Keywords:
Myofunctional Therapy - Apnea - Mouth - Polysomnography
INTRODUCTION
Dry mouth on awakening is associated with increased severity and risk of Obstructive
Sleep Apnea (OSA) by 2.33 fold compared to primary snoring[1]. Continuous positive airway pressure (CPAP) is highly effective in preventing upper
airway collapse, but patient acceptance and adherence is often low. Oral appliances
designed to improve upper airway configuration prevent collapse by altering jaw and
tongue positions, holding the lower jaw more anteriorly. A mandibular advancement
device (MAD) fixes the mandible in a forward position, and is non-invasive compared
to surgery and more convenient to use than CPAP. Such devices are unsuitable for individuals
with few/no teeth; teeth are needed for fixation. Moreover, use of a MAD can cause
tooth discomfort[2] and temporomandibular joint pain[3]. Long-term use results in changes to the bite[4].
Oral myofunctional therapy (OMFT) has proven beneficial in treating OSA. For example,
oropharyngeal exercises that consisted of isometric and isotonic exercises involving
the tongue, soft palate, and lateral pharyngeal wall significantly reduced subjective
sleepiness, subjective sleep quality, snoring symptoms and neck circumference[5], and improved the quality of life whether applied alone or in association with CPAP[6]. Lip muscle training by way of a lip trainer mouth piece, as a form of OMFT, significantly
decreases the AHI by strengthening the lip muscles and increasing lip closure force
(LCF)[7]. However, the benefits of OMFT on objective sleep quality have not been investigated.
We present a case report of a patient who showed improvements in objective sleep and
sleep apnea after training.
Case report
A 20-year-old woman (body mass index, 18.6 kg/m[2]) complaint of heavy snoring, daytime sleepiness and dry mouth following waking.
Occlusion was normal without stomatognathic abnormalities or disorders in the maxillomandibular
joint. The patient had a history of bacterial endocarditis, childhood asthma and allergic
rhinitis. She was a mouth breather at night, but had no history of smoking or gastroesophageal
tract problems.
A MAD was routinely applied, but was discontinued due to temporomandibular joint pain.
Given the coexisting dry mouth and OSA[8], OMFT was implemented using an M-Patakara(®) lip trainer (Patakara, Tokyo, Japan) made from flexible, resilient plastic and rubber
([Figure 1]). LCF, LCFmax and LCFmin, obtained in a 10-s period, were reported as the mean of
3 measurements with a lip device (BHC-V01; Patakara Tokyo). In accordance with the
supplied instructions for use of the Patakara(®) ([Table 1]), training involved 4 sessions/day, 5 min/session for 2 months. LCF data showed
large improvements following training ([Table 2]).
Figure 1 Lip muscle training with the Lip trainer Patakara(®) Insert the device between teeth and lips. Press lips on the mouthpiece without teeth
contact.
Table 1. Instructiou.s for u sins Patakara.
Table 2. Sleep data before and after training
Full diagnostic polysomnography (Alice PDx; Respironics, USA) was conducted once before
(April 2015) and after OMFT (June 2015). Both tests were done under the same temperature
condition (in the same hospital sleep laboratory) and the tests were run by the same
clinical laboratory technician. Sleep data were scored according to AASM guidelines[9].
RESULTS
Mild OSA was diagnosed. Lip muscle training decreased the AHI and hypopnea index.
Training decreased the snoring rate and improved sleep quality and quantity ([Table 2]). The patient spent more time sleeping (TST) due to decreased wake time after sleep
onset (WASO), and experienced fewer arousals from sleep (arousal index). Improved
sleep quality was reflected by increased times spent in both REM sleep and stage N3.
OMFT vastly reduced stage N1 and returned N1 to near-normal levels (from 30.2 to 8.9
%TST). N2 increased substantially to that of regular sleepers ([Table 2]). The patient changed from mouth to nose breathing during sleep and ceased snoring
following OMFT, as reported by her partner.
DISCUSSION
In this case report of a patient with mild OSA, we showed that OMFT markedly decreased
the AHI and hypopnea index, improved objective sleep and subjective symptoms of snoring
and dry mouth.
OMFT increases LCFmax and LCFmin, suggesting improved lip muscle strength. The marked
drop in the hypopnea index (10.1 to 1.6 events/h) but minimal change in apnea index
(2.1 to 2.3 events/h) suggest an increased airway dimension/decreased airway resistance
that may involve movement of the tongue into the anterior-superior oral cavity with
lip closure, as the lip muscles are strengthened. Ishikawa et al.[10] showed that effective muscle strengthening was directly due to isometric training
with the M-Patakara lip trainer that placed a direct load on the muscles especially
the orbicularis oris and buccinator muscles.
In addition, Konishi[11] reported that strengthened mouth closure force along with coordinated contraction
of the genioglossus and geniohyoid muscles reflexively moved the tongue forward during
sleep. Lip muscle training prevented the base of the tongue from sagging which was
expected to relieve snoring and OSA.
However, we have not recorded electromyogram or other indices from the orbicularis
oris muscle to confirm our findings. We should investigate it based on this phenomenon
in the future. It should be emphasized that regular lip muscle training is necessary,
since muscle disuse will lead to detraining effects. Further research is also needed
to demonstrate increases in airway dimensions or decreases in airway resistance.
The SpO2 improvement was small, with a 2% increase. This small increment was not surprising,
since the patient suffered from mild OSA. This improvement was unlikely to be influenced
by changes in sleeping positions. The patient spent 63.9% of the sleep time in the
supine position in the first PSG test and 58.2% following lip muscle training, whereas
improvements in AHI and hypopneic index were 68% and 84% respectively ([Table 2]).
Importantly, the patient no longer experienced dry mouth on awakening. According to
Oksenberg et al.[1], experiencing dry mouth upon awakening almost always was a common symptom in OSA
patients referred for polysomnographic evaluation. In our opinion, the most plausible
explanation for the increased frequency of dry mouth complaint was the sleep time
spent with an open mouth. On the other hand, Izuhara et al.[12] reported that allergic rhinitis, a known risk factor for asthma onset, was often
accompanied by mouth breathing and dry mouth. Mouth breathing may bypass the protective
function of the nose and is anecdotally considered to increase asthma morbidity. However,
it is unlikely that rhinitis caused the dry mouth in this patient, since she grew
out of rhinitis at a young age. Thus dry mouth was no longer experienced following
OMFT, which resulted in mouth closure during sleep.
A strong link between dry mouth and OSA has been noted. Hochberg et al., in an elderly
population, found a prevalence of 11.5% complained of dry mouth most noticeable upon
awakening[13]. Additionally, Kales et al.[14] reported complaints of dry throat on awakening in 37 of 50 patients (74%) with severe
OSA. Sleep improvements observed in this study may be explained by an absence of dry
mouth during the sleep period. Although it is known that sleep variability may occur
from night to night[15], the consistent pattern of change with all sleep parameters ([Table 2]) suggested that sleep improvements were the results of lip muscle training. Notably,
we observed an improvement in TST of 40.8%, whereas there was no reported significant
first-night effect for the TST value[15]
,
[16].
The current findings suggest that OMFT may offer an alternative treatment in cases
of mild OSA. Given that the results are those of a case report, future clinical trials
to establish the efficacy of this modality may prove enormously beneficial, since
OMFT (through regular lip muscle training) is cheap and easily implemented.
In conclusion, OMFT in this patient with mild OSA markedly decreased the AHI and hypopnea
index, and improved objective sleep and subjective symptoms of snoring and dry mouth.
