Sensitivity of impulse oscillometry and spirometry in beta-blocker induced bronchoconstriction and beta-agonist bronchodilatation in asthma

Window of opportunity for respiratory oscillometry: A review of recent research

Oscillometry has been around for almost 70 years, but there are still many unknowns. The test is performed during tidal breathing and is therefore free from patient-dependent factors that could influence the results. The Forced Oscillation Technique (FOT), which requires minimal patient cooperation, is gaining ground, particularly with elderly patients and children. In pulmonology, it is a valuable tool for assessing obstructive conditions (with a distinction between central and peripheral obstruction) and restrictive disorders (intrapulmonary and extrapulmonary). Its sensitivity allows the assessment of bronchodilator and bronchoconstrictor responses. Different lung diseases show different patterns of changes in FOT, especially studied in asthma and chronic obstructive pulmonary disease. Because of these differences, many studies have analysed the usefulness of this technique in different areas of medicine. In this paper, the authors would like to present the basics of oscillometry with the areas of its most recent clinical applications.

Clinical impact of obesity on oscillometry lung mechanics in adults with asthma

BACKGROUND

In the year 2035, projections have estimated that 5% of the Scottish population will be morbidly obese defined as a body mass index (BMI) greater than or equal to 40 kg/m2. Airway oscillometry is an effort-independent test akin to bronchial sonar which measures resistance and compliance.

OBJECTIVE

To evaluate the impact of obesity on lung mechanics using oscillometry.

METHODS

Clinical data for 188 patients with respiratory physician-diagnosed moderate-to-severe asthma were retrospectively collected and analyzed.

RESULTS

Obesity (BMI 30-39.9 kg/m2) and morbid obesity (BMI ≥ 40 kg/m2) were associated with a significantly worse heterogeneity of peripheral resistance between 5 Hz and 20 Hz and peripheral compliance as low-frequency reactance at 5 Hz and area under the reactance curve, as compared with normal weight (BMI 18.5-24.9 kg/m2). Cluster analysis incorporating oscillometry identified a patient cohort who was older, obese, and female with combined impairment of spirometry and oscillometry coupled with more frequent severe exacerbations.

CONCLUSION

Obesity is associated with worse peripheral airway dysfunction in moderate-to-severe asthma, including a patient cluster who was older, obese, and female with more frequent exacerbations.

Efficacy of biologic therapy on airway hyperresponsiveness in asthma

Airway hyperresponsiveness refers to an exaggerated bronchial constrictor response to a given exogenous inhaled agent and is governed by airway smooth muscle along with mucosal inflammation in asthma. In recent years, the advent of biologics and antialarmins has transformed severe asthma treatment in terms of reducing oral-corticosteroid-requiring exacerbations and improving disease control, asthma quality of life, and spirometry-measured lung function. In contrast, there have been comparatively fewer studies investigating the efficacy of biologics in airway hyperresponsiveness. In this focused review, we summarize the existing evidence base in this area regarding omalizumab, mepolizumab, benralizumab, and tezepelumab.

Airwave oscillometry and spirometry in children with asthma or wheeze

OBJECTIVE

Lung function testing is used in diagnosing asthma and assessing asthma control. Spirometry is most commonly used, but younger children can find performing this test challenging. Non-volitional tests such as airwave oscillometry (AOS) may be helpful in that population. We compared the success of spirometry and AOS in assessing bronchodilator responsiveness in children.

METHODS

AOS was conducted alongside routine lung function testing. Resistance at 5 Hz (R5), the difference between the resistance at 5 and 20 Hz (R5-20) and the area under the reactance curve (AX) were assessed. Patients between 5 and 16 years old attending clinic with wheeze or asthma were assessed. Patients performed AOS, followed by spirometry and were then given 400 µg salbutamol; the tests were repeated 15 minutes later.

RESULTS

Lung function testing was performed in 47 children of whom 46 (98%) and 32 (68%) performed acceptable baseline oscillometry and spirometry, respectively (p < 0.001). Children unable to perform acceptable spirometry were younger (7.35, range: 5.4-10.3 years) than those who could (10.4, range: 5.5-16.9 years), p < 0.001. The baseline z-scores of AOS R5 correlated with FEV₁ (r = 0.499, p = 0.004), FEF₇₅ (r = 0.617, p < 0.001), and FEV₁/FVC (r = 0.618, p < 0.001). There was a positive bronchodilator response assessed by spirometry (change in FEV₁ ≥ 12%) in eight children which corresponded to a change in R5 of 36% (range: 30%-50%) and a change in X5 of 39% (range: 15%-54%).

CONCLUSIONS

Oscillometry is a useful adjunct to spirometry in assessing young asthmatic children's lung function. The degree of airway obstruction, however, might affect the comparability of the results of the two techniques.

Potentiality of impulse oscillometry to evaluate bronchodilator reversibility in untreated adult patients with newly diagnosed asthma

BACKGROUND

Identifying positive bronchodilator reversibility (BDR) helps the diagnosis of asthma. However, not all patients can adequately perform the forced expiration during the spirometry test. An alternative test is required. Impulse oscillometry (IOS) is an effort-independent technique that enables the measurement of lung mechanics during quiet tidal breathing. We investigated the potentiality of IOS to evaluate BDR in untreated adult patients with newly diagnosed asthma (UAPNDS).

