The DS-14 questionnaire: psychometric characteristics and utility in patients with obstructive sleep apnea

Little is known about type D personality in patients with obstructive sleep apnea (OSA). The DS-14 questionnaire is the standard tool to assess this personality type, but it has not been properly validated in patients with OSA, nor has it been correlated with clinical features in these patients.

PURPOSE

To determine the internal consistency and test-retest reliability of the DS-14 questionnaire, as well as the prevalence of type D personality in the overall OSA sample and subgroups. We assessed the influence of type D on perceived symptoms and its congruence with self-reported measures of personality, depression, fatigue, anxiety, quality of life, and quality of sleep.

METHODS

Patients with OSA completed the DS-14 questionnaire, Big Five Inventory-2 questionnaire, Hospital Anxiety and Depression Scale, SF-36 Health Survey Questionnaire, Epworth Sleepiness Scale and Stanford Sleepiness Scale, Pittsburgh Sleep Quality Index and Insomnia Severity Index, Fatigue Assessment Scale, and Checklist Individual Strength. After 1 month, the DS-14 questionnaire was repeated.

RESULTS

The overall prevalence of type D personality was 32%. Internal consistency (negative affectivity: α = 0.880, social inhibition: α = 0.851) and diagnostic test-retest reliability (kappa value = 0.664) of the DS-14 questionnaire were high. Significantly more symptoms of anxiety, depression, poor sleep quality, fatigue, and a worse health perception were found in OSA with type D. Neither OSA severity nor REM predominance altered these observations.

CONCLUSION

The DS-14 questionnaire showed excellent psychometric properties in patients with OSA. The prevalence of type D personality in patients with OSA was higher than in the general population. The presence of type D personality was associated with higher symptom burden.

Getting the Most out of Spirometry: A Tool to Guide Dry Powder Inhaler Use

<b><i>Background:</i></b> Dry powder inhaler (DPI) use requires sufficient peak inspiratory flow over the DPI internal resistance (PIF_R). <b><i>Objectives:</i></b> We examined whether spirometric peak inspiratory flow (PIF_spiro) could serve to predict PIF_R in patients with obstructive lung disease. <b><i>Method:</i></b> Thirty healthy nonsmokers and 140 stable outpatients (70 COPD, 70 asthma) performed spirometry according to the 2019 ERS/ATS spirometry update, yielding PIF_spiro. Using a PIF_R measurement device with varying orifices, all subjects’ PIF_R values were recorded for 5 predefined resistance levels, characterized by 5 orifice cross sections (S_R). A test group including all healthy subjects, 30 of the asthma, and 30 of the COPD patients was used to establish the relationship between PIF_R and both PIF_spiro and S_R by multiple regression. A validation group including the remaining 40 asthma and 40 COPD patients, served to verify whether their predicted PIF_R value corresponded to the measured PIF_R for each resistance level. <b><i>Results:</i></b> The asthma (FEV₁ = 78 ± 17 [SD] %pred) and COPD (FEV₁ = 46 ± 17 [SD] %pred) patients under study had varying airway obstruction. In the test group, PIF_R could be predicted by ln[PIF_spiro] (<i>p</i> &#x3c; 0.0001), S_R (<i>p</i> &#x3c; 0.0001), and S_R² (<i>p</i> = 0.006), with an adjusted <i>R</i>² = 0.71. In the validation group, estimated PIF_R did not significantly differ from measured PIF_R (<i>p</i> &#x3e; 0.05 for the 5 resistance levels). <b><i>Conclusions:</i></b> We propose a simple method to predict PIF_R for a range of common DPI resistances, based on the device characteristics and on the patient’s characteristics reflected in PIF_spiro. As such, routine spirometry can serve to estimate a patient’s specific PIF_R without the need for additional testing.

Not a wild goose chase: long-lasting MRSA negative status following eradication therapy for chronic MRSA infection in patients with cystic fibrosis

OBJECTIVES

Prevalence of MRSA in patients with CF has risen over the past decades, and chronic infection with MRSA is associated with worse outcome in this patient group.

METHODS

This retrospective observational study investigated long-term eradication rate in pediatric and adult CF patients with chronic MRSA infection, using a 6-month eradication regimen containing 2 oral antibiotics, combined with topical decolonisation measures. Respiratory tract cultures were performed at least every three months, from the first MRSA-positive culture onwards.

