Compliance with nasal CPAP in obstructive sleep apnea patients

Sleep Medicine Reviews, Vol. 1, No. 1, pp 3344, 1997

SLEEP MEDICINE

REVIEW ARTICLE

Compliance with nasal CPAP in obstructive sleep apnea patients Ph. Collard’, Th. Pieters’, G. Aubert*, D. 0. Rodenstein’

P. Delguste’,

Departments of ‘Pneumology and 2Neurology, Cliniques Avenue Hippocrate 10, B 1200 Brussels, Belgium

Llniversitaires

Saint-Luc,

Continuous positive airway pressure (CPAP) is currently the treatment of choice fey the majority of patients with obstructive sleep apnea (OSA). After a CPAP trial, the ‘initial acceptance rate is 70-80%. Patients who derive no subjective benefit from suck a trial are poor candidates for home treatment with CPAP because they are likely to exkibit lower adherence and compliance rates. About 90% of OSA patients provided with CPAP apparatus will adhere to long-term CPAP treatment. Patients abandoning CPAP do so during the first few months of home therapy, a period during which close monitoring and support is warranted. Because of the strong correlation between the machine run time and effective pressure delivered at the nasal mask (90-95%), the time-counter of the CPAP device is sufficient to monitor compliance in clinical practice, allowing for early intervention in cases of suboptimal use. Longterm acceptors of CPAP display a satisfactory compliance (5-6.5 k of average daily use) which compares favourably with compliance with treatment in other chronic diseases. Lower acceptance and compliance rates have been reported in North America as compared to Europe. This could be related to cultural differences or different routines of prescription and follow-up.

Key words: Obstructive sleep apnea, continuous positive airway pressure, compliance

Nasal continuous positive airway pressure (CPAP) is generally considered as the best treatment for all but the mildest forms of obstructive sleep apnea (OSA).l Provided that the appropriate pressure can be applied, it is always effective in eliminating OSA. As it is a self-administered treatment, its efficacy is critically dependent on the patient’s willingness to use the device and apply the nasal mask during sleep. Hence, compliance should be regarded as the main determinant for success of CPAP. Cure of OSA is rare and the majority of patients are therefore committed to a lifelong treatment with CPAP. On the one hand, most patients notice a clear improvement in their daily life with CPAP and rapid recurrence of symptoms after withdrawal. On the other hand, it is a demanding treatment and not all patients are prepared to accept both its constraints and its possible side effects over several years. Compliance with CPAP will result from the balance between perceived benefits and drawbacks of treatment. In a study of compliance based on objective patterns of use in newly diagnosed OSA, it was found that patients may actually be wearing the mask much less than prescribed and reported subjectively.’ As a consequence, it was assumed that CPAP 1087-0792/97/010033+12$12.00/0

0 1997 W.B. Saunders Company Ltd

34

Ph. Collard et aZ.

may fall short of its therapeutic goal and the American Thoracic Society has recently ssued a rather pessimistic statement indicating that overall compliance rates may actually approach 50% at best1 In the present paper, we will review the issue of acceptance and compliance with CPAP at 3 levels: 1. Primary acceptance, i.e. the proportion of OSA patients accepting a CPAP trial with titration of pressure and willing to embark on such a treatment at home. 2. Adherence (or secondary acceptance), i.e. the proportion of patients who pursue CPAP treatment long-term after having been provided with an apparatus for home treatment. 3. Compliance, defined as the rate at which patients who adhere to their treatment actually use it.

Primary

acceptance

of CPAP as a home

treatment

After a single night spent at effective pressure, many patients are convinced of the efficacy of CPAP because they perceive a clear improvement in sleep quality and daytime status. In those patients who had the opportunity to get acquainted with the apparatus and had the pressure titrated in the sleep laboratory, prescription rates for home treatment of the order of 70-80% are usually reported.3-7 The initiation period is probably critical for eventual acceptance and possibly also for long-term compliance. In this context, the methods of implementing CPAP appear as important, including education of patients as to the principles and goals of therapy, acclimatization period, and interventions to cope with anxiety and side effects.

