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Research Article

Correlation of therapeutic pressure between home automatic positive airway pressure and in laboratory polysomnography manual titration in patients with obstructive sleep apnea

[version 1; peer review: 1 approved with reservations, 1 not approved]
PUBLISHED 27 Jun 2024
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Abstract

Background

Continuous positive airway pressure (CPAP) is an effective treatment for obstructive sleep apnea (OSA). Automatic positive airway pressure (APAP) at home might be an alternative choice to identify optimal treatment pressure for OSA patients requiring CPAP treatment. Data on the association of effective treatment pressure between laboratory polysomnography (in-lab PSG) and home APAP has been limited. The aim of this study was to determine the correlation of effective CPAP pressure between in-lab PSG and home APAP.

Methods

A prospective cohort study was conducted. OSA participants aged 18 years or older who required CPAP therapy were included. Patients underwent in-lab PSG with manual CPAP titration to identify an effective treatment pressure. Patients also underwent APAP at home for 2 weeks to identify 95 percentile treatment pressure as an effective pressure.

Results

Fifty OSA patients (82% male) were included. Mean age was 48.9±14.6 years. Body mass index was 28.7±6.1 kg/m2. Polysomnographic data showed the effective treatment pressure of 10.4±2.9 cmH2O and the apnea-hypopnea index was 55.1±29.0 events/hour. Severe OSA was 76%. Home APAP data showed effective treatment pressure of 10.8±1.8 cmH2O. There was positive correlation of effective pressure between home APAP and in-lab PSG (r=0.472, P=0.001). The equation for predicting an in-lab effective pressure was: predicted pressure (cmH2O) = 2 + (home APAP ⁎ 0.78). Bland-Altman analysis showed good agreement between them, with a low mean difference of -0.428 cmH2O and 96% within the limit of agreement.

Conclusions

Home APAP pressure is moderately positively correlated with in-lab PSG effective pressure. The accuracy of home APAP is in agreement with in-lab PSG with manual CPAP titration. This APAP might be able to determine an effective therapeutic pressure in the sleep laboratory for OSA treatment.

Keywords

APAP, automatic positive airway pressure, continuous positive airway pressure, CPAP, obstructive sleep apnea, OSA

Introduction

Obstructive sleep apnea (OSA) is a condition caused by obstruction of the upper airway during sleep and can occur at any age, but the incidence is highest in middle-aged individuals. This disease is more prevalent in males than females.1,2 The main risk factor is obesity, which has been found in 70% of OSA patients.2 Symptoms of OSA usually include snoring, gasping during sleep, excessive daytime sleepiness, and lack of concentration while working. Diagnosis of OSA relies on the patient's medical history, symptoms, and risk assessment from a sleep questionnaire. Polysomnography (PSG), also known as a sleep test, is the standardized tool for diagnosing OSA.3

Continuous positive airway pressure (CPAP) is a standard effective treatment for moderate to severe OSA.2,4,5 CPAP delivers air pressure through a mask into the airway to keep the airway open during sleep to prevent apnea.4,5 There are two CPAP systems; 1) fixed-pressure or manual CPAP, and 2) automatic positive airway pressure (APAP). Fixed-pressure CPAP provides the optimal constant pressure determined by a full night CPAP titration in-laboratory PSG (in-lab PSG) or a split-night in-lab PSG. APAP provides multiple pressure levels, which can be adjusted automatically according to the patient's condition, detected by airflow resistance, body position, and nasal congestion. APAP can improve compliance and reduce daytime sleepiness better than fixed CPAP.4 Some previous studies have found no significant difference in treatment pressure between APAP and fixed-pressure CPAP,612 while other studies have reported significant differences in pressure.1320 CPAP pressure titrated in-lab by an automatic device is usually higher than that titrated in-lab manually.16,1820 There are conflicting data and unclear results. Advantageously, home APAP titration is more cost-effective than manual laboratory titration to determine optimal CPAP pressure for long-term use.9 Therefore, the aim of this study was to evaluate the correlation of the effective CPAP pressure between in-lab PSG and home APAP in Thai patients with OSA.

