Total Airway Resistance Research Articles

Aerodynamics Analysis of the Impact of Nasal Surgery on Patients with Obstructive Sleep Apnea and Nasal Obstruction

Objective: The purpose of this study was to evaluate the effects of nasal surgery on airflow characteristics in patients with obstructive sleep apnea (OSA) by comparing the alterations of airflow characteristics within the nasal and palatopharyngeal cavities. Methods: Thirty patients with OSA and nasal obstruction who underwent nasal surgery were enrolled. A pre- and postoperative 3-dimensional model was constructed, and alterations of airflow characteristics were assessed using the method of computational fluid dynamics. The other subjective and objective clinical indices were also assessed. Results: By comparison with the preoperative value, all postoperative subjective symptoms statistically improved (p < 0.05), while the Apnea-Hypopnea Index (AHI) changed little (p = 0.492); the postoperative airflow velocity and pressure in both nasal and palatopharyngeal cavities, nasal and palatopharyngeal pressure differences, and total upper airway resistance statistically decreased (all p < 0.01). A significant difference was derived for correlation between the alteration of simulation metrics with subjective improvements (p < 0.05), except with the AHI (p > 0.05). Conclusion: Nasal surgery can decrease the total resistance of the upper airway and increase the nasal airflow volume and subjective sleep quality in patients with OSA and nasal obstruction. The altered airflow characteristics might contribute to the postoperative reduction of pharyngeal collapse in a subset of OSA patients.

Effectiveness of endoscopic intranasal incision reduction for nasal fractures

PurposeTo report our experience using endoscopic intranasal incision reduction (EIIR) for nasal fractures and to assess effectiveness of the method.Methods30 patients who underwent EIIR were retrospectively analysed. All the patients were examined by three-dimensional computed tomography (3D CT), acoustic rhinometry and rhinomanometry, preoperatively and postoperatively at 1 month. The visual analogue scale (VAS) was used to assess the preoperative aesthetics and nasal airflow satisfaction and at 1, 3 and 6 months postoperatively. VAS aesthetic satisfaction was also scored by two junior doctors.Results3D CT showed that the fracture fragments fitted well in 30 patients postoperatively at 1 month. VAS aesthetics and nasal airflow scores were significantly improved postoperatively at 1, 3 and 6 months compared with preoperative scores (P < 0.01). The VAS aesthetic scores from the two surgeons were also significantly improved (P < 0.01). The minimal cross-sectional area increased from 0.39 ± 0.13 to 0.64 ± 0.13 (P < 0.001), the nasal volume increased from 4.65 ± 0.86 to 6.37 ± 0.94 (P < 0.001) and the total inspiratory airway resistance of the bilateral nasal cavity median decreased from 0.467 Pa/mL/s to 0.193 Pa/mL/s (P < 0.001). There were no technique-related intraoperative complications.ConclusionEIIR was a practical choice, and the aesthetics and nasal airflow were significantly improved in patients with overlapped and displaced bone fragments, patients with fractures of the frontal process of the maxilla (FFPM), patients who underwent failed CR and patients beyond the optimal temporal window.

Assessment of airway reversibility in asthmatic children using forced oscillation technique - A single-center experience from North India.

Background:Lung function testing is recommended for the management of asthma. Due to certain limitations of conventional spirometry in vulnerable patients, forced oscillation technique (FOT) has been studied with promising results. As there is a paucity of data from developing world, we planned to conduct this study in children using FOT. To assess airway reversibility after inhaled salbutamol in asymptomatic children with suspected asthma.Settings:This study was conducted at pediatric asthma clinic of a tertiary care referral hospital in North India.Design:This was a prospective interventional study over 1-year period.Subjects and Methods:Asymptomatic children between 2 and 18 years of age, with history suggestive of asthma, were eligible for participation. Baseline and postbronchodilator pulmonary functions were assessed using FOT. Airway resistance and reactance were monitored at various frequencies. SPSS version 17 was used for statistical analysis.Results:Among the 345 enrolled children, baseline mean ± standard deviation total airway resistance (R5), central airway resistance (R19), peripheral airway resistance (R5–R19), reactance (X5), and resonant frequency (Fres) were 6.85 ± 2.60, 5.23 ± 1.93, 1.6 ± 1.16, and − 2.54 ± 1.36 cmH2O/L/s and 17.28 ± 3.06 Hz. The median (interquartile range) percentage change after inhaled salbutamol was 19.9 (11.40, 29.12), 22.86 (6.88, 38.76), 14.08 (3.40, 22.62), 39.20 (8.20, 62.39), and 15.79 (8.33, 27.27) in respective parameters. All changes were statistically significant. The studied respiratory variables were in maximum negative correlation with height, followed by body mass index.Conclusions:FOT is a simple technique for monitoring lung functions in children during asthma management.

