.

Proportional positive airway pressure (PPAP) was designed to optimize airway pressure for the therapy of obstructive sleep apnoea (OSA). In a randomized crossover prospective study, the clinical feasibility of PPAP and its immediate effects on the breathing disorder and sleep in comparison with continuous positive airway pressure (CPAP) was evaluated. Twelve patients requiring CPAP therapy underwent CPAP and PPAP titration in a random order. Obstructive and mixed respiratory events could be completely abolished with both forms of treatment. This efficacy could be achieved at a significantly lower mean mask pressure during PPAP titration (8.45+/-2.42 cmH2O) compared to CPAP (9.96+/-2.7 cmH2O) (p=0.002). The mean minimal arterial oxygen saturation (Sa,O2) (82.8+/-6.5%) on the diagnostic night increased significantly (p<0.001) to an average Sa,O2 of 93.35+/-1.71% and 93.19+/-2.9% during CPAP and PPAP titration. Total sleep time, slow wave sleep and rapid eye movement (REM) sleep increased significantly by the same amount during both CPAP and PPAP titration (p<0.001), while sleep stage nonrapid eye movement (NREM) 1 and 2 decreased. Six patients preferred the PPAP titration night, four patients did not have a preference, and two patients preferred CPAP. The present data show that proportional positive airway pressure is as effective as continuous positive airway pressure in eliminating obstructive events and has the same immediate effect on sleep. The lower average mask pressure during proportional positive airway pressure implies potential advantages compared to continuous positive airway pressure. Proportional positive airway pressure presents a new effective therapeutic approach to obstructive sleep apnoea.     

Comparison of three auto-adjusting positive pressure devices in patients with sleep apnoea.

Auto-adjustable continuous positive airway pressure (APAP) devices are an emerging treatment alternative to fixed-pressure continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea syndrome. They have been engineered to automatically adjust the pressure to the optimal level on a continuous basis. However, not all APAP technologies use the same algorithm. Three different APAP devices (Autoset Spirit, Breas PV 10i and RemStar Auto) were compared in a randomised crossover trial in patients already established on fixed-pressure CPAP therapy. The outcome measures were compliance, quality of life and side-effects. Twenty-seven middle-aged patients (25 male) previously diagnosed with severe obstructive sleep apnoea syndrome (median (interquartile range) apnoea/hypopnoea index 48 (29-76)), established on CPAP therapy for >3 yrs, were randomised to each APAP device for 4 weeks. Mean pressure and patient compliance were significantly lower on the Breas PV 10i than on the other APAP devices. The devices were similar in terms of quality of life, daytime sleepiness and upper airway side-effects, but patients evaluated them significantly differently in terms of device features, sleep quality and pressure comfort, with the Breas PV 10i being the least popular. Auto-adjustable positive airway pressure devices differ in pressure delivery and patient compliance in obstructive sleep apnoea syndrome patients.