Higher cough flow is associated with lower risk of pneumonia in acute stroke

Cough flows as a criterion for decannulation of autonomously breathing patients with tracheostomy tubes

BACKGROUND

Adequate cough or exsufflation flow can indicate an option for safe tracheostomy decannulation to noninvasive management. Cough peak flow via the upper airways with the tube capped is an outcome predictor for decannulation readiness in patients with neuromuscular impairment. However, this threshold value is typically measured with tracheotomy tube removed, which is not acceptable culturally in China. The aim of this study was to assess the feasibility and safety of using cough flow measured with tracheostomy tube and speaking valve (CFSV) > 100 L/min as a cutoff value for decannulation.

STUDY DESIGN

Prospective observational study conducted between January 2019 and September 2022 in a tertiary rehabilitation hospital.

METHODS

Patients with prolonged tracheostomy tube placement were referred for screening. Each patient was assessed using a standardized tracheostomy decannulation protocol, in which CFSV greater than 100 L/min indicated that the patients' cough ability was sufficient for decannulation. Patients whose CFSV matched the threshold value and other protocol criteria were decannulated, and the reintubation and mortality rates were followed-up for 6 months.

RESULTS

A total of 218 patients were screened and 193 patients were included. A total of 105 patients underwent decannulation, 103 patients were decannulated successfully, and 2 patients decannulated failure, required reinsertion of the tracheostomy tube within 48 h (failure rate 1.9%). Three patients required reinsertion or translaryngeal intubation within 6 months.

CONCLUSIONS

CFSV greater than 100 L/min could be a reliable threshold value for successful decannulation in patients with various primary diseases with a tracheostomy tube.

TRIAL REGISTRATION

This observational study was not registered online.

Pulmonary Function Tests Post-Stroke. Correlation between Lung Function, Severity of Stroke, and Improvement after Respiratory Muscle Training

Stroke is a significant cause of mortality and chronic morbidity caused by cardiovascular disease. Respiratory muscles can be affected in stroke survivors, leading to stroke complications, such as respiratory infections. Respiratory function can be assessed using pulmonary function tests (PFTs). Data regarding PFTs in stroke survivors are limited. We reviewed the correlation between PFTs and stroke severity or degree of disability. Furthermore, we reviewed the PFT change in stroke patients undergoing a respiratory muscle training program. We searched PubMed until September 2023 using inclusion and exclusion criteria in order to identify studies reporting PFTs post-stroke and their change after a respiratory muscle training program. Outcomes included lung function parameters (FEV1, FVC, PEF, MIP and MEP) were measured in acute or chronic stroke survivors. We identified 22 studies of stroke patients, who had undergone PFTs and 24 randomised controlled trials in stroke patients having PFTs after respiratory muscle training. The number of patients included was limited and studies were characterised by great heterogeneity regarding the studied population and the applied intervention. In general, PFTs were significantly reduced compared to healthy controls and predicted normal values and associated with stroke severity. Furthermore, we found that respiratory muscle training was associated with significant improvement in various PFT parameters and functional stroke parameters. PFTs are associated with stroke severity and are improved after respiratory muscle training.

Auditory-Perceptual Assessments of Cough: Characterizing Rater Reliability and the Effects of a Standardized Training Protocol

INTRODUCTION

Auditory-perceptual assessments of cough are commonly used by speech-language pathologists working with people with swallowing disorders with emerging evidence beginning to demonstrate their validity; however, their reliability among novice clinicians is unknown. Therefore, the primary aim of this study was to characterize the reliability of auditory-perceptual assessments of cough among a group of novice clinicians. As a secondary aim, we assessed the effects of a standardized training protocol on the reliability of auditory-perceptual assessments of cough.

METHODS

Twelve novice clinicians blindly rated ten auditory-perceptual cough descriptors for 120 cough audio clips. Standardized training was then completed by the group of clinicians. The same cough audio clips were then re-randomized and blindly rated. Reliability was analyzed pre- and post-training within each clinician (intra-rater), between each unique pair of raters (dyad-level inter-rater), and for the entire group of raters (group-level inter-rater) using intraclass correlation coefficients and Cohen's Kappa.

RESULTS

Pre-training reliability was greatest for measures of strength, effectiveness, and normality and lowest when judging the type of expiratory maneuver (cough, throat clear, huff, other). The measures that improved the most with training were ratings of perceived crispness, amount of voicing, and type of expiratory maneuver. Intra-rater reliability coefficients ranged from 0.580 to 0.903 pre-training and 0.756-0.904 post-training. Dyad-level inter-rater reliability coefficients ranged from 0.295 to 0.745 pre-training and 0.450-0.804 post-training. Group-level inter-rater reliability coefficients ranged from 0.454 to 0.919 pre-training and 0.558-0.948 post-training.

CONCLUSION

Reliability of auditory-perceptual assessments varied across perceptual cough descriptors, but all appeared within the range of what has been historically reported for auditory-perceptual assessments of voice and visual-perceptual assessments of swallowing and cough airflow. Reliability improved for most cough descriptors following 30-60 min of standardized training. Future research is needed to examine the validity of auditory-perceptual assessments of cough by assessing the relationship between perceptual cough descriptors and instrumental measures of cough effectiveness to better understand the role of perceptual assessments in clinical practice.

Computer-aided screening of aspiration risks in dysphagia with wearable technology: a Systematic Review and meta-analysis on test accuracy

Aspiration caused by dysphagia is a prevalent problem that causes serious health consequences and even death. Traditional diagnostic instruments could induce pain, discomfort, nausea, and radiation exposure. The emergence of wearable technology with computer-aided screening might facilitate continuous or frequent assessments to prompt early and effective management. The objectives of this review are to summarize these systems to identify aspiration risks in dysphagic individuals and inquire about their accuracy. Two authors independently searched electronic databases, including CINAHL, Embase, IEEE Xplore^® Digital Library, PubMed, Scopus, and Web of Science (PROSPERO reference number: CRD42023408960). The risk of bias and applicability were assessed using QUADAS-2. Nine (n = 9) articles applied accelerometers and/or acoustic devices to identify aspiration risks in patients with neurodegenerative problems (e.g., dementia, Alzheimer's disease), neurogenic problems (e.g., stroke, brain injury), in addition to some children with congenital abnormalities, using videofluoroscopic swallowing study (VFSS) or fiberoptic endoscopic evaluation of swallowing (FEES) as the reference standard. All studies employed a traditional machine learning approach with a feature extraction process. Support vector machine (SVM) was the most famous machine learning model used. A meta-analysis was conducted to evaluate the classification accuracy and identify risky swallows. Nevertheless, we decided not to conclude the meta-analysis findings (pooled diagnostic odds ratio: 21.5, 95% CI, 2.7-173.6) because studies had unique methodological characteristics and major differences in the set of parameters/thresholds, in addition to the substantial heterogeneity and variations, with sensitivity levels ranging from 21.7% to 90.0% between studies. Small sample sizes could be a critical problem in existing studies (median = 34.5, range 18-449), especially for machine learning models. Only two out of the nine studies had an optimized model with sensitivity over 90%. There is a need to enlarge the sample size for better generalizability and optimize signal processing, segmentation, feature extraction, classifiers, and their combinations to improve the assessment performance. Systematic Review Registration: (https://www.crd.york.ac.uk/prospero/), identifier (CRD42023408960).

