Abstract
BackgroundTotal laryngectomy (TL) is standard intervention for carcinoma of the head and neck or, in cases of non-functional larynx, as a result of disease or radiation exposure. Laryngeal extirpation serves as a unique human model of both recurrent and superior laryngeal nerve section and offers insight into motor and sensory aspects of cough: both volitional and in response to tussigenic stimuli. While motor changes in cough function are expected among those status post-TL due to postoperative reconstruction of the upper airway, motor cough parameters have not been well described and sensory aspects of cough are unknown in this population, which provides insight into a vagal denervation model in humans.MethodsData were collected from three groups totaling 80 adults (39 male), including 25 healthy younger adults (HYA), 27 healthy older adults (HOA), and 28 adults post-TL. Cough was elicited both upon command and in response to nebulized capsaicin. Outcome measures included urge to cough and cough airflows.ResultsKruskal–Wallis test showed that two of the three groups differed significantly by urge to cough χ2(2, N = 244) = 8.974, p = 0.011. Post hoc analysis showed that post-TL subjects had reduced perceived urge to cough at all concentrations of capsaicin (p < 0.05). Cough airflows were significantly reduced for post-TL subjects compared to healthy controls in all metrics except post-peak phase integral (PPPI) for which HOA and TLs were comparable under both volitional and capsaicin-induced conditions.ConclusionsThese findings support the hypothesis that both cough airflow and sensations are significantly reduced in post-TL subjects when compared with HOA. Interestingly, HOA and post-TL subjects have comparably reduced UTC and cough airflows when compared to HYA. The only metric of cough airflow for which these groups differ is the PPPI, which may be a compensatory adaptation for reduced cough airflows and/or sensation.
Highlights
Laryngeal neuropathy has been implicated in several conditions with deleterious effects on speech, swallow, and cough
Cough thresholds reported far have been based on cough response to lowest fog output capable of evoking at least one cough during two distinct challenges separated by a 30-min time interval and are dissimilar from urge to cough, which can be elicited at thresholds lower than that required for motoric cough response
Descriptive statistics showed that median urge to cough increased in response to increase in concentration and at 100 μM healthy younger adults (HYA) reported median (±SD) urge as “somewhat severe” (4 ± 2) while both healthy older adults (HOA) and the total laryngectomy (TL) group reported “very slight” urge to cough (1 ± 3 and 1 ± 2, respectively) (Table 3)
Summary
Laryngeal neuropathy has been implicated in several conditions with deleterious effects on speech, swallow, and cough. Stockwell et al (1993) found that cough elicited by mechanostimulation of laryngeal mucosa was abolished following lidocaine ablation of the SLN but that cough thresholds in response to chemostimulation (e.g., citric acid) were comparable to those with intact SLN input This was elaborated upon by Fontana et al (1999, 2002) who found reduced cough volume acceleration (CVA) due to reduced peak expiratory flow rise times (PEFRT; Figure 1) and comparable cough thresholds in response to nebulized fog inhalation in post-total laryngectomy (TL) subjects and those with Parkinson’s disease, which have been shown to be reduced as compared to healthy controls (Leow et al, 2012; Troche et al, 2014). While motor changes in cough function are expected among those status post-TL due to postoperative reconstruction of the upper airway, motor cough parameters have not been well described and sensory aspects of cough are unknown in this population, which provides insight into a vagal denervation model in humans
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