End-expiratory lung volume remains stable during N2 MBW in healthy sleeping infants

We have previously shown that functional residual capacity (FRC) and lung clearance index were significantly greater in sleeping healthy infants when measured by N2 (nitrogen) washout using 100% O2 (oxygen) versus 4% SF6 (sulfur hexafluoride) washout using air. Following 100% O2 exposure, tidal volumes decreased by over 30%, while end-expiratory lung volume (EELV, i.e., FRC) rose markedly based on ultrasonic flow meter assessments. In the present study to investigate the mechanism behind the observed changes, N2 MBW was performed in 10 separate healthy full-term spontaneously sleeping infants, mean (range) 26 (18-31) weeks, with simultaneous EELV monitoring (respiratory inductance plethysmography, RIP) and oxygen uptake (V´O2 ) assessment during prephase air breathing, during N2 washout by exposure to 100% O2 , and subsequently during air breathing. While flow meter signals suggested a rise in ELLV by mean (SD) 26 (9) ml over the washout period, RIP signals demonstrated no EELV change. V'O2 /FRC ratio during air breathing was mean (SD) 0.43 (0.08)/min, approximately seven times higher than that calculated from adult data. We propose that our previously reported flow meter-based overestimation of EELV was in fact a physiological artifact caused by rapid and marked movement of O2 across the alveolar capillary membrane into the blood and tissue during 100% O2 exposure, without concomitant transfer of N2 to the same degree in the opposite direction. This may be driven by the high observed O2 consumption and resulting cardiac output encountered in infancy. Furthermore, the low resting lung volume in infancy may make this error in lung volume determination by N2 washout relatively large.

The effect of pectus excavatum deformity on lung volume: fact or myth?

BACKGROUND AND PURPOSE

Most of the previous studies evaluating lung volume of pectus excavatum (PE) patients were based on spirometric measurements. We aimed to calculate lung volume of patients with PE and compare them with lung volume of patients without chest wall deformity using CT volumetry.

METHODS

After institutional review board approval, preoperative chest CT of PE patients who underwent minimal invasive procedure between January 2012 and February 2018, were evaluated retrospectively. As a control group, age and sex matched patients who underwent chest CT scan in the same period were enrolled. Total, right and left lung volumes were calculated using an automated software. Haller indexes were measured for both groups. Lung volumes and Haller indexes compared between the two groups. We also compared left and right lung volumes in both groups. We evaluated whether there is a correlation across the Haller index and total lung volume.

RESULTS

Total, right and left lung volumes were not statistically different between the two groups. While left lung volumes were significantly smaller in PE group (p = 0.041), there was no significant difference between the left and right lung volume in the control group (p = 0.12). Haller index and total lung volume showed no significant correlation between patients with the same age and gender (p = 0.14, R = -0.3).

CONCLUSIONS

PE deformity does not reduce lung volume when compared to age and sex matched control group. Quantitative CT volumetric evaluation of lung gives valuable data about lung volume.

Chest Movement and Respiratory Volume both Contribute to Thoracic Bioimpedance during Loaded Breathing

Bioimpedance has been widely studied as alternative to respiratory monitoring methods because of its linear relationship with respiratory volume during normal breathing. However, other body tissues and fluids contribute to the bioimpedance measurement. The objective of this study is to investigate the relevance of chest movement in thoracic bioimpedance contributions to evaluate the applicability of bioimpedance for respiratory monitoring. We measured airflow, bioimpedance at four electrode configurations and thoracic accelerometer data in 10 healthy subjects during inspiratory loading. This protocol permitted us to study the contributions during different levels of inspiratory muscle activity. We used chest movement and volume signals to characterize the bioimpedance signal using linear mixed-effect models and neural networks for each subject and level of muscle activity. The performance was evaluated using the Mean Average Percentage Errors for each respiratory cycle. The lowest errors corresponded to the combination of chest movement and volume for both linear models and neural networks. Particularly, neural networks presented lower errors (median below 4.29%). At high levels of muscle activity, the differences in model performance indicated an increased contribution of chest movement to the bioimpedance signal. Accordingly, chest movement contributed substantially to bioimpedance measurement and more notably at high muscle activity levels.

Total and Compartmental Chest Wall Volumes, Lung Function, and Respiratory Muscle Strength in Individuals with Abdominal Obesity: Effects of Body Positions

Background

Abdominal obesity is a chronic condition that can contribute to impairments in lung function, leading to increased risks for respiratory-related diseases. Body position is an important technique that effectively restores and increases lung function and chest wall volumes. The objective of the current study was to examine the effects of the body positions on total and compartmental chest wall volumes, lung function, and respiratory muscle strength in individuals with and without abdominal obesity.

Methods

Twenty obesity and twenty healthy males performed in four body position including sitting without and with back support, Fowler's, and supine positions. Each position was performed for five minutes. Chest wall volumes, lung function, and respiratory muscle strength were assessed in each position.

