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indicates symptoms caused by inappropriate velopha-
ryngeal closure, and is associated with neurological
issues, including stroke. VPI is one of 3 categories of
velopharyngeal dysfunction; velopharyngeal mislear-
ning, velopharyngeal insufficiency and VPI (12, 13).
Few studies have investigated effective treatment
methods of nasal penetration or VPI after stroke. One
study showed that treatment with continuous positive
airway pressure (CPAP) was effective in patients with
VPI (14). CPAP therapy increased the air pressure
in the nasal cavities during velopharyngeal closure,
leading to strengthening the oropharyngeal muscles,
which might be involved in velopharyngeal closure
(15, 16).
Mechanical inspiration and expiration (MIE) exer-
cise is a method for improving coughing ability in pa-
tients with respiratory muscle weakness. Chatwin et al.
reported that MIE exercise improved coughing ability
by increasing peak cough flow (PCF) in patients with
neuromuscular weakness (17). Like the CPAP therapy,
MIE exercise also might strengthen the oropharyngeal
muscles, which are involved in velopharyngeal closure.
As swallowing and coughing functions are closely
related by sharing the same expiration-related muscles
(5–9), we hypothesized that MIE exercise may affect
both swallowing, especially nasal penetration and
coughing functions, in patients after stroke. The aim
of this study was to investigate the therapeutic effects
of MIE exercise using mechanical cough assist on VPI
in patients with subacute stroke.
MATERIALS AND METHODS
Subjects
This study was designed as a pilot randomized controlled study
and was performed in the rehabilitation centre of a university
hospital, specifically a regional cerebrovascular centre from
May 2015 to July 2017. No formal sample size calculation was
performed. Patients with subacute stroke who had swallowing
difficulty were evaluated by a video fluoroscopic swallowing
study (VFSS). Among these the patients who showed VPI on
VFSS were enrolled in this study. VPI could be shown as nasal
penetration on VFSS (Fig. 1) due to inappropriate velopharyng-
eal closure. Of these patients, those susceptible to barotrauma
(atmospheric pressure injury) due to pulmonary diseases, such
as emphysema, those with a previous stroke, those with pha-
ryngeal structural abnormalities, those unable to cooperate for
MIE exercise due to deteriorated cognitive function or mentality,
and those with medical conditions that could affect their swal-
lowing ability were excluded from this study.
Fig. 1. Nasal penetration on video fluoroscopic swallowing study (red
circle).
group was administered conventional swallowing rehabilitation
therapy only.
The study group was administered MIE exercise once daily
using the CNS-100 Cough Assist® (SungdoMC, Seoul, Korea)
and conventional swallowing rehabilitation therapy twice a
day. The treatment procedures for inspiration were as follows:
starting positive pressure was 15–20 cm H 2 O, increased to 40
cm H 2 O according to the patients’ condition. Inspiration lasted
2 s, or longer if required, and was titrated for patient comfort.
The treatment procedures for expiration were as follows: starting
with the expiration (negative) pressure was similar to the inspi-
ration pressure, and then the negative pressure was increased
to 10–20 cm H 2 O above the positive pressure. Negative pres-
sure was then held for 3–6 s, simulating the airflows that occur
naturally during the cough. The patient was then instructed to
coordinate their respiratory rhythms according to those of the
cough assist machine (Fig. 2).
Conventional dysphagia rehabilitation consisted of oral motor
and sensory stimulation, neuromuscular electrical stimulation
of the suprahyoid muscle, and oral and lingual exercises to
Intervention protocol
All of the enrolled patients were randomly assigned to 2
groups using a table of random numbers. The study group was
administered additional MIE exercise therapy as well as con-
ventional swallowing rehabilitation therapy, while the control
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Fig. 2. Study group received mechanical inspiration and expiration
exercise using mechanical cough assist machine.