RESULTS

A total of 24 patients with chronic MRSA infection were identified from our CF patient registry, of which 13 patients underwent an eradication attempt. The regimen consisted of 2 oral antibiotics: a combination of rifampicin, fusidic acid, clindamycin and co-trimoxazol, based on the sensitivity pattern of the MRSA strain. At the end of the study period (median 8.2 years), 12 out of 13 patients (92%) were MRSA negative. None of the patients interrupted treatment due to side-effects.

CONCLUSIONS

Eradication of chronic MRSA infection is feasible, well-tolerated and highly successful, and can offer a long-lasting MRSA-negative status, obviating the need for patient segregation.

Fractal analysis reveals functional unit of ventilation in the lung

Ventilation is inhomogeneous in the lungs across species. It has been hypothesized that ventilation inhomogeneity is largely determined by the design of the airway branching network. Because exchange of gases at the alveolar barrier is more efficient when gas concentrations are evenly distributed at subacinar length scales, it is assumed that a 'functional unit' of ventilation exists within the lung periphery, where gas concentration becomes uniform. On the other hand, because the morphology of pulmonary airways and alveoli, and the distribution of inhaled fluorescent particles show self-similar fractal properties over a wide range of length scales, it has been predicted that fractal dimension of ventilation approaches unity within an internally homogeneous functional unit of ventilation. However, the existence of such a functional unit has never been demonstrated experimentally due to lack of in situ gas concentration measurements of sufficient spatial resolution in the periphery of a complex bifurcating network. Here, using energy-subtractive synchrotron radiation tomography, we measured the distribution of an inert gas (Xe) in the in vivo rabbit lung during Xe wash-in breathing manoeuvres. The effects of convective flow rate, diffusion and cardiac motion were also assessed. Fractal analysis of resulting gas concentration and tissue density maps revealed that fractal dimension was always smaller for Xe than for tissue density, and that only for the gas, a length scale existed where fractal dimension approached unity. The length scale where this occurred was seen to correspond to that of a rabbit acinus, the terminal structure comprising only alveolated airways. KEY POINTS: Gas ventilation is inhomogeneous in the lung of many species. However, it is not known down to what length scales this inhomogeneity persists. It is generally assumed that ventilation becomes homogeneous at subacinar length scales, beyond the spatial resolution of commonly available imaging techniques, hence this has not been demonstrated experimentally. Here we measured the distribution of inhaled Xe gas in the rabbit lung using synchrotron radiation energy-subtractive imaging and used fractal analysis to show that ventilation becomes internally uniform within regions about the size of rabbit lung acini.

Peripheral lung effect of elexacaftor/tezacaftor/ivacaftor in adult cystic fibrosis

Despite being an important patient group, adult cystic fibrosis patients with an FEV₁ below 40%predicted have been excluded from clinical trials with elexacaftor/tezacaftor/ivacaftor. We conducted a real-life 3 months follow-up study in 14 adult CF patients (median FEV₁ 34%predicted) demonstrating significant treatment effects in terms of FEV₁ (an increase of 12%predicted at 4 weeks, remaining stable thereafter). Corresponding decreases in lung clearance index LCI (by 31%predicted, down from baseline 247%predicted) and ventilation heterogeneity in the acinar compartment (Sacin) (by 411%predicted, down from baseline 798%predicted) suggest a distinct peripheral lung effect. One patient had intermittent treatment interruptions because of drug-induced liver injury. Our real-life data confirm that treatment with elexacaftor/tezacaftor/ivacaftor is effective in severely obstructive patients, and this is the first study to show time evolution of ventilation distribution improvement, pointing to the peripheral lung as the main site of treatment effect.

Peak In- and Expiratory Flow Revisited: Reliability and Reference Values in Adults

BACKGROUND

While peak in- and expiratory flow rates offer valuable information for diagnosis and monitoring in respiratory disease, these indices are usually considered too variable to be routinely used for quantification in clinical practice.

OBJECTIVES

The aim of the study was to obtain reproducible measurements of maximal inspiratory flow rates and to construct reference equations for peak in- and expiratory flows (PIF and PEF).

