Comparison of sleep parameters at titration and subsequent compliance between CPAP-pretreated and non-CPAP-pretreated patients with obstructive sleep apnea

Comparison of sleep parameters at titration and subsequent compliance between CPAP-pretreated and non-CPAP-pretreated patients with obstructive sleep apnea

Sleep Medicine 8 (2007) 773–778 www.elsevier.com/locate/sleep Original Article Comparison of sleep parameters at titration and subsequent compliance...

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Sleep Medicine 8 (2007) 773–778 www.elsevier.com/locate/sleep

Original Article

Comparison of sleep parameters at titration and subsequent compliance between CPAP-pretreated and non-CPAP-pretreated patients with obstructive sleep apnea Masaaki Suzuki a

a,*

, Hanako Saigusa a, Taiji Furukawa

b

Department of Otolaryngology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, 173-8605 Tokyo, Japan b Department of Cardiology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, 173-8605 Tokyo, Japan Received 19 May 2006; received in revised form 5 January 2007; accepted 13 January 2007 Available online 23 May 2007

Abstract Background and purpose: Obstructive sleep apnea–hypopnea syndrome (OSAHS) patients undergo continuous positive airway pressure (CPAP) treatment for the first time on titration night, and then the effect of overnight CPAP treatment is estimated immediately. The purpose of this study is to compare the effects of CPAP-pretreated and non-pretreated on patients with OSAHS. Methods: Prospective randomized, controlled parallel study was performed. Seventy patients with OSAHS received autoadjusted CPAP treatment for 2 months and then received the standard manual titration (CPAP-pretreated group). The other 70 did not receive any CPAP treatment before receiving the standard manual titration (non-CPAP-pretreated group). Results: The CPAP-pretreated group had significantly improved sleep efficiency and arousal index in non-rapid eye movement (NREM) sleep compared with the initial CPAP group at titration, whereas there were no significant differences between the two groups in other sleep parameters. Eight patients in the non-CPAP-pretreated group discontinued CPAP treatment 9 months after the titration, whereas one patient in the CPAP-pretreated group discontinued treatment. Conclusions: A preceding CPAP treatment showed minimal effects on sleep parameters on titration night and subsequent CPAP compliance rate, although it was speculated that this preceding treatment might be of benefit for better compliance in some patients. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Obstructive sleep apnea–hypopnea syndrome; Continuous positive airway pressure; Titration; Sleep efficiency; Arousals; Compliance

1. Introduction Obstructive sleep apnea–hypopnea syndrome (OSAHS) is caused by the periodic reduction or cessation of breath due to the narrowing or occlusion of the upper airway during sleep. Continuous positive airway pressure (CPAP) application is currently the noninvasive treatment of choice for the majority of patients with OSAHS. CPAP treatment markedly attenuates *

Corresponding author. Tel.: +81 3 3964 1211; fax: +81 3 3964 0659. E-mail address: [email protected] (M. Suzuki). 1389-9457/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.sleep.2007.01.013

obstructive apneas, hypopneas, snoring, flow limitations, desaturation and arousals and improves sleep fragmentation. It is currently recommended that the specific optimal pressure for each patient should be determined by manual titration performed during an attended overnight in-laboratory polysomnography (PSG) [1–3]. OSAHS patients encounter the CPAP apparatus for the first time on titration night, and then the effects of overnight CPAP treatment (i.e., titration parameters) are estimated immediately. However, not all patients subjectively sleep well in a CPAP titration setting because of inconvenience and intolerance of the initial phase of CPAP treatment itself. In contrast, auto-

