Measurement Of Airway Resistance Research Articles

Respiratory consequences of obesity and diabetes

While sustained hyperglicemia affects the smooth muscle tone and the elastin-collagen network, the effect of diabetes mellitus on the function and structure of the airways and the lung parenchyma has not been characterized, and the confounding influence of obesity has not been elucidated. To reveal the separate and additive roles of diabetes mellitus and obesity on the respiratory function. Non-obese mechanically ventilated patients were categorized as control non-diabetic (n = 80) and diabetic (n = 35) groups. Obese patients with (n = 33) or without (n = 47) associated diabetes were also enrolled. Forced oscillation technique was applied to measure airway resistance (Raw), tissue damping (G), and tissue elastance (H). Capnography was utilized to determine phase 3 slopes and ventilation dead space parameters. Arterial and central venous blood samples were analyzed to assess intrapulmonary shunt fraction (Qs/Qt) and the lung oxygenation index (PaO2/FiO2). Diabetes without obesity increased the Raw (7.4 ± 5 cmH2O.s/l vs. 3.0 ± 1.7 cmH2O.s/l), G (11.3 ± 4.9 cmH2O/l vs. 6.2 ± 2.4 cmH2O/l), and H (32.3 ± 12.0 cmH2O/l vs. 25.1 ± 6.9 cmH2O/l, (p<0.001 for all), compared with the corresponding control groups. Capnographic phase 3 slope was increased in diabetes without significant changes in PaO2/FiO2 or Qs/Qt. While similar detrimental changes in respiratory mechanics and alveolar heterogeneity were observed in obese patients without diabetes, these alterations also compromised gas exchange. The intrinsic mechanical abnormalities in the airways and lung tissue induced by diabetes are counterbalanced by hypoxic pulmonary vasoconstriction, thereby maintaining intrapulmonary shunt fraction and oxygenation ability of the lungs. Orv Hetil. 2022; 163(2): 63-73.

Chapter 1 - Pulmonary function testing in neuromuscular disease

Neuromuscular disorders frequently compromize pulmonary function and effective ventilation, and a thorough respiratory evaluation often can assist in diagnosis, risk assessment, and prognostication. Since many of these disorders can be progressive, serial assessments may be necessary to best define a trajectory of impairment or improvement with therapy. Patients with neuromuscular diseases may have few respiratory symptoms and limited signs of skeletal muscle weakness, but can have significant respiratory muscle weakness. A single testing modality may fail to elucidate true respiratory compromise, and often a combination of tests is recommended to fully evaluate these patients. Common tests performed in this population include measurement of flow rates, lung volumes, maximal pressures, and airways resistance. This review covers the major respiratory testing modalities available in the evaluation of these patients, emphasizing both the benefits and shortcomings of each approach. The majority of parameters are available in a standard pulmonary laboratory (flows, volumes, static pressures), although referral to a specialized center may be necessary to conclusively evaluate a given patient.

Impulse Oscillometry Parameters in Childhood Asthma, Childhood Obesity and Childhood Obesity with Asthma

Background: Monitoring of lung function is necessary to detect irreversible airway obstruction in both asthma and obesity. Impulse oscillometry (IOS), a novo non-invasive equipment, is increasing popularity to measure airway resistance in young children worldwide. Aims: To compare IOS parameters among Thai asthmatic children and Thai obese children with and without asthma. Methods: A cross-sectional study was conducted in 120 participants, aged 4-15 years old. Forty children were in each group (asthma, obesity, and obesity with asthma). All volunteers were consented to measure airway resistance by IOS technique (Jaeger, Germany). Results: Seventy-three percent of patients were male with the mean age at 8.8 + 2.61 years old. Mean X5 was found normal in childhood obesity (-0.13) when compared to children with asthma (-0.23) and obesity with asthma (-0.19) (p &lt; 0.001 and 0.013 respectively). The cut-off value of X5, according to ROC curve, for predicting asthma in obese patients was -0.16 kPa/L/s with 70% sensitivity, 70% specificity and 70% accuracy (AUC= 0.69). However, with the bronchodilator effect (adjusted by duration of asthma control), we found significant higher percentage change of IOS parameters, including resonant frequency, area of reactance and R5-R20, in asthma (Fres -24.57 + 15.82, AX -58.28 + 13.37, R5-R20 -51.32 + 20.13) than in asthma with obesity (Fres -13.77 + 16.42, AX -43.35 + 21.4, R5-R20 -34.72 + 18.21), (p = 0.014, 0.004, 0.002 respectively). Conclusions: X5 and percentage changes after bronchodilator of Fres, AX, and R5-R20 are useful parameters to differentiate airway dysfunction in asthmatic children from obese children.

