Lung Reactance Research Articles

Respiratory Oscillometry in Patients With Acute Hypoxemic Respiratory Failure: A Feasibility Study.

Assessing respiratory mechanics in patients with acute hypoxemic respiratory failure who are not intubated could provide useful information about illness trajectory. Oscillometry is a respiratory function test used to measure total respiratory impedance during tidal breathing, which reveals resistive and elastic properties of the lung. This study assessed the feasibility of oscillometry in patients with acute hypoxemic respiratory failure and described their respiratory mechanics. Adult participants with acute hypoxemic respiratory failure who were receiving noninvasive respiratory support with [Formula: see text] ≥0.4 and flow ≥6 L/min underwent oscillometry at baseline and after resolution of acute hypoxemic respiratory failure. The primary end point was the number of participants who completed the baseline measurement. The feasibility criterion was in obtaining baseline oscillometry measurements in ≥80% of enrolled participants. Of 183 patients screened between July 2022 and August 2023, 29% were unable to cooperate due to altered mental state, 20% with extreme hypoxemia were excluded because of clinical instability, and 12% declined participation. Of the 10 participants (5.4%) recruited, all tolerated oscillometry measurements. At baseline, the median (minimum, maximum) [Formula: see text] was 0.8 (0.4, 0.8), median oxygen saturation of 94% dropped to a nadir of 82% at the end of oscillometry and recovered within 2 min. Lung reactance was increased, with a reactance area of 25 (15-32) cm H2O/L. Hypoxemia resolved in 9 participants. After resolution of acute hypoxemic respiratory failure in 8 (6-16) d, the median reactance area dropped to 15 (14-19) cm H2O/L. Respiratory mechanics in the participants with acute hypoxemic respiratory failure who were not intubated could be assessed by oscillometry in carefully selected cases.

Cold air exposure at − 15 °C induces more airway symptoms and epithelial stress during heavy exercise than rest without aggravated airway constriction

PurposeExposure to cold air may harm the airways. It is unclear to what extent heavy exercise adds to the cold-induced effects on peripheral airways, airway epithelium, and systemic immunity among healthy individuals. We investigated acute effects of heavy exercise in sub-zero temperatures on the healthy airways.MethodsTwenty-nine healthy individuals underwent whole body exposures to cold air in an environmental chamber at − 15 °C for 50 min on two occasions; a 35-min exercise protocol consisting of a 5-min warm-up followed by 2 × 15 min of running at 85% of VO2max vs. 50 min at rest. Lung function was measured by impulse oscillometry (IOS) and spirometry before and immediately after exposures. CC16 in plasma and urine, and cytokines in plasma were measured before and 60 min after exposures. Symptoms were surveyed pre-, during and post-trials.ResultsFEV1 decreased after rest (− 0.10 ± 0.03 L, p < 0.001) and after exercise (− 0.06 ± 0.02 L, p = 0.012), with no difference between trials. Exercise in − 15 °C induced greater increases in lung reactance (X5; p = 0.023), plasma CC16 (p < 0.001) as well as plasma IL-8 (p < 0.001), compared to rest. Exercise induced more intense symptoms from the lower airways, whereas rest gave rise to more general symptoms.ConclusionHeavy exercise during cold air exposure at − 15 °C induced signs of an airway constriction to a similar extent as rest in the same environment. However, biochemical signs of airway epithelial stress, cytokine responses, and symptoms from the lower airways were more pronounced after the exercise trial.

