Could reflex cough induced through nebulized capsaicin achieve airway clearance in patients with acute retention of lung secretions?

Abstract

Nasotracheal suctioning (NTS) is a procedure commonly performed by respiratory physiotherapists and nurses to remove excess respiratory secretions from the tracheobronchial tree in a self-ventilating, non-intubated and non-tracheotomized patient. NTS is an important treatment modality for patients with acute secretion retention who are at high risk of progressive respiratory deterioration and arrest. However, NTS is a blind invasive procedure with risk of serious adverse events, and the patient experience of NTS is often extremely negative. Capsaicin, a substance extracted from cayenne pepper, elicits reflex coughs when inhaled. It is hypothesized that capsaicin-induced reflex cough may offer an alternative treatment option to NTS. It is suggested that repeated reflex cough bouts, elicited through inhalation of nebulized capsaicin via a facemask, could achieve clearance of retained secretions from the tracheobronchial tree to the oropharynx, thereby avoiding the need for NTS. This hypothesis is supported by preliminary cough flow data from a stroke trial. Stroke patients underwent assessments of peak cough flow (PCF, a measure of cough effectiveness) of both maximal volitional cough and capsaicin-induced reflex cough. In a sub-group of 20 stroke patients with weak volitional cough (mean PCF 220 L/min, SD 80), PCF of capsaicin-induced reflex cough was on average 184 L/min (SD 130) higher than PCF of subjects' maximal volitional cough effort. Cough flow traces indicate a pattern of cough augmentation during consecutive reflex cough bouts. It is suggested that the hypothesis may best be tested in a pragmatic applied clinical study, i.e. through the application of nebulized capsaicin in relevant clinical situations, as opposed to observational or experimental physiological studies.

Effect of Capsaicin Atomization–Induced Cough on Sputum Excretion in Tracheotomized Patients After Hemorrhagic Stroke: A Randomized Controlled Trial

“…A study of acute stroke patients showed that capsaicin-induced reflex cough produced a higher maximum PCF than spontaneous cough (Kulnik et al, 2015), indicating that induced reflexive coughing is more effective than spontaneous cough in expelling respiratory secretions. After the cough is induced by capsaicin nebulization, the patient can use the chest wall oscillation and the rapid expiratory airflow produced by the cough to move secretions from the deep small airways into the major airway at once (Kulnik, 2018). Accordingly, the daily sputum output in the intervention group was significantly higher than that in the control group.…”

“…We speculate that this may be related to the disease characteristics of patients with cerebral hemorrhage. Capsaicininduced cough is based on the function of a well-integrated cough reflex pathway (Kulnik, 2018), which could be interrupted if there is a dysfunction at any point in the neural pathways. The cough reflex in stroke patients is compromised because of brain lesions, resulting in decreased cough sensitivity (Hegland et al, 2016;Zhao et al, 2015), and that tracheotomy disrupts the physiology of the airway, further weakening the cough reflex.…”

“…In order to determine the appropriate capsaicin concentration, we conducted an experiment prior to the formal start of the study. Capsaicin solutions of 31.25, 62.5, and 125 μmol/L were prepared for pilot study according to previous studies (Chen et al, 2005;Kulnik, 2018). We conducted experiment based on the methods used in the studies (Chen et al, 2005;Zhao et al, 2015), and the results showed that a cough reflex could be produced in 20% (2/10) of patients at 31.25 μmol/L; 60% (6/10) of patients at 62.5 μmol/L; and 60% (6/10) of patients at 125 μmol/L.…”

“…Therefore, this study was designed to investigate an alternative method to assist coughing in tracheotomized patients with stroke to promote effective sputum elimination. The hypothesis of whether coughing induced by capsaicin can clear respiratory secretions has been proposed by some researchers (Kulnik, 2018) but has not been clinically tested.…”

“…Accordingly, capsaicin nebulization is a more appropriate method to induce cough in tracheotomized patients with hemorrhagic stroke. At present, this method of cough induction is mainly used in cough reflex tests to determine cough peak flow rate, cough sensitivity, and swallowing function in patients, with good validity and reproducibility (Cho et al, 2019;Ferenc et al, 2018;Kulnik, 2018). However, few studies have reported on the use of capsaicin nebulization to stimulate cough and promote sputum excretion in patients.…”