Nose Breathing Research Articles

Mechanism of decongestant activity of α2-adrenoceptor agonists

The vascular bed in nasal mucosa of different species, including human, is highly vascularized and an extensive sinusoidal network of large capacitance vessels is present deep within the submucosa. When this network of venous sinusoids is engorged with blood, the swollen mucosa reduces the size of the airway lumen and congestion ensues. Nasal vasculature tone is strongly influenced by the sympathetic nervous system and the only drugs approved specifically to relieve vascular nasal obstruction are α-adrenoceptor sympathomimetic agents. Due to their vasoconstrictor action, the sympathomimetic decongestants oppose vasodilation, reducing nasal airway resistance and thus facilitating nose breathing. However, standard decongestants that are non-selective α-adrenoceptor agonists are associated with the potential for side-effect liabilities including hypertension, stroke, insomnia and nervousness. We propose than a selective α 2-adrenoceptor agonist, by acting preferentially on nasal venous capacitance vessels, will elicit decongestion with a reduced side-effect liability. In the present study, we evaluated the effects of the selective α 2-adrenoceptor agonist BHT-920 in a real-time tissue contractility assay using isolated pig nasal explants and in an in vivo cat model of congestion. The vasoconstrictor and decongestant effects of BHT-920 were compared to the non-selective α-adrenoceptor agonist epinephrine and the standard decongestant oxymetazoline. Our results showed that the α 2-adrenoceptor agonist BHT-920 preferentially contracts venous sinusoids confirming previous observations [Corboz MR, Varty LM, Rivelli MA, Mutter JC, Mingo G, McLeod R, et al. Effects of an α 2-adrenoceptor agonist in nasal mucosa. Arch Physiol Biochem 2003;11: 335–6, Corboz MR, Rivelli MA, Varty LM, Mutter J, Cartwright M, Rizzo CA, et al. Pharmacological characterization of postjunctional α-adrenoceptor in human nasal mucosa. Am J Rhinol 2005;19: 495–502] and displays decongestion without affecting blood pressure. Therefore, an α 2-adrenoceptor agonist, by causing constriction in the capacitance vessels of nasal mucosa, can produce nasal decongestion without the effects on blood pressure observed with the standard selective α 1-adrenoceptor and non-selective α-adrenoceptor sympathomimetic decongestants.

The use of mouth taping in people with asthma: a pilot study examining the effects on end-tidal carbon dioxide levels

Objectives The use of mouth taping, to encourage nose breathing, is currently being recommended by some Buteyko practitioners, but its effects on physiology are unknown. This preliminary study aimed to investigate the effects of mouth taping on end-tidal carbon dioxide (ETCO 2). Design Preliminary study with an experimental single group repeated measures design. Setting Research laboratory, university campus. Participants Nine university students and staff with mild stable asthma. Interventions Physiological data were recorded before and during two experimental breathing conditions: oral breathing and nasal breathing (encouraged by mouth taping), carried out on two separate occasions 5–14 days apart. Between visits, participants familiarised themselves with the mouth taping technique. Outcome measures Primary outcome was ETCO 2. Secondary outcomes were respiratory rate, pulse rate, oxygen saturation and lung function. Results There was an increase in ETCO 2 from baseline during both breathing conditions. The mean ETCO 2 for oral breathing was 4.4 kPa versus 4.7 kPa for nasal breathing, with mean difference of 0.3 kPa (95% confidence interval −0.2 to 0.8 kPa). It was also found that ETCO 2 increased more in ‘natural’ oral breathers than ‘natural’ nasal breathers. Conclusions The results of this pilot study provide data to power a larger study and suggest ETCO 2 may be increased in people with asthma during nasal breathing, particularly in those who normally primarily breathe through the mouth. The methodology was found to be acceptable to this sample of people with mild asthma.

ÇOCUKLARDA AĞIZDAN SOLUNUMUN AĞIZ DİŞ SAĞLIĞINA VE ÇEVRE DOKULARA ETKİLERİNİN DEĞERLENDİRİLMESİ EVALUATION OF THE EFFECTS OF MOUTH BREATHING ON ORODENTAL HEALTH AND SURROUNDING TISSUES IN CHILDREN

