TABLE I.

Summary of Statistical Comparisons Stratified by Particle Size and Intervention.

	N	1–3 μm		3–5 μm		>5 μm
		Median Difference (Particles/M3)	P Value	Median Difference (Particles/M3)	P Value	Median Difference (Particles/M3)	P Value
Positive controls (relative to background)
Speech	10	−1,761	.838	−3,169	.284	−1,408	.192
Breathing	40	7,774	.016*	0	.700	−353	.763
Phonation with /e/	10	14,437	.126	704	.574	2,817	.153
Phonation with /æ/	10	34,859	.022*	9,507	.083	13,732	.012*
Test interventions
Flexible laryngoscopy (relative to breathing)	10	−3,873	.386	−1,408	.201	1,408	.329
Flexible laryngoscopy with humming (relative to breathing)	10	−352	.386	2,113	.212	−1,056	.550
Flexible laryngoscopy with /e/ sound (relative to /e/ phonation)	10	−8,451	.169	0	.779	−704	.646
Rigid laryngoscopy (relative to breathing)	10	10,915	.475	1,761	.594	3,169	.333
Rigid laryngoscopy with /æ/ sound (relative to /æ/ phonation)	10	−23,592	.013	−9,507	.138	−11,972	.013

Positive values represent higher intervention counts relative to reference, and negative values represent lower intervention counts relative to reference.

^*Significant increase at P < .05.