Bench model to simulate upper airway obstruction for analyzing automatic continuous positive airway pressure devices

BACKGROUND: Automatic positive airway pressure (APAP) devices are increasingly being used in patients with obstructive sleep apnea. Some APAP devices present an unstable behavior when subjected to some events or artifacts. The aims were to develop a bench model capable of reproducing real flow, snoring, and obstructive patterns and to compare the response of APAP devices based on flow and snoring with other devices using, in addition, the forced oscillation technique (FOT). METHODS: The bench model subjected APAP devices to apneas with and without obstruction, obstructive hypopneas with and without snoring, periods of flow limitation, and artifacts such as leaks and mouth expiration. RESULTS: Almost all the devices increased the pressure when subjected to apneas with obstruction, but at different rates. The time required by each device to reach 10 cm H(2)O ranged from 2.5 to 13 min. In the presence of apneas without obstruction, all the devices based on flow and snoring increased the pressure at the same rate as during apneas with obstruction. However, the devices using FOT did not modify the pressure. Four devices did not modify the pressure in the presence of obstructive hypopneas, and all but one device increased the pressure in the presence of snoring. Mask leaks had little effect on the response of the devices, but four devices increased the pressure during mouth expiration artifacts. CONCLUSIONS: When, in addition to the flow and snoring signals, the measurement of the upper airway resistance is included, the accuracy of the event detection algorithms is improved.     

Assessment of inspiratory flow limitation in children with sleep-disordered breathing by a nasal cannula pressure transducer system

A nasal cannula pressure transducer system identifies inspiratory flow limitation and increased upper airway resistance in adults with sleep-disordered breathing (SDB). The purpose of this study was to evaluate whether nasal cannula pressure (NCP) detects apneas and hypopneas as well as additional flow-limited events associated with increased airway resistance in children. We studied NCP in 47 patients (ages 2-14 years) referred for SDB to a university-based sleep disorders program during nocturnal polysomnography (NPSG). During NPSG, airflow was assessed simultaneously by thermistor and NCP. There was a high correlation between apneas assessed by thermistor (T) and NCP (r = 0.90, P < 0.0001), and for hypopneas using these two methods (r = 0.94, P = 0.0001). Respiratory driving pressure was indirectly measured with an esophageal pressure catheter. Flow-limited (flattened) NCP waves were associated with significantly higher driving pressure, indicating elevated upper airway resistance, compared to nonflow-limited (rounded) waves during nonrapid eye movement (NREM) (P = 0.05) and rapid eye movement (REM) (P = 0.01) sleep. Patients were classified as either having obstructive sleep apnea syndrome (OSAS) or primary snoring, based on standard NPSG criteria. NCP identified additional respiratory events with a flattened contour (FC) not detected by thermistor. NCP is a noninvasive device that identifies obstructive apneas and hypopneas as well as additional respiratory events associated with flow limitation in children.     

Relevance of linearizing nasal prongs for assessing hypopneas and flow limitation during sleep

Respiratory disturbances in patients with the sleep apnea-hypopnea syndrome (SAHS) may be detected by means of nasal prongs (NP) pressure (PNP). Nevertheless, PNP is nonlinearly related to flow (V). Our aim was to demonstrate the relevance of linearizing P NP for assessing hypopneas and flow limitation in SAHS. V was measured with a pneumotachograph during the hypopneas and flow limitation events in a continuous positive airway pressure (CPAP) titration in six patients with severe SAHS. These flow patterns were reproduced by a flow generator through an analog of the nares and recorded by NP. PNP was linearized [V NP = (PNP)1/2] by a specially designed analog circuit. For each event we used V, P NP, and V NP to compute the hypopnea flow amplitude (HFA) and a flow limitation index (FLI). Owing to NP nonlinearity, PNP considerably misestimated HFA and FLI. By contrast, V NP provided HFA and FLI values that were very close to those obtained from V: HFA (V NP) = 1.098. HFA(V) - 0.063 (r2 = 0.98) and FLI(V NP) = 1.044. FLI(V) + 0.004 (r2 = 0.99). Square-root linearization of NP greatly increases the accuracy of quantifying hypopneas and flow limitation. This procedure, which could be readily carried out in routine practice by means of the analog circuit we developed, is of interest in optimizing the assessment of respiratory sleep disturbances in SAHS.     