Reliability of translaryngeal airway resistance measurements during maximal exercise.

ObjectiveExercise-induced laryngeal obstruction is an important cause of exertional dyspnoea. The diagnosis rests on visual judgement of relative changes of the laryngeal inlet during continuous laryngoscopy exercise (CLE) tests, but we lack objective measures that reflect functional consequences. We aimed to investigate repeatability and normal values of translaryngeal airway resistance measured at maximal intensity exercise.Methods31 healthy nonsmokers without exercise-related breathing problems were recruited. Participants performed two CLE tests with verified positioning of two pressure sensors, one at the tip of the epiglottis (supraglottic) and one by the fifth tracheal ring (subglottic). Airway pressure and flow data were continuously collected breath-by-breath and used to calculate translaryngeal resistance at peak exercise. Laryngeal obstruction was assessed according to a standardised CLE score system.ResultsData from 26 participants (16 females) with two successful tests and equal CLE scores on both test sessions were included in the translaryngeal resistance repeatability analyses. The coefficient of repeatability (CR) was 0.62 cmH2O·L−1·s−1, corresponding to a CR% of 21%. Mean±sd translaryngeal airway resistance (cmH2O·L−1·s−1) in participants with no laryngeal obstruction (n=15) was 2.88±0.50 in females and 2.18±0.50 in males. Higher CLE scores correlated with higher translaryngeal resistance in females (r=0.81, p<0.001).ConclusionsThis study establishes translaryngeal airway resistance obtained during exercise as a reliable parameter in respiratory medicine, opening the door for more informed treatment decisions and future research on the role of the larynx in health and disease.

Relationships among pulmonary function, anxiety and depression in mild asthma: An exploratory study

In a secondary analysis of data from a prior study, we calculated the relationships among depression (PHQ-8), anxiety (GAD-7), and measures of asthma in 69 steroid-naïve patients with mild and moderate symptomatic asthma. Average levels of pulmonary function, depression and anxiety tended to be in the normal range, and asthma tended to be well controlled (Asthma Control Test). Nevertheless, PHQ-8 scores were significantly correlated with forced oscillation (FO) measures of airway reactance (AX) and resistance at a low frequency of stimulation (Rrs5 Hz). GAD-7 scores also were significantly related to Rrs5 Hz. Exploratory analyses in Supplementary data provide no evidence for vagal mediation of the association. Further research is necessary to discover mechanisms for the associations found here. Future studies might examine the utility of assessing and treating mild anxiety and depression in mild to moderate asthma.

Specific Immunotherapy in a Murine Model of Grass Pollen (Phl p5b)-Induced Airway Inflammation.

