Evaluation and Treatment of Cough for the Speech-Language Pathologist
Published in the September 2024 issue of the ISHA Voice
By Lisa Bloom, Medical Practice Issues Committee member, and Lea Rose Markham, Medical Practice Issues Committee co-chair
Introduction
Cough is the final line of defense in protecting the respiratory system from aspiration. For speech-language pathologists (SLPs), understanding the nuances of cough evaluation and treatment is critical in treating both acute and chronic dysphagia. This article discusses the physiology of the airway protection mechanism, evaluation of cough strength, treatment of dystussia (impaired cough), and how speech-language pathologists may use these skills in their daily practice.
Background
To best understand dystussia, it is first imperative to review the six underpinnings of airway protection. When material attempts to enter or enters the larynx, the body’s first line of dense is to swallow. Second, the aspirate triggers initiation of the laryngeal adductor reflex by irritating the laryngeal mucosa - the bilateral thyroarytenoids adduct to provide glottic closure. Muscles of the chest wall, diaphragm, and abdomen begin to contract to increase pressure in the lungs., Theexpiratory reflex is initiated causing a forceful exhalation against the closed glottis. Note that there is no inspiratory effort before this reflex, as to protect the body from further inhalation of the aspirate. Expiratory effort produces a forceful expulsion of air from the lungs. Through this high velocity airflow, the fifth and sixth mechanisms of airway protection - throat clearing and coughing - open the glottis and release air as well as potential aspirates through the mouth. Many medical conditions impacting patients with dysphagia can result in reduced expiratory effort or disruptions to any of these airway defensive mechanisms.
Dystussia
Dystussia,or reduced cough effectiveness, may reflect either a reduced reflex response or weakened motor response. Identifying patients with dystussia can increase the SLP’s ability to predict who may be at a higher risk of developing sequelae of aspiration, or pneumonia. Clinically, dystussia is described as a maximum peak cough flow of less than 5 liters per second. The addition of dystussia evaluation and treatment may help SLPs better navigate the nuances of dysphagia management as a patient’s likelihood of developing aspiration pneumonia from dysphagia may at least, in part, be related to their ability to clear aspirate from the respiratory system.
Evaluation
Cough itself can be assessed in two main categories: strength and skill. Cough strength involves peripheral muscle movement, expiratory output (maximum expiratory pressure) and inspiratory output (maximum inspiratory pressure). Digital or analog handheld manometers can measure maximum inspiratory and expiratory pressures. Cough skills can be described as sensation, optimization of the respiratory cycle, coordination for ejection, and urge to cough.
Along with this, literature refers to two types of cough: voluntary and reflexive. Voluntary cough is initiated by the individual, whereas reflexive cough, is an involuntary response to an irritant of the respiratory system, which can include aspirate. Evaluation of voluntary cough principles has historically included obtaining maximum inspiratory and expiratory pressures. Additional evaluation of voluntary cough can be assessed for both single and sequential coughs. Literature highlights beginning with assessment of sequential cough, as this variety is a more common bodily response than a single cough. Troche (2020) suggests obtaining two trials of each cough type, each with varying verbal and visual instructions/models, while the patient coughs into a peak cough flow meter attached to a disposable air cushion mask via a bacteria filter to obtain their peak cough flow. Borders (2022) works to define clinically meaningful cutoffs for those impacted by neurodegenerative disorders. In regard to single voluntary cough, Borders and Troche (2022) define peak cough flow rate of >300 liters per minute as normal, 200-300 liters per minute as potentially abnormal and <200 liters per minute to be abnormal with an increased rate of pneumonia development.
In the field of speech-language pathology, evaluation of reflexive cough has historically included auditory perceptual assessment. A similar system and methodology as described above for voluntary cough can be implored to assess reflexive cough. With the addition of a compressor nebulizer attached to the peak cough flow meter exposing the patient to a tussigenic agent (such as capsaicin or citric acid), peak cough flow is again measured. If using citric acid as your tussigenic agent, literature has outlined an ideal concentration of 0.8 mol/L.
Treatment
Many SLPs are familiar with evaluation and treatment of voluntary cough through inspiratory and expiratory muscles strength training devices, which have a theoretical basis for supporting cough strength. However, these do not work to improve reflexive cough, which is critical for improving dystussia and ultimately working to improve a patient’s ability to clear aspirate. Training cough skills can improve both the voluntary and reflexive cough. This can include sensorimotor training in airway protection (smTAP) and cough skills training. smTAP is designed to enhance the effectiveness of coughing through targeted exercise and biofeedback. It focuses on improving the coordination and strength of the respiratory muscles involved in coughing, thereby increasing the efficiency of both voluntary and reflexive coughs. Though smTAP may not be feasible in a clinical setting at this time, it shows promise in its clinical utility. Cough skills training guides the SLP to set targets at 25% above baseline peak cough flow and cue the patient to cough into the meter, with a prescription of 5 sets of 5 repetitions 5 times per week for 5 weeks. Peak cough flow is reassessed once weekly and targets adjusted. Note, cough strength and cough skills training are not mutually exclusive. Using both interventions may yield improvement in dystussia.