METHOD

With coaching for maximal effort, 187 healthy Caucasian subjects (20-80 years) performed at least 3 combined forced inspiratory and expiratory manoeuvres, until at least 2 peak inspiratory flow measurements were within 10% of each other. The effect on PIF preceded by a slow expiration instead of a forced expiration and PIF repeatability over 3 different days was also investigated in subgroups. Reference values and limits of normal for PIF, mid-inspiratory flow, and PEF were obtained according to the Lambda-Mu-Sigma statistical method.

RESULTS

A valid PIF could be obtained within 3.3 ± 0.6(SD) attempts, resulting in an overall within-test PIF variability of 4.6 ± 3.2(SD)%. A slow instead of a forced expiration prior to forced inspiration resulted in a significant (p < 0.001) but small PIF increase (2.5% on average). Intraclass correlation coefficient for between-day PIF was 0.981 (95% CI: 0.960-0.992). Over the entire age range, inter-subject PIF variability was smaller than in previous reports, and PIF could be predicted based on its determinants gender, age, and height (r2 = 0.53).

CONCLUSIONS

When adhering to similar criteria for the measurement of effort-dependent portions of inspiratory and expiratory flow-volume curves, performed according to current ATS/ERS standards, it is possible to obtain reproducible PIF and PEF values for use in routine clinical practice.

Clinical status and lung function 10 weeks after severe SARS-CoV-2 infection

INTRODUCTION

Since studies about clinical status after COVID-19 are scarce, we conducted a cross sectional study with assessment of residual symptoms, lung function and chest CT.

MATERIALS AND METHODS

During an outpatient follow-up visit, chest CT, pulmonary function and COVID-19 related symptoms were assessed approximately 10 weeks after diagnosis. Demographics, baseline (time of diagnosis) CT score and blood results were collected from patient files. Association between lung function and clinical characteristics (baseline), blood markers (baseline), chest CT (baseline and follow-up) and symptom score (followup) was analysed. Mann-Whitney U tests and Chi squared tests were used for statistical comparison between subgroups with and without restriction.

RESULTS AND DISCUSSION

Two hundred-twenty subjects were evaluated at a median follow-up of 74±12 (SD) days. Median symptom and median CT score at follow-up were 1(IQR=0- 2) and 2(IQR=0-6) respectively. Forty-six percent of patients had normal lung function, while TLC and TLCO below the lower limit of normal were observed in 38% and 22% of subjects respectively. This restrictive pulmonary impairment was associated with length of hospital stay (8 vs 6 days; p=0.003), admission to the intensive care unit (27% vs 13%;p=0.009), and invasive mechanical ventilation (10% vs 0.7%;p=0.001), but not with symptom score or CT score at baseline and follow-up.

CONCLUSIONS

Fifty-four percent of COVID-19 survivors had abnormal lung function 10 weeks after diagnosis. Restriction was the most prevalent pulmonary function, with the more critically ill patients being more prone to this condition. Yet, restriction could not be linked with abnormal imaging results or residual symptoms.

Inhaled aerosol dose distribution between proximal bronchi and lung periphery

Modern inhaled drug discovery programs assess dose delivery to proximal and distal airways using rudimentary imaging indices, where relative deposition is estimated by generically defined 'central' and 'peripheral' lung regions. Utilizing recent data linking the proximal airway topology to a characteristic pattern of aerosol lung deposition, we provide a direct measure of dose distribution between the proximal bronchi and the distal lung. We analyzed scintigraphic lung images of twelve asthma patients following inhalation of 1.5-, 3- and 6-µm monodisperse drug particles at breathing flows of 30- and 60-L/min. We explicitly used the central hot-spots associated with each patient's specific bronchial topology to obtain a direct measure of aerosol deposition in the proximal bronchi, rather than applying standard templates of lung boundaries. Maximum deposition in the central bronchi (as % of lung deposition) was 52 ± 10(SD)% (6 µm;60 L/min). Minimum central deposition was 17 ± 2(SD)% (1.5 µm;30 L/min) where the 83% aerosol 'escaping' deposition in the central bronchi reached 75 ± 17(SD)% of the lung area that could be reached by Krypton gas. For all particle sizes, hot-spots appeared in the same patient-specific central airway location, with greatest intensity at 60 L/min. For a range of respirable aerosol sizes and breathing flows, we have quantified deposited dose in the proximal bronchi and their distal lung reach, constituting a platform to support therapeutic inhaled aerosol drug development.

