Mechanical correlates of dyspnea in bronchial asthma.

We hypothesized that dyspnea and its descriptors, that is, chest tightness, inspiratory effort, unrewarded inspiration, and expiratory difficulty in asthma reflect different mechanisms of airflow obstruction and their perception varies with the severity of bronchoconstriction. Eighty-three asthmatics were studied before and after inhalation of methacholine doses decreasing the 1-sec forced expiratory volume by ~15% (mild bronchoconstriction) and ~25% (moderate bronchoconstriction). Symptoms were examined as a function of changes in lung mechanics. Dyspnea increased with the severity of obstruction, mostly because of inspiratory effort and chest tightness. At mild bronchoconstriction, multivariate analysis showed that dyspnea was related to the increase in inspiratory resistance at 5 Hz (R 5) (r (2) = 0.10, P = 0.004), chest tightness to the decrease in maximal flow at 40% of control forced vital capacity, and the increase in R 5 at full lung inflation (r (2) = 0.15, P = 0.006), inspiratory effort to the temporal variability in R 5-19 (r (2) = 0.13, P = 0.003), and unrewarded inspiration to the recovery of R 5 after deep breath (r (2) = 0.07, P = 0.01). At moderate bronchoconstriction, multivariate analysis showed that dyspnea and inspiratory effort were related to the increase in temporal variability in inspiratory reactance at 5 Hz (X 5) (r (2) = 0.12, P = 0.04 and r (2) = 0.18, P < 0.001, respectively), and unrewarded inspiration to the decrease in X 5 at maximum lung inflation (r (2) = 0.07, P = 0.04). We conclude that symptom perception is partly explained by indexes of airway narrowing and loss of bronchodilatation with deep breath at low levels of bronchoconstriction, but by markers of ventilation heterogeneity and lung volume recruitment when bronchoconstriction becomes more severe

Actual performance of mechanical ventilators in ICU: a multicentric quality control study.

Even if the performance of a given ventilator has been evaluated in the laboratory under very well controlled conditions, inappropriate maintenance and lack of long-term stability and accuracy of the ventilator sensors may lead to ventilation errors in actual clinical practice. The aim of this study was to evaluate the actual performances of ventilators during clinical routines. A resistance (7.69 cmH(2)O/L/s) - elastance (100 mL/cmH(2)O) test lung equipped with pressure, flow, and oxygen concentration sensors was connected to the Y-piece of all the mechanical ventilators available for patients in four intensive care units (ICUs; n = 66). Ventilators were set to volume-controlled ventilation with tidal volume = 600 mL, respiratory rate = 20 breaths/minute, positive end-expiratory pressure (PEEP) = 8 cmH(2)O, and oxygen fraction = 0.5. The signals from the sensors were recorded to compute the ventilation parameters. The average ± standard deviation and range (min-max) of the ventilatory parameters were the following: inspired tidal volume = 607 ± 36 (530-723) mL, expired tidal volume = 608 ± 36 (530-728) mL, peak pressure = 20.8 ± 2.3 (17.2-25.9) cmH(2)O, respiratory rate = 20.09 ± 0.35 (19.5-21.6) breaths/minute, PEEP = 8.43 ± 0.57 (7.26-10.8) cmH(2)O, oxygen fraction = 0.49 ± 0.014 (0.41-0.53). The more error-prone parameters were the ones related to the measure of flow. In several cases, the actual delivered mechanical ventilation was considerably different from the set one, suggesting the need for improving quality control procedures for these machines

Ventilation heterogeneity in obesity.

Obesity is associated with important decrements in lung volumes. Despite this, ventilation remains normally or near normally distributed at least for moderate decrements in functional residual capacity (FRC). We tested the hypothesis that this is because maximum flow increases presumably as a result of an increased lung elastic recoil. Forced expiratory flows corrected for thoracic gas compression volume, lung volumes, and forced oscillation technique at 5-11-19 Hz were measured in 133 healthy subjects with a body mass index (BMI) ranging from 18 to 50 kg/m(2). Short-term temporal variability of ventilation heterogeneity was estimated from the interquartile range of the frequency distribution of the difference in inspiratory resistance between 5 and 19 Hz (R5-19_IQR). FRC \% predicted negatively correlated with BMI (r = -0.72, P < 0.001) and with an increase in slope of either maximal (r = -0.34, P < 0.01) or partial flow-volume curves (r = -0.30, P < 0.01). Together with a slight decrease in residual volume, this suggests an increased lung elastic recoil. Regression analysis of R5-19_IQR against FRC \% predicted and expiratory reserve volume (ERV) yielded significantly higher correlation coefficients by nonlinear than linear fitting models (r(2) = 0.40 vs. 0.30 for FRC \% predicted and r(2) = 0.28 vs. 0.19 for ERV). In conclusion, temporal variability of ventilation heterogeneities increases in obesity only when FRC falls approximately below 65\% of predicted or ERV below 0.6 liters. Above these thresholds distribution is quite well preserved presumably as a result of an increase in lung recoil