METHODS

All UAPNDS (aged 20-80 years) who never smoke and underwent IOS and spirometry before and after salbutamol inhalation at their initial visit to the hospital from March 22, 2017, to December 31, 2019, were identified. A total of 323 patients were enrolled. Data from the medical record, including demographic characteristics, laboratory examination, spirometric data, and IOS parameters, were retrospectively reviewed. The associations of parameters with the positive BDR and the performance of parameters in predicting the positive BDR were evaluated by statistical methods.

RESULTS

Patients (n = 323) had a median age of 64 years and were mostly female (67.5%). Several variables, including serum total immunoglobulin level, blood eosinophil counts, blood eosinophil percentage (%), and two IOS parameters, were found to be different between the positive (n = 93) and negative BDR (n = 230) groups. Multivariate logistic regression analyses after adjustment by cofactors revealed that the percentage change of the area under the reactance curve between 5 Hz and resonant frequency [ΔAx (%)] after salbutamol inhalation was the only independent factor for the positive BDR. The area under the receiver operating characteristic curve of ΔAx (%) in predicting the positive BDR was 0.614 ( p = 0.0013), and its optimal cutoff value was -53.8% (sensitivity, 39.78% and specificity, 80.43%).

CONCLUSION

In addition to spirometry, ΔAx (%), an IOS parameter, may serve as a novel indicator to evaluate BDR in UAPNDS.

Ceiling effect of beclomethasone/formoterol/glycopyrronium triple fixed-dose combination in COPD: A translational bench-to-bedside study

BACKGROUND

Currently, data on the possible synergy of adding a LAMA to ICS/LABA combination are missing and no studies assessed whether triple therapy may induce ceiling bronchodilator effect. A translational study was performed to investigate the interaction between glycopyrronium bromide (GB) and beclomethasone dipropionate (BDP)/formoterol fumarate (FF) combination in human isolated airways and the effect on FEV₁ and small airway resistance of BDP/FF/GB in COPD.

METHODS

The interaction of adding GB to BDP/FF combination was tested in vitro in medium and small airways via Bliss, Loewe, and Highest Single Agent models. The peak and trough effect on FEV₁ and R5-R19 of salbutamol on top of BDP/FF/GB 100/6/12.5 μg FDC via extrafine formulation was investigated in severe COPD patients after two weeks of treatment.

RESULTS

GB plus BDP/FF elicited significant synergistic bronchorelaxation in medium and small isolated airways (overall maximal effect: +32% vs. additive effect). No significant (P > 0.05) improvement in R5-R19 was detected when salbutamol was administered on top of BDP/FF/GB 100/6/12.5 μg FDC (peak -0.12 ± 0.22 cmH₂O/L/s, trough -0.23 ± 0.25 cmH₂O/L/s). Salbutamol significantly (P < 0.01) increased FEV₁ when administered on top of triple FDC (peak +145 ± 119 ml, trough +221 ± 111 ml).

CONCLUSION

The synergistic interaction detected in vitro when adding GB to BDP/FF combination may lead to ceiling bronchorelaxation of small airways in vivo, an effect that may improve hyperinflation in subjects with small airway disease and, thus, explain the substantial clinical benefits of triple combination therapy administered via extrafine formulation in severe COPD patients.

STUDY REGISTRATION

ISRCTN94089001.

Diagnostic value of volumetric capnography in patients with chronic cough variant asthma

OBJECTIVES

To evaluate the quantitative changes and diagnostic performance of volumetric capnography (VCap) parameters in patients with cough variant asthma.

METHODS

This cross-sectional study enrolled 31 patients with cough variant asthma and 30 patients with chronic cough without asthma between November 2010 and March 2012. VCap measurements were recorded at baseline, during the five steps of the histamine challenge, and after bronchodilation with salbutamol. They were then compared between the baseline and histamine challenge, and between the two groups. Receiver operating characteristic curve analysis was performed for different VCap measurements.

RESULTS

The slope of phase III (dc\dv3) and the ratio of phase III slope to phase II slope (SR23%) decreased from baseline upon challenge with 1.1 mg histamine in cough variant asthma patients but increased in patients with chronic cough without asthma. Additionally, the change upon challenge with 1.1 mg histamine in dc\dv3 from baseline (S6-S1dc\dv3) in cough variant asthma patients had the largest area under the curve (AUC) (0.814, 95% CI: 0.697-0.931; p<0.001). The AUC for change upon challenge with 1.1 mg histamine in SR23% from baseline was 0.755 (95%CI: 0.632-0.878; p<0.001). At a cutoff of 19.8, S6-S1 dc\dv3 had a sensitivity of 74.2% and specificity of 90.0% and at a cutoff of 40.7, S6-S1 SR23% had a sensitivity of 48.4% and specificity of 96.7%.