Background: The use of ovalbumin as a model allergen in murine models of allergic asthma is controversially discussed since it is not an aeroallergen and sensitization can only be achieved by using strong Th2-inducing adjuvants. Therefore, in this study, a murine model of asthma has been established in which sensitization against the major grass pollen allergen Phl p5b was performed without using aluminum hydroxide (alum). We used this model for specific immunotherapy.Methods: Female, 5–6-week-old mice were sensitized by six subcutaneous (s.c.) injections of 20 μg Phl p5b followed by four provocations to induce allergic airway inflammation. For desensitization, 1 mg of Phl p5b was injected subcutaneously during allergen challenge for one to a maximum of four times. Three days after the last challenge, the allergic immune response was analyzed.Results: Sensitized and challenged animals showed a significant infiltration of eosinophils into the airways, and the production of interleukin-5 (IL-5) by in vitro re-stimulated splenocytes could be detected. Furthermore, hyper-responsiveness of the airways was verified by invasive measurement of airway resistance in methacholine-challenged animals. Desensitized animals showed a significant reduction of all parameters.Conclusion: In this study, a murine model of asthma has successfully been established by sensitization against the clinically relevant allergen Phl p5b without using alum. S.c. injection of allergen dose dependently led to desensitization of sensitized mice. We suggest that this model is useful to study adjuvant effects of immune modulatory substances on immunotherapy without the interference of alum.

Lung Function and Health Status in Individuals with Severe Alpha-1-Antitrypsin Deficiency at the Age of 42.

BackgroundSevere hereditary alpha-1-antitrypsin deficiency (AATD) is a known risk factor for the early development of pulmonary emphysema and COPD, especially in smokers. By the Swedish national screening programme carried out from 1972 to 1974, a cohort of individuals with severe (PiZZ) AATD was identified and has been followed up regularly. The aim of this study was to investigate health status, quality of life and lung function in this cohort at the age of 42 years compared with an age-matched control group randomly selected from the population registry.MethodsAll study participants answered a questionnaire on smoking habits, symptoms, occupation, exposure to airway irritants and quality of life using Saint George’s Respiratory Questionnaire (SGRQ). They underwent complete pulmonary function tests (PFT) and forced oscillation technique (FOT) for the measurement of airway resistance and reactance. Blood samples were taken for allergies and IgG-subclasses as an indicator of increased risk of airway infections.ResultsThe residual volume (RV), total lung capacity (TLC) and RV/TLC ratio were significantly higher in the PiZZ ever-smokers compared to the PiMM ever-smokers and PiZZ never-smokers (p < 0.05). The resistance in the upper, small and total airways was significantly lower in PiZZ subjects compared to PiMM subjects (p < 0.05). A greater proportion of PiZZ never-smokers had an FEV1/VC ratio <0.7 than PiMM never-smokers (p = 0.043). PiZZ subjects with occupational exposure to airway irritants showed a significantly lower FEV1, VC and higher RV/TLC ratio than PiMM individuals with exposure (p < 0.05).ConclusionAt the age of 42, ever-smoking PiZZ individuals have signs of COPD, and also PiZZ never-smokers have early, physiological signs of emphysema.

Predictors of methacholine challenge testing results in subjects without airflow obstruction

Objective Methacholine challenge testing (MCT) is considered when asthma remains clinically suspected despite normal spirometry. Few studies have attempted to determine the predictive factors of MCT results. We aimed to establish which demographic data, clinical symptoms, pulmonary function testing results, and laboratory values were associated with abnormal MCT (provocation concentration causing a 20% decrease in FEV1 (PC20) ≤ 16 mg/mL) in subjects without airflow obstruction on spirometry. Methods All patients who completed MCT at Montfort Hospital between January 1st, 2016 and December 31st, 2018 were identified. Subjects with a reduced FEV1/FVC ratio were excluded. We used Pearson’s chi-squared test and point-biserial correlation method to determine which variables had a significant relationship (p < 0.05) with MCT results. Results 23.3% of patients who underwent MCT had airflow limitation. In the 1126 subjects with a normal FEV1/FVC ratio, PC20 ≤ 16 mg/mL was found in 13.0%. Younger age, female gender, body mass index ≥ 40, and reported wheezing were factors associated with increased probability of airway hyper responsiveness. Lower FEV1, significant improvement of the FEV1 post-bronchodilator, reduced FEF25%-75%, greater FEF25%-75% reversibility, airway resistance measurements above the upper limit of normal, and increased blood eosinophil counts were predictive of abnormal MCT. Conclusions Only 13.0% of patients referred for MCT had a PC20 ≤ 16 mg/mL when the FEV1/FVC ratio was normal, highlighting the need to further define in which individuals this test is truly warranted. Further investigation is required to develop an easy-to-use and validated prediction model in order to better understand patients’ pretest probability of abnormal MCT.

