Nose/mouth distribution of respiratory airflow in 'mouth breathing' children

Improving Nasal Airflow with a Novel Nasal Breathing Stent

Nasal obstruction requires close attention, as it is a risk factor for obstructive sleep apnea (OSA). This study evaluated airflow rates of our newly designed nasal breathing stent (NBS) compared with those of existing nasal dilators in 10 adult men. We hypothesized that the NBS would expand the nasal passage more than the other nasal dilators by means of airflow measurements. We compared airflow measurements between the NBS and three existing appliances and no appliance. Velocity measurements were recorded by analyzing 499 videographic images when each appliance was placed next to a steam generator at 0, 5, and 10 mm from the outlet port for airflow visualization. The peak nasal inspiratory flow (PNIF) rate was measured using an inspiratory flow meter. The NBS resulted in significantly higher airflow velocity measurements at all distances from the outlet port and a higher PNIF rate than the other appliances. Thus, the NBS offers a significantly decreased resistance to air movement compared with other appliances. Future in-depth investigations are required to demonstrate the use of NBS as a nasal dilator in conjunction with continuous positive airway pressure/oral appliance treatments in patients with OSA.

Assessment of Screening for Nasal Obstruction among Sleep Dentistry Outpatients with Obstructive Sleep Apnea

Oral appliances (OA), a common treatment modality for obstructive sleep apnea (OSA), are not suitable for patients with nasal obstruction. Rhinomanometry, the gold standard technique to assess nasal airway resistance, is not readily available in sleep dentistry clinics. We demonstrate the use of a portable lightweight peak nasal inspiratory flow (PNIF) rate meter to objectively assess nasal airflow and utilized the Nasal Obstruction Symptom Evaluation (NOSE) scale to subjectively assess nasal obstruction in 97 patients with OSA and 105 healthy controls. We examined the correlations between the following variables between the groups: demographics, body mass index, PNIF, NOSE scale scores, apnea-hypopnea index (AHI), minimum SpO₂ (SpO₂min), Mallampati classification, and Epworth Sleepiness Scale (ESS) scores. Patients with OSA had significantly lower PNIF values and higher NOSE scores than controls. In the patient group, PNIF was not significantly correlated with AHI, SpO₂min, Mallampati classification, or NOSE or ESS scores. Lower PNIF values and higher NOSE scores suggested impaired nasal airflow in the OSA group. As daytime PNIF measurement bears no relationship to AHI, this cannot be used alone in predicting the suitability of treatment for OSA with OA but can be used as an adjunct for making clinical decisions.

Tongue position after deglutition in subjects with habitual open-mouth posture under different functional conditions

OBJECTIVE

To test the null hypothesis of no significant differences in (1) the duration of the post-deglutory, cranial tongue rest position (CTP) between different functional orofacial conditions and (2) the presence or absence of an oral screen (OS) in subjects with a habitual open-mouth posture.

SUBJECTS

Twenty-nine subjects (aged 6-16; mean: 9.69 years; 13/16 girls/boys) were selected according to the inclusion criterion of a habitual, daytime open-mouth posture.

METHODS

Deglutition was screened at baseline during resting respiration using orofacial polysensography and simultaneous assessment of tongue-to-palate position and nasal airstream, during five functional intervals of 8 min each: F1 without instruction (RR); F2 the same, but including an oral screen (RROS); F3 with OS and the instruction to maintain a tongue-to-palate contact (IROS); F4 with OS and the instruction to perform tongue repositioning manoeuvres at the time of spontaneous swallowing (TRMOS); and F5 corresponds to F3 omitting OS (IR). Duration and frequency of deglutition were analysed descriptively as well as by anova and subsequent multiple comparisons, and the CTP was evaluated with chi-square tests and paired comparisons at a significance level of 5%.

RESULTS

Of 542 identified swallowing acts, 75% were accompanied by a post-deglutory CTP. Mean duration of CTP increased for functional conditions RR/1.01s > RROS/2.56s > IR/3.21s > IROS/6.53s > TRMOS/6.58s. The null hypothesis (1) was rejected in comparison of resting respiration (F1, F2) with IROS and TRMOS, whereas the use of an oral screen alone did not significantly prolong the duration of CTP.

