“Effect of a porous oral patch on objective and subjective snoring and sleep”

Journal: Sleep and Breathing, 2015; Volume 19, Pages 861–866

This study involved 30 patients with mild obstructive sleep apnea (OSA) and habitual mouth breathing. The study evaluated the effects of mouth taping—designed to promote nasal breathing during sleep—on snoring, daytime sleepiness, and sleep-disordered breathing. Participants underwent pre- and post-treatment assessments, including overnight polysomnography and subjective symptom scoring.

Key conclusions:

1. Mouth tape significantly improved sleep-disordered breathing. After using mouth tape, the average apnea-hypopnea index (AHI) decreased by 35% (from 12.0 to 7.8 events/hour), indicating a meaningful improvement in breathing stability during sleep.
2. Mouth tape dramatically reduced snoring severity and intensity.
   - ➔ The visual analog scale (VAS) snoring score dropped by 68% (from 7.5 to 2.4).
   - ➔ Objective snoring frequency decreased by 72.7% (from 146.7 to 40.0 events/hour).
   - ➔ Snoring sound intensity was reduced by 16.3% (from 49.1 dB to 41.1 dB).
3. Mouth tape notably improved daytime sleepiness. The Epworth Sleepiness Scale (ESS) score improved by 35.8% (from 8.1 to 5.2), suggesting better sleep quality and reduced fatigue.

Original study

“Effect of nasal or oral breathing route on upper airway resistance during sleep”

Journal: European Respiratory Journal, 2003; Volume 22, Pages 827–832

This randomized, single-blind crossover study involved 12 healthy adults to investigate how the route of breathing (nasal vs. oral) affects upper airway resistance and the occurrence of obstructive sleep apnea (OSA) during sleep. Each participant underwent overnight sleep testing under both nasal and oral breathing conditions, with airflow, resistance, and sleep apnea events carefully monitored.

Key conclusions:

1. Nasal breathing dramatically lowers airway resistance during sleep. Compared to oral breathing, nasal breathing reduced upper airway resistance by 58.1%, highlighting a mechanical advantage for nasal airflow in maintaining an open airway.
2. Nasal breathing nearly eliminates obstructive sleep apnea events. The apnea-hypopnea index (AHI) dropped by 96.5% during nasal breathing (from 43 to 1.5 events/hour), showing nasal breathing is vastly superior in preventing sleep-disordered breathing.by 16.3% (from 49.1 dB to 41.1 dB).
3. These benefits hold across different sleep positions. Nasal breathing reduced AHI by 90.3% in the supine position and 93.1% in the lateral position, indicating that its protective effects are consistent regardless of body position during sleep.

Original study

Nasal breathing plays a crucial role in optimizing respiratory function and supporting a wide array of beneficial physiological processes. While breathing itself is automatic, the route air takes into the body—either nose or mouth—has profound effects on health. The nose actively filters, warms, and humidifies the air we inhale, preparing it for safe and efficient gas exchange in the lungs. Mouth breathing bypasses these protective mechanisms, resulting in drier, cooler, and less filtered air reaching the lower respiratory tract. Nasal breathing is essential for maintaining respiratory efficiency, defending against pathogens, and promoting overall well-being.

The nasal passages are the body's primary entry point for air and serve as an intricate system for conditioning the inhaled air before it reaches the delicate tissues of the lungs.1 This air conditioning process encompasses filtration, warming, and humidification, all of which are essential for maintaining optimal respiratory function.

The nose acts as the first line of defense against airborne particles. The nasal passages are lined with coarse hairs, known as vibrissae, which trap larger particles such as dust.2 Further along the nasal cavity, mucous membranes play a vital role in capturing smaller particles, including dust, pathogens like bacteria and viruses, and allergens.3 This sticky mucus layer prevents these potentially harmful substances from penetrating deeper into the respiratory system. To ensure the continuous removal of trapped particles, the nasal passages are equipped with cilia, tiny hair-like structures that rhythmically beat to propel the mucus, along with the entrapped debris, towards the pharynx where it can be expelled or swallowed.1 This sophisticated filtration mechanism significantly reduces the burden on the lower respiratory system by preventing a multitude of environmental hazards from reaching the lungs.1 In contrast, breathing through the mouth bypasses this essential filtration process, potentially leading to an increased risk of inhaling airborne bacteria, viruses, and other irritants, thereby elevating the likelihood of respiratory infections and irritation.5