Prenatal metal mixtures and early childhood lung function

BACKGROUND AND AIM: Individual metal exposures have been linked to child lung health, however associations with prenatal metal mixtures has not been described. We employed a novel statistical approach to examine associations between prenatal exposure to 18 metals and child lung function. METHODS: Analyses included 135 mothers and children enrolled in the longitudinal PRogramming of Intergenerational Stress Mechanisms (PRISM) pregnancy cohort. Urinary metals were analyzed in prenatal maternal spot urine with inductively coupled plasma-mass spectrometer-triple quadrupole. Children performed impulse oscillometry (IOS) at age 4 years; IOS z-scores adjusted for age, sex, race/ethnicity and height and weight. We employed Bayesian Weighted Quantile Sum (BWQS) regression to examine associations between prenatal metal mixture exposure and IOS z-scores, adjusting for gestational age at spot urine collection, urinary creatinine, maternal education and gestational age at delivery. Sex-specific effects were explored. RESULTS:Sixty three percent (N=84) and 36% (N=48) of children self-reported Black and Hispanic ethnicity, respectively. Children were aged a median 4.2 years (IQR 3.7, 4.9) at the time of IOS and 52% (N=70) were male. In adjusted models, prenatal metal mixtures were associated with increased R5 (R5 z-score β= 0.26, 95% credible interval, CI, 0.01, 0.49) and R20 (R20 z-score, β= 0.29, 95% CI 0.00, 0.57), measures of total and large airway resistance, respectively. BWQS metal mixture weights identified that for both R5 and R20, Nickel, Lead, Barium, and Antimony had the largest proportional weights; Cadmium and Copper had larger weights for R5 while tin and manganese had lerger weights for R20. Girls were more vulnerable to the effects of metal mixtures on R5 while boys were more vulnerable to effects on R20. CONCLUSIONS:Prenatal metal mixture exposures were associated with impaired airway mechanics at age four years, with a suggestion of a sex-differential response. KEYWORDS: Prenatal, metal mixtures, lung function

Original Article: Clinical Research.

Aim:In this study, we aimed to investigate the possible role of endotrophin, a profibrotic byproduct of collagen VI, in the complex process of fibrosis development in the disease group with pulmonary fibrosis among interstitial lung diseases.Material and Method:When the patients’ participation in the study were completed, smoking or alcohol drinking conditions, and family history were recorded. Their weights and heights were recorded and body mass index (BMI) was calculated. In every patient, Spirometry with bronchodilator testing, determination of single-breath DLCO, and plethysmographic measurement of thoracic gas volume and airway resistance were performed. Blood samples were obtained for the inflammation markers such as sedimentation rate, C-reactive protein (CRP), complete blood count, liver and renal function tests, and lactate dehydrogenase levels. Serum endotrophin levels were measured in all patients.Results:Thirty-five patients with interstitial lung disease who were having pulmonary fibrosis, 35 patients with interstitial lung disease without pulmonary fibrosis, and 20 control patients without any signs or symptoms of interstitial lung disease were included in the study. Age distribution was similar between groups. The fibrotic ILD group was more commonly smoker or ex-smoker compared with the non-fibrotic ILD patients or control cases. Fibrotic ILD patients were leaner, having significantly decreased total lung capacity, diffusion capacity, and higher LDH levels. In the comparison of the 3 study groups regarding the endotrophin levels, there was a significant difference between groups. The fibrotic and non-fibrotic patient groups were compared for the Endotrophin levels and the difference was also significant. However, there was not any significant difference regarding the endotrophin levels between control cases and non-fibrotic ILD patients. Smoked cigarette pocket x year showed a significant positive correlation and DLCO % and KCO % showed a significant negative correlation with the endotrophin levels.Conclusion:Serum endotrophin levels significantly increase in fibrotic ILD patients compared with the non-fibrotic ILD patients and control cases. Endotrophin may be suggested as a diagnostic marker in fibrotic interstitial lung diseases.

