Introduction

Although phonatory glottal posture and airflow pulse shape affect voice quality, studies to date have been limited by visualization of vocal fold (VF) vibration from a superior view. We performed a 3D reconstruction of VF vibratory motion during phonation from a medial view and assessed the glottal volume waveform and resulting acoustics as a function of neuromuscular stimulation.

Study design

In vivo canine hemilarynx phonation.

Methods

Across 121 unique combinations of the superior laryngeal nerve (SLN) and recurrent laryngeal nerve (RLN) stimulation, the hemilarynx was excited to the oscillation with airflow. VF medial surface reference points were tracked on high-speed video, mapped into 3D space, and surface shape was restored using cubic spline interpolation. Glottal surface shape, reconstruction-based parameters, and glottal volume waveform were calculated. Fundamental frequency (F0), cepstral peak prominence (CPP), and harmonic amplitude (H1-H2) were measured from high-quality audio samples.

Results

The glottis was convergent during opening and divergent during closing. Neuromuscular activation changed phonatory glottal shape and reduced glottal volume. Significant reduction in glottal volume and closing quotient were present with SLN stimulation. RLN stimulation significantly increased F0 and CPP and decreased H1-H2 (constricted glottis), while SLN effects were similar and synergistic with concurrent RLN stimulation.

Conclusion

3D reconstruction of in vivo medial surface vibration revealed effects of laryngeal nerve stimulation on glottal vibratory pattern and acoustic correlates of voice quality. SLN activation resulted in significantly quicker glottal closure per cycle, decreased glottal volume, and higher-pitched, less breathy, and less noisy voice. RLN had a similar effect on acoustic measures.

Level of evidence

NA, Basic Science Laryngoscope, 133:357-365, 2023.

South Asians in the United States have disproportionately high burden of cardiovascular disease compared to other race/ethnic groups but are a heterogenous population, so we evaluated differences in prevalence and adjusted odds of cardiovascular risk factors including diabetes, hypertension, dyslipidemia, and obesity between North Indian, South Indian, and Pakistani immigrants in the United States in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study. Given cultural differences among residents of Indian regions, for example in dietary patterns, we categorized Indian participants as North or South Indian. In 1,018 participants (728 North Indian [47% women], 223 South Indian [43% women], 67 Pakistani [52% women]), unadjusted diabetes and obesity prevalence was highest in Pakistani participants (33% and 48%, respectively); hypertension prevalence was highest in North Indian participants (54%); dyslipidemia prevalence was highest in South Indian and Pakistani participants (55%); and South Indian participants had a higher odds of dyslipidemia (OR 1.77, 95% CI 1.27, 2.47) compared with North Indian participants in fully adjusted models. As differences in cardiovascular risk factors were observed across South Asian American subgroups, identifying the determinants of suboptimal cardiovascular health within South Asian American subgroups may help to better tailor cardiovascular disease prevention strategies.