OZET Bu calisma, cocuklarda agizdan solunumun agiz dis sagligina ve cevre dokulara etkilerinin degerlendirilmesi amaci ile gerceklestirildi. Agizdan ve burundan solunum yapan 5-12 yaslari arasinda toplam 100 cocuk, df, df-s, DMF, DMF-S, kanama, plak indeksleri, marginal gingivitis, yuz sekli, burun, dudak, dil ve cene duruslari yani sira genel durum, uyku bozukluklari, aliskanliklar, davranis bozukluklari acisindan incelendi. Agizdan veya normal solunum yapan cocuklarda df, df-s, DMF, DMF-S degerleri arasinda anlamli farkliliklar (p>0.05) saptanmadi. Agizdan solunum yapan cocuklarin on grup sut dislerinde curuk gorulme sikliginin anlamli olarak daha fazla (p 0.05) were determined between df, df-s, DMF, DMF-S values in mouth and nose breathing children. Significantly (p<0.05) higher caries prevalence in anterior primary teeth was found in mouth breathing children; bleeding and plaque index values were determined higher (p<0.01) in nose breathers than mouth breathers. Significant differences were determined for facial form (p<0.001), nose form (p<0.01), lip posture (p<0.001), chin position (p<0.001), gummy smile (p<0.001) between children with mouth and nose breathing. In addition, in mouth breathing children snoring, sleep apnea syndrome, open mouth posture frequencies were found higher than control groups; however no significancy in behavioural disorders was observed between two groups. Data have demonstrated that mouth breathing could cause significant differences in children's face, nose, lip and chin morphologies; furthermore, it has been determined that other parameters regarding oral hygiene besides mouth breathing have also important roles on health of teeth and gingiva. Key Words: mouth breathing, health of tooth and gingiva

Can a discrete time‐frame for change in aerodigestive tract anatomy and function in human infants be identified?

The human aerodigestive tract (ADT) is the crossroads of breathing, swallowing, and vocalizing, yet precise data on when anatomic and physiologic changes occur is poorly understood. A central determiner of ADT function is laryngeal position, which until the second year is intranarial, allowing near simultaneous breathing and swallowing. While infants have been called “obligate” nose breathers, oral tidal respiration is evidenced by transient larynx/nasopharynx unlocking by the third month and even earlier. ADT development is hypothesized to be associated with clinicopathologies reflecting developmental errors. Tracking these changes may determine if a circumscribed time period in infancy exists during which structural changes in ADT development can be found consistently to occur. This project reviewed the literature of three documented infant ADT related clinicopathologies (sleep apneas, SIDS, excessive crying) to see if any nexus in occurrence frequency could be identified. In large scale trials, these three disorders were found to show a peak incidence between 2–4 months and dramatically decreased by 6 months. These data indicate that the critical period of infant ADT development may lie between 2–4 months. Whether these changes are functional, anatomical, or both remain unclear.

Particle Size Distribution and Inhalation Dose of Shower Water Under Selected Operating Conditions

Showering produces respirable droplets that may serve to deposit pollutants such as trihalomethane decontamination products, heavy metals, inorganic salts, microbes, or cyanoacterial toxins within the respiratory tract. The extent and importance of this route of indoor exposure depend on the physical characteristics of the aerosol as well as the pollutant profile of the source water. The purpose of this study was to characterize shower-generated aerosols as a function of water flow rate, temperature, and bathroom location. Aerosols were generated within a shower stall containing a mannequin to simulate the presence of a human. Using hot water, the mass median diameter (MMD) of the droplets inside the shower and in the bathroom were 6.3–7.5 um and 5.2–6 μm, respectively. Size was independent of water flow rate. The particle concentration inside the shower ranged from 5 to 14 mg/m3. Aerosols generated using cold water were smaller (2.5–3.1 μm) and concentrations were lower (0.02–0.1 mg/m3) inside the shower stall. No aerosols were detected in the bathroom area when cold water was used. The International Commission on Radiological Protection model was used to estimate water deposition in the respiratory tract. For hot water, total deposition ranged from 11 to 14 mg, depending on water flow rate, with approximately 50% of this deposited in the extrathoracic region during assumed mouth breathing, and greater than 86% when nose breathing was assumed. Alveolar deposition was 6–10% and 0.9% assuming oral and nasal breathing, respectively. The consequences deposition of shower water droplets will depend on the nature and extent of any pollutants in the source water.