A home monitoring system for nasal CPAP

A compact portable sensing system (PSS) was developed for home monitoring of patients with obstructive sleep apnea treated with nasal continuous positive-airway pressure (CPAP). The system consisted of a solid-state pressure sensor connected with plastic tubing to the side port of the nasal CPAP mask, a power supply, and a strip chart recorder. The device was validated against standard polysomnography in ten patients with obstructive sleep apnea undergoing overnight nasal CPAP trials. A total of 397 apneas and hypopneas were observed in the ten patients. The PSS device detected 386 events (sensitivity, 97.2 percent). In addition, there were 29 false positive events noted by the device (positive predictive value, 93 percent). The device was then tested at home in 23 patients on nasal CPAP. Eight of these patients had persistent apneas requiring adjustment of their CPAP pressure. The PSS device allowed for accurate reevaluation of nasal CPAP settings in the patient's home without necessitating expensive, time-consuming in-hospital laboratory polysomnographic studies.     

Upper airway collapsibility in snorers and in patients with obstructive hypopnea and apnea

During sleep, mild reduction in inspiratory airflow is associated with snoring, whereas obstructive hypopneas and apneas are associated with more marked reductions in airflow. We determined whether the degree of inspiratory airflow reduction was associated with differences in the collapsibility of the upper airway during sleep. Upper airway collapsibility was defined by the critical pressure (Pcrit) derived from the relationship between maximal inspiratory airflow and nasal pressure. In 10 asymptomatic snorers, six patients with obstructive hypopneas, and 10 patients with obstructive apneas, during nonrapid eye movement sleep, Pcrit ranged from -6.5 +/- 2.7 cm H2O to -1.6 +/- 1.4 and 2.5 +/- 1.5 cm H2O, respectively (mean +/- SD, p less than 0.001). Moreover, higher levels of Pcrit were associated with lower levels of maximal inspiratory airflow during tidal breathing during sleep (p less than 0.005). We conclude that differences in upper airway collapsibility distinguish among groups of normal subjects who snore and patients with periodic hypopneas and apneas. Moreover, the findings suggest that small differences in collapsibility (Pcrit) along a continuum are associated with reduced airflow and altered changes in pattern of breathing.     

Efficacy of flow- vs impedance-guided autoadjustable continuous positive airway pressure: a randomized cross-over trial

STUDY OBJECTIVES: Autoadjustable continuous positive airway pressure (CPAP) devices are increasingly used in the treatment of obstructive sleep apnea (OSA). Since different measurements of upper airway obstruction are applied, it is uncertain whether these devices are equally effective in controlling sleep-disordered breathing. Hypothesizing that differences in therapeutic efficacy were to come out, we compared the performance of the AutoSet device (ResMed; Sydney, Australia), which features autoadjustable positive airway pressure (APAP) guided by detection of flow limitation (APAPfl), with the SOMNOsmart device (Weinmann; Hamburg, Germany), which features APAP guided by the forced oscillation technique (APAPfot). DESIGN: A double-blind, randomized, cross-over trial. SETTING: The sleep disorders center and sleep laboratory of a university hospital. PATIENTS AND INTERVENTIONS: An overnight CPAP autotitration procedure was performed in 30 patients with OSA. A split-night protocol allowed that each patient used both devices. MEASUREMENTS AND RESULTS: Using polysomnography, sleep, indexes of sleep-disordered breathing, snoring, and CPAP levels were recorded. No significant differences were found in conventional sleep variables. While the apnea-hypopnea index (AHI) was lower with APAPfl (3.5 +/- 5.6/h) as compared to APAPfot (9.9 +/- 31.0/h), the difference was not statistically significant (mean +/- SD). The snoring index, however, was significantly lower with APAPfl (35.3 +/- 53.7/h vs 111.6 +/- 175.4/h, respectively; p = 0.01). The median and 95th percentile pressure levels rose from wakefulness to sleep in APAPfl, but decreased in APAPfot. Higher pressure variability was present in the latter method. CONCLUSIONS: These findings suggest that the APAPfl is superior to APAPfot in the control of snoring. While a lower AHI was achieved with APAPfl, at the expense of a higher median pressure but less pressure variability, the difference with APAPfot was not statistically significant.     

