Accuracy of an unattended home CPAP titration in the treatment of obstructive sleep apnea

Different Continuous Positive Airway Pressure Titration Modalities in Obstructive Sleep Apnea Syndrome Patients

Background

Patients with obstructive sleep apnea syndrome are mainly treated with continuous positive airway pressure. Polysomnography-guided full-night manual titration is the gold standard for continuous positive airway pressure titration, but it is cost-, time-, and effort-consuming. Alternative ways of titration are easier with less cost, time, and effort. In the era of the COVID-19 pandemic, the need to establish more safe strategies is increased.

Aim

To choose a rapid, efficient, simple, and safe method with less effort and cost in the measurement of a suitable level of positive airway pressure in the management of obstructive sleep apnea syndrome.

Methods

This study enrolled 48 adult patients who had been diagnosed with obstructive sleep apnea syndrome at our sleep unit and were candidates for treatment with continuous positive airway pressure according to AASM 2008 after exclusion of other sleep-related breathing disorders. All patients underwent both laboratory full-night manual titration and auto-titration (by Prisma20A of WEINMANN medical technology, Germany). Manual titration pressure and P95 of auto-titration were obtained and compared with calculated pressures by five predictive formulas (Miljeteig and Hoffstein, Sériès, Stradling, Loredo, and Lee).

Results

Patients included in the study were 25 females (52.1%) and 23 males (47.9%) with a mean±SD of age of 49.98±10.36 years. Mean±SD of manual pressure was 10.44±2.49 cmH₂O, P95 was 10.16±2.64 cmH₂O, and calculated pressures by different equations were: Miljeteig and Hoffstein, 8.53±2.03; Sériès, 11.40±1.81; Stradling, 9.68±1.65; Loredo, 9.90±1.79; and Lee, 10.61±2.68 cmH₂O. No significant differences were reported between manual pressure and pressures of auto-titration with Sériès, Stradling, Loredo, and Lee equations (p=0.112, 0.09, 0.212, 0.213, and 0.657, respectively).

Conclusion

Auto-titration can be used as an effective alternative to manual titration with less cost and effort and is more comfortable to patients. Predictive formulas can be used instead of standard and auto-titration especially in resource-limited facilities and in pandemics.

Using craniofacial characteristics to predict optimum airway pressure in obstructive sleep apnea treatment

Introduction

Manual titration is the gold standard to determinate optimal continuous positive airway pressure, and the prediction of the optimal pressure is important to avoid delays in prescribing a continuous positive airway pressure treatment.

Objective

To verify whether anthropometric, polysomnographic, cephalometric, and upper airway clinical assessments can predict the optimal continuous positive airway pressure setting for obstructive sleep apnea patients.

Methods

Fifty men between 25 and 65 years, with body mass indexes of less than or equal to 35 kg/m² were selected. All patients had baseline polysomnography followed by cephalometric and otolaryngological clinical assessments. On a second night, titration polysomnography was carried out to establish the optimal pressure.

Results

The average age of the patients was 43 ± 12.3 years, with a mean body mass index of 27.1 ± 3.4 kg/m² and an apnea–hypopnea index of 17.8 ± 10.5 events per hour. Smaller mandibular length (p = 0.03), smaller atlas–jaw distance (p = 0.03), and the presence of a Mallampati III and IV (p = 0.02) were predictors for higher continuous positive airway pressure. The formula for the optimal continuous positive airway pressure was: 17.244 − (0.133 × jaw length) + (0.969 × Mallampati III and IV classification) − (0.926 × atlas–jaw distance).

Conclusion

In a sample of male patients with mild-to-moderate obstructive sleep apnea, the optimal continuous positive airway pressure was predicted using the mandibular length, atlas–jaw distance and Mallampati classification.

Impact of Mask Type on the Effectiveness of and Adherence to Unattended Home-Based CPAP Titration

OBJECTIVES

To compare interfaces performance during home-based automatic titration (APAP).

METHODS

Retrospective study based on APAP titration from Obstructive Sleep Apnea Syndrome (OSA) patients.

RESULTS

707 patients, 513 men (70.6%), were titrated. Masks were 104 pillows (14.7%), group I (GI); 532 nasal (75.2%), group II (GII); and 71 oronasal masks (10%), group III (GIII). We found differences in effective pressure to the device (P90/P95) (GI: 7.13±1.9 vs. GII: 8.3±2.1 vs. GIII: 9.3±2.6 cmH2O, p <0.001) but not in final pressure titrated manually (GI: 7.9±1.4 vs. GII: 8.6±1.6 vs. GIII: 9.2±1.9 cm of H2O, p >0.5), where lower residual AHI for pillows was p <0.001 and leaks for nasal were p <0.001. No differences were found in compliance (hours) (GI: 6.3±1.2 vs. GII: 6.2±1.1 vs. GIII: 6.1±1.0, p <0.4).