Adherence

or CPAP treatment

interruptions

Most patients who will give up CPAP therapy do so within the first few months. For instance, Rolfe et a2. have reported that 78% of treatment interruptions took place within 2 months and 90% within 4 months of prescription.* In a larger study, Krieger et al. found that about 40% of secondary drop-outs occurred within 3 months and 80% within 1 year.’ The proportion of OSA patients abandoning CPAP use after initial acceptance ranges from 5 to 37%. In general, fewer treatment interruptions have been reported in Europe (5-19yo)5-7, 9x12 than in North America and Australia (19-37%).3,8,“,‘3,‘4 This might be related to cultural differences, and to different procedures of follow-up and support. When the drop-outs related to death or cure of OSA are excluded, we are left with about 10% of patients with QSA abandoning their CPAP treatment.5-7,10*12In the largest series published so far, more than 90% of the patients were still using CPAP after 3 years of treatment and more than 85% after 7 years.’ The first few weeks or months of home therapy appear to be the most critical phase for adjusting to CPAP and securing long-term compliance.

CPAP compliance

Determinants

of primary

acceptance

35

in OSA

and adherence

The literature is contradictory with various determinants of CPAP acceptance and use found in some studies but not in others. A number of studies have found some correlation between primary acceptance of and/or adherence to CPAP, and either objective measures of OSA severity4f6 or the subjective degree of sleepiness.>‘” More beneficial changes of CPAP were perceived by patients pursuing CI’AP and, interestingly, by their family also.ll In one study, up to 50% of patients with mild OSA (AH1 less than 30) refused to undergo a CPAP trial altogether4 The pressure was not higher” and the physical side effects were not more common3’11 among the patients who returned their CPAP machine. Patients with milder OSA and their spouses complained more about noise fron the machine.l’ About 25% of the patients abandoning CPAP declared that they did so because they had experienced no subjective benefits from this treatment.8”0,11 There is evidence that CPAP adherence3 and compliance’5 were adversely affected by previous palatal surgery. This has been attributed to mouth air leak. Early denials were mainly related to one or more of the following factors: anxiety, claustrophobia, inconvenience of being connected to a machine, noise, discomfort caused by the mask, difficulties of falling asleep, intolerance to high expiratory pressure, frequent nocturnal awakenings, lack of symptomatic benefit and general dislike of the system.8,10,13 Where GAP is not provided as a medical insurance or social security benefit, cost was considered as a problem by 28% of the patients,’ and it was the main reason for discontinuing treatment in 10% of non-adherent patients.’

Definition

of compliance

and methods

of monitoring

compliance

There is a lack of standard definition of compliance with CPAP use in the literature. Comparisons between studies are difficult because of different criteria set for compliance, different patient populations (new CPAP users versus long-term acceptors), variable modalities of data collection and unequal follow-up durations. Three modes of evaluation of compliance have been used: 1. Subjective compliance, as determined from self-reports by the patients. 2. Objective compliance, established from the built-in time-counter of the CPAP device, which measures the cumulative time that the apparatus is turned on (“machine run time”). However, there is a concern that the running time of the machine might be significantly different from the actual therapeutic mask pressure delivery. Furthermore, the run-time clock provides an average figure of use between two readings but no information on the pattern of use during each 24-h period. 3. Effective compliance, established from an additional microprocessor recording both machine run-time and time spent at effective pressure (“time at pressure”). This pressure monitor is activated when the mask pressure is more than a predetermined pressure (usually 2 cmH,O below the pressure at which the CPAP machine is set). A precise diary of effective use can be established. Without knowing actual sleep time (which may vary considerably between patients), studies of mask pressure may still not provide fully accurate data on true effective compliance.

Ph. Collard et al.

