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Respiratory Research Mar 2020The 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...
BACKGROUND
The 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.
METHODS
Eighteen 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.
RESULTS
The 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.
CONCLUSION
Symptomatic improvement after BT is mediated by increased airway volume and reduced airway resistance.
Topics: Adult; Aged; Airway Resistance; Asthma; Bronchial Thermoplasty; Female; Humans; Male; Middle Aged; Plethysmography; Respiratory Function Tests
PubMed: 32228586
DOI: 10.1186/s12931-020-1330-5 -
Respiratory Medicine Jun 2018Impulse oscillometry (IOS) is the most commonly used type of forced oscillation technique in clinical practice, although relatively little is known about its application... (Review)
Review
Impulse oscillometry (IOS) is the most commonly used type of forced oscillation technique in clinical practice, although relatively little is known about its application in COPD. Resistance at 20 Hz (R20) is unrelated to COPD severity and does not improve with bronchodilatation or bronchoconstriction, inferring a lack of large airway involvement in COPD. Peripheral airway resistance expressed as frequency dependent heterogeneity between 5 Hz and 20 Hz (R5-R20), and peripheral airway compliance as area under the reactance curve (AX), are both closely related to COPD severity and exacerbations. Both R5-R20 and AX markedly improve in response to long acting bronchodilators, while AX appears to be more sensitive than R5-R20 in response to bronchoconstriction. Future studies may be directed to assess if IOS in combination with spirometry is more sensitive at predicting future exacerbations. Perhaps AX might also be useful as a screening tool in early stage disease or to monitor long term decline in COPD.
Topics: Airway Resistance; Female; Humans; Male; Oscillometry; Pulmonary Disease, Chronic Obstructive; Respiratory Function Tests; Severity of Illness Index
PubMed: 29857993
DOI: 10.1016/j.rmed.2018.05.004 -
Respiratory Physiology & Neurobiology Nov 2021Cystic fibrosis (CF) is characterized by small airway disease; but central airways may also be affected. We hypothesized that airway resistance estimated from...
Cystic fibrosis (CF) is characterized by small airway disease; but central airways may also be affected. We hypothesized that airway resistance estimated from computational fluid dynamic (CFD) methodology in infants with CF was higher than controls and that early airway inflammation in infants with CF is associated with airway resistance. Central airway models with a median of 51 bronchial outlets per model (interquartile range 46,56) were created from chest computed tomography scans of 18 infants with CF and 7 controls. Steady state airflow into the trachea was simulated to estimate central airway resistance in each model. Airway resistance was increased in the full airway models of infants with CF versus controls and in models trimmed to 33 bronchi. Airway resistance was associated with markers of inflammation in bronchoalveolar lavage fluid obtained approximately 8 months earlier but not with markers obtained at the same time. In conclusion, airway resistance estimated by CFD modeling is increased in infants with CF compared to controls and may be related to early airway inflammation.
Topics: Airway Resistance; Computer Simulation; Cystic Fibrosis; Humans; Hydrodynamics; Infant; Models, Biological; Pneumonia; Tomography, X-Ray Computed
PubMed: 34157384
DOI: 10.1016/j.resp.2021.103722 -
Experimental Physiology Apr 2020What is the central question of this study? Are sex difference in the central airways present in healthy paediatric patients? What is the main finding and its...
NEW FINDINGS
What is the central question of this study? Are sex difference in the central airways present in healthy paediatric patients? What is the main finding and its importance? In patients ≤12 years we found no sex differences in central airway luminal area. After 14 years, the males had significantly larger central airway luminal areas than the females. The sex differences were minimized, but preserved when correcting for height. Luminal area is the main determinant of airway resistance and our finding could help explain sex differences in pulmonary system limitations to exercise in paediatric patients.