Results

Sitting without and with back support resulted in higher total and rib cage compartmental chest wall volumes, lung function, and inspiratory muscle strength than Fowler's and supine positions in both groups (p < 0.001). Abdominal obesity subjects had significantly less total and compartmental chest wall volumes and lung function across four body positions than healthy subjects (p < 0.001). Respiratory muscle strength in the obesity group was less than that in the healthy control group (p > 0.05).

Conclusions

This study provides new information regarding the effect of obesity and body position on chest wall volumes, lung function, and respiratory muscle strength. Among obesity individuals who are bedridden, sitting increases lung function, total and rib cage compartmental chest wall volumes, and inspiratory muscle strength-and would therefore likely to decrease the risk of respiratory-related disease-relative to Fowler's and supine positions.

Dynamic discriminant model for predicting respiratory distress at birth based on mass volume ratio in fetuses with congenital lung malformation

OBJECTIVES

The congenital lung malformation volume ratio (CVR) is a prenatal ultrasound measurement that parameterizes congenital lung malformation (CLM) size. The aims of this study were to use serial measurements to create estimated growth curves of fetal CVR for asymptomatic and symptomatic neonates with CLM and to investigate whether a discriminant prognostic model based on these measurements could predict accurately which fetuses with CLM will require invasive respiratory support at delivery and should therefore be delivered at a tertiary-care facility.

METHODS

This was a retrospective study of fetuses diagnosed prenatally with CLM at three tertiary-care children's hospitals between 2009 and 2016. Those with two or more sonographic measurements of CVR were included. Serial fetal CVR measurements were used to create estimated growth curves for neonates with and those without respiratory symptoms at delivery, defined as requiring invasive respiratory support for the first 24 h after delivery. A discriminant model based on serial CVR measurements was used to calculate the dynamic probability of the need for invasive respiratory support. The performance of this model overall and in preterm and term neonates was compared with those using maximum CVR thresholds of 1.0 and 1.6.

RESULTS

Of the 147 neonates meeting the inclusion criteria, 16 (10.9%) required postnatal invasive respiratory support. The estimated CVR growth curve models showed different growth trajectories for asymptomatic and symptomatic neonates, with significantly higher CVR in symptomatic neonates, and values peaking late in the second trimester at around 25 weeks' gestation in asymptomatic neonates. All prognostic methods had high accuracy for the prediction of the need for invasive respiratory support in term neonates, but the discriminant model had the best performance overall (area under the receiver-operating characteristics curve (AUC) = 0.88) and in the preterm population (AUC = 0.85).

CONCLUSIONS

The estimated CVR growth curves showed different growth patterns in asymptomatic and symptomatic neonates with CLM. The dynamic discriminant model performed well overall and particularly in neonates that were carried to term. Development of an externally validated clinical tool based on this analysis could be useful in determining the site of delivery for fetuses with CLM. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Fetal endoscopic tracheal occlusion reduces pulmonary hypertension in severe congenital diaphragmatic hernia

OBJECTIVE

Fetal endoscopic tracheal occlusion (FETO) is associated with increased perinatal survival and reduced need for extracorporeal membrane oxygenation (ECMO) in fetuses with severe congenital diaphragmatic hernia (CDH). This study evaluates the impact of FETO on the resolution of pulmonary hypertension (PH) in fetuses with isolated CDH.

METHODS

We reviewed retrospectively the medical records of all fetuses evaluated for CDH between January 2004 and July 2017 at a single institution. Fetuses with additional major structural or chromosomal abnormalities were excluded. CDH cases were classified retrospectively into mild, moderate and severe groups based on prenatal magnetic resonance imaging indices (observed-to-expected total fetal lung volume and percentage of intrathoracic liver herniation). Presence of PH was determined based on postnatal echocardiograms. Logistic regression analyses were performed to evaluate the relationship between FETO and resolution of PH by 1 year of age while controlling for side of the CDH, use of ECMO, gestational age at diagnosis, gestational age at delivery, fetal gender, sildenafil use at discharge and CDH severity. Resolution of PH by 1 year of age was compared between a cohort of fetuses with severe CDH that underwent FETO and a cohort that did not have the procedure (non-FETO). A subanalysis was performed restricting the analysis to isolated left CDH. Parametric and non-parametric tests were used for comparisons.

RESULTS

Of 257 CDH cases evaluated, 72% (n = 184) had no major structural or chromosomal anomalies of which 58% (n = 107) met the study inclusion criteria. The FETO cohort consisted of 19 CDH cases and the non-FETO cohort (n = 88) consisted of 31 (35%) mild, 32 (36%) moderate and 25 (28%) severe CDH cases. All infants with severe CDH, regardless of whether they underwent FETO, had evidence of neonatal PH. FETO (OR, 3.57; 95% CI, 1.05-12.10; P = 0.041) and ECMO (OR, 5.01; 95% CI, 2.10-11.96; P < 0.001) were independent predictors of resolution of PH by 1 year of age. A higher proportion of infants with severe CDH that underwent FETO had resolution of PH by 1 year after birth compared with infants with severe CDH in the non-FETO cohort (69% (11/16) vs 28% (7/25); P = 0.017). Similar results were observed when the analysis was restricted to cases with left-sided CDH (PH resolution in 69% (11/16) vs 28% (5/18); P = 0.032).

