Mouth breathing

Mouth breathing is habitual or obligatory breathing through the mouth rather than the nose. Nasal obstruction is the commonest cause, especially adenoidal hypertrophy and rhinitis in children. Long term mouth breathing in children affects facial growth, dental occlusion, sleep and behaviour.

Anatomy and physiology. Nasal breathing filters, warms and humidifies air and promotes normal facial growth and nasal nitric oxide production. Mouth breathing bypasses these functions and alters tongue and jaw posture.

Classification. Obstructive (nasal or nasopharyngeal blockage), habitual (persists after relief of obstruction), and anatomical (short upper lip, craniofacial anomaly).

Key distinctions. Mouth breathing with snoring, witnessed apnoea or poor concentration suggests obstructive sleep apnoea. A unilateral cause (foreign body, choanal atresia, tumour) needs separate attention.

History. Duration, day and night pattern, snoring, witnessed apnoea, restless sleep, bedwetting, morning headache, daytime sleepiness, behaviour and school performance, nasal obstruction, discharge, sneezing, itch, smell, speech (hyponasal), dry mouth, halitosis, sore throat, ear problems (glue ear), poor feeding or growth in infants, thumb sucking, and family history of atopy.

Examination. Open mouth posture, lip incompetence, adenoid facies (long face, open bite, high arched palate, narrow maxilla, dark circles under the eyes), nasal airway (mucosa, turbinates, septum, polyps), allergic salute, Cottle manoeuvre, tonsil size (Brodsky grade), oropharynx, dentition and occlusion (crossbite, overjet, crowding), ears (effusion), speech quality, growth parameters, and cardiorespiratory signs.

Red flags

• Apnoeas, cyanosis, failure to thrive, or neurobehavioural problems
• Neonate or infant with obstruction on feeding, cyclical cyanosis relieved by crying (choanal atresia)
• Unilateral obstruction with discharge or bleeding (foreign body, tumour)
• Craniofacial anomaly or syndromic features
• Hearing loss and recurrent effusion
• Pulmonary hypertension or heart failure signs

Special groups. Children: adenoidal hypertrophy and allergic rhinitis. Pregnancy: rhinitis of pregnancy. Older adults: septal deviation, rhinitis and sleep apnoea.

Obstructive

• Adenoidal hypertrophy, tonsillar hypertrophy
• Allergic and non-allergic rhinitis, chronic rhinosinusitis, nasal polyps
• Septal deviation, turbinate hypertrophy, nasal valve collapse
• Choanal atresia and stenosis, foreign body, rhinolith
• Nasopharyngeal mass (angiofibroma, carcinoma, lymphoma, cyst)
• Macroglossia and micrognathia (craniofacial syndromes)

Habitual and functional

• Habitual mouth breathing after relief of obstruction
• Short upper lip, lip incompetence, tongue tie, neuromuscular hypotonia (Down syndrome, cerebral palsy)

Sleep disordered breathing

• Obstructive sleep apnoea, primary snoring, upper airway resistance syndrome

Reasoning. Look for nasal and nasopharyngeal obstruction, test for allergy, and assess sleep disordered breathing when symptoms suggest it.

First line. Nasal examination and endoscopy, tonsil grading, and growth assessment.

Targeted tests:

• Flexible nasendoscopy to assess adenoid size.
• Lateral neck radiograph for adenoid size when endoscopy is not tolerated.
• Skin prick tests or specific IgE for suspected allergy.
• Audiometry and tympanometry for suspected effusion.
• Polysomnography or overnight oximetry for suspected obstructive sleep apnoea (apnoea hypopnoea index over 1 event each hour in children is abnormal; 5 or more in adults is abnormal).
• Orthodontic and cephalometric assessment.
• CT or MRI for suspected mass or choanal atresia (CT with fine cuts), and genetic testing for syndromes.

Limitations. Adenoid size on endoscopy does not predict symptoms. Home sleep tests are less reliable in children.

Allergic and non-allergic rhinitis. Mometasone 50 micrograms, 2 sprays to each nostril once daily (children 3 to 11 years: 1 spray to each nostril once daily), loratadine 10 mg orally once daily (children 2 to 11 years: 5 mg once daily if weight 30 kg or less, 10 mg if over 30 kg), saline irrigation, and allergen avoidance.

Adenoidal and tonsillar hypertrophy. Intranasal corticosteroid for 6 to 12 weeks, and montelukast 4 mg orally at night (age 2 to 5 years) or 5 mg (age 6 to 14 years) for mild sleep disordered breathing. Adenotonsillectomy for moderate to severe obstructive sleep apnoea, recurrent infection or persisting obstruction.

Nasal structural problems. Septoplasty and turbinate surgery by ENT in adults and selected adolescents.

Choanal atresia. Neonatal airway emergency: oral airway, then surgical repair by ENT.

Foreign body. Immediate removal.

Habitual mouth breathing after relief of obstruction. Myofunctional therapy and speech therapy, orthodontic management (rapid maxillary expansion), and lip seal training.

Obstructive sleep apnoea in adults. Weight reduction, avoidance of alcohol and sedatives, positional therapy, continuous positive airway pressure for moderate to severe disease, and mandibular advancement devices.

Monitoring. Review at 6 to 12 weeks after treatment. Growth, school performance and sleep symptoms in children. Dental and orthodontic review.

Referral and escalation. ENT for adenoidal hypertrophy and structural disease. Paediatric sleep service for suspected obstructive sleep apnoea. Orthodontics for occlusal problems. Immediate ENT for neonatal obstruction.

Admission criteria. Severe obstructive sleep apnoea with respiratory compromise, neonatal choanal atresia, or airway obstruction.

Discharge and safety netting. Return for pauses in breathing, cyanosis, poor feeding, noisy breathing, daytime sleepiness, worsening snoring, or persistent obstruction despite treatment.