Methods

Clinical trial registration

This study, entitled “Correlation of therapeutic pressure between home automatic positive airway pressure and in laboratory polysomnography manual titration in patients with obstructive sleep apnea”, was prospectively registered with Thaiclinicaltrials.org with number TCTR20210331002 on 31 March 2021. https://www.thaiclinicaltrials.org/export/xml/TCTR20210331002

Study design and population

A prospective cohort study was conducted in Thammasat University Hospital, Thailand from April 2021 to January 2022. Subjects with suspected OSA aged 18 years or older and undergoing split-night PSG were included. Exclusion criteria were congestive heart failure, myocardial infarction, obesity hypoventilation syndrome, chronic obstructive pulmonary disease, stroke, claustrophobia, tracheostomy, uncontrolled psychiatric disorders, and residual apnea-hypopnea index (AHI) of 5 events per hour or more during in-lab CPAP titration.

Demographic data including age, sex, height, weight, body mass index, neck circumference, Epworth sleepiness scale (ESS), comorbidity, and in-lab PSG data including AHI, lowest pulse oxygen saturation, 3%oxygen desaturation index, optimal CPAP pressure and residual AHI after optimal CPAP trial were recorded. Moreover, home auto-CPAP data including 95th percentile pressure, residual AHI after optimal CPAP use, and duration of CPAP use were also recorded.

Ethic approval was obtained from the Human Research Ethics Committee of Thammasat University (Medicine), Thailand (IRB No. MTU-EC-OO-6-087/63, the approval number: 142/2020, the date of approval on July 2, 2022), in full compliance with international guidelines such as the Declaration of Helsinki, the Belmont Report, CIOMS Guidelines, and the International Conference on Harmonisation-Good Clinical Practice (ICH-GCP). All methods were performed in accordance with these guidelines and regulations. All participants provided written informed consent. This study was registered with thaiclinicaltrials.org with number TCTR20210331002 on 31 March, 2021.

CPAP manual titration in laboratory PSG

All subjects underwent split-night PSG using Compumedics Profusion® Sleep Software (Compumedics, Ltd, Victoria, Australia, Available from: https://www.compumedics.com.au/en/products/profusion-sleep-software/). Titration and scoring procedures followed the American Academy of Sleep Medicine guideline version 2.6.21,22 PSG data were manually scored by a certified sleep technician and were reviewed and verified by a certified a sleep specialist. CPAP titration was performed to determine a pressure to reduce the AHI to less than 5 events per hour and achieve a supine REM sleep duration of at least 15 minutes. CPAP was manually titrated with Resmed Lumis® 150 VPAP ST-A (Resmed, Sydney, Australia) in our sleep lab under full PSG monitoring that included electroencephalogram, electrooculogram, submental electromyogram, airflow from a thermistor, snoring, body position, thoracic and abdominal movements, and oxygen saturation. CPAP began at 4 cmH2O and gradually increased by 1 cmH2O steps every 10 min until apnea-hypopnea events disappeared. Optimal pressure, residual AHI, and all PSG data were also recorded.

Home APAP titration

All subjects used Resmed AirStart®10 APAP model (Resmed, Sydney, Australia) for a period of 2 weeks within 3 months after split-night PSG. APAP data were downloaded using ResScan® software version 5.9.0.9629 (Resmed, Sydney, Australia, Available from: https://support.resmed.com/en-gb/software-and-data-management/resscan/). An effective APAP pressure was the 95th percentile of the pressure results. An effective pressure, residual AHI, and all APAP data were also recorded. Good APAP compliance was defined as usage ≥4 hours per night for ≥70% of nights.23

Statistical analysis

Based on a previous study,16 the optimal CPAP pressure determined by in-lab APAP titration in OSA patients was 9.8± 2.2 cmH2O, whereas the optimal CPAP pressure determined by in-lab manual CPAP titration was 7.3 ± 1.5 cmH2O. We hypothesized that the two titration methods in our study would provide optimal pressures like this previous study. Thus, we needed to study 34 participants with 90% power and 5% type I error.

Data is presented as number (%) and mean ± standard deviation (SD). Student’s t-test was used to compare continuous variables between in-lab PSG and home APAP groups. Pearson’s correlation was used to determine the relationship of optimal pressure between two groups and to develop a predictive equation of the optimal CPAP pressure of in-lab PSG. Bland-Altman plots were used to determine agreement between the optimal pressures obtained from in-lab PSG and home APAP. The 95% limits of agreement, which represent where 95% of the future differences between the two methods would be expected, were calculated. The proportional bias was also assessed by performing a linear regression between the difference between the two measures and mean pressure for paired measurement. Two-tailed P-values of less than 0.05 were considered statistically significant. All data analyses were done on SPSS version 26.0 software (IBM Corp., Armonk, NY, USA).