CONCLUSION

In infants with severe CDH, FETO and ECMO are independently associated with increased resolution of PH by 1 year of age. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Lung air trapping lowers respiratory arousal threshold and contributes to sleep apnea pathogenesis in COPD patients with overlap syndrome

STUDY OBJECTIVES

Overlap syndrome occurs when obstructive sleep apnea (OSA) and chronic obstructive pulmonary disorder (COPD) coexist in the same patient. Although several studies highlighted the importance of clinical phenotyping in OSA, the trait contribution to OSA pathogenesis in overlap syndrome has not been investigated. With this pilot study, we aimed to measure OSA determinants and their relationship with functional respiratory parameters in a sample of patients with overlap syndrome. In particular, we hypothesize that patients with COPD have in the low arousal threshold a major contributor for the development of OSA.

METHODS

Ten consecutive non-hypercapnic COPD patients (body mass index<35 kg/m²) suffering from overlap syndrome with no other relevant comorbidities underwent a phenotyping polysomnography. Traits were measured with CPAP dial-downs.

RESULTS

Arousal threshold was found to be inversely associated to functional measures of lung air trapping and static hyperinflation. Particularly, correlations with residual volume (r² = 0.49, p =  0.024) and residual volume to total lung capacity ratio (r² = 0.48, p =  0.026) were evident. Only 20% of patients showed a high upper airway passive collapsibility as single pathological trait. In contrast, among those patients with multiple altered traits (6 out of 10), all had an elevated loop gain and 4 (∼65%) a low arousal threshold.

CONCLUSIONS

High loop gain and particularly low arousal threshold seem important contributors to OSA pathogenesis and severity in patients with COPD. Recognizing in COPD patients these features as key traits may open avenues for personalized medicine in the field of overlap syndrome.

Level-Set Segmentation-Based Respiratory Volume Estimation Using a Depth Camera

In this paper, a method is proposed to measure human respiratory volume using a depth camera. The level-set segmentation method, combined with spatial and temporal information, was used to measure respiratory volume accurately. The shape of the human chest wall was used as spatial information. As temporal information, the segmentation result from the previous frame in the time-aligned depth image was used. The results of the proposed method were verified using a ventilator. The proposed method was also compared with other level-set methods. The result showed that the mean tidal volume error of the proposed method was 8.41% compared to the actual tidal volume. This was calculated to have less error than with two other methods: the level-set method with spatial information (14.34%) and the level-set method with temporal information (10.93%). The difference between these methods of tidal volume error was statistically significant \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\text{(p}} < {\text{0.0001}})$\end{document}. The intra-class correlation coefficient (ICC) of the respiratory volume waveform measured by a ventilator and by the proposed method was 0.893 on an average, while the ICC between the ventilator and the other methods were 0.837 and 0.879 on an average.

Science reflects history as society influences science: brief history of "race," "race correction," and the spirometer

Spirometers are used globally to diagnose respiratory diseases, and most commercially available spirometers "correct" for race. "Race correction" is built into the software of spirometers. To evaluate pulmonary function and to make recordings, the operator must enter the subject's race. In fact, the Joint Working Party of the American Thoracic Society/European Respiratory Society recommends the use of race- and ethnic-specific reference values. In the United States, spirometers apply correction factors of 10-15% for individuals labeled "Black" and 4-6% for people labeled "Asian." Thus race is purported to be a biologically important and scientifically valid category. However, history suggests that race corrections may represent an implicit bias, discrimination, and racism. Furthermore, this practice masks economic and environmental factors. The flawed logic of innate, racial difference is also considered with disability estimates, preemployment physicals, and clinical diagnoses that rely on the spirometer. Thomas Jefferson's Notes on the State of Virginia (1832) may have initiated this mistaken belief by noting deficiencies of the "pulmonary apparatus" of blacks. Plantation physicians used Jefferson's statement to support slavery, believing that forced labor was a way to "vitalize the blood" of deficient black slaves. Samuel Cartwright, a Southern physician and slave holder, was the first to use spirometry to record deficiencies in pulmonary function of blacks. A massive study by Benjamin Apthorp Gould (1869) during the Civil War validated his results. The history of slavery created an environment where racial difference in lung capacity become so widely accepted that race correction became a scientifically valid procedure.