CONCLUSION

Patients with cough variant asthma exhibit distinct VCap responses for dead space parameters upon challenge with histamine in comparison to patients with chronic cough. VCap parameters like phase III slope and phase III/phase II slope ratio could be used to aid the diagnosis of cough variant asthma.

Impulse oscillometry reference values and bronchodilator response in three- to five-year old children living at high altitude

Introduction

Impulse oscillometry (IOS) is used to measure airway impedance. It is an effective tool for diagnosing and treating respiratory diseases, and it has the advantage that it does not require forced respiratory maneuvers. IOS reference values are required for each population group.

Objective

This study aimed to determine the IOS reference values and bronchodilator response in healthy preschool children living in Bogotá, Colombia.

Methods

We performed a cross-sectional study in preschool children who had no history of respiratory disease; 96 children fit the parameters for testing to determine normal values according to the American Thoracic Society and European Respiratory Society criteria.

Results

Values for respiratory resistance (Rrs) and reactance (Xrs) at 5, 10, and 20 Hz, respiratory impedance (Zrs, and resonance frequency (Fres) were established. Height was the most influential independent variable for IOS values; an increase in height led to a reduction in Rrs5 and Rrs20 and an increase in Xrs5. After the administration of 400 mcg of salbutamol the values for Rrs5(−17.48%), Rrs20(−8.63%), Fres (−10.68%), and area of reactance (−35.44%) were reduced, meanwhile Xrs5 (15.35%) was increased.

Conclusions

Normal IOS values before and after the administration of 400 mcg of salbutamol were determined for a population of children aged 3–5 years at 2,640 m. Reference IOS equations for these children are presented. A relative change of up to −28% and 36% after the use of salbutamol for respiratory resistance and reactance, respectively, should be considered as an upper limit of the normal range, and possible appropriate cut-off values for defining significant response for evaluating therapeutic interventions.

I Say IOS You Say AOS: Comparative Bias in Respiratory Impedance Measurements

Background

The forced oscillation technique (FOT) measures respiratory impedance during normal tidal breathing and requires minimal patient cooperation.

Objective

To compare IOS and AOS devices in patients with asthma and COPD.

Methods

We compared two different FOT devices, namely impulse oscillometry using a loudspeaker (IOS: Jaeger Masterscreen) and airwave oscillometry using a vibrating mesh (AOS: Thorasys Tremoflo) for pre- and post-bronchodilator measurements in 84 patients with asthma and COPD.

Results

The overall pattern of measurement bias was for higher resistance with IOS and higher reactance with AOS, this being the case in asthma and COPD separately. There were small but significantly higher values using IOS for resistance at 5 Hz (R5) and 20(19) Hz (R20(19)). In converse, values for reactance at 5 Hz (X5), reactance area (AX) and resonant frequency (Fres) were significantly higher using AOS but to a much larger extent. The difference in AX between devices was more pronounced in COPD than in asthma. Salbutamol reversibility as % change was greater in asthma than COPD patients with AX but not FEV1.

Conclusion

Our study showed evidence of better agreement for resistance than reactance when comparing IOS and AOS, perhaps inferring that AOS may be more sensitive at measuring reactance in patients with airflow obstruction.

Electronic supplementary material

The online version of this article (10.1007/s00408-019-00247-y) contains supplementary material, which is available to authorised users.

Usefulness of impulse oscillometry for the assessment of bronchodilator response in elderly patients with chronic obstructive airway disease

BACKGROUND

Impulse oscillometry (IOS) is a noninvasive and convenient technique to measure both airway resistance and reactance. This study aimed to evaluate whether IOS can be used to measure bronchodilator response (BDR) in elderly patients with asthma and chronic obstructive pulmonary disease (COPD) and also describe the difference between asthma and COPD.

METHODS

Seventy patients (30 and 40 with asthma and COPD, respectively) over 65 years of age were enrolled. IOS and spirometry measurements were obtained before and after bronchodilator administration. Correlation analysis was used to compare the percentage changes in spirometry and IOS parameters after bronchodilator administration between the asthma and COPD groups.

RESULTS

The changes in IOS parameters after bronchodilator administration were strongly correlated with changes in forced expiratory volume at 1 second (FEV₁) and forced expiratory flow at 25-75% (FEF_25-75). However, the percentage changes in IOS parameters failed to discriminate between the asthma and COPD groups. Receiver operating characteristic curve (ROC) analysis of resistance at 5 and 20 Hz (R5-20) at the best cutoff (-15.4% change) showed both high sensitivity and specificity for BDR.

CONCLUSIONS

IOS serves as a reliable and useful technique for identifying BDR in elderly patients with chronic obstructive airway disease. There was a difference in IOS parameters between the asthma and COPD groups; however, it was difficult to distinguish between both diseases. Further larger studies are required to investigate the real implications of using IOS in the clinical practice.