Results

A total of 55 subjects with suspected OSA were screened, and 5 subjects were excluded (Figure 1). Fifty OSA subjects were included. Mean age was 48.9±14.6 years. 82% of subjects were male. Body mass index was 28.7±6.1 kg/m2. ESS score was 8.7±4.7. Common comorbidities were hypertension (40%), hyperlipidemia (44%), and allergic rhinitis (36%). PSG data showed AHI of 55.1±29.0 events/hour, optimal CPAP pressure of 10.4±2.9 cmH2O, and residual AHI was 1.6±1.5 events/hour. 76% of patients had severe OSA. The effective pressure of home APAP was 10.8±1.8 cmH2O, residual AHI was 1.5±1.0 events/hour and good APAP compliance was 58% (Table 1). There are no significant differences in the optimal pressure and the residual AHI between in-lab PSG and home APAP groups (Table 2).

7796235e-8535-4dcb-96ef-6007712a3d70_figure1.gif

Figure 1. Flowchart of recruitment to the study for patients with obstructive sleep apnea (OSA).

APAP=automatic positive airway pressure, CPAP=continuous positive airway pressure.

Table 1. Baseline characteristics of patients with obstructive sleep apnea.

CharacteristicsData (n=50)
Age, years48.9±14.6
Male41 (82)
BMI, kg/m228.7±6.1
Neck circumference, cm39.3±4.4
ESS, points8.7±4.7
Comorbidity
Hypertension20 (40)
Dyslipidemia22 (44)
Allergic rhinitis18 (36)
Heart disease5 (10)
Diabetes9 (18.0)
Obesity9 (18)
COPD1 (2)
Stroke1 (2)
Polysomnographic data
Total sleep time, minutes378.0±59.6
Sleep efficiency, %77.5±13.4
AHI, events/hour55.1±29.0
Lowest SpO2, %80.7±10.7
3%ODI, events/hour9.3±8.7
Optimal CPAP pressure, cmH2O10.4±2.9
Residual AHI after optimal CPAP trial, events/hour1.6±1.5
OSA severity
Mild2 (4)
Moderate10 (20)
Severe38 (76)
Home APAP titration data
95th percentile pressure, cmH2O10.8±1.8
Residual AHI after optimal CPAP use, events/hour1.5±1.0
95th percentile mask leak, L/minute22.7±13.3
CPAP use, hours/night4.7±1.9
Good compliance29 (58)

Table 2. Comparison of optimal pressure and residual AHI obtained from in-lab PSG and home APAP in patients with obstructive sleep apnea.

ParametersIn-lab PSGHome APAPP-value
Pressure, cmH2O10.4±2.910.8±1.80.252
Residual AHI, events/hour1.6±1.51.5±1.00.457

In all patients, including severe OSA patients, the optimal pressure obtained by in-lab PSG had significant moderately positive correlation with the effective pressure obtained by the home APAP (Table 3). Overall, an equation for predicting in-lab PSG derived optimal pressure is predicted pressure (cmH2O) = 2 + (0.78 ⁎ home APAP derived effective pressure) (Figure 2). The Bland-Altman comparison of the pressure obtained from in-lab PSG and the home APAP in all patients showed that there was very good agreement between them, with a low mean difference of -0.428 cmH2O (95% CI: -5.548 to 4.692 cmH2O) and only 2 of 50 measurements (4%) were outliers; 96% were within the limit of agreement (Figure 3). However, a proportional bias was detected (B = 0.648, P <0.001).

Table 3. Correlation of optimal pressure between in-lab PSG and home APAP in patients with obstructive sleep apnea.

PatientsData (n=50)Correlation coefficientP-value
All50 (100)0.4720.001
Good compliance29 (58)0.5860.001
Poor compliance21 (42)0.3400.132
Severe OSA38 (76)0.4520.004
Good compliance24 (63)0.6150.001
Poor compliance14 (37)0.1160.693
Non-severe OSA12 (24)0.2570.420
Good compliance5 (42)0.6140.271
Poor compliance7 (58)0.0150.975
7796235e-8535-4dcb-96ef-6007712a3d70_figure2.gif

Figure 2. Correlation of optimal pressure between manual continuous positive airway pressure (CPAP) titration in the lab and home automatic positive airway pressure (APAP) titration in patients with obstructive sleep apnea.

The equation for predicting an in-lab effective pressure is predicted pressure (cmH2O) = 2 + (0.78* home APAP derived effective pressure).

7796235e-8535-4dcb-96ef-6007712a3d70_figure3.gif

Figure 3. The Bland-Altman plot represents the difference in optimal pressure between manual continuous positive airway pressure (CPAP) titration in the lab and home automatic positive airway pressure (APAP) titration in patients with obstructive sleep apnea.