Chest wall strapping increases expiratory airflow and detectable airway segments in computer tomographic scans of normal and obstructed lungs

Chest wall strapping (CWS) induces breathing at low lung volumes but also increases parenchymal elastic recoil. In this study, we tested the hypothesis that CWS dilates airways via airway-parenchymal interdependence. In 11 subjects (6 healthy and 5 with mild to moderate COPD), pulmonary function tests and lung volumes were obtained in control (baseline) and the CWS state. Control and CWS-CT scans were obtained at 50% of control (baseline) total lung-capacity (TLC). CT lung volumes were analyzed by CT volumetry. If control and CWS-CT volumetry did not differ by more than 25%, airway dimensions were analyzed via automated airway segmentation. CWS-TLC was reduced on average to 71% of control-TLC in normal subjects and 79% of control-TLC in subjects with COPD. CWS increased expiratory airflow at 50% of control-TLC by 41% (3.50 ± 1.6 vs. 4.93 ± 1.9 l/s, P = 0.04) in normals and 316% in COPD(0.25 ± 0.05 vs 0.79 ± 0.39 l/s, P = 0.04). In 10 subjects (5 normals and 5 COPD), control and CWS-CT scans at 50% control-TLC did not differ more than 25% on CT volumetry and were included in the airway structure analysis. CWS increased the mean number of detectable airways with a diameter of ≤2 mm by 32.5% (65 ± 10 vs. 86 ± 124, P = 0.01) in normal subjects and by 79% (59 ± 19 vs. 104 ± 16, P = 0.01) in subjects with COPD. There was no difference in the number of detectable airways with diameters 2-4 mm and >4 mm in normal or in COPD subjects. In conclusion, CWS enhances the detection of small airways via automated CT airway segmentation and increases expiratory airflow in normal subjects as well as in subjects with mild to moderate COPD. NEW & NOTEWORTHY In normal and COPD subjects, chest wall strapping(CWS) increased the number of detectable small airways using automated CT airway segmentation. The concept of dysanapsis expresses the physiological variation in the geometry of the tracheobronchial tree and lung parenchyma based on development. We propose a dynamic concept to dysanapsis in which CWS leads to breathing at lower lung volumes with a corresponding increase in the size of small airways, a potentially novel, nonpharmacological treatment for COPD.

[The role of fetal magnetic resonance imaging in the study of congenital diaphragmatic hernia]

INTRODUCTION AND OBJECTIVES

Different echographic and fetal magnetic resonance (MRI) measurements have been described in the diagnosis of associated malformations and the prognosis of congenital diaphragmatic hernia (CDH). We have reviewed our experience searching for useful isolated or combined parameters and how MRI can complement ultrasound.

MATERIAL AND METHODS

We evaluated 29 fetuses with CDH. We examined ultrasonography: Lung to Head (LHR o/e) and in MRI: ipsilateral lung volume (IPV) and total expressed as percentage of observed / expected lung volume (VPT o/e) and percentage of herniated liver (PHH). We studied: survival, ECMO and associated malformations.

RESULTS

LHR o/e was the measure that best predicted survival (p< 0.05). VPT o/e did not predict survival or the need of ECMO (p> 0.05). PHH ≥19% was related to the need of ECMO. IPV < 2 cc required ECMO more frequently (p< 0.018) and when it was 0 cc in all cases. No combination of MR measurements was superior to LHR o/e in prediction of survival. MRI complemented the ultrasound in 4 cases: diaphragmatic eventration diagnosed with HDC, right HDC with fluid in the sac that suggested thoracic cyst, differentiation between spleen and lung that measured together overestimated the LHR and/or suspicion of Cornelia de Lange due to facial malformations.

CONCLUSIONS

Not a single or combined MRI measurement exceeds LHR o/e in survival prediction. MRI is related to prognosis and can be used to support ultrasound in making decisions. MRI occasionally provides complementary morphological information.

Low minute ventilation episodes during anesthesia recovery following intraperitoneal surgery as detected by a non-invasive respiratory volume monitor

An electrical impedance-based noninvasive respiratory volume monitor (RVM) accurately reports minute volume, tidal volume and respiratory rate. Here we used the RVM to quantify the occurrence of and evaluate the ability of clinical factors to predict respiratory depression in the post-anesthesia care unit (PACU). RVM generated respiratory data were collected from spontaneously breathing patients following intraperitoneal surgeries under general anesthesia admitted to the PACU. Respiratory depression was defined as low minute ventilation episode (LMVe, < 40% predicted minute ventilation for at least 2 min). We evaluated for associations between clinical variables including minute ventilation prior to opioid administration and LMVe following the first PACU administration of opioid. Also assessed was a low respiratory rate (< 8 breaths per minute) as a proxy for LMVe. Of 107 patients, 38 (36%) had LMVe. Affected patients had greater intraoperative opioid dose, P = 0.05. PACU opioids were administered to 45 (42.1%) subjects, of which 27 (25.2%) had LMVe (P = 0.42) within 30 min following opioid. Pre-opioid minute ventilation < 70% of predicted normal value was associated with LMVe, P < 0.01, (sensitivity = 100%, specificity = 81%).Low respiratory rate was a poor predictor of LMVe (sensitivity = 11.8%). Other clinical variables (e.g., obstructive sleep apnea) were not found to be predictors of LMVe. Using RVM we identified that mild, clinically nondetectable, respiratory depression prior to opioid administration in the PACU was associated with the development of substantial subsequent respiratory depression during the PACU stay.