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adjusted CPAP or formula-calculated fixed CPAP treatment sometimes precedes the titration night to familiarize patients with the CPAP apparatus or to prevent a cardiovascular, cerebrovascular attack or sudden death [4–6]. Although research data on CPAP titration have been accumulated, few analyses of the effect of the initial experience of the treatment itself (i.e., first-night effect of CPAP) on sleep parameters have been performed. The purpose of this study was to compare the effects of CPAP pretreatment and non-pretreatment on sleep architecture and other descriptors on titration night and for subsequent CPAP compliance rate. 2. Patients and methods 2.1. Protocol A prospective randomized, controlled study design was employed. OSAHS patients in whom apnea–hypopnea index (AHI) was P20 events/h by overnight baseline PSG were divided into two groups using a random number table and sealed envelopes. Seventy OSAHS patients received autoadjusted CPAP treatment for 2 months and then received the standard manual titration (CPAP-pretreated group). The other 70 patients did not receive any CPAP treatment before receiving the standard manual titration (non-CPAP-pretreated group). For patients in the CPAP-pretreated group, technologists provided 30-min instructions on the CPAP apparatus, nasal masks, and how to adjust the autoadjusted CPAP, as well as information about symptoms indicating an incorrect CPAP setting. Technologists also sufficiently performed hands-on intervention. Then a REMStar Auto (Respironics; Pittsburgh, PA, USA) autoadjusted CPAP machine was prescribed for 2 months after the diagnostic study until the standard CPAP manual titration night. The pressure range was set between 4.0 and 20.0 cmH2O before titration. There was a card with a built-in monitoring chip in the REMstar Auto CPAP machine for the collection and storage of CPAP pressure and usage data. The monitoring device provided the pressure at which the patient spent 90% of the night at or below (90% device pressure) for each patient. Titration was performed manually during an attended overnight in-laboratory sleep-in another 2 months after the baseline PSG night. For patients in the non-CPAP-pretreated group, the standard CPAP manual titration by the technologists was scheduled also in another 2 months after the baseline PSG night. Sufficient instruction on the CPAP apparatus, nasal masks, and how to adjust the autoadjusted CPAP, in addition to information on symptoms indicating an incorrect CPAP setting, were given by technologists. Hands-on intervention was also performed by the technologists on titration night. The techniques for the standard CPAP manual titration were the same both in the

CPAP-pretreated and non-CPAP-pretreated groups. The technologists increased CPAP pressure during sleep in a stepwise fashion every 0.2–1.0 cmH2O to abolish respiratory events and arousals. The pressure at which arousals through supine rapid eye movement (REM) sleep disappeared was basically determined as the optimal pressure. The CPAP apparatus used for titration was a REMStar Pro, fixed-type CPAP machine (Respironics; Pittsburgh, PA, USA). REMStar Pro was prescribed for OSAHS patients in both groups at the optimal pressure for each patient as determined by titration study. Monthly follow-up for CPAP usage and problems was performed to establish effective utilization patterns and to remediate problems. The study protocol is outlined in Fig. 1. The waiting time for sleep services (first-night PSG and titration) is usually almost 2 months because of a shortage of sleep laboratories in Japan. The Institutional Review Board of our institute approved the study after a review by the Ethics Committee, and written informed consent was obtained from each patient before participation in the study. 2.2. Polysomnography (PSG) Overnight sleep studies, baseline PSG and CPAP titration, were carried out by digital PSG (Alice 4: Respironics; Pittsburgh, PA, USA) according to our previous method [7]. Briefly, electroencephalography (EEG, C4/A1, C3/A2), electrooculography (EOG), submental electromyography (EMG) and electrocardiography (ECG) using surface electrodes, measurement of air flow at the nose and mouth using a thermistor, measurement of respiratory movements of the rib cage and abdomen by inductive plethysmography, and measurement of percutaneous arterial oxygen saturation (SpO2) using a finger pulse oximeter were simultaneously carried out. The predominant sleep stage was scored for each 30-s epoch according to the criteria established by Rechtshaffen and Kales (R&K) [8]. Arousals were identified according to the criteria of

Fig. 1. Study protocol. CPAP-pretreated group, after baseline (first night) PSG; subjects slept with CPAP device at home for 2 months and in subsequent standard manual titration study in the sleep laboratory (n = 70). In the non-CPAP-pretreated groups, patients did not use CPAP device for 2 months at home and received the standard manual titration (n = 70). AHI, apnea–hypopnea index; OSAHS, obstructive sleep apnea hypopnea syndrome.

