Nose Breathing Research Articles

Postural Changes in Nasal and Pulmonary Resistance in Subjects with Asthma

Introduction. Subjects with asthma frequently have nasal symptoms and complain of orthopnoea but airflow resistance is usually only assessed during oral breathing and while seated. Method. We have used a forced oscillation technique to measure total respiratory resistance (Rrs) at 6Hz during mouth breathing (Rrs,mo) and during nose breathing (Rrs,na) in the sitting and supine postures; resistance of the nasal airway (Rnaw) was estimated as Rrs,na − Rrs,mo. Forced oscillations were applied during normal tidal breathing and the mid‐tidal lung volume (MTLV) was determined for each breathing route and posture. Subjects. Three groups of subjects were studied: 10 normal subjects without lung or nasal disease (N; five males, mean age 33.5 [range 23–58] years, mean FEV1 105%pred, FEV1/VC 86%); seven subjects with asthma alone (A; four males, 40.3 [23–57] years, mean FEV1 66%pred, FEV1/VC 74%); 10 asthmatic subjects with nasal obstructive symptoms (AN; six males, 62.8 [38–80] years, mean FEV1 56%pred, FEV1/VC 75%). Results. In all three groups of subjects, mean Rrs,mo and Rrs,na were higher in the supine than sitting posture. In normal subjects the increase in supine Rrs,mo was associated with a 0.6 liter fall in MTLV. In asthma supine Rrs,mo increased despite a much smaller fall in MTLV; supine increases in Rrs,na were particularly large in presence of nasal disease. Discussion. Values of airflow resistance are 2–3 times higher in both normal and asthmatic subjects when breathing via the nose and supine than under normal laboratory conditions of oral breathing and seated.

Assessment of Upper Respiratory Tract and Ocular Irritative Effects of Volatile Chemicals in Humans

ABSTRACTAccurate assessment of upper respiratory tract and ocular irritation is critical for identifying and remedying problems related to overexposure to volatile chemicals, as well as for establishing parameters of irritation useful for regulatory purposes. This article (a) describes the basic anatomy and physiology of the human upper respiratory tract and ocular mucosae, (b) discusses how airborne chemicals induce irritative sensations, and (c) reviews practical means employed for assessing such phenomena, including psychophysical (e.g., threshold and suprathreshold perceptual measures), physiological (e.g., cardiovascular responses), electrophysiological (e.g., event-related potentials), and imaging (e.g., magnetic resonance imaging) techniques. Although traditionally animal models have been used as the first step in assessing such irritation, they are not addressed here since (a) there are numerous reviews available on this topic and (b) many rodents and rabbits are obligate nose breathers whose nasal passages differ considerably from those of humans, potentially limiting generalization of animal-based data to humans. A major goal of this compendium is to inform the reader of procedures for assessing irritation in humans and to provide information of value in the continued interpretation and development of empirical databases upon which future reasoned regulatory health decisions can be made.

Ronchopathie chronique et syndrome de l'apnée-hypopnée obstructive du sommeil chez l'enfant

The problems children have in sleeping are manifold; the gamut of disorders that have been described ranges from simple, occasional snoring with no accompanying complications, through the syndrome of increased blockage of the upper airways to the obstructive sleep apnea-hypopnea syndrome (OSAHS) where respiratory difficulties accompanied by hypoxemia, hypercapnia and structural sleep difficulties. Mouth breathing and chronic snoring occur frequently in children, with the incidence of snoring, identical for both sexes, varying between 3.2 and 27%. Difficulties in sleeping begin between the ages of the 3 and 9, peaking between 3 and 6. These results demonstrate, in a general way, the disparity between growth of the adenoids and tonsils, and upper airway growth. A differential diagnosis between the various pathological possibilities is based on the observed clinical signs and symptoms, analysis of cephalometric radiographs, polysomnography, a nocturnal cardio-respiratory polygraph and a video film taken during sleep. Snoring is the most characteristic sign of OSAHS in children. We do not yet have available any synthetic study that would sum up results of studies of sleep disorders in children. Nevertheless, we can define obstructive sleep apnea in children as the partial or total cessation of nose and mouth breathing for a period double that of the normal respiratory cycle. Classical treatment of children who suffer from severe respiratory difficulties during sleep, after identification of the etiology of the problem, consists of surgical removal of the adenoids or tonsils and, in certain, continuous positive pressure to assist breathing. The authors of this article have worked with 137 patients between the ages of 6 and 9, 77 of whom were chronic snorers with an average age of 7 years 6 months. The average age of the control group of 60 children was 7 years 2 months. We collected clinical data, medical histories, and distributed a questionnaire to determine individual sleep and vigilance behavior of each child in the sample. To complete our evaluation, we made a cephalometric analysis of facial type, antero-postero skeletal pattern, upper airways, and hyoid bone position. The symptom that we encountered most frequently in young chronic snorers was agitated and uneasy sleep, sometimes accompanied by bed-wetting and cervical hyperextension. We often found daytime symptoms of hyperactivity and personality or behavioral problems. Hypertrophy of the adenoids, the adenoidal fascia, and the tonsils were also frequent clinical signs. The cephalometric analyses often showed the patients to be of the dolichocephalic facial type, often with the mandible rotated posteriorly. The children were as likely to be classified as Class II owing to retrognathic mandibles as to be Class III owing to maxillary deficiencies or mandibular excess. At the level of the upper airways, it appears that the development of snoring can be explained by a reduction in the dimensions of the upper pharynges accompanied by an increase in the dimensions of the middle and lower pharynges.