Personal Exposure to PM2.5 Oxidative Potential in Association with Pulmonary Pathophysiologic Outcomes in Children with Asthma.

Fine particulate matter (PM2.5) with a higher oxidative potential has been thought to be more detrimental to pulmonary health. We aim to investigate the associations between personal exposure to PM2.5 oxidative potential and pulmonary outcomes in asthmatic children. We measured each of the 43 asthmatic children 4 times for airway mechanics, lung function, airway inflammation, and asthma symptom scores. Coupling measured indoor and outdoor concentrations of PM2.5 mass, constituents, and oxidative potential with individual time-activity data, we calculated 24 h average personal exposures 0-3 days prior to a health outcome measurement. We found that increases in daily personal exposure to PM2.5 oxidative potential were significantly associated with increased small, large, and total airway resistance, increased airway impedance, decreased lung function, and worsened scores of individual asthma symptoms and the total symptom score. Among the PM2.5 constituents, organic matters largely of indoor origin contributed the greatest to PM2.5 oxidative potential. Given that the variability in PM2.5 oxidative potential was a stronger driver than PM2.5 mass for the variability in the respiratory health outcomes, it is suggested to reduce PM2.5 oxidative potential, particularly by reducing the organic matter constituent of indoor PM2.5, as a targeted source control strategy in asthma management.

Multimodal longitudinal respiratory function assessment in very low birth weight 7-year-old children

PurposePreterm birth is associated with adverse pulmonary outcomes. We aimed to evaluate respiratory morbidities and lung function of very low birth weight (VLBW) Polish children followed up at the age of 7 years old, and to compare with electrical impedance segmentography (EIS) results recorded at 4 years of age. Materials and methodsVLBW children were compared with term controls using impulse oscillometry and spirometry. Perinatal data and current respiratory morbidities were analyzed and pulmonary function test results were compared with previous EIS results. ResultsWe included 40 VLBW children and 30 controls in the analysis. Elevated total airway resistance and forced expiratory volume in the first second below the lower limit of normal were more prevalent in VLBW children compared with term controls (15 vs 0%; 18 vs 0%). A positive bronchodilator response was more common in VLBW children (R5 Hz: 46 vs 13.3%; R5–20 ​Hz: 65 vs 36.7%). Children with bronchopulmonary dysplasia (BPD) had higher total airway resistance (R5 Hz/R5 Hz pred: 1.35 vs 0.95; p ​< ​0.001), large airway resistance (R20 Hz/R20 Hz pred: 0.89 vs 0.66; p ​= ​0.001), small airway resistance (R5–20 ​Hz: 0.57 vs 0.34 ​kPa ​L−1 ​s−1; p ​= ​0.009), than controls. Strong correlation between BDR in EIS and R5 Hz/R5 Hz pred was observed in children with BPD (r ​= ​0.7). ConclusionVLBW school-aged children with BPD presented with substantial respiratory morbidity and persistent reduction of lung function, affecting small and large airways and lung parenchyma. EIS may be an alternative tool for lung function assessment in children with BPD.

Determination of Airways Resistance, Volumetric Efficiency and Development of Ventilation Model of Rosh Pinah Zinc Mine Namibia

A quantitative technique was conducted at Rosh Pinah Zinc mine, Namibia with its main purpose to determine airways resistance which is a function of the parameters; roughness of the airways and the friction factor. The 32 branch points (i.e. a-ag) that stand for ventilation circuit have been selected. Data collected includes, length and width of airways, air velocity; air density, and roughness of the airways which were used to determine coefficient of frictions, friction factors and airway resistances. A ventilation model was developed. In order to improve the current ventilation model, airways resistance of the mine was determined and simulated in a modified model using VentSimTM software. An average total airways resistance of 0.32027 Ns2/m8 has been achieved for Rosh Pinah mine. It should be pointed out that, as the mine advances its production faces deeper, this value would increases suddenly. Simulation revealed that as much as 34.4 m3/s of air can be received at the production faces, compared to the measured received amount of 19.3 m3/s. Therefore, volumetric efficiency of the mine was improved from 29.3% to 68.3%. It was also noticed that after importing the resistance values into the model together with other parameters, the model was greatly improved and no cause for concern.

