Effects of Soft Cervical Collar on Apnea-Hypopnea Index in Patients with Obstructive Sleep Apnea

Introduction

CLINICAL IMPACT AND CHALLENGES IN MANAGEMENT:

OSA is strongly linked to hypertension, atrial fibrillation, insulin resistance, stroke, and increased mortality [6]. The criterion standard treatment for moderate-to-severe OSA is continuous positive airway pressure (CPAP) therapy, which effectively reduces respiratory events, improves oxygenation, and alleviates daytime sleepiness [7]. However, CPAP adherence remains a challenge, with up to 50% of patients discontinuing therapy within the first year due to discomfort, air leaks, or intolerance [8].

Alternative therapies, including mandibular advancement devices (MADs), positional therapy, weight loss interventions, hypoglossal nerve stimulation, and surgical procedures, have been explored to improve patient adherence and treatment effectiveness [9].

Neck collars, also referred to as cervical collars, serve a crucial role in the management of spinal injuries, particularly those impacting the neck. These medical devices are designed to provide support and immobilization to the cervical spine, effectively restricting movement and minimizing the risk of further injury. Typically, these collars encircle the neck and extend down the upper spine, offering stability to the injured area. In some instances, collars are worn continuously, while in others, they may be used intermittently as part of a rehabilitation process [10].

RATIONALE FOR THE STUDY:

Recent studies suggest that cervical collars can help stabilize the upper airway, particularly in patients with positional OSA or persistent apneas despite CPAP therapy [8]. By providing anterior support to the neck, a soft cervical collar can help prevent excessive airway collapse during sleep.

This study aimed to evaluate whether a soft cervical collar could reduce AHI and improve oxygen saturation in patients with OSA. By providing anterior airway support, a cervical collar can serve as an alternative or adjunctive treatment, particularly for patients who struggle with CPAP adherence.

Material and Methods

ETHICAL APPROVAL AND PATIENT CONSENT:

This study was designed as a prospective, single-center clinical study to evaluate the effects of a soft cervical collar on apnea-hypopnea index (AHI) and oxygenation parameters in patients diagnosed with obstructive sleep apnea (OSA). The study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki and received approval from the Van Yüzüncü Yıl University Clinical Research Ethics Committee (Approval Date: 20.09.2023/04, Decision Number B.30.2.YYU.0.0.00.00/11. Written informed consent was obtained from all participants before their inclusion in the study.

PATIENT SELECTION AND STUDY POPULATION:

The study initially included 40 adult patients diagnosed with OSA based on polysomnography (PSG) findings. However, 6 patients were excluded: 4 patients were unable to tolerate the cervical collar during sleep, and 2 patients had incomplete or insufficient PSG recordings. Thus, the final sample size was 34 patients.

Inclusion criteria: age ≥18 years, diagnosis of OSA based on an apnea-hypopnea index (AHI) ≥15 events/hour, no prior history of upper airway surgery or other sleep disorders, and no history of neuromuscular disease or cervical spine pathology that might interfere with collar usage. Exclusion criteria: presence of anatomical abnormalities (eg, severe retrognathia, tonsillar hypertrophy), using oral appliances or positional therapy before the study, cardiopulmonary diseases or any condition that could affect sleep architecture or oxygenation, and BMI >40 kg/m² (severe obesity).

STUDY PROTOCOL:

Baseline Sleep Study and Polysomnography (PSG): All participants underwent an overnight in-laboratory polysomnography (PSG) using a 16-channel Embla^® N7000 (Medcare, Reykjavik, Iceland) sleep monitoring system. PSG was performed in accordance with the American Academy of Sleep Medicine (AASM) guidelines (2020, Version 2.6), and the following physiological parameters were recorded:

The Apnea-Hypopnea Index (AHI) was calculated based on the number of apnea and hypopnea events per hour of sleep, following AASM criteria: Apnea: ≥90% reduction in airflow for ≥10 sec. Hypopnea: ≥30% reduction in airflow for ≥10 sec, associated with ≥3% oxygen desaturation or arousal.

