Airway Caliber Research Articles

Variability of lung function and respiratory muscles power in healthy and asthmatic subjects

Airway function is one of the many biologic functions that exhibit circadian variability over 24-h periods. Studies of circadian variability of lung function in normal subjects as well as asthmatics are particularly scarce, and those of MEP and MIP are unknown. The aim of this study to determine circadian variation in lung function (FVC, FEV1 and PEFR) and respiratory muscle pressures(MEP and MIP) for measurement of respiratory muscle power at 6:00am (early morning),12:00midday, 6:00pm( evening) and 12:00 midnight in healthy subjects and in patients with mild asthma at 6:00am and 6:00pm , to elaborate on the possibility of using MEP and MIP variability as a new diagnostic test for asthma. This is a cross sectional study performed in Khartoum, the capital of Sudan during December 2010. Thirty healthy, symptoms free non smokers normal subjects aged 20-64 years selected randomly and 15 mild asthmatics, clinically free during the time of study aged 19-49 years were included in the study. There is significant drop in healthy subjects early in the morning compared to 6:00pm, the drop in FVC was 9.75%, in FEV1 was 8.79%, in PEFR was 8.44%, in MEP was 10.04%, and in MIP was 17.57%. There is also significant drop in asthmatics early in the morning in MEP and MIP (21.76%, 27.57% respectively), is comparable to FEV1 (22.56%) and PEFR (23.86%). The sensitivity and specificity of variability for MEP (53%, 77%) and MIP (60%, 63%) comparable to sensitivity and specificity of FEV1 variability (40%, 86%) and PEFR variability (46%, 73%). The obtained comparable results of MEP, MIP variability to FEV1, PEFR variability in normal and asthmatic subjects could imply that MEP & MIP can be used in assessing airway calibre as in asthma. The study concluded that MEP & MIP variability could be sensitive tests to confirm asthma diagnosis.

MRI-based methodology to monitor the impact of positional changes on the airway caliber in obstructive sleep apnea patients

PurposeTo develop a non-invasive MRI-based methodology to visually and quantitatively assess the impact of head and chest rotations on the airway caliber. MethodsAn MRI table set-up was developed for independent rotations of the head and chest along B0 field and tested for feasibility using phantom scans. The accuracy of the head and chest rotations was validated with ten volunteer scans. A 3T MRI protocol was optimized to image the regions of interest (ROIs) that were the retropalatal (RP) and retroglossal (RG) sections of the upper airway. A workflow for data analysis was developed to assess the changes of the airway caliber following the independent head and chest rotations. ResultsA prototype MRI table setup was established with two separate plates each supporting and rotating the head or chest independently. Subject positioning and image acquisition were finished within seven minutes for each position. Thus, each subject MRI was set up with seven positions and completed for less than one hour. The implemented angles were within 0.3-degree deviation from the targeted angles. The data analysis workflow provided 2D and 3D visualization and quantification with the measurements of cross-sectional area, lateral and anterior-posterior distances of the ROIs. Sharp contrast of the airway and its surrounding tissues facilitated an automatic approach to ROI placement to minimize subjectivity. ConclusionsThe 3T MRI data acquisition and analysis methodology could reliably assess the impact of head and chest rotations on the upper airway caliber to identify the optimal position for obstructive sleep apnea patients.

Pulmonary Smooth Muscle in Vertebrates: A Comparative Review of Structure and Function.

Although the airways of vertebrates are diverse in shape, complexity, and function, they all contain visceral smooth muscle. The morphology, function, and innervation of this tissue in airways is reviewed in actinopterygians, lungfish, amphibians, non-avian reptiles, birds, and mammals. Smooth muscle was likely involved in tension regulation ancestrally, and may serve to assist lung emptying in fishes and aquatic amphibians, as well as maintain internal lung structure. In certain non-avian reptiles and anurans antagonistic smooth muscle fibers may contribute to intrapulmonary gas mixing. In mammals and birds, smooth muscle regulates airway caliber, and may be important in controlling the distribution of ventilation at rest and exercise, or during thermoregulatory and vocal hyperventilation. Airway smooth muscle is controlled by the autonomic nervous system: cranial cholinergic innervation generally causes excitation, cranial non-adrenergic, non-cholinergic innervation causes inhibition, and spinal adrenergic (SA) input causes species-specific, often heterogeneous contractions and relaxations.

