Exercise for velopharyngeal incompetence in subacute stroke
To our knowledge, this is the first study regarding the ef-
fect of treatment on VPI in patients with subacute stroke.
VPI, which is represented as nasal penetration, is
caused by inappropriate velopharyngeal closure. VPI is
one of the various symptoms of cough and swallowing
dysfunction after a stroke and is associated with orop-
haryngeal muscle weakness. Nasal penetration can be
considered clinically significant because it is associated
with serious upper respiratory tract infection, recurrent
or chronic sinus infection and cellulitis (23). Further-
more, post-stroke dysphagia is a risk factor, not only
for malnutrition and dehydration, but also for serious
complications that can delay functional recovery in
stroke patients, prolong hospital stays and cause death
(3, 4). Therefore, early detection of dysphagia and
appropriate treatment method is important in order to
treat each swallowing symptom (3, 4).
In previous studies, most dysphagia and/or coughing
dysfunction treatments have focused on prevention of
pharyngeal aspiration; few studies have investigated
effective treatment methods of nasal penetration or
VPI after stroke. Kummer (24). reported that speech
therapy was effective for reducing VPD, and another
study also showed that therapy using CPAP was use-
ful for VPD patients (14). The results of the current
study revealed that the study group that received ad-
ditional MIE exercise showed greater improvement
in both swallowing, especially nasal penetration, and
coughing function than did the control group. Using
a mechanism similar to CPAP therapy, MIE exercise
could increase the air pressure in the nasal cavities
during velopharyngeal closure, leading to strengthe-
ning of the oropharyngeal muscle, which is involved
in velopharyngeal closure in the swallowing process.
Strengthening of the oropharyngeal muscle may im-
prove the degree of nasal penetration in swallowing.
While swallowing and coughing, the same expiration-
related muscles are used. MIE exercise may strengthen
the expiration-related muscles. As a result, both swal-
lowing and coughing functions may have improved.
First, in terms of swallowing functions, this study
demonstrated that patients in the study group showed
significantly better degrees of nasal penetration of FDS
than did the patients in the control group. The FDS can
be used to quantify dysphagia severity and to identify
various physiological measures, including the aspira-
tion status and nasal penetration of food. To determine
the effect of MIE exercise on VPI, the FDS score was
divided into subsections and was analysed. We found
that only the degrees of nasal penetration of FDS sho-
wed statistically significant improvement in the study
group. There were no significant differences in the total
scores of FDS that indicated overall swallowing fun-
ction or in the swallowing score of the ASHA-NOMS
101
that indicated clinical severity. It was difficult to de-
monstrate the superiority of the MIE exercise therapy
for all kinds of dysphagia symptoms after stroke.
Secondly, in terms of coughing function, the current
study found that MIE exercise using cough assist was
also effective in increasing the values of PCF, thus
improving coughing function after a stroke. Clinically,
cough is an important protective mechanism for main-
taining a clear airway, removal of sputum or aspirated
food from the airways, and previous studies revealed
that patients with stroke could experience a decrease
in cough function (5–7). Kulnik et al. emphasized that
a high PCF value was associated with a lower risk of
pneumonia in acute stroke (25). Our previous study
suggested that voluntary coughing exercises could be
helpful for dysphagia to prevent pulmonary compli-
cations in patients with stroke (26).
According to a literature review, cough and swallow
pattern generators are tightly coordinated because they
share afferent and efferent pathways (6, 8, 10, 27). The
relationship between the coughing and swallowing
function in stroke patients has been demonstrated in
previous studies (5–9). Because the expiration-related
muscles used in coughing are also used in the swal-
lowing process, strengthening effect of the expiration-
related muscles through MIE exercise improves both
coughing and swallowing function in stroke patients.
Previous studies also found that MIE exercise could
improve coughing or swallowing function in other
diseases. Pitts et al. showed the impact of expiratory
muscle strength training on voluntary coughing and
swallowing function in Parkinson’s disease (27).
Another study demonstrated that MIE exercise impro-
ved coughing ability by increasing peak cough flow
(PCF) in patients with neuromuscular weakness (17).
Sivasothy et al. reported that cough function could be
improved by strengthening the muscles involved in
expiration through MIE exercise (28).
To our knowledge, this is the first study to de-
monstrate the effects of MIE exercise on VPI after a
stroke. Based on these findings, MIE exercise using
cough assist is expected to be applicable to patients
with post-stroke dysphagia and VPI. In addition, this
therapy is easy to use in the clinical setting and can also
be used at the bedside for patients who cannot move in
a wheelchair. Therefore, it is likely to be used widely
in the future with other various treatment methods.
Study limitations
This study has several limitations. First, the results
may not be generalizable to all stroke patients because
we enrolled patients who showed VPI in the results
of the VFSS. Secondly, the reduction in VPI in this
J Rehabil Med 51, 2019