Anatomy of oral respiration: morphology of the oral cavity and pharynx.

The anatomical states of the oral cavity and pharynx during mouth breathing in children with adenoid hypertrophy and in adults confirmed the speculation that mouth breathing is disadvantageous compared with nose breathing. In addition, comparison of the anatomical state between wakefulness and sleep in normal adults showed slight depression of the tongue root and slight narrowing of the oropharynx and hypopharynx during sleep. Obstructive sleep-disordered breathing occurs due to a variety of factors, such as paranasal sinus disease, tonsil and adenoid hypertrophy, hypertrophy and morphological abnormalities of the soft palate and palatine uvula, low-set soft palate, micrognathia, macroglossia, obesity and tongue root depression. Narrowing or obstruction of the middle pharynx and hypopharynx is more marked in patients with obstructive sleep-disordered breathing than in normal people and is especially marked during sleep. Therefore, morphological (i.e. anatomical) changes during mouth breathing may provide useful information for evaluating the pathology of snoring and sleep apnea.

The Nose and Sleep-Disordered Breathing

The Nose and Sleep-Disordered Breathing

The effect of head posture on the pharyngeal airway space (PAS)

The purpose of this study was to investigate the relationship between cranio-cervical inclination and pharyngeal airway space (PAS) by measuring these parameters at different head postures in the same subjects and to obtain a regression equation to correct the values measured. Fifty lateral cephalometric radiographs taken at five different head postures per individual were obtained from ten adults (seven males and three females) aged from 25 to 30 years with nose breathers and Class I occlusion. The changes in cranio-cervical inclination produced by head extension were correlated with changes in the variables describing the PAS. The OPT/NSL (cranio-cervical inclination in the second vertebrae) and C3-Me (distance between the third vertebrae and the Menton) correlated strongly with PAS-TP (the most proximal distance measured between the posterior pharyngeal wall and the tongue base) in the pharyngeal airway space (r=0.807 and 0.854 respectively). The regression equations were Y=−27.177+0.39 X (Y=PAS-TP, X=OPT/NSL), andY =−21.105+0.402 X (Y=PAS-TP, X=C3-Me), respectively. From these equations we could conclude that an increase of 10° in OPT/NSL or 10mm in C3-Me increased the pharyngeal airway space (PAS-TP) by about 4mm.

Endoscopic marsupialization of congenital nasolacrimal duct cyst with dacryocoele.

A congenital nasolacrimal duct cyst is an uncommon condition in the newborn usually treated by ophthalmologists. Prolapse or expansion of the cyst into the nose may lead to respiratory distress and difficulty in feeding as newborns are obligate nose breathers, which needs the involvement of the Otolaryngologist in diagnosis and management. The authors report a series of 8 children presenting with a congenital nasolacrimal duct cyst and dacryocoele and highlight the importance of endoscopic nasal examination of newborns presenting with respiratory problems. Diagnostic studies included intranasal endoscopy and CT scanning of the nasolacrimal system and nose. All the patients were treated by endoscopic marsupialization of the cyst. Nasolacrimal duct abnormality should be considered in the differential diagnosis of neonatal respiratory distress and nasal obstruction. Nasal endoscopy is essential in the work-up of all children with nasal obstruction and respiratory distress. CT scanning is the investigative method of choice. Endoscopic marsupialization followed by lacrimal duct irrigation is effective in the treatment of congenital nasolacrimal duct cyst and results in complete resolution of symptoms.

