Background: One population prone to aspiration pneumonia and impaired cough is the postoperative patient. Postoperative pneumonia is the third most common complication among surgical patients after urinary tract and wound infections (Wren, Martin, Yoon, & Bech, 2010). A patient who has their surgical course complicated by aspiration pneumonia has increased morbidity, increased length of hospital stay and places greater demands on the health system. Mortality rates are cited as high as 70% (Wren, et al., 2010). Despite the prevalence of postoperative pneumonia and the high morbidity and mortality rates, little is known about the effect of anaesthesia on swallowing and airway protection. This study investigated the effect of clinical doses of fentanyl on suppressed cough reflex in healthy participants. Materials and Methods: After receiving ethical approval, 14 young, healthy participants gave informed written consent and completed the study protocol. Each participant received a total of 2 mcg/kg of fentanyl in four doses administered at five-minute intervals. Fentanyl effect site concentrations (ESC) were estimated using a standard pharmacokinetic model. During the administration period, suppressed cough response testing (SCR) with nebulised citric acid was performed after each fentanyl dose. Citric acid was presented in increments of 0.2M from each participant’s baseline cough response until a present-strong response was achieved. During the post-administration period, SCR was compared with reducing effect site concentrations to determine the time course for resolution of cough suppression. Results: Suppressed cough threshold increased and decreased in parallel with modeled fentanyl effect site concentrations. Mean citric acid concentration increased from 0.5M at baseline to 0.6M after 0.5 mcg/kg of fentanyl, 0.7 M after 1 mcg/kg of fentanyl, 0.9M after 1.5 mcg/kg of fentanyl and 1.2M after 2 mcg/kg of fentanyl. Predicted effect site concentrations after final doses of fentanyl (2 mcg/kg) were 1.89 ng/mL (1.81-1.96), well within the range seen clinically in the postoperative period. After the final dose of fentanyl, participants had on average 3.4 increments of change in their cough response (at increments of 0.2M). Conclusion: SCR testing with citric acid is sensitive enough to mirror changes in fentanyl ESC in healthy, young participants. The degree of reflex suppression seen has been associated with an 8-fold increase in aspiration risk in the general medical patient with dysphagia (Miles, Moore, McFarlane, Lee, Allen, Huckabee, 2013). Further research into the application of SCR in the postoperative period may help clinical decisions regarding safety to commence oral intake.

The aim of this study was to determine whether there was an association between a failed test of cough reflex sensitivity and history of chest infection in a general population of rest home residents. One hundred rest home residents from four different levels of care (rest home, hospital, dementia and psycho-geriatric) were recruited and their cough reflex assessed using a solution of 0.6 Mol/L citric acid nebulised and presented via a facemask.Participant’s records were then checked to see if there were any documented episodes of chest infection in the 6 month period prior to cough reflex testing.The results showed that out of 100 participants, 4 failed the cough reflex test. Of the 4 that failed the test, 3 had no documented episodes of chest infections recorded in the 6 month period prior to cough reflex testing. Data was not available for one participant who was deceased by the time of collection of the second data set. As such, there was no direct association demonstrated between a failed cough reflex test and development of chest infection or aspiration pneumonia. The results of the study are unexpected in two ways. Firstly, the relatively low number of participants who failed the cough reflex test is surprising as 72% of the participants for whom a full data set was obtained had neurological conditions that are known predisposing factors for reduced cough reflex sensitivity. Secondly, the finding of no association between a failed cough reflex test and history of recorded chest infection is not consistent with other studies. There is however an established body of research that indicates the causes of aspiration pneumonia are multifactorial and not solely dependent upon aspiration. The characteristics of participants and the implications of the findings are described. The potential use of cough reflex testing as a tool to screen against the risks of silent aspiration in relation to assessment of oro-pharyngeal dysphagia in this frail, elderly population is discussed.

Patients with an impaired reflexive cough response are at increased risk of pneumonia. This study examined the correlation between cough sensitivity to citric acid and radiographic features of airway compromise. Eighty patients referred for a radiographic assessment of swallowing at an acute hospital over an 8-month period participated in the study. Nebulised citric acid diluted in 0.9% sodium chloride was inhaled through a facemask at four concentrations to assess cough sensitivity. These data were then compared to Penetration Aspiration Scale scores based on radiographic swallowing studies. There was a statistically significant correlation between cough response/lack of response and the radiographic features of airway compromise; that is, patients who had a weak or absent response to inhalation of citric acid were also likely to aspirate silently during radiographic assessment. Sensitivity for identifying absent cough was found to be high at all 4 concentrations (0.750, 0.833, 0.941, 1.000), however specificity was consistently quite low (0.344, 0.456, 0.238, 0.078). The significant findings of this research suggest that clinicians adopting cough reflex testing into their clinical practice will have a reliable screen for silent aspiration at bedside. Clinicians will be able to identify patients who require instrumental assessment and are at high risk of pneumonia. This will likely, in turn, decrease length and cost of hospital admissions as well as decrease aspiration pneumonia related morbidities.