36 Table 1 Short-term CPAP users

effective

compliance

with CPAP in prospective

studies of new

Authors (reference, year of publication)

Patients

Follow-up

Objective compliance (time counter)

Gibbs ef al. (Ref. 2, 1993) Reeves-Hoche et al. (Ref. 13, 1994) Engleman et al. (Ref. l&1994)

35

3 months

3.2 h/day

Effective compliance (pressure monitor) 2.9 h/day

38

6 months

4.7 h/day

4.3 h/day

32

1-3 months

4.7 h/day

4.2 h/day

Subjective

compliance

In early studies, compliance was judged on the basis of patient reports. The data were acquired by either written questionnaires or phone calls, and compliance was reported as the proportion of patients who allegedly applied CPAP at least an arbitrary number of days per week and/or number of hours per night. Early studies based on patient report suggested very good comp1iance.l” However, this was not confirmed by objective recordings. From the comparison between self-reported and time-counter data, it is now clear that patients overestimate their CPAP use by about 1 h per night on average.2~9~‘0~‘2~17 Individual patient reports may deviate quite substantially from real use so that self-reports should be considered as unreliable for assessing compliance.

Objective

and effective

compliance

in new CPAP users

A few prospective studies based on both time and pressure monitors have been performed in patients during their first few weeks or months of home therapy (Table 1). The effective pressure was applied during mean durations of 3.24.3 h per night, corresponding to 3.54.7 h of machine run time.2,‘3,‘8 These rates of use may appear as very disappointing in comparison with a sleep time of about 8 h per night. However, it is clear that there are major differences in CPAP use between the first few weeks and the following years of home therapy.l’ A study carried out during the first few months of treatment will contain a fraction of patients who will prove unable to adapt to CPAP, making the rest of the group appear less compliant. This adaptation period probably accounts for the discrepancy of compliance with CPAP between new and long-term users (see below). In new CPAP users, prospectively studied during their first 3 months of home therapy, 46% of the patients were considered as regular users (defined by at least 4 h of effective CPAP on 70% of the days) in a study from the United States,’ whereas 75% of patients met these criteria in a European collaborative study (Pepin JL, unpublished). The difference results probably from different forms of service delivery and of follow-up policies after prescription. The introduction of an external pressure monitor does not by itself induce a modification of the patients’ behavior (PGpin JL, unpublished).

CPAP

Table 2

* mentioned

Long-term

only

objective

if r>.0.2/

t including

compliance in OSA

compliance

patients

with CPAP in cross-sectional

with

only

4 months

studies

of treatment

From simultaneous studies of machine time-counter and mask pressure monitor recordings, it is now clear that appropriate application of pressure occurs between 89 and 97% of the time the power is on (‘86,I38~1I91*O;Pepin JL, unpublished). This small discrepancy between time-counter and pressure monitor can be explained by one or several of the following factors: (1) the mask is not correctly fitted, causing significant leaks; (2) the patient is using the delay timer which allows progressive ramp up of pressure so that effective CPAP at the mask is not reached until 30 minutes or so after the machine has been switched on; (3) the machine is in operation but the mask is not worn by the patient (for instance, a number of patients may be using the blower for drying the tubes after washing). There was a very high correlation between values of machine run time and time at pressure in individual CPAP users.‘* These data support the contention that, for clinical purposes, the time counter is all that is needed to adequately monitor CPAP use in the majority of patients.

Objective

compliance

in long-term

CPAP users

Objective compliance in long-term CPAP acceptors has been reported in several crosssectional (and sometimes longitudinal) studies. Table 2 summarizes a.number of such studies in which compliance was established from the time counters in at least 40 patients followed up for longer than 1 year.5, 6*7,9*lo,‘*, 17,”

Ph. Collard

38

et aE.