Pulmonary function patterns and their association with genotype and phenotype in adult cystic fibrosis patients

Background: While cystic fibrosis (CF) lung disease is generally considered to be an obstructive disorder, other pulmonary function patterns (PFP) may occur. Furthermore, little is known about possible associations between PFP and genotype or phenotypical characteristics. Methods: Cross-sectional study including CF patients aged 16 years or more, identifying different PFP and exploring associations between PFP and genotype or phenotypical characteristics. Results: Obstructive PFP was most prevalent in our population (n = 80), comprising obstructive lung disease (62.5%), small airway (obstructive) disease (11.2%), and mixed obstructive-restrictive disorder (1.3%). However, one in four adult CF patients did not show any obstruction at all: normal (13.7%) or restrictive (8.8%) lung disease and isolated diffusion disorder (2.5%). Obstructive PFP was associated with a greater proportion of CF-related diabetes mellitus (CFRD) (P = 0.04), Pseudomonas aeruginosa colonization (P = 0.02) and frequent exacerbators (P = 0.04). We observed no association between PFP and genotype. Conclusions: Obstructive PFP remains the most common pulmonary function pattern in adult CF and is associated with CFRD, Pseudomonas aeruginosa colonization and frequent exacerbators.

Pulmonary function changes following helical tomotherapy in patients with inoperable, locally advanced non-small cell lung cancer

PURPOSE

To evaluate alterations in pulmonary function indices after helical tomotherapy and explore potential associations with biologically corrected dosimetric parameters.

PATIENTS AND METHODS

In 64 patients with inoperable locally advanced non-small cell lung cancer, pulmonary function tests before and within 6 months after radiotherapy were evaluated retrospectively. In the case of concurrent chemotherapy a total dose of 67.2 Gy was delivered, otherwise 70.5 Gy was provided. In 44 patients, late pulmonary function changes (≥6 months after radiotherapy) could also be assessed.

RESULTS

In the entire patient group, there were significant declines in forced expiratory volume in 1s (FEV₁) (average change -4.1% predicted; P = 0.007), in forced vital capacity (FVC) (-4.9% predicted; P = 0.002), total lung capacity (TLC) (-5.8% predicted; P = 0.0016) and DL_CO (diffusing capacity of the lung for carbon monoxide corrected for hemoglobin level) (-8.6% predicted; P < 0.001) during the first 6 months. Corresponding FEV₁, FVC, TLC and DL_CO declines in the subgroup with late measurements (after 11.3 months on average) were -5.7, -7.4, -7.0, -9.8% predicted. A multivariate analysis including V_5 Gy, V_10 Gy, V_20 Gy, V_40 Gy, V_60 Gy, mean lung dose (MLD), gross tumor volume (GTV) and planning target volume (PTV) as potential covariates showed that GTV was the most consistent contributor, being significant for ∆FEV₁ (P = 0.003), ∆FVC (P = 0.003), ∆TLC (P = 0.001) and ∆DL_CO (P = 0.01). V_5 Gy or V_10 Gy did not contribute to any of the lung function changes.

CONCLUSIONS

The decline in pulmonary function indices after helical tomotherapy was of similar magnitude to that observed in studies reporting the effect of conformal radiotherapy on lung function. Diffusion capacity was the parameter showing the largest decrease following radiation therapy as compared to baseline and correlated with gross tumor volume. None of the alterations in pulmonary function tests were associated with the lung volume receiving low-dose radiation.

Substance deposition assessment in obstructed pulmonary system through numerical characterization of airflow and inhaled particles attributes

BACKGROUND

Chronic obstructive pulmonary disease (COPD) and asthma are considered as the two most widespread obstructive lung diseases, whereas they affect more than 500 million people worldwide. Unfortunately, the requirement for detailed geometric models of the lungs in combination with the increased computational resources needed for the simulation of the breathing did not allow great progress to be made in the past for the better understanding of inflammatory diseases of the airways through detailed modelling approaches. In this context, computational fluid dynamics (CFD) simulations accompanied by fluid particle tracing (FPT) analysis of the inhaled ambient particles are deemed critical for lung function assessment. Also they enable the understanding of particle depositions on the airways of patients, since these accumulations may affect or lead to inflammations. In this direction, the current study conducts an initial investigation for the better comprehension of particle deposition within the lungs. More specifically, accurate models of the airways obstructions that relate to pulmonary disease are developed and a thorough assessment of the airflow behavior together with identification of the effects of inhaled particle properties, such as size and density, is conducted. Our approach presents a first step towards an effective personalization of pulmonary treatment in regards to the geometric characteristics of the lungs and the in depth understanding of airflows within the airways.