Cough reflex testing (CRT) is used to assess the sensory and motor components of a reflexive cough. When used as an adjunct to the clinical swallowing evaluation, it has the potential to identify individuals who are more likely to aspirate silently in the event of aspiration. It is unknown how reliable clinicians are at interpreting cough responses and the factors that influence this reliability. Therefore, this study ascertained the reliability of Speech Language Therapists in interpreting cough responses in CRT and determined how sensory perception and training influence reliability. Additionally, the study determined a relative measure of CRT interpretation validity through a comparison with ‘expert’ consensus ratings. A total of 111 clinicians completed an online survey consisting of ratings of 30 audio-, visual- and audiovisual clips over three sessions, and a final questionnaire. Reliability was substantial (κ=.76) in rating for presence of cough but only fair (κ=.25) in rating for strength of cough. Clinicians used a variety of auditory and visual cues to assist in decision making. Training did not result in higher reliability. Ratings of individual clinicians were significantly associated with consensus ratings for presence of cough (p < 0.001) and strength of cough (p < 0.05). In summary, clinicians could reliably and accurately judge presence of cough response, but were poorer at rating the strength of cough.

Background: Cough Reflex Testing (CRT) has been shown to be useful in the challenging task of identifying silent aspiration (aspiration without a cough response). With the emergence of the routine clinical use of CRT in the acute stroke population, the following clinical conundrum often arises: Does passing a previously failed CRT mean the risk of silent aspiration has resolved? The purpose of this study was to evaluate the association between change in laryngeal cough threshold sensitivity and change in PAS (Penetration Aspiration Scale) score within the acute stage post-stroke. Methods: This was a prospective longitudinal pilot study of 20 acute stroke patients utilizing a Cough Reflex Threshold Test (CRTT) at 0.4M, 0.6M and 0.8M citric acid concentrations and Fiberoptic Endoscopic Evaluation of Swallowing (FEES). A cough response threshold was obtained from the CRTT and a PAS (penetration aspiration scale) score from FEES. Inclusion criteria required a PAS score of 4 or above on preliminary FEES or impaired CRT threshold as defined by weak or failed cough test result at 0.8M citric acid concentration. Both test methods were repeated every four days for 20 days or until the participant no longer aspirated/penetrated and had a normal result on CRTT on two consecutive assessment sessions. Agreement between changes in the two tests was evaluated using the Cohen’s Kappa statistic. Results: Eighteen of the twenty participants in this study aspirated on initial assessment, ten of which were silent. One participant continued to aspirate at study completion. On initial assessment eleven participants had a C2 response threshold at 0.4M citric acid concentration and three participants failed to reach threshold at 0.8M citric acid concentration. At study completion, 18 participants had a C2 response threshold at 0.4M citric acid concentration and one participant failed to reach threshold at 0.8M citric acid concentration. During the study, sixty-six re-assessments took place; there were fifteen incidences of improved cough response threshold on re-assessment and thirty-one incidences of improved PAS score. There was no significant agreement between improved laryngeal cough reflex threshold and improved PAS score during the acute stage Kappa = 0.0598 (p <.0.574), 95% CI (- 0.1496- 0.2692). Conclusion: Significant limitations of this study included small data set and potential flooring effect of the CRT. Due to the limitations of this study, no conclusions can be made as to the appropriateness of reinstating oral intake based on passing a previously failed CRT.

One of the most elusive challenges in the diagnosis and treatment of dysphagia is the reliable identification of silent aspiration (aspiration in the absence of cough). The citric acid inhalation cough challenge offers potential for aiding in identification of silent aspiration; however clinical application of this technique is currently problematic due to an absence of normative data. Therefore, this study aimed to establish a normative data set for the Citric- Acid Inhalation Cough Challenge, as administered with facemask method. 80 healthy subjects will participate in this study, constituting 2 age groups: above and below 60 years, with equal gender representation. On 3 separate trials, they will be asked to passively inhale, via a facemask, nebulised citric acid of concentrations ranging from 08M to 2.6M with placebo interspersed. ‘Natural cough thresholds’ (NCT) and ‘Suppressed Cough Thresholds’ (SCT) will be reached when subjects cough on at least 2 out of 3 trials. The majority (92.5%) of participants reached Natural Cough Threshold by 0.8M, with 68% demonstrating Suppressed Cough Threshold also at this concentration. There were no significant differences found between males and females (p<0.05) for either NCT (p=0.9885) or SCT (p=0.44). Whilst no difference was found between youngers and elders for NCT (p=0.7254), there was a significant difference for SCT (p=0.018), with youngers better able to suppress cough. Over 90% of healthy people were found to elicit cough at 0.8M, inferring that this level would be an adequate guide for use by clinicians testing for presence/absence of cough.