Changes in Cough Airflow and Acoustics After Injection Laryngoplasty

OBJECTIVE/HYPOTHESIS

We explored the following hypotheses in a cohort of patients undergoing injection laryngoplasty: (1) glottic insufficiency affects voluntary cough airflow dynamics and restoring glottic competence may improve parameters of cough strength, (2) cough strength can be inferred from cough acoustic signal, and (3) glottic competence changes cough sounds and correlates with spectrogram morphology.

STUDY TYPE/DESIGN

Prospective interventional study.

METHODS

Subjects with glottic insufficiency secondary to unilateral vocal fold paresis, paralysis, or atrophy, and scheduled for injection laryngoplasty completed an instrumental assessment of voluntary cough airflow using a pneumotachometer and a protocolized voluntary cough sound recording. A Wilcoxon signed-rank test was used to compare the differences between pre- and post-injection laryngoplasty in airflow and acoustic measures. A Spearman rank-order correlation was used to evaluate the association between airflow and acoustic cough measures.

RESULTS

Twenty-five patients (13F:12M, mean age 68.8) completed voluntary cough airflow measurements and 22 completed cough sound recordings. Following injection laryngoplasty, patients had a statistically significant decreased peak expiratory flow rise time (PEFRT) (mean change: -0.03 s, SD: 0.06, p = 0.04) and increased cough volume acceleration (mean change: 13.1 L/s2 , SD: 33.9, p = 0.03), suggesting improved cough effectiveness. Correlation of cough acoustic measures with airflow measures showed a weak relationship between PEFRT and acoustic energy (coefficient: -0.31, p = 0.04) and peak power density (coefficient: -0.35, p = 0.02).

CONCLUSIONS

Our study thus indicates that injection laryngoplasty may help avert aspiration in patients with glottic insufficiency by improving cough effectiveness and that improved cough airflow measures may be tracked with cough sounds.

LEVEL OF EVIDENCE

3 Laryngoscope, 133:S1-S14, 2023.

Analysis of Dysphagia and Cough Strength in Patients with Unilateral Vocal Fold Paralysis

The association between swallowing function and cough strength in patients with unilateral vocal fold paralysis (UVFP) is unknown. We evaluated the relationship between voluntary cough strength and dysphagia among patients with UVFP (UVFP group) by comparing their data with that of corresponding healthy participants (healthy control [HC] group) in a prospective observational study. From February 1st, 2018 to March 30th, 2019, we recruited patients with a voice disorder due to UVFP, who were referred to our university hospital. Patients with a history of laryngeal surgery, vagal nerve paralysis, or cardiac and respiratory failure were excluded. Descriptive and clinical data regarding swallowing, voice, and cough peak flow (CPF) were collected as a measure of cough strength. The UVFP group comprised six women and seven men (median age, 68.0 years), and the HC group comprised six women and eight men (median age 65.5 years). The groups differed significantly in the Eating Assessment Tool (EAT)-10 scores and CPF rates (P < 0.001). Among patients with UVFP, 84.6% had an abnormal EAT-10 score of ≥ 3. Additionally, 16.7% of the patients exhibited liquid aspiration with contrast medium on a videofluorographic swallowing study (VFSS). There was no correlation between the CPF values, EAT-10 scores, or the VFSS results. Therefore, patients with severe UVFP, whose condition had been fixed, had difficulties when swallowing (85% of cases), and some even presented with aspiration on VFSS (20% of cases), while receiving a regular diet.

Impact on swallowing functions of arytenoid adduction in patients with unilateral vocal fold paralysis

OBJECTIVE

Although the pathophysiology of swallowing dysfunction in patients with unilateral vocal fold paralysis (UVFP) remains uncertain, glottal insufficiency is known to be a possible major cause, and other factors due to vagus nerve or recurrent laryngeal nerve damage may contribute to dysphagia or aspiration. This study aimed to evaluate the effect of arytenoid adduction (AA) surgery on the swallowing functions of UVFP patients and to investigate the important role of glottic closure during swallowing.

METHODS

We prospectively analyzed the data of thirteen patients with UVFP who underwent AA in combination with medialization laryngoplasty (ML) for improving voice quality. The subjects received a series of examinations for not only voice function but also swallowing function and cough strength both preoperatively and approximately 6 months after surgery. The evaluations of voice function included the Voice Handicap Index and aerodynamic measures; the evaluations of swallowing function included the Eating Assessment Tool-10, liquid aspiration, a videofluorographic examination of swallowing study, and high-resolution manometry; and the evaluation of cough strength included the measurement of cough peak flow. All measurements before and after surgery were statistically compared and examined.

RESULTS

Considerable improvements in voice measures were observed after the procedure, as sufficient glottic closure was achieved during phonation and swallowing. In terms of swallowing evaluation, there were significant differences in the subjective assessment methods after the operation. Additionally, our intervention improved two cases of aspiration according to abnormal findings on the videofluorographic examination of swallowing. There was a significant difference in cough peak flow, with all participants having better values after surgery. High-resolution manometry revealed no significant differences between pre- and postsurgery in any parameters at the level of the mesopharynx or upper esophageal sphincter.

CONCLUSION

The findings of our study suggest an important effect on the dysphagia of UVFP patients who undergo AA combined with ML. In addition, we revealed improvements in swallowing by strengthening incomplete glottic closure; thus, we consider that sufficient glottic closure must play an important role in swallowing function in patients with UVFP.

Peak expiratory flow, but not tongue pressure, can predict pneumonia development in older adults

PURPOSE

Pneumonia is the leading cause of mortality and morbidity in aging populations. Major causes of pneumonia in older adults are swallowing dysfunction and decreased airway clearance capacity, including an impaired cough reflex. Maximal tongue pressure is useful for evaluating swallowing function, and peak expiratory flow indirectly reflects cough strength. However, it is unclear whether they can predict pneumonia development in older adults. In this study, we investigated whether tongue pressure and peak expiratory flow could predict pneumonia development in older adults.

METHODS

This two-center prospective observational study included older adults aged 65 years or older without respiratory disease or head and neck cancer. We enrolled 383 consenting participants, many of whom had a history of stroke, and followed them for 2 years. The association between time to pneumonia development and tongue pressure or peak expiratory flow at enrollment was examined in a Cox proportional hazards model.

RESULTS

The mean age of the participants was 77.1 ± 6.2 years, and 36.0% of them were women. The mean tongue pressure was 35.4 ± 10.5 kPa and median peak expiratory flow was 218 L/min at enrollment. Six patients developed pneumonia during the study period. A low peak expiratory flow at enrollment was significantly associated with pneumonia development in the multivariate Cox proportional hazards model, but this association was not observed for tongue pressure.

CONCLUSION

Decreased peak expiratory flow may predict pneumonia development in older adults. Future studies should investigate interventions for peak expiratory flow improvement.

