Relative impact of respiratory muscle activity on tidal flow and end expiratory volume in healthy neonates

INTRODUCTION: It has been suggested that infants dynamically regulate their tidal flow and end-expiratory volume level. The interaction between muscle activity, flow and lung volume in spontaneously sleeping neonates is poorly studied, since it requires the assessment of transcutaneous electromyography of respiratory muscles (rEMG) in matched comparison to lung function measurements. METHODS: After determining feasibility and repeatability of rEMG in 20 spontaneously sleeping healthy neonates, we measured the relative impact of intercostal and diaphragmatic EMG activity in direct comparison to the resulting tidal flow and FRC. RESULTS: We found good feasibility, repeatability and correlation of timing indices between rEMG activity and flow. The rEMG amplitude was significantly dependent on the resistive load of the face mask. Diaphragm and intercostal muscle activity commenced prior to the onset of flow and remained active during the expiratory cycle. The relative contribution of intercostal and diaphragmatic activity to flow was variable and changed dynamically. CONCLUSION: Using matched rEMG, air flow and lung volume measurements, we have found good feasibility and repeatability of intercostal and diaphragm rEMG measurements and provide the first quantitative measures of the temporal relationship between muscle activity and flow in spontaneously sleeping healthy neonates. Lung mechanical function is dynamically regulated and adapts on a breath to breath basis. So, non-invasive rEMG measurements alone or in combination with lung function might provide a more comprehensive picture of pulmonary mechanics in future studies. The data describing the timing of EMG and flow may be important for future studies of EMG triggered mechanical ventilation.

Circulating plasma surfactant protein type B as biological marker of alveolar-capillary barrier damage in chronic heart failure

BACKGROUND: Surfactant protein type B (SPB) is needed for alveolar gas exchange. SPB is increased in the plasma of patients with heart failure (HF), with a concentration that is higher when HF severity is highest. The aim of this study was to evaluate the relationship between plasma SPB and both alveolar-capillary diffusion at rest and ventilation versus carbon dioxide production during exercise. METHODS AND RESULTS: Eighty patients with chronic HF and 20 healthy controls were evaluated consecutively, but the required quality for procedures was only reached by 71 patients with HF and 19 healthy controls. Each subject underwent pulmonary function measurements, including lung diffusion for carbon monoxide and membrane diffusion capacity, and maximal cardiopulmonary exercise test. Plasma SPB was measured by immunoblotting. In patients with HF, SPB values were higher (4.5 [11.1] versus 1.6 [2.9], P=0.0006, median and 25th to 75th interquartile), whereas lung diffusion for carbon monoxide (19.7+/-4.5 versus 24.6+/-6.8 mL/mm Hg per min, P<0.0001, mean+/-SD) and membrane diffusion capacity (28.9+/-7.4 versus 38.7+/-14.8, P<0.0001) were lower. Peak oxygen consumption and ventilation/carbon dioxide production slope were 16.2+/-4.3 versus 26.8+/-6.2 mL/kg per min (P<0.0001) and 29.7+/-5.9 and 24.5+/-3.2 (P<0.0001) in HF and controls, respectively. In the HF population, univariate analysis showed a significant relationship between plasma SPB and lung diffusion for carbon monoxide, membrane diffusion capacity, peak oxygen consumption, and ventilation/carbon dioxide production slope (P<0.0001 for all). On multivariable logistic regression analysis, membrane diffusion capacity (beta, -0.54; SE, 0.018; P<0.0001), peak oxygen consumption (beta, -0.53; SE, 0.036; P=0.004), and ventilation/carbon dioxide production slope (beta, 0.25; SE, 0.026; P=0.034) were independently associated with SPB. CONCLUSIONS: Circulating plasma SPB levels are related to alveolar gas diffusion, overall exercise performance, and efficiency of ventilation showing a link between alveolar-capillary barrier damage, gas exchange abnormalities, and exercise performance in HF.

Subclinical thyroid dysfunction and the risk of stroke: a systematic review and meta-analysis

Subclinical thyroid dysfunction has been associated with coronary heart disease, but the risk of stroke is unclear. Our aim is to combine the evidence on the association between subclinical thyroid dysfunction and the risk of stroke in prospective cohort studies. We searched Medline (OvidSP), Embase, Web-of-Science, Pubmed Publisher, Cochrane and Google Scholar from inception to November 2013 using a cohort filter, but without language restriction or other limitations. Reference lists of articles were searched. Two independent reviewers screened articles according to pre-specified criteria and selected prospective cohort studies with baseline thyroid function measurements and assessment of stroke outcomes. Data were derived using a standardized data extraction form. Quality was assessed according to previously defined quality indicators by two independent reviewers. We pooled the outcomes using a random-effects model. Of 2,274 articles screened, six cohort studies, including 11,309 participants with 665 stroke events, met the criteria. Four of six studies provided information on subclinical hyperthyroidism including a total of 6,029 participants and five on subclinical hypothyroidism (n = 10,118). The pooled hazard ratio (HR) was 1.08 (95 % CI 0.87-1.34) for subclinical hypothyroidism (I (2) of 0 %) and 1.17 (95 % CI 0.54-2.56) for subclinical hyperthyroidism (I (2) of 67 %) compared to euthyroidism. Subgroup analyses yielded similar results. Our systematic review provides no evidence supporting an increased risk for stroke associated with subclinical thyroid dysfunction. However, the available literature is insufficient and larger datasets are needed to perform extended analyses. Also, there were insufficient events to exclude clinically significant risk from subclinical hyperthyroidism, and more data are required for subgroup analyses.