Silent aspiration is associated with pneumonia and mortality, and is poorly identified by traditional clinical swallowing evaluation (CSE). Currently, there is no reliable test for detecting silent aspiration during CSE. There is, however, increasing evidence for the validity of cough reflex testing (CRT) for identifying silent aspiration. This test has the potential to significantly improve clinical assessment of dysphagia. The aim of this research programme was to further investigate the validity, reliability and clinical utility of CRT for identifying patients at risk of silently aspirating. Several aspects of CRT were explored during this research programme. Two correlational studies were conducted to validate CRT for identifying silent aspiration against videofluoroscopic swallowing study (VFSS) and flexible endoscopic evaluation of swallowing (FEES). Cough reflex threshold testing was completed on 181 patients using inhaled, nebulised citric acid. Within one hour, 80 patients underwent VFSS and 101 patients underwent FEES. All tests were recorded and analysed by two researchers blind to the result of the alternate test. Significant associations between CRT result and cough response to aspiration on VFSS (p = .003) and FEES (p < .001) were identified. Sensitivity and specificity were optimised at 0.6mol/L in patients undergoing VFSS (71%, 60% respectively) and at 0.4mol/L in patients undergoing FEES (69%, 71% respectively). A concentration of 0.8mol/L had the highest odds ratio (OR) for detecting silent aspiration (8 based on VFSS, 7 based on FEES). Coughing on lower concentrations of citric acid (0.4mol/L compared with 1.2mol/L) was a better predictive measure of silent aspiration. Diminished cough strength has also been associated with aspiration and increased risk of pneumonia. Reflexive cough is our primary defensive mechanism against aspiration and a measure of reflexive cough strength therefore holds greater relevance than one of voluntary cough strength. Despite common use and clinical applicability, the reliability of subjective cough judgements has received little attention. The inter- and intra-rater reliability of subjective judgements of cough in patients following inhalation of citric acid was assessed. Forty-five speech-language therapists (SLTs) were recruited to the first study. Of these, 11 SLTs were currently using CRT in their clinical practice (experienced raters) and 34 SLTs reported no experience with CRT (inexperienced raters). Participants provided a rating of strong, weak or absent to ten video segments of cough responses elicited by inhalation of nebulised citric acid. The same video segments presented in a different sequence were re- evaluated by the same clinicians following a 15-minute break. Inter-rater reliability for experienced raters was calculated with a Fleiss’ generalised kappa of .49; intra-rater reliability was higher with a kappa of .70. Inexperienced raters showed similar reliability with kappa values for inter-rater and intra-rater reliability of .36 and .62, respectively. SLTs demonstrated only fair to moderate reliability in subjectively judging a patient’s cough response to citric acid. Experience in making cough judgements did not improve reliability significantly. In a second study, specific training in cough physiology and cough judgement was provided to 58 trained SLTs. Inter-rater reliability of subjective judgements of cough in patients following inhalation of citric acid was assessed. Participants provided a rating of present or absent, and if present then a rating of strong or weak, to ten video segments of cough responses. Inter-rater reliability for cough presence was calculated with a Fleiss’ generalised kappa of .71 and cough strength was calculated at .61. Years of clinical experience did not improve inter-rater reliability significantly. Experience in using CRT did improve inter-rater reliability. Further validity and reliability research would be beneficial for guiding clinical guidelines and training programmes. By identifying patients at risk of silent aspiration, more informed management decisions can be made that consequently lead to a reduction in preventable secondary complications such as pneumonia. The clinical utility of CRT for reducing pneumonia in acute stroke patients was assessed through a randomised, controlled trial. Three hundred and eleven patients referred for swallowing evaluation were assigned to either 1) a control group receiving standard evaluation or 2) an experimental group receiving standard evaluation with CRT. Participants in the experimental group were administered nebulised citric acid with test results contributing to clinical decisions. Outcomes for both groups were measured by pneumonia rates at three months post stroke and other clinical indices of swallowing management. Analysis of the data identified no significant differences between groups in pneumonia rate (p = .38) or mortality (p = .15). Results of CRT were shown to influence diet recommendations (p < .0001) and referrals for instrumental assessment (p <.0001). Despite differences in clinical management between groups, the end goal of reducing pneumonia in post stroke dysphagia was not achieved. Through this research, the characteristics and outcomes associated with dysphagia secondary to stroke in New Zealand were identified. Baseline characteristics of 311 patients with dysphagia following acute stroke were collected during their hospital stay and outcomes were measured at three months post stroke. Mortality rates were 16% and pneumonia rates 27%. Mean length of stay was 24 days and only 45% of patients were in their own home at three months post stroke. Pneumonia was significantly associated with mortality and increased length of stay. Only 13% of patients received referral for instrumental assessment of swallowing. These data are discussed in reference to the National Acute Stroke Services Audit 2009 and internationally published data. The outcomes for stroke patients with dysphagia in New Zealand are poor with a high risk of pneumonia and long hospital stays when compared internationally. In summary, this research programme has contributed to our understanding of the use of CRT in patients with dysphagia. The addition of a measure of reflexive cough strength may add to clinical assessment but specific training is required to reach adequate reliability. CRT results are significantly associated with aspiration response on instrumental assessment and lower concentrations of citric acid provide a better predictive measure of silent aspiration. CRT can be standardised and therefore is not as susceptible to interpretative variance that plagues much of CSE. Sensitivity and specificity values using this CRT methodology are adequate for CRT to be incorporated into clinical protocols. Inclusion of CRT alone was not shown to be sufficient to change clinical outcomes however integration of CRT into clinical pathways may prove more successful. Further research evaluating the addition of CRT to a comprehensive CSE would add greatly to the field of dysphagia assessment.