Post-stroke respiratory complications using machine learning with voice features from mobile devices

Abnormal voice may identify those at risk of post-stroke aspiration. This study was aimed to determine whether machine learning algorithms with voice recorded via a mobile device can accurately classify those with dysphagia at risk of tube feeding and post-stroke aspiration pneumonia and be used as digital biomarkers. Voice samples from patients referred for swallowing disturbance in a university-affiliated hospital were collected prospectively using a mobile device. Subjects that required tube feeding were further classified to high risk of respiratory complication, based on the voluntary cough strength and abnormal chest x-ray images. A total of 449 samples were obtained, with 234 requiring tube feeding and 113 showing high risk of respiratory complications. The eXtreme gradient boosting multimodal models that included abnormal acoustic features and clinical variables showed high sensitivity levels of 88.7% (95% CI 82.6–94.7) and 84.5% (95% CI 76.9–92.1) in the classification of those at risk of tube feeding and at high risk of respiratory complications; respectively. In both cases, voice features proved to be the strongest contributing factors in these models. Voice features may be considered as viable digital biomarkers in those at risk of respiratory complications related to post-stroke dysphagia.

Weak cough is associated with increased mortality in COPD patients with scheduled extubation: a two-year follow-up study

Background

Cough strength is associated with short-term outcome in patients with scheduled extubation who successfully complete a spontaneous breathing trial (SBT). However, the long-term outcome is unclear.

Methods

This was a prospective observational study performed in a respiratory ICU of a teaching hospital. COPD patients who successfully completed a SBT were candidates. We enrolled the case who assessed the cough strength by cough peak flow (CPF) or semiquantitative cough strength score (SCSS, ranging from 0 = weak to 5 = strong). Patients were followed up to two years by phone every 3 months.

Results

A total of 215 patients were enrolled in current study. Among them, CPF and SCSS were measured in 214 and 208 cases, respectively. Strong cough was associated with a 16% decrease in the risk of two-year mortality (adjusted hazard ratio [HR] 0.84, 95%CI: 0.78–0.91) per 10 L/min increment of CPF. When it was tested by SCSS, decrease in the risk of two-year mortality per unit increment was 27% (adjusted HR 0.73, 95%CI: 0.62–0.86). Similar results were confirmed in the discharged patients. In all patients, the two-year mortality was 75%, 53%, and 38% in patients with CPF < 60, 60–90, and > 90 L/min; and 85%, 70%, and 40% in patients with SCSS of 0–1, 2–3, and 4–5, respectively. Similar trend was found among the discharged patients whether it was assessed by CPF or SCSS.

Conclusions

In COPD patients, weak cough is associated with increased two-year mortality after a scheduled extubation. It provides objective information to caregivers to improve decision-making process during hospitalization and after discharge.

Soft Exoskeleton Mimics Human Cough for Assisting the Expectoration Capability of SCI Patients

OBJECTIVE

This paper describes the design of a bionic soft exoskeleton and demonstrates its feasibility for assisting the expectoration function rehabilitation of patients with spinal cord injury (SCI).

METHODS

A human-robot coupling respiratory mechanic model is established to mimic human cough, and a synergic inspire-expire assistance strategy is proposed to maximize the peak expiratory flow (PEF), the key metric for promoting cough intensity. The negative pressure module of the exoskeleton is a soft "iron lung" using layer-jamming actuation. It assists inspiration by increasing insufflation to mimic diaphragm and intercostal muscle contraction. The positive pressure module exploits soft origami actuators for assistive expiration; it pressures human abdomen and bionically "pushes" the diaphragm upward.

RESULTS

The maximum increase in PEF ratios for mannequins, healthy participants, and patients with SCI with robotic assistance were 57.67%, 278.10%, and 124.47%, respectively. The soft exoskeleton assisted one tetraplegic SCI patient to cough up phlegm successfully.

CONCLUSION

The experimental results suggest that the proposed soft exoskeleton is promising for assisting the expectoration ability of SCI patients in everyday life scenarios.

SIGNIFICANCE

The proposed soft exoskeleton is promising for advancing the application field of rehabilitation exoskeletons from motor functions to respiratory functions.

Inhalation Therapy with Nebulized Capsaicin in a Patient with Oropharyngeal Dysphagia Post Stroke: A Clinical Case Report

Dysphagia and aspiration risk are common sequelae of stroke, leading to increased risk of stroke-associated pneumonia. This is often aggravated by stroke-related impairment of cough, the most immediate mechanical defense mechanism against aspiration. In humans, reflex cough can be repeatedly and safely elicited by inhalation of nebulized capsaicin, a compound contained in chili peppers. Could this cough-eliciting property of capsaicin support the recovery of stroke survivors who present with dysphagia and aspiration risk? We present a clinical case report of a 73-year-old man, admitted to inpatient stroke rehabilitation following a right middle cerebral artery infarct with subsequent dysphagia and hospital-acquired pneumonia. A course of daily inhalation therapy with nebulized capsaicin was initiated, triggering reflex coughs to support secretion clearance and prevent recurrence of pneumonia. Clinical observations in each inhalation therapy session demonstrate good patient response, safety and tolerability of nebulized capsaicin in this mode of application. Repeated Fiberoptic Endoscopic Evaluation of Swallowing (FEES) assessments show concurrent improvement in the patient’s swallowing status. Inhalation therapy with nebulized capsaicin may offer a viable treatment to facilitate coughing and clearing of secretions, and to minimize aspiration and risk of aspiration-related pneumonia post stroke. Further investigation in a randomized controlled trial design is warranted.

Peak Voluntary Cough Flow and Oropharyngeal Dysphagia as Risk Factors for Pneumonia

Objective

To investigate the relationship between voluntary peak cough flow (PCF), oropharyngeal dysphagia, and pneumonia in patients who were evaluated with videofluoroscopic swallowing study (VFSS).

Methods

Patients who underwent both VFSS and PCF measurement on the same day were enrolled retrospectively (n=821). Pneumonia (n=138) and control (n=683) groups were assigned based on presence of pneumonia within 1 month from the date of VFSS assessment. In addition, sex, age (<65 and ≥65 years), preceding conditions, modified Barthel Index (MBI), Mini-Mental State Examination (MMSE), PCF value (<160, ≥160 and <270, and ≥270 L/min), and presence of aspiration/penetration on VFSS were reviewed.

Results

Pneumonia group was more likely to be male (n=108; 78.3%), ≥65 years (n=121; 87.7%), with neurodegenerative (n=25; 18.1%) or other miscellaneous diseases (n=50; 36.2%), and in poor functional level with lower value of MBI (39.1±26.59). However, MMSE was not significantly different in comparison to that of the control group. The pneumonia group was also more likely to have dysphagia (82.6%) and lower value of PCF (<160 L/min, 70.3%). In multivariable logistic regression analysis, male sex (odd ratio [OR]=6.62; 95% confidence interval [CI], 2.70–16.26), other miscellaneous diseases as preceding conditions (OR=2.52; 95% CI, 1.14–5.58), dysphagia (OR=3.82; 95% CI, 1.42–10.23), and PCF <160 L/min (OR=14.34; 95% CI, 1.84–111.60) were factors significantly related with pneumonia.

