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* From the Departments of Pulmonary Medicine (Drs. Sin, Mayers, and Man) and Psychiatry (Dr. Pawluk), University of Alberta, Edmonton, AB, Canada.
Correspondence to: Don D. Sin, MD, 2E4.29 Walter C. Mackenzie Center, University of Alberta, Edmonton, AB, Canada, T6G 2B7; e-mail: don.sin{at}ualberta.ca
| Abstract |
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Design: Prospective cohort longitudinal study.
Setting: University sleep disorders center.
Patients: Two hundred ninety-six
patients with an apnea-hypopnea index (AHI)
20/h on
polysomnography.
Interventions: A CPAP device equipped with a monitoring chip was supplied. Within the first week, daily telephone contacts were made. Patients were seen at 2 weeks, 4 weeks, 3 months, and 6 months.
Results: Of the 296 subjects
enrolled, 81.1% were males. Mean ± SD AHI was 64.4 ± 34.2/h of
sleep; age, 51 ± 11.7 years; and body mass index, 35.2 ± 7.9
kg/m2. The mean duration of CPAP use was 5.7 h/d at 2
weeks, 5.7 h/d at 4 weeks, 5.9 h/d at 3 months, and 5.8 h/d at 6
months. The percentage of patients using CPAP
3.5 h/d was 89.0% at
2 weeks, 86.6% at 4 weeks, 88.6% at 3 months, and 88.5% at 6 months.
There was a decrease in the Epworth Sleepiness Scale (ESS) score of
44% by 2 weeks of therapy. The patients continue to improve over the
follow-up period, with the lowest mean ESS score observed at 6 months.
With multiple regression analysis, three variables were found to be
significantly correlated with increased CPAP use: female gender,
increasing age, and reduction in ESS score.
Conclusion: A population-based CPAP program consisting of consistent follow-up, "troubleshooting," and regular feedback to both patients and physicians can achieve CPAP compliance rates of > 85% over 6 months.
Key Words: compliance rate continuous positive airway pressure obstructive sleep apnea
| Introduction |
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Continuous positive airway pressure (CPAP) is an effective therapy for OSA, significantly reducing OSA symptoms in a vast majority of cases.4 Successful application of CPAP can dramatically improve the health-related quality of life of patients and transform somnolent individuals into energetic and more productive people.5 Moreover, the use of CPAP can decrease systemic BP and improve cardiovascular performance, thereby decreasing cardiovascular morbidity and mortality associated with OSA.5
However, CPAP therapy is often difficult to tolerate and patients frequently stop using it because of discomfort. The nasal mask interface may cause pressure sores, persistent air leakage, claustrophobia, nasal congestion, and other side effects that may lead to suboptimal compliance.6 One study7 suggests that CPAP compliance might be improved with intensive CPAP support, where these problems can be addressed through a multidisciplinary team approach. However, as these results were produced in a clinical trial setting, it remains uncertain whether high CPAP compliance rates can also be achieved in the community using a similar CPAP program.
Using data from a comprehensive CPAP program implemented in Northern Alberta (population 1.3 million persons) beginning in July of 1999, the aims of this study were to determine: (1) short-term and long-term CPAP compliance rates in the community, (2) baseline predictors for long-term CPAP compliance, and (3) whether CPAP use is associated with sustained improvements in daytime sleepiness in OSA patients with moderate-to-severe disease.
| Materials and Methods |
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Recruitment and Consent
Between July 1999 and March 2000, all patients undergoing
diagnostic polysomnography at the UAH Sleep Disorders Laboratory were
considered as potential recruits for this study. All patients were
referred for clinical evaluation of possible sleep disorders.
Patients with an AHI
20/h were considered to be eligible candidates
to receive a CPAP device provided by Alberta Aids to Daily Living
without any cost to the patient. Some subjects with an AHI < 20/h
also received CPAP therapy if there were significant clinical
indications for CPAP therapy. All patients receiving CPAP devices were
asked to sign a consent form indicating their willingness to comply
with CPAP therapy, and their explicit understanding that the CPAP
device must be returned if their compliance was deemed unsatisfactory,
as measured through a pressure-sensing chip included in each CPAP unit.
Polysomnography
The diagnostic polysomnographic studies were performed at the
UAH Sleep Disorders Laboratory. Recordings were performed overnight
with continuous monitoring of EEG, electro-oculogram, chin
electromyogram, oronasal airflow (by thermistor), chest and abdominal
respiratory movements, oximetry, anterior tibialis electromyogram, body
position sensor, and snoring noise sensor. Digitized signals were
stored on optical disk and analyzed using software (Sandman Elite
Version 5.0; Nellcor Puritan Bennett [Melville] Ltd., Ottawa, ON,
Canada). Manual scoring was done by trained, certified technologist to
verify the automated scoring system in every case. All sleep recordings
were verified by American Board of Sleep Medicine-certified sleep
specialists who provided descriptive diagnostic interpretation of the
polysomnographic studies.
