Awake endoscopic assessment of the upper airway during tidal breathing: Definition of anatomical features and comparison with drug-induced sleep endoscopy.

OBJECTIVES: Awake nasopharyngoscopy is routinely performed in the assessment of patients who require treatment for sleep-disordered breathing (SDB). However, the applicability and accuracy of Müller's manoeuvre, the main evaluation method for this purpose, are disputable. The current study aimed to introduce an alternative method for awake nasopharyngoscopy in patients with SDB. DESIGN: We defined qualitative anatomical features during tidal breathing at the levels of the soft palate, oropharynx, tongue base, epiglottis and hypopharynx, and compared these awake features to the sites and patterns of collapse as observed during drug-induced sleep endoscopy (DISE). SETTING: Tertiary care academic centre. PARTICIPANTS: Seventy-three patients diagnosed with SDB. MAIN OUTCOME MEASURES: The primary outcome measure was the Kendall's tau correlation coefficient (τ) between observations during awake nasopharyngoscopy and DISE. Kappa-statistics (κ) were calculated to assess the agreement on awake endoscopic features with a second observer. RESULTS: In contrast to epiglottis shape, the modified Cormack-Lehane scale was significantly associated with epiglottis collapse during DISE (P < .0001; τ = .45). Other upper airway features that were correlated with DISE collapse were the position of the soft palate (P = .007; τ = .29), crowding of the oropharynx (P = .026; τ = .32) and a posteriorly located tongue base (P = .046; τ = .32). Interobserver agreement of endoscopic features during tidal breathing was moderate (0.60 ≤ κ < 0.80). CONCLUSION: The current study introduces a comprehensive and reliable assessment method for awake nasopharyngoscopy based on anatomical features that are compatible with DISE collapse patterns.

Neonatal Aerodigestive Disorders: Epidemiology and Economic Burden.

Aerodigestive disorders, those affecting the upper and lower airway or upper gastrointestinal tract, are interrelated anatomically during fetal development and functionally after birth. Successful respiration and feeding requires careful coordination to promote effective swallowing and prevent aspiration. I describe the epidemiology, including the prevalence of the most common aerodigestive disorders. The ability of an infant to feed by mouth at discharge, without a surgically placed feeding tube, is an important neurodevelopmental marker. Therefore, aerodigestive disorders have a high potential for lifelong morbidities and health care expenditures. When available, published research on related medical costs for these disorders is provided.

Sex differences in respiratory and circulatory cost during hypoxic walking: potential impact on oxygen saturation.

Energy expenditure (EE) during treadmill walking under normal conditions (normobaric normoxia, 21% O2) and moderate hypoxia (13% O2) was measured. Ten healthy young men and ten healthy young women walked on a level (0°) gradient a range of speeds (0.67-1.67 m s-1). During walking, there were no significant differences in reductions in arterial oxygen saturation (SpO2) between the sexes. The hypoxia-induced increase in EE, heart rate (HR [bpm]) and ventilation ([Formula: see text] [L min-1]) were calculated. Using a multivariate model that combined EE, [Formula: see text], and HR to predict ΔSpO2 (hypoxia-induced reduction), a very strong fit model both for men (r2 = 0.900, P < 0.001) and for women was obtained (r2 = 0.957, P < 0.001). The contributions of EE, VE, and HR to ΔSpO2 were markedly different between men and women. [Formula: see text] and EE had a stronger effect on ΔSpO2 in women ([Formula: see text]: 4.1% in women vs. 1.7% in men; EE: 28.1% in women vs. 15.8% in men), while HR had a greater effect in men (82.5% in men and 67.9% in women). These findings suggested that high-altitude adaptation in response to hypoxemia has different underlying mechanisms between men and women. These results can help to explain how to adapt high-altitude for men and women, respectively.

Second-hand smoke exposure in adulthood and lower respiratory health during 20 year follow up in the European Community Respiratory Health Survey.