Older age at Fontan completion is associated with reduced lung volumes and increased lung reactance

BackgroundFontan patients have abnormal lung function, in particular restrictive lung disease and low diffusing capacity of carbon monoxide (DLCO). We sought to further characterise these abnormalities with detailed pulmonary function testing and examine associations with clinical parameters. Methods132 Fontan patients across Australia and New Zealand underwent spirometry, with 126 subjects included in final analyses. Measurement of diffusion capacity (DLCO) including its components (alveolar volume (VA) and rate of uptake of CO (KCO)) and oscillometry (reactance (X5) and resistance (R5)) were assessed in a subset of Fontan patients (n = 44) and healthy controls (n = 12). Double diffusion (to assess diffusing capacity of nitric oxide (DLNO), capillary blood volume (Vc), alveolar capillary membrane function (DmCO)) was performed in Fontan patients (n = 18) and healthy controls (n = 12). ResultsFEV1 and FVC z-scores were low in Fontan subjects (mean − 1.67 ± 1.24 and − 1.61 ± 1.29, respectively) and correlated with exercise capacity. Compared to controls, z-scores for X5, DLCO, KCO, VA and DLNO were significantly lower in Fontan patients. R5, Vc and DmCO z-scores were preserved. X5 was associated with VA (r = 0.41,p = 0.009) and DmCO (r = 0.61,p = 0.008). Older age at Fontan completion was associated with lower z-scores for FEV1 (r = −0.46,p = 0.002), FVC (r = −0.47,p = 0.002), X5 (r = −0.32,p = 0.033) and VA (r = −0.36,p = 0.022). ConclusionFontan patients have a reduced DLCO which is largely driven by low VA. Lung stiffness (X5) is increased which is associated with VA and DmCO. These parameters negatively correlate with older age of Fontan completion suggesting that earlier Fontan completion may have a beneficial effect on lung function.

High-flow nasal cannula improves respiratory impedance evaluated by impulse oscillometry in chronic obstructive pulmonary disease patients: a randomised controlled trial

Non-pharmacological treatment with high-flow nasal cannula (HFNC) may play a vital role in treatment of patients with chronic obstructive pulmonary disease (COPD). To evaluate the efficacy of HFNC, impulse oscillation system (IOS) is a new noninvasive technique in measuring the impedance of different portions of lungs. It shows higher sensitivity in contrast to conventional pulmonary function tests (PFT). However, whether IOS is an appropriate technique to evaluate the efficacy of HFNC in improving the impedance of small airways or peripheral lung in patients with COPD is still unclear. We enrolled 26 stable COPD participants randomised into two groups receiving HFNC or nasal cannula (NC) for 10 min followed by a 4-week washout period and crossover alternatively. IOS was used to detect the difference of respiratory impedance after HFNC or NC interventions. IOS parameters, PFT results, transcutaneous partial pressure of carbon dioxide, peripheral oxygen saturation, body temperature, respiratory rate, pulse rate, and blood pressure at the time of pre-HFNC, post-HFNC, pre-NC, and post-NC, were collected and analysed using SPSS (version 25.0, IBM, Armonk, NY, USA). The IOS measurement indicated that HFNC significantly improved R5, R5% predicted, R5–R20, X5-predicted, and Fres compared with NC, whereas no significant difference was observed through the PFT measurement. The beneficial effect of HFNC in improving small airway resistance and peripheral lung reactance compared with that of NC in patients with stable COPD was confirmed through IOS measurement.Trial registration: ClinicalTrials.gov NCT05130112 22/11/2021.

Pulmonary 99mTc-HMDP uptake correlates with restrictive ventilatory defects and abnormal lung reactance in transthyretin cardiac amyloidosis patients

BackgroundPulmonary involvement in individuals with transthyretin cardiac amyloidosis is unclear. The aim of this study was to quantify 99mTc-hydroxy methylene diphosphonate (HMDP) lung retention in hereditary transthyretin (ATTRv) cardiac amyloidosis patients and to relate tracer uptake intensity to pulmonary function and aerobic capacity.MethodsWe prospectively enrolled 20 patients with biopsy-proven ATTRv cardiac amyloidosis and 20 control subjects. Cardiac involvement was confirmed by echocardiography and nuclear imaging using 99mTc-HMDP. Semi-quantitative analysis of the heart, rib and lung retention was assessed using a simple region of interest technique. Pulmonary function was evaluation by the means of whole-body plethysmography, diffusing capacity of the lung for carbon monoxide, forced oscillation technique and cardiopulmonary exercise testing.ResultsPulmonary tracer uptake estimated by lung to rib retention ratio was higher in ATTRv amyloidosis patients compared with control subjects: median 0.62 (0.55–0.69) vs 0.51 (0.46–0.60); p = 0.014. Analysis of relation between lung 99mTc-HMDP retention and pulmonary function parameters shown statistically significant correlations with total lung volume (% predicted), lung reactance (Xrs 5 Hz) and peak VO2, suggesting total lung capacity restriction impaired elastic properties of the lung and poor aerobic capacity.ConclusionOur study suggests that some grade of pulmonary retention of 99mTc-HMDP may occur in patients with cardiac ATTRv amyloidosis, which can elicit deleterious effects on patient’s lung function and aerobic capacity.