Sensitivity of Lung Resistance and Compliance to Beta-Blocker Induced Bronchoconstriction and Long Acting Beta-Agonist Withdrawal in COPD

Little is known about impulse oscillometry (IOS) in COPD. IOS is an effort independent measure of lung resistance and reactance (compliance). We assessed how frequency dependence of resistance (R) and reactance (X) changed in response to bronchoconstriction with carvedilol followed by long acting beta-agonist (LABA) withdrawal. N = 12 patients with moderate to severe COPD were analysed, who had ≥ 100 ml fall in FEV₁ with carvedilol. Compared to baseline taking ICS/LABA there were 21, 59, and 135% significant changes in resistance at 5 Hz (R5), reactance at 5 Hz (X5), and reactance area (AX), respectively, with carvedilol, while after LABA withdrawal only AX showed a further significant increase to 210% (i.e. reduced compliance). Hence changes in lung compliance rather than resistance play a more important role in the beta-2 receptor-mediated responses in COPD.

Bronchoprotective tolerance with indacaterol is not modified by concomitant tiotropium in persistent asthma

BACKGROUND

Tiotropium is a long acting muscarinic antagonist (LAMA), licensed as triple therapy with inhaled corticosteroid and long-acting beta-agonist (ICS/LABA). There may be a synergistic benefit between LAMA and LABA as a consequence of receptor cross-talk, which in turn could modify beta-2 receptor downregulation and associated tolerance induced by LABA.

OBJECTIVE

We hypothesize this mechanism may result in a reduction of airway hyperresponsiveness (AHR) when using triple therapy.

METHODS

We evaluated 14 non-smoking asthmatics using an open-label, randomized crossover design. ICS with Indacaterol and Tiotropium (IND/TIO) vs ICS with Indacaterol (IND) over 4 weeks with challenge performed after first and last doses at trough.

RESULTS

We found no significant difference in mannitol sensitivity, expressed as the provocative dose of mannitol required to reach a 15% drop in FEV₁ , or mannitol reactivity, expressed as the response dose ratio (RDR: max % fall in FEV₁ /cumulative dose), when comparing ICS/IND/TIO to ICS/IND. Geometric mean fold differences for RDR comparing single and chronic dosing were 3.26-fold (95% CI 1.46-7.29) and 2.51-fold (95% CI 1.32-4.79) for IND and IND/TIO, respectively. Furthermore, salbutamol recovery post-challenge was significantly blunted after chronic compared to single dosing with either ICS/IND (P<.005) or ICS/IND/TIO (P<.05).

CONCLUSION AND CLINICAL RELEVANCE

Our data suggest that concomitant tiotropium does not modify the bronchoprotective tolerance induced by Indacaterol, in turn suggesting that cross-talk may not be clinically relevant when using triple therapy. This study was registered on clinicaltrials.gov as NCT02039011.

Asthma as a disruption in iron homeostasis

Over several decades, asthma has evolved from being recognized as a single disease to include a diverse group of phenotypes with dissimilar natural histories, pathophysiologies, responses to treatment, and distinctive molecular pathways. With the application of Occam's razor to asthma, it is proposed that there is one cause underlying the numerous phenotypes of this disease and that the responsible molecular pathway is a deficiency of iron in the lung tissues. This deficiency can be either absolute (e.g. asthma in the neonate and during both pregnancy and menstruation) or functional (e.g. asthma associated with infections, smoking, and obesity). Comparable associations between asthma co-morbidity (e.g. eczema, urticaria, restless leg syndrome, and pulmonary hypertension) with iron deficiency support such a shared mechanistic pathway. Therapies directed at asthma demonstrate a capacity to impact iron homeostasis, further strengthening the relationship. Finally, pathophysiologic events producing asthma, including inflammation, increases in Th2 cells, and muscle contraction, can correlate with iron availability. Recognition of a potential association between asthma and an absolute and/or functional iron deficiency suggests specific therapeutic interventions including inhaled iron.

Respiratory effect of beta-blocker eye drops in asthma: population-based study and meta-analysis of clinical trials

AIMS

To measure the prevalence of beta-blocker eye drop prescribing and respiratory effect of ocular beta-blocker administration in people with asthma.

METHODS

We measured the prevalence of ocular beta-blocker prescribing in people with asthma and ocular hypertension, and performed a nested case-control study (NCCS) measuring risk of moderate exacerbations (rescue steroids in primary care) and severe exacerbations (asthma hospitalization) using linked data from the UK Clinical Practice Research Datalink. We then performed a systematic review and meta-analysis of clinical trials evaluating changes in lung function following ocular beta-blocker administration in people with asthma.

RESULTS

From 2000 to 2012, the prevalence of non-selective and selective beta-blocker eye drop prescribing in people with asthma and ocular hypertension fell from 23.0% to 13.4% and from 10.5% to 0.9% respectively. In the NCCS, the relative incidence (IRR) of moderate exacerbations increased significantly with acute non-selective beta-blocker eye drop exposure (IRR 4.83, 95% CI 1.56-14.94) but not with chronic exposure. In the meta-analysis, acute non-selective beta-blocker eye drop exposure caused significant mean falls in FEV1 of -10.9% (95% CI -14.9 to -6.9), and falls in FEV1 of ≥20% affecting one in three. Corresponding values for selective beta-blockers in people sensitive to ocular non-selective beta-blockers was -6.3% (95% CI -11.7 to -0.8), and a non-significant increase in falls in FEV1 of ≥20%.