In long-term acceptors of CPAP, the mean daily use was 5-6.5 h (approximately 2h more than in the more heterogeneous group of new CPAP users, which includes poorly motivated patients). More than 85% of the long-term users had an average use of at least 3 h.5-7,9 Only 1% of the long-term users admitted to no subjective benefit derived from their therapy,” while 25% of OSA patients abandoning CPAP mentioned the lack of benefit as the major reason to return the machine.8,10,11 In these long-term studies, the rate of use did not fall with time.7,9 Krieger et al. have even found that patients increased their rate of use over the first 2 years of home therapy.6 While there was a great interindividual dispersion of hourly use, the intraindividual variation appeared much lower.7 Using pressure monitors, Fleury et al.19 have provided additional information on the pattern of CPAP use in a representative group of long-term acceptors studied prospectively. Their average daily rate of use was 7.1 h. The CPAP system was used for 94% of the monitored days and 60% of patients used the device every day over the l-month follow-up period. The main reasons for not using the device are self-prescribed treatment breaks (e.g. naps, weekends, holidays, travel, hospitalization) or transitory CPAP withdrawal during episodes of nasal blockage, not to mention occasional mask or device failure. Some patients may find the apparatus uncomfortable and remove it during the night. In particular, about lo-20% of the patients who wake up during the night do not reestablish CPAP and spend the rest of the night without CPAP for an average duration of 1.42 h.*,13 In one study, the reasons for not using the device included (in decreasing order): nasal obstruction (34%), travel (28%), tired of device (23%), mask failure (20%), device failure (12%), partner disturbed (7%).14 Most patients do not consider the side effects sufficiently bothersome to limit their compliance with CPAl?

Determinants

of compliance

In prospective studies dealing with new CPAP users, there was a tendency for an association between higher effective use and more severe OSA or more complaints of excessive daytime sleepiness at diagnosis.2,‘3 However, baseline multiple sleep latency test (MSLT) did not appear to predict CPAP compliance.‘,l’ In long-term studies, the most consistent correlation of daily use of CPAP was with objective measures of OSA severity at diagnosis, such as the AHI, the movement arousal index (reflecting sleep fragmentation) or oxygen saturation during sleep (see Table 2). In most studies, MSLT or score of sleepiness at diagnosis were not significantly correlated with subsequent use of CPAI? The combination of factors contributing to the variance of the rate of use explained less than 10% of the variance. This suggests that long-term compliance is multifactorial or affected by factors which are not entered in the statistical analysis, such as subjective benefit (which could be established from a visual analogue score), or help and support by the prescribing team and family. Patients with low compliance did not have higher pressure.‘,17 In two studies, it was even lower.6,1s The less compliant patients did not report more physical side effects of CPAP>12 but they complained more about bulkiness of the machine.’

CPAP compliance

in OSA

39

It has been suggested that attended home titration of pressure** or titration during a split night in the sleep laboratoryz3 did not result in lower compliance than conventional titration at full-night polysomnography. As the level of compliance one could expect from an individual cannot be reliably determined before instituting CPAP therapy, an objective evaluation of compliance should be regularly obtained for all patients. A particular attention should be paid to those with milder OSA and those who reported less subjective benefit during a CPAP trial.

Why

don’t

OSA patients

use CPAP every

time

they

sleep?

From the studies reviewed so far, it is clear that many OSA patients do not apply CPAP every time they sleep. Almost all patients using CPAP for more than 3 h declared themselves satisfied with the subjective improvement. 24 We have also encountered patients using their CPAP device during several years for even shorter durations on average, but who were satisfied with the treatment and did not want to quit CPAP. They seem to derive enough subjective benefit from what would appear as very bad compliance. The patient’s main motivation to sleep with a mask over the nose for the rest of his life appears to be the impact daytime sleepiness has on his quality of life. One reason for not using CPAP all night long or every night could be that overt daytime somnolence does not recur immediately with intermittent use. Patients learn from experience that they can maintain satisfactory performance levels despite reduction in CPAP use. To some extent, they may be titrating their use to eliminate symptoms of daytime sleepiness. This is supported by the fact that sleepiness diminished to a similar extent in high and low users of CPAP.17 A residual, “hang-over” effect of CPAP has been demonstrated in several studies. When CPAP was applied during the first 4 h of the night, there was partial improvement of OSA during unassisted breathing for the rest of the night, both in new25 and in established CPAP users.26 Such an improvement has also been shown after CPAP withdrawal during one27 or several nights (Ph. Collard, unpublished). The possible mechanisms accountable for this hang-over effect are improvement in upper airway morphology and collapsibility, correction of sleep fragmentation and changes in ventilatory control. This probably explains why there was a small decrease (about 2 cmH,O) in the level of pressure required to abolish upper airway obstruction after a few weeks of CPAP treatment, as compared to the pressure determined at initial titration.” However, despite the fact that the rate of respiratory events was lessened, withdrawal of CPAP use for even a single night resulted in the reappearance of short sleep latencies by MSLT.29

The consequences

of not using

CPAP and how

much

is enough?