Oscillatory mechanics at birth for identifying infants requiring surfactant: a prospective, observational trial

BackgroundCurrent criteria for surfactant administration assume that hypoxia is a direct marker of lung-volume de-recruitment. We first introduced an early, non-invasive assessment of lung mechanics by the Forced Oscillation Technique (FOT) and evaluated its role in predicting the need for surfactant therapy.ObjectivesTo evaluate whether lung reactance (Xrs) assessment by FOT within 2 h of birth identifies infants who would need surfactant within 24 h; to eventually determine Xrs performance and a cut-off value for early detection of infants requiring surfactant.MethodsWe conducted a prospective, observational, non-randomized study in our tertiary NICU in Milan. Eligible infants were born between 27+0 and 34+6 weeks’ gestation, presenting respiratory distress after birth. Exclusion criteria: endotracheal intubation at birth, major malformations participation in other interventional trials, parental consent denied. We assessed Xrs during nasal CPAP at 5 cmH2O at 10 Hz within 2 h of life, recording flow and pressure tracing through a Fabian Ventilator for off-line analysis. Clinicians were blinded to FOT results.ResultsWe enrolled 61 infants, with a median [IQR] gestational age of 31.9 [30.3; 32.9] weeks and birth weight 1490 [1230; 1816] g; 2 infants were excluded from the analysis for set-up malfunctioning. 14/59 infants received surfactant within 24 h. Xrs predicted surfactant need with a cut-off − 33.4 cmH2O*s/L and AUC-ROC = 0.86 (0.76–0.96), with sensitivity 0.85 and specificity 0.83. An Xrs cut-off value of − 23.3 cmH2O*s/L identified infants needing surfactant or respiratory support > 28 days with AUC-ROC = 0.89 (0.81–0.97), sensitivity 0.86 and specificity 0.77. Interestingly, 12 infants with Xrs < − 23.3 cmH2O*s/L (i.e. de-recruited lungs) did not receive surfactant and subsequently required prolonged respiratory support.ConclusionXrs assessed within 2 h of life predicts surfactant need and respiratory support duration in preterm infants. The possible role of Xrs in improving the individualization of respiratory management in preterm infants deserves further investigation.

Early Oscillatory Mechanics Predict Surfactant Need and Respiratory Outcomes in Preterm Infants