CONCLUSION

During auto-adjusting titration by CPAP-naïve patients, nasal masks had lower leak rates and nasal pillows presented a similar performance.

Mathematical Equations to Predict Positive Airway Pressures for Obstructive Sleep Apnea: A Systematic Review

Objective. To systematically review the international literature for mathematical equations used to predict effective pressures for positive airway pressure (PAP) devices. Methods. Google Scholar, PubMed, Scopus, Embase, Web of Science, CINAHL, and The Cochrane Library were searched through June 27, 2015. The PRISMA statement was followed. There was no language limitation. Results. 709 articles were screened, fifty were downloaded, and twenty-six studies presented equations that met the inclusion and exclusion criteria. In total, there were 4,436 patients in the development phases and 3,489 patients in the validation phases. Studies performed multiple linear regressions analyses as part of the equation(s) development and included the following variables: physical characteristics, polysomnography data, behavioral characteristics, and miscellaneous characteristics, which were all predictive to a variable extent. Of the published variables, body mass index (BMI) and mean oxygen saturation are the most heavily weighted, while BMI (eighteen studies), apnea-hypopnea index (seventeen studies), and neck circumference (eleven studies) were the variables most frequently used in the mathematical equations. Ten studies were from Asian countries and sixteen were from non-Asian countries. Conclusion. This systematic review identified twenty-six unique studies reporting mathematical equations which are summarized. Overall, BMI and mean oxygen saturation are the most heavily weighted.

The predictive value of Muller's maneuvre for CPAP titration in OSAHS patients

To investigate the role of awake upper airways (UA) endoscopy assessment as a parameter of prediction for CPAP titration in OSAHS patient therapy. Retrospective analysis of UA endoscopic assessment with Mueller's maneuvre and the application of the nose oropharynx hypopharynx score (NOHs) was conducted to obtain a numeric score representing the grade of severity of UA obstruction. Other commonly used predictive parameters for CPAP titration were also included in the study: anthropometric [BMI, neck circumference (NC)] and polysomnographic parameters (AHI, ODI). 3 groups of patients were identified: (1) 67/90 patients requiring intermediate CPAP values, (2) 13/90 patients requiring high CPAP values, and (3) 10/90 patients requiring low pressure values. BMI (p = 0.0013) was the only monitored parameter to show significant statistical value as a CPAP titration predictor. However, higher values of anthropometric parameters (NOHs ≥9, BMI >35, NC >45) showed a sensitivity of 69.2% as a single parameter and 76.9% as combined parameters, and specificity between 66.2 and 72.7% as a single parameter and 43.4% as combined parameters, unequivocally identifying patients requiring high therapeutic CPAP value. A lower cut-off of anthropometric parameters (NOHs ≤6, BMI ≤29, NC <42) showed sensitivity between 40 and 60% as a single parameter and of 90% as combined parameters, and specificity between 68.7 and 80.2% as a single parameter which increased to 93.7% as combined parameters, identifying patients requiring a low therapeutic CPAP value. The results show that anthropometric and polygraphic parameters have no significant independent predictive value for CPAP titration, with the exception of BMI. However, anthropometric parameters showed good levels of sensitivity and specificity in OSAHS patients requiring high or low levels of CPAP therapy.

Determination of new prediction formula for nasal continuous positive airway pressure in Turkish patients with obstructive sleep apnea syndrome

BACKGROUND

Race/ethnicity may play an important role in determining body size, severity of obstructive sleep apnea syndrome (OSAS), and effective continuous positive airway pressure (CPAP) (Peff). Turkey is composed of different ethnic groups. Therefore, the aims of this study were to determine new prediction formula for CPAP (Ppred) in Turkish OSAS patients, validate performance of this formula, and compare with Caucasian and Asian formulas.

METHODS

Peff of 250 newly diagnosed moderate-to-severe OSAS patients were calculated by in-laboratory manual titration. Correlation and multiple linear regression analysis were used to model effects of ten anthropometric and polysomnographic variables such as neck circumference (NC) and oxygen desaturation index (ODI) on Peff. New formula was validated in different 130 OSAS patients and compared with previous formulas.