Scoring of sleep staging was done using published criteria.8 An apnea episode was defined as a cessation of oronasal airflow for > 10 s. An hypopnea episode was defined as a diminution of the amplitude of respiratory signals by > 50% for > 10 s, with or without desaturation. An obstructive respiratory event was scored when there was evidence of paradoxical chest and abdomen movement. A central respiratory event was scored when both the chest and abdominal respiratory movements were diminished.
Follow-up Protocol
All CPAP subjects underwent an educational session prior to
commencement of CPAP therapy, which included a 26-min video
presentation (produced locally by the Sleep Apnea Society of Alberta)
and a one-on-one discussion session with a qualified CPAP clinic nurse.
The videotape presented information on OSA, including symptoms, health
consequences, and pathophysiology, and a detailed explanation on the
use of the CPAP device. The key concepts from this videotape was
subsequently reinforced by a CPAP nurse who had prior training and
experience in polysomnographic studies and in basic respiratory therapy
principles relevant to the care of the CPAP devices. Reading materials
were given to each subject, with a pamphlet on OSA, CPAP devices,
suggestions for troubleshooting and remedies, as well as a follow-up
schedule.
Subjects were instructed to contact the CPAP clinic nurse daily by telephone within the first week. Subsequently, the subjects were seen at 2 weeks, 4 weeks, 3 months, and 6 months after starting CPAP therapy. At each visit, the compliance data were downloaded from the CPAP device and reviewed by the CPAP clinic nurse together with the subjects. Any concerns or questions were addressed immediately by the CPAP clinic nurse, and changes in the CPAP setting, nose/face mask, or circuit were made after consultation with the responsible sleep physician if necessary. If nasal complaints were significant, either topical steroid spray or anticholinergic nasal spray was prescribed. If these failed, a heated humidifier was then made available. During the study period, only 15 patients required a heated humidifier. Each follow-up visit lasted 15 to 30 min.
The compliance data from each visit were tabulated and reported to the referring sleep physician. If there were doubts about a patients compliance or willingness to continue with the program, the referring physician made personal contacts with the patient by telephone or through direct in-person interviews to resolve barriers to adequate compliance. Through a collaborative team effort, patient problems were addressed and resolved.
CPAP Device
The CPAP device used was the Aria LX model (Respironics;
Pittsburgh, PA). There were various nose masks, face masks, nasal
pillows, and head-harnesses used, depending on individual facial
structure and preference. Passive humidifiers were routinely used.
Heated humidifiers were used when necessary. In all CPAP devices, there
was a built-in monitoring chip for collection and storage of CPAP usage
data. The monitoring chip only registers use when the set pressure was
maintained, not just when the CPAP device was turned on. The monitoring
device provided time of days used, hours of daily use, and days used
per month. From these data, we calculated: Percentage of days CPAP
was used
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Measurements
At the start of the CPAP program, and during each follow-up
visit, subjects were asked to complete a questionnaire regarding the
degree of daytime sleepiness (the Epworth Sleepiness Scale
[ESS]).9
Statistical Analysis
The means and SDs of continuous variables were compared using
Students two-tailed t test. Nonnormally distributed
variables were compared using the Wilcoxon rank-sum test. Ordinal and
binary variables were compared using a
2 test.
A trend test was used to determine significance of temporal
relationships in the use of CPAP over the 6 months of follow-up. To
determine important predictors of 6-month compliance to CPAP, we used a
multiple logistic regression model. We employed a step-wise regression
model to select out significant variables; only those variables that
produced a p value < 0.05 were included in the final model. Odds
ratios are presented with 95% confidence intervals, and reported p
values are two-tailed. All p values < 0.05 were considered
statistically significant. All analyses were performed with statistical
software (SAS release 8.1; SAS Institute; Cary, NC).
| Results |
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20/h and were invited to join the CPAP program.
No patients refused, and all were followed up for the duration of the
study period. We did not lose any patients during follow-up. The
baseline demographic and sleep study features for patients with and
without OSA are shown in Table 1
. Patients with OSA were slightly older, more obese, and more likely to
be men than those without OSA. Moreover, OSA patients displayed
increased fragmentation of sleep as evidenced by lower sleep efficiency
and increased representation of stages 1 and 2 sleep than those without
OSA. As expected, OSA patients had a higher AHI and lower mean arterial
oxygen saturation (SaO2) compared to
those without OSA.
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4.5 h/d), 83% and
79% of the patients in this program were compliant with their CPAP
therapy at 3 months and 6 months, respectively.