Background: Current criteria for surfactant administration assume that hypoxia is a direct marker of lung-volume de-recruitment. Objectives: To evaluate whether lung reactance (Xrs) assessment by FOT within 2h of birth identifies infants who would need surfactant within 24h; to eventually determine Xrs performance and a cut-off value for early detection of infants requiring surfactant. Methods: We conducted a prospective, observational, non-randomized study in our tertiary NICU in Milan. Eligible infants were born between 27+0 and 34+6 weeks' gestation presenting respiratory distress after birth. Exclusion criteria: endotracheal intubation at birth, major malformations. We assessed Xrs during nasal CPAP at 5cmH2O at 10Hz within 2h of life, recording flow and pressure tracing through a Fabian Ventilator for off-line analysis. Clinicians were blinded to FOT results. Results: We enrolled 61 infants, with a median[IQR] gestational age of 31.9[30.3; 32.9]weeks and birth weight 1490[1230; 1816]g. 14/59 infants received surfactant within 24h. Xrs predicted surfactant need with a cut-off -33.4 cmH2O*s/L and AUC-ROC=0.86 (0.76-0.96), with sensitivity 0.85 and specificity 0.83. An Xrs cut-off value of -23.3 cmH2O*s/L identified infants needing surfactant or respiratory support >28 days with AUC-ROC=0.89 (0.81-0.97), sensitivity 0.86 and specificity 0.77. Interestingly, 12 infants with Xrs <-23.3 cmH2O*s/L (i.e. de-recruited lungs) did not receive surfactant and subsequently required prolonged respiratory support. Interpretation: Xrs assessed within 2 h of life predicts surfactant need and respiratory support duration in preterm infants. Xrs possible role for improving the individualization preterm infants' respiratory management deserves further investigation. Funding: None Declaration of Interest: RD reports grants and other from Restech, personal fees from Philips Healthcare, outside the submitted work; Dr Dellaca' has a patent on the detection of EFL by Forced Oscillation technique (FOT) with royalties paid to Philips Respironics and Restech Srl, a patent on monitoring lung volume recruitment by FOT with royalties paid to Vyaire, and a patent on early detection of exacerbations by home monitoring of FOT with royalties paid to Restech and is co-founder and shareholder of Restech Srl, a spin-off company of the Politecnico di Milano University producing medical devices for lung function testing based on FOT. AL was consultant for Getinge and Chiesi S.p.A and received travel grants from Vapotherm and Fischer&Pykel. The other authors have no financial interest to declare. Ethical Approval: Our ethical committee approved the research protocol in April 2016. Between December 2016 and February 2020, we recruited the study participants, whose follow-up lasted until discharge home.

Impulse oscillometry, an aid or a substitute?

IntroductionIn the field of pulmonary medicine, respiratory mechanics and physiology are obviously affected by most pathological lesions and diseases, either primary disease or part of systemic ones. In the era of rheumatoid arthritis (RA), airway abnormality and interstitial lung pneumonia and/or fibrosis are the most common findings that face physicians during the disease course and affect morbidity, survival, and quality of life of patients with RA. Impulse oscillometry (IOS) is a noninvasive technique that needs minimal patient cooperation, which makes it suitable for any age including even children and can be performed by most patients.Aim of the workTo describe the respiratory measures done by IOS in patients with RA and to correlate them with those measured by spirometry.Patients and methodsA total of 60 patients with RA were recruited in this cross-sectional observational study. They were investigated via pulmonary function assessments, including spirometry and IOS, to measure forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and FEV1/FVC, and maximal expiratory flow at 25% (MEF 25%)in addition to R5% of predicted, R20% of predicted, R5–20, X5, and area under the curve.ResultsIOS measures indicated increased airway resistance (R5%, R20%, and R5–20) with decreased lung reactance (X5). Moreover, a positive correlation between disease duration and X5, between X5 and area under the curve and each of FEV1%, FVC%, and MEF 25%, whereas a negative correlation between R5–20 and each of FEV1%, FVC%, and MEF 25%.ConclusionIOS is an easy and rapid maneuver that requires minimal patient cooperation. It can identify lung affection in those who have mild or even normal spirometric changes. It is just a good screening test in patients with RA to detect early pathophysiologic lung changes. However, it needs further investigations to clarify the mechanism of these changes.

Early life exposure to coal mine fire smoke emissions and altered lung function in young children.