Conclusion

Impaired swallowing and coughing function showed an independent association with the development of pneumonia. Patients with PCF <160 L/min require more attention with lung care and should be encouraged with voluntary coughing strategy to prevent possible pulmonary complications.

Stroke and breathing

Stroke remains a leading cause of neurologic disability with wide ranging effects, including a variety of respiratory abnormalities. Stroke may influence the central control of the respiratory drive and breathing pattern, airway protection and maintenance, and the respiratory mechanics of inspiration and expiration. In the acute phase of stroke, the central control of breathing is affected by changes in consciousness, cerebral edema, and direct damage to brainstem respiratory centers, resulting in abnormalities in respiratory pattern and loss of airway protection. Common acute complications related to respiratory dysfunction include dysphagia, aspiration, and pneumonia. Respiratory control centers are located in the brainstem, and brainstem stroke causes specific patterns of respiratory dysfunction. Depending on the exact location and extent of stroke, respiratory failure may occur. While major respiratory abnormalities often improve over time, sleep-disordered breathing remains common in the subacute and chronic phases and worsens outcomes. Respiratory mechanics are impaired in hemiplegic or hemiparetic stroke, contributing to worse cardiopulmonary health in stroke survivors. Interventions to address the respiratory complications are under researched, and further investigation in this area is critical to improving outcomes among stroke survivors.

Prognostic Value of Preoperative Peak Expiratory Flow to Predict Postoperative Pulmonary Complications in Surgical Lung Cancer Patients

Objectives

Cough impairment may lead to excessive accumulation of pulmonary secretions and increase the risk of postoperative pulmonary complications (PPCs). Peak expiratory flow (PEF) is a sensitive indicator of cough ability. We aimed to investigate the correlation between PEF and PPCs for lung cancer patients undergoing lobectomy or segmental resection for improved risk assessment.

Methods

This retrospective study assessed 560 patients with non-small cell lung cancer admitted for surgery between January 2014 to June 2016. The measurements of PEF were performed before surgery and the clinical outcomes were recorded, including PPCs, postoperative hospital stay, hospitalization costs, and other variables.

Results

Preoperative PEF was significantly lower in PPCs group compared to non-PPCs group (294.2 ± 95.7 vs. 363.0 ± 105.6 L/min, P < 0.001). Multivariable regression analysis showed that high PEF (OR=0.991, 95%CI: 0.988-0.993, P < 0.001) was an independent protective factor for PPCs. According to the receiver operating characteristic (ROC) curve, a PEF value of 250 L/min was selected as the optimal cutoff value in female patients, and 320 L/min in male patients. Patients with PEF under cutoff value of either sex had higher PPCs rate and unfavorable clinical outcomes.

Conclusions

Preoperative PEF was found to be a significant predictor of PPCs for surgical lung cancer patients. It may be beneficial to consider the cutoff value of PEF in perioperative risk assessment.

Swallowing and laryngeal complications in lung and heart transplantation: Etiologies and diagnosis

Despite continued surgical advancements in the field of cardiothoracic transplantation, post-operative complications remain a burden for the patient and the multidisciplinary team. Lesser-known complications including swallowing disorders (dysphagia), and voice disorders (dysphonia), are now being reported. Such disorders are known to be associated with increased morbidity and mortality in other medical populations, however their etiology amongst the heart and lung transplant populations has received little attention in the literature. This paper explores the potential mechanisms of oropharyngeal dysphagia and dysphonia following transplantation and discusses optimal modalities of diagnostic evaluation and management. A greater understanding of the implications of swallowing and laryngeal dysfunction in the heart and lung transplant populations is important to expedite early diagnosis and management in order to optimize patient outcomes, minimize allograft injury and improve quality of life.

Stroke and Pneumonia: Mechanisms, Risk Factors, Management, and Prevention

A stroke is a cerebrovascular medical emergency characterized by the sudden loss of neurological function due to interruption to the blood supply. A serious and common complication of stroke is pneumonia. This review article outlined various studies in order to understand the pathogenesis pathways that lead to the development of stroke-associated pneumonia, as well as therapeutic and preventive options to reduce pneumonia. The article looked for risk factors that increase the risk of developing pneumonia among stroke patients. In addition, it has reviewed various therapeutic modalities, such as postural modifications, pharmacological treatment, and other unique treatments, in an attempt to find which of them are efficient to decrease the occurrence of pneumonia and which of them are not. The article also attempts to emphasize the importance of early screening for dysphagia among stroke patients and demonstrates the importance of preventive strategies that can be easily implemented, such as routine oral care and behavioral modifications.

Relationship between kyphosis and cough strength and respiratory function of community-dwelling elderly

BACKGROUND

Kyphosis may reduce the force of coughing by affecting the factors related to cough peak flow (CPF). This study sought to compare cough strength and respiratory function between non-kyphotic and kyphotic elderly individuals and clarify the relationship between these factors.

METHODS

The non-kyphotic group comprised 17 elderly individuals with a kyphosis index of less than 15.1, while the kyphotic group comprised 21 elderly individuals with a kyphosis index of 15.1 or higher. Cough strength, respiratory function, respiratory muscle strength, and maximum phonation time were measured, and comparison between two groups and correlation analysis between variables were performed.

RESULTS

CPF, vital capacity, maximum expiratory pressure (PEmax), maximum inspiratory pressure (PImax), and chest expansion at the xiphoid process were significantly lower in the kyphotic group than in the non-kyphotic group. There were significant negative correlations between kyphosis index and CPF (r = -0.37, p < 0.05), PEmax (r = -0.45, p < 0.01), PImax (r = -0.44, p < 0.01) and chest expansion at the xiphoid process (r = -0.38, p < 0.05).

CONCLUSIONS

Our results demonstrated that cough strength was significantly lower in the kyphotic compared to non-kyphotic individuals. Furthermore, cough strength decreased with increased severity of kyphosis.

Predictive Value of Cough Frequency in Addition to Aspiration Risk for Increased Risk of Pneumonia in Dysphagic Stroke Survivors: A Clinical Pilot Study

BACKGROUND

Post-stroke dysphagia leads to increased risk of aspiration and subsequent higher risk of pneumonia. It is important to not only diagnose post-stroke dysphagia early but also to evaluate the protective mechanism that counteracts aspiration, i.e., primarily cough. The aim of this study was to investigate the predictive value of cough frequency in addition to aspiration risk for pneumonia outcome.

METHODS

This was a single-center prospective observational study. Patients with first-ever strokes underwent clinical swallowing evaluation, fibreoptic endoscopic evaluation of swallowing (FEES), and overnight cough recording using LEOSound^® (Löwenstein Medical GmbH & Co. KG, Bad Ems, Germany ). Penetration-Aspiration Scale (PAS) ratings and cough frequency measurements were correlated with incidence of pneumonia at discharge.