Closing
With research guiding the evolution of dysphagia evaluation and interventions, SLPs are increasing their clinical repertoire to better serve patients, partnering with key stakeholders to improve quality of life and reduce the risk of dysphagia related disease development. A thorough understanding of airway protection, dystussia, cough evaluation and treatment is becoming a critical component of the clinical acumen. Discussing these modalities with referring providers to increase education and elucidate any specific considerations for individual patients is an important component of success for any treatment approach. Ongoing research in dystussia and cough is a necessary endeavor to improve treatment for those at risk of impaired airway protection.
References
Bianchi, C., Baiardi, P., Khirani, S., & Cantarella, G. (2012). Cough peak flow as a predictor of pulmonary morbidity in patients with dysphagia. American journal of physical medicine & rehabilitation, 91(9), 783-788.
Borders, J.C., Curtis, J.A., Sevitz, J.S., Vanegas-Arroyave, N., & Troche, M.S. (2022). Immediate effects of sensorimotor training in airway protection (smTAP) on cough outcomes in progressive supranuclear palsy: A feasibility study. Dysphagia, 37, 74-83
Borders, J.C. & Troche, M.S. (2022). Voluntary cough effectiveness and airway clearance in neurodegenerative disease. Journal of Speech, Language and Hearing Research, 65, 431-449.
Curtis, J. A., & Troche, M. S. (2020). Handheld Cough Testing: A Novel Tool for Cough Assessment and Dysphagia Screening. Dysphagia, 1-8.
Curtis, J. A., Borders, J. C., Dakin, A. E., & Troche, M. S. (2023). Auditory-Perceptual Assessments of Cough: Characterizing Rater Reliability and the Effects of a Standardized Training Protocol. Folia Phoniatrica et Logopaedica
Doruk, C., Curtis, J.A., Dakin, A.E., & Troche, M.S (2023). Cough and swallowing therapy and their effects on vocal fold bowing and laryngeal lesions. The Laryngoscope, 00, 1-6.
Hegland, K. W., Okun, M. S., & Troche, M. S. (2014). Sequential voluntary cough and aspiration or aspiration risk in Parkinson’s disease. Lung, 192(4), 601-608.
Kulnik, S. T., Birring, S. S., Hodsoll, J., Moxham, J., Rafferty, G. F., & Kalra, L. (2016). Higher cough flow is associated with lower risk of pneumonia in acute stroke. Thorax, 71(5), 474-475.
Monroe, M. D., Manco, K., Bennett, R., & Huckabee, M. L. (2014). Citric acid cough reflex test: establishing normative data. Speech, Language and Hearing, 17(4), 216-224.
Plowman, E. K., Watts, S. A., Robison, R., Tabor, L., Dion, C., Gaziano, J., ... & Gooch, C. (2016). Voluntary cough airflow differentiates safe versus unsafe swallowing in amyotrophic lateral sclerosis. Dysphagia, 31(3), 383-390.
Sakai, Y., Ohira, M., & Yokokawa, Y. (2020). Cough Strength Is an Indicator of Aspiration Risk When Restarting Food Intake in Elderly Subjects With Community-Acquired Pneumonia. Respiratory Care, 65(2), 169-176.
Sevitz, J.S., Borders, J.C., Dakin, A.E., Kiefer, B.R., Alcalay, R.N., Kuo, S., & Troche, M.S. (2022). Rehabilitation of airway protection in individuals with movement disorders: A telehealth feasibility study. American Journal of Speech-Language Pathology, 31, 2741-2758.
Sohn, D., Park, G. Y., Koo, H., Jang, Y., Han, Y., & Im, S. (2018). Determining peak cough flow cutoff values to predict aspiration pneumonia among patients with dysphagia using the citric acid reflexive cough test. Archives of physical medicine and rehabilitation, 99(12), 2532-2539.
Lisa Bloom, SLPD, CCC-SLP, BCS-S, is a speech-language pathologist at the University of Chicago Medicine working with adult and geriatric patients in acute care. Her clinical interests lie in dysphagia management for inpatient populations in addition to healthcare operations and process improvement.
Lea Rose Markham M.S., CCC-SLP, BCS-S, CLC is a dedicated speech-language pathologist at the University of Chicago Medicine, working primarily in acute care with patients across the lifespan. Clinically, Lea has a keen interest in dysphagia, traumatic brain injuries (TBIs), and tracheostomy management. Additionally, she is passionate about developing ethical healthcare systems and is committed to promoting equity throughout the hospital system.
