Subglottal

Subglottal refers to the region of the airway located below the glottis, the opening between the true vocal folds. Anatomically, the subglottal space extends from the inferior margin of the vocal folds to the inferior border of the cricoid cartilage, and it continues as the upper part of the trachea. The space is lined with mucosa and forms part of the laryngeal airway responsible for guiding airflow from the lungs toward the vocal apparatus.

In phonation, subglottal pressure is the air pressure that builds up beneath the vocal folds as air is expelled from the lungs. This pressure provides the driving force that sets the vocal folds into vibration when they come into contact and separate during exhalation. The level of subglottal pressure influences voice onset, loudness, and the quality of phonation, interacting with vocal fold tension, mass, and glottal closure. Higher subglottal pressure generally yields greater loudness and can affect pitch stability and spectral balance.

Measurement and clinical relevance: Subglottal pressure can be estimated indirectly in clinical and research settings by recording intraoral pressure during voiceless plosive consonants, which approximates the pressure beneath the vocal folds during voicing. Abnormal subglottal conditions include subglottic stenosis (narrowing at the subglottic region), which can cause dyspnea and stridor, and other inflammatory or structural disorders affecting airflow. In voice science, subglottal dynamics are studied to understand voice production, pathologies, and optimal vocal techniques.