Let’s talk aspiration. I hate to even bring it up. It is a word that makes physicians, speech-language pathologists (SLPs), and many people living with swallowing disorders cringe. Why? If you have lived with dysphagia or cared for someone who has, you know that dysphagia and aspiration can be linked to potentially life-threatening complications, like aspiration pneumonia. So, when we talk about aspiration, we want to talk about reducing it. There are several causes of aspiration and a dysphagia treatment program needs to target those issues specifically to be effective. One reason food and/or liquid can enter the lungs is due to poor airway protection. This article reviews the emerging evidence that expiratory muscle strength training (EMST) is one treatment that can improve airway protection.
Swallowing is an intricate process involving multiple sensorimotor responses to efficiently move food and liquid from the mouth to the stomach, while bypassing the airway/lungs. Because swallowing and breathing share a common system, the airway closes during the swallow to prevent aspiration of food and liquid into the lungs. Airway closure is impaired in some people with dysphagia. Fortunately, we have a range of actions to protect our airway from food and liquid invasion, ranging from swallowing (prevention) all the way to cough (ejection). In the event food and/or liquid enters the airway, a cough is produced to force the material out and prevent it from entering the lungs. Unfortunately, there is evidence that shows some people with swallowing disorders have a reduced cough reflex. Because both cough and swallowing are important parts of airway protection, SLPs are increasingly interested in assessment and treatment of both cough and swallow as part of a comprehensive dysphagia program.
How Does it Work?
Expiratory muscle strength training targets muscle groups involved in airway protection in two ways.
- Strengthening swallowing muscles to improve swallow safety. During EMST, a group of muscles in the neck called the suprahyoid muscles are activated in a similar way to that of swallow-based exercises. Research has found that EMST results in increased hyoid displacement and opening of the upper esophageal sphincter (UES) to allow the food and/or liquid to flow through the throat and toward the stomach. These improvements led to a reduction in penetration-aspiration scale (PAS) scores which measure airway invasion (Plowman et al., 2016, Troche et al., 2010). After completion of an EMST program, airway protection improved in several populations, including:
- Parkinson’s disease (Pitts et al., 2009; Troche et al., 2010)
- Amyotrophic Lateral Sclerosis (ALS) (Plowman et al., 2016)
- Stroke (Arnold & Bausek, 2020; Eom et al., 2017; Moon et al., 2017; Park et al., 2016)
- Head and neck cancer(Hutcheson et al., 2018)
- Strengthening the expiratory muscles to improve cough strength. Contraction of the expiratory muscles creates the force to expel material from the airway. This is important because decreased expiratory peak flow and voluntary cough measures have been found to be associated with dysphagia and aspiration. There is emerging evidence that EMST improves cough-related measurements in the following populations:
- Multiple sclerosis (Chiara et al., 2006; Gosselink et al., 2000)
- Parkinson’s disease (Pitts et al., 2009)
- ALS (Plowman et al., 2016)
- Spinal cord injury (Roth et al., 2010)
- Stroke (Menezes et al., 2016)
- Sedentary elderly (Kim et al., 2009)
The EMST Treatment Program:
In most EMST research studies, a pressure threshold device is used for treatment. It is a spring-loaded device with an adjustable valve. Patients are trained to blow forcefully through the device and the valve is adjusted progressively to increase the load on the expiratory muscles. Think of it like increasing weight on the barbell at the gym. If the valve is set too high, the patient will be unable to blow air through the device. If it is set too low, it will not require enough effort to gain muscle strength. The program should be individualized to the patient. An example of an initial EMST session may include the following:
- SLP measures the patient’s maximum expiratory pressure (MEP), selects an appropriate device, and sets the device at a recommended percentage of MEP (ex. 75% of MEP)
- Patient is trained to use the device.
- Place nose plug (if needed to prevent air loss through the nose).
- Take a deep breath and hold.
- Place the device in your mouth behind your teeth and place lips tightly around mouthpiece.
- Blow forcefully through the device, holding cheeks to maintain a tight seal, if needed.
- Rest at least 15-30 seconds before repeating.
- SLP prescribes patient a schedule (ex. 5 repetitions, 5 times per day for 25 total per day, 5 days per week)
The SLP reassesses throughout the program and changes valve levels as the patient progresses. After treatment goals are reached, the SLP may recommend a maintenance program to maintain results.
Contraindications for EMST should be discussed with the physician prior to treatment. These are specific to the individual and will vary based on medical conditions and history. Those for whom the Valsalva maneuver (e.g., “bearing down”) is contraindicated may be more likely to be excluded from EMST use. While a study on healthy adults showed the use of EMST was less effortful and shorter in duration than a Valsalva maneuver, those with more complex cardiovascular or pulmonary diagnoses may be affected differently than a healthy adult.
Advantages and Disadvantages of EMST:
- Research has shown improved airway protection for multiple populations. Success of EMST in activating both swallow and cough musculature has promise for success in other populations that have not been researched yet.
- Improvement in certain populations has been seen in as little as 4 weeks using an intensive protocol (75% MEP, 25 times per day, 5 days per week).The program follows principles of exercise science and instructions are easy to follow.
- EMST may be a first step to address airway protection for people who aspirate and are at risk of pneumonia, as the program does not require the consumption of food or liquid.
- EMST may be feasible for those with neurodegenerative diagnoses to complete, when adjusted for effort.
- EMST trains the muscles of the cough and swallow by blowing through a device, but not through the pattern of an actual cough or swallow. The expiratory muscles are just one important factor in a cough, so if other phases of the cough are impaired, EMST alone will not result in an effective cough. Similarly, suprahyoid muscle contraction is just one component of a swallow. Strengthening this muscle group alone may not resolve aspiration if other sensorimotor issues are the cause of an individual’s swallowing difficulty. EMST can be considered an adjunct therapy, rather than a stand-alone treatment.
- Research is still growing to support effectiveness and determine the best training protocol.
When we talk about aspiration, we want to talk about reducing it because it can have life-threatening complications. The more effective treatment techniques that SLPs have to treat dysphagia and reduce aspiration, the more we can look to a solution and reduce the fear those words provoke. Improving airway protection is one important goal of dysphagia therapy to reduce aspiration of food and liquid into the lungs. Evidence is growing in support of EMST to target airway protection through strengthening muscles of the cough and the swallow. For best results, it is important that patients and SLPs who are guiding treatment have a thorough understanding of what populations most benefit from EMST and prescribe an appropriate treatment program.
Kari Hovorka M.S., CCC-SLP, BCS-S is an ASHA certified speech-language pathologist (SLP) and board-certified specialist in swallowing and swallowing disorders. She currently works with adults recovering from critical illness at a long term acute care hospital (LTACH). She began her career serving medically complex children as a clinical SLP and therapy manager. Over the past decade she has been a volunteer with multiple organizations supporting SLPs and the people they serve, including: SDSLHA, the ASHA Advisory Council, and CLASP International. She has been awarded the ASHA Award for Continuing Education (ACE) 6 times for her commitment to lifelong learning. Kari is passionate about sharing evidence-based practice with other SLPs, patients, and caregivers to help people with dysphagia meet their goals.