Administration of Aerosolized Drugs to Infants by a Hood: A Three-Dimensional Numerical Study

Using a hood for aerosol delivery to infants was found to be effective and user-friendly compared to the commonly used face mask. The currently available hood design has an even greater potential in terms of efficiency, and a numerical simulation can serve as a tool for its optimization. The present study describes the development and utilization of a numerical simulation for studying the transport and fate of the aerosol particles and the carrier gas within a three-dimensional realistic representation of the hood and the infant's head. The study further incorporates realistic breathing patterns, with a longer expiration phase than an inspiration phase. Both nose and mouth breathing are simulated. While the base case assumes that the funnel that delivers the aerosol within the hood is perpendicular to the infant's face, more realistic scenarios include a funnel that is slanted with respect to the infant face, the infant's head taking a general position with respect to the funnel, and the funnel and the head being both tilted. A good agreement is found between computation and experimental results. As expected, the most efficient drug delivery, 18%, is achieved when the funnel is normal to the infant's face. The quantitative evaluation of different scenarios presented in this work increases the knowledge of physicians, nurses, and parents regarding the efficacy of the treatment, in terms of the actual amount of drug inhaled under various modes of function of the device.

Primary Care Evaluation of the Nose and Paranasal Sinuses

Primary Care Evaluation of the Nose and Paranasal Sinuses

호흡기 내 주기적 공기유동에 대한 PIV 계측

CT 스캔 데이터를 이용하여 호흡기의 컴퓨터 모델을 얻고, RP 를 이용하여 고형 모형으로 정교한 호흡기 유로 모형을 제작하였고, 호흡을 정확하게 모사하는 펌프를 만들었다. 사람의 호흡에 관한 생리적 데이터를 이용하여 캠을 제작하고 대형 피스톤 펌프를 만들어 사람의 호흡을 정확 하게 모사하였다. 이를 이용하여 생리적 주기를 갖는 호흡기 내 유동에 대한 PIV 결과를 획득하였다. 최초로 정확한 기하학적 형상 및 입구와 출구 조건 하에서 인후부와 기관 내의 공기 유동장의 데이터베이스를 확보하였으므로, 향후 기존의 단순화된 모델을 이용한 실험적 수치해석적 결과들을 검정하는데 활용될 것이며 호흡기 질환의 진단과 치료에 기여할 수 있는 생리학적 병리학적 데이터를 제공할 수 있으리라 생각된다. 또한 공해 물질, 유독 물질, 흡입 약품 등의 호흡기 내 흡착 현상 규명 등에도 활용될 수 있을 것으로 보인다.

Simulation of nasal flow by lattice Boltzmann methods

The lattice Boltzmann method is used to calculate the incompressible, viscous flow of air through a model of a nasal cavity, used in experiments. Computations are performed for steady flows at the inspiration and expiration phase of nose breathing. Computed pressure distributions and friction coefficients compare well with Navier–Stokes solutions from a finite-volume method on structured, curvilinear grids. The comparison with conventional Navier–Stokes solvers shows several advantages of the lattice Boltzmann method in particular for bio-medical flow problems. These are the fast grid generation, the simple, granular algorithm, suited for efficient parallelization and the high flexibility for implementing complex boundary conditions and additional transport equations. Lattice Boltzmann methods are therefore efficient candidates for fast flow predictions in the frame of computer-aided rhino-surgery.

The “silent” progression of a secondary paranasal malignancy in a laryngectomized patient

We discuss a 56-year-old white male patient who presented, 36 months after total laryngectomy for a primary vallecular carcinoma, with frontal headaches and left-sided nasal discharge since 5 months. Initially he was treated with antibiotics for a presumed sinusitis. In due course, bilateral paranasal swelling, left-sided eye pain and diplopia occurred. By then, physical examination and MRI imaging showed an irresectable left-sided paranasal tumour. He was then treated with palliative chemotherapy. Considerable diagnostic delay occurred in this metachronous second primary carcinoma, by the lack of nose breathing after total laryngectomy, thus not noticing nasal obstruction as a first sign. The rare occurrence of second primary tumour of the nose and paranasal sinuses in patients who underwent a laryngectomy obliges us to investigate vague nasal complaints by rhinoscopy and imaging.

Growth of the nasopharynx and adenoidal development in Brazilian subjects

The purpose of this research was to study the growth of the nasopharynx and adenoid development. Lateral cephalometric radiographs obtained from 320 white Brazilian subjects between 4 and 16 years of age were used. All the participants were nose breathers and none of them had previously undergone adenoidectomy. Tracings were made from the radiographs and cephalometric measurements were performed. The results showed that adenoid sagital thickness is larger in the age group 4 - 5 years and decreases progressively. There is a slight increase in the age group 10 - 11 years, but afterwards the decrease continues. However, the nasopharyngeal free airway space does not decrease in the age group 10 - 11 years, despite the increasing thickness of the adenoid. This is attributable to the downward displacement of the hard palate, resulting in an increase of the free airway space due to growth. Although the nasopharynx follows a growth pattern similar to that of the rest of the body, adenoid tissue does not. Adenoidal development seems to differ from that of other lymphatic tissues, showing a peculiar pattern that can be revealed when hypertrophy due to infections and allergies is eliminated.