Forced expiratory flow during 25%-75% of expiration in middle aged obese and non-obese females – A comparitive study

Introduction: Obesity can cause various health hazards in women in many ways. Overweight or being obese is associated with various risk factors like diabetes and coronary artery disease in women. The incidence of obesity is increasing worldwide. Obesity can cause alteration in pulmonary function which may lead to early morbidity and mortality. FEF 25%-75% is one of the most effort independent portion of the curve, more sensitive parameter to airflow in peripheral airways, where disease of chronic airflow obstruction can begin. Reduced Expiratory Flow rate value in obese individuals may be probably due to increase in the total peripheral resistance and airway resistance with obesity. Hence the present study was undertaken to know the impact of obesity on Forced Expiratory Flow rate25%-75% in middle aged obese females. Aims and Objectives: The present study was conducted ` to compare Pulmonary function test parameter FEF 25%-75% in middle aged obese and non-obese females, to determine the impact of obesity on FEF25%-75%. Materials and Methods: Dynamic Pulmonary Function tests (PFTs) of 50 normal, healthy, non-obese middle aged females and 50 healthy but obese middle aged females, age group 30-45 years of Hubli city were determined and were compared with its normal counterparts. Study subjects were classified into obese and non-obese based on WHO classification of BMI. To obtain the dynamic pulmonary function test computerized Spirometer Eazy on-PC model were used. Dynamic PFT parameter FEF25%-75%was used as measure of lung function. Results: In our Study conducted, middle aged obese females had FEF25%-75% (litre) of 2.53± 0.85 compared to corresponding values in controls were 2.77±1.06.Our study showed statistically significant differences between two groups. Conclusion: In our study Dynamic pulmonary function test parameter FEF25%-75% showed statistically significant reduction in obese compared to non-obese middle aged females. Keywords: Obesity, Middle aged obese

Lrp1 Regulation of Pulmonary Function. Follow-Up of Human GWAS in Mice.

Human genome-wide association studies (GWASs) have identified more than 270 loci associated with pulmonary function; however, follow-up studies to determine causal genes at these loci are few. SNPs in low-density lipoprotein receptor-related protein 1 (LRP1) are associated with human pulmonary function in GWASs. Using murine models, we investigated the effect of genetic disruption of the Lrp1 gene in smooth muscle cells on pulmonary function in naive animals and after exposure to bacterial LPS or house dust mite extract. Disruption of Lrp1 in smooth muscle cells leads to an increase in tissue resistance, elastance, and tissue elastance at baseline. Furthermore, disruption of Lrp1 in smooth muscle increases airway responsiveness as measured by increased total lung resistance and airway resistance after methacholine. Immune cell counts in BAL fluid were increased in animals with Lrp1 disruption. The difference in airway responsiveness by genotype observed in naive animals was not observed after LPS or house dust mite extract exposure. To further explore the mechanisms contributing to changes in pulmonary function, we identified several ligands dysregulated with Lrp1 disruption in smooth muscle cells. These data suggest that dysregulation of LRP1 in smooth muscle cells affects baseline pulmonary function and airway responsiveness and helps establish LRP1 as the causal gene at this GWAS locus.

Bronchial thermoplasty reduces ventilation heterogeneity measured by multiple breath nitrogen washout

