Does Nasal Cavity Enlargement Associated With Respiratory Function Improvement After Surgically Assisted Rapid Maxillary Expansion?

PURPOSE: To systematically evaluate the effects of surgically assisted rapid maxillary expansion (SARME) on nasal cavity and its associated respiratory function changes. MATERIAL AND METHODS: Multiple electronic databases were searched, authors were contacted as required, and reference lists of potentially relevant studies were screened. Articles that included patients older than 16 who had received SARME were considered. Data extraction and quality assessment were performed independently and in duplicate. RESULTS: Eight articles, including 161 patients, were finally selected and analyzed. Nasal cavity significantly augmentation after SARME has been recognized by 7 studies with moderate-quality evidence. Among them, the nasal cavity volume increased <20% in 4 studies, 20% to 40% in 1 study, and >40% in 2 studies. Totally, the range of increasing in nasal cavity volume was 7.6% to 99%. One study had recorded the nasal expiratory and inspiratory flow significantly increased 18.5% and 21.7%, respectively. CONCLUSION: SARME was found to produce meaningful volume augmentation in nasal cavity with adult patients. However, the improvement of nasal respiratory function has not been well elucidated; thus, SARME is not yet recommended for the purpose of improving nasal respiratory.

Prevention of Nasal Ala Pressure Injuries With Use of Hydroactive Dressings in Patients With Nasotracheal Intubation of Orthognathic Surgery: A Randomized Controlled Trial.

PURPOSE: To compare a hydroactive dressing to an adhesive tape standard of care in the prevention of nasal ala pressure injuries associated with nasotracheal intubation during orthognathic surgery. DESIGN: Randomized controlled trial. SUBJECTS AND SETTING: The study took place in a tertiary hospital of stomatology in China. Patients undergoing general anesthesia with nasotracheal intubation during orthognathic surgical procedures were invited to participate. METHODS: Participants were divided into 2 groups: in the experimental group, a hydroactive dressing was applied to the nasal ala before the surgical procedures; the control group received standard prevention with a type of tape. Skin assessments were performed on the wards up to 72 hours after the procedures. Demographic information and potential contributing factors associated the development of nasal ala pressure injuries were collected from patients' electronic medical records. Pressure injury development was staged using National Pressure Injury Advisory staging guidelines. Pressure injury incidence was compared between groups using the χ test and odds ratio. RESULTS: The sample comprised 450 participants, 225 in each group. The incidence of nasal ala pressure injuries development was 14.222% and 4.444% in the 2 groups, respectively (P = .000). The odds ratio was 3.565 (95% confidence interval, 1.707-7.443). CONCLUSIONS: The study findings indicate that the incidence of pressure injuries of nasal ala skin protected by hydroactive dressings was lower than the standard preventive method. Hydroactive dressings should be considered as a prevention method to reduce device-related skin injuries associated with nasotracheal intubation.

Effects on nasal airflow and resistance using two different RME appliances: a randomized controlled trial.