Bilevel positive airway pressure worsens central apneas during sleep

STUDY OBJECTIVES: While most patients with sleep-disordered breathing are treated with continuous positive airway pressure (CPAP), bilevel positive airway pressure (BLPAP) is often used. Having observed that BLPAP therapy increased central apneas in some of our patients undergoing sleep studies, we conducted this study to evaluate the effects of BLPAP. DESIGN: Retrospective analysis of all sleep studies performed in an outpatient sleep center that used BLPAP over a 2-year period. We assessed the incidence and frequency of events during rapid eye movement (REM) sleep and non-REM sleep during baseline conditions, CPAP, and BLPAP. Desaturations, hypopneas, obstructive apneas, and central events, including periodic breathing (PB), Cheyne-Stokes respiration (CSR), and non-CSR central apneas were evaluated. PATIENTS: Ninety-five of the 719 patients who underwent sleep studies met inclusion criteria. Eighty of the 95 patients treated with BLPAP were also treated with CPAP. RESULTS: BLPAP was more likely to worsen than improve CSR (p = 0.002), non-CSR central apneas (p < 0.001), and CSR or PB (p < 0.001). CSR (p = 0.03) and non-CSR central apneas (p = 0.01) were more likely to worsen with BLPAP (24% and 23%, respectively) than with CPAP (11% and 8%). Central events (p = 0.04) and CSR (p = 0.009) were more likely to worsen during BLPAP in patients with baseline CSR or PB (62% and 48%, respectively) than develop in those without baseline CSR or PB (34% and 18%). Higher BLPAP differences worsened central events in 28% of patients, while 7% improved (p = 0.02). During REM sleep, central apneas improved, while hypopneas and obstructive apneas worsened (p < 0.001). CONCLUSIONS: BLPAP often increases the frequency of CSR and non-CSR central apneas during sleep. Since CSR has adverse effects on cardiac function and sleep, it is important to consider this possible adverse effect of BLPAP.     

Bench evaluation of flow limitation detection by automated continuous positive airway pressure devices

STUDY OBJECTIVE: Automatic continuous positive airway pressure (CPAP) devices that adjust the pressure delivered to the patient are now available to treat sleep-disordered breathing. Sophisticated auto-CPAP devices can detect and correct flattened inspiratory flow contours (FIFCs) associated with subtle upper airway obstruction. However, evaluations of their performance are made difficult by differences across patients and devices. We performed a bench study of five commercially available auto-CPAP devices using a breath waveform simulator to evaluate sensitivity for detecting flattened inspiratory flow. DESIGN: Five degrees of FIFC were simulated. In addition, normal and abnormal flow contours from patients published in the literature were evaluated. MEASUREMENTS AND RESULTS: One device showed autotriggering leading to CPAP increases, and another device varied the CPAP level independently from the presence of an FIFC. The three remaining devices differed regarding the detection of FIFCs and the means used to increase CPAP. CONCLUSION: Based on the characteristics of each patient, physicians must choose among devices with different thresholds of FIFC detection and different pressure responses to detection. Therefore, physicians need details on the algorithms used in auto-CPAP devices. Manufacturers should supply detailed algorithms.     

Randomized short-term trial of two autoCPAP devices versus fixed continuous positive airway pressure for the treatment of sleep apnea

We evaluated the efficacy of two different continuous positive airway pressure devices with automatic mask pressure adjustment (autoCPAP) in comparison with fixed CPAP in treating obstructive sleep apnea syndrome in 29 patients. The mean (+/- SE) apnea-hypopnea index was 46 +/- 4 per hour and the Epworth score was 14.2 +/- 0.7. Patients were treated over three consecutive 1-month periods with three regimens in random order: an autoCPAP device responding to apnea-hypopnea and snoring, another autoCPAP device responding to snoring and changes in flow contour, and fixed CPAP at the 90th pressure percentile titrated by autoCPAP over 2 weeks. Allowed pressure in the autoCPAP mode was 4 to 15 cm H2O. At the end of each treatment period, symptoms, quality of life, vigilance, and nocturnal breathing disturbances were evaluated. All three treatment modalities improved symptoms, quality-of-life domains, and apnea-hypopnea index significantly and to a similar degree. Mean (+/- SE) maintenance-of-wakefulness time increased by 4.5 +/- 1.8, 6.0 +/- 1.5, and 6.1 +/- 1.4 minutes with DeVilbiss AutoAdjust LT, AutoSet T, and fixed-pressure CPAP, respectively (p<0.001 vs. baseline, p=not significant for comparisons among the three modalities). We conclude that both autoCPAP devices were equally effective as fixed-pressure CPAP in improving major outcomes during short-term therapy of sleep apnea.     

