Comparisons of Continuous Positive Airway Pressures Determined by Conventional Manual Titration in a Sleep Center, During Sleep Endoscopy, and Auto-Titration at Home

Abstract

Importance:

Drug-induced sleep endoscopy (DISE) could be valuable to determine an appropriate therapeutic pressure for obstructive sleep apnea (OSA).

Objective:

The continuous positive airway pressure (CPAP) determined by DISE was regarded as equal to the conventional titrating pressure. There is no study comparing the DISE-titrating pressure and the home-based automatic CPAP (APAP) titrating pressure. This study compared the DISE-titrating pressure, conventional titrating pressure, and home-based APAP titrating pressure.

Design:

Retrospective comparative cohort study.

Setting:

This study was conducted in a single medical center in Taiwan.

Participants:

A total of 59 participants with OSA who had 3 titrating pressures determined by DISE, conventional titration and home-based APAP titration were analyzed.

Interventions or Exposures:

Therapeutic CPAP pressure was determined by 3 methods: DISE, conventional titration, and home-based APAP titration.

Main Outcome Measures:

Home-based APAP titrating pressure was determined as 90% to 95% of APAP used at home for 2 weeks. The DISE-titrating pressure was determined manually based on direct visualization of upper airway patency during DISE examination. The conventional titrating pressure was determined manually under polysomnography (PSG) guidance in a sleep center. The correlation and difference between these 3 pressures were analyzed.

Results:

The home-based APAP titrating pressure, conventional titrating pressure, and DISE-titrating pressure were 8.8, 8.1, and 8.2 cmH₂O, respectively. Good reliability was observed in pairs between all 3 pressures. The DISE-titrating pressure and the conventional titrating pressure were lower than the home-based APAP titrating pressure. There was no difference between the DISE-titrating pressure and the conventional titrating pressure.

Conclusions:

DISE could help provide a therapeutic CPAP pressure similar to the conventional titrating pressure in sleep center and APAP titrating pressure at home.

Relevance:

DISE could be a valuable alternative titrating method, especially in countries where PSG is expensive, time-consuming and difficult to access, and could facilitate earlier and more effective management of patients with OSA.

Graphical Abstract.

Key Message

1. Drug-induced sleep endoscopy could be an alternative titration method for determining therapeutic pressures for patients with obstructive sleep apnea (OSA).

2. Drug-induced sleep endoscopy could facilitate earlier and more effective management of patients with OSA.

Introduction

Drug-induced sleep endoscopy (DISE) evaluates the obstructive sites of the upper airway and assists in individualized surgical planning in patients with obstructive sleep apnea (OSA). The DISE can be performed easily and safely. ¹ DISE was regarded as an emerging technique in precision medicine and helps evaluate surgical and non-surgical treatments.^2,3 DISE could help determine the potential causes of continuous positive airway pressure (CPAP) failure and offer suitable interventions to improve CPAP adherence, ⁴ predict the likelihood of CPAP failure,^2,5 and facilitate a better understanding of mechanisms of higher CPAP pressure, which might be corrected by oral appliance or surgery. ⁶

Conventionally, the CPAP pressure is manually titrated at sleep center guided by polysomnography (PSG). Automatic CPAP (APAP) has a built-in memory for downloading usage data, and 90% or 95% of the pressure used for a period is used for setting a therapeutic pressure.^7-10 However, home-based APAP titration is labor-intensive and requires at least 1 to 2 weeks. Many investigators tried to determine useful equations for obtaining pressure^11,12; however, only 86% of optimal estimation was obtained. ¹³

In 2012, DISE was firstly used to assist CPAP titration for obtaining therapeutic pressure which was found not to be different from the conventional titrating pressure. ¹⁴ The authors concluded that the DISE-titrating method is cheaper and less time-consuming and could be an alternative to the conventional titration method. To date, no study has compared the DISE-titrating pressure to the home-based APAP titrating pressure. This study simultaneously compared the DISE-titrating pressure, conventional titrating pressure and home-based APAP titrating pressure.