RESULTS

11 women (37%) and 19 men (63%), mean age 70.3 years (SD ± 10.6), with ischemic stroke and dysphagia were enrolled. Correlation analysis showed statistically significant relationships between pneumonia and PAS (r = 0.521; p < 0.05), hourly cough frequency (r = 0,441; p < 0.05), and categories of cough severity (r = 0.428 p < 0.05), respectively. Logistic regression showed significant predictive effects of PAS (b = 0.687; p = 0.014) and cough frequency (b = 0.239; p = 0.041) for pneumonia outcome.

CONCLUSION

Cough frequency in addition to aspiration risk was an independent predictor of pneumonia in dysphagic stroke survivors.

Objective measurement of acoustic intensity of coughing for clearance of penetration and aspiration on video-fluoroscopy

PURPOSE

This preliminary, exploratory study evaluated the acoustic intensity of effective and ineffective clearance of penetrated and aspirated material from the laryngeal vestibule in patients with dysphagia.

METHOD

A lapel microphone was attached anterior to participants' tragus and recorded coughing in decibels during their videofluoroscopic swallowing studies (VFSS).

RESULT

Eighty-eight patients were recruited. Thirteen patients, with visible airway invasion and coughing were included in the final analysis. No coughs were effective at expelling aspirated material from the airway (n = 10). Both effective (4/7) and ineffective (3/7) coughing to penetration were recorded. The mean acoustic intensity of effective coughing to penetration was -44.0 dBFS (decibel level relative to full scale) [SD = 7.3, 95% CI = -51.14, -36.86], and ineffective coughing to penetration was only marginally lower at -42.9 dBFS [SD = 2.0, 95% CI = -45.21, -40.59].

CONCLUSION

No coughs were effective at expelling aspirated material from the airway. Some coughs effectively expelled penetrated material from the airway. However, the relationship between acoustic intensity and cough effectiveness is unclear due to the limited number of observations. Given that perceptual evaluation of coughing is widely used in dysphagia clinical practice to determine cough effectiveness, this is an important area for future research.

Global Physiology and Pathophysiology of Cough: Part 1: Cough Phenomenology - CHEST Guideline and Expert Panel Report

The purpose of this state-of-the-art review is to update the American College of Chest Physicians 2006 guideline on global physiology and pathophysiology of cough. A review of the literature was conducted using PubMed and MEDLINE databases from 1951 to 2019 and using prespecified search terms. We describe the basic phenomenology of cough patterns, behaviors, and morphological features. We update the understanding of mechanical and physiological characteristics of cough, adding a contemporary view of the types of cough and their associated behaviors and sensations. New information about acoustic characteristics is presented, and recent insights into cough triggers and the patient cough hypersensitivity phenotype are explored. Lastly, because the clinical assessment of patients largely focuses on the duration rather than morphological features of cough, we review the morphological features of cough that can be measured in the clinic. This is the first of a two-part update to the American College of Chest Physicians 2006 cough guideline; it provides a more global consideration of cough phenomenology, beyond simply the mechanical aspects of a cough. A greater understanding of the typical features of cough, and their variations, may allow a more informed interpretation of cough measurements and the clinical relevance for patients.

Comparison of physical properties of voluntary coughing, huffing and swallowing in healthy subjects

Coughing, huffing and swallowing protect the airway from aspiration. This study was conducted to compare the physical properties of voluntary coughing, huffing and swallowing in healthy subjects. Ten healthy men were asked to huff, cough and swallow repeatedly. Electromyograms (EMGs) were recorded from the left side of the external oblique (EO), sternocleidomastoid, suprahyoid (SH) and thyrohyoid muscles. Airflow was recorded using a face mask with two-way non-rebreathing valves. The expiratory velocity of huffing and coughing and the SH EMG of all actions presented high intraclass correlation coefficients (> 0.8). The inspiratory and expiratory velocities did not differ significantly between coughing and huffing. The expiratory acceleration of coughing was significantly higher than that of huffing, whereas the expiratory volume of coughing was significantly smaller than that of huffing. The EO EMG of coughing and huffing were significantly larger than that of swallowing. The EO EMG activity during the expiratory phase was significantly higher than that of the other phases of both coughing and huffing. The SH EMG of coughing and huffing were significantly smaller than that of swallowing. Correlation analysis revealed that the expiratory velocity of coughing was strongly positively correlated with that of huffing. The expiratory volume of huffing was significantly positively correlated with hand grip strength. These results suggest that EO and SH muscle activities during huffing or coughing differ those during swallowing, and huffing and coughing may work similarly in expiratory function.

Effect of Brain Lesions on Voluntary Cough in Patients with Supratentorial Stroke: An Observational Study

Patients with stroke are known to manifest a decreased cough force, which is associated with an increased risk of aspiration. Specific brain lesions have been linked to impaired reflexive coughing. However, few studies have investigated whether specific stroke lesions are associated with impaired voluntary cough. Here, we studied the effects of stroke lesions on voluntary cough using voxel-based lesion-symptom mapping (VLSM). In this retrospective cross-sectional study, the peak cough flow was measured in patients who complained of weak cough (n = 39) after supratentorial lesions. Brain lesions were visualized via magnetic resonance imaging (MRI) at the onset of stroke. These lesions were studied using VLSM. The VLSM method with non-parametric mapping revealed that lesions in the sub-gyral frontal lobe and superior longitudinal and posterior corona radiata were associated with a weak cough flow. In addition, lesions in the inferior parietal and temporal lobes and both the superior and mid-temporal gyrus were associated with a weak peak cough flow during voluntary coughing. This study identified several brain lesions underlying impaired voluntary cough. The results might be useful in predicting those at risk of poor cough function and may improve the prognosis of patients at increased risk of respiratory complications after a stroke.

[Relationship between cough peak flow and onset of pneumonia in residents of geriatric health services facilities]

AIM

Sputum expectoration is associated with cough strength, which can be evaluated by cough peak flow (CPF). Since sputum expectoration can be difficult for patients with reduced CPF, they are more likely to have risk factors for pneumonia. We conducted a study to clarify factors contributing to CPF in residents of geriatric health services facilities and to assess the relationship between CPF and the onset of pneumonia.

METHODS

We included 41 male residents of geriatric health services facilities from September to the middle of October 2018. We recorded each subject's age, body mass index (BMI), Performance Status (PS), nursing care level, Functional Independence Measure (FIM), pulse rate, percutaneous arterial oxygen saturation (SpO₂), hand grip strength, Charlson comorbidity index, underlying diseases and rales upon auscultation. We also used Pearson's correlation analysis to analyze the relationship between CPF and the above factors. Subjects were assigned to 2 groups according to median CPF to determine the between-group relationships of these factors. Finally, subjects were followed up for 6 to 11 months after CPF measurement to confirm whether or not they developed pneumonia.