Electromyographic analysis of the upper lip in nose and mouth breathers

The purpose of this research was to compare the electromyographic (EMG) activity of the superior belly of orbicularis oris muscle between individuals with Class II Division 1 malocclusion, nose breathers (Group 1) and mouth breathers (Group 2), having as a comparative parameter a control group of individuals with clinically normal occlusion (Group 3). The EMG recordings were obtained in resting position and in 16 movements. A statistically significant difference between Groups 1 and 2 was observed during puffing out with flaccid cheeks, dispelling of the lips' angle and saliva deglutition; between Groups 1 and 3 during puffing out with flaccid cheeks, posterior right and left clenching and saliva deglutition; between 2 and 3 during posterior right and left clenching. According to the normalized data the malocclusion groups (Groups 1 and 2) have a similar muscle behavior but when they are compared with the normal occlusion group there was a statistically significant difference between them. It can be concluded that, for this sample, the breathing mode did not influence the muscular behavior of the subjects with Class II division 1 malocclusion and that subjects with normal occlusion have more competent lips than the ones with Class II division 1 malocclusion.

Effects of upper airway anaesthesia on respiratory-related evoked potentials in humans

Cortical potentials evoked by mid-inspiratory occlusion arise from numerous receptors, many of which are probably within the upper airway. Their precise nature is not known. The aim of the current study was to improve knowledge of this by studying the effects of topical upper airway anaesthesia on respiratory-related evoked potentials. Respiratory-related evoked potentials were described through the averaging of electroencephalogram (EEG) epochs following mid-inspiratory occlusions (C3-CZ; C4-CZ). A total of 21 healthy volunteers (13 male, aged 22-52 yrs) were studied during mouth breathing, before and after topical upper airway anaesthesia (lidocaine). Moreover, 15 subjects were studied during nose breathing with and without anaesthesia. Six subjects were studied whilst inhaling L-menthol. Typical potentials were present in all the subjects, their components featuring normal amplitudes and latencies. The route of breathing and upper airway anaesthesia did not modify the EEG responses to inspiratory occlusions, qualitatively or quantitatively, during mouth or nose breathing. L-menthol had no effect. Upper airway receptors sensitive to topical anaesthesia are unlikely to contribute significantly to mid-inspiratory occlusion-evoked potentials. On the contrary, deeper receptors, such as joint and muscle receptors, could contribute dominantly to these potentials.

Aleitamento e hábitos orais deletérios em respiradores orais e nasais

OBJETIVO: A amamentação promove vários benefícios na criança, entre eles o favorecimento da respiração nasal. Neste estudo verificou-se a relação do padrão respiratório com o histórico de aleitamento e hábitos orais deletérios. FORMA DE ESTUDO: clínico com coorte transversal. MATERIAL E MÉTODO: A população foi constituída por 62 crianças, de 3 anos e 3 meses a 6 anos e 11 meses, as quais foram submetidas à avaliação otorrinolaringológica, para definição dos grupos respiradores nasais e orais e entrevista fonoaudiológica. A avaliação otorrinolaringológica constituiu-se dos seguintes exames: rinoscopia anterior, oroscopia e exame radiológico. Os pais das crianças foram questionados em relação à forma (natural e/ou artificial), e ao período de aleitamento, além da presença de hábitos orais deletérios (sucção e mordida). O teste Exato de Fisher foi utilizado para comparar os grupos em relação à presença ou ausência de hábitos e diferentes períodos de aleitamento. RESULTADOS: O período de aleitamento materno foi maior nos respiradores nasais concentrando-se no período de 3 a 6 meses de idade. Quanto ao uso de mamadeira, os resultados mostraram que a maioria das crianças de ambos os grupos utilizou-se deste tipo de aleitamento nos primeiros anos de vida, não apresentando diferença estatística entre os grupos (p=0.58). A presença de hábitos orais deletérios ocorreu de maneira marcante nos respiradores orais, evidenciando diferença estatisticamente significativa, entre os grupos, para os hábitos de sucção (p=0.004) e hábitos de mordida (p=0.0002). CONCLUSÃO: As crianças respiradoras orais apresentaram um menor período de aleitamento materno e um histórico de hábitos orais presentes comparadas às crianças respiradoras nasais.