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the American Sleep Disorders Association (ASDA) [9]. Arousals preceded by the termination of breathing events or snoring were defined as respiratory arousals. Spontaneous arousals were defined as pure EEG arousals without clear changes in other physiological parameters or movement arousals, excluding periodic leg movement arousals according to the criteria of R&K by an EMG activation. Apneas were identified as a nearly flat airflow (<10% of the baseline, at which the baseline amplitude was identified during the nearest preceding period of regular breathing with a stable oxygen saturation) for at least 10 s. Hypopneas were identified as an airflow or a thoracoabdominal excursion of approximately <70% of the baseline for at least 10 s associated with either an oxygen desaturation of >3% or an arousal. 2.3. Statistical analyses All descriptive statistics are presented as means ± standard error. Descriptive statistics were calculated for each variable. Unpaired variables were evaluated by the Mann–Whitney U-test, and paired variables by the Wilcoxon t-test. All p-value tests were two-tailed. A p-value of less than 0.05 was considered to indicate statistical significance. The SPSS computerized statistical package (version 11.01) was used. 3. Results 3.1. Physical and baseline PSG parameters of CPApretreated and non-CPAP-pretreated groups

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0.2 ± 0.1 and 7.3 ± 1.9 to 0.2 ± 0.1 (%), respectively (each p value was less than 0.001). These results show that the standard CPAP manual titration was so effective in both groups that it permitted the normalization of respiratory parameters. 3.3. Differences in sleep parameters between CPAPpretreated and non-CPAP-pretreated groups Under an adequate attenuation of respiratory events, we compared sleep parameters between the two groups. Table 3 shows the comparison of changes in sleep parameters from the baseline to titration PSG. The average changes in sleep efficiency (SE) in the CPAP-pretreated and non-CPAP-pretreated groups were 8.3% ± 1.7 and 1.2 % ± 1.5, respectively, suggesting that the CPAP-pretreated group had a significantly improved SE compared with the non-CPAP-pretreated group. There was a significant difference also in the absolute figures of the SE between the two groups (p = 0.002). In contrast, there were no significant differences between the two groups in changes in other parameters (Table 3). In the next series of this study, the effects on arousal changes from the baseline to titration PSG between the two groups were elucidated. There was a significant difference in changes in arousal index (Ar-I) in non-rapid eye movement (NREM) sleep. There was a significant difference also in the absolute figures of the Ar-I in NREM between the two groups (p = 0.005). However, no significant differences were observed in changes in other parameters between the two groups (Table 4). 3.4. CPAP and compliance

Three of 70 patients in the CPAP-pretreated group and two of 70 patients in the non-CPAP-pretreated group were women. There were no significant differences in age and body mass index (BMI) between the CPAPpretreated and non-CPAP-pretreated groups. There were no significant differences in baseline PSG parameters between the two groups (Table 1). The baseline arousals between the two groups are compared in Table 2. There were no significant differences between the two groups (Table 2). 3.2. Efficacy of standard CPAP titration in CPAPpretreated and non-CPAP-pretreated groups The standard CPAP manual titration could attenuate overall respiratory events both in the CPAP-pretreated and non-CPAP-pretreated groups from the baseline to titration: AHI, 58.9 ± 2.1 to 7.0 ± 0.5 and 57.9 ± 2.1 to 9.1 ± 0.7 (events/h); apnea indices, 29.0 ± 2.9 to 0.6 ± 0.1 and 28.8 ± 2.7 to 2.1 ± 0.3 (events/h); hypopnea indices, 30.0 ± 1.7 to 6.4 ± 0.5 and 29.1 ± 2.1 to 8.3 ± 0.6 (events/h); and cumulative percentage of time spent at saturation below 90 (CT 90), 9.3 ± 1.4 to

The average optimal pressures determined by titration PSG in the CPAP-pretreated and non-CPAP-pretreated groups were 11.3 ± 0.3 and 11.7 ± 0.4 cmH2O, respectively, which were not significantly different. The average 90% device pressure for autoadjusted CPAP during the two months before the titration night in the CPAP-pretreated group was 9.3 ± 0.3 cmH2O, which was lower than the average optimal pressure (11.3 ± 0.3 cmH2O) by 2.0 cmH2O (p < 0.001). In the CPAP-pretreated group, the compliance during the 2 months before titration was 4.1 ± 0.4 h. The average hours of daily use in another nine months from titration PSG in the CPAP-pretreated and non-CPAP-pretreated groups were 5.1 ± 0.5 and 4.9 ± 0.4 h, respectively; which were not significant different (p = 0.54). There was a significant difference between the pretreatment compliance of 4.1 h and post-titration compliance of 5.1 h in the CPAP-pretreated group (p = 0.036). Eight patients in the non-CPAP-pretreated group discontinued CPAP treatment nine months after the titration night, whereas one patient in the CPAP-pretreated group discontinued. Yates v-test showed that there

