Table 5.

Respiratory mechanisms: subcategories, characteristics, and triggers.

Author(s), year	Subcategories	Associated characteristics	Potential triggers
Gillespie et al. (2013, 2015)	CO2-based (disruption in gas-exchange balance)	Disrupted respiratory pattern (i.e., breath holding) Disruption in O2/CO2 homeostasis	Anxiety, perceived stress, lower airway disease (e.g., asthma, COPD), URI
Desjardins et al. (2021); Koufman & Blalock (1988); Lowell et al. (2008, 2020)	Disruption in respiratory dynamics: phonatory lung volume	Small tidal volume (“shallow breathing,” “chest breathing”) Speaking at low lung volume (use of functional residual capacity) Lack of increase in lung volume initiation during loud speaking	Viral laryngitis, URI, vocal demands (e.g., increased loudness), acute anxiety
Cryns et al. (2021); Morrison & Rammage (1993); Rubin et al. (2011)	Disruption in respiratory dynamics: control of respiratory muscles	Uncontrolled bursts of airflow Disrupted ratio of transverse abdominis and internal oblique muscles activity Sustained contraction of the SCM muscle	Body position, vocal genre (for singers), vocal technique

Note. COPD = chronic obstructive pulmonary disease; URI = upper respiratory infection; SCM = sternocleidomastoid.