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Biomedical subjects

S Vedal

Publications and source records attributed to S Vedal.

At least 19 recordsLinked to original sources
PubMed2005

Interpretation of transbronchial lung biopsies from lung transplant recipients: inter- and intraobserver agreement.

BACKGROUND: Transbronchial lung biopsy results are crucial for the management of lung transplant recipients. Little information is available regarding the reliability and reproducibility of the interpretation of transbronchial lung biopsies. OBJECTIVE: To examine the inter-reader variability between two lung pathologists with expertise in lung transplantation. METHODS: Fifty-nine transbronchial lung biopsy specimens were randomly selected. Active infection had been excluded in all cases. The original interpretations (as per the Lung Rejection Study Group) for acute rejection grade included 19 biopsies scored as A0 (none), 14 scored as A1 (minimal), 12 as A2 (mild), 11 as A3 (moderate) and three as A4 (severe). The pathologists worked independently without clinical information or knowledge of the original interpretation. The specimens were graded using the Lung Rejection Study Group criteria for acute rejection (grades A0 to A4), airway inflammation (grades B0 to B4) and bronchiolitis obliterans (C0 absent and C1 present). Between-reader agreement for each category was analyzed using a Kappa statistic. RESULTS: Because many transplant specialists initiate augmented immunosuppression with biopsy grades of A2 or higher, results for each reader were dichotomized as A0/A1 versus A2/A3/A4. Using this dichotomy, there was only moderate agreement (kappa 0.470, P < 0.001) between readers. For categories B and C, the results were dichotomized for the absence or presence of airway inflammation and bronchiolitis obliterans, respectively. The level of agreement between readers was fair for category B (kappa 0.333, P = 0.014) and poor for category C (kappa 0.166, P = 0.108). The intrareader agreement for acute rejection was substantial (kappa 0.795, P = 0.0001; kappa 0.676, P = 0.0001). CONCLUSIONS: Because the agreement between expert pathologists is only modest, optimum clinical decision-making requires that transbronchial lung biopsy results be used in an integrated clinical context.

Biopsy↗
PubMed2004

Wood smoke exposure and lung adenocarcinoma in non-smoking Mexican women.

OBJECTIVE: To determine the association between long-term exposure to wood smoke from cooking and lung adenocarcinoma in non-smoking Mexican women. METHODS: We reviewed records of hospitalized patients at a chest referral hospital in Mexico City and identified 113 histologically proven lung adenocarcinoma cases in non-smoking women. Four control groups of non-smoking women were also selected: 99 patients with pulmonary tuberculosis (PTB), 110 with interstitial lung disease (ILD), 64 with miscellaneous pulmonary conditions (MISC), and the three control groups combined (COMB) (n = 273). RESULTS: Exposure was assessed on the basis of questionnaire responses at the time of hospital admission. Exposure to wood smoke for more than 50 years, but not for shorter periods, was associated with lung cancer after adjusting for age, education, socio-economic status and environmental tobacco smoke (ETS) exposure. Adjusted odds ratios from the multivariable logistic regression models were 1.4 (95%CI 0.6-2.0) for cases vs. TB controls, 1.9 (95%CI 0.9-4.0) for cases vs. ILD controls, 2.6 (95%CI 1.0-6.3) for cases vs. MISC controls and 1.9 (95%CI 1.1-3.5) for cases vs. COMB controls. CONCLUSION: These findings suggest that long-term exposure to wood smoke from cooking may contribute to the development of lung cancer.

Adenocarcinoma↗
PubMed2002

Exposure misclassification and threshold concentrations in time series analyses of air pollution health effects.