Materials and Methods

Participants

This is a retrospective comparative cohort study. The inclusion criteria were: (1) age 20 to 80 years, (2) apnea-hypopnea index (AHI) ≥5, (3) had received manual titration at our sleep center to obtain the conventional titrating pressure (P__Lab), (4) had received DISE and obtained DISE-assisted titrating pressure; P__DISE), (5) had used home APAP for at least 2 weeks and could obtain a 90% or 95% pressure from the built-in memory to obtain a home-based APAP titrating pressure (P__Home), and (6) not received treatment for OSA previously. The exclusion criteria were: (1) age <20 years or >80 years, (2) use of sedatives or psychiatric medicine, (3) heavy alcohol (more than 1 bottle of beer every day) or cigarette (more than 1 package per day) consumption, and (4) body mass index (BMI) ≥40 kg/m².

We totally reviewed 358 patients who underwent both conventional titration and the DISE procedure between January 2016 and July 2021. A total of 140 of the 358 patients had both P__Lab and P__DISE values. Among the 140 patients, 59 patients had used home APAP and could obtain the P__Home and were included in the final analysis. This study was approved by the Institutional Review Board of Taipei Tzu Chi Hospital (protocol no 10-XD-077). The informed consent was waived owing to the retrospective design.

Data Collection and Measurements

Anthropometric Characteristics

We collected age, sex, BMI, cigarette smoking and alcohol consumption status, comorbidities (diabetes mellitus, hypertension, cardiovascular accident, coronary artery disease, chronic obstructive pulmonary disease, and asthma) and the waiting time for conventional CPAP titration, DISE, and home APAP trial.

Polysomnography

The standard PSG was performed by trained technicians. The PSG recording included the sleep stage, position, oxygen saturation, airflow by the thermistor, and nasal pressure transducer. The position was identified using a trunk-position sensor. Each PSG recording lasted at least 6 hours. Each 30 second epoch was manually scored by technicians and rechecked by a sleep specialist. The sleep stage and respiratory events were rescored according to the 2012 American Academy of Sleep Medicine Guidelines.

Conventional Titration in the Sleep Center

Conventional titration was performed using DeVilbiss CPAP (DeVilbiss Healthcare, Somerset, PA, USA). The pressure was started at 4 cmH₂O and titrated upward in 1 to 2 cmH₂O increments for over ≥5 minutes periods to eliminate all respiratory events, snoring, and oxygen desaturation and to minimize arousals in all sleep stages in supine position. After reaching the desired pressure in rapid eye movement (REM) sleep stage for at least 30 minutes in supine position, a downward titration of 1 to 2 cmH₂O was attempted to minimize the hysteresis phenomenon, and the final pressure was recorded as P__Lab. ¹⁵

Manual Titration During Drug-Induced Sleep Endoscopy

The DISE was carried out in the operating room. Before the patient was sedated, we used folded surgical drapes to simulate the pillow that the patient used at home. Subsequently, the patient was sedated by the anesthesiologists with standard propofol titration protocol, which starts with a loading dose of 1 mg/kg and is maintained at 200 to 300 μg/kg/minute. A bispectral index (BIS) instrument was applied to monitor and maintain stable sleep depth (BIS score, 60-70). After the patient was asleep in the supine position, the fiberoptic nasopharyngoscope was inserted from the left or right nostril. After recording the level, pattern, and severity of upper airway collapse, the nasopharyngoscope was withdrawn and the CPAP instrument (ResMed S9 AutoSet, using CPAP mode, Bella Vista, NSW, Australia) was turned on. After confirming mask fitted adequately, the nasopharyngoscope was re-inserted from the silicone nasal mask through a 5 mm cruciform hole which was made for assurance of mask tightness. (Supplement Figure 1) The starting pressure was 4 cmH₂O and was manually increased by 1 cmH₂O every time until satisfactory upper airway patency was achieved and no more snoring or oxygen desaturation was observed. The pressure was then titrated downward by 1 cmH₂O to minimize the hysteresis phenomenon. ¹⁵ To confirm the final optimal pressure, the CPAP was switched off and turned on again to check if the assumed pressure did open the airway firmly on each occasion; this pressure was recorded as the P__DISE.

Auto-Titration at Home

Patients used home APAP (ResMed S9 or S10 AutoSet and Philips Respironics auto-CPAP, Murrysville, PA, USA) for at least 2 weeks, and the usage data was downloaded. The 90% or 95% of pressure used for 2 weeks was recorded as the P__Home.