RESULTS

The final prediction formula was [Formula: see text]. When Peff of control group was assessed, it was observed that mean Peff was 8.39 ± 2.00 cmH(2)O and Ppred was 8.23 ± 1.22 cmH(2)O. Ppred was within ±3 cmH(2)O of Peff in 96.2% patients. Besides, Peff was significantly correlated with new formula, and prediction formulas developed for Caucasian and Asian populations (r = 0.651, p < 0.001, r = 0.648, p < 0.001, and r = 0.622, p < 0.001, respectively).

CONCLUSIONS

It is shown that level of CPAP can be successfully predicted from our prediction formula, using NC and ODI and validated in Turkish OSAS patients. New equation correlates with other formulas developed for Caucasian and Asian populations. Our simple formula including ODI, marker of intermittent hypoxia, may be used easily in different populations.

Predictive equations for CPAP titration in OSAS patients

BACKGROUND

Continuous positive airway pressure (CPAP) is the elective treatment of obstructive sleep apnea. The therapeutic level of CPAP is generally established by manual titration or an auto CPAP device, but an alternative way involves the use of predictive formulas. The aim of the present study was to test the difference between mathematical equations and CPAP or auto CPAP in terms of therapeutic pressure.

METHODS

A retrospective analysis of 197 subjects with a diagnosis of obstructive sleep apnea needing a CPAP treatment was performed. The patients were divided into two groups: the first one included patients who had received CPAP after manual titration and the second one included patients who had received auto CPAP titration. The therapeutic CPAP pressure was then compared to the pressure calculated by three different equations: Eq. A by Stradling, Eq. B by Sériès, and Eq. C by Hoffstein.

RESULTS

One hundred ninety-seven patients were included in the study, 110 were titrated by auto CPAP and 87 by manual titration. There was a positive correlation between the pressure defined by the three equations and both titration methods, but each equation usually gave a higher pressure with patients needing CPAP <8 and lower for patients needing CPAP >11. Equation C normally gave a lower result than the other two equations.

CONCLUSIONS

Manual or auto CPAP titration remains the best way to define the appropriate CPAP. However, predictive formulas can be useful if used with caution and always after verifying the real efficacy, particularly for patients needing higher pressure.

Utility of formulas predicting the optimal nasal continuous positive airway pressure in a Greek population

BACKGROUND

There have been reports that optimal CPAP pressure can be predicted from a previously derived formula, with the Hoffstein formula being the most accurate and accepted in the literature so far. However, the validation of this predictive model has not been applied in different clinical settings. Our aim was to compare both the Hoffstein prediction formula and a newly derived formula to the CPAP pressure setting assessed during a formal CPAP titration study.

METHODS

We prospectively studied 1,111 patients (871 males/240 females) with obstructive sleep apnea hypopnea syndrome (OSAHS) undergoing a CPAP titration procedure. In this large population sample, we tested the Hoffstein formula, utilizing body mass index (BMI), neck circumference and apnea/hypopnea index (AHI), and we compared it with our new formula that included not only AHI and BMI but also smoking history and gender adjustment.

RESULTS

We found that using the Hoffstein prediction formula, successful prediction (predicted CPAP pressure within ±2 cm H(2)O compared to the finally assessed optimum CPAP pressure during titration) was accomplished in 873 patients (79%), with significant correlation between CPAP predicted pressure (CPAPpred(1)) and the optimum CPAP pressure (CPAPopt) [r = 0.364, p < 0.001]. With the new formula, including smoking history and gender adjustment, successful prediction was accomplished in 1,057 patients (95%), with significant correlation between CPAP predicted pressure (CPAPpred(2)) and the CPAPopt (r = 0.392, p < 0.001). However, there was a highly significant correlation between the two formulas (r = 0.918, p < 0.001).

CONCLUSIONS

We conclude that the level of CPAP necessary to abolish sleep apnea can be successfully predicted from both equations, using common clinical measurements and prediction formulas that may be useful in calculating the starting pressure for initiating CPAP titration. It may also be possible to shorten CPAP titration and perhaps in selected cases to combine it with the initial diagnostic study.