Objectives: To evaluate and compare the effects of tooth-borne (TB) and tooth-bone-borne (TBB) rapid maxillary expansion (RME) on nasal airflow and resistance. Material and methods: Fifty-four consecutive patients who met the eligibility criteria were recruited from September 2010 to December 2015. Of these 54 subjects, 40 agreed to participate in the part of the study involving evaluation of nasal flow and resistance. The 40 subjects were allocated to either the TB group, mean age 9.7 years (SD 1.5), or the TBB group, mean age 10.2 years (SD 1.4). All subjects performed rhinomanometric registration at baseline (T0), but only 30 attended the post-expansion registration (T1), of whom 16 had been randomized to the TB group and 14 to the TBB group. The study outcomes, nasal airflow and nasal airway resistance, were evaluated with linear regression adjusted for baseline variable of the outcome to compare the study groups with complete cases strategy as well as after multiple imputation (MI). Randomization: Participants were randomly allocated in blocks of different sizes, using the concealed allocation principle in a 1:1 ratio. The randomization list was computer generated to ensure homogeneity between groups. Blinding: Blinding was done only for outcome assessor due to clinical limitations. The care providers at the ENT unit who conducted all the rhinomanometry examinations were blinded to which group the patients were allocated to. Results: Complete case analysis showed significantly higher post-expansion nasal airflow values for the TBB group compared with the TB group, mean difference 51.0 cm3/s (P = 0.018). The evaluation after MI showed a similar significant mean difference, 52.7 cm3/s (P = 0.020) in favour of the TBB group when taking into account the missing values from the T1 examination. Even reduction in nasal airway resistance showed similar pattern in favour of the TBB group. Limitations: Our results represent the short-term effects. A longer follow-up period would have been preferable. Conclusions: The TBB RME induced significantly higher nasal airway flow and lower nasal resistance values than TB RME. It might be wiser to use TBB RME in cases with constricted maxilla and upper airway obstruction. Registration: This trial was not registered in any external sites. Protocol: The protocol was not published before trial commencement.

Relationships among nasal resistance, adenoids, tonsils, and tongue posture and maxillofacial form in Class II and Class III children.

INTRODUCTION: The purpose of this study was to clarify the relationships between upper airway factors (nasal resistance, adenoids, tonsils, and tongue posture) and maxillofacial forms in Class II and III children. METHODS: Sixty-four subjects (mean age, 9.3 years) with malocclusion were divided into Class II and Class III groups by ANB angles. Nasal resistance was calculated using computational fluid dynamics from cone-beam computed tomography data. Adenoids, tonsils, and tongue posture were evaluated in the cone-beam computed tomography images. The groups were compared using Mann-Whitney U tests and Student t tests. The Spearman rank correlations test assessed the relationships between the upper airway factors and maxillofacial form. RESULTS: Nasal resistance of the Class II group was significantly larger than that of the Class III group (P = 0.005). Nasal resistance of the Class II group was significantly correlated with inferior tongue posture (P <0.001) and negatively correlated with intermolar width (P = 0.028). Tonsil size of the Class III group was significantly correlated with anterior tongue posture (P <0.001) and mandibular incisor anterior position (P = 0.007). Anterior tongue posture of the Class III group was significantly correlated with mandibular protrusion. CONCLUSIONS: The relationships of upper airway factors differ between Class II and Class III children.

Congenital arhinia - First published case in Malaysia.

Congenital arhinia is one of the rare craniofacial malformation that may cause severe respiratory distress at birth due to upper airway obstruction. Our patient, whose abnormalities were only detected after delivery in our centre, is the first reported case of congenital arhinia in Malaysia. Contrary to popular belief that neonates are obligate nasal breather, our patient adapted well to breathing through mouth before an elective tracheostomy was performed on day four of life.

Complications following nasotracheal intubation using cuffed polyvinyl chloride tube: a prospective cross sectional study.

Background: To examine the complications following nasotracheal intubation by documenting the nasal traumas observed with the use of untreated cuffed polyvinyl chloride tube in unprepared nostrils. Methods: Patients who had maxillofacial surgeries under general anesthesia, muscle relaxation and nasotracheal intubation were included in the study. Nasotracheal intubation was carried out after induction of anesthesia was effected with intravenous propofol and suxamethonium by an Anesthetist using well lubricated cuffed polyvinyl chloride tube. Sizes 6.0, 6.5 and 7.0mm were inserted in females while sizes 7.0 and 7.5mm were inserted in males. Occasionally, the natural curve of the tube guides it through the cords without the aid of Magill forceps. Anterior rhinoscopy was performed by otolaryngologist 24 hours after surgery. Results were subjected to statistical analysis. Results: Sixty four patients were included in the study. They were between the ages of 21 and 63 years (mean 33.2 ± 14.1 years); they were 39 males and 25 females. The most frequently used nasotracheal tube (NT) was size 7.0mm internal diameter. Epistaxis was noticed in 52 (81.2%) patients. There were no statistically significant differences in the incidence of epistaxis observed in males and females, and also between right and left nostrils. A total of 46.8% of nasal trauma were inferior turbinate trauma involving the inferior medial aspect. Conclusion: The use of untreated cuffed polyvinyl chloride tube for nasotracheal intubation in unprepared nostrils is associated with a high incidence of epistaxis and nasal trauma.