The nasal cavity is richly supplied with blood vessels, which play a crucial role in regulating the temperature of inhaled air.1 As air passes through the nose, it comes into close contact with this extensive network of blood vessels, allowing for efficient heat exchange. The inhaled air is warmed to body temperature, typically ranging from 31 to 37°C.2 A countercurrent heat exchange mechanism, involving the sphenopalatine artery, further enhances the efficiency of this warming process.2 This warming of inhaled air is vital as it prevents the respiratory system, particularly the delicate lung tissues, from being exposed to cold air, which can be irritating and potentially damaging.5 Breathing through the mouth, however, delivers cooler air to the lungs, which can cause irritation and may even trigger respiratory issues.5 The efficient warming of inhaled air by the nose, therefore, serves as a protective mechanism against thermal stress, especially crucial in cold environments.1

The nasal passages are also responsible for humidifying inhaled air.1 The vascular nasal mucosa increases the relative humidity of the inhaled air to approximately 95%.1 Mucous membranes lining the nasal cavity release moisture into the passing air, ensuring it is adequately moistened before reaching the lungs.3 This humidification process is essential for preventing dryness and irritation of the respiratory tract 5, maintaining the integrity of the mucous membranes, and facilitating optimal gas exchange in the lungs. The upper airways, including the nasal passages, help conserve humidity during exhalation, transferring moisture from the warm, moist exhaled air back to the cooler, drier inhaled air.3 Mouth breathing leads to drier air entering the lungs, potentially causing discomfort, dry mouth, and throat irritation.5 The role of the nasal passages in humidifying inhaled air is vital for ensuring the delicate tissues of the respiratory system remain moist and functional for effective gas exchange.1

Breathing through the mouth bypasses the nose's natural air conditioning processes of filtration, warming, and humidification.5 This can lead to a cascade of negative consequences, including potentially reduced oxygen intake and overall respiratory inefficiency.5 The absence of the nose's filtering mechanisms in mouth breathing increases the risk of inhaling airborne pathogens, elevating the likelihood of respiratory infections.5 Moreover, the drying effects of mouth breathing can significantly impact oral health, leading to issues such as dry mouth, bad breath, and an increased risk of dental problems.5 The cumulative effect of these bypassed functions underscores the significant advantages of nasal breathing for maintaining respiratory and overall well-being.

The mode of breathing significantly influences the quality of sleep. Scientific evidence indicates that nasal breathing is inherently linked to deeper and more restful sleep through various physiological mechanisms.

Nasal breathing naturally encourages diaphragmatic breathing, a deeper and more efficient form of respiration that engages the diaphragm muscle fully, leading to enhanced oxygen distribution throughout the body.5 Physiologically, nasal breathing is the expected and preferred mode of respiration during sleep.11 Studies have shown that oral (mouth) breathing during sleep is associated with significantly higher upper airway resistance compared to nasal breathing.12 By facilitating smoother airflow and reducing resistance, nasal breathing can also play a crucial role in minimizing snoring by helping to keep the airways open and preventing the vibrations of the soft tissues in the throat.10 The mechanics of nasal breathing, therefore, inherently support deeper and more efficient respiration, which is conducive to a more restful and restorative sleep experience.

The relationship between breathing patterns and sleep apnea is well-documented. Mouth breathing during sleep has been shown to exacerbate sleep apnea, a condition characterized by pauses in breathing during sleep, and can lead to worsened oxygen desaturation, a drop in blood oxygen levels.13 Conversely, nasal obstruction has been identified as a significant risk factor for obstructive sleep apnea (OSA).15 Research suggests that improving nasal breathing can effectively reduce the severity of OSA and may even lower the levels of continuous positive airway pressure (CPAP) required for treatment.18 One emerging method to promote nasal breathing during sleep and potentially improve mild OSA is the use of mouth taping, which gently encourages breathing through the nose by keeping the mouth closed.19 Therefore, prioritizing nasal breathing is a crucial aspect of managing sleep-disordered breathing, and addressing any underlying nasal obstruction can be a key component in the overall treatment strategy for OSA.