Clinical trials for elderly patients with multiple diseases (CHROMED) pilot study

The problem COPD (Chronic Obstructive Pulmonary Disease) is a significant socioeconomic burden which, particularly when associated with comorbidities such as Chronic Heart Failure (CHF), markedly affects patient outcomes. Care models based on telemedicine systems that enable early diagnosis and treatment of exacerbations are advocated to reduce the impact of chronic diseases on patient outcomes and health service costs. CHROMED (www.chromed.eu) is an international EU-funded project aimed at developing a multi-centre clinical trial to evaluate the impact of a new integrated home care approach to reduce care costs and improve quality of life in COPD. The approach We collaborated in a pilot study prior to the main trial which will include 300 patients from seven European countries (Italy, Spain, UK, Estonia, Slovenia, Sweden and Norway) with nine partners. The home monitoring system includes a novel forced oscillation technique (FOT) device for self-measurement of lung mechanics (RESMONPRO DIARY, Restech srl, Italy), a touch screen for collecting patients' symptoms and, where COPD is associated with CHF, by a device for measuring heart rate (HR), blood pressure (BP), pulse oximetry (SpO2) and body temperature (WRIST CLINIC, Medic4all, Israel). Findings The pilot included 16 patients (n=11 COPD, 5 COPD+CHF). The average monitoring period was 48.3±23.4 days resulting in a total of 504 patient days. The percentage of data correctly received within the period was: lung impedance and breathing pattern 90.0%; HR 91.7%, BP 91.7%; SpO2 74.0% and body temperature 71.4%. During the pilot, one patient was treated pharmacologically for an exacerbation of COPD. Offline processing demonstrated that the system identified warning of an exacerbation five days prior to admission. We also analysed qualitative data from patients and professionals about the acceptability of the telemedicine system and the interaction between patients, professionals and the monitoring system. Consequences The data suggest good acceptability and short-term compliance among patients with COPD. Lung function, HR and BP provided the most reliable data. The full RCT is currently under way and will be completed in August 2015

An individualized approach to sustained inflation duration at birth improves outcomes in newborn preterm lambs

A sustained first inflation (SI) at birth may aid lung liquid clearance and aeration, but the impact of SI duration relative to the volume-response of the lung is poorly understood. We compared three SI strategies: 1) variable duration defined by attaining volume equilibrium using real-time electrical impedance tomography (EIT; SIplat); 2) 30 s beyond equilibrium (SIlong); 3) short 30-s SI (SI30); and 4) positive pressure ventilation without SI (no-SI) on spatiotemporal aeration and ventilation (EIT), gas exchange, lung mechanics, and regional early markers of injury in preterm lambs. Fifty-nine fetal-instrumented lambs were ventilated for 60 min after applying the allocated first inflation strategy. At study completion molecular and histological markers of lung injury were analyzed. The time to SI volume equilibrium, and resultant volume, were highly variable; mean (SD) 55 (34) s, coefficient of variability 59%. SIplat and SIlong resulted in better lung mechanics, gas exchange and lower ventilator settings than both no-SI and SI30. At 60 min, alveolar-arterial difference in oxygen was a mean (95% confidence interval) 130 (13, 249) higher in SI30 vs. SIlong group (two-way ANOVA). These differences were due to better spatiotemporal aeration and tidal ventilation, although all groups showed redistribution of aeration towards the nondependent lung by 60 min. Histological lung injury scores mirrored spatiotemporal change in aeration and were greatest in SI30 group (P < 0.01, Kruskal-Wallis test). An individualized volume-response approach to SI was effective in optimizing aeration, homogeneous tidal ventilation, and respiratory outcomes, while an inadequate SI duration had no benefit over positive pressure ventilation alone

The association of tidal EFL with exercise performance, exacerbations, and death in COPD