METHODS

A geometry processing technique involving contraction algorithms is established and used to employ the different respiratory arrangements associated with lung related diseases that exhibit airways obstructions. Apart from the normal lung case, two categories of obstructed cases are examined, i.e. models with obstructions in both lungs and models with narrowings in the right lung only. Precise assumptions regarding airflow and deposition fraction (DF) over various sections of the lungs are drawn by simulating these distinct incidents through the finite volume method (FVM) and particularly the CFD and FPT algorithms. Moreover, a detailed parametric analysis clarifies the effects of the particles size and density in terms of regional deposition upon several parts of the pulmonary system. In this manner, the deposition pattern of various substances can be assessed.

RESULTS

For the specific case of the unobstructed lung model most particles are detected on the right lung (48.56% of total, when the air flowrate is 12.6 L/min), a fact that is also true when obstructions arise symmetrically in both lungs (51.45% of total, when the air flowrate is 6.06 L/min and obstructions occur after the second generation). In contrast, when narrowings are developed on the right lung only, most particles are pushed on the left section (68.22% of total, when the air flowrate is 11.2 L/min) indicating that inhaled medication is generally deposited away from the areas of inflammation. This observation is useful when designing medical treatment of lung diseases. Furthermore, particles with diameters from 1 μm to 10 μm are shown to be mainly deposited on the lower airways, whereas particles with diameters of 20 μm and 30 μm are mostly accumulated in the upper airways. As a result, the current analysis indicates increased DF levels in the upper airways when the particle diameter is enlarged. Additionally, when the particles density increases from 1000 Kg/m³ to 2000 Kg/m³, the DF is enhanced on every generation and for all cases investigated herein. The results obtained by our simulations provide an accurate and quantitative estimation of all important parameters involved in lung modeling.

CONCLUSIONS

The treatment of respiratory diseases with inhaled medical substances can be advanced by the clinical use of accurate CFD and FPT simulations and specifically by evaluating the deposition of inhaled particles in a regional oriented perspective in regards to different particle sizes and particle densities. Since a drug with specific characteristics (i.e. particle size and density) exhibits maximum deposition on particular lung areas, the current study provides initial indications to a qualified physician for proper selection of medication.

The quantitative link of lung clearance index to bronchial segments affected by bronchiectasis

In adult patients with cystic fibrosis (CF), the lung clearance index (LCI) derived from the multiple breath washout relates to both acinar and conductive ventilation heterogeneity. The latter component predicts an association between LCI and the number of bronchial segments affected by bronchiectasis. Here, we experimentally demonstrated this association in patients with CF, and also examined an ancillary group of patients with non-CF bronchiectasis. We conclude that lung disease severity in terms of number of bronchial segments results in an associated LCI increase, likely constituting a portion of LCI that cannot be reversed by treatment in patients with CF lung disease.

Mild Lung Restriction in Breast Cancer Patients After Hypofractionated and Conventional Radiation Therapy: A 3-Year Follow-Up

PURPOSE

To assess the effect of radiation therapy on lung function over the course of 3 years.

METHODS AND MATERIALS

Evolution of restrictive and obstructive lung function parameters was investigated in 108 breast cancer participants in a randomized, controlled trial comparing conventional radiation therapy (CR) and hypofractionated tomotherapy (TT) (age at inclusion ranging 32-81 years). Spirometry, plethysmography, and hemoglobin-corrected diffusing capacity were assessed at baseline and after 3 months and 1, 2, and 3 years. Natural aging was accounted for by considering all lung function parameters in terms of percent predicted values using the most recent reference values for women aged up to 80 years.

RESULTS

In the patients with negligible history of respiratory disease or smoking (n=77), the greatest rate of functional decline was observed during the initial 3 months, this acute decrease being more marked in the CR versus the TT arm. During the remainder of the 3-year follow-up period, values (in terms of percent predicted) were maintained (diffusing capacity) or continued to decline at a slower rate (forced vital capacity). However, the average decline of the restrictive lung function parameters over a 3-year period did not exceed 9% predicted in either the TT or the CR arm. Obstructive lung function parameters remained unaffected throughout. Including also the 31 patients with a history of respiratory disease or more than 10 pack-years showed a very similar restrictive pattern.