The pathophysiological consequences of such an intermittent use are by no means clear. On a short-term basis, cognitive performance, daytime sleepiness (supported by MSLT), mood and quality of life all improved even at a low level of CPAP use (effective

40

Ph. Collard

et al.

compliance of 3.4 h)20 However, the improvement in sleep latency with CPAP was relatively small, suggesting that the beneficial effects may only be partial. Increased CPAP use was associated with greater improvements in symptom scores, quality of life and concentration2’ This raises the question of how much is necessary for CPA!? to be effective. There is no study establishing a threshold rate of use of CPAP below which there is no benefit. At this stage, all criteria for CPAP usage and compliance are essentially aribitrary and it may be unjustified to set a lower limit of compliance. Unlike in longterm oxygen therapy for instance, we do not have detailed “dosage studies” with CPAP from which a threshold use for improving long-term outcome or a dose-effect relationship can be determined. We have some information with regard to a few long-term outcomes. In the study by He et al.?’ CPAP was as effective as tracheostomy (which is by definition 100% effective at correcting OSA) to prevent the excess of mortality associated with OSA. Compliance with CPAP was not mentioned but there is no reason to believe that it was better than in the long-term studies mentioned above. In a group of patients with an average 5.1 h of CPAP use, there was a significant reduction of road traffic incidents.” In view of the less than optimal correction of nocturnal and diurnal consequences of OSA with intermittent use of CPAP, there is no doubt that patients with OSA should repeatedly be encouraged to use CPAP whenever they sleep.

How can we improve

acceptance

and compliance?

The time counter permits recognition of low rates of use. In such instances, early intervention is probably a factor of improved CPAP adherence and use. Clearly, it is important to identify the cause of CPAP failure which may vary from one patient to the next. A study in a small group of patients has suggested that positive reinforcement by telephone and the intensity of follow-up do not influence compliance.31 In another study, intervention to urge patients to be as compliant as possible resulted in increased usage.2 Although it is not fully demonstrated that close follow-up can improve compliance, clinical experience suggests that the strategy of follow-up is very important to secure high levels of compliance. A number of OSA patients find it difficult to exhale against CPAI? In such patients, the preset pressure may produce arousals from sleep. By using a device that permits independent adjustment of lower expiratory and higher inspiratory pressures, adverse effects associated with high levels of CPAP could theoretically be reduced. In a study comparing CPAP and BIPAP (bilevel positive airway pressure), there was no difference in the rate of use between the two devices nor in the proportion of the night spent at effective pressure. However, the drop-out rate was somewhat lower in the BIPAP users.32 Rauscher has sy stematically tried BIPAP in patients who did not tolerate CPAP on the pressure titration night, a group representing 11% of OSA patients considered for CPAP therapy. The majority of patients unable to tolerate CPAP refused BIPAP also (Rauscher H, unpublished).“Intelligent CPAP” (also called auto-CPAP) devices with diagnostic and therapeutic abilities could improve comfort and compliance. These devices can detect respiratory events and can generate a variable CPAP level throughout sleep in order to prevent upper airway obstruction. Such devices may actually deliver a wide range of pressures on a single night depending on nasal obstruction, sleep

CPAP compliance

in OSA

41

stages, alcohol and/or sedative intake, and body position, for instance. As these devices deliver variable “as needed” pressure, the mean overnight pressure level should theoretically be less than with conventional constant CPAP. In a group of OSA patients already treated with conventional CPAP, auto-CPAP was associated with better comfort (Meurice JC, unpublished). Such an auto-CPAP system was also compared to CPAP in two small parallel groups of patients. Both treatments were equally effective at correcting OSA and improving daytime vigilance. In the auto-CPAP group, the mean mask pressure was not lower than the pressure titrated at polysomnography. We understand that the mean pressure was even higher during light sleep and this could possibly hamper sleep onset. Over a period of 3 weeks, the home amount of use was significantly higher in the auto-CPAP group (7.1 h) than in the constant-CPAP group (5.7 h).33 The potential advantages of auto-CPAP should be corroborated in larger groups of OSA patients who do not tolerate CPAP before its prescription can be advocated in such patients. As the level of pressure is not a determinant of CPAP compliance, it is doubtful that changes in the way pressure is delivered (BIPAP or auto-CPAP) will have a huge impact on compliance with therapy in the majority of OSA patients. Furthermore, in those patients who do not tolerate the optimal CPAP level, conventional CPAP treatment can be started at a somewhat lower pressure (for instance 2 cmH,O below the ideal pressure). Under such conditions, the patients derive immediate benefit from CPAP and further improve over time (the remaining respiratory events usually disappear after 2 months of CPAP use).‘”