SOFT CERVICAL COLLAR APPLICATION:

On the second night, participants underwent a 2-hour intervention using a soft cervical collar. The soft cervical collar used in this study was the Case-Nelson® soft cervical collar, which is a lightweight, foam-based orthopedic device designed to provide mild anterior support to the neck while allowing controlled movement. This collar was selected due to its comfortable fit, adjustability, and ability to prevent excessive neck flexion, which can contribute to airway stabilization in patients with OSA. The collar was fitted by a trained sleep technician to ensure proper positioning and comfort during the intervention. Patients were instructed to maintain a supine sleeping position during the intervention to assess its effects on apnea-hypopnea index (AHI) and oxygen saturation levels. Throughout the intervention, polysomnography (PSG) was continuously performed, recording electroencephalography (EEG), electrooculography (EOG), electromyography (EMG), nasal airflow, respiratory effort (thoracoabdominal movements), and oxygen saturation (SpO2) using pulse oximetry. After 2 hours, the cervical collar was removed, and patients underwent standard positive airway pressure (PAP) titration for the remainder of the night. The application of the soft cervical collar is illustrated in Figure 1, showing both frontal and lateral views of a patient undergoing PSG while wearing the device. Figure 1A demonstrates the overall setup, including electrode placement for PSG, while Figure 1B illustrates the cervical collar’s positioning and fit around the neck.

During this period, patients were instructed to maintain a supine sleeping position PSG monitoring continued to evaluate real-time changes in AHI, SpO₂, and sleep parameters with the cervical collar. After 2 hours, the cervical collar was removed, and patients underwent standard positive airway pressure (PAP) titration for the remainder of the night.

OUTCOME MEASURES AND DATA COLLECTION:

Primary and secondary outcome measures were analyzed, including:

Primary outcomes:

Secondary outcomes:

All data were reviewed by 2 independent sleep specialists who were blinded to the study conditions to ensure objective evaluation.

STATISTICAL ANALYSIS:

Sample size calculation was performed using G*Power (Version 3.1.9.7). Based on an α=0.05, effect size=0.5, and power=80%, a minimum of 34 participants was required. Data normality was assessed using the Shapiro-Wilk test. Since the dataset was not normally distributed, non-parametric tests were used. Comparisons between PSG, cervical collar, and CPAP titration were performed using the Friedman test. Pairwise comparisons were conducted using Bonferroni-corrected Wilcoxon signed-rank tests. Statistical significance was set at p<0.05. All statistical analyses were performed using IBM SPSS Statistics (version 26.0, IBM Corp., Armonk, NY, USA).

Results

BASELINE CHARACTERISTICS OF PARTICIPANTS:

The demographic characteristics of the participants are detailed in Table 1. Out of the initial 40 participants, 4 were excluded due to inability to sleep with the cervical collar, and 2 were excluded due to incomplete overnight polysomnography (PSG) data. Thus, the final analysis included 34 patients, of whom only 4 were female. The mean age of the participants was 44.91±11.32 years. The mean body mass index (BMI) was 29.72±4.19 kg/m2.

EFFECTS OF THE SOFT CERVICAL COLLAR AND CPAP ON APNEA-HYPOPNEA INDEX (AHI):

Table 2 presents the AHI data collected during overnight PSG, cervical collar usage, and CPAP titration. The mean AHI during overnight PSG was 44.44±26.3 events/hour. With the use of a cervical collar, AHI decreased to 36.69±37.48 events/hour, but this difference was not statistically significant. With CPAP titration, AHI significantly decreased to 10.91±30.13 events/hour (p<0.05).

EFFECTS OF THE SOFT CERVICAL COLLAR AND CPAP ON OXYGEN SATURATION:

The impact of cervical collar usage and CPAP titration on oxygen saturation levels is summarized in Table 2.

MEAN OXYGEN SATURATION:

The mean oxygen saturation during overnight PSG was 89.16±3.17%. With the cervical collar, it increased to 89.92±2.22%, but this difference was not statistically significant. With CPAP titration, the mean oxygen saturation increased to 91.16±1.83%, and this difference was statistically significant (p<0.05).

LOWEST OXYGEN SATURATION:

The lowest oxygen saturation during overnight PSG was 76.35±10.26%. With the cervical collar, it increased to 83.74±5.02% (p<0.05). With CPAP titration, it was 83.24±13.76% (p<0.05). Both treatments showed significant improvement compared to PSG.

SLEEP DURATION AND DESATURATION TIME:

Patients wearing a cervical collar slept for an average of 112.79 minutes. During CPAP titration, they slept for an average of 285.85 minutes. Individual hourly desaturation times below 90% were calculated: Overnight PSG: 5.67±6.01 min/hour, Cervical Collar: 6.42 min/hour, CPAP titration: 4.53±9.08 min/hour. The difference between desaturation times per hour during PSG and CPAP titration was statistically significant (p<0.05).

SUBGROUP ANALYSIS: EFFECT OF BMI ON OUTCOMES:

A subgroup analysis focusing on individuals with a BMI below 30 revealed statistically significant differences between overnight PSG and cervical collar use. Significant differences were observed in AHI scores, mean oxygen saturation, and lowest oxygen saturation levels (Table 3). Additionally, comprehensive data for all patients are provided in Table 4.