Introduction : La toux est un symptôme fréquent dans l’asthme, en particulier à l’effort mais peu des choses sont connus quant aux mécanismes impliqués. L’objectif de cette étude a été d’établir le rôle de l’exercice dans la modulation du réflexe de toux (RT) sur un modèle de lapin anesthésié en ventilation spontanée, présentant une inflammation éosinophilique des voies aériennes. Méthode : Nous avons étudié 10 lapins sensibilisés à l’ovalbumine (OVA) et 8 lapins contrôles. La réponse ventilatoire à la stimulation mécanique trachéale (ST) a été analysée pour chaque lapin en conditions de repos et à l’exercice pour quantifier l’incidence et la sensibilité de la toux. Le lavage bronchioloalaveolaire (LBA) et le comptage cellulaire a été réalisé pour vérifier la présence d’une inflammation à éosinophiles chez les lapins sensibilisés à l’OVA. Pour reproduire l’exercice, des contractions musculaires au niveau des pattes arrière ont été induites par stimulation électrique (CME). Résultats : Au total, 494 ST ont été réalisées, 261 en repos et 233 à l’exercice. Le taux d’éosinophiles dans le LBA a été retrouvé significativement plus élevé chez les lapins sensibilisés à l’OVA (vs contrôles, p=0.008). La CME a permis une augmentation similaire de l’ordre de 35% de la ventilation minute chez les lapins sensibilisés à l’OVA et chez les lapins contrôles par rapport au repos. La sensibilité du RT a été retrouvée significativement diminuée à l’exercice par rapport au repos pour les lapins contrôles (p=0.0313) contrairement aux lapins sensibilisés à l’OVA pour lesquels elle reste inchangée. Conclusion : Le phénomène de “down-regulation” du RT à l’exercice décrit chez les lapins contrôles n’a pas été observé chez les lapins sensibilisés à l’OVA. D’autres études sont nécessaires afin d’établir le rôle spécifique de l’inflammation bronchique sur la disparition du phénomène de “down-regulation” de la toux à l’exercice chez les patients asthmatiques / Introduction: Cough is a major symptom of asthma frequently experienced during exercise but little is known about interactions between cough and exercise. The goal of our study was to clarify the potential modulation of the cough reflex (CR) by exercise in a spontaneously breathing anaesthetized animal model of airway eosinophilic inflammation. Materials & methods: Ten ovalbumin (OVA) sensitized rabbits and 8 controls were studied. The ventilatory response to direct (TS) performed both at rest and during exercise was determined to quantify the incidence and the sensitivity of the CR. Broncho-alveolar lavages (BAL) and cell counts were performed to assess the level of the airway inflammation following OVA-induced sensitization. Exercise was mimicked by electrically induced hind limb muscular contractions (EMC). Results: Among 494 TS were performed, 261 at rest and 233 at exercise. The OVA sensitized rabbits have a higher level of eosinophil (p=0.008) in BAL. EMC increased minute ventilation by 36% in OVA rabbits vs 35% in control rabbits, compared to rest values. The sensitivity of the CR decreased during exercise compared to baseline in control rabbits (p=0.0313) while it remained unchanged in OVA rabbits. Conclusion: The down-regulation of the CR during exercise in control rabbits was abolished in OVA rabbits. The precise role of airway inflammation in this lack of CR downregulation needs to be further investigated but it might contribute to the exercise-induced cough in asthmatics