Alternative

treatments

for non-compliant

patients

Other forms of treatment may be more appropriate for patients with OSA who do not tolerate CPAP or demonstrate low levels of use. A comprehensive evaluation of alternative treatments is beyond the scope of this review. They will be only briefly mentioned with emphasis on compliance. About half of the patients who refuse or abandon CPAP sought no further treatment, while the remainder received alternative treatments such as weight loss, position training, or uvulopalatopharyngoplasty, with variable results.3*6*34Weight loss can bring about cure of OSA in obese patients but compliance with dietetic counselling is limited and consistent slimming is rare. Gastroplasty can be considered in morbidly obese patients with OSA but it is associated with significant drawbacks. In a randomized crossover study, patients with mild to moderate OSA were subjectively more satisfied (and reported less side effects) with an oral appliance than with CPAP, despite the fact that CPAP was objectively more effective at correcting snoring, OSA and excessive daytime sleepiness.35 The long-term compliance with oral appliances (and their impact on outcome) will have to be studied with the same scrutiny as for CPAP, before they can be advocated as valuable alternatives. The objective long-term compliance with such devices could for instance be evaluated with microchips recording temperature changes. Maxillo-mandibular advancement osteotomy and hyoid suspension can also be offered as a surgical alternative. The advantages of such a surgical procedure are that compliance is not an issue and that cure can be contemplated in an as yet undetermined proportion of patients. The disadvantages are that a therapeutic trial is not possible, that the results are variable and that there is a significant complication rate. Few

42

Ph. Collard

et al.

centers have consistently reported very beneficial which is not widely available as present.

Comparison

with

other

results with this treatment

option

diseases

In our opinion, obtaining such a high level of adherence and compliance in a chronic disease such as OSA with a prolonged and constraining treatment like CPAP is a very satisfactory result which compares favorably with other therapeutic situations. Wearing a mask and being connected to a machine during sleep is certainly more constraining than swallowing a few pills. In general, at least 50% of patients on longterm treatment do not use medication as prescribed. For instance, patients with epilepsy may take their medication as prescribed on only 39% of the days, despite the potential for socially unacceptable and medically dangerous consequences.36 Similar results have been reported in common diseases such as asthma and systemic hypertension.37,38 Compliance can also be compared with long-term oxygen therapy, another form of lifelong home treatment with a machine (oxyconcentrator or liquid oxygen system). Long-term domiciliary oxygen therapy has been demonstrated to improve survival in patients with chronic obstructive pulmonary disease provided that it is given for at least 15 h a day. In a group of a thousand patients, only 45% used oxygen for at least 15 h per day on average.39 It is clear that both the method of initial advice, and subsequent technical and medical follow-up are important factors contributing to acceptable compliance.

Conclusions CPAP is currently the most widely prescribed treatment for obstructive sleep apnea. However, it may be difficult to use and there have been reservations concerning its acceptability and its actual use by patients that might restrict its beneficial effects. The lack of subjective benefit from CPAP appears to be a major factor having detrimental influences on adherence and compliance. Patients with more severe OSA are expected to derive more benefit from CPAP and this does probably account for the association (albeit weak) between indices of OSA severity and both CPAP acceptance and use. The majority of long-term acceptors apply nasal CPAP faithfully during most of their nocturnal sleep, but some patients seem to restrict their use just to the rate bringing about subjective relief of excessive daytime sleepiness. High rates of acceptance and adherence have been secured in programs where enough time is spent on education and support. Clinical experience suggests that a continued relationship between the patient and the prescribing team is important. Under such conditions, the majority of patients achieve acceptable levels of long-term compliance with CPAP, which compares favourably with compliance in other chronic diseases.