Statistics

Normally distributed continuous variables were reported as mean and standard deviation and analyzed using a repeated measures analysis of variance (ANOVA) with a post hoc test using the Bonferroni correction method. Non-normally distributed continuous variables were presented as median (interquartile) and analyzed using the Friedman test with a post hoc test by the Wilcoxon signed-rank test with the Bonferroni correction at a significant level set at P < .0167. The categorical variables were presented as numbers (percentages). Intraclass correlation coefficient (ICC) was used to estimate the inter-rater reliability and the 95% confidence intervals (CIs) were calculated based on a mean rating (k = 3), absolute agreement, and a 2-way mixed-effects model where participants are random and measures of effects are fixed. The ICC value <0.4, 0.4 to 0.59, 0.6 to 0.74, and 0.75 to 1.0 are indicative of poor, moderate, good, and excellent reliability, respectively. ¹⁶ To pairwise comparisons of these 3 pressures, a repeated measures ANOVA with a post hoc test using the Bonferroni correction method was used. The significance level was set as 2-sided P < .05. Multivariate stepwise linear regression analysis was performed to evaluate the factors affecting the difference between P__DISE and P__Lab. All statistical analyses were carried out using SPSS Statistics for Windows, version 17.0 (SPSS, Inc, Chicago, IL, USA).

Results

Table 1 shows the age of the participants was 52.1 ± 10.9 years and the BMI was 27.0 ± 3.6 kg/m². The majority were males (76.3%). The sleep stages were: 30% ± 14.1%, 53% ± 11.8%, 4.2% ± 7.1%, and 12.7% ± 5.9% for N1, N2, N3, and REM sleep, respectively. The AHI was 45.1 ± 21.3/hour. The desaturation index was 37.6 ± 23.1/hour. Three participants had mild OSA with AHI 5 to 14.9/hour (1 had symptoms, 2 had difficult-to-control hypertension), 12 participants had moderate OSA with AHI 15 to 29.9/hour, and 44 participants had severe OSA with AHI ≥30/hour. Twenty-nine patients used Respironics APAP and 30 patients used ResMed APAP (7 with S9 Autoset; 23 with S10 Autoset).

Table 1.

Characteristics of Study Participants.

Characteristics of study participants (n = 59)
Age (y)	52.1 ± 10.9
Body mass index (kg/m2)	27.0 ± 3.6
Male, n (%)	45 (76.3%)
Drinking, n (%)	11 (18.6%)
Smoking, n (%)	19 (32.2%)
Chronic obstructive pulmonary disease, n (%)	11 (18.6%)
Asthma, n (%)	6 (10.2%)
Diabetes mellitus, n (%)	8 (13.6%)
Hypertension, n (%)	26 (44.1%)
Cerebrovascular accident, n (%)	3 (5.1%)
Coronary artery disease, n (%)	3 (5.1%)
OSA severity
Mild OSA with AHI = 5.0-14.9/h, n (%)	3 (5.1%)
Moderate OSA with AHI = 15.0-29.9/h, n (%)	12 (20.3%)
Severe OSA with AHI ≥30.0/h, n (%)	44 (75.6%)
Auto-continuous positive airway pressure brand
ResMed	30 (50.8%)
Respironics	29 (49.2%)
Polysomnography variables
N1 sleep (%)	30.0 ± 14.1
N2 sleep (%)	53.0 ± 11.8
N3 sleep (%)	4.2 ± 7.1
Rapid eye movement sleep (%)	12.7 ± 5.9
AHI (events/h)	45.1 ± 21.3
Arousal index (events/h)	40.8 ± 19.9
Desaturation index (events/h)	37.6 ± 23.1
Mean oxygen saturation (%)	92.5 ± 2.3

Abbreviations: AHI, apnea-hypopnea index; OSA, obstructive sleep apnea.

Continuous variables were presented as mean ± standard deviation. Categoric variables were presented as number (%).

Table 2 and Figure 1 demonstrated that P__Home, P__Lab, and P__DISE were 8.8 ± 1.9, 8.1 ± 1.9, and 8.2 ± 1.8 cmH₂O, respectively. The P__Home was significantly higher than the P__DISE and P__Lab; however, there was no difference between the P__DISE and P__Lab.

Table 2.

Comparisons Between P__Lab, P__DISE, and P__Home.