Breast-feeding and deleterious oral habits in mouth and nose breathers

SummaryAimBreast-feeding promotes several benefits in childhood, among them favoring the nasal breathing. In the present study, the relationship between breathing pattern and the history of breast-feeding and of deleterious oral habits was determined.Study designclinical with transversal cohort.Material and MethodThe study population consisted of 62 children ranging in age from 3 years and 3 months to 6 years and 11 months who were submitted to otorhinolaryngologic evaluation to determine nasal and mouth breathers and to a speech language pathologic interview. The otorhinolaryngologic evaluation involved the following exams: anterior rhinoscopy, oroscopy and radiologic examination. The parents of the children were questioned about the form of feeding (natural and/or artificial), the duration of breast-feeding and the presence of deleterious oral habits (suction and biting). The Fisher exact test was used to compare groups regarding the presence and absence of habits and the different periods of breast-feeding.ResultsThe breast-feeding period was longer among nasal breathers and was concentrated in the period between 3 and 6 months of age. Regarding the use of bottle, the results showed that most of the children in both groups used this type of feeding during the first years of life, with no significant difference between groups (p = 0.58). There was a marked presence of deleterious oral habits among mouth breathers, with a statistically significant difference between groups regarding suction (p = 0.004) and biting habits (p = 0.0002).ConclusionMouth breathing children were breast-fed for a shorter period of time and had a history of deleterious oral habits compared to nose breathers.

A computer program for the simulation of fiber deposition in the human respiratory tract

As inhaled fibers may lead to a variety of lung diseases, detailed information on their deposition in the human respiratory tract is an indispensable requirement in medical science. In the work presented here, a Visual Basic ® computer program, termed FIBROS, is described which enables the simulation of fibrous particle deposition in both the extrathoracic region and different parts of the lung itself, including the results of published numerical studies on inertial/interceptional as well as diffusional and gravitational deposition. The input window of FIBROS includes the selection of specific breathing conditions by variation of the tidal volume and breathing cycle. Furthermore, the user is able to determine fiber properties such as diameter, aspect ratio, specific weight, and fiber orientation with respect to the air stream in the upper and lower airways of the lungs. Besides the offer of various deposition formulae for each region of the respiratory tract, thereby also allowing a distinction between mouth and nose breathing, the user may select between different morphometric datasets of the lung and respective airway scaling procedures. Analysis routines of FIBROS include the estimation of regional deposition fractions, thereby distinguishing between extrathoracic, bronchial, and acinar compartments, and a calculation of generation-by-generation deposition probabilities within tubular and alveolar structures. Preliminary results presented here should demonstrate the effects on fiber deposition due to variations of the breathing behaviour and the particle properties.

Breathing mode influence in craniofacial development

SummaryAimthe aim of this study was to evaluate the differences in facial proportions of nose and mouth breathing children using cephalometric analysis.Study designtransversal cohort.Material and MethodSixty cephalometric radiographs from pediatric patients aged 6 to 10 years were used. After otorhinolaryngological evaluation, patients were divided into two groups: Group I, with mouth breathing children and group II, with nose breathers. Standard lateral cephalometric radiographs were obtained to evaluate facial proportions using the following measures: SN.GoGn, ArGo.GoMe, N-Me, N-ANS, ANS-Me and S-Go; and the following indexes: PFH-AFH ratio: S-Go/N-Me; LFH-AFH ratio: ANS-Me/N-Me and UFH-LFH ratio: N-ANS/ANS-Me.ResultsIt was observed that the measurements for the inclination of the mandibular plane (SN.GoGn) in mouth breathing children were statistically higher than those in nasal breathing children. The posterior facial height was statistically smaller than the anterior one in mouth breathing children (PFH-AFH ratio). Thus, the upper anterior facial height was statistically smaller than the lower facial height (UFH-LFH ratio).ConclusionWe concluded that mouth breathing children tend to have higher mandibular inclination and more vertical growth. These findings support the influence of the breathing mode in craniofacial development.