Background: Tidal expiratory flow limitation (EFLT) is frequently found in patients with COPD and can be detected by forced oscillations when within-breath reactance of a single-breath is â\u89¥0.28 kPa·s·L-1. The present study explored the association of within-breath reactance measured over multiple breaths and EFLT with 6-minute walk distance (6MWD), exacerbations, and mortality. Methods: In 425 patients, spirometry and forced oscillation technique measurements were obtained on eight occasions over 3 years. 6MWD was assessed at baseline and at the 3-year visit. Respiratory symptoms, exacerbations, and hospitalizations were recorded. A total of 5-year mortality statistics were retrieved retrospectively. We grouped patients according to the mean within-breath reactance (Î\u94(Formula Presented.)), measured over several breaths at baseline, calculated as mean inspiratory-mean expiratory reactance over the sampling period. In addition to the established threshold of EFLT, an upper limit of normal (ULN) was defined using the 97.5th percentile of Î\u94(Formula Presented.) of the healthy controls in the study; 6MWDs were compared according to Î\u94(Formula Presented.), as normal, â\u89¥ ULN < EFLT, or â\u89¥ EFLT. Annual exacerbation rates were analyzed using a negative binomial model in the three groups, supplemented by time to first exacerbation analysis, and dichotomizing patients at the ULN. Results: In patients with COPD and baseline Î\u94(Formula Presented.) below the ULN (0.09 kPa·s·L-1), 6MWD was stable. 6MWD declined significantly in patients with Î\u94(Formula Presented.) â\u89¥ ULN. Worse lung function and more exacerbations were found in patients with COPD with Î\u94(Formula Presented.) â\u89¥ ULN, and patients with Î\u94(Formula Presented.) â\u89¥ ULN had shorter time to first exacerbation and hospitalization. A significantly higher mortality was found in patients with Î\u94(Formula Presented.) â\u89¥ ULN and FEV1.50%. Conclusion: Patients with baseline Î\u94(Formula Presented.) â\u89¥ ULN had a deterioration in exercise performance, more exacerbations, and greater hospitalizations, and, among those with moderate airway obstruction, a higher mortality. Î\u94(Formula Presented.) is a novel independent marker of outcome in COPD

Fixed-Duration versus EIT-determined Volume-Response Defined Sustained Inflation in Preterm Lambs

We compared a standard fixed duration Sustained Inflation (SI) during resuscitation at birth in preterm lambs with two SI guided by real-time volumetric EIT imaging, lasting respectively until volume plateau and until 30s beyond plateau. Global and local end expiratory volume (EEV), lung mechanics and gas exchange were measured. Both the volumetric EIT guided approaches were feasible and resulted in better relative lung aeration

Telemonitoring in Chronic Obstructive Pulmonary Disease (CHROMED). A Randomized Clinical Trial

Rationale: Early detection of COPD exacerbations using tele-monitoring of physiological variables might reduce the frequency of hospitalisation. Objectives: To evaluate the efficacy of home monitoring of lung mechanics by the forced oscillation technique (FOT) and cardiac parameters in older COPD patients with co-morbidities. Methods: This multicentre, randomized clinical trial recruited 312 GOLD grade II-IV COPD patients (median age 71 years [IQR:66-76], 49.6% grade II, 50.4% grade III-IV), with a history of exacerbation in the previous year and at least one non-pulmonary co-morbidity. Patients were randomised to usual care (n=158) or tele-monitoring (n=154) and followed for 9 months. All tele-monitoring patients self-assessed lung mechanics daily and in a subgroup with congestive heart failure (n=37) cardiac parameters were also monitored. An algorithm identified deterioration, triggering a telephone contact to determine appropriate interventions. Measurements and Main results: Primary outcomes were time to first hospitalisation (TTFH) and change in EQ-5D utility index score. Secondary outcomes included: rate of antibiotic/corticosteroid prescriptions, hospitalisation, CAT, PHQ-9 and MLHF questionnaire scores, quality-adjusted life years and healthcare costs. Tele-monitoring did not affect TTFH, EQ-5D utility index score, antibiotic prescriptions, hospitalization rate and questionnaire scores. In an exploratory analysis, tele-medicine was associated with fewer repeat hospitalizations (-54%, p=0.017). Conclusions: In older COPD patients with co-morbidities remote monitoring of lung function by FOT and cardiac parameters did not change TTFH and EQ-5D. Clinical trial registration available at www.clinicaltrials.gov, ID NCT01960907