Validation of polyvinylidene fluoride nasal sensor to assess nasal obstruction in comparison with subjective technique.

OBJECTIVE: The aim of this study is to validate the applicability of the PolyVinyliDene Fluoride (PVDF) nasal sensor to assess the nasal airflow, in healthy subjects and patients with nasal obstruction and to correlate the results with the score of Visual Analogue Scale (VAS). METHODS: PVDF nasal sensor and VAS measurements were carried out in 50 subjects (25-healthy subjects and 25 patients). The VAS score of nasal obstruction and peak-to-peak amplitude (Vp-p) of nasal cycle measured by PVDF nasal sensors were analyzed for right nostril (RN) and left nostril (LN) in both the groups. Spearman's rho correlation was calculated. The relationship between PVDF nasal sensor measurements and severity of nasal obstruction (VAS score) were assessed by ANOVA. RESULTS: In healthy group, the measurement of nasal airflow by PVDF nasal sensor for RN and LN were found to be 51.14±5.87% and 48.85±5.87%, respectively. In patient group, PVDF nasal sensor indicated lesser nasal airflow in the blocked nostrils (RN: 23.33±10.54% and LN: 32.24±11.54%). Moderate correlation was observed in healthy group (r=-0.710, p<0.001 for RN and r=-0.651, p<0.001 for LN), and moderate to strong correlation in patient group (r=-0.751, p<0.01 for RN and r=-0.885, p<0.0001 for LN). CONCLUSION: PVDF nasal sensor method is a newly developed technique for measuring the nasal airflow. Moderate to strong correlation was observed between PVDF nasal sensor data and VAS scores for nasal obstruction. In our present study, PVDF nasal sensor technique successfully differentiated between healthy subjects and patients with nasal obstruction. Additionally, it can also assess severity of nasal obstruction in comparison with VAS. Thus, we propose that the PVDF nasal sensor technique could be used as a new diagnostic method to evaluate nasal obstruction in routine clinical practice.

[Aerosol deposition in nasal passages of burrowing and ground rodents when breathing dust-laden air].

In subterranean rodents, which dig down the passages with frontal teeth, adaptation to the underground mode of life presumes forming of mechanisms that provide protection against inhaling dust particles of different size when digging. One of such mechanisms can be specific pattern of air flow organization in the nasal cavity. To test this assumption, comparative study of geometry and aerodynamics of nasal passages has been conducted with regard to typical representative of subterranean rodents, the mole vole, and a representative of ground rodents, the house mouse. Numerical modeling of air flows and deposition of micro- and nanoparticle aerosols indicates that sedimentation of model particles over the whole surface of nasal cavity is higher in mole vole than in house mouse. On the contrary, particles deposition on the surface of olfactory epithelium turns out to be substantially less in the burrowing rodent as compared to the ground one. Adaptive significance of the latter observation has been substantiated by experimental study on the uptake ofnanoparticles of hydrated manganese oxide MnO x (H2O)x and Mn ions from nasal cavity into brain. It has been shown with use of magnetic resonance tomography method that there is no difference between studied species with respect to intake of particles or ions by olfactory bulb when they are introduced intranasally. Meanwhile, when inhaling nanoparticle aerosol of MnCl2, deposition of Mn in mouse's olfactory bulbs surpasses markedly that in vole's bulbs. Thereby, the morphology of nasal passages as a factor determining the aerodynamics of upper respiratory tract ensures for burrowing rodents more efficient protection of both lungs and brain against inhaled aerosols than for ground ones.

Improvement of nasal airway ventilation after rapid maxillary expansion evaluated with computational fluid dynamics.