Cortical control of upper airway calibre: It's the thought that counts!

Cortical control of upper airway calibre: It's the thought that counts!

Airway Caliber is Linked to Wall Thickness in Mice: Implications for Morphometry

Morphometry of lung tissues often involves evaluation for changes in airway wall components such as collagen and/or smooth muscle. Alterations of these tissue parameters may be markers of diseases like asthma, chronic obstructive pulmonary disease or cystic fibrosis. The mouse lung is composed of airways that exhibit monopodial branching during development and these intrapulmonary airways are exclusively bronchioles (i.e. no intra‐pulmonary bronchi). As such, many airways can look alike for analysis by inexperienced observers. We tested if the airway caliber in wild type B6 mice could influence the detection and scoring of airway collagen or smooth muscle composition. We examined 15 lungs from archival blocks that came from studies with appropriate institutional approvals. Airway lumen diameter as well as wall thickness (sum of epithelium, smooth muscle and collagen) measurements of the 2 largest and 2 smallest airways were taken. These were then cumulatively analyzed for wall thickness (y axis) and airway lumen diameter (x axis). There was a significant positive slope (P=0.0017). We then grouped the data into large (lumen >130 microns) and small (lumen <130 microns) airways and compared the wall thickness, which was significantly thicker in the larger airways (P<0.0001). These data indicate that morphometry of murine airways requires analysis of similar sized airways for accurate assessment of changes and we speculate this finding will be relevant across other species as well.Support or Funding InformationNAThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Particles in the lungs of patients with chronic bronchitis—part 1: deposition modeling

Background: Chronic bronchitis represents a lung disease which is characterized by a non-reversible reduction of the airway calibers and, as a consequence of that, by a continuous widening of the terminal lung structures. In the present contribution the behavior of inhaled particles in bronchitis lungs is submitted to a detailed theoretical investigation, thereby using a well-validated deposition model. Methods: Any changes of the bronchial airway architecture and alveolar region were modeled by application of well-defined scaling procedures, where random reductions of tubular and spherical diameters are considered. Transport and deposition of particles were simulated by using a random-walk approach including the Monte Carlo method. For the computation of random particle paths a stochastic lung architecture was assumed. Particle deposition was modeled with the help of empirical and analytical formulae describing the physical mechanisms exerting on the particulate substances. Simulations were carried out for male adult lungs and two different breathing conditions. Results: With regard to submicron particles differences of total deposition between bronchitis patients and healthy controls range from 5% to 10%. In the case of particles exceeding a size of 1 µm these discrepancies may be increased to 20%. For most particle sizes chronic bronchitis results in a significant enhancement of tubular (= bronchial + ductal) and alveolar deposition. A change of the breathing conditions from sitting inhalation to light-work inhalation has only minor consequences for total and regional deposition, whereby small particles ( Conclusions: Based on the theoretical results presented in this study it may be concluded that particle deposition is remarkably increased in bronchitis patients with respect to healthy controls. Detailed knowledge of these modifications may be regarded as essential basis for the optimization of inhalation therapies, where high amounts of inhaled aerosol particles have to be delivered to respective target regions.

Pharyngeal distensibility during expiration is an independent predictor of the severity of obstructive sleep apnoea.

Pharyngeal distensibility and collapsibility reflect the passive properties of tissue in the airway, are an indicator of the ease with which an airway can be deformed and are related to the severity of obstructive sleep apnoea (OSA). During normal tidal respiration, the collapsibility of the pharynx during expiration is passive without confounding by neuromuscular activation that occurs during inspiration. We evaluated the distensibility and collapsibility of the upper airway in subjects with OSA during wakefulness using sophisticated dynamic computed tomography (CT) imaging. We hypothesized that the dynamic changes of the upper airway during expiration would be related to the severity of OSA. Twenty-three patients with OSA and eight normal subjects underwent simultaneous measurement of respiratory flow and airway calibre using ultrafast CT. The change in pharyngeal cross-sectional area divided by the change in concomitant flow (as distensibility or collapsibility) was measured and compared across different severities of OSA. The slope of this relationship between delta area and delta flow during expiration was significantly higher in severe OSA when compared with normal controls and mild-moderate OSA. Differences in airway distensibility or collapsibility between severity groups were significant in expiration but not in inspiration. Distensibility or collapsibility contributed most to the apnoea-hypopnoea index in regression modelling. Age, gender, and body mass index (BMI) were not significant independent predictors. Our study demonstrates that airway distensibility during the expiratory phase of awake respiration is correlated with the severity of OSA.