BACKGROUND: Early life exposure to tobacco smoke has been extensively studied but the role of second-hand smoke (SHS) for new-onset respiratory symptoms and lung function decline in adulthood has not been widely investigated in longitudinal studies. Our aim is to investigate the associations of exposure to SHS in adults with respiratory symptoms, respiratory conditions and lung function over 20 years. METHODS: We used information from 3011 adults from 26 centres in 12 countries who participated in the European Community Respiratory Health Surveys I-III and were never or former smokers at all three surveys. Associations of SHS exposure with respiratory health (asthma symptom score, asthma, chronic bronchitis, COPD) were analysed using generalised linear mixed-effects models adjusted for confounding factors (including sex, age, smoking status, socioeconomic status and allergic sensitisation). Linear mixed-effects models with additional adjustment for height were used to assess the relationships between SHS exposure and lung function levels and decline. RESULTS: Reported exposure to SHS decreased in all 26 study centres over time. The prevalence of SHS exposure was 38.7% at baseline (1990-1994) and 7.1% after the 20-year follow-up (2008-2011). On average 2.4% of the study participants were not exposed at the first, but were exposed at the third examination. An increase in SHS exposure over time was associated with doctor-diagnosed asthma (odds ratio (OR): 2.7; 95% confidence interval (95%-CI): 1.2-5.9), chronic bronchitis (OR: 4.8; 95%-CI: 1.6-15.0), asthma symptom score (count ratio (CR): 1.9; 95%-CI: 1.2-2.9) and dyspnoea (OR: 2.7; 95%-CI: 1.1-6.7) compared to never exposed to SHS. Associations between increase in SHS exposure and incidence of COPD (OR: 2.0; 95%-CI: 0.6-6.0) or lung function (ß: - 49 ml; 95%-CI: -132, 35 for FEV1 and ß: - 62 ml; 95%-CI: -165, 40 for FVC) were not apparent. CONCLUSION: Exposure to second-hand smoke may lead to respiratory symptoms, but this is not accompanied by lung function changes.

Axial Spondyloarthritis after bariatric surgery: a 7-year retrospective analysis

Abstract Background: In recent decades, obesity has become a public health problem in many countries. The objective of this study was to evaluate the main joint and extra-articular manifestations related to spondyloarthritis (SpA) after bariatric surgery (BS) in a retrospective cohort. Methods: Demographic, clinical, laboratory and imaging data from nine patients whose SpA symptoms started after a BS have been described. Modified New York (mNY) criteria for ankylosing spondylitis (AS) and the Assessment of Spondyloarthritis International Society (ASAS) criteria for axial (ax-SpA) and peripheral (p-SpA) spondyloarthritis were applied. Results: The mean weight reduction after BS was 49.3 ±21.9 kg. The BS techniques were Roux-en-Y gastric bypass (n =8; 88.9%) and biliopancreatic diversion with duodenal switch (n = 1; 11.1%). Four (44.4%) patients had no axial or peripheral pain complaints before BS, while the other four (44.4%) had sporadic non-inflammatory back pain that had been attributed to obesity. One patient (11.1%) had persistent chronic back pain. In all nine cases, patients reported back pain onset or pattern (intensity or night pain) change after BS (mean time 14.7 ± 18 months). In addition, 8 of them (88.9%) were human leukocyte antigen (HLA)-B27 positive. All nine patients could be classified according to ASAS criteria as ax-SpA and five (55.6%) patients were classified as AS, according to the mNY criteria. Conclusion: Our data highlight a temporal link between SpA onset symptoms and the BS, suggesting a possible causal plausibility between the two events.

Sleep and airway assessment: A review for dentists.

INTRODUCTION: Dentists can be the first professionals to recognize a patient's potential sleep problem since they typically have more frequent contact with their patients than do physicians. It is important that dentists have a reasonable understanding of sleep disorders and how to assess their patients if they suspect such a problem so that a timely referral can be made or treatment can be provided as appropriate. OBJECTIVE: To review the key literature relevant to sleep-disordered breathing (SDB) characteristics and diagnosis, including history, examination, and investigation with an emphasis on radiographic airway analyses. CONCLUSION: The authors present a concise explanation of SDB conditions and an outline for thorough patient examination and evaluation, including radiographic airway analyses. Limited two-dimensional and three-dimensional norms exist for adult patients with no SDB and even less so for children. Much more research is needed, particularly in the pediatric population.