A Standardized Method for Measuring Internal Lung Surface Area via Mouse Pneumonectomy and Prosthesis Implantation

Pulmonary morphology, physiology, and respiratory functions change in both physiological and pathological conditions. Internal lung surface area (ISA), representing the gas-exchange capacity of the lung, is a critical criterion to assess respiratory function. However, observer bias can significantly influence measured values for lung morphological parameters. The protocol that we describe here minimizes variations during measurements of two morphological parameters used for ISA calculation: internal lung volume (ILV) and mean linear intercept (MLI). Using ISA as a morphometric and functional parameter to determine the outcome of alveolar regeneration in both pneumonectomy (PNX) and prosthesis implantation mouse models, we found that the increased ISA following PNX treatment was significantly blocked by implantation of a prosthesis into the thoracic cavity1. The ability to accurately quantify ISA is not only expected to improve the reliability and reproducibility of lung function studies in injured-induced alveolar regeneration models, but also to promote mechanistic discoveries of multiple pulmonary diseases.

Estimation of respiratory volume from thoracoabdominal breathing distances: comparison of two models of machine learning

PURPOSE

The purposes of this study were to both improve the accuracy of respiratory volume (V) estimates using the respiratory magnetometer plethysmography (RMP) technique and facilitate the use of this technique.

METHOD

We compared two models of machine learning (ML) for estimating [Formula: see text]: a linear model (multiple linear regression-MLR) and a nonlinear model (artificial neural network-ANN), and we used cross-validation to validate these models. Fourteen healthy adults, aged [Formula: see text] years participated in the present study. The protocol was conducted in a laboratory test room. The anteroposterior displacements of the rib cage and abdomen, and the axial displacements of the chest wall and spine were measured using two pairs of magnetometers. [Formula: see text] was estimated from these four signals, and the respiratory volume was simultaneously measured using a spirometer ([Formula: see text]) under lying, sitting and standing conditions as well as various exercise conditions (working on computer, treadmill walking at 4 and 6 km[Formula: see text], treadmill running at 9 and 12  km [Formula: see text] and ergometer cycling at 90 and 110 W).

RESULTS

The results from the ANN model fitted the spirometer volume significantly better than those obtained through MLR. Considering all activities, the difference between [Formula: see text] and [Formula: see text] (bias) was higher for the MLR model ([Formula: see text] L) than for the ANN model ([Formula: see text] L).

CONCLUSION

Our results demonstrate that this new processing approach for RMP seems to be a valid tool for estimating V with sufficient accuracy during lying, sitting and standing and under various exercise conditions.

Ethnicity impacts the cystic fibrosis diagnosis: A note of caution

BACKGROUND

The diagnosis of Cystic Fibrosis (CF) is by consensus based on the same parameters in all patients, yet the influence of ethnicity has only scarcely been studied. We aimed at elucidating the impact of Asian descent on the diagnosis of CF.

METHODS

We performed a retrospective analysis of the CFTR2 and UK CF databases for clinical phenotype, sweat chloride values and CFTR mutations and compared the diagnostic characteristics of Asian to non-Asian patients with CF.

RESULTS

Asian patients with CF do not have a worse clinical phenotype. The repeatedly reported lower FEV₁ of Asian patients with CF is attributable to the influence of ethnicity on lung function in general. However, pancreatic sufficiency is more common in Asian patients with CF. The diagnosis of CF in people with Asian ancestry is heterogeneous as mean sweat chloride values are lower (92±26 versus 99±22mmol/L in controls) and 14% have sweat chloride values below 60mmol/L (versus 6% in non-Asians). Also, CFTR mutations differ from those in Caucasians: 55% of British Asian patients with CF do not have one mutation included in the routine newborn screening panel.

CONCLUSIONS

Bringing together the largest cohort of patients with CF and Asian ethnicity, we demonstrate that Asian roots impact on all three CF diagnostic pillars. These findings have implications for clinical practice in the increasingly ethnically diverse Western population.

Do nanoparticles provide a new opportunity for diagnosis of distal airspace disease?

There is a need for efficient techniques to assess abnormalities in the peripheral regions of the lungs, for example, for diagnosis of pulmonary emphysema. Considerable scientific efforts have been directed toward measuring lung morphology by studying recovery of inhaled micron-sized aerosol particles (0.4-1.5 µm). In contrast, it is suggested that the recovery of inhaled airborne nanoparticles may be more useful for diagnosis. The objective of this work is to provide a theoretical background for the use of nanoparticles in measuring lung morphology and to assess their applicability based on a review of the literature. Using nanoparticles for studying distal airspace dimensions is shown to have several advantages over other aerosol-based methods. 1) Nanoparticles deposit almost exclusively by diffusion, which allows a simpler breathing maneuver with minor artifacts from particle losses in the oropharyngeal and upper airways. 2) A higher breathing flow rate can be utilized, making it possible to rapidly inhale from residual volume to total lung capacity (TLC), thereby eliminating the need to determine the TLC before measurement. 3) Recent studies indicate better penetration of nanoparticles than micron-sized particles into poorly ventilated and diseased regions of the lungs; thus, a stronger signal from the abnormal parts is expected. 4) Changes in airspace dimensions have a larger impact on the recovery of nanoparticles. Compared to current diagnostic techniques with high specificity for morphometric changes of the lungs, computed tomography and magnetic resonance imaging with hyperpolarized gases, an aerosol-based method is likely to be less time consuming, considerably cheaper, simpler to use, and easier to interpret (providing a single value rather than an image that has to be analyzed). Compared to diagnosis by carbon monoxide (DL,CO), the uptake of nanoparticles in the lung is not affected by blood flow, hemoglobin concentration or alterations of the alveolar membranes, but relies only on lung morphology.