CONCLUSION

Non-selective beta-blocker eye drops significantly affect lung function and increase asthma morbidity but are still frequently prescribed to people with asthma and ocular hypertension despite safer agents being available.

Is Gly16Arg β2 Receptor Polymorphism Related to Impulse Oscillometry in a Real-Life Asthma Clinic Setting?

PURPOSE

We evaluated whether Gly16Arg beta2-receptor genotype relates to impulse oscillometry (IOS) in a real-life clinic setting.

METHODS

Patients with persistent asthma taking inhaled corticosteroid ± long-acting beta-agonist (ICS ± LABA) were evaluated. We compared genotype groups comprising either no Arg copies (i.e. GlyGly) versus one or two Arg copies (i.e. ArgArg or ArgGly). IOS outcomes included total airway resistance at 5 Hz (R5), central airway resistance at 20 Hz (R20), peripheral airway resistance (R5-R20), reactance at 5 Hz, area under reactance curve (AX) and resonant frequency (RF). In addition, we recorded ACQ-5 and salbutamol use.

RESULTS

One hundred and twelve ICS-treated asthmatic patients (mean ICS dose 1238 µg/day), mean age 43 years, ACQ 2.34, FEV1 82 %, R5 177 % were identified-89 were also taking LABA. 61 patients were GlyGly, while 14 were ArgArg and 37 were ArgGly. There were no significant differences in IOS outcomes, ACQ or salbutamol use between the genotypes. The allelic risk (as odds ratio) for less well-controlled asthma (as ACQ > 1.5) was 1.1 (95 % CI 0.72-1.68) in relation to each Arg copy with a corresponding odds ratio for abnormal R5-R20 > 0.07kPA/l.s being 0.91 (95 % CI 0.57-1.44). 71 % of patients had an ACQ > 1.5 in the GlyGly group, versus 67 % in GlyArg/ArgArg group, with corresponding figures for abnormal R5-R20 > 0.07 kPa/l.s being 69 versus 73 %.

CONCLUSION

In a real-life clinic setting for patients with poorly controlled persistent asthma taking ICS ± LABA, we found no evidence of any relationship of Gly16Arg to IOS, ACQ or salbutamol use.

Impulse oscillometry in acute and stable asthmatic children: a comparison with spirometry

OBJECTIVE

Lung function tests have attracted interest for the diagnosis and follow-up of childhood asthma in recent years. For patients who cannot perform forced expiratory maneuvers, impulse oscillometry (IOS), performed during spontaneous breathing, may be an alternative tool.

METHODS

Thirty-five acute, 107 stable asthmatic and 103 healthy children who presented to our clinic performed IOS followed by spirometry before and after salbutamol inhalation. The mean baseline and reversibility of IOS and spirometry parameters were compared between the groups. Correlation analyses were undertaken within the asthmatics, and the healthy controls separately. To distinguish the three groups, the sensitivity and specificity of baseline and reversibility values of IOS and spirometry were computed. When spirometry was taken as the gold standard, the discriminating performance of IOS to detect the airway obstruction and reversibility was investigated.

RESULTS

The mean absolute values of Zrs, R5, R5-R20, X5, X10, X15, Fres, AX, and all spirometric parameters, and the mean reversibility values of R5, R10, Fres, AX and forced expiratory volume in one second were different between the groups and the highest area under curve values to discriminate the groups was obtained from area of reactance (AX) and ΔAX. Zrs, all resistance (including R5-R20) and reactance parameters, Fres and AX were correlated with at least one spirometric parameter. Spirometric reversibility was detected by ≤-22.34 and ≤-39.05 cut-off values of ΔR5 and ΔAX, respectively.

CONCLUSIONS

IOS has shown a highly significant association with spirometric indices and reversibility testing. It may be a substitute for spirometry in children who fail to perform forced expiratory maneuvers.

Usefulness of impulse oscillometry for the assessment of airway hyperresponsiveness in mild-to-moderate adult asthma

BACKGROUND

Impulse oscillometry (IOS) is a novel method of assessing airway resistance. IOS is rarely used in assessing airway resistance after bronchoprovocation in adult asthma.

OBJECTIVE

To ascertain the degree of change in IOS measurements seen in patients with asthma undergoing bronchial challenge testing.

METHODS

Patients 18 to 65 years old with mild to moderate asthma, forced expiratory volume in 1 second (FEV1) greater than 80% predicted, and diurnal FEV1 variation less than 30% and taking inhaled corticosteroid (≤1,000 μg/day of beclomethasone dipropionate equivalent dose) were recruited. Sequential spirometry and IOS results were measured during bronchial challenge testing to inhaled methacholine and histamine.

