Mouth Closure and Airflow in Patients With Obstructive Sleep Apnea

Journal Article 1 Mention

Hyung Chae Yang•2024

Phillip HuyettTsai-Yu Wang

Top 4% · 96th Percentile

23 citations · Physiology

Open Access

TLDR

Closing the mouth improved breathing for many people with sleep apnea, but it made breathing worse for those who mainly breathed through their mouth. Treatment should therefore be tailored to each person.

Summary

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1 Study Aim

The authors investigated whether mouth breathing provides an important backup route in obstructive sleep apnea (repeated breathing interruptions caused by a blocked upper airway). They examined how closing the mouth changes breathing and whether velopharyngeal obstruction ( blockage near the soft palate and upper throat) affects the result. Closing the mouth does not help everyone with sleep apnea, especially people who rely heavily on mouth breathing.

2 Study Design

This nonrandomized clinical trial studied 66 patients with obstructive sleep apnea during drug-induced sleep endoscopy, which examines the airway while medication simulates sleep. Twelve patients lacked enough starting airflow, leaving 54 for analysis. Researchers grouped participants by oral airflow: nearly none, moderate, or high. They alternated relaxed and closed-mouth breaths by gently pressing the chin until the teeth touched. The main measure was total inspiratory flow, meaning the amount of air entering during breathing. The researchers also assessed whether velopharyngeal obstruction changed the response. The researchers tested mouth closure during simulated sleep in 54 people, comparing results among people with different amounts of mouth breathing.

3 Findings

The study reports that mouth closure increased total inspiratory flow by 27.8 percentage points overall. Results differed according to baseline mouth breathing. Among 10 patients with almost no mouth breathing, closure showed no clear effect. In 32 patients with moderate mouth breathing, closure improved airflow by 2.0 liters per minute. Airflow worsened by 1.9 liters per minute in patients with high mouth breathing. Velopharyngeal obstruction was linked with more mouth breathing and reduced airflow after closure. The authors recommend personalized approaches rather than routine mouth closure for every patient. Closing the mouth often helped, but it harmed breathing for people who depended on mouth breathing, especially when the upper throat was blocked.

Abstract

Importance: Mouth breathing is associated with increased airway resistance, pharyngeal collapsibility, and obstructive sleep apnea (OSA) severity. The common belief is that closing the mouth can mitigate the negative effects of mouth breathing during sleep. However, mouth breathing may serve as an essential route to bypassing obstruction along the nasal route (eg, the velopharynx). Objective: To investigate the role of mouth breathing as an essential route in some patients with OSA and its association with upper airway anatomical factors. Design, Setting, and Participants: This nonrandomized clinical trial included participants diagnosed with OSA who underwent drug-induced sleep endoscopy. Patients were stratified into 3 quantiles based on oral-breathing level (quantile 1: oral airflow < 0.05 L/min; quantile 2: oral airflow 0.05-2.2 L/min; quantile 3: oral airflow > 2.2 L/min). Interventions: Closing the mouth during sleep during alternating breaths by applying pressure to the mentum until teeth are in occlusion. Main Outcomes and Measures: The primary outcome was total inspiratory flow defined as the change in airflow in the transition from mouth relaxed to mouth closed, analyzed overall and by 3 oral-breathing quantiles. The association of velopharyngeal obstruction on the change in total inspiratory airflow was also investigated. Results: Of 66 enrolled patients with OSA, 12 were excluded due to insufficient baseline airflow. The analytic cohort consisted of 54 patients (39 [72%] male; median [IQR] age, 55 [46-64] years; apnea-hypopnea index, 26.9 [17.6-39.9] events/h; and body mass index calculated as weight in kilograms divided by height in meters squared, 28.9 [27.1-31.6]). Mouth closure increased total inspiratory flow by 27.8 percentage points overall (β, 1.0 [95% CI, 0.4-1.9] L/min). However, outcomes varied based on the degree of baseline oral breathing. No association was found for 10 patients with near-zero mouth breathing (0.9 [95% CI, -0.2 to 2.1] L/min). Airflow improved with mouth closure in 32 patients with moderate levels of mouth breathing (2.0 [95% CI, 1.3-2.7] L/min), whereas it worsened in patients with high levels of mouth breathing (-1.9 [95% CI, -3.1 to -0.6] L/min). Velopharyngeal obstruction was associated with increased mouth breathing (0.6 [95% CI, 0.1-3.0] L/min) and reduced airflow with mouth closure (-1.9 [95% CI, -3.1 to -0.7] L/min). Conclusion and Relevance: Although mouth closure increased inspiratory airflow in the overall cohort of this nonrandomized clinical trial, the outcomes were heterogeneous. In patients who breathe primarily through their mouth during sleep and have velopharyngeal obstruction, airflow worsens with mouth closure. Hence, personalized approaches to treating mouth breathing should be considered. Trial Registration: ClinicalTrials.gov Identifier: NCT06547658.

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