ABSTRACT
Cross-sectional airway area is the main determinant of resistance to airflow in the respiratory system. In paediatric patients (<18 years), previous evidence for sex differences in cross-sectional airway area was limited to patients with history of pulmonary disease or cadaveric studies with small numbers of subjects. These studies either only report tracheal data and do not include a range of ages or correct for height. Therefore, we sought to assess sex differences in airway luminal area utilizing paediatric patients of varying ages and no history of respiratory disease. Using three-dimensional reconstructions from high-resolution computed tomography scans, we retrospectively assessed the cross-sectional airway area in healthy paediatric females (n = 97) and males (n = 128) over a range of ages (1-17 years). The areas of the trachea, left main bronchus, left upper lobe, left lower lobe, right main bronchus, intermediate bronchus and right upper lobe were measured at three discrete points by a blinded investigator. No differences between the sexes were noted in the cross-sectional areas of the youngest (ages 1-12 years) patients (P > 0.05). However, in patients ≥14 years the cross-sectional areas were larger in the males compared to females in most airway sites. For instance, the cross-sectional size of the trachea was 25% (218 ± 44 vs. 163 ± 24 mm , P < 0.01) larger in males vs. females among ages 13-17 years. When accounting for height, these sex differences in airway areas were attenuated, but persisted. Our results indicate that sex differences in paediatric airway cross-sectional area manifest after age ≥14 years and are independent of height.
Topics: Airway Resistance; Bronchi; Child; Child, Preschool; Female; Humans; Inhalation; Lung; Male; Retrospective Studies; Sex Characteristics; Tomography, X-Ray Computed; Trachea
PubMed: 32003484
DOI: 10.1113/EP088370 -
American Journal of Respiratory and... Feb 2017For unclear reasons, obese children with asthma have higher morbidity and reduced response to inhaled corticosteroids.
RATIONALE
For unclear reasons, obese children with asthma have higher morbidity and reduced response to inhaled corticosteroids.
OBJECTIVES
To assess whether childhood obesity is associated with airway dysanapsis (an incongruence between the growth of the lungs and the airways) and whether dysanapsis is associated with asthma morbidity.
METHODS
We examined the relationship between obesity and dysanapsis in six cohorts of children with and without asthma, as well as the relationship between dysanapsis and clinical outcomes in children with asthma. Adjusted odds ratios (ORs) were calculated for each cohort and in a combined analysis of all cohorts; longitudinal analyses were also performed for cohorts with available data. Hazard ratios (HRs) for clinical outcomes were calculated for children with asthma in the Childhood Asthma Management Program.
MEASUREMENTS AND MAIN RESULTS
Being overweight or obese was associated with dysanapsis in both the cross-sectional (OR, 1.95; 95% confidence interval [CI], 1.62-2.35 [for overweight/obese compared with normal weight children]) and the longitudinal (OR, 4.31; 95% CI, 2.99-6.22 [for children who were overweight/obese at all visits compared with normal weight children]) analyses. Dysanapsis was associated with greater lung volumes (FVC, vital capacity, and total lung capacity) and lesser flows (FEV and forced expiratory flow, midexpiratory phase), and with indicators of ventilation inhomogeneity and anisotropic lung and airway growth. Among overweight/obese children with asthma, dysanapsis was associated with severe disease exacerbations (HR, 1.95; 95% CI, 1.38-2.75) and use of systemic steroids (HR, 3.22; 95% CI, 2.02-5.14).
CONCLUSIONS
Obesity is associated with airway dysanapsis in children. Dysanapsis is associated with increased morbidity among obese children with asthma and may partly explain their reduced response to inhaled corticosteroids.
Topics: Administration, Inhalation; Adolescent; Adrenal Cortex Hormones; Airway Resistance; Anti-Asthmatic Agents; Asthma; Case-Control Studies; Child; Comorbidity; Drug Resistance; Female; Forced Expiratory Flow Rates; Humans; Longitudinal Studies; Male; Multicenter Studies as Topic; Obesity; Proportional Hazards Models; Vital Capacity; Young Adult
PubMed: 27552676
DOI: 10.1164/rccm.201605-1039OC -
American Journal of Physiology. Lung... Jun 2022Lung resistance () is determined by airway and parenchymal tissue resistance, as well as the degree of heterogeneity in airway constriction. Deep inspirations (DIs) are...