RESULTS

CPF was positively correlated with BMI (nutritional parameter), hand grip strength (index of systemic muscular strength), and SpO₂ The median CPF was 240 L/minute, and subjects were divided into 2 groups based on this valus: CPF ≤240 L/minute group (n=21) and CPF >240 L/minute group (n=20). Subjects in the CPF ≤240 L/minute group demonstrated lower BMI and hand grip strength but more pronounced rales upon auscultation. No statistically significant difference was observed between the 2 groups during the 6-month folloe-up. However, the 11-month follow-up demonstrated a higher incidence of pneumonia in the CPF ≤240 L/minute group.

CONCLUSION

The above findings suggest that subjects with reduced CPF are more likely to develop pneumonia. To increase CPF, muscle rehabilitation therapy and nutrition management should be provided to residents of geriatric health services facilities to prevent pneumonia.

The present and future of cough counting tools

The widespread use of cough counting tools has, to date, been limited by a reliance on human input to determine cough frequency. However, over the last two decades advances in digital technology and audio capture have reduced this dependence. As a result, cough frequency is increasingly recognised as a measurable parameter of respiratory disease. Cough frequency is now the gold standard primary endpoint for trials of new treatments for chronic cough, has been investigated as a marker of infectiousness in tuberculosis (TB), and used to demonstrate recovery in exacerbations of chronic obstructive pulmonary disease (COPD). This review discusses the principles of automatic cough detection and summarises key currently and recently used cough counting technology in clinical research. It additionally makes some predictions on future directions in the field based on recent developments. It seems likely that newer approaches to signal processing, the adoption of techniques from automatic speech recognition, and the widespread ownership of mobile devices will help drive forward the development of real-time fully automated ambulatory cough frequency monitoring over the coming years. These changes should allow cough counting systems to transition from their current status as a niche research tool in chronic cough to a much more widely applicable method for assessing, investigating and understanding respiratory disease.

Physical Activity Intolerance and Cardiorespiratory Dysfunction in Patients with Moderate-to-Severe Traumatic Brain Injury

Moderate-to-severe traumatic brain injury (TBI) is a chronic health condition with multi-systemic effects. Survivors face significant long-term functional limitations, including physical activity intolerance and disordered sleep. Persistent cardiorespiratory dysfunction is a potentially modifiable yet often overlooked major contributor to the alarmingly high long-term morbidity and mortality rates in these patients. This narrative review was developed through systematic and non-systematic searches for research relating cardiorespiratory function to moderate-to-severe TBI. The literature reveals patients who have survived moderate-to-severe TBI have ~ 25-35% reduction in maximal aerobic capacity 6-18 months post-injury, resting pulmonary capacity parameters that are reduced 25-40% for weeks to years post-injury, increased sedentary behavior, and elevated risk of cardiorespiratory-related morbidity and mortality. Synthesis of data from other patient populations reveals that cardiorespiratory dysfunction is likely a consequence of ventilator-induced diaphragmatic dysfunction (VIDD), which is not currently addressed in TBI management. Thus, cardiopulmonary exercise testing should be routinely performed in this patient population and those with cardiorespiratory deficits should be further evaluated for diaphragmatic dysfunction. Lack of targeted treatment for underlying cardiorespiratory dysfunction, including VIDD, likely contributes to physical activity intolerance and poor functional outcomes in these patients. Interventional studies have demonstrated that short-term exercise training programs are effective in patients with moderate-to-severe TBI, though improvement is variable. Inspiratory muscle training is beneficial in other patient populations with diaphragmatic dysfunction, and may be valuable for patients with TBI who have been mechanically ventilated. Thus, clinicians with expertise in cardiorespiratory fitness assessment and exercise training interventions should be included in patient management for individuals with moderate-to-severe TBI.

Role of injection laryngoplasty in preventing post-stroke aspiration pneumonia, case series report

INTRODUCTION

Injection laryngoplasty is a common procedure for patients with vocal fold dysfunction, but the literature on its benefits has been mainly focused on those related to structural lesions or laryngeal nerve involvement. Stroke patients may be at increased risk of aspiration due to insufficient vocal fold motion. However, how injection laryngoplasty can be of benefit in stroke patients has not been reported yet.

PATIENT CONCERNS

Six chronic stroke patients with long-standing swallowing difficulties and who showed severe aspiration despite long-term swallowing rehabilitation.

DIAGNOSIS

Laryngoscope evaluation revealed insufficient glottic closure as the cause of aspiration.

INTERVENTIONS

Injection laryngoplasty was done per-orally under local anaesthesia with calcium hydroxylapatite (Radiesse Voice, 1-1.5 mL) in an office setting. Respiratory pressures and peak cough flows were assessed at baseline and at 2 weeks follow-up.

OUTCOMES

At 2 weeks, the mean peak cough flow (Δ = +95.09 L/min) increased significantly after the procedure. The maximal expiratory (Δ = +18.40 cm H2O) and inspiratory (Δ = +20.20 cm H2O) pressures also improved, indicating that injection laryngoplasty was effective in augmenting respiratory and cough parameters. All cases showed improvement in the Functional Oral Intake Scale (Δ = +4). Feeding tubes were successfully removed.

CONCLUSION

Injection laryngoplasty proved to be both successful and safe in improving glottic closure with immediate results in those who had failed to show a positive response after long-term swallowing rehabilitation. The positive and dramatic clinical outcomes were observed through changes in the coughing force. Our case series support the use of injection larygnoplasty as a powerful adjunctive treatment method to prevent aspiration pneumonia in post-stroke patients with vocal fold insufficiency. Pre- and post-injection peak cough flow changes may reflect improvement in glottic closure and indicate the safety of swallowing with reduced risk of aspiration.

Effectiveness of expiratory muscle strength training on expiratory strength, pulmonary function and cough in the adult population: a systematic review

BACKGROUND

Respiratory muscle strength declines in certain disease states, leading to impaired cough, reduced airway clearance and an increased risk of aspiration pneumonia. Respiratory muscle training may therefore reduce this risk.

OBJECTIVES

To assess current evidence of expiratory muscle strength training (EMST) on maximum expiratory pressure, cough flow and spirometry.

DATA SOURCES

Databases including CINAHL, Medline, Science Direct and PEDRo were searched.

ELIGIBILITY CRITERIA

Randomised controlled trials investigating expiratory muscle strength training on maximum expiratory pressure, pulmonary function or cough in any adult population, published before December 2017.

STUDY APPRAISAL

Data were extracted to a trial description form and study quality evaluated by two reviewers. Meta-analysis was performed with calculation of mean differences and 95% confidence intervals.

RESULTS

Nine studies met inclusion criteria and ranged in size from 12 to 42 participants. Trials investigated EMST in healthy adults (2), multiple sclerosis (3), COPD (2), acute stroke (1) and spinal cord injury (1). Overall, EMST improved maximum expiratory pressure (15.95cmH₂O; 95% CI: 7.77 to 24.12; P<0.01) with no significant impact on cough flow (4.63L/minute; 95%CI -27.48 to 36.74; P=0.78), forced vital capacity (-0.16L; 95%CI -0.35 to 0.02; P=0.09) or forced expiratory volume in 1second (-0.09L; 95%CI -0.10 to -0.08; P<0.001) vs control or sham training.