INTRODUCTION: Rapid maxillary expansion is known to improve nasal airway ventilation. However, it is difficult to precisely evaluate this improvement with conventional methods. The purpose of this longitudinal study was to use computational fluid dynamics to estimate the effect of rapid maxillary expansion. METHODS: Twenty-three subjects (9 boys, 14 girls; mean ages, 9.74 ± 1.29 years before rapid maxillary expansion and 10.87 ± 1.18 years after rapid maxillary expansion) who required rapid maxillary expansion as part of their orthodontic treatment had cone-beam computed tomography images taken before and after rapid maxillary expansion. The computed tomography data were used to reconstruct the 3-dimensional shape of the nasal cavity. Two measures of nasal airflow function (pressure and velocity) were simulated by using computational fluid dynamics. RESULTS: The pressure after rapid maxillary expansion (80.55 Pa) was significantly lower than before rapid maxillary expansion (147.70 Pa), and the velocity after rapid maxillary expansion (9.63 m/sec) was slower than before rapid maxillary expansion (13.46 m/sec). CONCLUSIONS: Improvement of nasal airway ventilation by rapid maxillary expansion was detected by computational fluid dynamics.

[The substantiation of the approach for endoscopic surgery of nasal liquorrhea].

The objective of the present study was to develop a rationale for the approach to be employed in endoscopic surgery of nasal liquorrhea. A total of 69 patients presenting with this condition were available for the observation. Traumatic liquorrhea accounted for 80% of the cases, iatrogenic liquorrhea for 10%, liquorrhea associated with malformations for 5%, and spontaneous liquorrhea for 5% of the cases. The diagnostic algorithms elaborated for the identification of liquor cartilages were used to develop the criteria for the choice of the operative approach. A total of 69 surgical interventions were performed including 54 transnasal, 20 transethmoidal, 29 transsphenoidal, 5 endonasal, and 15 transcranial operations. The liquor fistulas were closed using tissue fragments and artificial materials, viz. muscles, broad fascia of thigh, periosteum and cartilage of the nasal septum, the mucous membrane from the nasal cavity, TachoComb plates, hemostatic sponge, fibrin-thrombin glue, bone crumbs, elements of bone marrow, and stem cells. The study has demonstrated the advantages of transnasal surgical treatment of liquor fistulas. The principles of postoperative care for the patients have been developed.

Nasometric and aerodynamic outcome analysis of pharyngeal flap surgery for the management of velopharyngeal insufficiency.

OBJECTIVE: This study aimed to evaluate the effectiveness of pharyngeal flap surgery (PFS) for the management of velopharyngeal insufficiency in cleft lip/palate patients and to assess the impact of age at surgery, surgeon's skills, and postoperative speech therapy on the outcomes. METHODS: Prospective preoperative and postoperative assessments were performed on 240 patients aged 6 to 57 years using nasometry and pressure-flow studies.This study was carried out in a quaternary hospital.This study was superiorly based on PFS.Speech nasalance scores were assessed by nasometry and velopharyngeal orifice area assessed by pressure-flow technique, 2 days before and 1 year after PFS, on average. Differences were considered significant when P < 0.05. RESULTS: Significant reduction in nasalance scores was observed in 68% of the cases, and improvement of velopharyngeal area was observed in 66%. Rates of 55% and 48%, respectively, were observed when complete resolution was considered. Higher success rates were observed in children (81%) compared with other age groups analyzed and in patients who had concluded postoperative speech therapy (86%). Results did not differ among surgeons. CONCLUSIONS: Pharyngeal flap surgery was shown to be effective in reducing nasalance scores and velopharyngeal area during speech for a significant number of patients. Complete resolution was observed in smaller number of cases. Age at surgery and postoperative speech therapy were relevant factors for treatment success.

Evaluation of upper airway obstruction in Class II children with fluid-mechanical simulation.