Optical measurement of breathing: algorithm volume calibration and preliminary validation on healthy trained subjects

The use of optical technologies may be beneficial when measuring breathing biomechanics. The purpose of this study was twofold: i) to enhance the optoelectronic plethysmography (OEP) algorithm performance for the volume estimation by the use of a novel volume calibration procedure and ii) to compare the OEP volumes gained by a commercial optoelectronic system against actual respiratory volumes measured by a breath-by-breath gas analyzer (BbB). The OEP volume algorithm calibration was performed by the use of a novel volume calibration procedure based on both a calibrator device that delivered known volumes changes and one ad-hoc designed software for the static and dynamic calibration analysis. OEP algorithm threshold, accuracy, repeatability and the volume algorithm calibration were investigated. Tidal volume (VT) measurements performed simultaneously by the calibrated OEP algorithm and BbB analyzer were compared. VT measured simultaneously by OEP and BbB was collected during submaximal exercise tests in five trained healthy participants in two conditions (with hunched shoulders and in normal shoulder position). The two methods were compared by linear regression and Bland-Altman analysis in both positions. The average difference between methods and the discrepancy were calculated. The OEP-BbB correlation was high in both positions, R2=0.92 and R2=0.97 for hunch and normal one, respectively. Bland-Altman analysis demonstrated that OEP algorithm systematic difference was lower than 100mL. The limits of agreement assessed in both positions are comparable. The difference between measurements suggesting that OEP may be a useful tool to analyze chest wall volume changes and breathing mechanics during intense exercise.

A Systematic Approach to Multiple Breath Nitrogen Washout Test Quality

Background

Accurate estimates of multiple breath washout (MBW) outcomes require correct operation of the device, appropriate distraction of the subject to ensure they breathe in a manner representative of their relaxed tidal breathing pattern, and appropriate interpretation of the acquired data. Based on available recommendations for an acceptable MBW test, we aimed to develop a protocol to systematically evaluate MBW measurements based on these criteria.

Methods

50 MBW test occasions were systematically reviewed for technical elements and whether the breathing pattern was representative of relaxed tidal breathing by an experienced MBW operator. The impact of qualitative and quantitative criteria on inter-observer agreement was assessed across eight MBW operators (n = 20 test occasions, compared using a Kappa statistic).

Results

Using qualitative criteria, 46/168 trials were rejected: 16.6% were technically unacceptable and 10.7% were excluded due to inappropriate breathing pattern. Reviewer agreement was good using qualitative criteria and further improved with quantitative criteria from (κ = 0.53–0.83%) to (κ 0.73–0.97%), but at the cost of exclusion of further test occasions in this retrospective data analysis.

Conclusions

The application of the systematic review improved inter-observer agreement but did not affect reported MBW outcomes.

Impaired lung transfer factor in fibromyalgia syndrome

OBJECTIVES

The aim of this study was to evaluate whether pulmonary diffusing capacity is impaired in patients with fibromyalgia (FM) as it is in those with other diseases characterised by autonomic nerve system (ANS) dysfunction such as type 1 diabetes.

METHODS

Forty-five consecutive anti-nuclear antibody (ANA)-negative female Caucasian patients aged 50.1± 5.6 years with FM and compared with 45 healthy female control volunteers matched in terms of age and body mass index (BMI). The autonomic function has been evaluated by means of standard electrocardiography (ECG), finger blood pressure respiration, and muscle sympathetic nerve activity (MSNA) at rest and during a stepwise tilt test up to 75°. Their autonomic profiles were drawn up on the basis of MSNA, plasma catecholamine levels, and spectral indices of cardiac sympathetic and vagal modulation, and sympathetic vasomotor control computed by means of the spectrum analysis of RR and systolic arterial pressure (SAP) variability. Lung volumes and dynamic spirometry parameters were assessed by means of plethysmography. All of the patients were clinically evaluated and completed the FQI and COMPASS questionnaire.

RESULTS

There was no difference in lung volumes between the FM patients and healthy controls, but DLCO (83±4 vs. 96±5; p<0.001), Kco (84±5 vs 98±5; p<0.001), DM (12.7±2.4 vs 13.6±1.8; p<0.05) and Vc (48±3.9 vs 65±7; p<0.001) were significantly reduced in the patients. The COMPASS-31, RCS and pain VAS scores significantly correlated with DLCO, Kco and Vc with the correlation being particularly close in the case of Vc. Furthermore, univariate Cox proportional hazard analysis showed that the three scores were all significantly associated with an increased risk of impaired DLCO (respectively, χ(2) 16.21, p<0.0005; χ(2) 7.09, p<0.005; χ(2) 6.37, p<0.01).