Practice parameters for the use of autotitrating continuous positive airway pressure devices for titrating pressures and treating adult patients with obstructive sleep apnea syndrome: an update for 2007. An American Academy of Sleep Medicine report

These practice parameters are an update of the previously published recommendations regarding the use of autotitrating positive airway pressure (APAP) devices for titrating pressures and treating adult patients with obstructive sleep apnea syndrome. Continuous positive airway pressure (CPAP) at an effective setting verified by attended polysomnography is a standard treatment for obstructive sleep apnea (OSA). APAP devices change the treatment pressure based on feedback from various patient measures such as airflow, pressure fluctuations, or measures of airway resistance. These devices may aid in the pressure titration process, address possible changes in pressure requirements throughout a given night and from night to night, aid in treatment of OSA when attended CPAP titration has not or cannot be accomplished, or improve patient comfort. A task force of the Standards of Practice Committee of the American Academy of Sleep Medicine has reviewed the literature published since the 2002 practice parameter on the use of APAP. Current recommendations follow: (1) APAP devices are not recommended to diagnose OSA; (2) patients with congestive heart failure, patients with significant lung disease such as chronic obstructive pulmonary disease; patients expected to have nocturnal arterial oxyhemoglobin desaturation due to conditions other than OSA (e.g., obesity hypoventilation syndrome); patients who do not snore (either naturally or as a result of palate surgery); and patients who have central sleep apnea syndromes are not currently candidates for APAP titration or treatment; (3) APAP devices are not currently recommended for split-night titration; (4) certain APAP devices may be used during attended titration with polysomnography to identify a single pressure for use with standard CPAP for treatment of moderate to severe OSA; (5) certain APAP devices may be initiated and used in the self-adjusting mode for unattended treatment of patients with moderate to severe OSA without significant comorbidities (CHF, COPD, central sleep apnea syndromes, or hypoventilation syndromes); (6) certain APAP devices may be used in an unattended way to determine a fixed CPAP treatment pressure for patients with moderate to severe OSA without significant comorbidities (CHF, COPD, central sleep apnea syndromes, or hypoventilation syndromes); (7) patients being treated with fixed CPAP on the basis of APAP titration or being treated with APAP must have close clinical follow-up to determine treatment effectiveness and safety; and (8) a reevaluation and, if necessary, a standard attended CPAP titration should be performed if symptoms do not resolve or the APAP treatment otherwise appears to lack efficacy.

Prediction of continuous positive airway pressure in obstructive sleep apnea

Continuous positive airway pressure (CPAP) prediction formulas can potentially simplify the treatment of obstructive sleep apnea (OSA). However, they can be difficult to derive and validate. We tested a statistical method to derive and validate a CPAP prediction formula using the same sample population. Seventy-six OSA patients underwent polysomnography and CPAP titration. Anthropometric measures, sleep parameters, and the Epworth sleepiness scale (ESS) were evaluated as predictors. All subsets regression was used to determine the optimum number of variables in the model. The Bayes information criterion was used to find the best-fit model. The model was then evaluated by a tenfold cross-validation procedure. Subjects were obese (BMI 31.3 +/- 5.4) and had significant daytime somnolence (ESS 11.9 +/- 5). Mean respiratory disturbance index (RDI) was 53.5 +/- 31.3. The ESS was not predictive of titrated CPAP. The best-fit model included three variables (CPAP(pred) = 30.8 + RDI x 0.03 - nadir saturation x 0.05 - mean saturation x 0.2). This model explained 67% of the variance. Our data and the literature suggest that a combination of two to three factors is predictive of titrated CPAP: RDI, oxyhemoglobin saturation, and obesity. Except for RDI, the specific factors vary in each population. A CPAP prediction formula that explains a high proportion of the titrated CPAP variance can be easily derived from parameters measured during the diagnostic work-up of OSA patients using a unique statistical model that allows derivation and validation of the formula in the same test population.

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.

Does the severity of obstructive sleep apnea predict patients requiring high continuous positive airway pressure?

STUDY OBJECTIVES

To investigate polysomnographic and anthropomorphic factors predicting need of high optimal continuous positive airway pressure (CPAP).

DESIGN

Retrospective data analysis.

PATIENTS

Three hundred fifty-three consecutive obstructive sleep apnea (OSA) patients who had a successful manual CPAP titration in our sleep disorders unit.