Lung resistance () is determined by airway and parenchymal tissue resistance, as well as the degree of heterogeneity in airway constriction. Deep inspirations (DIs) are known to reverse experimentally induced increase in , but the mechanism is not entirely clear. The first step toward understanding the effect of DI is to determine how each of the resistance components is affected by DI. In the present study, we measured and apparent airway resistance (, which combines the effects of airway resistance and airway heterogeneity) simultaneously before and after a DI in acetylcholine (ACh)-challenged ex vivo sheep lungs. We found that at normal breathing frequency (0.25 Hz) ACh-challenge led to a doubling of , 80.3% of that increase was caused by an increase in ; the increase in apparent tissue resistance () was insignificant. 57.7% of the increase in was abolished by a single DI. After subtracting from , the remaining was mostly independent of ACh-challenge and its reduction after a DI came mostly from the change in the mechanical properties of lung parenchyma. We conclude that at normal breathing frequency, in an unchallenged lung is mostly composed of , and the increase in due to ACh-challenge stems mostly from the increase in and that both and can be greatly reduced by a DI, likely due to a reduction in true airway resistance and heterogeneity, as well as parenchymal tissue hysteresis post DI.
Topics: Airway Resistance; Animals; Inhalation; Lung; Parenchymal Tissue; Respiratory Function Tests; Sheep
PubMed: 35537098
DOI: 10.1152/ajplung.00033.2022 -
The Journal of the Acoustical Society... Jun 2021Steady airflow resistances in semi-occluded airways as well as acoustic impedances in vocalization are quantified from the lungs to the lips. For clinical and voice...
Steady airflow resistances in semi-occluded airways as well as acoustic impedances in vocalization are quantified from the lungs to the lips. For clinical and voice training applications, the primary focus is on two airway conditions, an oral semi-occlusion and a semi-occlusion above the vocal folds. Laryngeal airflow resistance is divided into glottal airflow resistance and epilaryngeal airway resistance. Maximum aerodynamic power is transferred to the vocal tract if the glottal airflow resistance is reduced while the epilaryngeal airway resistance is increased. A semi-occlusion at the lips helps to set up this condition. For the acoustic power transfer, the epilaryngeal airway also serves to match the impedance of the source to the impedance of the vocal tract.
Topics: Humans; Larynx; Phonation; Vocal Cords; Voice; Voice Training
PubMed: 34241487
DOI: 10.1121/10.0005124 -
Sleep Science (Sao Paulo, Brazil) 2015To evaluate the available literature regarding Upper Airway Resistance Syndrome (UARS) treatment. (Review)
Review
OBJECTIVE
To evaluate the available literature regarding Upper Airway Resistance Syndrome (UARS) treatment.
METHODS
Keywords "Upper Airway Resistance Syndrome," "Sleep-related Breathing Disorder treatment," "Obstructive Sleep Apnea treatment" and "flow limitation and sleep" were used in main databases.
RESULTS
We found 27 articles describing UARS treatment. Nasal continuous positive airway pressure (CPAP) has been the mainstay therapy prescribed but with limited effectiveness. Studies about surgical treatments had methodological limitations. Oral appliances seem to be effective but their efficacy is not yet established.
CONCLUSION
Randomized controlled trials with larger numbers of patients and long-term follow-up are important to establish UARS treatment options.
PubMed: 26483942
DOI: 10.1016/j.slsci.2015.03.001 -
Respiratory Care Mar 2021A 20% reduction in the FEV is routinely used as an end point for methacholine challenge testing (MCT). Measurement of FEV is effort dependent, and some patients are not...
BACKGROUND
A 20% reduction in the FEV is routinely used as an end point for methacholine challenge testing (MCT). Measurement of FEV is effort dependent, and some patients are not able to perform acceptable and repeatable forced expiration maneuvers. The goal of the present study was to investigate the diagnostic value of airway resistance measurement by forced oscillation technique (FOT), body plethysmography, and interrupter technique compared with the traditionally accepted standard FEV measurement in evaluating the responsiveness to methacholine during MCT.