Discussion

COMPARISON WITH PREVIOUS STUDIES:

Our findings align with previous research investigating the role of cervical collars in OSA management. Prigent et al (2017) demonstrated that a cervical collar reduced persistent apneas in patients who continued to experience obstructive events despite continuous positive airway pressure (CPAP) therapy, suggesting that it can serve as an adjunctive intervention [8]. Similarly, Bordier et al (2021) conducted a pilot study examining the efficacy of soft cervical collars in OSA patients. Their results indicated that a cervical collar could reduce AHI by stabilizing the upper airway, particularly in positional OSA cases [9]. These findings support the hypothesis that cervical collars can be beneficial in selected OSA patients, particularly those who have difficulties tolerating CPAP therapy or exhibit positional-dependent airway obstruction. However, larger studies are needed to confirm the long-term effectiveness and adherence to cervical collar use.

OSA TREATMENT AND CPAP THERAPY:

CPAP remains the criterion standard treatment for moderate-to-severe OSA, as it significantly reduces AHI, improves oxygenation, and enhances sleep quality. Studies have demonstrated that CPAP therapy alleviates daytime sleepiness, reduces cardiovascular risk, and lowers motor vehicle accident rates [1]. However, adherence to CPAP remains a challenge, with up to 50% of patients discontinuing therapy due to discomfort, nasal congestion, or claustrophobia [4]. As a result, alternative therapies such as mandibular advancement devices (MADs), positional therapy, weight loss, and upper airway stimulation have been explored [11]. In our study, the cervical collar led to statistically significant AHI reductions in the BMI <30 subgroup, indicating that it could be an adjunctive option for select patients.

OBESITY AND ITS IMPACT ON OSA:

OSA is highly prevalent in overweight and obese individuals, and obesity is a major risk factor for OSA progression. The Wisconsin Sleep Cohort Study found that a 10% weight gain increased AHI by 32%, while a 10% weight loss reduced AHI by 26% [3]. As a result, weight loss interventions are consistently recommended for patients with OSA, even though they rarely lead to complete disease resolution [12].

In our study, the significant AHI reduction observed in patients with BMI <30 kg/m² aligns with findings that suggest anatomical airway stability is better preserved in non-obese individuals. This highlights the potential role of cervical collars in non-obese OSA patients.

POSITIONAL OSA AND POTENTIAL ROLE OF CERVICAL COLLARS:

Positional OSA (POSA) is a subtype of OSA where respiratory events occur predominantly in the supine position. Large retrospective studies indicate that POSA is present in over 50% of OSA patients, with 20% experiencing events exclusively in the supine position (e-POSA) [13]. Patients with POSA often have lower adherence to CPAP therapy, and positional therapy devices have been developed to prevent supine sleeping [11]. Meta-analyses have confirmed that positional therapy reduces AHI, although its effectiveness is generally lower compared to CPAP [14]. Given that cervical collars can alter head position and prevent airway collapse, future studies should investigate their effectiveness specifically in POSA patients.

ALTERNATIVE THERAPIES BEYOND CPAP:

Apart from CPAP, other emerging therapies such as hypoglossal nerve stimulation (HSN), upper airway stimulation (UAS), oral appliances, nasal expiratory positive airway pressure (EPAP), and myofunctional therapy have gained attention [15]. HSN is recommended for patients who cannot tolerate CPAP, provided they meet eligibility criteria, including AHI 15–65 events/hour, BMI <35 kg/m2, and absence of complete concentric palatal collapse [16]. Studies have demonstrated consistent efficacy and high adherence with HSN therapy [17].

Additionally, oronasal CPAP masks have been associated with higher CPAP pressures, residual AHI, and lower adherence compared to nasal masks [18]. Optimizing mask selection and considering alternative treatment modalities remain crucial in OSA management.

Oral appliances (OAm) have been validated as effective in OSA management, offering comparable health outcomes to CPAP, despite CPAP’s superior AHI reduction. This equivalence is largely due to better adherence rates with OAm. Technological advancements, such as remotely controlled mandibular positioners and adherence monitoring, enhance OAm effectiveness and patient selection. Ongoing improvements in device design and treatment monitoring may establish OAm as a viable first-line alternative to CPAP therapy [19].

LIMITATIONS OF THE STUDY:

This study has several limitations:

Conclusions

While CPAP remains the criterion standard for OSA treatment, our findings suggest that a soft cervical collar can serve as an adjunctive option, particularly in patients with BMI <30 kg/m2 or those with positional OSA. Future long-term studies are necessary to determine the optimal patient profile for cervical collar use and to evaluate adherence and long-term efficacy.

Data Availability Statement

The data used in this study are available upon request from the corresponding author. Restrictions apply to the availability of these data, which were used under license for this study.