MEASUREMENTS AND RESULTS

The mean optimal CPAP was 9.5 +/- 2.4 cm H2O. The optimal CPAP pressure increases with an increase in OSA severity from 7.79 +/- 2.2 in the mild, to 8.7 +/- 1.8 in the moderate, and to 10.1 +/- 2.3 cm H2O in the severe OSA group. A high CPAP was defined as the mean + 1 standard deviation (SD; > or =12 cm H2O). The predictor variables included apnea-hypopnea index (AHI), age, sex, body mass index (BMI), Epworth Sleepiness Scale (ESS), and the Multiple Sleep Latency Test (MSLT). High CPAP was required in 2 (6.9%), 6 (5.8%), and 63 (28.6%) patients with mild, moderate, and severe OSA, respectively. On univariate analysis, AHI, BMI, ESS score, and the proportion of males were significantly higher in those needing high CPAP. They also have a lower MSLT mean. On logistic regression, the use of high CPAP was 5.90 times more frequent (95% confidence interval 2.67-13.1) in severe OSA patients after adjustment for the other variables. The area under the receiver operator curve was 72.4%, showing that the model was adequate.

CONCLUSIONS

Severe OSA patients are much more likely to need high CPAP levels. However, because of the low positive predictive value (only 28.6%), the clinical value of such information is limited. ESS and MSLT did not increase the predictive value for the need for high CPAP.

Effective comparison of two auto-CPAP devices for treatment of obstructive sleep apnea based on polysomnographic evaluation

BACKGROUND

Automatic continuous positive airway pressure (auto-CPAP) machines differ mainly in algorithms used for respiratory event detection and pressure control. The auto-CPAP machines operated by novel algorithms are expected to have better performance than the earlier ones in the treatment of obstructive sleep apnea syndrome (OSAS).

OBJECTIVES

The purpose of this study was to determine the therapeutic characteristics between two different auto-CPAP devices, i.e., the third-generation flow-based (f-APAP) and the second-generation vibration-based (v-APAP) machines, during the first night treatment of OSAS.

METHODS

We retrospectively reviewed the polysomnography (PSG) recordings of 43 OSAS patients who were initially performed an overnight diagnostic PSG to confirm the disease and afterwards received the first night auto-CPAP treatment with using either the f-APAP (n=22) or v-APAP (n=21) device under another PSG evaluation.

RESULTS

There were 13.6% and 61.9% patients who remained a residual apnea/hypopnea index more than 5 during the f-APAP and v-APAP application, respectively (P<0.005). The f-APAP was more effective than the v-APAP in reducing apnea/hypopnea index (P=0.003), hypopnea index (P=0.023) and apnea index (P=0.007), improving the lowest oxygen saturation index (P=0.007) and shortening stage 1 sleep (P=0.016). However, the f-APAP was less sufficient than the v-APAP in reducing arousal/awakening index (P=0.02).

CONCLUSION

These findings suggest that the f-APAP works better than the v-APAP in abolishing breathing abnormities in the treatment of OSAS; however, the f-APAP device might still have some potential limitations in the clinical application.

Role of different nocturnal monitorings in the evaluation of CPAP titration by autoCPAP devices

The aim of the study was to assess how the analysis of different signals recorded during application of automatic continuous positive airway pressure (autoCPAP) devices improves the evaluation of pressure titration in patients with obstructive sleep apnea syndrome (OSAS) naive to treatment. Seventy-two patients underwent nocturnal polysomnography during autoCPAP (Autoset T, ResMed, Sydney, Australia) application. Progressively more complex combinations of signals were analysed in consecutive steps. According to the analysis of oxyhemoglobin saturation (SaO(2)) alone, a fixed CPAP level suitable for treatment could not be identified in 3 subjects. When analysis of posture was added, titration was considered unsatisfactory in 1 more subject, due to a short time spent supine. Further, addition of flow and respiratory movements led to consider titration unsatisfactory in 1 more subject. Analysis of all polysomnographic signals demonstrated a not fully reliable titration in 9 subjects: 1 with short sleep duration, 2 without REM sleep, 4 with a short sleep time spent supine, and 3 subjects (already identified by SaO(2)) with insufficient correction of respiratory disorders even when a relatively high CPAP was administered. Mask leaks did not hamper titration. CPAP titration by automatic devices alone results in imperfect titration in >10% subjects naive to ventilatory treatment. Only polysomnographic recording ensures titration reliability in all patients. Further research is needed to identify simple and economic methods to reliably start the CPAP treatment.