CONCLUSIONS

In women with breast cancer, both conventional radiation therapy and hypofractionated tomotherapy induce small but consistent restrictive lung patterns over the course of a 3-year period, irrespective of baseline respiratory status or smoking history. The fastest rate of lung function decline generally occurred in the first 3 months.

Transfer factor, lung volumes, resistance and ventilation distribution in healthy adults

Monitoring of chronic lung disease requires reference values of lung function indices, including putative markers of small airway function, spanning a wide age range.We measured spirometry, transfer factor of the lung for carbon monoxide (TLCO), static lung volume, resistance and ventilation distribution in a healthy population, studying at least 20 subjects per sex and per decade between the ages of 20 and 80 years.With respect to the Global Lung Function Initiative reference data, our subjects had average z-scores for forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC of -0.12, 0.04 and -0.32, respectively. Reference equations were obtained which could account for a potential dependence of index variability on age and height. This was done for (but not limited to) indices that are pertinent to asthma and chronic obstructive pulmonary disease studies: forced expired volume in 6 s, forced expiratory flow, TLCO, specific airway conductance, residual volume (RV)/total lung capacity (TLC), and ventilation heterogeneity in acinar and conductive lung zones.Deterioration in acinar ventilation heterogeneity and lung clearance index with age were more marked beyond 60 years, and conductive ventilation heterogeneity showed the greatest increase in variability with age. The most clinically relevant deviation from published reference values concerned RV/TLC values, which were considerably smaller than American Thoracic Society/European Respiratory Society-endorsed reference values.

Increase in ventilated air spaces after eradication of chronic methicillin-resistant Staphylococcus aureus infection in cystic fibrosis patients

Effective microbiogical eradication of methicillin-resistant Staphylococcus aureus (MRSA) in patients with cystic fibrosis (CF) can be obtained, but its effect is not always clear-cut in terms of spirometric indices. The aim of this observational prospective cohort study was to study the potential effect of eradication of chronic MRSA infection on lung function including ventilation distribution. Six CF patients, chronically colonized with MRSA (median age: 21 years (range 14-46); median FEV1: 76 (95%CI 58-98)%pred) were successfully eradicated using oral rifampicin and fusidic acid in combination with topical decolonization measures. Lung function and multiple breath washout test were performed at the start and at the end of the eradication protocol and after an average follow-up period of 7·5±1·5(SD) months. One patient cultured MRSA again 4 months after successful eradication. All patients reported reduced sputum production and viscosity. By the end of the follow-up period, there was an increase in ventilated FRCMBW and no change in plethysmographic FRCPL. This resulted in a significant decrease of trapped air by half a litre (from 579 to 40 ml; P = 0·013). Lung clearance index (LCI) also showed a small but significant decrease (from 7·2 to 6·7; P = 0·014) after eradication of MRSA. We conclude that MRSA eradication can be successful, also in terms of recruitment of previously unventilated air spaces, potentially due to reduced sputum production and/or viscosity.

Bronchiolitis obliterans syndrome leads to a functional deterioration of the acinus post lung transplant

Bronchiolitis obliterans syndrome (BOS) limits long-term survival of lung transplant recipients, and airflow obstruction in these patients likely originates in the small airways. 61 double lung transplant recipients performed multiple breath nitrogen washouts to obtain indices of acinar and conductive ventilation heterogeneity (Sacin, Scond). There was a significant association of BOS status with Sacin (Kruskal-Wallis; p<0.001) but not with Scond (p=0.1). These results demonstrate that it is the structural alteration of the terminal bronchioles, generating ventilation heterogeneity at the level of the diffusion front, and not the bronchioles located more proximally, that is driving the airflow obstruction that determines BOS status.

Peripheral lung function in patients with stable and unstable asthma

BACKGROUND

Exacerbations of asthma are thought to be caused by airflow obstruction resulting from airway inflammation, bronchospasm, and mucus plugging. Histologic evidence suggests the small airways, including acinar air spaces, are involved; however, this has not been corroborated in vivo by measurements of peripheral small-airway function.

OBJECTIVE

We sought to determine whether asthma severity is linked to small-airway function, particularly in patients with acute severe asthma.