The patency of the nasal passages has a direct impact on sleep quality. Nasal congestion, whether due to allergies, illness, or structural issues, has been shown to worsen subjective sleep quality.15 Notably, allergic rhinitis-related nasal congestion significantly increases the likelihood of developing moderate to severe OSA.15 Conversely, treating nasal obstruction, through medication, nasal sprays, or surgical intervention, has been found to improve sleep quality and enhance adherence to PAP therapy for sleep apnea.15 Maintaining clear nasal passages is therefore essential for achieving optimal sleep quality, particularly for individuals who suffer from allergies or sleep apnea.

Habitual mouth breathing, especially during sleep, is associated with a range of disturbances that can negatively impact sleep quality and daytime functioning.21 These disturbances include snoring, which can disrupt sleep for both the individual and their partner, as well as dry mouth and throat, which can lead to discomfort and awakenings.21 Furthermore, mouth breathing has been linked to poor rapid eye movement (REM) sleep, a crucial stage for cognitive and physical restoration.21 Consequently, individuals who habitually breathe through their mouths during sleep may experience increased daytime fatigue, irritability, and difficulties with cognitive functions such as concentration and memory.21

The mode of breathing significantly impacts the efficiency with which the body absorbs oxygen. Scientific evidence indicates that nasal breathing offers several advantages over mouth breathing in terms of oxygen uptake and utilization.

Nasal breathing is generally more efficient for oxygen uptake compared to mouth breathing [5, 52, 5. Studies have shown that consistent nasal breathing can increase arterial oxygen pressure by nearly 10% compared to mouth breathing.65 This improvement is attributed to the fact that the nasal passages filter, warm, and humidify the air, optimizing it for absorption in the lungs.65 The increased resistance to airflow in the nasal passages, compared to the mouth, slows down the rate of breathing and allows for a more complete extraction of oxygen from the inhaled air.13 Some research even suggests that nasal breathing may increase blood oxygen uptake by as much as 18%.13 This enhanced oxygenation through nasal breathing is crucial for maintaining optimal bodily functions.

During physical activity, nasal breathing has been shown to be more efficient. It is estimated to be 22% more efficient than mouth breathing.13 Nasal breathing during aerobic exercise may also improve oxygen uptake efficiency (OUE), particularly at higher intensities.69 Furthermore, nasal breathing can be effective in reducing hyperventilation, which can occur during intense exercise, as indicated by a lower respiratory exchange ratio (RER).71 While mouth breathing might feel like it delivers a greater volume of air, nasal breathing can lead to a more effective use of oxygen, especially during endurance activities.

Breathing through the mouth is generally less efficient for oxygen absorption.21 It can potentially decrease lung function and exacerbate symptoms in individuals with asthma.24 Moreover, mouth breathing can lead to an excessive loss of carbon dioxide, which is essential for the release of oxygen from hemoglobin to the body's cells.40 This imbalance in oxygen and carbon dioxide can hinder the efficient delivery of oxygen to tissues and organs.

Nasal breathing plays a critical role in the production and release of nitric oxide (NO), a molecule with significant effects on various bodily systems.

Nitric oxide is continuously produced in the paranasal sinuses and the nasal cavity.1 This vasodilator gas is released into the nasal airways, especially during nasal breathing, which enhances its supply to the respiratory system.13 The production of NO in the nose is flow-dependent, with higher levels observed during inhalation.78 The nasal passages, therefore, serve as a primary source of this important molecule, and breathing through the nose is essential for its effective delivery.

Nasal nitric oxide exerts numerous beneficial effects on the cardiovascular system. It acts as a potent vasodilator, causing the relaxation and widening of blood vessels, which improves blood flow and circulation throughout the body.6 This vasodilation contributes to lower blood pressure 13 and enhances the uptake and delivery of oxygen to tissues and organs.6 Furthermore, nasal breathing and the associated release of NO have been shown to improve heart rate variability (HRV), an indicator of cardiovascular health and autonomic nervous system function 85, and may also reduce pulmonary vascular resistance.77