Measurements	P_Home	P_Lab	P_DISE	P value
Pressure (cmH2O)
Mean ± SD	8.8 ± 1.9	8.1 ± 1.9 a	8.2 ± 1.8 b	.000 c
Outlier-1	N/A	14.0	14.0
Outlier-2	N/A	13.0	13.0
Maximal	12.8	12.0	12.0
Median (Q1, Q3)	9.3 (7.5, 10.0)	8.0 (7.0, 9.0)	8.0 (7.0, 9.0)
Minimal	5.0	5.0	5.0
Waiting time (d)
Median (Q1, Q3)	14 (7, 27)	27 (12, 42)	13 (6, 18) d	.000 e
Maximal	334	96	62
Minimal	1	1	1

Abbreviations: ANOVA, analysis of variance; P__DISE, drug-induced sleep endoscopy-assisted titrating pressure; P__Home, home-based auto-continuous positive airway pressure titrating pressure; P__Lab, conventional manual titrating pressure in a sleep center.

^aSignificant difference between P__Lab and P__Home.

^bSignificant difference between P__DISE and P__Home.

^cSignificant difference at P < .05 for a repeated measures ANOVA with a post hoc test using the Bonferroni correction method.

^dSignificant difference between P__DISE and P__Lab.

^eSignificant difference at P < .05 for the Friedman test with a post hoc test using the Wilcoxon signed-rank test with the Bonferroni correction at a significant level set at P < .0167.

Figure 1.

The comparisons between P__Home, P__Lab, and P__DISE. The P__Home is higher than P__Lab, and P__DISE. However, the P__Lab is not different from the P__DISE. P__DISE, drug-induced sleep endoscopy-assisted titrating pressure; P__Home, home-based auto-titrating pressure; P__Lab, manual titrating pressure in a sleep center.

*Significant difference with P < .05 (2-tail).

The waiting time for DISE is shorter than that for conventional titration method (13 days for DISE vs 27 days for conventional titration method, P = .000; Figure 2).

Figure 2.

The waiting time for P__Home, P__Lab, and P__DISE.

The waiting time for DISE was shorter than that of conventional manual titration in a sleep center. P__DISE, drug-induced sleep endoscopy-assisted titrating pressure; P__Home, home-based auto-titrating pressure; P__Lab, manual titrating pressure in a sleep center.

*Significant difference with P < .05 (2-tail).

Table 3 demonstrates good reliability between P__DISE and P__Home (ICC = 0.632, 95% CI [0.382-0.781], P = .000), between P__DISE and P__Lab (ICC = 0.695, 95% CI [0.485-0.819], p = .000), and between P__Home and P__Lab (ICC = 0.748, 95% CI [0.550-0.856], P = .000).

Table 3.

ICC to Estimate the Test-Retest/Intra-Rater Reliability Between Pressures in Pairs.

1. ICC for DISE-assisted titrating pressure and home-based APAP titrating pressure
	Intraclass correlation a	95% Confidence interval		F test with true value 0
		Lower bound	Upper bound	Value	df1	df2	P value
Average measures	0.632	0.383	0.781	2.869	58	58	.000
2. ICC for DISE-assisted titrating pressure and conventional titrating pressure in sleep center
	Intraclass correlation a	95% Confidence interval		F test with true value 0
		Lower bound	Upper bound	Value	df1	df2	P value
Average measures	0.695	0.485	0.819	3.240	58	58	.000
3. ICC for home-based APAP titrating pressure and conventional titrating pressure in sleep center
	Intraclass correlation a	95% Confidence interval		F test with true value 0
		Lower bound	Upper bound	Value	df1	df2	P value
Average measures	0.748	0.550	0.856	4.436	58	58	.000

Abbreviations: APAP, auto-adjusted continuous positive airway pressure; DISE, drug-induced sleep endoscopy; ICC, intraclass correlation coefficient.

^aICC estimates and their 95% confidence intervals were calculated based on a mean rating (k = 3), absolute agreement, 2-way mixed-effects model where participants are random and measures effects are fixed.

Table 4 showed the results of a repeated measures ANOVA test evaluating the null hypothesis that there is no difference among the 3 pressures. The results showed a significant difference: Wilks’ lambda = 0.836, F (2, 57) = 5.610, P = .006, η² = 0.164, thus providing significant evidence to reject the null hypothesis. Pairwise comparisons indicated significant differences between P__Home and P__DISE (mean difference = 0.610, 95% CI [0.119-1.101], P = .016) and between P__Home and P__Lab (mean difference = 0.669, 95% CI [0.250-1.089], P = .002). There was no significant difference between P__DISE and P__Lab.