Contribution of facial feature dimensions and velocity parameters on particle inhalability

To examine whether the actual dimensions of human facial features are important to the development of a low-velocity inhalable particulate mass sampling criterion, this study evaluated the effect of facial feature dimensions (nose and lips) on estimates of aspiration efficiency of inhalable particles using computational fluid dynamics modeling over a range of indoor air and breathing velocities. Fluid flow and particle transport around four humanoid forms with different facial feature dimensions were simulated. All forms were facing the wind (0.2, 0.4 m s(-1)), and breathing was simulated with constant inhalation (1.81, 4.3, 12.11 m s(-1)). The fluid flow field was solved using standard k-epsilon turbulence equations, and laminar particle trajectories were used to determine critical areas defining inhaled particles. The critical areas were then used to compute the aspiration efficiency of the mouth-breathing humanoid. One-tailed t-tests indicated that models with larger nose and lip features resulted in significantly lower aspiration efficiencies than geometries with smaller features, but the shape of the orifice into the mouth (rounded rectangle versus elliptical) had no effect on aspiration efficiency. While statistically significant, the magnitudes of differences were small: on average, the large nose reduced aspiration efficiency by 6.5% and the large lips reduced aspiration efficiency by 3.2%. In comparison, a change in breathing velocity from at-rest to heavy increased aspiration efficiency by an average of 21% over all particle sizes, indicating a much greater impact of aspiration efficiency on breathing rate in the facing-the-wind orientation. Linear regression models confirmed that particle diameter and breathing velocity were significant predictors to the aspiration fraction, while the facial feature dimensions were not significant contributors to a unifying model. While these effects may be less pronounced as the orientation changes from facing-the-wind, their impact confirms the importance of breathing velocity and, to a lesser extent, facial feature dimensions on exposure estimates in low freestream velocities typical of occupational environments.

Dry mouth upon awakening in obstructive sleep apnea

The aim was to assess the significance of dry mouth upon awakening as a symptom of obstructive sleep apnea (OSA). The participants were 668 consecutive adults referred for polysomnographic evaluation (PSG) because of snoring and suspected OSA, and 582 adults who were attending a general health check-up. Data were obtained from self-administered questionnaires and PSG evaluation. The participants were asked to answer the following question: 'During the last month, did you experience waking up in the morning with a dry mouth?'. The response scale consisted of five categories: 'never', 'rarely', 'sometimes', often', or 'almost always'. We classified patients as having dry mouth upon awakening complaint only if they reported experiencing the symptom 'almost always'. The prevalence of dry mouth upon awakening was twofold higher in patients with OSA (31.4%) than in primary snorers (16.4%, P < 0.001), and increased linearly from 22.4%, to 34.5%, and 40.7% in mild, moderate, and severe OSA respectively (P < 0.001). The prevalence of dry mouth upon awakening in the control group was 3.2%. Logistic regression results indicated that this symptom significantly differentiated OSA patients from primary snorers after adjusting for age, BMI, gender, hypertension, and other classical OSA symptoms (OR 2.33, 95% CI 1.34-4.07). Dry mouth upon awakening appears as a significant symptom of OSA. We suggest that increased sleep time spent with an open mouth is a likely explanation for these findings.

Partitioning of inhaled ventilation between the nasal and oral routes during sleep in normal subjects

The oral and nasal contributions to inhaled ventilation were simultaneously quantified during sleep in 10 healthy subjects (5 men, 5 women) aged 43 +/- 5 yr, with normal nasal resistance (mean 2.0 +/- 0.3 cmH(2)O. l(-1). s(-1)) by use of a divided oral and nasal mask. Minute ventilation awake (5.9 +/- 0.3 l/min) was higher than that during sleep (5.2 +/- 0.3 l/min; P < 0.0001), but there was no significant difference in minute ventilation between different sleep stages (P = 0.44): stage 2 5.3 +/- 0.3, slow-wave 5.2 +/- 0.2, and rapid-eye-movement sleep 5.2 +/- 0.2 l/min. The oral fraction of inhaled ventilation during wakefulness (7.6 +/- 4%) was not significantly different from that during sleep (4.3 +/- 2%; mean difference 3.3%, 95% confidence interval -2.1-8.8%, P = 0.19), and no significant difference (P = 0.14) in oral fraction was observed between different sleep stages: stage two 5.1 +/- 2.8, slow-wave 4.2 +/- 1.8, rapid-eye-movement 3.1 +/- 1.7%. Thus the inhaled oral fraction in normal subjects is small and does not change significantly with sleep stage.

Oronasal distribution of ventilation at different ages

The route of breathing, oral or nasal, is a determinant of the doses of inhaled pollutants delivered to target sites in the upper and lower respiratory tracts. We measured partitioning of ventilation, using a divided oronasal mask during a submaximal exercise test, in 37 male and female subjects who ranged in age from 7 to 72 y. The following four patterns of breathing were evident during exercise: (1) nasal only (13.5%), nasal shifting to oronasal (40.5%), oronasal only (40.5%), and oral only (5.4%). Children (i.e., 7-16 y of age) displayed more variability than adults with respect to their patterns of ventilation with exercise. Young adults (i.e., 17-30 y of age) who initially breathed nasally with exercise switched to oral ventilation at a lower percentage of the previously measured maximum ventilation (10.8%) than older subjects (31.8%). The partitioning of ventilation between the nasal and oral routes follows complex patterns that cannot be predicted readily by the age, gender, or nasal airway resistance of the subject.