Arbitrary-Pressure Continuous Positive Airway Pressure for Obstructive Sleep Apnea Syndrome

Current resources are inadequate to meet the demand for polysomnography, resulting in long waiting lists. This study aimed to evaluate the role of arbitrary-pressure continuous positive airway pressure (CPAP) as a method to reduce delays in commencing treatment. The study was of an open, randomized, parallel design. Ninety-one subjects with obstructive sleep apnea syndrome were randomized to either arbitrary-pressure CPAP based on body mass index before treatment polysomnography or to CPAP at settings determined by polysomnography. Both interventions resulted in similar improvements in clinical outcomes as determined by Epworth Sleepiness Score, Short Form-36 Quality of Life questionnaire, objective compliance, and subjective attitudes to treatment. There was higher sleep efficiency at treatment polysomnography in the group commenced at arbitrary pressure (81.8 +/- 10.1% [mean +/- SD] compared with 72.2 +/- 18.0%, p = 0.01). Subjects unable to tolerate CPAP were identified by the use of arbitrary pressure, leading to a reduction in the proportion of "wasted" treatment polysomnograms (studies performed in subjects not persisting with treatment) relative to commencing therapy after treatment polysomnography (3 of 39 compared with 12 of 35, p = 0.01). This approach to initiating treatment with CPAP appears feasible when there are long waiting lists for polysomnography.

Alternative Methods of Titrating Continuous Positive Airway Pressure

Standard practice for continuous positive airway pressure (CPAP) treatment in sleep apnea and hypopnea syndrome (SAHS) requires pressure titration during attended laboratory polysomnography. However, polysomnographic titration is expensive and time-consuming. The aim of this study was to ascertain, in a large sample of CPAP-naive patients, whether CPAP titration performed by an unattended domiciliary autoadjusted CPAP device or with a predicted formula was as effective as CPAP titration performed by full polysomnography. The main outcomes were the apnea-hypopnea index and the subjective daytime sleepiness. We included 360 patients with SAHS requiring CPAP treatment. Patients were randomly allocated into three groups: standard, autoadjusted, and predicted formula titration with domiciliary adjustment. The follow-up period was 12 weeks. With CPAP treatment, the improvement in subjective sleepiness and apnea-hypopnea index was very similar in the three groups. There were no differences in the objective compliance of CPAP treatment and in the dropout rate of the three groups at the end of the follow-up. Autoadjusted titration at home and predicted formula titration with domiciliary adjustment can replace standard titration. These procedures could lead to considerable savings in cost and to significant reductions in the waiting list.

CPAP compliance in sleep apnea patients with and without laboratory CPAP titration

Advances in auto-adjusting positive airway pressure technology for obstructive sleep apnea now permit this treatment to be initiated outside of the sleep laboratory environment, bypassing the need for laboratory-based titration studies. Thus far, little research has addressed how such developments may affect compliance to continuous positive airway pressure (CPAP). We tested the effect of laboratory CPAP exposure and technologist support in a retrospective chart review of 98 veterans with obstructive sleep apnea to determine whether patients who received standard laboratory CPAP titration complied better with CPAP than did patients who received no laboratory CPAP titration. Fifty patients underwent standard technician-attended polysomnography (PSG) with CPAP titration, and 48 patients underwent unattended PSG with no laboratory trial of CPAP (first CPAP exposure was at home). Objective CPAP compliance measures were obtained from CPAP units at follow-up visits. Attended-PSG patients wore CPAP significantly longer per night on average (5.0 hours vs 3.9 hours) and tended to wear CPAP on more nights (76.5% vs 64.2%) compared with unattended-PSG patients. These findings suggest that patients' sleep laboratory experience with CPAP and the support and education provided by sleep technologists are important factors in facilitating CPAP compliance.

A novel, simplified approach to starting nasal CPAP therapy in OSA

BACKGROUND

Due to ever increasing referral rates, we have had to move the nasal CPAP induction program for patients with obstructive sleep apnoea (OSA) out of the sleep laboratories and into an outpatient setting. We report the effects this has had on patient outcomes.

METHODS

The last 75 patients with OSA who had an overnight CPAP titration in the sleep laboratory (group 1) were compared with the first 75 coming to an afternoon clinic and set up on CPAP in groups, and who had their CPAP pressure determined from an algorithm (group 2). They were assessed at 1 and 11 months using the Epworth Sleepiness Score, compliance with CPAP (h/night), whether still using CPAP, and the number of clinic appointments required in the first 11 months.

RESULTS

The two groups were similar at baseline. There were no differences in any of the outcome measures. ESS values fell from 14.6 to 5.0 and from 14.0 to 5.1 at 11 months in groups 1 and 2, respectively: compliance, 5.2 versus 5.1 h/night; clinic appointments, 1.75 versus 1.96; discontinuation rates at 1 month, 8% and 7%, and at 11 months, 25% and 21%.