Table 4.

Pairwise Comparisons of P__Home, P__Lab, and P__DISE.

Pressure (I)	Pressure (J)	Mean difference (I-J)	Std. error	P value a	95% Confidence interval for difference a
					Lower bound	Upper bound
P_Home	P_Lab	0.669	0.210	.002*	0.250	1.089
	P_DISE	0.610	0.245	.016*	0.119	1.101
P_Lab	P_Home	−0.669	0.210	.002*	−1.089	−0.250
	P_DISE	−0.059	0.236	.082	−0.531	0.412
P_DISE	P_Home	−0.610	0.245	.016*	−1.101	−0.119
	P_Lab	0.059	0.236	.082	−0.412	0.531

Based on estimated marginal means, *P < .05 (2-tail) significant different.

Abbreviations: P__DISE, drug-induced sleep endoscopy-assisted titrating pressure; P__Home, home-based auto-continuous positive airway pressure titrating pressure; P__Lab, conventional titrating pressure in sleep center.

^aAdjustment for multiple comparisons: lease significant difference (equivalent to no adjustments).

Table 5 demonstrates that the individual differences of each-pair of pressures were not different. The range of individual difference of P__DISE and P__Lab, P__Home and P__DISE, and P__Home and P__Lab were −7.0 to 6.0, −4.2.0 to 5.8, and −4.0 to 5.0 cmH₂O, respectively.

Table 5.

Individual Difference of Each-Pair of Pressures.

Measurements	P_DISE − P_Lab (cmH2O)	P_Home − P_DISE (cmH2O)	P_Home − P_Lab (cmH2O)	P value a
Median (Q1, Q3)	0 (−1, 1)	0.3 (−0.1, 1.3)	0.4 (−0.1, 1.9)	>.05
mean ± SD	0.06 ± 1.81	0.61 ± 1.88	0.67 ± 1.61
range	−7 to 6	−4.2 to 5.8	−4 to 5

Abbreviations: P__DISE, drug-induced sleep endoscopy-assisted titrating pressure; P__Home, home-based auto-continuous positive airway pressure titrating pressure; P__Lab, conventional manual titrating pressure in a sleep center.

^aFriedman Test with a post hoc test using the Wilcoxon signed-rank test with the Bonferroni correction at a significant level set at P < .0167.

The influencing factors of the difference between P__Lab and P__DISE were DM (beta = −.298, 95% CI −2.794 to 0.328, P = .014) and alcohol consumptions (beta = −.333, 95% confidence internal −2.641 to −0.43, P = .007), whereas the influencing factor of the difference between P__Home and P__DISE was only COPD (beta = .342, 95% CI 0.445-2.837, P = .008). The factors influencing the difference between P__Home and P__Lab could not be found in our analysis.

Discussion

The study was the first to simultaneously compare the DISE-titrating pressure, home-based APAP titrating pressure and conventional titrating pressure. The study demonstrated that DISE- titrating pressure correlated with conventional titrating pressure and home-based APAP titration pressure, and had a similar value to the conventional titrating pressure, but was lower than the home-based APAP titrating pressure.

Civelek et al firstly used DISE to obtain a therapeutic pressure and found that DISE-titrating pressure was not different from the conventional titrating pressure. ¹⁴ Our result was consistent, but there were some differences. The DISE-titrating pressure in their report was higher than the conventional titrating pressure (9.93 ± 4.76 vs 8.37 ± 3.84 cmH₂O, P = .116), whereas, in our study, there was no difference. The OSA severity in their participants was lower than that of ours (26.91 ± 3.98 vs 45.1 ± 21.3/hour), but this did not cause a lower DISE-titrating pressure than that in our study. This difference could be due to midazolam they used for anesthesia induction following propofol for maintaining anesthesia, which may have resulted in deeper sleep. After establishing a stable upper airway opening, they attempted to increase the pressure by an additional 2 cmH₂O to achieve a larger diameter of opening, but none of their patients had an increasing opening after the initial opening. This suggested that they only performed up-titration and not back-titration, resulting in a final pressure higher than ours. In their report, they used the same CPAP manufactory as in our study and obtained similar conventional titrating pressure. However, the CPAP manufactory was not identified in their report; there may be other factors affecting the DISE-titrating pressure between their study and ours.