Microscale to mesoscale analysis of parenchymal tethering: the effect of heterogeneous alveolar pressures on the pulmonary mechanics of compliant airways.

In the healthy lung, bronchi are tethered open by the surrounding parenchyma; for a uniform distribution of these peribronchial structures, the solution is well known. An open question remains regarding the effect of a distributed set of collapsed alveoli, as can occur in disease. Here, we address this question by developing and analyzing microscale finite-element models of systems of heterogeneously inflated alveoli to determine the range and extent of parenchymal tethering effects on a neighboring collapsible airway. This analysis demonstrates that micromechanical stresses extend over a range of ∼5 airway radii, and this behavior is dictated primarily by the fraction, not distribution, of collapsed alveoli in that region. A mesoscale analysis of the microscale data identifies an effective shear modulus, Geff, that accurately characterizes the parenchymal support as a function of the average transpulmonary pressure of the surrounding alveoli. We demonstrate the use of this formulation by analyzing a simple model of a single collapsible airway surrounded by heterogeneously inflated alveoli (a "pig-in-a-blanket" model), which quantitatively demonstrates the increased parenchymal compliance and reduction in airway caliber that occurs with decreased parenchymal support from hypoinflated obstructed alveoli. This study provides a building block from which models of an entire lung can be developed in a computationally tenable manner that would simulate heterogeneous pulmonary mechanical interdependence. Such multiscale models could provide fundamental insight toward the development of protective ventilation strategies to reduce the incidence or severity of ventilator-induced lung injury. NEW & NOTEWORTHY A destabilized lung leads to airway and alveolar collapse that can result in catastrophic pulmonary failure. This study elucidates the micromechanical effects of alveolar collapse and determines its range of influence on neighboring collapsible airways. A mesoscale analysis reveals a master relationship that can that can be used in a computationally efficient manner to quantitatively model alveolar mechanical heterogeneity that exists in acute respiratory distress syndrome (ARDS), which predisposes the lung to volutrauma and/or atelectrauma. This analysis may lead to computationally tenable simulations of heterogeneous organ-level mechanical interactions that can illuminate novel protective ventilation strategies to reduce ventilator-induced lung injury.

Disparate diagnostic accuracy of lung function tests as predictors of poor asthma control in children

Rationale: In practice, asthma control is assessed according to symptom burden and office spirometry. However, spirometry poorly tests peripheral lung function, which may be abnormal in asthma. Impluse oscillometry (IOS) and multiple-breath washout (MBW) are novel methods which measure reactance (X5) and ventilation heterogeneity (VH) in the peripheral lung, but how well these tests reflect asthma control is poorly understood. Objective: To compare the diagnostic accuracy of tests of large airways caliber (FEV1, FEV1/FVC, R20), peripheral zone properties (X5, VH), and airways inflammation (FeNO) as predictors of poor control in asthmatic children (44 poorly controlled/10 controlled). Methods: 54 children enriched in severe asthma completed a symptom-based control scale (ACT/cACT) and lung function tests after overnight bronchodilator withhold. The accuracy of each variable to predict poor control was ranked by area under the receiver operating characteristic (ROC) curve, sensitivity and specificity. Results: Among measures of large airways caliber, the FEV1% had the highest ROC curve area, with low sensitivity but perfect specificity. Among measures of peripheral lung function, X5 and VH in the conducting zone had fair curve areas with higher sensitivity but lower specificity compared to the FEV1%. VH in the acinar zone and FeNO both had poor accuracy. Conclusion: Tests of large airway and peripheral zone lung function performed disparately as predictors of poor control in a sample of children enriched in severe asthma. Further studies in a larger sample with more diverse phenotypic features are necessary to validate this preliminary conclusion.