CONCLUSIONS

Meta-analysis indicated a small significant increase in maximum expiratory pressure following EMST. Improvements in maximum expiratory pressure did not lead to improvements in cough or pulmonary function.

LIMITATIONS

Variations in protocol design and population limited the overall effect size. Systematic Review Registration PROSPERO CRD42018104190.

Definition of Respiratory Sarcopenia With Peak Expiratory Flow Rate

OBJECTIVES

Respiratory muscle strength decreases with advancing age, and respiratory muscle dysfunction may indicate respiratory sarcopenia. However, there is no consensus regarding the definition of respiratory sarcopenia. We aimed to create a definition of respiratory sarcopenia based on the peak expiratory flow rate (PEFR).

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

Community-based study including 681 community-dwelling older people.

METHODS

Body composition, spirometry, grip strength, and walking speed were measured. Participants reported comorbidities and long-term insurance certification. Conventional sarcopenia was defined using skeletal muscle mass, grip strength, and walking speed adjusted for the Japanese population. Receiver operating characteristic (ROC) curve analysis of the cut-off values of PEFR for conventional sarcopenia and long-term care insurance certification were performed for both sexes without airway obstruction. In the ROC curve analysis, potential cut-off values were lowest quartile, lowest quintiles, and the standard deviation of PEFR. Multiple logistic regression analysis was performed with respiratory sarcopenia as a dependent variable defined by each cut-off value and other variants as independent variables.

RESULTS

The ROC curve analysis for conventional sarcopenia and long-term care insurance certification showed significance for both sexes, and we determined cut-off values from those results. The multiple logistic regression model using PEFR values 1 standard deviation below the mean had the highest accuracy; thus, we accepted these cut-off values (4.40 L/s for men, 3.21 L/s for women) for the definition of respiratory sarcopenia.

CONCLUSIONS/IMPLICATIONS

The definition of respiratory sarcopenia based on PEFR was useful and correlated with conventional sarcopenia and long-term care insurance certification among community-dwelling older people. In this study, respiratory sarcopenia was determined by PEFR alone. Other parameters may need to be considered.

Cough, a vital reflex. mechanisms, determinants and measurements

Cough is a natural defense mechanism that protects the respiratory tract from inhaling foreign bodies and by clearing excessive bronchial secretions. As a spontaneous reflex arc, it involves receptors, an afferent pathway, a center processing information, an efferent pathway and effectors. The determinant factor of cough efficacy is the operational volume of the lung, which in turn relies on the strength and coordination of respiratory and laryngeal muscles as well as on lung mechanics. Respiratory muscle weakness and dysfunction as well as expiratory flow limitation and lung hyperinflation may occur in some neuromuscular disorders and in obstructive airway diseases, respectively. Accordingly, all these diseases may show an ineffective cough. In this brief overview, we deal with the determinants of the cough efficacy and the clinical conditions affecting cough efficacy as well as the cough’s efficacy measurements in clinical setting. (www.actabiomedica.it)

[Effect of A High Intensive Preoperative Rehabilitation on the Perioperative Complications in Patients with Chronic Obstructive Pulmonary Disease Eligible for Lung Cancer Surgery]

背景与目的

慢性阻塞性肺病(chronic obstructive pulmonary diseases, COPD)降低患者心肺功能，可导致患者围手术期风险增加。本研究拟探讨术前短期高强度肺康复训练对肺癌合并COPD患者肺功能及术后并发症的影响。

方法

分析2016年6月-2016年12月101例肺癌合并COPD患者的临床资料，其中肺康复训练组43例，常规治疗组58例，比较两组患者肺功能、术后肺部并发症、住院时间等指标，同时比较肺康复训练组训练前后肺功能相关指标。

结果

两组患者术前一般资料及肺功能无显著差异，康复训练组住院时间更长[(17.23±4.18) d vs (14.41±4.03) d]，但术后住院时间与常规治疗组无显著差异[(8.93±3.78) d vs (9.62±3.98) d]，两组患者术后肺部感染[8例(18.6%) vs 17例(29.3%)]、肺不张[1例(2.3%) vs 1例(1.7%)]、呼吸衰竭[1例(2.3%) vs 2例(3.4%)]等无显著差异。肺康复训练组训练前后FEV₁[(2.06±0.45) L vs (2.15±0.45) L, P < 0.001]、PEF[(4.32±0.90) L/s vs (5.15±1.05) L/s, P < 0.001]、PCO₂[(42.42±2.79) mmHg vs (41.58±2.98) mmHg, P=0.009]改善明显，按亚组分析，康复训练后中-重度COPD亚组FEV₁[(0.16±0.05) L (8.6%) vs (0.06±0.05) L (2.8%)]增加值较轻度COPD亚组更明显。

结论

术前短期肺康复训练可改善肺癌合并COPD患者肺功能，其中中-重度COPD患者肺功能改善更明显。

Implementing Cough Reflex Testing in a Clinical Pathway for Acute Stroke: A Pragmatic Randomised Controlled Trial

Silent aspiration is common after stroke and can lead to subsequent pneumonia. While standard bedside dysphagia assessments are ineffective at predicting silent aspiration, cough reflex testing (CRT) has shown promise for identifying patients at risk of silent aspiration. We investigated the impact of CRT on patient and service outcomes when embedded into a clinical pathway. 488 acute stoke patients were randomly allocated to receive either CRT or standard care (i.e. bedside assessment). Primary outcomes included confirmed pneumonia within 3 months post stroke and length of acute inpatient stay. Secondary outcomes related to the feasibility of implementing a CRT pathway and clinician and patient satisfaction. There was a non-significant reduction in pneumonia rates by 2.2% points in the CRT group (OR 0.32, 95% CI 0.06-1.62). There was a non-significant difference of 0.7 days (95% CI - 0.29 to 1.71 days) in length of stay between the standard care group and the CRT group. The CRT took on average 3 min longer to complete (p < 0.01) and resulted in a significant 6.7% increase in videofluoroscopic referrals (p = 0.02); however, these results are clinically insignificant. High patient and clinician satisfaction with CRT was found, with clinicians reporting additional knowledge and confidence in decision making for dysphagia management. Post hoc subgroup analyses according to stroke types were conducted and revealed no significant differences in pneumonia rates after adjustment for multiple comparisons. In conclusion, it was possible to implement a CRT pathway with minimal increases in clinician resources. While clinicians perceived CRT as beneficial in clinical decision making, the efficacy of CRT for reducing pneumonia rates in acute stroke remains to be established.Clinical Trial Registration-URL: http://www.anzctr.org.au . Unique identifier: ACTRN12616000724471.

Changes in Peak Airflow Measurement During Maximal Cough After Vocal Fold Augmentation in Patients With Glottic Insufficiency

Importance

Compromised cough effectiveness is correlated with dysphagia and aspiration. Glottic insufficiency likely yields decreased cough strength and effectiveness. Although vocal fold augmentation favorably affects voice and likely improves cough strength, few data exist to support this hypothesis.

Objective

To assess whether vocal fold augmentation improves peak airflow measurements during maximal-effort cough following augmentation.