Correlation between PaO2/FiO2 and airway and vascular parameters in the assessment of cellular ex vivo lung perfusion system.

BACKGROUND: Ex vivo lung perfusion (EVLP) may be an essential process for the pre-transplant evaluation of the donor lungs. Currently, the partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2, or PF) ratio is the standard in the assessment of lung function in cellular EVLP, whereas other parameters, including airway and vascular parameters, have only been partially utilized. The primary purpose of this study is to assess the potential utility of other parameters as a surrogate of lung function in EVLP. METHODS: Yorkshire swine lungs (n = 12) and rejected human donor lungs (n = 12) were perfused in cellular-based EVLP for 2 hours. PF ratio, airway parameters (peak airway pressure, plateau pressure, dynamic compliance and static compliance) and vascular parameters (pulmonary vascular resistance and pulmonary artery pressure) were measured. The correlations between PF ratio and one of these parameters were analyzed. RESULTS: Correlations were identified in the following combinations: PF ratio and airway parameters (p < 0.05, each); PF ratio and vascular parameters (p < 0.05, each); static compliance and pulmonary vascular resistance in swine lungs (p = 0.0001); and PF ratio and airway parameters in rejected human lungs (p < 0.05, each). There were significant differences in all parameters between suitable cases and non-suitable cases in swine lungs (p < 0.02, each). CONCLUSIONS: Our results show that airway parameters are complementary quantitative indicators of lung function in cellular EVLP, based on the correlations with PF ratio in both swine lungs and human lungs.

Preoperative airway assessment - experience gained from a multicentre cluster randomised trial and the Danish Anaesthesia Database.

Difficulties with airway management in relation to general anaesthesia have been a challenge for the anaesthesiologist since the birth of anaesthesia. Massive landmark improvements have been made and general anaesthesia is now regarded as a safe procedure. However, rare, difficult airway management still occurs and it prompts increased risk of morbidity and mortality - especially when not anticipated. Several preoperative risk factors for airway difficulties have been identified, yet none have convincing diagnostic accuracy as stand alone tests. Combining several risk factors increase the predictive value of the test and multivariable risk models have been developed. The Simplified Airway Risk Index (SARI) is a predictive model developed for anticipation of a difficult direct laryngoscopy. However, neither the diagnostic accuracy of the SARI nor of any other model has been tested prospectively and compared with existing practice for airway assessment in a randomised trial setting. The first objective of this thesis was to quantify the proportion of unanticipated difficult intubation and difficult mask ventilation in Denmark. The second objective was to design a cluster randomised trial, using state of the art methodology, in order to test the clinical impact of using the SARI for preoperative airway assessment compared with a clinical judgement based on usual practice for airway assessment. Finally, to test if implementation of the SARI would reduce the proportion of unanticipated difficult intubation compared with usual care for airway assessment. This thesis is based on data from the Danish Anaesthesia Database (DAD). Paper 1 presents an observational cohort study on 188,064 patients who underwent tracheal intubation from 2008 to 2011. Data on the anaesthesiologists' preoperative anticipations of airway difficulties was compared with actual airway management conditions, thus enabling an estimation of the proportion of unanticipated difficulties with intubation and mask ventilation. Papers 2 and 3 outline the methodology and the pre-trial calculations and considerations leading to the DIFFICAIR trial described in Paper 4. The trial was designed to randomise anaesthesia department to either thorough education in, and subsequent use of the SARI for preoperative airway assessment or to continue usual care. Registration of the SARI in DAD was made mandatory in SARI departments and impossible in usual care departments. Conditions regarding anticipation of difficulties and actual airway managements were recorded as for Paper 1. DAD data made it possible to estimate an appropriate sample size, considering the between cluster variation, and to construct a stratification variable based on 2011 baseline values of the primary outcome used in the DIFFICAIR trial. Paper 1 revealed that 1.86% of all patients who were intubated, but not planned for advanced intubation techniques (e.g. video laryngoscopy), were unanticipated difficult to intubate. However, 75 to 93% of all difficult intubations were unanticipated. Furthermore, 94% of all difficult mask ventilations were unanticipated. In Paper 4, 59,514 patients were included in the primary analyses. The proportion of unanticipated difficult intubations was 2.38% (696/29,209) in SARI departments and 2.39% (723/30,305) in usual care departments. The adjusted odds ratio was 1.03 (95% CI: 0.77-1.38), p = 0.84. No significant differences were detected in other adjusted outcome measures and neither a 58% increase in patients anticipated to have intubation difficulties nor an 84% increase in patients scheduled for advanced intubation techniques in SARI departments reached statistical significance, p = 0.29 and p = 0.06 respectively. The papers constituting this thesis demonstrate that at high proportion of airway management difficulties are unanticipated. In a cluster randomised trial it was not possible to reduce the proportion of unanticipated difficult intubation in daily clinical practice by implementing a systematic approach for airway assessment compared with usual care. However, implementation of the SARI may increase the anticipation of intubation difficulties and it may change practice towards advanced intubation techniques. This thesis underlines the continued challenge anaesthesiologists face in predicting airway management related difficulties.

