Cough reflex sensitivity is decreased in female obese patients with obstructive sleep apnea

Lack of association of impaired upper airway sensation with the presence or absence of obstructive sleep apnoea or chronic rhinosinusitis in World Trade Center responders

OBJECTIVE

Examine sensory function of the upper airway in four groups of subjects recruited from the World Trade Centre General Responder Cohort (WTCGRC), with/without obstructive sleep apnoea (OSA), and with/without chronic rhinosinusitis (CRS).

METHODS

Upper airway sensory function was determined using 2-point discrimination (2-PD) and vibration threshold (VT) in 163 WTCGRC subjects with both OSA and CRS (cases), OSA or CRS alone and without OSA or CRS (controls). Presence of OSA was determined from clinical sleep studies or home sleep testing. Presence of CRS was determined by nasal symptom questionnaire. The relationship between the presence of OSA and CRS and upper airway sensory impairment was assessed using linear regression analysis with each of 2PD and VT sensory threshold values as the dependent variable; OSA, CRS and their interaction were the independent variables. Age, gender and body mass index were covariates in the statistical model. The primary analysis was comparison of OSA+CRS versus controls (no OSA and no CRS) evaluated by linear contrasts.

RESULTS

There were no differences in 2-PD or VT in those with OSA+CRS, OSA and CRS alone or controls. However, both 2-PD and VT were significantly higher in the WTCGRC controls compared with values seen in historical controls using the same methodology (median 2-PD 13.0; CI (11.0 to 13.5) vs 10.5; CI (8 to 11); VT: mean±SEM (9.3±0.6 vs 2.2±0.1)).

CONCLUSION

While no differences were found in upper airway sensation between cases of OSA and CRS versus controls in the WTGRC population, there was evidence of impaired upper airway sensation in the WTGRC overall.

Evaluation methods and influencing factors of cough sensitivity

Increased cough sensitivity is an important mechanism of chronic cough, and the evaluation of cough sensitivity helps understand the mechanism of cough and explore better methods to reduce cough. Evaluation methods may be direct or indirect. Direct methods include mechanical stimulation and chemical stimulation, and indirect methods include laryngeal reflex test, questionnaires, and brain functional magnetic resonance imaging (fMRI). Chemical stimulation is the most common method, while the capsaicin cough challenge test is proven and widely used. In this article, we will compare evaluation methods and explore influencing factors of cough sensitivity.

A systematic review of methods of citric acid cough reflex testing

INTRODUCTION

This systematic review summarises and appraises methods of citric acid cough reflex testing (CRT) documented in published literature.

METHODS

Electronic databases, MEDLINE, EMBASE, CINAHL, PsychINFO, Scopus were searched up to and including 11th February 2018. Studies reporting a method of citric acid CRT, published in peer-reviewed journals in English or Spanish, were assessed for the inclusion criteria. Of the selected studies, information on the instrumentation and CRT protocol was extracted.

RESULTS

A total of 129 studies were included. Instrumentation and protocols differed widely across studies. Reporting of methods of citric acid CRT was sub-standard, with many crucial methodological components omitted from published manuscripts, preventing their full replication.

CONCLUSIONS

Considerable methodological variability exists for citric acid CRT in published literature. The findings suggest that caution is warranted in comparing citric acid cough thresholds across studies. Full replication of previously published methods of citric acid CRT is limited due to crucial elements of the citric acid CRT protocol being omitted from published manuscripts. These findings have implications on the use of citric acid CRT in clinical and pharmaceutical studies to evaluate the effects of antitussive medications and cough therapies.

Cough hypersensitivity in patients with obstructive sleep apnea hypopnea syndrome

PURPOSE

The purpose of this study was to investigate cough hypersensitivity and its potential mechanisms in patients with obstructive sleep apnea hypopnea syndrome (OSAHS).

METHODS

Fifteen OSAHS patients, 12 simple snoring patients, and 15 healthy volunteers received cough sensitivity test and induced sputum cytology. Cough thresholds C2 and C5 (the minimum of capsaicin inducing ≥ 2 and ≥ 5 coughs, respectively), total cell count, cell differentials and the levels of bradykinin, histamine, prostaglandin E₂, substance P, calcitonin gene-related peptide, pepsin, and interleukin-2 in the induced sputum detected by enzyme-linked immunosorbent assay were compared. The linear correlation between lgC2 and lgC5 and apnea hypopnea index, cell differentials, and inflammatory mediators in the induced sputum was calculated in OSAHS patients.

RESULTS

OSAHS patients presented with a significant lower C2 and C5 (P < 0.01), increased lymphocyte but decreased macrophage and neutrophil proportions in the induced sputum (P < 0.01), and higher contents of substance P, calcitonin gene-related peptide and interleukin-2 (P < 0.01) but similar levels of bradykinin, pepsin, prostaglandin E₂, and histamine (P > 0.05) in the supernatant of induced sputum, when compared with simple snoring patients and healthy volunteers. However, theses variable were comparable between simple snoring patients and healthy volunteers (P > 0.05). Finally, lgC2 or lgC5 was negatively related to apnea hypopnea index, lymphocyte percentage, and the levels of substance P, calcitonin gene-related peptide or interleukin-2 in the sputum (P < 0.01). There was a positive linear correlation between lymphocyte percentage and interleukin-2 level in the induced sputum (r = 0.63, P = 0.00).

CONCLUSION

OSAHS patients have a predisposition of cough hypersensitivity associated with airway inflammation.

Comparison of the effectiveness of lidocaine and salbutamol on coughing provoked by intravenous remifentanil during anesthesia induction

BACKGROUND

Coughing is a side effect of opioids that is rarely studied. Here, we evaluated the incidence of remifentanil induced coughing during anesthesia induction in an attempt to identify its risk factors and to examine the preventive effects of lidocaine and salbutamol.

METHODS

A total of 237 patients scheduled to undergo general anesthesia were allocated randomly into three groups. Group C received no medication, while Group L received 2% lidocaine at 0.5 mg/kg intravenously 1 minute prior to remifentanil infusion and Group S inhaled one metered aerosol puff of salbutamol 15 minutes prior to entering the operating room. Remifentanil was infused at 5 ng/ml by target controlled infusion and coughing was measured for five minutes and graded as none, mild, moderate, or severe based on the number of coughs.

RESULTS

The incidences of coughing were 30.4%, 25.3%, and 35.4% in Groups C, L, and S, respectively. The incidences, onset times, and severity of coughing did not differ significantly among groups. In addition, multivariate analysis showed that non-smoking and a lower body weight were risk factors of remifentanil-induced coughing (odds ratio, 8.13; P = 0.024, 1.11, and 0.004, respectively).

CONCLUSIONS

The incidence of remifentanil-induced coughing was 30%. A total of 0.5 mg/kg lidocaine and 1 metered aerosol puff of salbutamol did not prevent coughing. Non-smoking and low body weight were found to be risk factors of remifentanil-induced coughing.