BackgroundDespite demonstrated symptomatic benefit from bronchial thermoplasty (BT), the underlying pathophysiological benefits have been uncertain. The purpose of the present study was to relate clinical benefit after BT to changes in lung physiology, focusing on ventilation homogeneity assessed using multiple breath nitrogen washout (MBNW), and how this may be affected by changes in airway volume and resistance.MethodsConsecutive patients (n = 21) with severe asthma scheduled for BT, were evaluated at baseline, 6 weeks and 6 months after completion of treatment. Assessments included the Asthma Control Questionnaire (ACQ), medication usage, exacerbation frequency, spirometry, plethysmography and MBNW. Eighteen of these patients underwent detailed CT evaluation for the estimation of airway volume at baseline and then after the left lung had received BT treatment but prior to right lung treatment. Data are mean ± STDEV.ResultsPatients responded to BT with an improvement in ACQ from 3.4 ± 0.8 at baseline to 2.0 ± 1.1 at 6 months (p < 0.001). Steroid requiring exacerbations fell from 3.1 ± 2.9 in the 6 months prior to BT to 1.4 ± 1.7 following BT (p < 0.001). Significant reductions in maintenance oral steroid dosing and short acting beta agonist use were observed.Airway volume measured by CT scanning significantly increased after treatment. The FEV1 improved from 1.34 ± 0.65 l to 1.52 ± 0.76 l (p = 0.024). The Residual Volume fell from 2.87 ± 0.89 l to 2.71 ± 0.93 l (p = 0.008) and Total Airway Resistance (Raw) from 10.58 ± 6.56 to 7.64 ± 3.74 cmH2O.s.l−1 (p = 0.020). The Lung Clearance Index (LCI) was 187 ± 63% predicted at baseline and improved after treatment from 12.7 ± 3.3 to 11.8 ± 2.4 (p = 0.049). The improvement in LCI correlated with the improvement in Raw (r = 0.463, p = 0.035).ConclusionClinical benefit after BT is accompanied by improvements in lung physiology, including normalisation of lung homogeneity that seems to be driven by airway dilation and reduced resistance.

PM2.5 induces autophagy-mediated cell apoptosis via PI3K/AKT/mTOR signaling pathway in mice bronchial epithelium cells.

Air pollution can highly impact the respiratory system in healthy individuals. Studies have indicated that particles with an aerodynamic diameter of ≤2.5 µm (PM2.5) can be considered to be harmful for lung alveoli and bronchial epithelium cells. PM2.5 can be directly inhaled and can deeply penetrate into the lung alveoli, causing lung dysfunction. However, the toxicological mechanism mediated by PM2.5 for respiratory disease has still not been clearly determined. The purpose of the current study was to investigate the effects of PM2.5 on mouse bronchial epithelium cells (MBECs) and explored the possible mechanism mediated by PM2.5 in MBECs. The results of the current study indicated that PM2.5 markedly decreased lung function, including total lung capacity, residual volume, vital capacity and airway resistance in experimental mice. The results demonstrated that PM2.5 markedly induced inflammatory responses, oxidative injury and MBEC apoptosis. PM2.5 increased interleukin (IL)-1β and IL-6 expression, and reactive oxygen species production in MBECs. Furthermore, PM2.5 specifically induced PI3K, AKT and mTOR expression in MBECs. Disruption of PI3K/AKT/mTOR signaling was also indicated to effectively inhibit apoptosis of MBECs. In conclusion, the results of the current study systematically demonstrated the role of apoptosis-mediated MBEC apoptosis in PM2.5-treated mice, and provides a potential strategy for preclinical intervention in patients with PM2.5-induced lung diseases.

Total nasal airway resistance while sitting predicts airway collapse when lying down.

Nasal obstruction when lying down is a common complaint in patients with chronic nasal obstruction, but rhinomanometry is typically performed in the sitting position. This study aimed to analyse whether adding rhinomanometry in a supine position is a useful examination. A total of 41 patients with chronic nasal obstruction underwent rhinomanometry and acoustic rhinometry, sitting and supine, before and after decongestion, as well as an over-night polygraphy. Total airway resistance was measurable in a supine position in 48 per cent (14 of 29) of the patients with total airway resistance of equal to or less than 0.3 Pa/cm3/second when sitting and in none (0 of 12) of the patients with total nasal airway resistance of more than 0.3 Pa/cm3/second when sitting. After decongestion, this increased to 83 per cent and 58 per cent, respectively. Increased nasal resistance when sitting predicts nasal breathing problems when supine. Rhinomanometry in a supine position should be performed to diagnose upper airway collapse when supine.

Airway mechanics after withdrawal of a leukotriene receptor antagonist in children with mild persistent asthma: Double-blind, randomized, cross-over study.