(Un)Healthy in the City: Respiratory, Cardiometabolic and Mental Health Associated with Urbanity.

BACKGROUND: Research has shown that health differences exist between urban and rural areas. Most studies conducted, however, have focused on single health outcomes and have not assessed to what extent the association of urbanity with health is explained by population composition or socioeconomic status of the area. Our aim is to investigate associations of urbanity with four different health outcomes (i.e. lung function, metabolic syndrome, depression and anxiety) and to assess whether these associations are independent of residents' characteristics and area socioeconomic status. METHODS: Our study population consisted of 74,733 individuals (42% males, mean age 43.8) who were part of the baseline sample of the LifeLines Cohort Study. Health outcomes were objectively measured with spirometry, a physical examination, laboratory blood analyses, and a psychiatric interview. Using multilevel linear and logistic regression models, associations of urbanity with lung function, and prevalence of metabolic syndrome, major depressive disorder and generalized anxiety disorder were assessed. All models were sequentially adjusted for age, sex, highest education, household equivalent income, smoking, physical activity, and mean neighborhood income. RESULTS: As compared with individuals living in rural areas, those in semi-urban or urban areas had a poorer lung function (ß -1.62, 95% CI -2.07;-1.16), and higher prevalence of major depressive disorder (OR 1.65, 95% CI 1.35;2.00), and generalized anxiety disorder (OR 1.58, 95% CI 1.35;1.84). Prevalence of metabolic syndrome, however, was lower in urban areas (OR 0.51, 95% CI 0.44;0.59). These associations were only partly explained by differences in residents' demographic, socioeconomic and lifestyle characteristics and socioeconomic status of the areas. CONCLUSIONS: Our results suggest a differential health impact of urbanity according to type of disease. Living in an urban environment appears to be beneficial for cardiometabolic health but to have a detrimental impact on respiratory function and mental health. Future research should investigate which underlying mechanisms explain the differential health impact of urbanity.

[THE INFLUENCE OF SMOKING ON THE LUNG VENTILATION FUNCTION IN YOUNG SUBJECTS].

The aim of the work was to evaluate effect of smoking on the lung ventilation function in young subjects. The study included 1552 subjects (808 men and 744 women) of the mean age 31.6 ± 4.7 and 29.27 ± 5.3 years respectively divided into 3 groups: smokers (n = 568), ex-smokers (n = 103), and non-smokers (n = 881). A sample of the general population contained 36.6% smokers, 6.6% ex-smokers, and 56.8% non-smokers; it showed significant correlation of smoking habits with the gender and the education level. Functional studies revealed lower spirographic and higher whole-body plethysmographic parameters in the smokers and ex-smokers. Also, they more frequently suffered obstructive disorders. These data suggest negative effect of tobacco smoke on the respiratory system in practically healthy young subjects revealed by the studying external respiratory function with the use of spirographic and whole-body plethysmographic methods.

Integrating pulmonary rehabilitation into the multidisciplinary management of lung cancer: a review.