RESULTS

The magnitude of percentage of change demonstrated in total airway resistance at 5 Hz was greater than that observed for FEV1 in the 2 bronchial challenge tests. For example, at a methacholine provocation concentration that caused a decrease in FEV1 of 20%, a 43.5% change (95% confidence interval 29.4-57.5) was seen in total airway resistance at 5 Hz as measured by IOS compared with a 23.3% change (95% confidence interval 18.7-27.9) in FEV1. The magnitude of change seen with other IOS outcomes, including peripheral airway resistance, area under the curve, and resonant frequency, also was greater compared with spirometry.

CONCLUSION

The potential application of IOS in the assessment of airway hyperresponsiveness in adult asthma has been demonstrated. Further population studies are required.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT01074853).

Effects of formoterol or salmeterol on impulse oscillometry in patients with persistent asthma

BACKGROUND

Effects of small-particle long-acting β-agonists on the small airways have been poorly documented.

OBJECTIVE

We used impulse oscillometry (IOS) to compare single and repeated dosing effects of small- and large-particle long-acting β-agonists.

METHODS

After a 1- to 2-week run-in period, patients received either 12 μg of small-particle hydrofluoroalkane 134a-formoterol solution or 50 μg of large-particle salmeterol dry powder twice daily plus inhaled corticosteroid for 1 to 2 weeks with a 1- to 2-week washout period in between. Measurements were made over 60 minutes after the first and last doses.

RESULTS

Sixteen patients completed the study as follows: mean age, 43 years; FEV1, 80%; forced midexpiratory flow between 25% and 75% of forced vital capacity (FEF(25-75)), 48%; total airway resistance at 5 Hz, 177%; peripheral airway resistance as the difference between 5 and 20 Hz, 0.18 kPa·L(-1)·s; Asthma Control Questionnaire score, 0.76; and inhaled corticosteroid dosage, 550 μg/d. There were significantly greater improvements with formoterol versus salmeterol in all IOS outcomes and FEF25-75, but not FEV1, at 5 minutes after the first dose, which were not sustained over 60 minutes. After the last dose, all IOS outcomes, but not FEV1 or FEF(25-75), were significantly better with formoterol over the entire 60 minutes: mean difference at 60 minutes between formoterol and salmeterol in total airway resistance at 5 Hz, 7.50% (95% CI, 1.56% to 13.43%, P = .02); central airway resistance at 20 Hz, 5.37% (95% CI, 0.13% to 10.62%, P = .045); peripheral airway resistance as the difference between 5 and 20 Hz, 12.76% (95% CI, 1.28% to 24.24%, P = .03); reactance area under the curve, 19.46% (95% CI, 7.56% to 31.36%, P = .003); reactance at 5 Hz, 11.19% (95% CI, 4.62% to 17.76%, P = .002); and resonant frequency, 9.34% (95% CI, 3.21% to 15.47%, P = .005). Peak expiratory flow significantly improved to a similar degree with both drugs.

CONCLUSION

Significant improvements in IOS outcomes but not spirometry results occurred after chronic dosing with formoterol compared with salmeterol. This might reflect better deposition to the entire lung, including the small airways.

Effect of gastroesophageal reflux disease on disease severity and characteristics of lung functional changes in patients with asthma

INTRODUCTION

Almost one third of patients with asthma have symptomatic evidence for coexisting gastroesophageal reflux disease (GERD), which is thought to be aggravating factor in asthma at least in some cases. We investigated the impact of coexisting GERD on asthma severity and parameters of lung function.

METHODS

Ninety two asthma patients diagnosed according to ATS criteria were studied. After full history and physical examination, asthma severity was measured in each patient using asthma control test (ACT). GERD symptoms was verified in each patient. Impulse oscillometry (IOS) and lung volume studies (using body-plethysmography and IOS) were performed. The difference between total airway resistance (TAWR) indicated by resistance at 5 Hz and central airway resistance (CAWR) as indicated by resistance at 20 Hz in oscillometry was calculated and considered as representative of resistance at peripheral airways (PAWR). The relationship between the presences of GERD symptoms, ACT score and parameters of lung function were analyzed.

RESULTS

PAWR and TAWR were both significantly higher in asthmatic patients with GERD symptoms than patients without GERD symptoms (256.64±161.21 versus 191.68±98.64; P=0.02, and 102.73±122.39 versus 56.76±71.43; P=0.01, respectively). However, no significant difference was noted in mean values of ACT, FEV1 (forced expiratory volume in 1 sec), FVC (forced vital capacity), PEF (peak expiratory flow), and CAWR in these two groups.

CONCLUSION

These findings suggest that the severity of asthma as measured by ACT score is not different in patients with and without GERD symptoms. However, total and peripheral airway resistance measured by IOS is significantly higher in asthmatic patients with GERD symptoms.

Respiratory impedance and response to salbutamol in healthy individuals and patients with COPD

BACKGROUND

Recent studies suggested that the bronchodilator response depends on airway obstruction. The forced oscillation technique (FOT) may help improve our understanding of the changes in respiratory mechanics that occur after the application of a bronchodilator.

OBJECTIVES

We aimed to (1) assess the response to salbutamol and to compare the impedance changes in healthy individuals and COPD patients, (2) investigate the effects of airway obstruction on this response and (3) evaluate the utility of the FOT as a complementary measurement to assess the response to the bronchodilator.