To determine the response of airway mechanics and the changes in asthma symptoms to stepping down of leukotriene receptor antagonist (LTRA) therapy. Thirty children (mean age: 7.1 years) with mild, well-controlled, and persistent asthma who took LTRA as maintenance treatment were randomized into a double-blind, placebo-controlled, cross-over study. Each group received an LTRA (montelukast) or placebo daily for 2 weeks, followed by a 1-week washout period, and then the alternate treatment for 2 weeks. Spirometry and impulse oscillation system (IOS) measurements before and after four puffs of salbutamol inhalation, fractional exhaled nitric oxide (FeNO), and the childhood asthma control test (C-ACT) were evaluated at baseline, the end of placebo treatment, and the end of LTRA treatment. Changes of FEV1 /FVC (p = .113) and FEV1 (p = .109) from baseline to posttreatment did not differ significantly between the placebo and montelukast groups. In the placebo group, prebronchodilator (pre-) FEV1 /FVC was decreased (83% vs. 86%) and bronchodilator response (BDR) in FEV1 was diminished (10.7% vs. 6.4%) at posttreatment compared with baseline. However, the montelukast group had no significant changes in pre-FEV1 /FVC (p = .865) and BDR in FEV1 (p = .461). In addition, compared with the montelukast group, the placebo group showed no significant changes in Rrs5 (total airway resistance), Rrs5-20 (peripheral airway resistance), FeNO, and symptoms by the C-ACT. In children with well-controlled mild persistent asthma, changes in spirometry, IOS, FeNO, and C-ACT results did not differ between the placebo and montelukast groups within 2 weeks.

Deterioration of Nighttime Respiratory Mechanics in COPD: Impact of Bronchodilator Therapy

COPD is associated with nighttime respiratory symptoms, poor sleep quality, and increased risk of nocturnal death. Overnight deterioration of inspiratory capacity (IC) and FEV1 have been documented previously. However, the precise nature of this deterioration and mechanisms by which evening bronchodilation may mitigate this occurrence have not been studied. What is the effect of evening dosing of dual, long-acting bronchodilation on detailed nocturnal respiratory mechanics and inspiratory neural drive (IND)? A double-blind, randomized, placebo-controlled crossover study assessed the effects of evening long-acting bronchodilation (aclidinium bromide/formoterol fumarate dihydrate: 400/12 μg) or placebo on morning trough IC (12h after the dose; primary outcome) and serial overnight measurements of spirometry, dynamic respiratory mechanics, and IND (secondary outcomes). Twenty participants with COPD (moderate/severe airway obstruction and lung hyperinflation) underwent serial measurements of IC, spirometry, breathing pattern, esophageal and transdiaphragmatic pressures, and diaphragm electromyography (diaphragmatic electromyography as a percentage of maximum; IND) at 6 time points from 0 to 12h after the dose and compared with sleeping IND. Compared with placebo, evening bronchodilation was not associated with increased morning trough IC 12h after the dose (P= .48); however, nadir IC (lowest IC, independent of time), peak IC, area under the curve for 12h after the dose, and IC for 10h after the dose were improved (P< .05). During placebo, total airways resistance, lung hyperinflation, IND, and tidal esophageal and transdiaphragmatic pressure swings all increased significantly overnight compared with baseline evening values; however, each of these parameters improved with bronchodilator treatment (P< .05) with no change in ventilation or breathing pattern. Respiratory mechanics significantly deteriorated at night during placebo. Although the morning trough IC was unchanged, evening bronchodilator treatment was associated consistently with sustained overnight improvements in dynamic respiratory mechanics and inspiratory neural drive compared with placebo CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT02429765.

Diagnosis of asthma in children: findings from the Swiss Paediatric Airway Cohort.

Diagnosing asthma in children remains a challenge because respiratory symptoms are not specific and vary over time. In a real-life observational study, we assessed the diagnostic accuracy of respiratory symptoms, objective tests and two paediatric diagnostic algorithms (proposed by the Global Initiative for Asthma (GINA) and the National Institute for Health and Care Excellence (NICE)) in the diagnosis of asthma in school-aged children. We studied children aged 5-17 years who were referred consecutively to pulmonary outpatient clinics for evaluation of suspected asthma. Symptoms were assessed by parental questionnaire. The investigations included specific IgE measurement or skin prick tests, measurement of exhaled nitric oxide fraction (F eNO), spirometry, body plethysmography and bronchodilator reversibility (BDR). Asthma was diagnosed by paediatric pulmonologists based on all available data. We assessed diagnostic accuracy of symptoms, tests and diagnostic algorithms by calculating sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and area under the curve (AUC). Among 514 participants, 357 (70%) were diagnosed with asthma. The combined sensitivity and specificity was highest for any wheeze (sensitivity=75%, specificity=65%), dyspnoea (sensitivity=56%, specificity=76%) and wheeze triggered by colds (sensitivity=58%, specificity=78%) or by exercise (sensitivity=55%, specificity=74%). Of the diagnostic tests, the AUC was highest for specific total airway resistance (sRtot; AUC=0.73) and lowest for the residual volume (RV)/total lung capacity (TLC) ratio (AUC=0.56). The NICE algorithm had sensitivity=69% and specificity=67%, whereas the GINA algorithm had sensitivity=42% and specificity=90%. This study confirms the limited usefulness of single tests and existing algorithms for the diagnosis of asthma. It highlights the need for new and more appropriate evidence-based guidance.