Association Between Red Blood Cell Distribution Width and Outcomes of Open Airway Reconstruction Surgery in Adults

Airway reconstruction for adults with laryngotracheal stenosis (LTS) is directed toward improving airway caliber to mitigate the patient's dyspnea and achieve prosthesis-free breathing (ie, without tracheostomy, intraluminal stent, or T-tube). Despite the importance of preoperative risk stratification to minimize postoperative complications, consensus on an objective predictive algorithm for open airway reconstruction is lacking. To determine whether the ability to achieve a prosthesis-free airway in adults after open airway reconstruction is associated with red blood cell distribution width (RDW) at the time of surgery. Case series study investigating 92 consecutive patients 18 years and older with laryngotracheal stenosis who underwent open airway reconstruction at a US tertiary care hospital from January 1, 2006, to January 1, 2017. The main outcome was a prosthesis-free airway (absence of tracheostomy, intraluminal stent, or T-tubes) at last follow-up. Multivariate logistic regression modeling was used to identify independent factors associated with this outcome. Of the 92 patients who met inclusion criteria, the median (interquartile range) age was 44 (33.0-60.3) years; 50 (53%) were female, and 82 (89%) were white. In all, 74 patients (80%) were prosthesis free at the last follow-up (mean, 833 days; 95% CI, 10-4229 days). In multivariate analyses, airway decannulation was significantly correlated with reduced RDW (odds ratio [OR], 0.40; 95% CI, 0.19-0.84) and the absence of posterior glottic stenosis (OR, 0.12; 95% CI, 0.04-0.37). These data suggest that surgical success in open airway reconstruction is significantly associated with RDW and whether the patient had posterior glottic stenosis. The RDW is a routine laboratory parameter that may provide some insight to the preoperative probability of prosthesis removal, facilitate risk stratification, promote informed patient decision making, and optimize health care resource management.

Individual Airway Closure Characterized In Vivo by Phase-Contrast CT Imaging in Injured Rabbit Lung.

Airway closure is involved in adverse effects of mechanical ventilation under both general anesthesia and in acute respiratory distress syndrome patients. However, direct evidence and characterization of individual airway closure is lacking. Here, we studied the same individual peripheral airways in intact lungs of anesthetized and mechanically ventilated rabbits, at baseline and following lung injury, using high-resolution synchrotron phase-contrast CT. Laboratory animal investigation. European synchrotron radiation facility. Six New-Zealand White rabbits. The animals were anesthetized, paralyzed, and mechanically ventilated in pressure-controlled mode (tidal volume, 6 mL/kg; respiratory rate, 40; FIO2, 0.6; inspiratory:expiratory, 1:2; and positive end-expiratory pressure, 3 cm H2O) at baseline. Imaging was performed with a 47.5 × 47.5 × 47.5 μm voxel size, at positive end-expiratory pressure 12, 9, 6, 3, and 0 cm H2O. The imaging sequence was repeated after lung injury induced by whole-lung lavage and injurious ventilation in four rabbits. Cross-sections of the same individual airways were measured. The airways were measured at baseline (n = 48; radius, 1.7 to 0.21 mm) and after injury (n = 32). Closure was observed at 0 cm H2O in three of 48 airways (6.3%; radius, 0.35 ± 0.08 mm at positive end-expiratory pressure 12) at baseline and five of 32 (15.6%; radius, 0.28 ± 0.09 mm) airways after injury. Cross-section was significantly reduced at 3 and 0 cm H2O, after injury, with a significant relation between the relative change in cross-section and airway radius at 12 cm H2O in injured, but not in normal lung (R = 0.60; p < 0.001). Airway collapsibility increases in the injured lung with a significant dependence on airway caliber. We identify "compliant collapse" as the main mechanism of airway closure in initially patent airways, which can occur at more than one site in individual airways.

Revisiting atelectasis in lung units with low ventilation/perfusion ratios.