Automatic CPAP Performance in Patients with Sleep Apnea Plus COPD

Abstract

Background: Automatic CPAP devices have demonstrated good results in obtaining optimal fixed CPAP pressure to eliminate respiratory events in patients with sleep apnea-hypopnea syndrome (SAHS). However, automatic CPAP has not been fully studied in patients with COPD plus SAHS. Objectives: To analyse the performance of an automatic CPAP in severe COPD patients compared with SAHS patients with no associated co-morbidity. Methods: We compared 10 consecutive patients with SAHS and no associated co-morbidity and 10 patients with SAHS plus severe COPD who required CPAP titration. Automatic CPAP performance was studied during full-night PSG. Inadequate pressure increase periods, absence of pressure increases in reaction to respiratory events, air leak periods, and pressure behaviour in the face of erratic breathing periods were analysed. Results: The SAHS patients without co-morbidities vs. SAHS plus COPD patients presented: mean sleep efficiency, 80.2 (11.5)% vs. 76.5 (12.1)%; residual AHI, 6.3 (5.2) vs. 5.1 (7.7); residual CT90, 1 (3)% vs. 14 (1)%. The device´s performance demonstrates a mean of 1.2 (1.5) vs. 1.3 (1.2) periods of inadequate pressure increases; absence of pressure increases in reaction to respiratory events, 4.1 (5.4) vs. 0.6 (0.7) times; periods of air leaks, 1.3 (3.8) vs. 13.9 (11.7); mean optimal pressure, 9.1 (1.4) vs. 9.0 (1.9) cm H₂O. Conclusion: Titration with automatic CPAP could be as effective in patients with SAHS plus severe COPD as in patients with SAHS without COPD. However, the presence of more leakages must be taken into account.     

The sleep hypopnea syndrome

We have observed patients who clinically have the obstructive sleep apnea syndrome but have no apneas, instead having recurrent nocturnal hypoventilation. There is disagreement about the definition and significance of such sleep-related hypopneas. We have thus analyzed breathing patterns, oxygenation and sleep records of 50 consecutive patients referred with the clinical features of the sleep apnea syndrome and found to have abnormal breathing during sleep to determine: (1) the best definition of hypopnea, and (2) how frequently patients have the clinical features of the sleep apnea syndrome without recurrent apneas. Hypopnea definitions based on decreases in thoracoabdominal movement yielded hypopnea frequencies that were significantly closer to desaturation and arousal frequencies than hypopnea definitions based on flow reduction. The best hypopnea definition was that of a 50% reduction in thoracoabdominal movement lasting for 10 s. This was validated in 33 normal subjects, all of whom had fewer than 11 hypopneas/h, and fewer than 14 apneas plus hypopneas/h of sleep. Thirty-two of the 50 patients had 10 or more apneas/h, the remaining 18 having 9 to 98 hypopneas/h such that all patients had more than 16 apneas plus hypopneas/h. Patients with recurrent hypopneas were clinically indistinguishable from and had a similar frequency of 4% desaturations (zero to 104/h) and arousals (7 to 98/h) to the patients with frequent apneas. This study confirms that hypopneas are clinically important and that the "sleep apnea syndrome" may occur in the absence of recurrent apneas.     

82例睡眠呼吸暂停低通气综合征的诊断与无创正压通气治疗

目的探讨睡眠呼吸暂停综合征(SAHS)的诊断及自动调节持续气道内正压通气(auto-CPAP)对SAHS的治疗价值。方法82例SAHS患者,均行整夜的多导睡眠仪监测,并对18例中重度患者进行auto-CPAP治疗。结果SAHS患者随病情加重Epworth评分、呼吸紊乱程度、最长呼吸暂停时间、鼾声指数、氧减指数等参数明显增加,最低氧饱和度明显降低。Auto-CPAP治疗后呼吸紊乱和低氧血症的程度显著减轻,中枢性呼吸暂停的次数及所占时间没有明显改变。Epworth评分与呼吸紊乱、低氧血症以及打鼾的的时间和次数有明显的相关关系。结论Auto-CPAP可有效的治疗中重度SAHS患者,消除阻塞性及混合性呼吸暂停,减轻低氧血症,明显改善症状,并具有良好的接受性。夜间频繁出现的低氧血症是导致日间过度嗜睡的重要因素。     