Association Between Bedroom Particulate Matter Filtration and Changes in Airway Pathophysiology in Children With Asthma

Fine particles (particulate matter 2.5 μm [PM2.5]), a ubiquitous air pollutant, can deposit in the small airways that play a vital role in asthma. It appears to be unknown whether the use of a PM2.5 filtration device can improve small airway physiology and respiratory inflammation in children with asthma. To discover what pathophysiological changes in the small airways are associated with using a PM2.5-removing device in the bedrooms of children with asthma. Children with mild or moderate asthma were enrolled in this double-blind, crossover study. The participants used a true filtration device and a sham filtration device in their bedrooms in a random order for 2 weeks each with a 2-week washout interval. The study was conducted in a suburb of Shanghai, China, during a low-ozone season. Ozone and PM2.5 were measured inside bedrooms and outside a window. Impulse oscillometry, spirometry, and fractional exhaled nitric oxide were measured at the beginning and the end of each intervention. Peak expiratory flow was measured twice daily at home. Forty-three children (5-13 years old; 26 boys [60%]) participated. Outdoor 24-hour mean PM2.5 concentrations were moderately high, ranging from 28.6 to 69.8 μg/m3 (median, 53 μg/m3). During true filtration, bedroom PM2.5 concentrations were a mean (SD) of 63.4% (35.9%) lower than during sham filtration. Compared with sham filtration, true filtration was significantly associated with improved airway mechanics, reflected in a 24.4% (95% CI, 11.8%-37.1%) reduction in total airway resistance, a 43.5% (95% CI, 13.7%-73.3%) reduction in small airway resistance, a 22.2% (95% CI, 2.2%-42.2%) reduction in resonant frequency, and a 73.1% (95% CI, 0.3%-145.8%) increase in airway reactance. True filtration was also associated with significant improvements in fractional exhaled nitric oxide (a 27.6% [95% CI, 8.9%-42.4%] reduction) and peak expiratory flow (a 1.6% [95% CI, 0.8%-2.5%] increase). These improvements were significantly associated with bedroom PM2.5 reduction. Improvements in small airway function were nonsignificant (8.4% [95% CI, -1.4% to 18.3%]) in all participants but significant (13.2% [95% CI, 1.2%-25.1%]) in participants without eosinophilic airway inflammation at baseline. No improvements were observed for forced vital capacity, forced expiratory volume during the first second, and the ratio of these in all participants or subgroups. Per these results, indoor PM2.5 filtration can be a practical method to improve air flow in an asthmatic lung through improved airway mechanics and function as well as reduced inflammation. This warrants a clinical trial to confirm. ClinicalTrials.gov Identifier: NCT03282864.

Bronchial thermoplasty reduces airway resistance

BackgroundThe mechanism for symptomatic improvement after bronchial thermoplasty (BT) is unclear, since spirometry reveals little or no change. In this study, the effects of BT on airway resistance were examined using two independent techniques.MethodsEighteen consecutive patients, with severe asthma (57.6 ± 14.2 years) were evaluated by spirometry and plethysmography at three time points: (i) baseline, (ii) left lung treated but right lung untreated and (iii) 6 weeks after both lungs were treated with BT. At each assessment, total and specific airway resistance (Raw, sRaw) were measured. High resolution CT scans were undertaken at the first two assessments, and measurements of lobar volume, airway volume and airway resistance were made. The Asthma Control Questionnaire (ACQ) was administered at each assessment.ResultsThe baseline ACQ score was 3.5 ± 0.9, and improved progressively to 1.8 ± 1.2 (p < 0.01). At baseline, severe airflow obstruction was observed, FEV1 44.8 ± 13.7% predicted, together with gas trapping, and elevated Raw at 342 ± 173%predicted. Following BT, significant improvements in Raw and sRaw were observed, as well as a reduction in Residual Volume, increase in Vital Capacity and no change in FEV1. The change in Raw correlated with the change in ACQ (r = 0.56, p < 0.05).CT scans demonstrated reduced airway volume at baseline, which correlated with the increased Raw determined by plethysmography (p = − 0.536, p = < 0.05). Following BT, the airway volume increased in the treated lung, and this was accompanied by a significant reduction in CT-determined local airway resistance.ConclusionSymptomatic improvement after BT is mediated by increased airway volume and reduced airway resistance.