References 1 American Thoracic Society. Indications and standards for use of nasal continuous positive airway pressure (CPAP) in sleep apnea syndromes. Am J Respir Cvit Care Med 1994; 150: 1738-1745.

CPAP compliance

in OSA

43

2 Kribbs NB, Pack AI, Kline LR et al. Objective measurement of patterns of nasal CPAP use by patients with obstructive sleep apnea. Am Rev Respiv Dis 1993; 147: 887-895. 3 Waldhorn RE, Herrick TW, Nguyen MC et al. Long-term compliance with nasal continuous positive airway pressure therapy of obstructive sleep apnea. Chest 1990; 97: 33-38. 4 Rauscher H, Popp W, Wanke T et al. Acceptance of CPAP therapy for sleep apnea. Chest 1991; 100: 1019-1023. 5 Chollet S, Ordronneau J, Chailleux E et al. Facteurs predictifs de l’observance de la pression positive continue nocturne chez les patients porteurs d’un syndrome d’apnees du sommeil. Rev Ma1 Resp 1993; 10: 519-525. 6 Krieger J, Kurtz D, Petiau C et al. Long-term compliance with CPAP therapy in obstructive sleep apnea patients and in snorers. Sleep 1996; 19: 5136-5143. 7 Pieters T, Collard P, Aubert G et al. Acceptance and long-term compliance with nCPAP in patients with obstructive sleep apnoea syndrome. Euu Respiv J 1996; 9: 939-944. 8 Rolfe I, Olson LG, Sanders NA. Long-term acceptance of continuous positive airway pressure in obstructive sleep apnea. Am Rev Respiv Dis 1991; 144: 1130-1133. 9 Meurice JC, Dore P, Paquereau J et al. Predictive factors of long-term compliance with nasal continuous positive airway pressure treatment in sleep apnea syndrome. Chest 1994; 105: 429433.

10 Engleman HM, Asgari-Jirhandeh N, McLeod AL et al. Self-reported use of CPAP and benefits of CPAP therapy. A patient survey. Chest 1996; 109: 1470-1476. 11 Hoffstein V, Viner S, Mateika S et al. Treatment of obstructive sleep apnea with nasal continuous positive airway pressure. Patient compliance, perception of benefits, and side effects. Am Rev Respiv Dis 1992; 145: 841-845. 12 Pepin JL, Leger P, Veale D et al. Side effects of nasal continuous positive airway pressure in sleep apnea syndrome. Study of 193 patients in two French sleep centers. Chest 1995; 107: 375-831. 13 Reeves-Hoche MK, Meek R, Zwillich CW. Nasal CPAP: an objective evaluation of patient compliance. Am J Respir Crit Cave Med 1994; 149: 149-154. 14 Nino-Murcia G, Crowke McCann C, Bliwise DL et al. Compliance and side effects in sleep apnea patients treated with nasal continuous positive airway pressure. West 1 Med 1989; 150: 165-169. 15 Mortimore IL, Bradley PA, Murray JAM et al. Uvulopalatopharyngoplasty may compromise nasal CPAP therapy in sleep apnea syndrome. Am J Respiv Cvit Cave Med 1996; 154: 1759-1762. 16 Sanders MH, Gruendl CA, Rogers RM. Patient compliance with nasal CPAP therapy for sleep apnea. Chest 1986; 90: 330-333. 17 Rauscher H, Formanek D, Popp W et al. Self-reported vs measured compliance with nasal CPAP for obstructive sleep apnea. Chest .1993; 103: 1675-1680. 18 Engleman HM, Martin SE, Douglas NJ. Compliance with CPAP therapy in patients with the sleep apnoea/hypopnoea syndrome. Tkovax 1994; 49: 263-266. 19 Fleury B, Rakotonanahary D, Hausser-Hauw C et al. Objective patient compliance in longterm use of nCPAl? Eur Respir J 1996; 9: 2356-2359. 20 Engleman HM, Martin SE, Deary IJ et al. Effect of continuous airway pressure treatment on daytime function in sleep apneoa/hypopnoea syndrome. Lancet 1994; 343: 572-575. 21 Noseda A, Kempenaers C, Kerkhofs M et al. Sleep apnea after 1 year domiciliary nasalcontinuous positive airway pressure and attempted weight reduction. Potential for weaning from continuous positive airway pressure. Chest 1996; 109: 138-143. 22 Waldhorn RE, Wood K. Attended home titration of nasal continuous positive airway pressure therapy for obstructive sleep apnea. Chest 1993; 104: 1707-1710. 23 Fleury B, Rakotonanahary D, Tehindrazanarivelo AD et al. Long-term compliance to continuous positive airway pressure therapy (nCPAP) set up during a split-night polysomnography. Sleep 1994; 17: 512-515. 24 Krieger J, Kurtz D. Objective measurement of compliance with nasal CPAP treatment for obstructive sleep apnoea syndrome. Eur Respir 1 1988; 1: 436438. 25 Hers V, Liistro G, Dury M et al. Residual effect of nCPAP applied for part of the night in patients with obstructive sleep apnoea. Eur Respiv J 1997; 10: 973-976. 26 Rauscher H, Popp W, Wanke T et al. Breathing during sleep in patients treated for obstructive sleep apnea. Nasal CPAP for only part of the night. Chest 1991; 100: 156-159. 27 Collop NA, Block AJ, Hellard D. The effect of nightly nasal CPAP treatment on underlying obstructive sleep apnea and pharyngeal size. Chest 1991; 99: 855-860.