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| Discussion |
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4 h of CPAP use per night), 84% of the eligible
CPAP recipients were compliant with CPAP over the first 6 months of the
program. Second, as expected, with the application of and compliance
with CPAP therapy, there was a marked improvement in the patients
daytime sleepiness as measured by the ESS. In just 2 weeks following
initiation of CPAP therapy, we observed a 44% relative reduction in
the average daytime sleepiness for our cohort of patients. More
importantly, this improvement was sustained for the duration of the
6-month follow-up period, suggesting that continued compliance with
CPAP provides long-term benefits for patients with OSA. Third, women,
older patients, and those who experienced marked improvements in their
daytime sleepiness were more likely to be compliant with CPAP at 6
months than those without these parameters.
Several large studies10
11
12
13
have been previously published
concerning CPAP compliance in the community, which have shown
compliance rates ranging from 65 to 80%. Such a wide variation in the
reported compliance rates may in part be related to the way in which
compliance has been measured. For instance, McArdle and
coworkers14
reported a 6-month compliance rate of 85%
using a program similar to ours. However, their definition of
compliance was > 2 h/night of CPAP use.14
Moreover, they
used built-in counters on CPAP devices to capture utilization data;
however, these devices tend to overestimate actual compliance as
measured by pressure-actuated devices such as the one we
used.15
16
In an earlier work, Kribbs and
coworkers15
used a microprocessor to measure
"actual" compliance and reported an average duration of CPAP
use of 4.9 ± 2.0 h (on days that CPAP was used) over a
3-month period. In our program, we observed an average duration of CPAP
use of 6.2 ± 1.8 h over a similar time frame. In a more recent
study, Pepin and coworkers16
reported a 3-month compliance
rate of 74% using criteria of > 4 h of use per day. Even using very
stringent criteria for compliance in our study (
4 h of use), we
found that 87% and 84% of patients were compliant at 3 months and 6
months, respectively, suggesting our program was effective in securing
adequate compliance in most OSA patients.
We believe that several factors were important in producing good CPAP
compliance among our cohort of patients. First, we carefully selected
patients with "objective" documentation of OSA (using an AHI of
20/h) for our program and systematically treated all of them with
CPAP. Patients with an AHI < 20/h were enrolled on a case-by-case
basis (data not included in this analysis). Second, we designed our
program to maximize the compliance rate in our participants. We
incorporated the elements that have been suggested by previous
investigators6
to be important for improving CPAP
compliance over the long term. These measures included intense patient
education, use of a dedicated CPAP nurse to ensure close follow-up of
patients (particularly during the first 2 weeks of therapy),
troubleshooting when necessary, and rapid involvement of sleep
physicians to solve compliance issues for difficult-to-manage patients.
Third, we provided the CPAP device and ancillary services free of
charge to the patients, removing significant financial concerns for
patients.
Our findings that increasing age, female sex, and changes in ESS scores from baseline were associated with CPAP compliance are consistent with findings by McArdle and coworkers14 but dissimilar to those from Janson and coworkers.17 However, the latter study employed a case-control design (which is prone to more biases),18 had smaller study sample, and, most importantly, used only oximetric results for OSA diagnosis, which may have led to a diagnostic misclassification.
The present study has certain limitations. First, while good CPAP
compliance was achieved in a vast majority of OSA patients in our
program, due to the nature of the study design, it remains uncertain
which elements or components of the program were responsible for this
success. Indeed, the uncontrolled protocol used in this study makes it
difficult to attribute the excellent CPAP compliance rates directly to
the comprehensive CPAP program. Nevertheless, the totality of evidence
from our study, as well as those of others,7
15
suggests
that high compliance rates to CPAP can be achieved in a environment
that fosters patient education, comprehensive follow-up, and integrated
care. Second, before we started the program, we decided collectively to
use the criteria of an AHI
20/h as the treatment threshold. This
decision is partly based on previous report of increased mortality in
OSA subjects with an AHI
20/h who are untreated.19
There is evidence that some patients with an AHI < 20/h may also
benefit symptomatically from nasal CPAP, but the results are not
definitive and it is not possible at the moment to clearly identify the
subjects (with an AHI < 20/h) who might benefit. We do not wish to
imply that OSA patients with an AHI < 20/h should not be treated. Our
study did not include these subjects, and therefore we cannot report on
the CPAP compliance rate in these subjects. Further studies will be
necessary to determine the treatment threshold and compliance rate in
OSA subjects with mild disease.
In summary, our study findings suggest that high CPAP compliance rates are achievable in the community through a comprehensive CPAP program that provided free CPAP devices, extensive education, and follow-up services for symptomatic OSA patients with moderate-to-severe disease through a multidisciplinary team approach. Future studies are needed to determine which of the components of the program are the critical pieces in effecting excellent long-term CPAP compliance rates in the community.
| Acknowledgements |
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| Footnotes |
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Dr. Sin is supported by a New Investigator Award from the Canadian Institutes of Health Research.
Received for publication May 17, 2001. Accepted for publication August 8, 2001.
| References |
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