INTRODUCTION: Lung cancer is the number one cause of cancer related deaths. It is increasingly recognized that a multidisciplinary approach to the diagnosis and management of patients with lung cancer represents the ideal model for health care delivery. Given the high incidence of comorbid lung disease in lung cancer patients, strategies targeted at improving or optimizing these conditions may improve outcomes. Pulmonary rehabilitation (PR) has proven to be a useful management strategy for patients with chronic lung diseases including chronic obstructive pulmonary disease, interstitial lung disease and pulmonary hypertension. DISCUSSION: PR improves both exercise capacity and dyspnea. The effects of PR have also been studied in patients with lung cancer prior to and following surgical resection. Investigators have demonstrated significant improvements in six minute walk distance and lower extremity strength. In addition, patient recovery time is shorter when inpatient pulmonary rehabilitation is integrated prior to or following surgery. There are also positive reports regarding the benefits of exercise training in lung cancer patients receiving definite chemotherapy and radiotherapy. Pilot studies have demonstrated improvement in dyspnea scores as well as exercise capacity objectively measured by six minute walk distance. PR also offers an educational component in which patients have the opportunity to be educated regarding management of their disease as well as discuss goals of care. CONCLUSION: PR can be included as the standard of care for patients with advanced lung cancer with the goal of optimizing quality of life. Here, we provide a review of the current knowledge regarding PR in the management of patients with lung cancer.

Comparison of a self-inflating bulb syringe and a colorimetric CO2 indicator with capnography and radiography to detect the misdirection of naso/orogastric tubes into the airway of critically ill adult patients.

OBJECTIVE: The objective of this study was to develop a mechanism of discovering misdirection into the airway of naso/orogastric (NG) tubes before they reach their full depth of placement in adults. METHODS: A prospective, observational study was performed in humans, evaluating both the self-inflating bulb syringe (SIBS) and a colorimetric CO2 detector. A prospective convenience sample of 257 NG tube placements was studied in 199 patients in medical ICUs of a tertiary care medical center. Findings were compared to a "standard" (ie, end tidal CO2 results of a capnograph and the results of a chest radiograph performed at the completion of the tube placement). RESULTS: On the first tube placement attempt in any patient, the SIBS had a sensitivity of 91.5% and a specificity of 87.0% in detecting nonesophageal placement, while the colorimetric device exhibited 99.4% sensitivity and 91.3% specificity. On subsequent insertions, the SIBS showed 95.7% sensitivity and 100% specificity, while the colorimetric device exhibited 97.8% sensitivity and 100% specificity. The colorimetric device was eight times more expensive than the SIBS. CONCLUSIONS: The SIBS and the colorimetric CO2 detector are very good at detecting NG tube malpositioning into the airway, although the colorimetric device is slightly more sensitive and specific. Neither method adds substantial time or difficulty to the insertion process. The colorimetric device is substantially more expensive. The decision as to which method to use may be based on local institutional factors, such as expense.

Assessment of respiratory system compliance with electrical impedance tomography using a positive end-expiratory pressure wave maneuver during pressure support ventilation: a pilot clinical study.