Patients on high inspired O2 concentrations are at risk of atelectasis, a problem that has been quantitatively assessed using analysis of ratio of ventilation to perfusion (V̇a/Q̇) equations. This approach ignores the potential of the elastic properties of the lung to support gas exchange through "apneic" oxygenation in units with no tidal ventilation, and is based on an error in the conservation of mass equations. To fill this gap, we correct the error and compare the pressure drops associated with apneic gas exchange with the pressure differences that can be supported by lung recoil. We analyze a worst case scenario: a small test unit in the Weibel model A tree structure with zero tidal ventilation, 100% inspired O2, the rest of the lung being normally ventilated tidally. We first computed the gas flux to the (unventilated) test unit and estimated the associated pressure drops. We then computed the difference in local gas pressure relative to the surrounding lung that would cause the unit to collapse. We compared these two, and finally computed the degree of airway narrowing that would effect change from the stable (apneic gas exchange) regime to the unstable regime leading to collapse. We find that except under extreme conditions of loss of airway caliber exceeding roughly 90%, lung recoil is sufficient to maintain oxygenation through convective transport alone. We further argue that the fundamental V̇a/Q̇ equations are invalid in these circumstances, and that the issue of atelectasis in low V̇a/Q̇ will require modifications to account for this additional mode of gas exchange. NEW & NOTEWORTHY Breathing high concentrations of oxygen increases the likelihood of atelectasis because of oxygen absorption, which is thought to be inevitable in regions with relatively low ventilation/perfusion ratios. However, airspaces of the lung resist collapse because of the forces of interdependence, and can, with low or even zero active tidal ventilation, draw in an inspiratory flow of oxygen sufficient to replace the oxygen consumed, thus preventing collapse of airspaces served by all but the most narrowed airways.

Dynamic Upper Airway Imaging during Wakefulness in Obese Subjects with and without Sleep Apnea.

Obesity is a major risk factor for obstructive sleep apnea. Although greater dimensional changes in the upper airway during wake respiration have been noted in patients with apnea compared with control subjects, whether these differences remain in the presence of obesity is unknown. To evaluate upper airway anatomic characteristics and airway compliance (distensibility) in obese subjects with obstructive sleep apnea compared with obese control subjects. Dynamic magnetic resonance imaging was performed in 157 obese subjects with apnea and 46 obese control subjects during wakefulness in the midsagittal and three axial upper airway regions (retropalatal, retroglossal, epiglottal). Differences in measurements between subjects with apnea and control subjects, and correlations with apnea-hypopnea index among subjects with apnea, were examined. Measurements included airway areas and linear dimensions. Subject-specific coefficients of variation were calculated to examine variability in airway size. Controlling for covariates, the retropalatal area during respiration was significantly smaller in subjects with apnea than control subjects, based on the average (P = 0.003), maximum (P = 0.004), and minimum (P = 0.001) airway area. Airway narrowing was observed in anteroposterior and lateral dimensions (adjusted P < 0.05). Results were similar in an age, sex, and body mass index-matched subsample. There were significant correlations between apnea-hypopnea index and dynamic measures of airway caliber in the retropalatal and retroglossal regions among subjects with apnea. Upper airway caliber during respiration was significantly narrower in obese subjects with apnea than obese control subjects in the retropalatal region. These findings provide further evidence that retropalatal airway narrowing plays an important role in the pathogenesis of obstructive sleep apnea in obese subjects.

Genioglossus activation during maximal sniff manoeuvres: Is upper airway function relevant in the clinical assessment of inspiratory and expiratory muscle strength?

Genioglossus activation during maximal sniff manoeuvres: Is upper airway function relevant in the clinical assessment of inspiratory and expiratory muscle strength?

Diagnostic étiologique d’une dilatation des bronches

Bronchiectasis is defined by a permanent and irreversible increase in airway caliber. Computed tomography (CT) scan is required for diagnosis and allows differentiating localized (affecting only one lobe) from diffuse (affecting two or more lobes) bronchiectasis. Localized bronchiectasis is usually related to a local cause (e.g., tumor, compression by lymph nodes, foreign body) whereas there are multiple causes of diffuse bronchiectasis. Main causes of diffuse bronchiectasis can be grouped into 5 categories: (1) immune deficiencies; (2) genetic disorders responsible for abnormal mucociliairy clearance (e.g., cystic fibrosis and primary ciliary dyskinesia); (3) autoinflammatory and connective tissue diseases (e.g., rheumatoid arthritis, Sjogren syndrome); (4) chronic airway inflammatory disorders (e.g., allergic broncho-pulmonary aspergillosis) or chronic infections (e.g., by nontuberculous mycobacteria) and; (5) sequelae of pulmonary insults (e.g., infection, radiotherapy). In the absence of a specific cause, bronchiectasis are called idiopathic. Bronchoscopy is the cornerstone for etiological diagnosis in localized bronchiectasis. Investigation of diffuse bronchiectasis includes standardized biological tests, eventually completed by specialized explorations (e.g., analysis of epithelial ion transport and/or ciliary beating). After this systematic approach, an etiological diagnosis is obtained in approximately 60% of cases, often resulting in therapeutic consequences and in some cases in genetic counselling.