Long-term respiratory risks following exposure to relatively short periods of poor air quality early in life are unknown. We aimed to evaluate the association between exposure to a 6-week episode of air pollution from a coal mine fire in children aged <2 years, and their lung function 3 years after the fire. We conducted a prospective cohort study. Individual exposure to 24-h average and peak concentrations of particulate matter with an aerodynamic diameter <2.5 μm in diameter (PM2.5 ) during the fire were estimated using dispersion and chemical transport modelling. Lung function was measured using the forced oscillation technique (FOT), generating standardized Z-scores for resistance and reactance at a frequency of 5 Hz (Rrs5 and Xrs5 ), and area under the reactance curve (AX). We used linear regression models to assess the associations between PM2.5 exposure and lung function, adjusted for potential confounders. Of the 203 infants originally recruited, 84 aged 4.3 ± 0.5 years completed FOT testing. Median (interquartile range, IQR) for average and peak PM2.5 were 7.9 (6.8-16.8) and 103.4 (60.6-150.7) μg/m3 , respectively. The mean ± SD Z-scores for Rrs5 , Xrs5 and AX were 0.56 ± 0.80, -0.76 ± 0.88 and 0.72 ± 0.92, respectively. After adjustment for potential confounders including maternal smoking during pregnancy, a 10 μg/m3 increase in average PM2.5 was significantly associated with worsening AX (β-coefficient: 0.260; 95% CI: 0.019, 0.502), while the association between a 100-μg/m3 increase in peak PM2.5 and AX was borderline (0.166; 95% CI: -0.002, 0.334). Infant exposure to coal mine fire emissions could be associated with long-term impairment of lung reactance.

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.

Effects of combination therapy indacaterol/glycopyrronium versus tiotropium on moderate to severe COPD: evaluation of impulse oscillometry and exacerbation rate

BackgroundSmall airways are considered the major site of airflow limitation in COPD. Impulse oscillometry (IOS) is a forced oscillation technique, which provides passive measurement of lung mechanics. It can differentiate small airway from large airway obstruction and is more sensitive than spirometry for peripheral airway disease. In this study the efficacy of the combination of Indacaterol/Glycopirronium (IND/GLY) versus Tiotropium on airway resistance (R5, R20, R5–20), lung reactance (X) and resonant frequency in moderate to severe COPD patients has been evaluated. We also evaluated inspiratory capacity (IC), forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), exacerbation rate and quality of life.MethodsForty patients were monitored with forced oscillation technique and spirometry. Patients were randomized in 2 groups: 20 received fixed dose once daily Indacaterol/Glycopyrronium (Group A) and 20 received single Tiotropium (Group B).The oscillometry parameters were the measure of resistance in the airways at 5 Hz (R5), at 20 Hz (R20) and the lung reactance (X).ResultsThere was a statistically significant difference between pre-dosing at V1 and at follow up visits in R5, R20 and X values in patients receiving dual bronchodilation but not in control group. Pre-dosing IC value at follow up visits in patients receiving dual bronchodilation had a statistical significant variation.ConclusionsThe “new” bronchodilator combination LABA/LAMA significantly reduces bronchial obstruction in small airways too. The oscillometry demonstrated greater sensitivity compared with spirometry for monitoring outcome measures of airway obstruction and the effect of long-term therapy.

Effects of combination therapy indacaterol/ glycopyrronium versus tiotropium on moderate to severe COPD: evaluation of impulse oscillometry and exacerbation rate

Background: Small airways are considered the major site of airflow limitation in COPD. Impulse oscillometry (IOS) is a forced oscillation technique, which provides passive measurement of lung mechanics. It can differentiate small airway from large airway obstruction and is more sensitive than spirometry for peripheral airway disease. In this study the efficacy of the combination of Indacaterol/Glycopirronium (IND/GLY) versus Tiotropium on airway resistance (R5, R20, R5–20), lung reactance (X) and resonant frequency in moderate to severe COPD patients has been evaluated. We also evaluated inspiratory capacity (IC), forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), exacerbation rate and quality of life. Methods: Forty patients were monitored with forced oscillation technique and spirometry. Patients were randomized in 2 groups: 20 received fixed dose once daily Indacaterol/Glycopyrronium (Group A) and 20 received single Tiotropium (Group B). The oscillometry parameters were the measure of resistance in the airways at 5 Hz (R5), at 20 Hz (R20) and the lung reactance (X). Results: There was a statistically significant difference between pre-dosing at V1 and at follow up visits in R5, R20 and X values in patients receiving dual bronchodilation but not in control group. Pre-dosing IC value at follow up visits in patients receiving dual bronchodilation had a statistical significant variation. Conclusions: The “new” bronchodilator combination LABA/LAMA significantly reduces bronchial obstruction in small airways too. The oscillometry demonstrated greater sensitivity compared with spirometry for monitoring outcome measures of airway obstruction and the effect of long-term therapy.