Dentofacial morphology of mouth breathing children.

The relationship between dentofacial morphology and respiration has been debated and investigated from various approaches. The aim of this study was to verify the skeletal and dental relationship of mouth and nose breathing children. Thirty-five children, 7 to 10 years of age, were submitted to orthodontic and otorhinolaryngologic evaluations and were separated into 2 groups: 15 nose breathers and 20 mouth breathers. Each subject underwent a cephalometric radiograph analysis. Statistical analysis (Mann-Whitney U test) indicated that changed mode of breathing was associated with 1) maxillo-mandibular retrusion in relation to the cranial base in the mouth breathers; 2) the SNGoGn and NSGn angles were greater in the mouth breathing group; 3) incisor inclination in both jaws and the interincisal angle were not different between groups. There was no statistically significant difference in the maxillary and mandibular molar heights between the nose breathers and mouth breathers.

Inhalability of large solid particles

Large particles (10– 150 μm) with systemic toxicity pose a health risk if inhaled regardless of where they deposit. This research seeks to better define particle inhalability, the fraction of airborne particles that are inhaled as a function of particle size. Measurements of inhalability were made for solid particles using a 1.6×1.6×5-m wind tunnel. Tunnel air velocities were 0.4, 1.0, and 1.6 m/ s . A full-size, full-torso mannequin was used to collect dust entering either the mouth or nose for breathing at minute volumes of 14.2, 20.8, and 37.3 l . The mannequin either faced the oncoming wind or rotated slowly (0.06 rpm) during sample collection. At the test section, air velocity was uniform to within 10% and aerosol concentration was uniform to within 15% over the central 80% of the cross section. Orientation-averaged inhalability for mouth breathing was higher than the inhalable particulate mass (IPM) sampling criterion for particles smaller than 35 μm and lower than the criterion for larger particles, leveling off at about 30% for particles >70 μm . Facing-the-wind mouth inhalability showed the same trend as the IPM sampling criterion, but the measured values were 25% higher. Wind velocity and breathing pattern had little effect on inhalability for the range of conditions examined here. Orientation-averaged inhalability for nose breathing dropped quickly with particle size reaching less than 10% at 60 μm . Facing-the-wind nose inhalability was slightly increased for particles smaller than 60 μm compared to orientation averaged inhalability for nose breathing.

A comparison of nasopharyngeal endoscopy and lateral cephalometric radiography in the diagnosis of nasopharyngeal airway obstruction

Two auxiliary methods of diagnosing nasopharyngeal airway obstruction were compared. Cephalometric radiography and nasopharyngeal videoendoscopy were evaluated for efficacy in terms of reproducibility and validity. Thirty orthodontic patients (7 to 12 years of age) seeking otorhinolaryngologic treatment for mouth breathing, or mouth and nose breathing, had nasopharyngeal endoscopy and radiographic examinations performed on the same day. Two otorhinolaryngologists analyzed the results. Nasopharyngeal endoscopy was more reliable in identifying all the obstructive nasopharyngeal processes. Endoscopy obtained kappa index scores of almost perfect agreement for diagnosis of posterior nasal septum deviation, of substantial agreement for anterior nasal septum deviation and lower turbinate hypertrophy, and of moderate agreement for middle turbinate hypertrophy. Lateral cephalometric radiography obtained scores of perfect agreement for imaging hypertrophy of the middle turbinate, of almost perfect agreement for imaging hypertrophy of the posterior portion of the inferior turbinate, and of substantial agreement for imaging hypertrophy of the inferior turbinate. Radiographic diagnoses of hypertrophy of the middle and lower turbinates exhibited high sensitivity and low specificity when compared with diagnoses by nasopharyngeal endoscopy. (Am J Orthod Dentofacial Orthop 2001;120:348-52)