Correlation of Various Anthropometric and Craniofacial Variables with Severity of Obstructive sleep Apnea in Indian Population

Ethnic craniofacial morphology differences significantly affect upper airway caliber and thus apnea–hypopnea index (AHI). As there is very limited data available from India regarding factors influencing severity of obstructive sleep apnea (OSA), we tried to explore whether anthropometric and craniofacial variable predict severity of OSA. To find out correlation of simple clinical examination of craniofacial morphology and anthropometric measurements with severity of OSA in Indian population. We studied consecutive OSA patients between June 2015 and September 2016. Detailed history, physical examination (including anthropometry, clinical craniofacial assessment) and Level I polysomnography was done. Anthropometric and craniofacial parameters were correlated with AHI, nadir oxygen and percent of total time with oxygen saturation level lower than 90% during sleep (T < 90%). Out of 193 patients, 148 (76.6%) were males and 45 (23.3%) were females with ratio of 3.28:1. Mean age, mean body mass index (BMI) and mean AHI of cohort were 50.24 ± 1.65 years, 30.20 ± 0.84 kg/m2, and 53.83 ± 4.8 events per hour, respectively. With respect to AHI, nadir oxygen and T < 90%, statistically significant correlation was found for modified Mallampati class (p value = 0.001, = 0.009, = 0.002, respectively), waist circumference (p value = 0.002, < 0.001, = 0.001, respectively), neck circumference (p value < 0.001, < 0.001, < 0.001, respectively), BMI WHO cut off (p value < 0.001, < 0.001, < 0.001, respectively), and BMI Asian Indian cut off (p value = 0.001, < 0.001, < 0.001, respectively). Anthropometric and craniofacial variables are easy to perform clinical examinations. Higher modified Mallampati class, WC, NC, BMI, large tonsils and micrognathia are associated with more severe OSA.

Predictors of Obtaining Polysomnography Among Otolaryngologists Prior to Adenotonsillectomy for Childhood Sleep-Disordered Breathing.

(1) To assess the predictors for obtaining polysomnography (PSG) in children undergoing adenotonsillectomy (AT) for sleep-disordered breathing, and (2) to estimate the adherence to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guideline recommendations for pre-AT PSG. This was a retrospective cohort study of children who were seen in the Pediatric Otolaryngology Clinic and underwent AT for sleep-disordered breathing over a 13-month period at a single tertiary care children's hospital. Patients with and without pre-AT PSG were compared using bivariate and logistic regression analysis to identify predictors for PSG. Electronic medical records were reviewed for demographic variables, medical comorbidities, and PSG data. Adherence to AAO-HNS guideline recommendations was estimated by calculating the proportion of patients who had a PSG among those who met the recommended criteria for pre-AT PSG. Mean age was 6.6 ± 3.6 years with 53% male. A total of 65 of 324 children (20%) underwent PSG prior to AT. The only factor significantly associated with pre-AT PSG was age 1 to 3 years (odds ratio 4.5, 95% confidence interval [2.2, 9.0], P < .001). Among patients who met AAO-HNS criteria for pre-AT PSG, 28 of 128 (20%) underwent PSG compared to 35 of 186 (19%) who did not meet criteria (odds ratio 1.0, 95% confidence interval [0.6, 1.9], P = .87). Among children who underwent AT, the only significant predictor of obtaining pre-AT PSG was age 1 to 3 years. The rate of adherence to the AAO-HNS guideline recommendations was low (20%), which represents an educational opportunity.

Respiratory Care for the Ventilated Neonate.