INTRODUCTION: Assessment of respiratory system compliance (Crs) can be used for individual optimization of positive end-expiratory pressure (PEEP). However, in patients with spontaneous breathing activity, the conventional methods for Crs measurement are inaccurate because of the variable muscular pressure of the patient. We hypothesized that a PEEP wave maneuver, analyzed with electrical impedance tomography (EIT), might be suitable for global and regional assessment of Crs during assisted spontaneous breathing. METHODS: After approval of the local ethics committee, we performed a pilot clinical study in 18 mechanically ventilated patients (61 ± 16 years (mean ± standard deviation)) who were suitable for weaning with pressure support ventilation (PSV). For the PEEP wave, PEEP was elevated by 1 cmH2O after every fifth breath during PSV. This was repeated five times, until a total PEEP increase of 5 cmH2O was reached. Subsequently, PEEP was reduced in steps of 1 cmH2O in the same manner until the original PEEP level was reached. Crs was calculated using EIT from the global, ventral and dorsal lung regions of interest. For reference measurements, all patients were also examined during controlled mechanical ventilation (CMV) with a low-flow pressure-volume maneuver. Global and regional Crs(low-flow) was calculated as the slope of the pressure-volume loop between the pressure that corresponded to the selected PEEP and PEEP +5 cmH2O. For additional reference, Crs during CMV (Crs(CMV)) was calculated as expired tidal volume divided by the difference between airway plateau pressure and PEEP. RESULTS: Respiratory system compliance calculated from the PEEP wave (Crs(PEEP wave)) correlated closely with both reference measurements (r = 0.79 for Crs(low-flow) and r = 0.71 for Crs(CMV)). No significant difference was observed between the mean Crs(PEEP wave) and the mean Crs(low-flow). However, a significant bias of +17.1 ml/cmH2O was observed between Crs(PEEP wave) and Crs(CMV). CONCLUSION: Analyzing a PEEP wave maneuver with EIT allows calculation of global and regional Crs during assisted spontaneous breathing. In mechanically ventilated patients with spontaneous breathing activity, this method might be used for assessment of the global and regional mechanical properties of the respiratory system.

Toxicological assessment of kretek cigarettes Part 3: kretek and American-blended cigarettes, inhalation toxicity.

A typical Indonesian kretek cigarette brand and an experimental kretek reference cigarette were compared to the reference cigarette 2R4F in two 90-day inhalation studies. Male and female rats were exposed nose-only to mainstream smoke for 6 hours daily, for 90 consecutive days. Biological endpoints were assessed according to OECD guideline 413, with special emphasis on respiratory tract histopathology and on lung inflammation (broncho-alveolar lavage fluid levels of neutrophils, macrophages and lymphocytes). Histopathological alterations included: in the nose, hyperplasia and squamous metaplasia of the respiratory epithelium and squamous metaplasia and atrophy of the olfactory epithelium; in the larynx, epithelial squamous metaplasia and hyperplasia; in the lungs, accumulation of macrophages in alveoli and goblet cell hyperplasia in bronchial epithelium. The findings were qualitatively consistent with observations from previous similar studies on conventional cigarettes. Compared to 2R4F cigarette, however, kretek smoke exposure was associated with a pronounced attenuation of pulmonary inflammation and less severe histopathological changes in the respiratory tract. Neutrophilic inflammation was also significantly lower (>70%). These results are consistent with the observations made on smoke chemistry and in vitro toxicology. They do not support any increased toxicity of the smoke of kretek cigarettes compared to conventional American-blended cigarettes.

Toxicological assessment of kretek cigarettes Part 5: mechanistic investigations, inhalation toxicity.

The biological effects of mainstream smoke (MS) from Indonesian-blended cigarettes with and without added cloves, cloves extracted with hot ethanol, and extracted cloves replenished with eugenol or clove oil were assessed in a 90-day inhalation study in rats. A separate 35-day inhalation study in rats was performed with MS from American-blended cigarettes with 0%, 2.5%, 5% or 10% added eugenol. Effects commonly seen in inhalation studies with MS were observed. These included histopathological changes indicative of irritation in the entire respiratory tract and inflammatory responses in the lung. Adding cloves to American- or Indonesian-blended cigarettes reduced the inflammatory response in the lung but with no difference between the two blend types. When the clove oil was extracted (∼ 75% reduction of eugenol achieved) from cloves, the inflammatory response in the lung was still reduced similarly to whole cloves but the severity of histopathological changes in the upper respiratory tract was less reduced. Add back of clove oil or pure eugenol reduced this response to a level similar to what was seen with whole cloves. When eugenol was added to American-blended cigarettes, similar findings of reduced lung inflammation and severity of histopathological changes in respiratory the tract was confirmed. These studies demonstrate a clear effect of cloves, and in particular eugenol, in explaining these findings.

Computational fluid dynamics endpoints for assessment of adenotonsillectomy outcome in obese children with obstructive sleep apnea syndrome.