In 2022, Wang et al compared the effects of 1 month CPAP therapy with pressure determined by the DISE-titration method or the conventional titration method. ¹⁷ They discovered that both modalities were comparable in terms of establishing the pressure settings. These 2 pressures in their report were higher than those in our report. The participants in their report had higher AHI, higher BMI, and deeper sleep depth than our report. The pressure they determined in the sleep center involved both auto-titration and manual titration. A study reported that a combination of auto-titrating pressure and manual titrating pressure was higher than manual titration ¹⁸ ; this might explain the higher manual titrating pressure than ours.

Only 2 previous reports and our present report evaluated the role of DISE in determining therapeutic pressure.^14,17 A larger, well-designed study is required to address this issue.

The comparisons of home-based APAP titrating pressure and conventional titrating pressure had been reported but the results were inconsistent.^18-20 Masa et al reported that home-based APAP titration had the same pressure level and treatment efficacy as conventional titration and could save cost and reduce the waiting time. ¹⁹ The CPAP they chose was not identified and the level was 8.8 ± 1.9 cmH₂O, which was higher than ours. They did not mention whether they performed upward/downward titration. The APAP they used was ResMed APAP and the level was 9.1 ± 1.9 cmH₂O, which was similar to ours. In Galetke et al’s report, the CPAP device they used was unknown, but the pressure level was 8.7 ± 2.9 cmH₂O, which was slightly higher than ours. They used the SOMNOSet APAP device (Weinmann, Germany), and the pressure level was 8.8 ± 1.9 cmH₂O, which was the same as ours. ²⁰ A comparative cohort study by Luo J, which had similar OSA severity and Chinese population as ours, showed that the home-based APAP titrating pressure using REMstar Auto (Philips Respironics, Inc) was higher than the conventional titrating pressure using Virtuoso device (Philips Respironics Inc; 9.8 ± 2.2 vs 7.3 ± 1.5 cmH₂O, P < .001); however, both had the same treatment efficacy. ¹⁸ In their report, the home-based APAP titrating pressure was higher than ours, which might be due to the fact that we used APAP devices from different manufacturers. However, this explanation may not be accurate. As Damiani MF reported, there is no difference in the pressures derived by REMstar APAP and ResMed APAP. ²¹

Different APAP devices might respond to respiratory events in different ways, resulting in different pressures, making the home-based APAP titration method less favored. ⁸ Besides, home-based APAP titration still requires at least 1 to 2 weeks. In our hospital, the waiting time for DISE was indeed shorter than that for the conventional method or home-based APAP titration.

In patients with diabetes mellitus, the increased leptin along with leptin receptor resistance can provoke metabolic and respiratory disturbances, causing neuromechanical dysfunction of the upper airway muscles and pharyngeal collapsibility during sleep.^22,23 The alcohol consumption can predispose them to upper airway collapse through negative effects on muscle tone. ²⁴ Anesthetics might enhance the negative impact of diabetes mellitus and alcohol consumption on upper airway collapsibility during DISE and a higher therapeutic P__DISE.

BIS monitors can provide a useful measure of sleep depth and have been shown to highly correlate with the hypnogram, showing a progressive decrease as sleep deepens and an increase during REM sleep.^25,26 However, BIS values can discriminate between N3 sleep and N1/N2 sleep but cannot discriminate between REM sleep and N1 sleep unless electromyography (EMG) activity is added to help identify REM sleep. ²⁵ In our present study, we did not use an EMG sensor to identify REM sleep during DISE and cannot determine if the patient achieved REM sleep. The sleep depth was monitored and maintained at a BIS score of 60 to 70, which represents a sleep depth of only N1 or N2 sleep. Therefore, our patient may not have achieved N3 sleep or REM sleep. The DISE was possibly performed under lighter sleep, making the DISE-titrating pressure level lower than the home-based APAP titrating pressure. The operating time of DISE was approximately 30 minutes, which was actually too short to achieve longer deep sleep.