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Table 1 Comparison of physical and first-night PSG parameters between CPAP preceding and non-CPAP-pretreated groups

Age BMI (kg/m2) AHI (events/h) CT90 (%) TST (min) SE (%) %REM %Stage1 %Stage2 %SW Ar-I (events/h) Sleep latency (min) REM latency (min)

CPAP-pretreated (70)

Non-CPAPpretreated (70)

p

45.3 ± 1.2 28.4 ± 0.6 58.9 ± 2.1 9.3 ± 1.4 368 ± 7.8 78.7 ± 1.6 16.3 ± 0.7 43.5 ± 2.4 39.7 ± 2.3 0.5 ± 0.2 56.4 ± 2.0 17.3 ± 2.3 134.0 ± 8.5

47.5 ± 1.4 27.8 ± 0.5 57.9 ± 2.1 7.3 ± 1.2 362 ± 8.9 80.5 ± 1.1 16.2 ± 0.7 41.9 ± 2.3 40.9 ± 2.0 0.8 ± 0.2 54.2 ± 1.5 13.6 ± 1.3 135.2 ± 7.5

0.20 0.65 0.71 0.34 0.72 0.79 0.83 0.69 0.77 0.19 0.45 0.91 0.78

AHI, apnea–hypopnea index; CT 90, cumulative percentage of time spent at saturation below 90; TST, total sleep time; SE, sleep efficiency; %REM, percentage of rapid eye movement sleep time in TST; %stage 1, percentage of stage 1 sleep in TST; %stage 2, percentage of stage 2 sleep in TST; %SW, percentage of slow-wave sleep in TST; Ar-I, arousal index.

Table 2 Comparison of first-night arousal indices between CPAP preceding and non-CPAP-pretreated groups

REM Ar-I NREM Ar-I Respir Ar-I in REM Spont Ar-I in REM Respir Ar-I in NREM Spont Ar-I in NREM

CPAPpretreated (70)

Non-CPAPpretreated (70)

p

48.1 ± 2.1 60.4 ± 2.0 44.5 ± 2.2 3.9 ± 0.4 53.1 ± 2.3 7.3 ± 0.6

45.7 ± 1.5 60.0 ± 2.2 41.0 ± 1.6 4.8 ± 0.6 52.5 ± 2.5 7.5 ± 0.7

0.53 0.95 0.25 0.72 0.87 0.97

Ar-I, arousal index; NREM, non-REM; Respir Ar-I, respiratory arousal index; spont Ar-I, spontaneous arousal index.

Table 3 Comparison of changes in sleep parameters from baseline to titration PSG between CPAP preceding and non-CPAP-pretreated groups CPAPpretreated (70) Changes in SE (%) Changes in %REM Changes in %Stage1 Changes in %Stage Changes in %SW Changes in Ar-I (events/h) Changes in Sleep latency (min) Changes in REM latency (min) *

Significant difference.

Non-CPAPpretreated (70)

P

8.3 ± 1.7 6.8 ± 0.9 26.1 ± 2.3 2 17.2 ± 2.0 2.0 ± 0.5 33.8 ± 2.2

1.2 ± 1.5 5.3 ± 1.1 20.3 ± 2.7 14.3 ± 1.9 1.5 ± 0.5 27.7 ± 2.0

0.006* 0.430 0.075 0.530 0.835 0.063

5.2 ± 3.2

1.7 ± 2.0

0.246

46.7 ± 9.8

30.1 ± 9.9

0.178

Table 4 Comparison of changes in arousal indices from baseline to titration PSG in CPAP preceding and non-CPAP-pretreated groups

Changes in Changes in Changes in REM Changes in REM Changes in NREM Changes in NREM *

CPAPpretreated (70)

Non-CPAPpretreated (70)

P

REM Ar-I NREM Ar-I respir Ar-I in

27.3 ± 2.4 37.5 ± 2.3 39.2 ± 2.2

26.9 ± 1.9 30.7 ± 2.7 35.2 ± 1.8

0.560 0.036* 0.266

spont Ar-I in

9.9 ± 1.1

7.9 ± 0.9

0.330

respir Ar-I in

46.6 ± 2.3

42.4 ± 2.5

0.198

spont Ar-I in

9.0 ± 1.0

11.2 ± 1.3

0.377

Significant difference.