44

Ph. Collard

et al.

28 Series F, Marc I, Cormier Y et al. Required levels of nasal continuous positive airway pressure during treatment of obstructive sleep apnoea. Eur Respiv 1 1994; 7: 1776-1781. 29 Kribbs NB, Pack AI, Kline LR et al. Effects of one night without nasal CPAP treatment on sleep and sleepiness in patients with obstructive sleep apnea. Am Rev Respir Dis 1993; 147: 1162-1168. 30 He J, Kryger MH, Zorick FJ et al. Mortality and apnea index in obstructive sleep apnea. Chest 1988; 94: 9-14. 31 Fletcher EC, Luckett RA. The effect of positive reinforcement on hourly compliance in nasal continuous positive airway pressure users with obstructive sleep apnea. Am Rev Respir Dis 1991; 143: 936-941. 32 Reeves-Hoche MK, Hudgel DW, Meek R et al. Continuous versus bilevel positive airway pressure for obstructive sleep apnea. Am J Respir Cvit Care Med 1995; 151: 443449. 33 Meurice JC, Marc I, Series F. Efficacy of auto-CPAP in the treatment of obstructive sleep apnea/hypopnea syndrome. Am J Respir Cvit Cave Med 1996; 153: 794-798. 34 Krieger J. Long-term compliance with nasal continuous positive airway pressure (CPAP) in obstructive sleep apnea patients and nonapneic snorers. Sleep 1992; 15: S42-S46. 35 Ferguson KA, Onu T, Lowe AA et al. A randomized crossover study of an oral appliance vs nasal-continuous positive airway pressure in the treatment of mild-moderate obstructive sleep apnea. Chest 1996; 109: 1269-1275. 36 Cramer JA, Mattson RH, Prevery ML et al. How often is medication taken as prescribed? A novel assessment technique. JAMA 1989; 261: 3273-3277. 37 Mawhinney H, Spector SL, Kinsman RA et al. Compliance in clinical trails of two nonbronchodilator, antiasthma medications. Ann Allergy 1991; 66: 294-299. 38 Rudd I? Clinicians and patients with hypertension: unsettled issues about compliance. Am Heart J 1995; 130: 572-579. 39 Barjhoux C, Pepin JL, Deschaux-Blanc C et al. Oxygenotherapie au long tours a domicile: respect de la prescription medicale et observance d’une duree quotidienne d’au moins 15 heures. Rev Ma1 Respir 1994; 11: 3745.