Energetics of nose and mouth breathing, body size, body composition, and nose volume in young adult males and females

This research tests the relative ability of body size factors and sex to explain variation in nose volume and to explain metabolic measures during rest and moderate exercise in 50 young adults. It uses standard anthropometric measures plus two new measures of nose morphology (nose/face angle and nose volume) and evaluates body composition with a device for air displacement plethysmography. Standard physiological measures were obtained in nose-only and mouth-only breathing conditions with subjects at rest and using moderate exercise. A factor representing linear and bulk measures of body size and a factor representing lean body mass explain subjects' variation in nose volume, resting volume of oxygen consumed (VO2), and resting ventilation volume (VV) better than subject's sex does. By contrast, during exercise, sex explains VO2 and VV better than do body size factors, probably because hormone-mediated muscularity in males produced greater work output. Nose breathing was found to be more energetically efficient in most but not all subjects, but additional research is needed to explore this finding further. Qualitative comparisons between modes of breathing and the application of this research protocol to studies of climate-related patterns of nasal variation are discussed.

Effects of adenoidectomy and changed mode of breathing on incisor and molar dentoalveolar heights and anterior face heights

Abstract Background: Mouth breathing may affect facial form and the positions of the teeth. Objectives: To determine whether the increased dentoalveolar and facial heights found in mouth breathing children with enlarged adenoids are maintained following adenoidectomy and changed mode of breathing from mouth to nose. Methods: The subjects were Swedish children, either mouth breathers with nasal obstruction caused by large adenoids, or nose breathers. The children in the mouth breathing group were adenoidectomized at seven years of age and changed from mouth breathing to nose breathing. The unoperated subjects were age and sex matched to the operated subjects, and both groups were followed up again at 12 years of age. The incisor and molar dentoalveolar heights and anterior face heights, measured on lateral cephalometric radiographs, were compared prior to adenoidectomy and at 12 years of age. Results: Significant intra-group increases were found for all dentoalveolar heights and 5 out of 6 facial heights. Only the ratio of upper anterior to lower anterior face height in the controls was not different statistically. Upper posterior dentoalveolar height was significantly larger (p &lt; 0.05) in the adenoidectomized group compared with the controls at follow up, but not before adenoidectomy. Lower face height was significantly longer (p &lt; 0.001) in the adenoidectomized group compared with the control group initially, and at follow up (p &lt; 0.01). Initially, the ratio of upper face height to lower face height was significantly larger (p &lt; 0.001) in the control group than the adenoidectomized group, but the groups were similar at follow up. Small, but statistically significant, correlations were found between the changes in upper molar dental height and the mode of breathing (p &lt; 0.05) in the adenoidectomized group, and between the change in the ratio of upper to lower face heights and the mode of breathing (p &lt; 0.01). Conclusion: The changes in the dentoalveolar heights of the maxillary molars, and the ratio of the upper and lower anterior face heights seem to be associated with the change in mode of breathing from mouth to nose breathing after adenoidectomy.

Mouth Breathing Compromises Adherence to Nasal Continuous Positive Airway Pressure Therapy

Mouth leak compromises nasal continuous positive airway pressure (CPAP) therapy. We hypothesized that patients who breathe mainly through their mouths during sleep, compared to those who breathe mainly through their noses, would have more mouth leak during CPAP and therefore lower adherence to CPAP. A case-control study to compare adherence to CPAP at 1 year in mouth breathers (MBs) with nose breathers (NBs). University teaching hospital with a sleep laboratory. Fifty-one CPAP-naive patients (4 women), with a respiratory disturbance index (RDI) > 15/h. Of the 51 patients, 30 patients breathed through their mouths (mouth breathing > 70% of total sleep time [TST]), and 21 patients breathed through their noses (mouth breathing < 30% of TST). MBs between 30% and 70% of TST were excluded. Overnight polysomnography was performed at baseline, during CPAP titration, and at 3 months. Patients were followed up for 1 year after beginning CPAP. To measure mouth breathing, nasal and oral thermistors during polysomnography were separated by a 3 x 6-cm silicon transverse diaphragm. RDI decreased from (mean +/- SD) 37.8 +/- 21.5 to 1.8 +/- 2.6/h at 3 months. Throughout the study, adherence to CPAP (mean daily CPAP use in hours) was better in NBs. Most NBs (71%) but only 30% of MBs used CPAP daily for > 4 h at 1-year follow-up. Mouth breathing decreased significantly from 84 +/- 8.9% at baseline to 22 +/- 14.4% at 3 months. Patients with moderate-to-severe sleep-disordered breathing and a high percentage of mouth breathing during sleep were less adherent to CPAP therapy than patients exhibiting a low percentage of mouth breathing.