was a significant difference between the two groups in CPAP adherence (p = 0.039). 4. Discussion There are findings in this study that may contribute to the understanding of the therapeutic theory on CPAP for patients with OSAHS. Pretreatment increased the improvement in SE from baseline and also resulted in a decrease from baseline in the total Ar-I during NREM sleep. Few other changes were significantly different between the groups. Pretreatment affects subsequent adherence to CPAP. 4.1. Sleep efficiency in titration night CPAP application is currently the most frequently used medical treatment for patients with OSAHS. This treatment requires the determination of the specific pressure for each patient in initiating. It is recommended that this should be accomplished by manual titration performed during an attended overnight in-laboratory PSG [1–3]. Titration endpoints for ‘‘optimal’’ CPAP can include values that lead to the elimination of apneas–hypopneas, snoring, inspiratory flow limitation and arousals. CPAP induced the attenuation of arousals and light sleep, and slow wave (SW, stages 3 and 4) sleep enhancement [3,10]. In contrast, titration night PSG does not always improve SE compared with baseline PSG because of the inconvenience and intolerance of the initial phase of CPAP treatment itself (first-night effect of CPAP). SE on titration night is important because of its strong correlation with a change in score on the Epworth Sleepiness Scale at follow-up and with CPAP compliance from 6 to 12 months [11]. In addition, Drake et al. reported that OSAHS patients whose SE improved during CPAP titration used their CPAP machines for an average of more than 2.03 h per night after the mean follow-up days of 46.9 as compared with individuals whose SE did not improve during CPAP

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titration [12]. Patient compliance may be correlated with the degree of improvement in SE that patients experience during their initial titration night. Hukins et al. randomly assigned 91 patients to commence CPAP either at an arbitrary pressure determined on the basis of BMI before titration or at an optimal pressure after a CPAP titration, and demonstrated that there was a significantly higher SE at arbitrary pressure on titration night in agreement with our results [13]. In the present study, the CPAP-pretreated group had a significantly better improvement in SE. A preceding CPAP treatment would be of benefit for better compliance of patients whose SE is low at baseline PSG.

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ture. However, titration protocol in this study (e.g., starting pressure, rate of titration up or down) was the same across subjects. There were statistical limitations because the power calculation was not done before performing the study, which might have reduced the value of the present study. In summary, a preceding CPAP treatment showed minimal effects on sleep parameters on titration night and subsequent CPAP compliance rate when a sufficient intervention for CPAP treatment was performed on patients with OSAHS, although it was speculated that this preceding treatment might be of benefit for better compliance in patients whose SE is low or arousal index in NREM is high.

4.2. Respiratory arousals Nocturnal arousals are a prominent feature and the essential cause of a disturbed sleep structure in patients with OSAHS. Respiratory effort produces arousals by mechanoreceptors, and these arousals induce upper airway muscle tonus activity and apnea termination coincident with postapneic hyperventilation [14]. These respiratory arousals are associated with sleep-related breathing events registered in PSG tracing and might be linked to undetected increased ventilatory efforts [15]. Detecting arousals would lead to the detection of sleep-related breathing events. There may be differences in arousability between sleep stages. Ar-I in NREM sleep is higher than that in REM sleep for patients with severe OSAHS [16]. In the baseline PSG, the highest respiratory Ar-I was observed in stage 1, which is significantly different from the frequencies in stage 2, SW and REM, and these respiratory Ar-Is decreased significantly from the baseline PSG to the first CPAP titration night [17,18]. In REM sleep, patients are not entirely dependent on arousal or on chemical and mechanoreceptor feedback to increase flow [19]. The arousal threshold during REM sleep state might be higher than that during NREM sleep [17,18]. Thus, arousals in NREM sleep might be much more correlated with respiratory events than those in REM sleep. 4.3. Limitations in this study The most ideal study to compare arousals should have other micro-architectural sleep parameters, such as cyclic alternating pattern, microarousals (less than 3 s) or delta power [20]. If these parameters were analyzed, other findings regarding arousal might be obtained. A single-night titration study design might have affected our results [3]. It is difficult to compare a full overnight study to a CPAP titration study in terms of sleep architecture. Sleep architecture may vary due to the effects of CPAP titration, and the time the effective CPAP pressure was achieved might vary by patient factors, circumstances or their circadian rhythm and, therefore, may have affected sleep architec-

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