Methacholine Challenge Testing: Comparison of FEV1 and Airway Resistance Parameters.

A 20% reduction in the FEV1 is routinely used as an end point for methacholine challenge testing (MCT). Measurement of FEV1 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 FEV1 measurement in evaluating the responsiveness to methacholine during MCT. 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 FEV1 at each step of MCT. 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 H2O/L/s vs -0.09 ± 0.32 cm H2O/L/s) and at 15 Hz (-0.29 ± 0.2 cm H2O/L/s vs -0.1 ± 0.19 cm H2O/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 FEV1 non-responders at the onset of respiratory symptoms during MCT compared with baseline. 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 FEV1 non-responders with methacholine-induced asthma-like symptoms. (ClinicalTrials.gov registration NCT02343419.).

Using airway resistance measurement to determine when to switch ventilator modes in congenital diaphragmatic hernia: a case report

BackgroundCongenital diaphragmatic hernia is a deficiency of the fetal diaphragm resulting in herniation of the abdominal viscera into the thoracic cavity. The best method of respiratory management of congenital diaphragmatic hernia is unclear, but high frequency oscillatory ventilation is often used as the initial ventilator mode for severe congenital diaphragmatic hernia. When it becomes impossible to maintain the pre-ductal saturations, the timing of successful switching of the ventilation mode from high frequency oscillatory ventilation to conventional mechanical ventilation remains unclear. Herein, we reported two cases in which airway resistance measurements based on pulmonary function tests were used for making the decision to switch the ventilator mode from high frequency oscillatory ventilation to conventional mechanical ventilation in patients with left isolated congenital diaphragmatic hernia.Case presentationTwo 0-day-old infants with congenital diaphragmatic hernia were admitted to our hospital. In both patients, high frequency oscillatory ventilation was started initially, and the levels of saturation gradually rose within a few hours after birth. After 24 h of high frequency oscillatory ventilation, the level of saturation decreased, and the dissociation of pre-ductal and post-ductal saturation re-occurred. The respiratory-system resistance was 515 and 403 cmH2O·kg/L/s, respectively. Because the respiratory-system resistance was elevated, we decided to change the ventilator mode from high frequency oscillatory ventilation to conventional mechanical ventilation. After switching to conventional mechanical ventilation, the patients’ heart rate and saturation increased immediately.ConclusionsIn patients with congenital diaphragmatic hernia, resistance levels of > 400 cmH2O·kg/L/s may indicate high airway resistance and suggest greater alveolar vibration attenuation. When respiratory-system resistance reaches over 400 cmH2O·kg/L/s, it may be an optimal time for switching from high frequency oscillatory ventilation to conventional mechanical ventilation.

Acupuncture inhibited airway inflammation and group 2 innate lymphoid cells in the lung in an ovalbumin-induced murine asthma model.

Group 2 innate lymphoid cells (ILC2s) are known to serve important functions in the pathogenesis of allergic airway inflammation. Studies have shown that acupuncture has an anti-inflammatory effect in the airways. However, how acupuncture treatment affects innate immunity, especially with regard to the function of ILC2s in ovalbumin (OVA)-induced allergic airway inflammation, is poorly understood. BALB/c mice were injected and subsequently challenged with OVA ± treated with manual acupuncture. At the end of the experimental course, lung function was assessed by measurement of airway resistance (RL) and lung dynamic compliance (Cdyn). Cytokine levels were detected by enzyme-linked immunosorbent assay (ELISA). ILC2 proportions in the lung were analyzed by flow cytometry. The results showed that airway inflammation and mucus secretion were significantly suppressed by acupuncture treatment. RL decreased while Cdyn increased after acupuncture treatment. There was an apparent decrease in the bronchoalveolar lavage fluid (BALF) concentrations of interleukin (IL)-5, IL-13, IL-9, IL-25 and IL-33 and an increase in soluble IL-33 receptor (sST2) levels compared with untreated asthmatic mice. Acupuncture also reduced the lin-CD45+KLRG1+ST2+ cell proportion in the lung. In conclusion, this study has demonstrated that acupuncture treatment alleviates allergic airway inflammation and inhibits pulmonary ILC2 influx and IL-5, IL-9 and IL-13 production. The inhibition of ILC2s by acupuncture may be associated with the IL-33/ST2-signaling pathway and IL-25 levels, thereby offering protection from the respiratory inflammation associated with asthma.