New Technologies to Detect Static and Dynamic Upper Airway Obstruction During Sleep

Increase in upper airway resistance is the main patho-physiological feature in the obstructive breathing disorders during sleep. Upper airway events may be divided into two main groups: static obstruction (apneas) and dynamic obstruction (hypopneas, flow limitation, and snoring). This classification is useful to provide better information about the patho-physiological mechanisms of obstruction and to better define the diagnostic tools necessary for detecting abnormal respiratory events during sleep. Detection of dynamic obstruction requires sensors with a good frequency response. As thermistors have a poor dynamic response, they are not efficient in detecting the dynamic obstruction but are good enough to detect static obstruction. Nasal prongs (NP) connected a to pressure transducer and the impedance signal measured by the forced oscillation technique (FOT) are relatively new tools to noninvasively investigate dynamic upper airflow obstruction during sleep. FOT provides a direct index of the magnitude of airway obstruction and, therefore, of the upper airway patency, even under conditions of no flow (apneas). NP are aimed at assessing flow. Thus, both techniques have a different scope. The main advantages of NP are that they are easy to use and do not require sophisticated technology, while FOT needs a more complex instrumentation. For clinical routine studies NP are probably the best and simplest method for assessing the different respiratory events during sleep. However, FOT would be particularly useful in selected applications such as assessing upper airway patency in some central apneas; interpreting the irregular pattern of breathing during REM sleep; in better characterizing the inspiratory flow-limited breaths classified as intermediate; and in studying upper airway mechanics.     

Comparison of conventional nighttime with automatic or manual daytime CPAP titration in unselected sleep apnea patients: study of the usefulness of daytime titration studies

Daytime CPAP titration studies with full polysomnography have been successfully performed in patients with severe sleep apnea-hypopnea syndrome (SAHS). The implementation of daytime studies in unselected SAHS patients could help to reduce the waiting lists for CPAP titrations. The main purpose of this study was to compare the effectiveness of conventional versus manual or automatic daytime CPAP titration in unselected patients with SAHS. Ninety-three consecutive patients with SAHS in whom CPAP was indicated were assigned to conventional titration or to manual or automatic (AutoSet) daytime CPAP titration, after sleep deprivation. The number of valid studies, sleep architecture, final pressure selected and mean pressure in the different sleep stages were compared. Changes in sleepiness (Epworth sleepiness score) and hours of CPAP use were assessed after 3 months of treatment. Four patients did not sleep (3 AutoSet, 1 conventional daytime groups). Sleep latency was shorter during automatic daytime titration whereas REM latency was shorter in daytime studies; the percentage of sleep stages was similar during all types of titration. CPAP requirements were significantly higher during REM sleep in conventional and manual daytime titrations while mean pressure was unchanged throughout sleep stages during AutoSet titration. CPAP pressure selected with conventional or daytime manual titration (7.5(2.2) cm H2O and 7.4(1.5) cm H2O, ns) were significantly lower (P< 0.001) than with AutoSet (9.4(1.6) cm H20. All groups showed similar decrease of sleepiness and hours of use of CPAP at 3 months of follow-up. Automatic and manual daytime PSG studies after sleep deprivation are useful for CPAP titration in unselected patients with SAHS. Pressure selected with AutoSet is significantly higher than with conventional daytime or nighttime titration, although not significant in terms of treatment compliance and symptom improvement.     

Reversal of central sleep apnea using nasal CPAP

Based on the theory that obstructive (OSA) and central (CSA) sleep apneas share common pathophysiologic mechanisms, we attempted to treat eight patients with predominantly CSA by continuous positive airway pressure (CPAP). All patients exhibited repetitive episodes of CSA and mixed sleep apneas (MSA) in the supine position with a mean duration of 23.7 +/- 0.7 s and 34.5 +/- 1.3 s, respectively. The pattern of apnea changed when the subject lay in the lateral position. Five patients were observed to develop OSA in the lateral position with a mean duration of 27.2 +/- 1.5 s, while the other three patients snored continuously. High levels of CPAP (range 9.0 to 16.5 cm H2O) prevented all CSA and MSA and resulted in quiet breathing in all eight patients. Intermediate levels of CPAP produced firstly MSA, then purely OSA and/or continuous snoring. Low levels of nasal CPAP also prevented OSA and snoring occurring in the lateral posture in all subjects (range 2.0 to 8.3 cm H2O). Three patients are currently on home CPAP therapy for a range of four to 36 months. We conclude that upper airway collapse in the supine posture has a key role in the induction of CSA. We suggest that a reflex inhibition of respiration through activation of supraglottic mucosal receptors during passive oropharyngeal airway closure caused CSA in these patients.     