Associations of personal exposure to air pollutants with airway mechanics in children with asthma

BackgroundThe importance of airway mechanics has been increasingly recognized in pediatric asthma. However, no studies have examined responses of airway mechanics to air pollution exposure in asthmatic children. MethodsIn this panel study involving indoor air filtration manipulation that created a large gradient of personal exposure to PM2.5, the airway mechanics and lung function of 43 asthmatic children 5–13 years old in a suburb of Shanghai were measured four times within 3 consecutive months. Concentrations of indoor and outdoor PM2.5 and ozone were coupled with individual time-activity data to calculate personal exposures. Linear mixed effects models were used to examine the relationships of personal exposure with indicators of airway mechanics and lung function, respectively. ResultsAn interquartile range (IQR) increase in 24-hour average PM2.5 personal exposure (30.3 µg/m3) in the prior day was associated with significant increases in small airway resistance (R5-R20) of 15.8%, total airway resistance (R5) of 6.3%, and airway inflammation (FeNO) of 9.6%. These associations were stronger in children with lower blood eosinophil counts (<450/µL). No significant associations were found between personal PM2.5 exposure and lung function. Low-level ozone exposure (daily maximum 8-hour exposure range 1.1–56.4 ppb) was not significantly associated with any of the outcomes. ConclusionChanges in personal PM2.5 exposure, partly enhanced by air filtration, were associated with significant changes in airway resistance and inflammation in children with asthma. These findings suggest the importance of reducing PM2.5 exposure, via personal air quality management, in improving airflow limitation in the airways, especially the small airways.

THERAPEUTIC BLOWING TOYS: DOES THE OVERLAP OF VENTILATORY STIMULI ALTER THE RESPIRATORY MECHANICS OF HEALTHY SCHOOLCHILDREN?

ABSTRACTObjective: To verify whether the overlapping of ventilatory stimuli, resulting from playing with blowing toys, changes the respiratory mechanics of healthy schoolchildren.Methods: Cross-sectional study with healthy schoolchildren aged seven to 14 years old from Florianópolis, Santa Catarina, Southern Brazil. Spirometric data were obtained, a health questionnaire and the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire were also applied. The procedure consisted of playing with the following blow toys in a random order: soap bubbles, party whistles and balloon. Before and after the intervention, the assessment of respiratory mechanics was carried out by impulse oscillometry - IOS (Erich Jaeger, Germany®). The ANOVA for repeated measures test was applied.Results: 71 students of both genders with mean age of 9.7±2.1 years participated in the study. Results showed a progressive decrease of impedance (Z5), total airway resistance (R5) and resonance frequency (Fres) when the moment before the use of the first toy was compared with the moment after the third toy (Z5/p=0.048; R5/p=0.049; Fres/p=0.004). Fres also differed between the moment before the first and the second toy (p=0.048). After the use of each of the three blowing toys, the oscillometric parameters did not differ.Conclusions: The difference in oscillometric parameters of R5 before the use of each toy indicates that the overlap of ventilatory stimuli produced by them provided a reduction in the R5.

Dynamic hyperinflation and intrinsic positive end-expiratory pressure in ARDS patients