CONCLUSIONS

FM impairs DLCO mainly as a result of a reduction in Vc, and that this defect is inversely proportional to the severity of the dysfunction suggesting a relationship between impaired DLCO and autonomic nerve dysfunction.

Geometric uncertainties in voluntary deep inspiration breath hold radiotherapy for locally advanced lung cancer

BACKGROUND AND PURPOSE

Deep inspiration breath hold (DIBH) increases lung volume and can potentially reduce treatment-related toxicity in locally advanced lung cancer. We estimated geometric uncertainties in visually guided voluntary DIBH and derived the appropriate treatment margins for different image-guidance strategies.

MATERIAL AND METHODS

Seventeen patients were included prospectively. An optical marker-based respiratory monitoring with visual guidance enabled comfortable DIBHs, adjusted to each patient's performance. All patients had three consecutive DIBH CTs at each of the treatment fractions 2, 16 and 31. DIBH reproducibility was evaluated as inter- and intra-fractional variations in lung volume, tumour position and differential motion between primary tumour and mediastinal lymph nodes.

RESULTS

Lung volume increased by median 60% in DIBH. Inter- and intra-fractional lung volume variations were median 2.1% and 1.1%, respectively. Inter- and intra-fractional uncertainties in 3D tumour position were 4.8 ± 2.8 mm and 1.7 ± 1.4 mm (mean ± SD). Inter- and intra-fractional differential motion was 4.8 ± 3.3 mm and 0.0 ± 1.1 mm.

CONCLUSIONS

For single targets, visually guided voluntary DIBH radiotherapy is highly reproducible provided an image-guidance strategy with tumour registration is performed. If the primary tumour is separated from the mediastinal lymph nodes, inter-fractional differential motion remains a challenge and margins must be adapted to reflect the image registration strategy.

[A New Method of Analyzing the Closing Volume (CV) Curve: "N2 First Derivative Wave Method"]

Evaluation of the lung function involves the measurement of many factors. The closing volume (CV) curve is clinically important as an index of uneven alveolar ventilation and airway closure. Although conventional methods for CV measurement are usually based on the pattern of the exhaled nitrogen (N2) concentration curve with respect to the lung volume, it is often difficult to measure the steep pattern of patients with chronic obstructive pulmonary disease (COPD). In this paper, we proposed a new method called the "N2 first derivative (fdN) wave method" for measuring CV. The N2 concentration of the CV curve was transformed to a derivative with respect to the lung volume, which revealed the existence of cardiogenic oscillations. Discrimination between phases III and IV was straightforward based on the difference in the slope or in the amplitude of oscillations of the fdN wave. Our new method was able to distinguish phase IV from phase III using the difference in amplitude of the oscillation of the fdN wave even in the presence of COPD with steep patterns of the CV curve. Close relationships were seen among normal subjects including COPD patients in both the slope of the alveolar plateau (ΔN2) and the CV values measured with the conventional and new methods. In conclusion, the new method we propose in this paper was able to provide measurements of CV for all subjects including those with COPD. [Original]

A new approach to assess COPD by identifying lung function break-points

PURPOSE

COPD is a progressive disease, which can take different routes, leading to great heterogeneity. The aim of the post-hoc analysis reported here was to perform continuous analyses of advanced lung function measurements, using linear and nonlinear regressions.

PATIENTS AND METHODS

Fifty-one COPD patients with mild to very severe disease (Global Initiative for Chronic Obstructive Lung Disease [GOLD] Stages I-IV) and 41 healthy smokers were investigated post-bronchodilation by flow-volume spirometry, body plethysmography, diffusion capacity testing, and impulse oscillometry. The relationship between COPD severity, based on forced expiratory volume in 1 second (FEV1), and different lung function parameters was analyzed by flexible nonparametric method, linear regression, and segmented linear regression with break-points.

RESULTS

Most lung function parameters were nonlinear in relation to spirometric severity. Parameters related to volume (residual volume, functional residual capacity, total lung capacity, diffusion capacity [diffusion capacity of the lung for carbon monoxide], diffusion capacity of the lung for carbon monoxide/alveolar volume) and reactance (reactance area and reactance at 5Hz) were segmented with break-points at 60%-70% of FEV1. FEV1/forced vital capacity (FVC) and resonance frequency had break-points around 80% of FEV1, while many resistance parameters had break-points below 40%. The slopes in percent predicted differed; resistance at 5 Hz minus resistance at 20 Hz had a linear slope change of -5.3 per unit FEV1, while residual volume had no slope change above and -3.3 change per unit FEV1 below its break-point of 61%.

CONCLUSION

Continuous analyses of different lung function parameters over the spirometric COPD severity range gave valuable information additional to categorical analyses. Parameters related to volume, diffusion capacity, and reactance showed break-points around 65% of FEV1, indicating that air trapping starts to dominate in moderate COPD (FEV1 =50%-80%). This may have an impact on the patient's management plan and selection of patients and/or outcomes in clinical research.