Linear, no-threshold relationships are typically reported for time series studies of air pollution and mortality. Since regulatory standards and economic valuations typically assume some threshold level, we evaluated the fundamental question of the impact of exposure misclassification on the persistence of underlying personal-level thresholds when personal data are aggregated to the population level in the assessment of exposure-response relationships. As an example, we measured personal exposures to two particle metrics, PM2.5 and sulfate (SO4(2-)), for a sample of lung disease patients and compared these with exposures estimated from ambient measurements Previous work has shown that ambient:personal correlations for PM2.5 are much lower than for SO4(2-), suggesting that ambient PM2.5 measurements misclassify exposures to PM2.5. We then developed a method by which the measured:estimated exposure relationships for these patients were used to simulate personal exposures for a larger population and then to estimate individual-level mortality risks under different threshold assumptions. These individual risks were combined to obtain the population risk of death, thereby exhibiting the prominence (and the value) of the threshold in the relationship between risk and estimated exposure. Our results indicated that for poorly classified exposures (PM2.5 in this example) population-level thresholds were apparent at lower ambient concentrations than specified common personal thresholds, while for well-classified exposures (e.g., SO4(2-)), the apparent thresholds were similar to these underlying personal thresholds. These results demonstrate that surrogate metrics that are not highly correlated with personal exposures obscure the presence of thresholds in epidemiological studies of larger populations, while exposure indicators that are highly correlated with personal exposures can accurately reflect underlying personal thresholds.

Air Pollution↗
PubMed2001

Air pollution and retained particles in the lung.

Epidemiologic evidence associates particulate air pollution with cardiopulmonary morbidity and mortality. The biological mechanisms underlying these associations and the relationship between ambient levels and retained particles in the lung remain uncertain. We examined the parenchymal particle content of 11 autopsy lungs from never-smoking female residents of Mexico City, a region with high ambient particle levels [3-year mean PM(10) (particulate matter < or = 10 microm in aerodynamic diameter)= 66 microg/m(3)], and 11 control residents of Vancouver, British Columbia, Canada, a region with relatively low levels (3-year mean PM(10) = 14 microg/m(3). Autopsy lungs were dissolved in bleach and particles were identified and counted by analytical electron microscopy. Total particle concentrations in the Mexico City lungs were significantly higher [geometric mean = 2,055 (geometric SD = 3.9) x 10(6) particles/g dry lung vs. 279 (1.8) x 10(6) particles/g dry lung] than in lungs from Vancouver residents. Lungs from Mexico City contained numerous chain-aggregated masses of ultrafine carbonaceous spheres, some of which contained sulfur, and aggregates of ultrafine aluminum silicate. These aggregates made up an average of 25% of the total particles by count in the lungs from Mexico City, but were only rarely seen in lungs from Vancouver. These observations indicate for the first time that residence in a region with high levels of ambient particles results in pulmonary retention of large quantities of fine and ultrafine particle aggregates, some of which appear to be combustion products.

Aged↗
PubMed2000

Exposure of chronic obstructive pulmonary disease patients to particulate matter: relationships between personal and ambient air concentrations.

Mot time-series studies of particulate air pollution and acute health outcomes assess exposure of the study population using fixed-site outdoor measurements. To address the issue of exposure misclassification, we evaluate the relationship between ambient particle concentrations and personal exposures of a population expected to be at risk of particle health effects. Sampling was conducted within the Vancouver metropolitan area during April-September 1998. Sixteen subjects (non-smoking, ages 54-86) with physician-diagnosed chronic obstructive pulmonary disease (COPD) wore personal PM2.5 monitors for seven 24-hr periods, randomly spaced approximately 1.5 weeks apart. Time-activity logs and dwelling characteristics data were also obtained for each subject. Daily 24-hr ambient PM10 and PM2.5 concentrations were measured at five fixed sites spaced throughout the study region. SO4(2-), which is found almost exclusively in the fine particle fraction and which does not have major indoor sources, was measured in all PM2.5 samples as an indicator of accumulation mode particulate matter of ambient origin. The mean personal and ambient PM2.5 concentrations were 18 micrograms/m3 and 11 micrograms/m3, respectively. In analyses relating personal and ambient measurements, ambient concentrations were expressed either as an average of the values obtained from five ambient monitoring sites for each day of personal sampling, or as the concentration obtained at the ambient site closest to each subject's home. The mean personal to ambient concentration ratio of all samples was 1.75 (range = 0.24 to 10.60) for PM2.5, and 0.75 (range = 0.09 to 1.42) for SO4(2-). Regression analyses were conducted for each subject separately and on pooled data. The median correlation (Pearson's r) between personal and average ambient PM2.5 concentrations was 0.48 (range = -0.68 to 0.83). Using SO4(2-) as the exposure metric, the median r between personal and average ambient concentrations was 0.96 (range = 0.66 to 1.0). Use of the closest ambient site did not improve the median correlation of the group for either PM2.5 or SO4(2-). All pooled analyses resulted in lower correlation coefficients than the median correlation coefficient of individual regressions. Personal SO4(2-) was more highly correlated with all ambient measures than PM2.5. Inclusion of time-activity and dwelling characteristics data did not result in a useful predictive regression model for PM2.5 personal exposure, but improved the model fit from simply regressing against ambient concentration (R2 = 0.27). The model for SO4(2-) was predictive (R2 = 0.82), as personal exposures were largely explained by ambient levels. These results indicate a relatively low correlation between personal exposure and ambient PM2.5 that is not improved by assigning exposure to the closest ambient monitor. The correlation between personal exposure and ambient concentration is high, however, when using SO4(2-), an indicator of accumulation mode particulate matter of ambient origin.

