Clinical estimation of mouth breathing

Introduction: Breathing mode was objectively determined by monitoring airflow through the mouth, measuring nasal resistance and lip-seal function, and collecting information via questionnaire on the patient's etiology and symptoms of mouth breathing. Methods: The expiratory airflow through the mouth was detected with a carbon dioxide sensor for 30 minutes at rest. Fifteen men and 19 women volunteers (mean age, 22.4 +/- 6 2.5 years) were classified as nasal breathers, complete mouth breathers, or partial mouth breathers based on the mean duration of mouth breathing. Nasal resistance, lip-sealing function, and the subjective symptoms of mouth breathing ascertained by questionnaire were statistically compared by using 1-way and 2-way analysis of variance (ANOVA) and the chi-square test in the breathing groups. Results: Nasal resistance was significantly (P<0.05) greater for the mouth breathers than for the nasal breathers, and significantly (P<0.05) greater for the partial mouth breathers than for the complete mouth breathers. There were no significant differences in the subjective responses to questions about mouth breathing among the 3 groups. Conclusions: Detecting airflow by carbon dioxide sensor can discriminate breathing mode. Degree of nasal resistance and subjective symptoms of mouth breathing do not accurately predict breathing mode. (Am J Orthod Dentofacial Orthop 2009;136:630.e1-630.e7)