The continuous line indicates the mean difference of optimal pressure between CPAP titration in the lab and home APAP titration (-0.428 cmH2O), while the dotted lines indicate 95% confidence intervals (-5.548 to 4.692 cmH2O). SD=standard deviation.

Furthermore, all patients and severe OSA patients with good APAP compliance had higher significant positive correlation than those without good compliance (Table 3). In patients with severe OSA, a predictive equation for the optimal pressure is in-lab PSG (cmH2O) = 4.28 + (0.64 ⁎ home APAP derived effective pressure) (Figure 4). In OSA patients with good compliance, a predictive equation for the optimal pressure is in-lab PSG (cmH2O) = 1.49 + (0.83* home APAP derived effective pressure) (Figure 5).

7796235e-8535-4dcb-96ef-6007712a3d70_figure4.gif

Figure 4. Correlation of optimal pressure between manual continuous positive airway pressure (CPAP) titration in the lab and home automatic positive airway pressure (APAP) titration in patients with severe OSA.

The equation for predicting an in-lab effective pressure is predicted pressure (cmH2O) = 4.28 + (0.64* home APAP pressure).

7796235e-8535-4dcb-96ef-6007712a3d70_figure5.gif

Figure 5. Correlation of optimal pressure between manual continuous positive airway pressure (CPAP) titration in the lab and home automatic positive airway pressure (APAP) titration in OSA patients with good compliance.

The equation for predicting an in-lab effective pressure is predicted pressure (cmH2O) = 1.49 + (0.83* home APAP pressure).

Discussion

This is the first study to determine the relationship of optimal CPAP pressure between in-lab pressure titration and home APAP in Thai patients with OSA. Our results showed that there was moderately positive correlation between the two titration methods with acceptable agreement, particularly for severe OSA patients with good APAP compliance. Also, the difference of mean optimal pressure between two methods was 0.4 cmH2O in our study.

CPAP is a standard, effective treatment for OSA patients.2,4 Conventionally, the optimal pressure for treating OSA is determined by a standard PSG with manual CPAP titration in a laboratory, whether split-night PSG or full-night PSG. The latter is often performed as a follow-up to the first PSG if the optimal pressure hasn't been successfully determined.3 However, this method is time consuming and expensive. Alternatively, automatic titration is recommended instead of manual titration to identify the proper pressure for CPAP treatment in clinical practice, providing the same outcome in less time for less expense.24 Automatic titration is as effective as standard manual titration in improving AHI and somnolence. In addition, automatic titration has the same effect on acceptance and compliance of CPAP treatment as manual titration.24 Therefore, home APAP is an alternative choice for determining the optimal pressure.

In our study, we hypothesized that the difference of optimal pressure between home APAP and in-lab PSG study would not be more than 2 cmH2O. Our results showed an average pressure difference of 0.4 cmH2O between the two methods and a moderately positive correlation (correlation coefficient of 0.47). These findings are consistent with a study by Elshahaat HA, et al6 and Wongsritrang K, et al,18 which found weakly to strongly positive correlations of optimal pressure between in-lab PSG and home APAP with pressure difference ranging from 0.25 to 3.5 cmH2O. It can be observed that as the difference in the optimal pressure increases, the positive correlation between two titrating methods decreases. However, there might be a few limitations of the titrating study for optimal pressure due to differences in sleep position and sleep stages between home APAP and in-lab PSG settings. The optimal pressure obtained by in-lab PSG needs to maintain an AHI less than 5 events per hour and at least 15 minutes of REM sleep in the supine position,22 which might differ from the pressure requirements of home APAP machines due to differences in sleep posture and sleep stage.

Our results showed that the majority of patients had severe OSA (approximately 76%) while moderate and mild OSA accounted for 20% and 4%, respectively. Among patients with severe OSA, there was significant moderately positive correlation (correlation coefficient of 0.45) between the pressure from home APAP and in-lab PSG study. However, there was no significant correlation in patients with mild to moderate OSA. These findings may be explained by the small sample size of this population.

In OSA patients using home APAP with good compliance (approximately 58% of all patients), there was significant moderately positive correlation between the home APAP pressure and the pressure adjusted during the in-lab PSG study (correlation coefficient of 0.586), whereas there was no significant correlation in patients without good compliance. Moreover, there was greater moderately positive correlation in severe OSA patients with good compliance for home APAP, (correlation coefficient of 0.615). These findings indicate that regular home APAP use for OSA patients, especially severe OSA, leads to closer optimal pressure obtained from both titrating methods.