Factors influencing the shape of the inspiratory flow

An index (IS), quantitating the departure of the inspiratory flow profile (IFP) from the rectangular one, i.e. the optimal profile (IS=0), was computed from pneumotachograms recorded in 26 normal, anesthetized subjects breathing spontaneously through the endotracheal tube (ETT) or face mask (FM) with or without added resistances (R) and in 27 awake subjects breathing through the mouth and FM in the supine and seated posture at rest and during exercise (40 W) on a cycloergometer, through the nose and FM, and through the mouthpiece (MP). During anesthesia, IS decreased with R both while breathing through the ETT (ΔIS=−0.037±0.006 (SE); P<0.001) and FM (ΔIS=−0.054±0.008; P<0.001). This indicates that (a) the change of IFP towards the optimal shape is reflex in nature and related to the dynamic inspiratory load, and (b) tracheobronchial mechanoreceptors and inspiratory muscles are involved in this response. The reflex is also operative in awake subjects, since IS decreased whenever the inspiratory dynamic load was increased, as on turning from seated to supine posture (ΔIS=−0.024±0.003; P<0.001), shifting from mouth to nose breathing (ΔIS=−0.034±0.003; P<0.05), from rest to mild exercise (ΔIS=−0.066±0.005; P<0.001). The different IS value between FM and MP breathing (ΔIS=0.036±0.004; P<0.001) indicates, however, that other factors, likely behavioral, also affect the IFP.

Uniform expression of alcohol dehydrogenase 3 in epithelia regenerated with cultured normal, immortalised and malignant human oral keratinocytes.

The human oral epithelium is a target for damage from the inhalation of formaldehyde. However, most experimental studies on this chemical have relied on laboratory animals that are obligatory nose breathers, including rats and mice. Therefore, in vitro model systems that mimic the structure of the human oral epithelium and which retain normal tissue-specific metabolic competence are desirable. Based on the established role of alcohol dehydrogenase 3 (ADH3), also known as glutathione-dependent formaldehyde dehydrogenase, as the primary enzyme catalysing the detoxification of formaldehyde, the aim of this study was to investigate the expression of ADH3 in organotypic epithelia regenerated with normal (NOK), immortalised (SVpgC2a) and malignant (SqCC/Y1) human oral keratinocytes. Organotypic epithelia, usually consisting of 5-10 cell layers, were produced at the air-liquid interface of collagen gels containing human oral fibroblasts, after culture for 10 days in a standardised serum-free medium. Immunochemical staining demonstrated uniform expression of ADH3 in these organotypic epithelia, as well as in the epithelial cells of oral tissue. The specificity of the ADH3 antiserum was ascertained from the complete neutralisation of the immunochemical reaction with purified ADH3 protein. Assessment of the staining intensities indicated that the expression levels were similar among the regenerated epithelia. Furthermore, the regenerated epithelia showed similar ADH3 expression to the epithelium in oral tissue. Therefore, a tissue-like expression pattern for ADH3 can be generated from the culture of various oral keratinocyte lines in an organotypic state. Similar expression levels among the various cell lines indicate the preservation of ADH3 during malignant transformation, and therefore that NOK, SVpgC2a and SqCC/Y1 represent functional models for in vitro studies of formaldehyde metabolism in human oral mucosa.

L’obstruction nasale néonatale

Neonatal nasal obstruction. J. Leraillez Because neonates are obligate nose breathers, neonatal nasal obstruction may have serious consequences. Prompt diagnosis and appropriate treatment are essential to avoid severe hypoxia. The most common cause of neonatal nasal obstruction is rhinitis. However, it is essential to first rule out anatomical causes such as choanal atresia and stenosis, pyriform aperture stenosis, traumatic deformation or tumors, as these conditions may be life-threatening and require prompt surgical treatment.

Nasal Strips Do Not Affect Cardiorespiratory Measures During Recovery From Anaerobic Exercise

Nasal dilators supposedly aid recovery from exercise by reducing nasal airway resistance. Research has focused on the effectiveness of nasal dilators during exercise. The purpose of this study was to examine the effects of nasal dilators on heart rate (HR), minute ventilation (VE), and oxygen consumption (Vo2) during recovery from anaerobic exercise. Fourteen subjects (19-32 years) performed a modified Cunningham-Faulkner anaerobic treadmill test (1-minute walk at 2.0 miles per hour [mph], 0% grade; 1-minute jog at 5 mph, 0% grade; and sprint at 8 mph, 20% grade) under 3 randomly assigned conditions: (a) control, (b) nasal strip, and (c) placebo nasal strip. A 10-minute recovery period consisting of 5 minutes of walking (2 mph, 0% grade) and 5 minutes of passive recovery (seated) was completed. During the test and recovery periods, the participant wore a fireman's face mask to allow for simultaneous sampling of nose and mouth breathing. Vo2 and VE were monitored by a TEEM 100 metabolic analyzer. Each subject wore a Polar Heart Watch to monitor HR every minute during recovery. Mean time to exhaustion was 48.4 seconds (+/-14.9). One-way repeated-measures analyses of variance (ANOVAs) indicated no significant nasal dilator effect on 5-minute recovery HR or 10-minute recovery HR, 5-minute recovery Vo2 or 10-minute recovery Vo2, and 5-minute recovery VE or 10-minute recovery VE. Nasal strips appear to have no significant impact during recovery from anaerobic exercise.

