None listed
Conditions
Brief summary
Background: This project seeks to answer the clinical question of whether it is possible to rehabilitate the cough reflex. Dysphagia refers to disordered swallowing, the nature of which can be neurological, structural (due to injury or cancer), or developmental. Patients with dysphagia are at high risk of dystussia (impairment of the cough reflex), which is unsurprising given the close association of the neural, anatomical and physiological mechanisms involved in both reflexes. Coughing serves as a vital airway protective mechanism, and is of particular importance for patients with dysphagia, for which aspiration (when food/liquid enters the airway below the vocal cords) frequently occurs. In the absence of an intact cough reflex, these patients are at risk of silent aspiration (aspiration in the absence of triggering a cough reflex) and aspiration pneumonia (lung infection from inhalation of food/liquids) and are generally considered unsafe for oral intake. Both the sensory and motor components of the cough reflex can be impaired. The citric acid cough reflex test (CRT) is a reliable, objective, clinically applicable assessment of cough sensitivity that enables clinicians to identify patients at risk of silent aspiration with high sensitivity and specificity (Miles et al, 2013; Miles & Huckabee, 2013, Miles et al, 2014). The introduction of a CRT protocol for acute stroke patients in Christchurch Hospital alone reduced the prevalence of aspiration pneumonia from 26% to 11%, with estimated savings of $1.4 million [press release - Retrieved from http://www.cdhb.health.nz/News/Media-Releases/Pages/Outstanding-Quality-Improvement- Innovation-Awards.aspx)]. While clinicians can now identify patients with an absent or impaired cough reflex at bedside, there are currently no treatments available for them. Many patients are placed on non-oral methods of feeding and are not prescribed swallowing rehabilitation exercises to promote their recovery, due to their high risk of aspiration and pulmonary system compromise. Successful rehabilitation of the cough reflex would offer patients the opportunity to engage in swallowing rehabilitation while maintaining adequate airway protection. It would also offer clinicians the opportunity to assume an active rehabilitation role. Objectives: This aim of this study is to determine the optimal parameters to safely enhance cough reflex sensitivity (as measured by citric acid cough reflex threshold) in healthy individuals, using ultrasonically nebulised distilled water (UNDW), which is a known tussigenic agent currently used in cough challenge tests.
Interventions
The study will be conducted over 5 days. On day one, participants’ citric acid cough thresholds will be obtained. Citric acid cough threshold will be obtained by exposing participants to incrementally increasing concentrations of citric acid (0.01 to 3.2 mol/l). Citric acid will be administered using a breath activated dosimeter and a jet nebuliser (De Vilbiss 646). Participants will take three single inhalations of the citric acid until they produce a C2 cough response at a given concentration.
The study will be conducted over 5 days. On day one, participants’ citric acid cough thresholds will be obtained. Citric acid cough threshold will be obtained by exposing participants to incrementally increasing concentrations of citric acid (0.01 to 3.2 mol/l). Citric acid will be administered using a breath activated dosimeter and a jet nebuliser (De Vilbiss 646). Participants will take three single inhalations of the citric acid until they produce a C2 cough response at a given concentration. Their cough threshold will be confirmed by re-administering the same concentration. Cough threshold is defined as the lowest concentration of citric acid capable of eliciting a C2 cough response, on the same concentration of citric acid twice Participants will also rate their urge to cough (UTC) following each citric acid inhalation. Following phase one, participants will be randomly assigned to a supra-threshold group or a sub-threshold group. A no-treatment control group will also be included, in which participants receive inhalations of saline in place of distilled water. The supra-threshold group will receive the maximum nebulising output from the nebuliser 1.6 ml/min and the sub-threshold group will receive 0.5 ml/min. Participants will inhale UNDW once a day for 4 days (Tuesday - Friday). Repeated rapid stimulation of UNDW, in cycles of 5 breaths + 10 sec break x 5 times (totalling approx. 1 minute of direct UNDW stimulation per cycle), will be used to stimulate and modulate the cough reflex. These cycles will be repeated 12 times per session. Between each cycle, there will be a minimum of a 1-minute break. Spirometry will be taken at regular intervals throughout the cycles. Total sensory stimulation session will be 1 hour 30 mins. Comparisons between these groups will determine the optimal and safest stimulation parameters to enhance cough sensitivity. Outcome measures will include pre-treatment, mid-treatment (3 days) and post-treatment (5 days) citric acid cough reflex threshold testing. Respiratory measures (forced expiratory volume in 1 second) will be taken throughout and in between stimulation to ensure the safety of the protocol.
Sponsors
University of Canterbury
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Treatment
Masking
Blinded (masking used) (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Participants must be healthy and capable of providing informed, written consent to participate.
Exclusion criteria
History of asthma, neurological disorders, respiratory diseases or gastro-esophageal reflux. Any participants ACE inhibitor drugs, codeine, smoking, or have had a upper respiratory chest infection in the past 2 weeks..
Outcome results
None listed