BackgroundIn ARDS patients, changes in respiratory mechanical properties and ventilatory settings can cause incomplete lung deflation at end-expiration. Both can promote dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEP). The aim of this study was to investigate, in a large population of ARDS patients, the presence of intrinsic PEEP, possible associated factors (patients’ characteristics and ventilator settings), and the effects of two different external PEEP levels on the intrinsic PEEP.MethodsWe made a secondary analysis of published data. Patients were ventilated with a tidal volume of 6–8 mL/kg of predicted body weight, sedated, and paralyzed. After a recruitment maneuver, a PEEP trial was run at 5 and 15 cmH2O, and partitioned mechanics measurements were collected after 20 min of stabilization. Lung computed tomography scans were taken at 5 and 45 cmH2O. Patients were classified into two groups according to whether or not they had intrinsic PEEP at the end of an expiratory pause.ResultsWe enrolled 217 sedated, paralyzed patients: 87 (40%) had intrinsic PEEP with a median of 1.1 [1.0–2.3] cmH2O at 5 cmH2O of PEEP. The intrinsic PEEP significantly decreased with higher PEEP (1.1 [1.0–2.3] vs 0.6 [0.0–1.0] cmH2O; p < 0.001). The applied tidal volume was significantly lower (480 [430–540] vs 520 [445–600] mL at 5 cmH2O of PEEP; 480 [430–540] vs 510 [430–590] mL at 15 cmH2O) in patients with intrinsic PEEP, while the respiratory rate was significantly higher (18 [15–20] vs 15 [13–19] bpm at 5 cmH2O of PEEP; 18 [15–20] vs 15 [13–19] bpm at 15 cmH2O). At both PEEP levels, the total airway resistance and compliance of the respiratory system were not different in patients with and without intrinsic PEEP. The total lung gas volume and lung recruitability were also not different between patients with and without intrinsic PEEP (respectively 961 [701–1535] vs 973 [659–1433] mL and 15 [0–32] % vs 22 [0–36] %).ConclusionsIn sedated, paralyzed ARDS patients without a known obstructive disease, the amount of intrinsic PEEP during lung-protective ventilation is negligible and does not influence respiratory mechanical properties.

Impulse Oscillometry to Evaluate Lung Function in Young Children Under Five Years with Sickle Cell Disease

BACKGROUND Young children with sickle cell disease (SCD) aged 2 - 5 years old are at the highest risk of acute chest syndrome (ACS), a leading cause of morbidity and mortality. In addition to severe forms of SCD (HbSS and HbSβ0 thalassemia), asthma and airway hyper-responsiveness are also known risk factors for ACS, and are three to five times more prevalent in older children and adults with SCD. However in SCD children under 5 years there are only a few studies describing airway function, due to limitations in spirometry and other common pulmonary function tests (PFTs). Impulse oscillometry, a passive, non-invasive technique to evaluate airway function via pulmonary resistance and reactance, has been validated in children as young as 3 years, but has not been used widely in children with SCD. OBJECTIVE We sought to describe baseline airway function in children under 5 years with SCD using impulse oscillometry, as part of an ongoing observational study to evaluate lung function in young SCD children over time. METHOD Following IRB approval, participation in the ongoing prospective study was offered to patients aged 3 - 5 years old with HbSS and HbSβ0 thalassemia followed at the Pediatric Sickle Cell Clinic at Augusta University. Parents of the consented patients completed a modified ISAAC questionnaire assessing reported asthma symptoms and tobacco smoke exposure. Baseline IOS was obtained within 6 months of consent, with other clinical data obtained from medical records. Airway function was assessed using airway resistance at 5Hz and 20Hz (R5, R20), and reactance at 5Hz (X5). Percent predicted values were computed using NHANES (National Health and Nutrition Examination Survey) reference criteria for age, height, gender and ethnicity. RESULTS Out of 9 consented patients, 7 completed the ISAAC questionnaire and 6 successfully performed IOS. One patient consented but deferred participation to next visit and 1 patient with HbSC was excluded from analysis. All remaining patients had sickle cell anemia (HbSS). Age range at study enrolment was 3.7 - 5.4 years (mean 4.6 years). All participants were African American, 4/7 were male. Four out of 7 survey participants were already on Hydroxyurea therapy for their disease with therapy duration ranging from 2 - 41 months. None had preceding history of ACS. One survey respondent reported asthma symptoms (wheezing, dry cough at night) in preceding 12 months and 1 reported passive tobacco exposure. None reported a prior asthma diagnosis. Of the 6 participants with PFT data, baseline percent-predicted values for IOS parameters R5 and R20 were 114.83 ± 22.37 and 97.83 ± 23.11 respectively. Baseline X5 (%pred) was 76.33 ± 48.59. DISCUSSION Our preliminary results show normal baseline airway function in this subset of young SCA patients, with R5 representing total airway resistance, and R20 representing resistance in large airways. Small airway function can be deduced from differences between R5 and R20. Airway resistance decreases with age, and early changes in small airway resistance can be seen in children with asthma and obstructive symptoms. Low frequency reactance serves as a measure of airway distensibility, especially in the distal airways. Therefore, conditions affecting lung elasticity would result in abnormal X5. Ongoing data collection and follow-up will help us study how airway function evolves in young children with SCA with or without underlying asthma. We will also assess the effects of Hydroxyurea and other disease-modifying therapies on airway function over time. Disclosures No relevant conflicts of interest to declare.