Cheek support affects lung mechanics measurements of tidal-based spontaneous breathing

Background and Objective: Patients are required to support their cheeks during breath-occluding lung function tests. This prevents cheek expansion which would alter pressure measured at the mouth, and, consequently, lung mechanics measurements. To date, the effect of cheek support on airway resistance measurements has been assessed. However other lung mechanics have not been studied as thoroughly, and no algorithm to account for the effect of missing cheek support on lung mechanics measurements has been developed.Methods: Lung mechanics were assessed with a breath occlusion test during light panting in healthy subjects with and without cheek support in a body plethysmograph. Average model-based airway resistance, lung elastance, and a parameter representing the viscoelastic were measured. Results were compared to quantify the effect of cheek support on these three parameters.Results: In the nine healthy subjects (5 Female, 4 Male) recruited for this study, all mechanics tended to be underestimated when cheeks were unsupported. Changes in elastance, resistance, and viscoelastic parameter ranged between 1.6–66.8 %, -4.5–21.8 %, and -4.7–68.2 %, respectively, when cheek support was added. The underestimation was due to reduced mouth pressure during cheek expansion when the breath was occluded. The variance of lung mechanics parameters did not change with cheek support in all subjects.Conclusions: The error in lung mechanics measurement caused by unsupported cheeks was subject dependent. Hence, no rule-of-thumb could be identified to reconstruct missing cheek support. For correct lung mechanics measurements during breath-occluding lung tests, patients must have adequate cheek support.Abbreviations:ROCC: Occlusion resistance; COPD: Chronic Obstructive Pulmonary Disorder; SB: spontaneous breathing.

Age-Dependent Progression in Lung Pathophysiology can be Prevented by Restoring Fatty Acid and Ceramide Imbalance in Cystic Fibrosis.

Cystic fibrosis (CF) is a progressive disease which causes a continuous decline in lung capacity with age. Our study aimed to investigate the age-dependent deterioration in lung function and the effects of treatment with Fenretinide formulation (LAU-7b) in Cftr knockout (KO) mice. Non-invasive whole-body plethysmography (WBP) was done to measure the baseline lung functions of KO and wild-type (WT) mice at the ages of 2 and 4months. Mice were then treated for 21days with PBS or 10mg/kg/day LAU-7b initiated at 4 and 7months. Standard airway resistance measurements, haematoxylin and eosin staining, and analysis of lipids, and markers of oxidation were performed. The 4- and 7-month-old KO mice had significantly higher lung enhanced pause (Penh) and resistance values than age-matched WT mice and 2-month-old KO mice. Likewise, analysis of ceramides showed that PBS-treated mice had higher levels of long-chain ceramides (LCCs; C14-C18) and lower levels of very-long-chain ceramides (VLCCs; C24-C26) compared to LAU-7b-treated mice. Cftr KO mice displayed markedly greater inflammatory cell infiltration and epithelial hyperplasia at the ages of 2, 4, and 7months compared to WT. LAU-7b treatment significantly diminished this cellular infiltration and epithelial hyperplasia compared to PBS-treated mice. Our results demonstrate a progressive age-dependent decline in lung function in Cftr KO mice. Treatment with LAU-7b corrects the lipid imbalance observed in the aging KO and WT mice and, more importantly, inhibits the age-dependent deterioration in lung physiology and histopathology.