Aged↗
PubMed1999

The significance of the persistent presence of acid-fast bacilli in sputum smears in pulmonary tuberculosis.

STUDY OBJECTIVES: Identification of acid-fast bacilli (AFB) in the sputum smear at the completion of tuberculosis therapy is in some settings considered evidence of treatment failure. However, some patients with pulmonary tuberculosis (TB) will have positive smear results with negative sputum culture results at the end of therapy. The objectives of this study were to estimate the prevalence of persisting positive sputum smear results in patients with TB and to identify characteristics that distinguish patients with persistently positive sputum smear results who also had negative sputum culture results from patients identified as treatment failures. DESIGN: A population-based, historical cohort study with nested case control study. SETTING: British Columbia Division of Tuberculosis Control central case registry. PATIENTS: All 428 patients with culture-proven pulmonary TB in British Columbia over 7 years with sputum that was positive for AFB. METHODS: Review of laboratory data of all 428 patients, as well as clinical data of a subset of 30 patients with persistently positive smear results beyond 20 weeks. RESULTS: Sputum smears were positive for AFB in 205 patients (48%) at 4 weeks, in 30 patients (7%) at 20 weeks, and in 12 patients (3%) at 36 weeks. Of the patients with smear results that were persistently positive at 20 weeks, 23 (77%) had negative sputum culture results and 7 (23%) had positive sputum culture results (ie, they were treatment failures). Patients identified as treatment failures had more localized disease as shown on chest radiographs, had less radiographic improvement at follow-up, had a higher prevalence of drug resistance, and were less compliant with medications than patients with persistently positive smear results and negative culture results. No subject with a negative culture result relapsed over the 6- to 48-month observation period. CONCLUSION: Sputum that is persistently positive for AFB in patients in developed countries is more likely to be associated with negative culture results than with treatment failure.

Adult↗
PubMed1999

Community study using a polymerase chain reaction panel to determine the prevalence of common respiratory viruses in asthmatic and nonasthmatic children.

We developed a sensitive polymerase chain reaction (PCR) panel, suitable for the detection of seven common respiratory viruses, to study the prevalence of viruses in nasal swabs obtained from clinically stable asthmatic children (n = 21), non-physician diagnosed asthmatic children with exercise-induced bronchoconstriction (EIB) (n = 16), and nonasthmatic, non-EIB controls (n = 33). The PCR panel detected viruses in 43/70 (61.4%) specimens but there were no significant differences in prevalence of these viruses between the three groups of children. These results indicate that clinically stable asthmatic and nonasthmatic children frequently harbor viruses in the upper respiratory tract.

Adenoviruses, Human↗
PubMed1998

Long term cigarette smoke exposure does not increase airway responsiveness in rats.

To ascertain whether chronic cigarette smoke exposure induces increased airway responsiveness, we performed methacholine response tests in Sprague-Dawley rats by calculating pulmonary resistance after nebulization of saline followed by an increasing concentration of methacholine. We also calculated the concentration of methacholine which doubled the baseline resistance (R200). Tests were performed at baseline and after 2, 4, 8, and 12 months of exposure to the smoke of seven cigarettes per day, 5 days each week; control animals were exposed to room air. At the completion of the study, there were 13 rats in the smoke-exposed group and 7 rats remaining in the control group. Airway morphology was assessed using a point counting technique. We found that (1) chronic exposure to cigarette smoke did not alter either the baseline resistance or the R200; (2) the saline baseline resistance decreased over time in the control animals; and (3) at the 12-month time point, smokers with increased baseline airway resistance had greater amounts of airway smooth muscle compared with the smoke-exposed animals without increased resistance. We conclude that in this animal model, long term exposure to cigarette smoke did not alter the response to methacholine but did increase airway smooth muscle and baseline resistance in some but not all animals.