Nitric oxide produced during nasal breathing also plays a crucial role in the body's immune defense. It possesses broad antimicrobial properties, acting as antibacterial, antiviral, and antifungal agent.6 NO serves as a first line of defense against airborne pathogens, helping to neutralize harmful microorganisms before they can cause infection.75 Studies suggest that it may help reduce the incidence and severity of respiratory tract infections 107 and has even been shown to inhibit the replication of viruses such as SARS-CoV.79

Beyond its impact on the cardiovascular and immune systems, nasal nitric oxide appears to influence a variety of other physiological processes, including improving respiratory ciliary beat frequency, inhibiting platelet aggregation, and potentially acting as a radical scavenger.78 It is also believed to play a role in respiration itself, enable erectile function, enhance memory and learning, and regulate bladder function.82

A significant drawback of mouth breathing is that it leads to lower levels of nitric oxide within the respiratory tract compared to nasal breathing.107 Some research indicates that mouth breathing can reduce the amount of exhaled nitric oxide by as much as 50%.79 This reduction in NO levels diminishes the numerous benefits associated with this vital molecule, further underscoring the importance of prioritizing nasal breathing.

The way we breathe, particularly during childhood, has a profound influence on the growth and development of the craniofacial structures, including the jawline, cheekbones, and mid-face. Nasal breathing plays a vital role in promoting proper facial development.

Nasal breathing is essential for stimulating the proper growth and development of both the upper and lower jaws, which is fundamental for achieving a healthy smile and a well-proportioned facial structure.25 When breathing occurs through the nose, the tongue naturally rests against the roof of the mouth (the palate). This proper tongue posture exerts a gentle outward pressure that supports the widening and forward growth of the upper jaw, creating sufficient space for the teeth to erupt in proper alignment and preventing issues such as overcrowding.26 This interplay between nasal breathing and correct tongue posture is therefore critical for guiding the healthy development of the facial skeleton, especially the jaws.

In contrast to the positive influence of nasal breathing, chronic mouth breathing, particularly during the critical growth periods of childhood, can lead to a constellation of characteristic facial changes often referred to as "adenoid facies" or "long face syndrome".26 Mouth breathing often results in a backward and downward rotation of the mandible (lower jaw) 42, contributing to an increased lower facial height and a longer, narrower facial appearance. The chronic open mouth posture associated with mouth breathing often leads to lip incompetence, where the lips do not seal properly at rest.55 Furthermore, mouth breathing can contribute to narrower dental arches, increased overjet (the horizontal distance between the upper and lower front teeth), and a higher prevalence of posterior crossbite, where the upper back teeth bite inside the lower back teeth.42 The altered muscle balance resulting from mouth breathing, with the tongue resting in a lower position in the mouth instead of against the palate, disrupts the normal forces that shape the developing face.59 These persistent changes underscore the significant impact of habitual mouth breathing on craniofacial development, often resulting in distinct and recognizable facial and dental abnormalities.

The dental and skeletal changes associated with mouth breathing often necessitate orthodontic intervention to correct malocclusions.55 Orthodontists are increasingly recognizing the importance of early detection of mouth breathing in their patients.61 Addressing mouth breathing through various strategies, such as myofunctional therapy or addressing underlying nasal obstructions, can significantly improve the outcomes of orthodontic treatment by supporting more harmonious facial growth and dental alignment.61 Therefore, orthodontists play a crucial role in identifying and managing mouth breathing to mitigate its potential negative impact on dental and facial development.

Scientific evidence overwhelmingly supports the notion that nasal breathing is the body's natural and optimal mode of respiration, offering a multitude of benefits for overall health and wellness. From its crucial role in conditioning inhaled air to its impact on sleep quality, craniofacial development, oxygen uptake, nitric oxide production, mental well-being, and athletic performance, nasal breathing underpins numerous vital physiological processes.5 Mouth breathing bypasses these beneficial mechanisms and can contribute to various health issues.5

To harness these benefits, individuals can consciously strive to breathe through their nose during both wakefulness and sleep. Practices such as mouth taping, being mindful of breathing patterns, practicing nasal breathing exercises, and addressing any underlying nasal obstructions can significantly improve overall health and quality of life. While mouth breathing may be necessary in certain situations, such as during intense exercise or nasal congestion, making nasal breathing the default mode of respiration is a fundamental step towards optimizing our health and well-being.