Body plethysmography for measuring airway resistance in patients with bilateral vocal fold immobility

ObjectiveThis study investigated the reliability of body plethysmography in comparison to spirometry in objectively measuring upper airway functions. MethodsThe study population consisted of 53 participants, 23 patients with BVFI after endolaryngeal laser posterior cordectomy and 30 healthy volunteers. All of them had body plethysmography (airway resistance, Raw), spirometry (ratio of forced expiratory flow at 50% to forced inspiratory flow at 50%, FEF50/FIF50 and peak inspiratory flow, PIF), 6 min-walking-test (6MWT) and Medical Research Council (MRC) dyspnea scale measurements. The tests were repeated and reliability was evaluated using intraclass correlation (ICC) and Spearman correlation. ResultsThe reliability of Raw was high with ICC of 0.92, comparable to the spirometry measurements: FEF50/FIF50(ICC = 0.72) and PIF (ICC = 0.97). The mean of Raw was significantly higher in patient group. A strong significant correlation between Raw and MRC dyspnea scale (r = 0.79; p<0.05) and a moderate negative correlation between Raw and 6MWT (r = 0.4; p<0.05) was demonstrated. ConclusionBody plethysmography (Raw) is a reliable tool in objective measurement of upper airway resistance that reflects the patient's perception of breathlessness. A larger number of participants are necessary to confirm this finding.

Measuring Airway Resistance and Characterizing the Flow‐Volume Envelope with External Expiratory Loading in Healthy Adults

Expiratory flow limitation is a key characteristic in chronic obstructive pulmonary disease (COPD). Increased airway resistance occurs due to bronchoconstriction, destruction of elastic tissue in the airways, and mucus hypersecretion from goblet cells caused by irritation of the epithelium. Obstruction can lead to dynamic hyperinflation, dyspnea, and exercise intolerance. However, increased airway resistance is just one of many abnormalities in COPD and asthma ‐ COPD in particular is an exceedingly heterogeneous disease. Therefore, isolating the effects of expiratory airflow limitation is challenging.PURPOSEIn order to study abnormal lung mechanics in isolation, we measured pulmonary function with and without expiratory loading in healthy adults.METHODSForty‐eight volunteers (26±5 yr, 171.8±10.2 cm, 72.2±13.3 kg) completed spirometry and body plethysmography according to the ATS/ERS standards under three randomized conditions: control, expiratory loading of 7 and 11 cmH2O. The expiratory load was added by installing a threshold inspiratory muscle trainer in reverse. We analyzed the shape of the flow‐volume (F‐V) loops with rectangular area ratio (RAR) using custom MATLab software.RESULTSAirway resistance was increased (F[1.5, 27.5]= 446.0, p&lt;0.05) with 7 and 11 cmH2O vs control (9.20±1.02 and 11.76±1.68 cmH2O vs. 2.53± 0.80 cmH2O). RAR (F[1.9, 77.9]= 3.71, p&gt;0.05) was reduced with 7 and 11 cmH2O vs control (0.45±0.07 and 0.47±0.09L vs. 0.48±0.08L). FEV1 was reduced (F[1.6, 60.38.6]= 67.54, p&lt;0.05) with 7 and 11 cmH2O vs control (3.26±0.82 and 3.23±0.79L vs. 4.03±1.04L). FVC was also reduced (F[1.5, 55.31] = 77.71, p&lt;0.05) with 7 and 11 cmH2O vs control (4.15±1.01 and 4.17±1.02L L vs. 5.05±1.33L L). PEF was reduced (F[1.5, 55.99] = 72.69, p&lt;0.05) with 7 and 11 cmH2O vs control (6.02±1.65 and 5.95±1.85L vs. 8.39±2.85L L). FEV1/FVC (F[1.9, 69.17] = 5.5, p&gt; 0.05) and FRC (F[1.863, 33.53]= 0.93, p&lt;0.05) were not different between resistance conditions or compared to the control.CONCLUSIONSExpiratory loading reduced FEV1, FVC, PEF and provided a doseresponse in airway resistance and RAR. There were no differences in FEV1/FVC. While RAR was reduced with expiratory loading, the magnitude was of little clinical importance. Therefore, a concave expiratory F‐V relationship was consistently absent – a key limitation for model comparison with pulmonary function in COPD. This is most likely due to the imposed resistance being applied outside of the airways, leading to higher airway pressures. The higher airway pressures are likely to resist dynamic airway compression and either maintain the equal pressure point position or possibly move it proximally.

