Patients with respiratory muscle weakness as a result of neuromuscular-neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) or Duchenne Muscular Dystrophy (DMD) or spinal cord injuries may require airway clearance therapy to clear mucus and prevent lung infections.

By Lisa Spear


Muscle weakness in the airways may be overlooked in some patients who live with neuromuscular and neurodegenerative diseases. Since these patients are not able to take a deep breath, their cough may become weak. When a patient’s cough becomes too weak, mucus may collect in the airways and lead to a potentially dangerous infection, unnecessary emergency room visits, and even a stay in the intensive care unit. For some patients, this can all be avoided if proper airway clearance therapy (ACT) is administered as soon as a weak cough is detected. 


“This is a really important thing to talk about,” said Jeremy E. Orr, MD, pulmonary and critical care physician at UC San Diego Health in La Jolla, California. “A lot of these patients probably don’t get managed as aggressively as they should be. We could probably save everybody a lot of heartache and probably improve some outcomes by being a little bit more proactive.” 

Number of Patients Increasing

Patients with neuromuscular diseases are now living longer than ever, so the prevalence of these patients is on the rise, and they are appearing more frequently in emergency rooms with respiratory distress. A Canadian study published in Plos One found that, in both adults and children, neuromuscular disease prevalence is increasing and mortality rates are declining.[1] The results of the retrospective population-based study, which looked at population data during the period of 2003 through 2014 in Ontario, Canada, confirmed an increased survival rate of children and adults with neuromuscular diseases.[1]

In order to ensure that these patients get the care that they need, Orr suggested that hospitals should have a protocol for respiratory therapists to evaluate neuromuscular patients to identify those who could benefit from ACT. At UC San Diego Health, Orr helped to develop a protocol aimed at empowering the hospital’s RTs to identify these patients as early as possible with an initial assessment and to develop recommendations for management.

Without the ability to properly clear their airways of secretions, patients with neuromuscular and neurodegenerative diseases could experience potentially severe complications. Not to mention, muscle weakness could often leave this population unable to vocalize their discomfort, unable to tell their physician that they are unable to cough. This could lead clinicians to overlook the severity of their neuromuscular patients’ impaired cough, said Orr. “I think the awareness of these patients is much lower than in diseases like COPD or asthma, where I think people are much more comfortable making assessments on those patients,” said Orr, who specializes in neuromuscular respiratory weakness.  

“We need to start with recognizing these patients in the first place. A lot of these patients who have neuromuscular diseases, it is not appreciated the degree to which they have muscle weakness. Recognize that if you are seeing an ALS patient, they may have respiratory muscle weakness, if you are seeing a patient with muscular dystrophy, they may have respiratory muscle weakness,” said Orr, an assistant professor of medicine at UC San Diego School of Medicine.

Cough-Assist Therapies

The first line of defense against respiratory infections in these patients is typically mechanical insufflation-exsufflation (MI-E), a machine that slowly inflates the lungs, followed by an abrupt change to negative pressure, which produces a rapid exhalation. The machine simulates a cough, drawing up any mucus and fluids that may have accumulated in the airways. “For patients with a weak cough, they need cough augmentation, first and foremost. And for most patients, that is all they need,” said Orr. 

One of a handful of cough assist devices on the market, Philips Respironics CoughAssist T70, clears secretions from the central airways. In the process, it also captures device use data on an SD card, which healthcare providers can then review to better assess the patient’s adherence and build an effective treatment plan. 

The CoughAssist T70 uses a proprietary algorithm called the Cough-Trak that allows patients to initiate therapy through inhalation and determine the length of the therapy pause times increasing both comfort and compliance, according to information from the manufacturer. 

The predominant interface used to deliver MI-E therapy to neuromuscular patients is a facemask. Once the proper interface is selected for each patient, the clinician must pay attention to excessive leak around the interface during the insufflation cycle, according to Kevin McCarty, registered respiratory therapist and clinical services supervisor at Philips-RespirTech, a Philips company. Excessive leak leads to poor lung expansion and less effective therapy. The clinician can observe the chest expansion during the insufflation cycle, as well as monitoring Vti (Insufflation volume) on the CoughAssist T70 display to determine if a desirable lung expansion volume has been achieved. 