Invasive ventilation is often necessary for the treatment of newborn infants with respiratory insufficiency. The neonatal patient has unique physiological characteristics such as small airway caliber, few collateral airways, compliant chest wall, poor airway stability, and low functional residual capacity. Pathologies affecting the newborn's lung are also different from many others observed later in life. Several different ventilation modes and strategies are available to optimize mechanical ventilation and to prevent ventilator-induced lung injury. Important aspects to be considered in ventilating neonates include the use of correct sized endotracheal tube to minimize airway resistance and work of breathing, positioning of the patient, the nursing care, respiratory kinesiotherapy, sedation and analgesia, and infection prevention, namely, the ventilator-associated pneumonia and nosocomial infection, as well as prevention and treatment of complications such as air leaks and pulmonary hemorrhage. Aspects of ventilation in patients under ECMO (extracorporeal membrane oxygenation) and in palliative care are of increasing interest nowadays. Online pulmonary mechanics and function testing as well as capnography are becoming more commonly used. Echocardiography is now a routine in most neonatal units. Near infrared spectroscopy (NIRS) is an attractive tool potentially helping in preventing intraventricular hemorrhage and periventricular leukomalacia. Lung ultrasound is an emerging tool of diagnosis and can be of added value in helping monitoring the ventilated neonate. The aim of this scientific literature review is to address relevant aspects concerning the respiratory care and monitoring of the invasively ventilated newborn in order to help physicians to optimize the efficacy of care.

Abstract O-38: BIODEGRADEBLE STENTS CAN RESTORE AIRWAY PATENCY FOLLOWING BRONCHIAL COMPRESSION BY A DILATED LEFT ATRIUM IN CRITICALLY ILL CHILDREN

Aims & Objectives: Vascular compression of the left main bronchus can occur due to left atrial enlargement, secondary to congenital or acquired heart disease. In severe cases this can result in ventilator dependence. A bronchial stent may improve symptoms. Metal stents have been associated with vascular erosion and deemed very high risk in this patient group. We report our experience using a biodegradable polydioxanone stent in the left main bronchus in 5 children with cardiac disease and ventilator dependance. Methods Bedside flexible bronchoscopy was performed on paediatric intensive care and the anatomical relationship between cardiac structures and the bronchus was investigated with contrast enhanced computed tomography. 5 patients (weight range 1.8kg to 31kg) were identified and had biodegradable left main bronchial stents inserted under fluoroscopic guidance. Stents were custom designed and deliberately downsized by 50 to 70% of expected airway calibre. Results Stents were inserted without complication under fluoroscopic guidance. All patients experienced improvement in symptoms over time. In three patients subsequent bronchial stenting was performed where degradation preceded relief of vascular compression. No stents migrated with no evidence of bronchial or vascular erosion. (figure 1 shows radiological progression in one patient pre and post stent insertion A to D). There was one death, unrelated to stenting and all remaining survivors are well at 2 year follow up.Conclusions The use of biodegradable stents was safe in this cohort of critically ill patients with vascular bronchial compression. There use provided a temporary improvement in airway calibre which aided weaning from mechanical ventilation and supported eventual cardiac recovery.

Gender differences in chronic obstructive pulmonary diseases: a narrative review.

Chronic obstructive pulmonary disease (COPD) is generally considered to be prevalent in males. However, smoking is rising in women in developing and developed countries, while exposure to biomass fuel for domestic purposes is a recognized risk factor among females. Females developing more severe COPD patterns due to tobacco exposure than men may be due to a genetic predisposition, a greater dose-dependent effect of smoke related to smaller airways caliber and an increased oxidative stress with augmented TGF-beta1 signaling. Gender hormones also seem to be involved in tobacco-smoke metabolism and in lung and pulmonary development. while menopause is associated with accelerated alveolar loss and decline of lung function pulmonary function. The time to diagnosis differs between the sexes since a lower rate of spirometry is performed in women. Also, comorbidities vary between genders: osteoporosis, inflammatory bowel diseases, reflux, hypertension, rheumatoid arthritis, and mental diseases are more common in women. Women pay more attention to breathlessness, maybe due to higher emotional response and anxiety. These elements could lead to higher hospitalization rates in women. The aim of this review is to provide the available evidence with the aim of inviting healthcare professionals to evaluate gender differences in patients with COPD, key point for optimizing the care plan.