Influence of obligatory mouth breathing, during realistic activities, on voice measures.

OBJECTIVE: Low humidity environments and mouth breathing may contribute to superficial vocal fold dehydration. The purpose of this study was to investigate the effects of obligatory mouth breathing, during daily activities in low- and high-humidity environments, on voice measures. The activities included 15 minutes of obligatory mouth breathing alone, during loud reading and during exercise. The effects of mouth breathing and humidity were compared in subjects who either reported or did not report vocal worsening after heavy voice use.

STUDY DESIGN: Prospective, between-group, repeated-measures design.

METHODS: Sixty-three healthy adults with normal respiratory function and perceptually normal voice participated in this study. Thirty-one subjects reported symptoms of voice worsening with heavy voice use. Thirty-two subjects who did not report these symptoms participated as controls. Phonation threshold pressure and perceived phonatory effort were measured at baseline and after each obligatory mouth breathing challenge. Ambient humidity was set to either low or high humidity.

RESULTS: Obligatory mouth breathing in loud reading and exercise significantly increased phonation threshold pressure when compared with mouth breathing alone. This increase in phonation threshold pressure was observed at low and high humidity, in both subject groups. There were no significant effects for perceived phonatory effort.

CONCLUSIONS: Obligatory mouth breathing during loud reading and exercise negatively impact phonation threshold pressure. Future investigations that include longer challenge durations, and subjects with voice disorders, are needed to elucidate the underlying mechanisms for increases in phonation threshold pressure.