BACKGROUND: Improvements in obstructive sleep apnea syndrome (OSAS) severity may be associated with improved pharyngeal fluid mechanics following adenotonsillectomy (AT). The study objective is to use image-based computational fluid dynamics (CFD) to model changes in pharyngeal pressures after AT, in obese children with OSAS and adenotonsillar hypertrophy. METHODS: Three-dimensional models of the upper airway from nares to trachea, before and after AT, were derived from magnetic resonance images obtained during wakefulness, in a cohort of 10 obese children with OSAS. Velocity, pressure, and turbulence fields during peak tidal inspiratory flow were computed using commercial software. CFD endpoints were correlated with polysomnography endpoints before and after AT using Spearman׳s rank correlation (rs). RESULTS: Apnea hypopnea index (AHI) decreases after AT was strongly correlated with reduction in maximum pressure drop (dPTAmax) in the region where tonsils and adenoid constrict the pharynx (rs=0.78, P=0.011), and with decrease of the ratio of dPTAmax to flow rate (rs=0.82, P=0.006). Correlations of AHI decrease to anatomy, negative pressure in the overlap region (including nasal flow resistance), or pressure drop through the entire pharynx, were not significant. In a subgroup of subjects with more than 10% improvement in AHI, correlations between flow variables and AHI decrease were stronger than in all subjects. CONCLUSIONS: The correlation between change in dPTAmax and improved AHI suggests that dPTAmax may be a useful index for internal airway loading due to anatomical narrowing, and may be better correlated with AHI than direct airway anatomic measurements.

Computational fluid dynamics for the assessment of upper airway response to oral appliance treatment in obstructive sleep apnea.

Mandibular advancement splints (MAS), which protrude the lower jaw during sleep, are recognized as an effective treatment for obstructive sleep apnea (OSA) through their action of enlarging the airway space and preventing upper airway collapse. However a clinical challenge remains in preselecting patients who will respond to this form of therapy. We aimed to use computational fluid dynamics (CFD) in conjunction with patient upper airway scans to understand the upper airway response to treatment. Seven OSA patients were selected based on their varied treatment response (assessed by the apnea-hypopnoea index (AHI) on overnight polysomnography). Anatomically-accurate upper airway computational models were reconstructed from magnetic resonance images with and without MAS. CFD simulations of airflow were performed at the maximum flow rate during inspiration. A physical airway model of one patient was fabricated and the CFD method was validated against the pressure profile on the physical model. The CFD analysis clearly demonstrated effects of MAS treatment on the patient's UA airflow patterns. The CFD results indicated the lowest pressure often occurs close to the soft palate and the base of the tongue. Percentage change in the square root of airway pressure gradient with MAS (Δsqrt(ΔP(Max))%) was found to have the strongest relationship with treatment response (ΔAHI%) in correlation analysis (r=0.976, p=0.000167). Changes in upper airway geometry alone did not significantly correlate with treatment response. We provide further support of CFD as a potential tool for prediction of treatment outcome with MAS in OSA patients without requiring patient specific flow rates.

Risks of population antimicrobial resistance associated with chronic macrolide use for inflammatory airway diseases.

Macrolide antibiotics have established efficacy in the management of cystic fibrosis and diffuse panbronchiolitis-uncommon lung diseases with substantial morbidity and the potential for rapid progression to death. Emerging evidence suggests benefits of maintenance macrolide treatment in more indolent respiratory diseases including chronic obstructive pulmonary disease and non-cystic fibrosis bronchiectasis. In view of the greater patient population affected by these disorders (and potential for macrolide use to spread to disorders such as chronic cough), widespread use of macrolides, particularly azithromycin, has the potential to substantially influence antimicrobial resistance rates of a range of respiratory microbes. In this Personal View, I explore theories around population (rather than patient) macrolide resistance, appraise evidence linking macrolide use with development of resistance, and highlight the risks posed by injudicious broadening of their use, particularly of azithromycin. These risks are weighed against the potential benefits of macrolides in less aggressive inflammatory airway disorders. A far-sighted approach to maintenance macrolide use in non-cystic fibrosis inflammatory airway diseases is needed, which minimises risks of adversely affecting community macrolide resistance: combining preferential use of erythromycin and restriction of macrolide use to those patients at greatest risk represents an appropriately cautious management approach.