Airway Resistance↗
PubMed1998

Acute effects of ambient inhalable particles in asthmatic and nonasthmatic children.

Although increases in inhalable particle (PM10) concentrations have been associated with acute reductions in the level of lung function and increased symptom reporting in children, including children with asthma, it is not clear whether these effects occur largely in asthmatic children, or even whether asthmatic children are more likely to experience these effects than children without asthma. To address these points, the following subgroups of children were selected from a survey population of all 2,200 elementary school children (6 to 13 yr of age) in a pulp mill community on the west coast of Vancouver Island: (1) all children with physician-diagnosed asthma (n = 75 participated), (2) all children with an exercise-induced fall in FEV1 without diagnosed asthma (n = 57), (3) all children with airway obstruction (FEV1/FVC < 0.76) without either of the above (n = 18), and (4) control children without any of the above (n = 56). The children were followed for as long as 18 mo with twice daily measurements of peak expiratory flow (PEF) and daily symptom diary recording. Maximum daily PM10 concentration was 159 microm/m3 (median, 22.1), but only 8 d (1.2%) had concentrations above 100 microg/m3. In an analysis that accounted for time-varying covariates, and serially correlated and missing data, for the entire sample of children, increases in PM10 were associated with reductions in PEF and increased reporting of cough, phlegm production, and sore throat. For the subgroup of children with diagnosed asthma, PEF in the time period with the highest PM10 concentrations fell by an estimated 0.55 L/min (95% CI, 0.06 to 1.05) for a 10 microg/m3 PM10 increase above the mean daily PM10 concentration of 27.3 microg/m3 and the odds of reported cough increased by 8% (95% CI, 0 to 16%); no consistent effects were observed in the other groups of children. It is concluded that children experience reductions in PEF and increased symptoms after increases in relatively low ambient PM10 concentrations, and that children with diagnosed asthma are more susceptible to these effects than are other children.

Adolescent↗
PubMed1998

Risk factors for near-fatal asthma. A case-control study in hospitalized patients with asthma.

We prospectively recruited patients admitted to the hospital with severe asthma to comprehensively evaluate the association of historical and physiologic features with the risk of near-fatal asthma (NFA). A case-control study design was used. All patients admitted with NFA (cases) were identified prospectively and compared with asthma patients admitted during the same period without respiratory failure (controls). Nineteen cases (age: 40.2 +/- 12.0 yr) (mean +/- SD) and 80 controls (age: 36 +/- 13.5 yr) were enrolled. Duration of asthma, gender, smoking status, ethnicity, and prevalence of atopy were similar in the case and control groups. More than 80% of patients in both groups reported worsening symptoms for more than 48 h before admission, and more than 50% were worse for longer than 7 d. There was no difference in degree of airways obstruction or bronchial hyperresponsiveness (PC20). Perception of dyspnea was similar in the cases and controls, but among cases the males had greater impairment than the females (Borg score: 1.9 +/- 1. 4 versus 3.9 +/- 1.2: p = 0.05). Univariate analysis identified a history of previous mechanical ventilation (OR: 27.5; 95% CI: 6.60 to 113.7), admission to the intensive care unit (ICU) (OR: 9.9; 95% CI: 3.0 to 32.9), history of worse asthma during January and February (OR: 3.5; 95% CI: 1.0 to 11.8), and use of air-conditioning (OR: 15.0; 95% CI: 1.3 to 166) as risk factors for NFA. Of concern was the dependence of most patients (59.8%) on the emergency department (ED) for initial care, and the small number of cases (16%) in which patients visited a physician before admission to the hospital. We have confirmed risk factors identified previously in retrospective studies of fatal and NFA, and have also shown that hospitalized patients with asthma, irrespective of severity of their asthma, share several characteristics, especially in terms of their failure to respond to worsening asthma.

Acute Disease↗
PubMed1997

A longitudinal analysis of pulmonary function in rats during a 12 month cigarette smoke exposure.