According to some previous studies, the effective pressure obtained by APAP and by in-lab PSG manual titration did not usually differ significantly.4,612,18,19,25 However, some studies did show differences in optimal pressures between them,1417 with the pressure obtained from an APAP being about 2.5 cmH2O higher than that obtained from in-lab PSG manual titration.16 In contrast, some studies found that the pressure obtained from in-lab PSG manual titration was higher than that obtained from APAP.14,17

When focusing on the compliance of CPAP use, some studies found that APAP had better compliance than manual CPAP,4,12,25 with APAP used 11 statistically significant minutes longer than manual CPAP.4,12 However, several studies found no difference in compliance between APAP and manual CPAP.10,12,14,15,26 Fietze I, et al found that APAP was used approximately 48 minutes longer than manual CPAP.10

Clinical outcomes after following APAP or CPAP uses did not differ in quality of life for OSA patients.10,12,17,18 There was also no difference in Epworth sleepiness scale.11,12,14 Moreover, the initial use of APAP improved the quality of sleep.10 Because APAP machines are more expensive than manual CPAP machines, cost should be considered before starting of positive airway pressure treatment.11 Nevertheless, APAP is cost-effective because it saves time and reduces the expense of undergoing pressure analysis.6,8,9,27,28

There are a few limitations in our study. Firstly, the sample size was small, however study results could detect the correlation of the two titrating methods for optimal pressure. Secondly, only one commercial CPAP machine was investigated, therefore study results might not apply to another type of CPAP machine. A larger study with other types of CPAP machine is needed for comparison. Furthermore, the equation for predicting in-lab PSG effective pressure is required to verify the accuracy of the optimal pressure obtained by home APAP.

Conclusions

Home APAP pressure is moderately positively correlated with in-lab PSG effective pressure. The optimum pressures of home APAP agree with in-lab PSG with manual CPAP titration. APAP might be able to determine effective therapeutic pressure for OSA treatment in the sleep laboratory. A large prospective study is needed to verify the accuracy of home APAP effective pressure for OSA patients and to determine the predictive equation for detecting in-lab PSG effective pressure.

Registration

thaiclinicaltrials.org with number TCTR20210331002

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Pugongchai A, Leelasittikul K and Saiphoklang N. Correlation of therapeutic pressure between home automatic positive airway pressure and in laboratory polysomnography manual titration in patients with obstructive sleep apnea [version 1; peer review: 1 approved with reservations, 1 not approved]. F1000Research 2024, 13:699 (https://doi.org/10.12688/f1000research.144758.1)
NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article.
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Reviewer Report 06 Feb 2025
Krishna Sundar, Division of Pulmonary and Critical Care Medicine,, The University of Utah, Salt Lake City, Utah, USA 
Katyayini Aribindi, University of California Davis School of Medicine (Ringgold ID: 12218), Sacramento, California, USA 
Not Approved
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This study looked at effective CPAP pressures for managing OSA in 55 patients seen at Thammasat University Hospital, Thailand that underwent split night PSG and then were placed on AutoPAP Resmed S10 for 2 weeks. The PAP pressure obtained from ... Continue reading
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Sundar K and Aribindi K. Reviewer Report For: Correlation of therapeutic pressure between home automatic positive airway pressure and in laboratory polysomnography manual titration in patients with obstructive sleep apnea [version 1; peer review: 1 approved with reservations, 1 not approved]. F1000Research 2024, 13:699 (https://doi.org/10.5256/f1000research.158598.r356153)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
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Reviewer Report 23 Aug 2024
Matthew Rahimi, Sleep group, Woolcock Institute of Medical Research (Ringgold ID: 104349), Macquarie Park, New South Wales, Australia 
Fraser Lowrie, Faculty of Medicine and Health, The University of Sydney (Ringgold ID: 4334), Sydney, New South Wales, Australia 
Approved with Reservations
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Title: Correlation of therapeutic pressure between home automatic positive airway pressure and in laboratory polysomnography manual titration in patients with obstructive sleep apnea

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Rahimi M and Lowrie F. Reviewer Report For: Correlation of therapeutic pressure between home automatic positive airway pressure and in laboratory polysomnography manual titration in patients with obstructive sleep apnea [version 1; peer review: 1 approved with reservations, 1 not approved]. F1000Research 2024, 13:699 (https://doi.org/10.5256/f1000research.158598.r313793)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.

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Alongside their report, reviewers assign a status to the article:
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Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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