METHODS
We included in the study adult subjects referred for MCT because of asthma-like symptoms and with normal baseline spirometry. We modified routine MCT protocol by adding the assessment of airway resistance to the measurement of FEV at each step of MCT.
RESULTS
We observed, in the subjects with airway hyper-responsiveness versus those with normal airway responsiveness, a significantly greater percentage change in median (interquartile range) FOT resistance at 10 Hz (25.9% [13.7%-35.4%] vs 16% [15.7%-27.2%]), plethysmographic resistance (70.2% [39.5%-116.3%] vs 37.1% [23.9%-81.9%]), and mean ± SD conductance (-41.3 ± 15.4% vs -29.6 ± 15.9%); and a significantly greater change in mean ± SD FOT reactance at 10 Hz (-0.41 ± 0.48 cm HO/L/s vs -0.09 ± 0.32 cm HO/L/s) and at 15 Hz (-0.29 ± 0.2 cm HO/L/s vs -0.1 ± 0.19 cm HO/L/s). We also recorded significant differences in airway resistance parameters (FOT resistance at 10 Hz, FOT reactance at 15 Hz, plethysmographic airway resistance, and conductance indices as well as interrupter resistance) in FEV non-responders at the onset of respiratory symptoms during MCT compared with baseline.
CONCLUSIONS
Measurements of airway resistance could possibly be used as an alternative method to spirometry in airway challenge. Significant changes in airway mechanics during MCT are detectable by airway resistance measurement in FEV non-responders with methacholine-induced asthma-like symptoms. (ClinicalTrials.gov registration NCT02343419.).
Topics: Adult; Airway Resistance; Bronchial Provocation Tests; Forced Expiratory Volume; Humans; Methacholine Chloride; Spirometry
PubMed: 33203723
DOI: 10.4187/respcare.08331 -
Journal of Applied Physiology... Aug 2021Obesity alters chest wall mechanics, reduces lung volumes, and increases airway resistance. In addition, the luminal area of the larger conducting airways is smaller in...
Obesity alters chest wall mechanics, reduces lung volumes, and increases airway resistance. In addition, the luminal area of the larger conducting airways is smaller in women than in men when matched for lung size. We examined whether differences in pulmonary mechanics with obesity and sex were associated with the dysanapsis ratio (DR), an estimate of airway size when the expiratory flow is maximal, in men and women with and without obesity. In addition, we examined the ability to estimate DR using predicted versus measured static recoil pressure at 50% forced vital capacity (FVC; Pst). Participants completed pulmonary function testing and measurements of pulmonary mechanics. Flow, volume, and transpulmonary pressure were recorded while completing forced vital capacity (FVC) maneuvers in a body plethysmograph. Static compliance curves were collected using the occlusion technique. DR was calculated using measured values of forced midexpiratory flow and Pst. DR was also calculated using Pst predicted from previously reported data. There was no significant group (lean vs. obese) by sex interaction or main effect of group on DR. However, women displayed significantly larger DR compared with men. Predicted Pst was significantly greater than measured Pst. DR calculated from measured Pst was significantly greater than when using predicted Pst. In conclusion, although obesity does not appear to alter airway size, women may have larger airways compared with men when midexpiratory flow is maximal. In addition, DR estimated using predicted Pst should be used with caution. It is unclear whether obesity in combination with sex influences the dysanapsis ratio (DR). These data indicate that DR is unaltered in adults with obesity and is greater in women than in men but similar between sexes when matched for lung volume. We also report a significant difference between predicted and measured static recoil pressure. Thus, we caution against predicting static recoil pressure in the calculation of DR.
Topics: Adult; Airway Resistance; Female; Forced Expiratory Volume; Humans; Lung; Lung Volume Measurements; Male; Obesity; Vital Capacity
PubMed: 34166096
DOI: 10.1152/japplphysiol.00133.2021