Advantage of impulse oscillometry over spirometry to diagnose chronic obstructive pulmonary disease and monitor pulmonary responses to bronchodilators: An observational study.

Objectives:This retrospective study was a comparative analysis of sensitivity of impulse oscillometry and spirometry techniques for use in a mixed chronic obstructive pulmonary disease group for assessing disease severity and inhalation therapy.Methods:A total of 30 patients with mild-to-moderate chronic obstructive pulmonary disease were monitored by impulse oscillometry, followed by spirometry. Lung function was measured at baseline after bronchodilation and at follow-up (3–18 months). The impulse oscillometry parameters were resistance in the small and large airways at 5 Hz (R5), resistance in the large airways at 15 Hz (R15), and lung reactance (area under the curve X; AX).Results:After the bronchodilator therapy, forced expiratory volume in 1 second (FEV1) readings evaluated by spirometry were unaffected at baseline and at follow-up, while impulse oscillometry detected an immediate improvement in lung function, in terms of AX (p = 0.043). All impulse oscillometry parameters significantly improved at follow-up, with a decrease in AX by 37% (p = 0.0008), R5 by 20% (p = 0.0011), and R15 by 12% (p = 0.0097).Discussion:Impulse oscillometry parameters demonstrated greater sensitivity compared with spirometry for monitoring reversibility of airway obstruction and the effect of maintenance therapy. Impulse oscillometry may facilitate early treatment dose optimization and personalized medicine for chronic obstructive pulmonary disease patients.

Three-dimensional Airway Tree Architecture and Pulmonary Function

The airway tree is a primary conductive structure, and airways' morphologic characteristics, or variations thereof, may have an impact on airflow, thereby affecting pulmonary function. The objective of this study was to investigate the correlation between airway tree architecture, as depicted on computed tomography, and pulmonary function. A total of 548 chest computed tomographic examinations acquired on different patients at full inspiration were included in this study. The patients were enrolled in a study of chronic obstructive pulmonary disease (Specialized Center for Clinically Oriented Research) and underwent pulmonary function testing in addition to computed tomographic examinations. A fully automated airway tree segmentation algorithm was used to extract the three-dimensional airway tree from each examination. Using a skeletonization algorithm, airway tree volume-normalized architectural measures, including total airway length, branch count, and trachea length, were computed. Correlations between airway tree measurements with pulmonary function testing parameters and chronic obstructive pulmonary disease severity in terms of the Global Initiative for Obstructive Lung Disease classification were computed using Spearman's rank correlations. Non-normalized total airway volume and trachea length were associated (P < .01) with lung capacity measures (ie, functional residual capacity, total lung capacity, inspiratory capacity, vital capacity, residual volume, and forced expiratory vital capacity). Spearman's correlation coefficients ranged from 0.27 to 0.55 (P < .01). With the exception of trachea length, all normalized architecture-based measures (ie, total airway volume, total airway length, and total branch count) had statistically significant associations with the lung function measures (forced expiratory volume in 1 second and the ratio of forced expiratory volume in 1 second to forced expiratory vital capacity), and adjusted volume was associated with all three respiratory impedance measures (lung reactance at 5 Hz, lung resistance at 5 Hz, and lung resistance at 20 Hz), and adjusted branch count was associated with all respiratory impedance measures but lung resistance at 20 Hz. When normalized for lung volume, all airway architectural measures were statistically significantly associated with chronic obstructive pulmonary disease severity, with Spearman's correlation coefficients ranging from -0.338 to -0.546 (P < .01). Despite the large variability in anatomic characteristics of the airway tree across subjects, architecture-based measures demonstrated statistically significant associations (P < .01) with nearly all pulmonary function testing measures, as well as with disease severity.