CONCLUSIONS

Using these simple outcome measures, we have shown that using an outpatient-based approach, and CPAP pressure based on an algorithm, have not reduced the efficacy of our CPAP induction program for patients with OSA.

Evaluation and Comparison of Tranquility and AutoSet T Autotitrating CPAP Machines

The objective of this study was to determine the effectiveness of two autotitrating continuous positive airway pressure (auto-CPAP), the Tranquility (Respironics, Inc., Murrysville, PA, U.S.A.) and the AutoSet T (ResMed Corp., Poway, CA, U.S.A). Patients with obstructive sleep apnea syndrome (OSAS) underwent attended auto-CPAP titration with either the Tranquility or AutoSet T machine. The auto-CPAP machine was given a performance score between 0 and 9. A score of 3 or lower indicated that autotitration had to be discontinued. Sixty patients were studied, 35 patients with the Tranquility machine and 25 patients with the AutoSet T machine. The mean age was 55.4 years, whereas the mean body mass index (BMI) was 32.7. The mean respiratory disturbance index (RDI) was 37.5, and the mean arousal index before use of auto-CPAP was 41.4. The two treatment groups were comparable in age, BMI, RDI, and arousal index. The mean performance scores for the Tranquility and AutoSet T machines were not statistically different. Autotitration with the Tranquility machine had to be discontinued in 10 of the 35 patients (29%), whereas with the AutoSet T machine, autotitration was discontinued in 11 of the 25 patients (44%). Despite advances in auto-CPAP machines, there remains a large minority of patients with OSAS in whom these machines do not accomplish treatment goals. At this time, these machines are not a substitute for in-laboratory CPAP titration polysomnograms.

Continuous positive airway pressure: new generations

Automatic positive airway pressure devices are the most technologically advanced positive airway pressure devices available for use in OSA. Although heterogeneous, they have in common the ability to detect and respond to changes in upper airway resistance. Data cannot necessarily be extrapolated from one device to another, and the field is rapidly advancing. Most studies of APAP have been performed in a supervised setting, or patients have been carefully selected to have a high likelihood of OSA uncomplicated by disorders such as alveolar hypoventilation or central apnea or technical problems such as mask leaks. Studies of APAP for the diagnosis of OSA have shown that APAP can diagnose severe OSA effectively, but the diagnosis of mild-moderate OSA is less reliable. APAP devices also can be effective therapy for selected patients with OSA, with overall similar results to conventional fixed CPAP in terms of respiratory disturbances, sleep quality, nocturnal oxygenation, and daytime sleepiness and performance, with less known or other long-term outcomes. In most studies, mean treatment pressures are lower, without change in side effect profile. Compliance and preference with APAP are similar to or somewhat better than CPAP in most studies. APAP also can be used in an attended setting to titrate an effective pressure for use in long-term conventional CPAP therapy, also with similar results to CPAP in many patients. APAP devices are more expensive than CPAP devices, but the cost may be outweighed if a group of patients who can be diagnosed, treated, or titrated safely in the unattended setting can be identified. Although diagnostic and therapeutic algorithms for APAP have been proposed, the best candidates for this modality must be defined better.

Nonattended home automated continuous positive airway pressure titration: comparison with polysomnography

OBJECTIVE

Automatic adjusting nasal continuous positive airway pressure titration (APAP) has been introduced as an alternative method of establishing pressures for patients with sleep apnea. The performance and accuracy of APAP in nonattended home environment are controversial. This study assessed APAP polysomnographic outcomes and accuracy in a nonattended home environment.

STUDY DESIGN AND SETTING

We conducted a retrospective consecutive case series of 24 consecutive patients who had nonattended APAP and simultaneous full polysomnography (PSG).

RESULTS

APAP was tolerated and reduced obstructive Apnea-Hypopnea Index (AHI) to <10 events/h in all patients. Mean AHI decreased from 38.4 (21.2) to 5.9 (6.6) events/h. Central apneas worsened in one patient. A therapeutic pressure was determined in 91% of patients. Autoset accurately measured residual AHI compared with PSG (R = 0.77, P < 0.001). APAP overestimated the AHI by 1.4 events/h.

CONCLUSIONS

Nonattended APAP is successful in many patients in determining a therapeutic positive pressure setting. Reported AHI via Autoset is similar to that of PSG.

SIGNIFICANCE

APAP reduces AHI and is tolerated in a nonattended environment.