The significance of late developmental crowding to early treatment planning for incisor crowding

Incisor crowding has traditionally been attributed to discrepancies in either tooth-jaw size or interarch tooth-size ratios. Such concepts have led orthodontists to develop mixed and permanent dentition space and interarch tooth-size analyses to assist in the diagnosis of crowded dentitions. Treatment plans have emphasized the removal of 4 premolars in an attempt to stabilize the dentition. Although individuals with large teeth may tend to have more incisor crowding, several factors other than tooth size may contribute to incisor crowding, for example, altered resting or functional activity in the facial and masticatory muscles. Thus, changes in occlusion, incisor crowding-spacing, lower anterior face height, and mandibular and maxillary retrognathism or prognathism have all been induced in primates through the application of a single chronically acting, environmental impact, such as either altered tongue posture or oral respiration.1-4 In addition, similar changes have been shown in human beings that were partially reversible after removal of the environmental impact.5,6 Thus, adverse neuromuscular changes, such as chronic mouth open breathing, have been associated with narrowing of both arches and lingual inclination of the incisor teeth and crowded dentitions.1,7-10 These dentoalveolar and skeletal changes were partially or fully reversible without orthodontic therapy after removal of the chronic input8,10 It follows that judicious orthodontic expansion procedures might be warranted to assist recovery in such cases after removal of the neuromuscular insult. We are indebted to the University of Washington for their documentation of late developmental crowding up to age 40 in orthodontically untreated as well as treated individuals. Study of untreated individuals at the University of Toronto shows that this phenomenon continues to at least age 70. Such crowding seen during the teen and adult years cannot be called tooth-jaw size discrepancy and must be neuromuscular in nature. Strong evidence supports the view that many of the crowdings we see during the mixed dentition are also neuromuscular or developmental. In a previous study9 of the relationship between mandibular incisor crowding and nasal mucosal swelling, cephalometric and dental cast variables from 30 male and 20 female children (8 to 13 years old) with chronic nasal mucosal swelling were compared with matched controls. These controls were orthodontically untreated and had no history of airway obstruction. The nasal mucosal swelling was confirmed with active posterior rhinomanometry and a headout volume-displacement plethysmograph. The subjects with nasal mucosal swelling had significantly (P < .001) more mandibular incisor crowding aDepartment of Orthodontics, University of Toronto. Reprint requests to: Donald G. Woodside, CM, DDS, MSc(D), PhD(hc), Department of Orthodontics, University of Orthodontics, 124 Edward Street, Toronto, Ontario, Canada M5G 1G6. Copyright © 2000 by the American Association of Orthodontists. 0889-5406/2000/$12.00 + 0 8/1/106117 doi.10.1067/mod.2000.106117 The significance of late developmental crowding to early treatment planning for incisor crowding

Radon: characteristics in air and dose conversion factors.

The dose conversion factor (DCF) which gives the relationship between effective dose and potential alpha energy concentration of inhaled short-lived radon decay products is calculated with a dosimetric approach. The calculations are based on a lung dose model with a structure that is related to the new recommended ICRP respiratory tract model. The characteristics of the radon decay products concerning the unattached fraction and the activity size distribution of the radon decay products are important input quantities for the calculation of DCF. Experimental data about these parameters obtained from measurements in homes, at working places, and in the free atmosphere at ground level in the last past years are summarized. Taking into account the measured aerosol characteristics the DCF fractions of the unattached (DCFu) and aerosol-attached (DCFae) radon decay products for different places were calculated. Variation of DCF for different places were caused dominantly by the variation of DCFu of the unattached radon clusters (0.3-32 mSv WLM(-1)). Nose inhalation drastically reduced (about a factor 4) the dose contribution by the unattached cluster. The dose fraction by the radon decay product aerosol (DCFae) varies between 4-10 mSv WLM(-1). Taking into account a relative sensitivity distribution between bronchial, bronchiolar and alveolar regions of the thoracic lung with 0.80:0.15:0.05 and nose breathing the DCF of most of the working places (inhalation rate: 1.2 m3 h(-1)) vary between 5.7-6.7 mSv WLM(-1) depending on the number concentration of the aerosol particles. The DCF-value of 4.2 mSv WLM(-1) for the general public in dwellings with higher aerosol concentration (>4 x 10(4) particles cm(-3)) has about the same value as recommended by ICRP 65 (1994b). Significantly higher are the DCF-values for "normal" aerosol conditions indoors (5 x 10(3)-4 x 10(4) particles cm(-3)) and in the open air (7.3 mSv WLM(-1) and 9.7 mSv WLM(-1)).