Impulse oscillometry in preschool children and association with body mass index

The use of the impulse oscillometry system (IOS) allows differentiated lung function testing with a minimum of cooperation at normal tidal breathing. The aim of this cross-sectional study was to assess the association of body mass (overweight and obese) with oscillometric parameters in preschool children. A preschool medical check of 518 children (age 6.01 ± 0.25 years) included IOS recordings of airway resistance and lung reactance (MasterScreen IOS, CareFusion, Höchberg, Germany). Measured values of respiratory resistance (R5) and reactance (X5) at 5 Hz were correlated with BMI. In addition, data were compared with recently published reference equations. In this young age group of 241 boys and 277 girls there was no significant association between oscillometric parameters and BMI. When compared with current IOS reference values of healthy subjects the relationship of R5 (109 ± 25%) and X5 (105.5 ± 35%) suggested mildly elevated peripheral resistance in this unselected group of preschool children. IOS is ideally suited to obtain measurements of respiratory function in preschool children. At the age of 6 years, standard oscillometric values do not indicate impaired respiratory function associated with increased BMI.

Skeletal dysplasias: Evaluation with impulse oscillometry and thoracoabdominal motion analysis

Children with skeletal dysplasia (SD) often have pulmonary disease, which can be life threatening. In clinical practice, chest wall and formal respiratory function tests are difficult to perform owing to the small size and cooperation. The objective of this study was to demonstrate distinct thoracopulmonary function patterns in children with SD. We conducted a retrospective study reviewing pulmonary function tests from 17 patients with the diagnosis of SD. Three subgroups were studied: Morquio syndrome (MS), metatropic-spondylocostal dysplasia (MSD), and unspecified skeletal dysplasias (SDU). Rib cage contribution to tidal volume excursions (%RC), phase angle (Phtheta), phase relation during total breath (PhRTB), respiratory resistance (Rrs(5-35) Hz), respiratory reactance (Xrs(5-35) Hz), resonant frequency, and their frequency-dependency were analyzed. Values were age-matched and height-matched to reference values of healthy subjects. There was a decrease in %RC and an increase in PhRTB (P < 0.05) in the SD group. %RC differed between subgroups [MS: 46.4 +/- 1.8% SE, MSD: 18.4 +/- 2.6% SE, SDU: 27.5 +/- 5.2% SE (P < 0.05)]; Phtheta was within reference values only in MS, which exhibited a decrease in Xrs at 5 Hz (P < 0.05) and an increase in Rrs independent of the frequency. SDU showed a decrease in Xrs at 35 Hz (P < 0.05), no differences were found in Rrs. In MS, a correlation was found between RC and Rrs at all frequencies (r = -0.98, P < 0.01) and between Xrs(5-10) and Phtheta (r = -0.93, P < 0.05). Thoracoabdominal dysfunction was associated with altered chest wall reactance at high frequencies in a subgroup of SD patients with abnormal lung reactance and central airway involvement in MS.

Die moderne Impulsoszillometrie im Spektrum lungenfunktioneller Messmethoden

Impulse oscillometry (IOS) is a computer supported method for the measurement of complex mechanical airway characteristics. Bronchial obstructions can reliably be diagnosed by IOS when more complex parameters such as frequency dependence of resistance (FDR) and lung reactance (X5) are evaluated in cases with more severe obstruction. Parameters of conventional methods like pneumotachography, spirometry, and bodyplethysmography show relatively low correlations due to the different measurement principles, not only in comparison to IOS, but also in between one another. The IOS is a convenient method for patients with a low dependency on cooperation for the evaluation of obstructive airway diseases complementary to the established standard methods. Furthermore, IOS may provide a sensitive screening tool for the early detection of bronchial obstructions not only in paediatrics but also in occupational medicine.