INTRODUCTION: The purpose of this study was to test the null hypothesis that dolichofacial and brachyfacial children with Class II malocclusion do not differ in upper airway obstruction. Furthermore, the ability of fluid-mechanical simulation to detect airway obstruction within the limitations of simulation was examined. METHODS: Forty subjects from 7 to 11 years of age with Class II malocclusion participated and were divided into 2 groups, dolichofacial and brachyfacial, based on their Frankfort mandibular plane angles. Cone-beam computed tomography images supplied the shape of the entire airway. Two measures of respiratory function, air velocity and pressure, were simulated by using 3-dimensional images of the airway. The images and simulations were compared between the 2 facial types. RESULTS: The size of the upper airway did not differ statistically between facial types; however, the simulated maximal pressure and velocity of the dolichofacial type were significantly higher than those of the brachyfacial type. CONCLUSIONS: Airway obstruction differs with the Frankfort mandibular plane angle, even though the depth and cross-sectional area of the airway do not. The fluid-mechanical simulation system developed in this study detected differences in airway obstruction that were not apparent from morphologic studies.

Nasal cavity size, airway resistance, and subjective sensation after surgically assisted rapid maxillary expansion: a prospective longitudinal study.

INTRODUCTION: The aims of this study were to measure changes in nasal minimum cross-sectional area and nasal airway resistance after surgically assisted rapid maxillary expansion and to explore a possible correlation with the subjective sensation of nasal obstruction. METHODS: Minimum cross-sectional area and nasal airway resistance were measured in 39 consecutive patients treated with surgically assisted rapid maxillary expansion. Subjective nasal obstruction was assessed by a questionnaire at pretreatment and at 3 and 18 months postoperatively. RESULTS: Subjective nasal obstruction had improved significantly by 3 months postoperatively. Minimum cross-sectional area increased and nasal airway resistance decreased. No correlations were found. In subjects with pretreatment subjective nasal obstruction and initially narrow anterior minimum cross-sectional area, there was a significant correlation between a moderate increase in anterior minimum cross-sectional area and improvement in perceived nasal obstruction. Eighteen months postoperatively, no changes were found from pretreatment values for subjective nasal obstruction, minimal cross-sectional area, or nasal airway resistance, and there were no correlations. Subjects with a sensation of nasal obstruction at treatment start reported a lasting significant subjective improvement. CONCLUSIONS: The postoperative effects of surgically assisted rapid maxillary expansion did not persist in the long term. No correlation was found between objective and subjective findings. Subjects with pretreatment nasal obstruction, however, reported a lasting sensation of improved nasal function after surgically assisted rapid maxillary expansion.

Measuring vital capacity in amyotrophic lateral sclerosis: Effects of interfaces and reproducibility.

BACKGROUND: Deterioration of vital capacity (VC) in amyotrophic lateral sclerosis (ALS) signifies disease progression and indicates need for non-invasive ventilation. Weak facial muscles consequent to ALS, with resulting poor mouth seal, may interfere with the accuracy of VC measurements. OBJECTIVES: To determine whether different interfaces affect VC measurements in ALS patients and whether the interface yielding the largest VC produces an even higher VC when re-measured after one week (learning effect). To explore the relationship between optimal interface VC and sniff nasal pressure (SNIP), a measurement of global inspiratory muscle strength. METHODS: Thirty-five patients (17 bulbar and 18 spinal ALS) were studied. Three interfaces (rigid-cylindrical, flanged, oronasal mask) were tested. One week after the first visit, VC was recorded using the optimal interface. SNIP recordings were also obtained. RESULTS: In the bulbar ALS group, median (interquartile range) VC with the flanged mouthpiece was 8.4% (3.9-15.5) larger than with the cylindrical mouthpiece (p < 0.001). VC values with oronasal mask were intermediate to VC with the other two interfaces. In spinal ALS, flanged mouthpiece VC was 4.6% (2.3-7.5) larger than with oronasal mask (p < 0.0006). The latter was 4.5% (0.6-5.2) smaller than with the cylindrical mouthpiece (p = 0.002). In both groups, VC during the second visit was greater than during the first visit (p < 0.025). SNIPs were logarithmically related to VC values recorded with the flanged mouthpiece. CONCLUSION: A flanged mouthpiece yields the largest values of VC in patients with bulbar and spinal ALS.