Constant vs auto-continuous positive airway pressure in patients with sleep apnea hypopnea syndrome and a high variability in pressure requirement

STUDY OBJECTIVES: Auto-continuous positive airway pressure (CPAP) has been reported to have no more efficacy than constant CPAP in unselected patients with sleep apnea hypopnea syndrome (SAHS). The aim of this study was to evaluate patients judged to be good candidates for auto-CPAP because of a high within-night variability in pressure requirement. DESIGN: Single-blind, randomized, cross-over study (2 x 8 weeks) to compare auto-CPAP with constant CPAP. PATIENTS: Outpatients with moderate-to-severe SAHS attending the chest clinic. INTERVENTIONS: Patients were equipped at home in the auto-CPAP mode (model GK418A; Malinckrodt; Nancy, France), using a 4- to 14-cm H(2)O pressure range. Those individuals having a high within-night variability in pressure requirement, assessed at the end of a 14-day run-in period, were included in the cross-over study. Auto-CPAP was compared with constant CPAP (according to a titration night in the sleep laboratory) in terms of compliance, efficacy on apneas (assessed from the pressure monitor), and sleepiness (assessed on the Epworth sleepiness scale). MEASUREMENTS AND RESULTS: Of 90 consecutive patients with SAHS, 27 patients were selected for a within-night variability in pressure requirement exceeding a given threshold. After completion of the cross-over, 24 patients were evaluable. The median percentage of nights the machine was used was 95.5% (range, 45 to 100%) on constant CPAP, and 96.5% (range, 40 to 100%) on auto-CPAP; the median apnea index recorded by the device was 0.40/h (range, 0 to 2.40/h) on constant CPAP, and 0.45/h (range, 0 to 5.80/h) on auto-CPAP (differences not significant). The mean Epworth sleepiness score was significantly (p < 0.01) lower on auto-CPAP (5.1; SD, 2.8) than on constant CPAP (6.1; SD, 2.8). CONCLUSIONS: In patients selected for a high within-night variability in pressure requirement, auto-CPAP administered via a GK418A device was equivalent to constant CPAP based on a titration night in the sleep laboratory. Subjective ratings for sleepiness were slightly lower on auto-CPAP.     

Physiological consequences of prolonged periods of flow limitation in patients with sleep apnea hypopnea syndrome

Flow limitation during sleep occurs when the rise in esophageal pressure is not accompanied by a flow increase which results in a non-rounded inspiratory flow shape. Short periods of flow limitation ending in an arousal or in a fall in SaO2 (hypopnea or upper airway resistance syndrome) are detrimental but the role of prolonged periods of flow limitation (PPFL) has not yet been clarified. This is important not only for diagnosis but also for nasal continuous positive airway pressure (CPAP) titration, especially for the automatic devices that need to be setup. The aim of this study was to analyze the effects of PPFL. We compared the behavior of the mean end-expiratory systemic blood pressure (SBP), end-tidal CO2, esophageal pressure and the pattern of breathing during a period of normal breathing at optimal (CPAP) and during PPFL at suboptimal CPAP in 14 patients with sleep apnea/hypopnea syndrome during a full polysomnography CPAP titration. The mean values of the parameters studied, at optimal and suboptimal CPAP were (1) SBP 92+/-13 vs. 91+/-15 mmHg (P: ns). At suboptimal CPAP, swings of blood pressure were associated with changes in pleural pressure; (2) SaO2 97.5+/-1.2 vs. 96.5+/-1.6 (P: 0.03), (3) end-tidal CO2 43.5+/-4 vs. 49.5+/-4 (P:0.001); (4) oesophageal pressure, 10.5+/-4 vs. 37.6+/-15 cmH2O (P:0.001) and (5) pattern of breathing: minute ventilation 6.6+/-1.4 vs. 6.1+/-1.2L/min (P: ns) and inspiratory time 1.24+/-0.3 vs. 1.66+/-0.4s (P:0.001). It can be concluded that PPFL induces significant physiological changes. Nevertheless, given the scant literature, clinical studies are warranted to elucidate the clinical role of these physiological changes.     