Design, Setting, and Participants

This case series study was conducted in a tertiary, academic laryngology clinic. Participants included 14 consecutive individuals with glottic insufficiency due to vocal fold paralysis, which was diagnosed via videostrobolaryngoscopy as a component of routine clinical examination. All participants who chose to proceed with augmentation were considered for the study whether office-based or operative augmentation was planned. Postaugmentation data were collected only at the first follow-up visit, which was targeted for 14 days after augmentation but varied on the basis of participant availability. Data were collected from June 5, 2014, to October 1, 2015. Data analysis took place between October 2, 2015, and March 3, 2017.

Main Outcomes and Measures

Peak airflow during maximal volitional cough was quantified before and after vocal fold augmentation. Participants performed maximal coughs, and peak expiratory flow during the maximal cough was captured according to American Thoracic Society guidelines.

Results

Among the 14 participants (7 men and 7 women), the mean (SD) age was 62 (18) years. Three types of injectable material were used for vocal fold augmentation: carboxymethylcellulose in 5 patients, hyaluronic acid in 5, and calcium hydroxylapatite in 4. Following augmentation, cough strength increased in 11 participants and decreased cough strength was observed in 3. Peak airflow measurements during maximal cough varied from a decrease of 40 L/min to an increase of 150 L/min following augmentation. When preaugmentation and postaugmentation peak airflow measurements were compared, the median improvement was 50 L/min (95% CI, 10-75 L/min; P = .01). Immediate peak airflow measurements during cough collected within 30 minutes of augmentation varied when compared with measurements collected at follow-up (103-380 vs 160-390 L/min).

Conclusions and Relevance

Peak airflow during maximal cough may improve with vocal fold augmentation. Additional assessment and measurements are needed to further delineate which patients will benefit most regarding their cough from vocal fold augmentation.

Effects of expiratory muscle activation via high-frequency spinal cord stimulation

In persons with spinal cord injury, lower thoracic low-frequency spinal cord stimulation (LF-SCS; 50 Hz, 15 mA) is a useful method to restore an effective cough. Unfortunately, the high-stimulus-amplitude requirements and potential activation of pain fibers significantly limit this application in persons with intact sensation. In this study, the mechanism of the expiratory muscle activation, via high-frequency SCS (HF-SCS; 500 Hz, 1 mA) was evaluated in dogs. In group 1, the effects of electrode placement on airway pressure generation (P) was evaluated. Maximal P occurred at the T9-T10 level with progressive decrements in P at more rostral and caudal levels for both LF-SCS and HF-SCS. In group 2, electromyographic (EMG) latencies of internal intercostal muscle (II) activation were evaluated before and after spinal root section and during direct motor root stimulation. Onset time of II EMG activity during HF-SCS was significantly longer (3.84 ± 1.16 ms) than obtained during direct motor root activation (1.61 ± 0.10 ms). In group 3, P and external oblique (EO) EMG activity, before and after sequential spinal section at the T11-T12 level, were evaluated. Bilateral dorsal column section significantly reduced EO EMG activity below the section and resulted in a substantial fall in P. Subsequent lateral funiculi section completely abolished those activities and resulted in further reductions in P. We conclude that 1) activation of the expiratory muscles via HF-SCS is dependent entirely on synaptic spinal cord pathways, and 2) HF-SCS at the T9 level produces a comparable level of muscle activation with that achieved with LF-SCS but with much lower stimulus amplitudes. NEW & NOTEWORTHY The findings in the present study suggest that lower thoracic high-frequency spinal cord stimulation with low stimulus currents results in sufficient activation of the expiratory muscles via spinal circuitry to produce large positive airway pressures sufficient to generate an effective cough mechanism. This method, therefore, may be applied in patient populations with intact sensation such as stroke and amyotrophic lateral sclerosis to restore an effective cough.

Computational Modelling of Cough Function and Airway Penetrant Behavior in Patients with Disorders of Laryngeal Function

Objective/Hypothesis

Patients with laryngeal disorders often exhibit changes to cough function contributing to aspiration episodes. Two primary cough variables (peak cough flow: PCF and compression phase duration: CPD) were examined within a biomechanical model to determine their impact on characteristics that impact airway compromise.

Study Design

Computational study

Methods

A Computational Fluid Dynamics (CFD) technique was used to simulate fluid flow within an upper airway model reconstructed from patient CT images. The model utilized a finite‐volume numerical scheme to simulate cough‐induced airflow, allowing for turbulent particle interaction, collision, and break‐up. Liquid penetrants at 8 anatomical release locations were tracked during the simulated cough. Cough flow velocity was computed for a base case and four simulated cases. Airway clearance was evaluated through assessment of the fate of particles in the airway following simulated cough.

Results

Peak‐expiratory phase resulted in very high airway velocities for all simulated cases modelled. The highest velocity predicted was 49.96 m/s, 88 m/s, and 117 m/s for Cases 1 and 3, Base case, and Cases 2 and 4 respectively. In the base case, 25% of the penetrants cleared the laryngeal airway. The highest percentage (50%) of penetrants clearing the laryngeal airway are observed in Case 2 (with −40% CPD, +40% PCF), while only 12.5% cleared in Case 3 (with +40% CPD, −40% PCF). The proportion that cleared in Cases 1 and 4 was 37.5%.

Conclusion

Airway modelling may be beneficial to the study of aspiration in patients with impaired cough function including those with upper airway and neurological diseases. It can be used to enhance understanding of cough flow dynamics within the airway and to inform strategies for treatment with “cough‐assist devices” or devices to improve cough strength.

Level of Evidence

N/A.

Cough modulation by upper airway stimuli in cat - potential clinical application?

The modulation of mechanically induced tracheobronchial cough was tested by applying various stimuli and the elicitation of other airway protective behaviors in pentobarbital anesthetized cats. Capsaicin and histamine were injected in the nose, and mechanical nylon fiber and / or air puff stimulation was applied to the nose and nasopharynx. Reflex responses of cough, sneeze, aspiration reflex and expiration reflex were induced mechanically. Swallow was initiated by the injection of water into oropharynx. Subthreshold mechanical stimulation of nasopharyngeal and nasal mucosa, as well as water stimulation in the oropharynx and larynx, with no motor response, had no effect on rhythmic coughing. Cough responsiveness and excitability increased with capsaicin and air puff stimuli delivered to the nose. Vice versa, the number of cough responses was reduced and cough latency increased when aspiration reflexes (>1) occurred before the cough stimulus or within inter-cough intervals (passive E2 cough phase). The occurrence of swallows increased the cough latency as well. Cough inspiratory and / or expiratory motor drive was enhanced by the occurrence of expiration reflexes, swallows, and sneezes and also by aspiration reflex within the inspiratory phase of cough and by nasal air puff stimuli. Complex central interactions, ordering and sequencing of motor acts from the airways may result in the disruption of cough rhythmic sequence but also in the enhancement of cough. Our data confirm that number of peripheral stimuli and respiratory motor responses significantly alters cough performance. We propose developing and testing stimulation paradigms that modify coughing and could be employed in correcting of inappropriate or excessive coughing.