Nasal splinting effects on breathing patterns and cardiorespiratory responses

The aim of this study was to compare the effects of nasal splinting during different modes of breathing on breathing patterns and cardiorespiratory responses. Ten healthy subjects (4 males, 6 females) performed five maximal treadmill tests while breathing through the nose, nose + dilator, mouth, nose + mouth, and nose + mouth + dilator. Repeated-measures analysis of variance and Tukey HSD revealed no significant differences between trials for maximal oxygen consumption, minute ventilation at an oxygen consumption of 30 ml. kg-1.min-1, carbon dioxide production, respiratory exchange ratio, tidal volume, dead space to tidal volume ratio, or completed treadmill stages to exhaustion. No significant difference was found in subjective dyspnoea ratings between stages of nose versus nose + dilator breathing. Minute ventilation, ventilatory equivalent for oxygen, and breath frequency for nose and nose + dilator versus mouth, nose + mouth, and nose + mouth + dilator were significantly lower. Ventilatory equivalent for carbon dioxide was significantly lower for nose versus mouth, and nose + dilator versus nose + mouth + dilator breathing. End-tidal carbon dioxide was significantly higher in nose versus mouth, nose + mouth, and nose + mouth + dilator breathing, and in nose + dilator versus mouth breathing. Nose breathing revealed a significantly lower heart rate versus nose + dilator, mouth, nose + mouth, and nose + mouth+dilator breathing. These results suggest that nasal splinting during exercise has minimal effects when nasal breathing and no effects when oronasal breathing.

SHORT-TERM EXPOSURES OF RATS TO AIRBORNE HYDROGEN FLUORIDE

A series of acute inhalation exposures was performed with airborne hydrogen fluoride (HF) to establish the concentration response for nonlethal effects in the rat. Exposures were either 2 or 10 min long; concentrations ranged from 135 to 8621 ppm. Three additional exposures (20 to 48 ppm) were performed for 60 min. A mouth-breathing (MB) model with a tracheal cannula was used in most of the exposures to maximize delivery of the HF to the lower respiratory tract. Endpoints on the day after exposure included hematology, serum chemistry, bronchoalveolar lavage, pulmonary function, organ weights, and histopathology. Nasal resistance was measured in nose-breathing (NB) groups. Effects of exposure were generally limited to the respiratory tract and included alveolitis, bronchial lesions, altered parameters of pulmonary function and bronchoalveolar lavage, and mucosal necrosis, inflammation, and fibrinopurulent exudate in airways. Observed changes were concentration related and appeared more pronounced in major airways near the point of entry (trachea in MB animals and nose in NB animals). One group of MB animals exposed for 10 min to 1454 ppm was evaluated at 3 and 14 wk after exposure; the acute effects had resolved by those times. The effects of 2-min exposures were consistently more severe than those from 10-min exposures to the same product of concentration x time. Exposures of MB animals for 60 min to 20 or 48 ppm HF did not result in observable adverse effects, although quasistatic pressure-volume curves were shifted upward slightly after 48 ppm. These data provide an integrated picture of the concentration-related effects of short nonlethal exposures to HF.

Inhalability of large particles for mouth and nose breathing

Inhalability of large particles for mouth and nose breathing

Radiation dose to the human respiratory tract from inhalation of radon-222 and its progeny

In this article the regional dose equivalent for exposure to 1 working level month (WLM), the annual effective dose equivalent and the dose equivalent conversion factor due to the inhalation of short-lived radon progeny ( 218Po, 214Pb and 214 Bi 214 Po ) are calculated with a dosimetric model. Experimental results of aerosol size characteristics, unattached activity fractions, equilibrium factors, and activity size distribution of the short-lived radon progeny in indoor and outdoor atmosphere are summarized. Dose calculations based on these results show that the changes in dose rate values are influenced by the different model assumptions concerning deposition probabilities of aerosol particles in the respiratory system during inhalation, the sensitivity of different cells (epithelial, basal) to radiation and assuming nose or mouth breathing. The inverse relationship between the unattached fraction of potential alpha-particle energy in room air and the radioactive equilibrium between radon gas and its progeny indicates that dose equivalent is closely related to the concentration of radon gas averaged over a period of exposure.