Obstructive pressure peak: a new method for differentiation of obstructive and central apneas under auto-CPAP therapy

Purpose

Auto-CPAP devices (APAP) are controlled, e.g., by the respiratory flow and pressure to adjust the treatment pressure to the variable obstruction in sleep apnea syndromes. By obstruction of the upper airway during inspiration, a pressure difference between the lower airways and the mask can be measured. In case of an opening of the pharynx at the end of the obstruction, the pressure decreases immediately. This brief negative pressure, the so-called obstructive pressure peak (OPP) can be used to identify obstruction or open airways with the algorithm of an APAP device. Useless pressure increases, e.g., after central apneas without obstruction may be avoided. We therefore investigated the association of the OPP signal with respiratory events during APAP therapy.

Methods

In this pilot study, 13 patients with obstructive sleep apnea syndrome were evaluated. Attended automatic CPAP titration (SOMNObalance, Fa Weinmann Hamburg/Germany) was performed. The OPP signal was recorded synchronously in parallel with the polysomnographic data. If the OPP signal was within a time range of ±5 s of the resumption of normal breathing, it was assigned to the event.

Results

A total of 480 sleep-related breathing disorders events were studied. The most common were the mixed apneas associated with more than 90% of all cases with an OPP signal, followed by obstructive sleep apneas (66.7%) and central apneas (38%). The difference in OPP frequency distribution between central apneas and obstructive apneas was significant with p?<?0.001.

Conclusions

The analysis of the pressure characteristics of APAP treatment with the registration of OPP allows a further differentiation in obstructed and not obstructed upper airways.     

Sleep-disordered breathing associated with long-term opioid therapy

Three patients are described who illustrate distinctive patterns of sleep-disordered breathing that we have observed in patients who are receiving long-term, sustained-release opioid medications. Polysomnography shows respiratory disturbances occur predominantly during non-rapid eye movement (NREM) sleep and are characterized by ataxic breathing, central apneas, sustained hypoxemia, and unusually prolonged obstructive "hypopneas" secondary to delayed arousal responses. In contrast to what is usually observed in subjects with obstructive sleep apnea (OSA), oxygen desaturation is more severe and respiratory disturbances are longer during NREM sleep compared to rapid eye movement sleep. Further studies are needed regarding the effects of opioids on respiration during sleep as well as the importance of interaction with other medications and associated risk factors for OSA.     

Kritische Standortbestimmung zur apparativen Therapie schlafbezogener Atmungsstörungen

The administration of therapy with positive airway pressure (PAP) represents the standard option in the treatment of sleep-related breathing disorders (SRBD). Several modifications of continuous positive airway pressure (CPAP) have been developed in order to improve patient adherence, to most precisely address defined phenotypes of SRBD and to optimally focus on combinations of different disorders. The use of the different algorithms and devices requires a clear discrimination of phenotypes of SRBDs to avoid insufficient, inadequate and false therapies. As a first step, the physician has to define if the prevailing breathing disturbance has to be treated at all which depends on limitations of the quality of life, increased risk of accidents and any existing or imminent comorbidities. Although automatic CPAP (APAP) or bilevel PAP (BPAP) in spontaneous mode are not generally superior to CPAP, they allow individual treatment approaches. A short-term treatment trial with CPAP is indicated in most patients with central breathing disturbances; however, adaptive servoventilation or BPAP in spontaneous-timed mode or non-invasive ventilation have proven to be more efficient in treating patients with Cheyne-Stokes respiration, hypoventilation syndromes, coexisting obstructive and central sleep apnea, complex sleep apnea or atactic breathing. During the stay in the sleep laboratory, devices and interfaces are individually selected according to the specific requirements of the patient. Treatment pressure is titrated and the patient is educated in the use and care of the device. As the first days of therapy are of crucial importance for long-term adherence, any delay in the supply of the device, changes of the device for non-medical reasons and insufficient follow-up have to be avoided.