Effect of Disease Severity on Respiratory Impedance in Parkinson's Disease.

Background:Parkinson’s disease (PD) is a progressive neurodegenerative disorder. PD has been traditionally perceived as a motor disorder. However, it is frequently associated with pulmonary dysfunction which has been assessed by Spirometry, an effort-dependent technique.Purpose:To evaluate in patients with PD the effect of disease severity on respiratory impedance using Impulse Oscillometry (IOS) and to correlate with Spirometry.Methods:The study was conducted on 30 patients diagnosed with PD. Pulmonary function was assessed by IOS and spirometer. IOS is an effort-independent technique that uses sound waves of different frequencies to measure airway resistance. Spirometer measures the lung volume and generates flow–volume and volume–time relationship.Results:The mean age of patients was 60.1±9.45. Resistance at 5 Hz (R5) was found to be negatively correlated with forced expiratory volume in the first second of the FVC manoeuver (FEV1) (r = –0.628, P = .002), FEV1/FVC (forced vital capacity) (r = –0.487, P = .025), and PEF (r = –0.599, P = .004), and resistance at 20 Hz (R20) with FEV1 (r = –0.474,P = .029) and PEF (r = –0.522, P = .015). There was significant increase in R5 (0.32(0.36–0.28) vs 0.47(0.60–0.36); P = .04) and R20 (0.25(0.28–0.20) vs 0.30(0.40–0.25); P = .04) in stage II as compared to stage I of Hoehn–Yahr scale.Conclusion:IOS might be a promising tool for diagnosis of respiratory dysfunction in addition to Spirometry, especially in cases where patients are not able to perform forced manoeuvers.

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.

Chronic Refractory Cough: Objective Improvement With Aerodynamic-Focused

Previous investigations have reported that a chronic cough that is refractory to medical therapies improves with behavioral therapies. However, the treatment parameters that may account for improvement in cough symptoms have not yet been objectively documented. The purpose of this study was to document changes in chronic refractory cough using a breath training protocol. The charts of 27 patients with a long-term chronic cough (>6 months) refractory to various medical treatments were reviewed. These patients received 2-4 sessions of breath training therapy over a 6-month period. Treatment sessions consisted of breathing modification exercises such as those reported in the literature. Aerodynamic parameters including mean estimated subglottal air pressure, mean airflow rate, laryngeal airway resistance, and maximum phonation time were obtained before treatment and 6 months after therapy. Patients also completed the Cough Severity Index at the first visit and 6 months after treatment. Twenty four of the 27 patients (M:F = 6:21), with a mean age of 62.4 (range = 28-78, median = 66) had significant Cough Severity Index improvement from 16.74 to 10.04 (P< 0.001) after therapy. Maximum phonation time increased significantly from 12.00 to 16.38 seconds (P= 0.006); mean estimated subglottic air pressure decreased significantly from 7.58 to 6.36 cm H2O (P= 0.004); laryngeal airway resistance decreased significantly from 52.97 to 40.64 ppm (P= 0.013). This investigation provides evidence that patients who followed a protocol that focused on a breath training program reduced their chronic cough. Significant relationships between patient self-assessment of chronic cough and aerodynamic measures of subglottic pressure and glottal airway resistance were found in this group.