New predictive equation for lung volume using chest computed tomography for size matching in lung transplantation

PURPOSE

Lung size matching is important in lung transplantation (LT). With advances in computed tomography (CT) technology, multidetector row CT can accurately measure the thoracic cage and lung volumes. The objective of this study was to generate a new regression equation using demographic data based on the measured CT lung volume in a healthy population to predict the CT lung volume of the donor in LT size matching.

MATERIALS AND METHODS

The medical records of healthy subjects who underwent chest CT scans to screen for lung cancer were retrospectively reviewed. CT lung volume was semi-automatically measured using a threshold-based auto-segmentation technique. New regression equations for CT lung volume were generated by multiple linear regression analysis using demographic data including height (H, cm), weight (W, kg), and age (A, years). The percentage error rate (%) of the equations were calculated as ([Estimated CT lung volume--Measured CT lung volume]/Measured CT lung volume × 100). A percentage error rate within ± 20% was considered acceptable.

RESULTS

A total of 141 men aged 27 to 55 years (mean, 46.7 ± 6.2 years) and 128 women aged 20 to 55 years (mean, 45.4 ± 7.2 years) were enrolled. The final regression equations for CT lung volume were (-5.890 + 0.067 H - 0.030 W + 0.020 A) in men and (-6.698 + 0.072 H - 0.024 W) in women. The mean absolute error rate was 10.9 ± 9.0% and 11.0 ± 8.5% in men and women, respectively. Percentage error rates were within ± 20% in 121 of 141 (85.8%) men and 113 of 128 (88.3%) women.

CONCLUSION

These equations could predict the CT lung volume of healthy subjects using demographic data. Using these equations, the predicted CT lung volume of donors could be matched to the measured CT lung volume of recipients in lung transplantation.

Bronchoscopic lung volume reduction with endobronchial valves for patients with heterogeneous emphysema and intact interlobar fissures (the BeLieVeR-HIFi study): a randomised controlled trial

BACKGROUND

Lung volume reduction surgery improves survival in selected patients with emphysema, and has generated interest in bronchoscopic approaches that might achieve the same effect with less morbidity and mortality. Previous trials with endobronchial valves have yielded modest group benefits because when collateral ventilation is present it prevents lobar atelectasis.

METHODS

We did a single-centre, double-blind sham-controlled trial in patients with both heterogeneous emphysema and a target lobe with intact interlobar fissures on CT of the thorax. We enrolled stable outpatients with chronic obstructive pulmonary disease who had a forced expiratory volume in 1 s (FEV1) of less than 50% predicted, significant hyperinflation (total lung capacity >100% and residual volume >150%), a restricted exercise capacity (6 min walking distance <450 m), and substantial breathlessness (MRC dyspnoea score ≥3). Participants were randomised (1:1) by computer-generated sequence to receive either valves placed to achieve unilateral lobar occlusion (bronchoscopic lung volume reduction) or a bronchoscopy with sham valve placement (control). Patients and researchers were masked to treatment allocation. The study was powered to detect a 15% improvement in the primary endpoint, the FEV1 3 months after the procedure. Analysis was on an intention-to-treat basis. The trial is registered at controlled-trials.com, ISRCTN04761234.

FINDINGS

50 patients (62% male, FEV1 [% predicted] mean 31·7% [SD 10·2]) were enrolled to receive valves (n=25) or sham valve placement (control, n=25) between March 1, 2012, and Sept 30, 2013. In the bronchoscopic lung volume reduction group, FEV1 increased by a median 8·77% (IQR 2·27-35·85) versus 2·88% (0-8·51) in the control group (Mann-Whitney p=0·0326). There were two deaths in the bronchoscopic lung volume reduction group and one control patient was unable to attend for follow-up assessment because of a prolonged pneumothorax.

INTERPRETATION

Unilateral lobar occlusion with endobronchial valves in patients with heterogeneous emphysema and intact interlobar fissures produces significant improvements in lung function. There is a risk of significant complications and further trials are needed that compare valve placement with lung volume reduction surgery.

FUNDING

Efficacy and Mechanism Evaluation Programme, funded by the Medical Research Council (MRC) and managed by the National Institute for Health Research (NIHR) on behalf of the MRC-NIHR partnership.

A new method for respiratory-volume monitoring based on long-period fibre gratings

Respiratory-volume monitoring is an indispensable part of mechanical ventilation. Here we present a new method of the respiratory-volume measurement based on a single fibre-optical long-period sensor of bending and the correlation between torso curvature and lung volume. Unlike the commonly used air-flow based measurement methods the proposed sensor is drift-free and immune to air-leaks. In the paper, we explain the working principle of sensors, a two-step calibration-test measurement procedure and present results that establish a linear correlation between the change in the local thorax curvature and the change of the lung volume. We also discuss the advantages and limitations of these sensors with respect to the current standards.