METHODS

Eighteen subjects admitted for an asthma exacerbation underwent lung function testing, including measures of acinar ventilation heterogeneity (S(acin)) and conductive ventilation heterogeneity (S(cond)) using the multiple-breath nitrogen washout. Treatment requirement was defined according to Global Initiative for Asthma scores. Data were compared with those obtained in 19 patients with stable asthma.

RESULTS

For the asthma exacerbation group, the median FEV1 was 59% of predicted value (95% CI, 45% to 75% of predicted value), the median S(cond) value was 185% of predicted value (95% CI, 119% to 245% of predicted value), and the median S(acin) value was 225% of predicted value (95% CI, 143% to 392% of predicted value). FEV1 (percent predicted) was correlated with S(acin) (percent predicted) values (Spearman rho = -0.67, P = .006) but not with S(cond) (percent predicted) values (P > .1). The Global Initiative for Asthma score was significantly related to S(acin) (percent predicted) (Spearman rho = 0.59, P = .016) but not to S(cond) (percent predicted) values (P > .1). The unstable group was characterized by considerably lower forced vital capacity (P < .001) and higher S(cond) (P = .001) values than the unstable group. In a subgroup of 11 unstable patients who could be reviewed after 4 weeks, FEV1, forced vital capacity, S(acin), and S(cond) values showed marked improvements.

CONCLUSION

Our findings suggest that unstable asthma is characterized by a combined abnormality in the acinar and conductive lung zones, both of which are partly reversible. Functional abnormality in the acinar lung zone in particular showed a direct correlation with airflow obstruction and treatment requirement in patients with acute severe asthma.

Effect of methacholine on peripheral lung mechanics and ventilation heterogeneity in asthma

The forced oscillation technique (FOT) and multiple-breath nitrogen washout (MBNW) are noninvasive tests that are potentially sensitive to peripheral airways, with MBNW indexes being especially sensitive to heterogeneous changes in ventilation. The objective was to study methacholine-induced changes in the lung periphery of asthmatic patients and determine how changes in FOT variables of respiratory system reactance (Xrs) and resistance (Rrs) and frequency dependence of resistance (Rrs5-Rrs19) can be linked to changes in ventilation heterogeneity. The contributions of air trapping and airway closure, as extreme forms of heterogeneity, were also investigated. Xrs5, Rrs5, Rrs19, Rrs5-Rrs19, and inspiratory capacity (IC) were calculated from the FOT. Ventilation heterogeneity in acinar and conducting airways, and trapped gas (percent volume of trapped gas at functional residual capacity/vital capacity), were calculated from the MBNW. Measurements were repeated following methacholine. Methacholine-induced airway closure (percent change in forced vital capacity) and hyperinflation (change in IC) were also recorded. In 40 mild to moderate asthmatic patients, increase in Xrs5 after methacholine was predicted by increases in ventilation heterogeneity in acinar airways and forced vital capacity ( r2 = 0.37, P < 0.001), but had no correlation with ventilation heterogeneity in conducting airway increase or IC decrease. Increases in Rrs5 and Rrs5-Rrs19 after methacholine were not correlated with increases in ventilation heterogeneity, trapped gas, hyperinflation, or airway closure. Increased reactance in asthmatic patients after methacholine was indicative of heterogeneous changes in the lung periphery and airway closure. By contrast, increases in resistance and frequency dependence of resistance were not related to ventilation heterogeneity or airway closure and were more indicative of changes in central airway caliber than of heterogeneity.

Consensus statement for inert gas washout measurement using multiple- and single- breath tests

Inert gas washout tests, performed using the single- or multiple-breath washout technique, were first described over 60 years ago. As measures of ventilation distribution inhomogeneity, they offer complementary information to standard lung function tests, such as spirometry, as well as improved feasibility across wider age ranges and improved sensitivity in the detection of early lung damage. These benefits have led to a resurgence of interest in these techniques from manufacturers, clinicians and researchers, yet detailed guidelines for washout equipment specifications, test performance and analysis are lacking. This manuscript provides recommendations about these aspects, applicable to both the paediatric and adult testing environment, whilst outlining the important principles that are essential for the reader to understand. These recommendations are evidence based, where possible, but in many places represent expert opinion from a working group with a large collective experience in the techniques discussed. Finally, the important issues that remain unanswered are highlighted. By addressing these important issues and directing future research, the hope is to facilitate the incorporation of these promising tests into routine clinical practice.