Computational fluid dynamic study on obstructive sleep apnea syndrome treated with maxillomandibular advancement.

Maxillomandibular advancement is one of the treatments available for obstructive sleep apnea. The influence of this surgery on the upper airway and its mechanism are not fully understood. The present research simulates the flow fields of narrowed upper airways of 2 patients with obstructive sleep apnea treated with maxillomandibular advancement. The geometry of the upper airway was reconstructed from computed tomographic images taken before and after surgery. The consequent three-dimensional surface model was rendered for measurement and computational fluid dynamics simulation. Patients showed clinical improvement 6 months after surgery. The cross-sectional area of the narrowest part of the upper airway was increased in all dimensions. The simulated results showed a less constricted upper airway, with less velocity change and a decreased pressure gradient across the whole conduit during passage of air. Less breathing effort is therefore expected to achieve equivalent ventilation with the postoperative airway. This study demonstrates the possibility of computational fluid dynamics in providing information for understanding the pathogenesis of OSA and the effects of its treatment.

Maxillary protraction with and without maxillary expansion: a finite element analysis of sutural stresses.

INTRODUCTION: In this finite element study, we compared the stress patterns along the various craniofacial sutures with maxillary protraction with and without expansion. METHODS: Two 3-dimensional analytic models were developed, 1 simulating maxillary protraction and the other simulating maxillary protraction with expansion. The model consisted of 108799 10 node solid 92 elements (tetrahedron), 193633 nodes, and 580899 degrees of freedom. RESULTS: The overall stresses after maxillary protraction with maxillary expansion were significantly higher than with a facemask alone. The magnitude of stress on the craniofacial sutures with maxillary protraction alone was in the range of a few millinewtons per square millimeter, whereas, with maxillary protraction with maxillary expansion, the stresses ranged from a few newtons per square millimeter to a few hundred newtons per square millimeter. The pattern of stress distribution also differed with the 2 treatment modalities as did the sutures experiencing maximum and minimum stresses. CONCLUSIONS: The osteogenic potential of such low stresses after maxillary protraction can be questioned. High stresses generated in various craniofacial sutures after maxillary protraction with expansion are responsible for disrupting the circummaxillary sutural system and presumably facilitating the orthopedic effect of the facemask.

Comparison between rhinometric variables and nasal airing in children with mouth breathing

ABSTRACT Purpose: to analyze the correlation between the values of nasal aeration and geometry of the nasal cavities, before and after nasal cleansing in children with mouth breathing. Methods: 20 children aged 4 to 12 years old were chosen. The questionnaire Identification Index of Signs and Symptoms of Oral breathing was applied and nasal patency was assessed by nasal aeration, through the Altmann graded mirror, and the nasal geometry measured by acoustic rhinometry. After nasal cleansing and massage, the same aeration measurements and nasal geometry procedures were performed. Group normality was analyzed using the Shapiro-Wilk test considering the hypothesis of normal distribution whenever p>0.05. The Spearman's test was applied to analyze the correlation between variables (p<0.05). Results: there was a strong and significant correlation between nasal aeration and the corresponding cross-sectional area of the front of the inferior turbinate (CSA2) in the left cavity before cleansing. There were no correlations between the nasal aeration and other rhinometric variables. Conclusion: there was a correlation between nasal aeration values and the anterior portion of the turbinates, before the massage and nasal cleansing technique, in mouth breathing children. There were no significant differences when the nasal aeration was correlated with other rhinometric variables.

Change in the nose areas in children with mouth breathing after nasal cleansing and massage. / Mudança nas áreas nasais em crianças com respiração oral após a limpeza e massagem nasal.