We wanted to examine the longitudinal effects of chronic cigarette smoke exposure, and to determine whether the chronic alterations in pulmonary function induced by long-term cigarette smoke exposure in an animal model could be predicted by initial or early alterations in function. A group of Sprague Dawley rats was exposed to the smoke of 7 cigarettes x day(-1) for 5 days x week(-1) during a total period of 12 months. Lung volume, flow-volume curves and pressure-volume curves were recorded at baseline, and after 2, 4, 8 and 12 months of smoke exposure. A control group of rats was subjected to the same regimen of testing, but was not exposed to smoke. Thirteen rats completed the study in the smoke-exposed group and seven rats in the control group. We found that chronic exposure to cigarette smoke produced early abnormalities in pulmonary function, with the forced expiratory volume in one second/forced vital capacity (FEV1/FVC) ratio showing an acceleration of ageing effect, particularly between 4 and 8 months of exposure. In this model, although the two groups had significantly different airflow after 12 months, the initial values in each group were remarkably similar, and we could not identify any pulmonary function test which had predictive value. We conclude that longitudinal studies of cigarette smoke exposure in this rat model allow better characterization of the nature and time course of the effects of smoking on the lung.

Animals↗
PubMed1996

Carinal and tubular airway particle concentrations in the large airways of non-smokers in the general population: evidence for high particle concentration at airway carinas.

OBJECTIVE: To evaluate the extent to which human airway carinas accumulate ambient atmospheric particles, a newly developed technique was used to micro-dissect and analyse particle concentration in tubular segments and carinas of the large airways of 10 necropsy lungs from non-smokers from the general population of Vancouver. METHODS: Ratios of the particle concentrations on the carinas to the tubular segment immediately preceding it were measured with analytical electron microscopy for the mainstem bronchus, upper and lower lobe bronchi, and four different segmental or subsegmental bronchi--that is, Weibel generations 1 to about 5. A total of 119 carinal-tubular pairs was evaluated. RESULTS: Over all cases, both carinal and tubular particle concentrations increased with increasing airway generation; the median ratio of carinal to tubular particle concentration was 9:1 and did not show any trend with airway generation. The ratio was > 5 in 71% of carinal-tubular pairs, > 10 in 42% of pairs, > 20 in 31% of pairs, and > 100 in 9% of pairs. Some subjects showed a notable tendency to high ratios, with many ratios > 100, and other subjects had a tendency toward low ratios. The predominant mineral species in both carinas and tubular airway segments was crystalline silica and the relative proportion was similar in both sites; however, mean particle diameter was consistently less in the carinal tissues. CONCLUSIONS: These findings suggest that the ratio of carinal to tubular retained particles in the large airways in non-smokers is higher than might be supposed from data generated in airway casts, and that there is considerable variation in this ratio between subjects. This finding is of potential interest in models of carcinogen, toxin, and dose of fibrogenic agent to the large airways as it suggests high and sometimes extreme concentrations of toxic particles at carinas, and thus reinforces the notion that carinas may be sites of initiation of disease.

Aged↗
PubMed1996

Shape and position of the complete dose-response curve for inhaled methacholine in normal subjects.

Plateaus on the inhalation concentration-response curve have been described in normal subjects and patients with mild asthma. To determine the prevalence of plateaus on inhalation concentration-response curves, and the position of the curves in normal subjects, we measured complete dose-response curves for methacholine (1 mg/ml to 256 mg/ml) in 73 nonatopic, nonsmoking, nonasthmatic normal subjects between the ages of 20 and 76 yr. Measurements included FEV1, maximal expiratory flow at 50% and 30% of vital capacity on partial and complete forced expiratory flow-volume curves (Vmax50p, Vmax50c, Vmax30p, Vmax30c) and pulmonary resistance (RL). Plateau responses, EC50 values and slopes were measured. Plateaus were present in 25, 27, 24, 34, 35, and 16 subjects for FEV1, Vmax50c, Vmax30c, Vmax50p, Vmax30p, and RL, respectively. In those who achieved a plateau, the mean maximal decrease in FEV1 (+/- SD) was 21 +/- 8%, in Vmax50c it was 46 +/- 16%, in Vmax50p it was 67 +/- 12%, in Vmax30c it was 58 +/- 21%, and in Vmax30p it was 75 +/- 15%, and the increase in RL was 213 +/- 89%. In summary, the results of this study showed that easily identifiable plateaus develop on the inhalation concentration-response curves of approximately 40% of normal subjects after only moderate decreases in maximum flow and increases in RL. Maximal response at the plateau was greater on partial flow-volume curves and at lower lung volumes (30% versus 50% of VC). Comparison of these data with data from patients at risk for airway hyperresponsiveness will allow definition of the mechanisms leading to airway hyperresponsiveness.