METHODS

Twenty-five healthy individuals and 82 patients with COPD were assessed with the FOT followed by spirometry before and after the use of salbutamol.

RESULTS

The changes exhibited by the COPD subgroups were greater than in the healthy individuals (p < 0.05). Increased obstruction resulted in decreased reductions in mean resistance and increased improvements in mean reactance (p < 0.001). In addition, the bronchodilation reduced the ventilation heterogeneity and the impedance modulus in all COPD stages (p < 0.05). The correlation coefficients for the spirometric and FOT changes were low (0.21-0.38).

CONCLUSIONS

In the initial phases of COPD (stage I), the effects of bronchodilation are greater than in healthy volunteers. The bronchodilator use improved the oscillatory mechanics in all of the studied groups of COPD patients. These improvements are reduced in more advanced phases of airway obstruction (II, III and IV). The FOT provides information that complements the data supplied by spirometry, contributing to an improvement in the evaluation of the bronchodilator response in COPD.

Adverse respiratory effect of acute β-blocker exposure in asthma: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

β-Blockers are avoided in asthma over concerns regarding acute bronchoconstriction. Risk is greatest following acute exposure, including the potential for antagonism of β2-agonist rescue therapy.

METHODS

A systematic review of databases was performed to identify all randomized, blinded, placebo-controlled clinical trials evaluating acute β-blocker exposure in asthma. Effect estimates for changes in respiratory function, symptoms, and β2-agonist response were pooled using random effects meta-analysis with heterogeneity investigated.

RESULTS

Acute selective β-blockers in the doses given caused a mean change in FEV1 of −6.9% (95% CI, −8.5 to −5.2), a fall in FEV1 of ≥20% in one in eight patients (P=.03), symptoms affecting one in 33 patients (P=.18), and attenuation of concomitant β2-agonist response of −10.2% (95% CI, −14.0 to −6.4). Corresponding values for acute nonselective β-blockers in the doses given were −10.2% (95% CI, −14.7 to −5.6), one in nine patients (P=.02), one in 13 patients (P=.14), and −20.0% (95% CI, −29.4 to −10.7). Following investigation of heterogeneity, clear differences were found for celiprolol and labetalol. A dose-response relationship was demonstrated for selective β-blockers.

CONCLUSIONS

Selective β-blockers are better tolerated but not completely risk-free. Risk from acute exposure may be mitigated using the smallest dose possible and β-blockers with greater β1-selectivity. β-Blocker-induced bronchospasm responded partially to β2-agonists in the doses given with response blunted more by nonselective β-blockers than selective β-blockers. Use of β-blockers in asthma could possibly be based upon a risk assessment on an individual patient basis.

Evaluation of pulmonary dysfunctions and acid-base imbalances induced by Chlamydia psittaci in a bovine model of respiratory infection

Background

Chlamydia psittaci (Cp) is a respiratory pathogen capable of inducing acute pulmonary zoonotic disease (psittacosis) or persistent infection. To elucidate the pathogenesis of this infection, a translational large animal model was recently introduced by our group. This study aims at quantifying and differentiating pulmonary dysfunction and acid–base imbalances induced by Cp.

Methods

Forty-two calves were grouped in (i) animals inoculated with Cp (n = 21) and (ii) controls sham-inoculated with uninfected cell culture (n = 21). For pulmonary function testing, impulse oscillometry, capnography, and FRC (functional residual capacity) measurement were applied to spontaneously breathing animals. Variables of acid–base status were assessed in venous blood using both (i) traditional Henderson-Hasselbalch and (ii) strong ion approach.

Results

Both obstructive and restrictive pulmonary disorders were induced in calves experimentally inoculated with Cp. Although disorders in respiratory mechanics lasted for 8–11 days, the pattern of spontaneous breathing was mainly altered in the period of acute illness (until 4 days post inoculation, dpi). Expiration was more impaired than inspiration, resulting in elevated FRC. Ventilation was characterised by a reduction in tidal volume (−25%) combined with an increased percentage of dead space volume and a significant reduction of alveolar volume by 10%. Minute ventilation increased significantly (+50%) due to a compensatory doubling of respiratory rate. Hyperventilatory hypocapnia at 2–3 dpi resulted in slightly increased blood pH at 2 dpi. However, the acid–base equilibrium was additionally influenced by metabolic components, i.e. the systemic inflammatory response, all of which were detected with help of the strong ion theory. Decreased concentrations of albumin (2–10 dpi), a negative acute-phase marker, resulted in a decrease in the sum of non-volatile weak acids (A_tot), revealing an alkalotic effect. This was counterbalanced by acidic effects of decreased strong ion difference (SID), mediated by the interplay between hypochloraemia (alkalotic effect) and hyponatraemia (acidic effect).

Conclusions

This bovine model was found to be suitable for studying pathophysiology of respiratory Cp infection and may help elucidating functional host-pathogen interactions in the mammalian lung.