The effective pressure in upward titration was higher than that in experimental downward titration in all sleep stages, especially during REM sleep. ¹⁵ Because lower effective pressure may improve CPAP compliance, we also performed downward titration in our sleep center and in DISE procedure. Therefore, the pressures of P__Lab and P__DISE were similar in our study. This result further encourages us to use P__DISE for earlier prescription of CPAP treatment for patients who are assessed as inoperable in the DISE result.

The pressure determined by manual titration in the sleep center was well reproducible and the pressures of 2 nights were highly correlated. ²⁷ The mean pressure in their report was 8.1 ± 2.9 mbar (8.26 ± 2.96 cmH₂O), which is similar to the 3 pressures in our study. The difference between 2 nightly titration pressures in their report was 0.51 ± 1.33 cmH₂O. In our report, the difference between P__Lab and P__DISE was 0.06 ± 1.33 cmH₂O, which was smaller than that reported by Wiest et al. Callahan et al used multiple nights of CPAP titration to determine a therapeutic prescription for fixed CPAP. ²⁸ They found that in some patients, small changes in pressure did not correlate with changes in residual respiratory function. Therefore, it could be concluded that the mean differences between P__Lab, P_{_Home}, and P__DISE in our study are within normal night-to-night differences and may not be large enough to affect treatment outcomes, despite the difference between P__Home and the other 2 pressures was statistically significant.

Taiwan’s National Health Insurance Administration does not have a standard payment for DISE procedures. The cost of DISE procedures between hospitals varies. In our hospital, the cost of conventional titration was NT$6300, which was fully covered by our national health insurance, and the cost of the DISE procedure was only NT$5458. Therefore, DISE is cheaper than conventional titration in our hospital. Performing a DISE has many advantages over the 2 conventional methods in our hospital, not only because it’s valuable in evaluating upper airway surgery, but also because the waiting time is shorter and the cost is lower. However, in some hospitals in Taiwan, the cost of DISE procedures was more expensive (NT$7000-NT$10000 out of personal expense) than conventional CPAP titration. In the report by Civelek et al, they also declared that DISE was cheaper than conventional titration. ¹⁴ Therefore, whether DISE-assisted titration can replace conventional titration should depend on the policies and practices of different hospitals in different countries.

Limitations

This study had several limitations. First, it was a retrospective study with small sample size. While DISE-titrating pressure and conventional titrating pressure were both obtained in the supine sleep position, Home-based APAP titrating pressure was possibly obtained not completely in supine position. The sleep depth of DISE might be different from the natural sleep depth of conventional titration method; it was difficult to compare DISE-titrating pressure and conventional titrating pressure. The differences in sleep posture and depth between home-based APAP titration and both DISE-titrating pressure and conventional titrating pressure could possibly affect the strength of the results in this study. Further well-designed studies are required to clarify this issue. The CPAP equipment we used for obtaining DISE-titrating pressure was different from that for obtaining conventional titrating pressure. The response to respiratory events during sleep of different CPAP equipment might be different; it was difficult to compare between DISE-titrating pressure and conventional titrating pressure in our study. We only collected data from patients who used ResMed and Respironics APAP, the ResMed APAP included 2 different generations (S9 Autoset and S10 Autoset) which might have different responses to respiratory events, resulting in different pressures. We did not record the subtypes of Respironics APAP due to a large number of subtypes. CPAP equipment in Taiwan was purchased at the patient’s own expense (about NT$55000). It is impossible to control all patients to buy the same CPAP equipments. For some patients, the time interval between obtaining the 3 pressures is very long. During this period, the patient’s condition may change, resulting in different pressure needed. The time lag in obtaining the titration pressures by 3 methods could affect the strength of the results in this study. Although DISE-titrating pressure is less costly compared to the conventional titrating pressure yet, it carries greater risk because of the general anesthesia. Physicians must consider whether DISE is worthwhile for individuals and centers, taking comorbidities and available facilities into account. The lack of consistency in the anesthesiologist performed intravenous general anesthesia, which may have resulted in varying levels of sleep depth during DISE. Finally, the 3 pressure values were obtained in completely different environments, which might have different effects on sleep depth.

Conclusions

DISE can be an effective alternative method for obtaining therapeutic CPAP pressure and could be considered in countries where PSG is expensive, time-consuming, and difficult to access. The DISE could facilitate earlier and more effective management of patients with OSA.