PURPOSE: To analyze the changes occurred in the nasal cavity geometry, before and after nasal cleansing, through nasal aeration and acoustic rhinometry in children with oral breathing. METHODS: Twenty children aged four to 12 years were included in the study. The gathering of participants was conducted at the Multifunctional Laboratory of the Speech Pathology Department of the Federal University of Pernambuco - UFPE. The following procedures were conducted: Identification Index of Signs and Symptoms of Oral Breathing; marking of nasal expiratory airflow using the graded mirror of Altmann, and examination of the Nasal Geometry by Acoustic Rhinometry. The same procedures were performed after nasal massage and cleansing with saline solution. RESULTS: Significant change was observed in the areas with respect to the nasal airflow on both sides after nasal cleansing and massage. As for nasal geometry, measured by acoustic rhinometry, comparison between the nostrils showed that the effect of cleansing and massage was discrete. CONCLUSION: Nasal aeration measures showed sensitivity to the cleansing and massage technique and measures of nasal geometry confirmed its effect on respiratory physiology.

Factors influencing delivered mean airway pressure during nasal CPAP with the RAM cannula.

OBJECTIVE: To measure mean airway pressure (MAP) delivered through the RAM Cannula® when used with a ventilator in CPAP mode as a function of percent nares occlusion in a simulated nasal interface/test lung model and to compare the results to MAPs using a nasal continuous positive airway pressure (NCPAP) interface with nares fully occluded. STUDY DESIGN: An artificial airway model was connected to a spontaneous breathing lung model in which MAP was measured at set NCPAP levels between 4 and 8 cmH2 O provided by a Dräger Evita XL® ventilator and delivered through three sizes of RAM cannulae. Measurements were performed with varying leakage at the nasal interface by decreasing occlusion from 100% to 29%, half-way prong insertion, and simulated mouth leakage. Comparison measurements were made using the Dräger BabyFlow® NCPAP interface with a full nasal seal. RESULTS: With simulated mouth closed, the Dräger interface delivered MAPs within 0.5 cmH2 O of set CPAP levels. For the RAM cannula, with 60-80% nares occlusion, overall delivered MAPs were 60 ± 17% less than set CPAP levels (P < 0.001). Further, MAP decreased progressively with decreasing percent nares occlusion. The simulated open mouth condition resulted in significantly lower MAPs to <1.7 cmH2 O. The one-half prong insertion depth condition, with closed mouth, yielded MAPs approximately 35 ± 9% less than full insertion pressures (P < 0.001). CONCLUSIONS: In our bench tests, the RAM interface connected to a ventilator in NCPAP mode failed to deliver set CPAP levels when applied using the manufacturer recommended 60-80% nares occlusion, even with closed mouth and full nasal prong insertion conditions.

Estimation of the Human Extrathoracic Deposition Fraction of Inhaled Particles Using a Polyurethane Foam Collection Substrate in an IOM Sampler.

Extrathoracic deposition of inhaled particles (i.e., in the head and throat) is an important exposure route for many hazardous materials. Current best practices for exposure assessment of aerosols in the workplace involve particle size selective sampling methods based on particle penetration into the human respiratory tract (i.e., inhalable or respirable sampling). However, the International Organization for Standardization (ISO) has recently adopted particle deposition sampling conventions (ISO 13138), including conventions for extrathoracic (ET) deposition into the anterior nasal passage (ET1) and the posterior nasal and oral passages (ET2). For this study, polyurethane foam was used as a collection substrate inside an inhalable aerosol sampler to provide an estimate of extrathoracic particle deposition. Aerosols of fused aluminum oxide (five sizes, 4.9 µm-44.3 µm) were used as a test dust in a low speed (0.2 m/s) wind tunnel. Samplers were placed on a rotating mannequin inside the wind tunnel to simulate orientation-averaged personal sampling. Collection efficiency data for the foam insert matched well to the extrathoracic deposition convention for the particle sizes tested. The concept of using a foam insert to match a particle deposition sampling convention was explored in this study and shows promise for future use as a sampling device.