The reversibility of increased airways resistance in chronic heart failure measured by impulse oscillometry

BackgroundPatients with chronic heart failure complain of breathlessness and fatigue on exercise. Airways resistance is increased and lung compliance is reduced in chronic heart failure patients. The aim of this study was to determine whether the pulmonary abnormalities are reversible and whether any improvements lead to changes to exercise capacity or symptoms. MethodsTwelve patients with stable chronic heart failure and 10 matched controls underwent repeated assessment of airways resistance using impulse oscillometry and peak exercise testing with metabolic gas exchange after receiving nebulized saline as placebo or combined salbutamol and ipratropium bromide in a double-blind crossover randomized fashion. ResultsPatients had lower peak oxygen consumption and a steeper slope relating ventilation to carbon dioxide production than controls. Bronchodilators reduced peripheral airways resistance in patients (0.53 versus 0.38, P<.02) and controls (0.21 versus 0.19, P<.005) and increased measures of compliance in both groups. There was no effect on the peak oxygen consumption, exercise time, ventilation to carbon dioxide slope, or anaerobic threshold. There was an increase in peak tidal volume (Vt) in both groups but this did not lead to an increase in peak ventilation. The slope relating symptoms to ventilation (ie, Borg/Ve) was significantly reduced in the patients after bronchodilators (17%±8%, P<.05). The relationship between the improvement in Vt and reduction in gradient of the Borg/Ve slope was significant (r=.40, P<.05). ConclusionsNebulized bronchodilators improve airways resistance, lung reactance, and peak tidal volume during exercise in chronic heart failure but do not increase peak exercise capacity. They do, however, reduce the symptom of breathlessness.

Pulmonary Pathologies in Pallid Mice Result from Nonhematopoietic Defects

Several single gene pigment mutants of inbred C57BL/6J mice display a triad of subcellular granule-associated defects: oculocutaneous pigment dilution, prolonged bleeding due to defects in platelet dense granules, and abnormal lysosomes. These features also characterize Hermansky–Pudlak Syndrome (HPS), making these mice relevant animal models for HPS. Mice of one mutant strain, pallid, in addition to the hallmark triad of signs, also exhibit age-dependent lung pathology. Respiratory system mechanics showed that the age-dependent histopathology of pallid mice was accompanied by a decrease in lung reactance. Furthermore, the possibility that pallid pulmonary pathology may result from persistent inflammation due to microhemorrhage owing to the platelet defect was examined. Hematopoietic reconstitution of pallid mice with marrow from normal C57BL/6J donors did not prevent the development of the pulmonary histopathology or respiratory system mechanics characteristic of the pallid genotype. Similarly, wild-type mice 12 months after engraftment with pallid marrow did not develop pallid-like pulmonary histopathology or respiratory system mechanics. Thus, pallid-associated pulmonary functional and structural pathologies are not linked to the marrow (bleeding) genotype, but instead are the result of an age-dependent process resulting from a defect(s) in one or more nonhematopoietic cell types.

Low-dose halothane produces airway dilatation but does not alter parenchymal mechanics in the normal canine lung

The purpose of this study was to examine whether halothane reduces the contractile tone of the normal lung and to distinguish the effects of halothane on airways from those on lung tissue. We also tested whether a mathematical model was capable of quantitatively describing the mechanical changes in the lung produced by halothane. We measured lung impedence (ZL(omega) a complex function of real (lung resistance) and imaginary (reactance) parts) at low frequencies in dogs using a forced volume oscillation technique before and during 1 MAC halothane anaesthesia. Halothane produced small changes in ZL(omega). The lung resistance tended to decrease during halothane anaesthesia whereas the lung reactance did not show change. Using an alveolar capsule technique to separate the airways from the lung tissue components, these lung mechanical changes were induced mainly by alterations in lung tissue and not in the airways. Our mathematical model featured a single airway leading to an alveolar region surrounded by a viscoelastic lung tissue. In the model analysis, estimates of airway resistance and inertance decreased by the administration of halothane. In contrast, estimates of lung tissue elastance and resistance did not change during halothane anaesthesia. These modeling results were consistent with those obtained by direct alveolar pressure measurements. Our results suggest that a low concentration of halothane dilates the airways but does not alter the parenchymal mechanics in the normal lung, and that the model provides a quantitative tool to assess lung mechanics precisely, if respiratory signals are measured only at the true airway opening.