A common mistake when using cough assist devices is to set the pressure too low, explained Jonathan Finder, MD, a pediatric pulmonologist at Le Bonheur Children’s Hospital in Memphis, Tennessee. “If you have a very weak pressure, it is not going to be very effective for airway clearance, so I tend to do 35 and above for exhale pressures and since it doesn’t take a lot of pressure to inflate the lungs, I tend to set it a little bit lower on the inhale side,” said Finder, a professor of pediatrics at University of Tennessee Health Science Center. Finder recommends clinicians ask their patients to bring their cough assist devices to his office so that he can help them find a pressure setting that is tolerable and effective. 

Overall, cough assist devices are more effective than respiratory physiotherapy alone for critically ill patients on ventilators in the intensive care unit (ICU), according to research published in the peer-reviewed journal Respiratory Care in 2017.[2] This research shows that the combination of physiotherapy and mechanical cough assist resulted in airways that were twice as clear compared to patients who only received physiotherapy. The study’s authors wrote that the use of MI-E had the potential to decrease the risk of ventilator-associated pneumonia and shorten stays in the ICU.

Cough assist can also be administered with medical manufacturer Ventec Life Systems’ VOCSN, a portable life support device that combines five respiratory therapies: ventilation, oxygen, cough, suction, and nebulization. This device received approval from the US FDA last year and is now covered by Medicare. According to information provided by the manufacturer, caregivers can easily switch between therapies by pressing a button and no longer need to change the patient circuit between therapies.

Vest Therapy

Some patients may benefit from adding the additional therapy of high-frequency chest wall oscillation (HFCWO), which uses air pressure to create pulses against the chest wall to thin secretions and assist in its transport from the airways, explained McCarty. Once secretions are mobilized, the fluid may be removed either by the patient’s natural cough, if it is strong enough or suction from the cough assist device, McCarty said. “Both therapies help to mobilize and remove secretions, but from different parts of the respiratory system.” 

HFCWO may not always be covered by insurance, but it may be worth considering since there is evidence to show that it could improve clinical outcomes in some patients. A recent paper published in Annals of the ATS found that HFCWO therapy reduced inpatient admissions, length of stay, and inpatient costs for patients with various neuromuscular conditions.[3]

“It is important to consider the progressive nature of a disease when evaluating a patient’s cough effort and making decisions about which therapy will provide the longest-term benefit to the changing condition of the patient,” said McCarty. “In general, HFCWO therapy can be beneficial to patients requiring airway clearance who have not fully lost a natural cough, while CoughAssist is indicated for patients with a weak or nonexistent cough. They may also be used in combination with one another.”

The Right Device for the Right Patient

Another important consideration is to choose the right interface for each patient based on his or her current disease state. Some patients may be able to facilitate their own therapy while others will need a caregiver to administer the therapy to them. Choosing the correct interface (mouthpiece, mask or trach adapter) for therapy is an important consideration to ensure the best patient outcomes. For HFCWO, proper vest fitting and titrating to the appropriate pressure setting are key for the optimal patient outcomes, said McCarty.  

Some of these machines may initially be intimidating for some respiratory therapists, so hospital administrators might consider contacting the medical device manufacturers to conduct on-site trainings, Orr suggested. “I think it is definitely worth doing training sessions on using these devices,” said Orr. “It’s generating big inspiratory and expiratory pressure swings. It can seem a little intimidating, I think, for both patients and for respiratory therapists.”


RT

Lisa Spear is associate editor of RT Magazine. For more information, contact editor@RTmagazine.com.



References

  1. Rose L, McKim D, Leasa D, Nonoyama M, et al. Trends in incidence, prevalence, and mortality of neuromuscular disease in Ontario, Canada: A population-based retrospective cohort study (2003-2014). Plos One. 2019 Mar 26. Accessed at https://doi.org/10.1371/journal.pone.0210574
  2. Ferreira de Camillis ML, Savi A, Rosa RG, et al. Effects of Mechanical Insufflation-Exsufflation on Airway Mucus Clearance Among Mechanically Ventilated ICU Subjects. Resp Care. 2018 Dec;63(12)1471-1477. Accessed at http://rc.rcjournal.com/content/63/12/1471
  3. Lechtzin N, Wolfe L, Frick K. The Impact of High-Frequency Chest Wall Oscillation on Healthcare Use in Patients with Neuromuscular Diseases. Annals ATS. 2016 Jun;13(6). Accessed at https://doi.org/10.1513/AnnalsATS.201509-597OC