Effects of intravenous and oral β-blockade in persistent asthmatics controlled on inhaled corticosteroids

OBJECTIVE

Despite their benefits in the treatment of cardiovascular disease, β-blockers are seldom used to treat asthmatics. We assessed the safety and tolerability of acute dosing with esmolol and propranolol in patients with asthma.

DESIGN

Post-hoc analysis of a double blind, randomised, placebo controlled trial of β-blocker use in asthma.

PATIENTS

Mild-to-moderate asthmatics on inhaled corticosteroids.

INTERVENTIONS

Each participant underwent a 6-8 week dose titration of oral propranolol. A subgroup received an intravenous bolus dose of esmolol (0.5 mg/kg). Measurements were recorded pre- and post-esmolol and first dose exposure to 10 mg, 20 mg, and 80 mg of propranolol. Tiotropium was given concurrently with propranolol. Bronchoconstriction was reflected as a fall in forced expiratory volume in 1 s (FEV1) or increase in total airway resistance at 5 Hz (R5).

RESULTS

12 patients completed the trial. There were no adverse effects on FEV1% or R5% following intravenous esmolol. There were significant reductions at 2 min post-esmolol in heart rate (-4.7 beats/min (bpm), 95% CI -7.9 to -1.3 bpm; p=0.002) and systolic blood pressure (-5.9 mm Hg, 95% CI -11.4 to -0.4 mm Hg; p=0.03). No bronchoconstriction was seen during up titration following the first dose of 10 mg, 20 mg or 80 mg of propranolol in the presence of tiotropium. No difference in the asthma control questionnaire at 80 mg propranolol was seen versus placebo in the presence of tiotropium.

CONCLUSIONS

Intravenous esmolol was administered without any adverse effects on pulmonary function in selected, stable, mild-to-moderate asthmatics controlled on inhaled corticosteroids. Tiotropium prevented propranolol induced bronchoconstriction after acute dosing during up-titration to 80 mg with no adverse impact on asthma control.

Targeting the small airways asthma phenotype: if we can reach it, should we treat it?

OBJECTIVE

To review the available methods of evaluating the small airways disease in asthma and the therapeutic strategies to achieve better control using emerging extrafine particle inhaler technologies.

DATA SOURCES

The PubMed, MEDLINE (Ebsco), Scirus, Scopus, and Google Scholar databases were all scanned with Cross-search using the following keywords: asthma, small airways, hydrofluoroalkane 134a, extrafine particle, inhaled corticosteroid, long-acting β-agonist, spirometry, impulse oscillometry, nitrogen washout, exhaled nitric oxide, airway hyperresponsiveness, and adrenal suppression.

STUDY SELECTION

Key clinical studies considered to being relevant to the topic under review were evaluated.

RESULTS

There is an unmet need in current asthma guidelines for those individuals who exhibit the small airways asthma phenotype with a preserved forced expiratory volume in 1 second but abnormal forced midexpiratory flow and peripheral airway resistance, which tends to be associated with poorer control. Extrafine hydrofluoroalkane solution formulations of inhaled corticosteroid either alone or in combination with long-acting β-agonist may improve small airways outcomes and associated control.

CONCLUSION

From a pragmatic perspective, it makes sense to try to deliver asthma treatment to more of the lung to improve clinical outcomes, especially in patients who exhibit the small airways asthma phenotype.

Reference values of impulse oscillometric lung function indices in adults of advanced age

Background

Impulse oscillometry (IOS) is a non-demanding lung function test. Its diagnostic use may be particularly useful in patients of advanced age with physical or mental limitations unable to perform spirometry. Only few reference equations are available for Caucasians, none of them covering the old age. Here, we provide reference equations up to advanced age and compare them with currently available equations.

Methods

IOS was performed in a population-based sample of 1990 subjects, aged 45–91 years, from KORA cohorts (Augsburg, Germany). From those, 397 never-smoking, lung healthy subjects with normal spirometry were identified and sex-specific quantile regression models with age, height and body weight as predictors for respiratory system impedance, resistance, reactance, and other parameters of IOS applied.

Results

Women (n = 243) showed higher resistance values than men (n = 154), while reactance at low frequencies (up to 20 Hz) was lower (p<0.05). A significant age dependency was observed for the difference between resistance values at 5 Hz and 20 Hz (R5–R20), the integrated area of low-frequency reactance (AX), and resonant frequency (Fres) in both sexes whereas reactance at 5 Hz (X5) was age dependent only in females. In the healthy subjects (n = 397), mean differences between observed values and predictions for resistance (5 Hz and 20 Hz) and reactance (5 Hz) ranged between −1% and 5% when using the present model. In contrast, differences based on the currently applied equations (Vogel & Smidt 1994) ranged between −34% and 76%. Regarding our equations the indices were beyond the limits of normal in 8.1% to 18.6% of the entire KORA cohort (n = 1990), and in 0.7% to 9.4% with the currently applied equations.

Conclusions

Our study provides up-to-date reference equations for IOS in Caucasians aged 45 to 85 years. We suggest the use of the present equations particularly in advanced age in order to detect airway dysfunction.