Administration, Inhalation↗
PubMed1996

Exposure to biomass smoke and chronic airway disease in Mexican women. A case-control study.

A case-control study was performed in women older than 40 yr of age to evaluate the risk of cooking with traditional wood stoves for chronic bronchitis and chronic airway obstruction (CAO). The subjects were recruited from patients attending a referral chest hospital in Mexico City. We selected 127 patients with chronic bronchitis or CAO, of which 63 had chronic bronchitis alone, 23 had CAO alone (FEV1 less than 75% of predicted), and 41 had both chronic bronchitis and CAO (cases). Four control groups were selected: 83 patients with pulmonary tuberculosis, 100 patients with interstitial lung diseases, 97 patients with ear, nose and throat ailments, and 95 healthy visitors to the hospital (controls). Exposure to wood smoke, assessed as any or none, and as hour-years (years of exposure multiplied by average hours of exposure per day) was significantly higher in cases than in controls. Crude odds ratios for wood smoke exposure were 3.9 (95% CI, 2.0 to 7.6) for chronic bronchitis only, 9.7 (95% CI, 3.7 to 27) for CAO plus chronic bronchitis, and 1.8 (95% CI, 0.7 to 4.7) for CAO only. Differences in exposure to wood smoke persisted after adjusting by stratification and logistic regression for age, income, education, smoking, place of residence, and place of birth. Risk of chronic bronchitis alone and chronic bronchitis with CAO increased linearly with hour-years of cooking with a wood stove; odds ratios for exposure to more than 200 hour-years compared with nonexposed were 15.0 (95% CI, 5.6 to 40) for chronic bronchitis only and 75 (95% CI, 18 to 306) for chronic bronchitis with CAO. The findings support a causal role of domestic wood smoke exposure in chronic bronchitis and chronic airflow obstruction.

Adult↗
PubMed1996

Effect of ambient ozone exposure on lung function in farm workers.

Effects of ozone exposure on outdoor farm workers in the Fraser Valley of British Columbia, Canada, were investigated. Fifty-eight workers underwent spirometry daily before and after each 8- to 14-h workday from June 23 to August 26, 1993. The mean daily maximum (1 h) ambient ozone concentration was 40 ppb (range: 13 to 84 ppb). Concentrations of acid aerosols and fine particulates, potential confounders of ozone effects, were very low. In individual regressions of evening FEV1 and FVC on maximum daily ozone concentration, 47 of 53 workers with valid data (46 of 53 for FVC) had negative slopes. The average slopes (weighted by the inverse SE of the regression coefficients) were -3.3 and -4.7 ml for FEV1 and FVC, respectively, for each ppb increase in ozone (p < 0.001). Following correction for an individual's mean lung function level, date, and temperature, regression of either the afternoon or the daily change (afternoon-morning) corrected for the morning measurement of FEV1 and FVC on ozone showed similar magnitudes of effect. These associations were still apparent on the following morning, suggesting a persistent ozone effect. These results indicate that exposure of a population of outdoor workers to ambient ozone concentrations below 85 ppb is associated with decreased lung function over the day, which persists to the following day.

Adult↗
PubMed1995

Determinants of airway smooth muscle shortening in excised canine lobes.

There is marked heterogeneity of airway narrowing in intraparenchymal airways in response to bronchoconstricting stimuli. We hypothesized that this heterogeneity results from variations in the structure of the airway wall. Freshly excised dog lung lobes were inflated to transpulmonary pressures (PL) of between 5 and 15 cmH2O, and an aerosol containing a high concentration of carbachol was administered. The lobes were fixed and processed for light-microscopic examination and morphometric analysis of membranous airway dimensions. The relationships of smooth muscle shortening to PL and airway dimensions were analyzed using multiple linear regression. The results show that airway smooth muscle shortening was greater at lower PL and in airways with larger internal perimeter and a greater number of folds per internal perimeter and that it was less in airways with greater inner wall area. We conclude that the magnitude and variability of airway smooth muscle shortening and airway narrowing in response to maximal constricting stimuli are influenced by mechanical factors related to airway wall geometry.

Airway Resistance↗