Effects of continuous positive airway pressure on upper airway inspiratory dynamics in awake patients with sleep-disordered breathing

Continuous positive airway pressure (CPAP) is the main treatment of the obstructive sleep apnoea syndrome (OSAS). We assessed its effects on the upper airway (UA) dynamics in response to bilateral anterior magnetic phrenic nerve stimulation (BAMPS) in 17 awake untreated OSAS patients (15 males; 52 +/- 7 years) whose effective CPAP (P(eff)) had been determined beforehand by a conventional titration sleep study. All twitch-related inspirations were flow-limited, flow first rising to a maximum (V(Imax)), then decreasing to a minimum (V(Imin)), and then increasing again (M-shaped pattern). Up to V(Imin), the relationship between driving pressure (P(d)) and flow (V) could adequately be fitted to a polynomial regression model (V = k(1)P(d) + k(2)P(d)(2); r(2) = 0.71-0.98, P < 0.0001). At atmospheric pressure V(Imax) was 700 +/- 377 ml s(-1), V(Imin) was 458 +/- 306 ml s(-1), k(1) was 154.5 +/- 63.9 ml s(-1) (cmH(2)O)(-1), and k(2) was 10.7 +/- 7.3 ml s(-1) (cmH(2)O)(-1). CPAP significantly increased V(Imax) and V(Imin) (peak values 1007 +/- 332 ml and 837 +/- 264 ml s(-1), respectively) as well as k(1) and k(2) (peak values 300.9 +/- 178.2 ml s(-1) (cmH(2)O)(-1) and 55.2 +/- 65.3 ml s(-1) (cmH(2)O)(-1), respectively). With increasing CPAP, k(1)/k(2) increased up to a peak value before decreasing. We defined as P(eff,stim) the CPAP value corresponding to the highest k(1)/k(2) value. P(eff,stim) was correlated with P(eff) (P(eff) = 7.0 +/- 2.0; P(eff,stim) = 6.4 +/- 2.6 cmH(2)O; r = 0.886; 95 % CI 0.696-0.960, P < 0.001). We conclude that CPAP improves UA dynamics in OSAS and that the therapeutic CPAP to apply can be predicted during wakefulness using BAMPS.

Response of automatic continuous positive airway pressure devices to different sleep breathing patterns: a bench study

Evaluating the usefulness of automatic continuous positive airway pressure (CPAP) in treating the sleep apnea-hypopnea syndrome (SAHS) is not easy because the algorithms for automatic CPAP implemented in the devices available are not well known and are probably dependent on the device. In addition, at present it is not possible to test the behavior of automatic CPAP devices in response to well-defined breathing patterns. Our aim was to implement a bench test to characterize the responses of automatic CPAP devices by subjecting them to breathing patterns of patients with SAHS. To this end, a variety of typical breathing patterns (normal, apneas, hypopneas, flow limitation, snoring) previously recorded in patients with SAHS during sleep were reproduced by a breathing waveform generator. Five commercially available automatic CPAP devices were tested. The responses of the devices to apneas, hypopneas, flow limitation, and snoring were considerably different. In some devices, the response was modified by air leaks similar to the ones found in patients. Consequently, the effectiveness of automatic CPAP assessed in clinical tests performed by using particular devices has no general validity. Testing automatic CPAP devices in a bench study is a useful first step in evaluating the performance of this new type of device in adjusting nasal pressure for each patient.

Memory for symptoms in COPD patients: how accurate are their reports?

The purpose of this study was to examine the accuracy of self-reports of symptom intensity in patients with chronic obstructive pulmonary disease (COPD) and factors that might influence recall of that intensity. Thirty COPD (forced expiratory volume in one second (FEV1) 36 +/- 17% predicted) subjects recorded their dyspnoea and fatigue intensity scores on a 0-10 scale for 14 consecutive days. On the fourteenth day, subjects recalled their average, greatest and least symptom intensity for the previous 14 days. General cognitive function, spirometry, and oxygenation were also measured. No significant differences were found between actual and recalled scores for dyspnoea or fatigue. General cognitive function, measured by the Mini Mental State Exam, correlated with the greatest and least dyspnoea and average fatigue difference scores (recall-actual) and contributed to the variance in the average and least dyspnoea recalled scores. The greatest contributor to the variance in the recall scores of both symptoms was the symptom intensity level on the day of recall. These results highlight the importance of current levels of symptom intensity and cognitive function when appraising symptoms in chronic obstructive pulmonary disease patients.