Mass spectrometric study of molecular and ionic sublimation of lanthanum triiodide

The molecular and ionic composition of saturated vapor over lanthanum triiodide was studied by Knudsen effusion mass spectrometry. The (LaI3)n molecules (n = 1–3) and the [I(LaI3)n]− ions (n = 0–4) were observed. The partial pressures of the molecules were determined and the enthalpies of sublimation, ΔsH° (298.15 K) in kJ mol−1, in the form of monomers (304 ± 7), dimers (428 ± 25), and trimers (455 ± 50) were obtained by the second and third laws of thermodynamics. The enthalpy of formation, ΔfH° (298.15 K) in kJ mol−1, of the LaI3 (−376 ± 10), La2I6 (−932 ± 25), La3I9 (−1585 ± 50) molecules and the LaI4− (−841 ± 24), La2I7− (−1486 ± 32) ions were determined. The electron work function, φe = 3.5 ± 0.3 eV, for the LaI3 crystal was calculated from the thermochemical cycle.

Perceived functional ability assessed with the spinal function sort: is it valid for European rehabilitation settings in patients with non-specific non-acute low back pain?

The aim of this study involving 170 patients suffering from non-specific low back pain was to test the validity of the spinal function sort (SFS) in a European rehabilitation setting. The SFS, a picture-based questionnaire, assesses perceived functional ability of work tasks involving the spine. All measurements were taken by a blinded research assistant; work status was assessed with questionnaires. Our study demonstrated a high internal consistency shown by a Cronbach's alpha of 0.98, reasonable evidence for unidimensionality, spearman correlations of >0.6 with work activities, and discriminating power for work status at 3 and 12 months by ROC curve analysis (area under curve = 0.760 (95% CI 0.689-0.822), respectively, 0.801 (95% CI 0.731-0.859). The standardised response mean within the two treatment groups was 0.18 and -0.31. As a result, we conclude that the perceived functional ability for work tasks can be validly assessed with the SFS in a European rehabilitation setting in patients with non-specific low back pain, and is predictive for future work status.

Sonographic Assessment of Fetal Cardiac Function: Indirect Measurements of Fetal Cardiac Function, Newer Techniques and Clinical Applications

Noninvasive blood flow measurements based on Doppler ultrasound studies are the main clinical tool for studying the cardiovascular status of fetuses at risk for circulatory compromise. Usually, qualitative analysis of peripheral arteries and in particular clinical situations such as severe growth restriction or volume overload also of venous vessels close to the heart or of flow patterns in the heart is being used to gauge the level of compensation in a fetus. However, quantitative assessment of the driving force of the fetal circulation, the cardiac output remains an elusive goal in fetal medicine. This article reviews the methods for direct and indirect assessment of cardiac function and explains new clinical applications. Part 1 of this review describes the concept of cardiac function and cardiac output and the techniques that have been used to quantify output. Part 2 summarizes the use of arterial and venous Doppler studies in the fetus and gives a detailed description of indirect measurements of cardiac function (like indices derived from the duration of segments of the cardiac cycle) with current examples of their application.

Upper bound on neutrino mass based on T2K neutrino timing measurements

The Tokai to Kamioka (T2K) long-baseline neutrino experiment consists of a muon neutrino beam, produced at the J-PARC accelerator, a near detector complex and a large 295 km distant far detector. The present work utilizes the T2K event timing measurements at the near and far detectors to study neutrino time of flight as function of derived neutrino energy. Under the assumption of a relativistic relation between energy and time of flight, constraints on the neutrino rest mass can be derived. The sub-GeV neutrino beam in conjunction with timing precision of order tens of ns provide sensitivity to neutrino mass in the few MeV/c^2 range. We study the distribution of relative arrival times of muon and electron neutrino candidate events at the T2K far detector as a function of neutrino energy. The 90% C.L. upper limit on the mixture of neutrino mass eigenstates represented in the data sample is found to be m^2 < 5.6 MeV^2/c^4.

Normative data for lung function and exhaled nitric oxide in unsedated healthy infants

Despite association with lung growth and long-term respiratory morbidity, there is a lack of normative lung function data for unsedated infants conforming to latest European Respiratory Society/American Thoracic Society standards. Lung function was measured using an ultrasonic flow meter in 342 unsedated, healthy, term-born infants at a mean ± sd age of 5.1 ± 0.8 weeks during natural sleep according to the latest standards. Tidal breathing flow-volume loops (TBFVL) and exhaled nitric oxide (eNO) measurements were obtained from 100 regular breaths. We aimed for three acceptable measurements for multiple-breath washout and 5-10 acceptable interruption resistance (R(int)) measurements. Acceptable measurements were obtained in ≤ 285 infants with high variability. Mean values were 7.48 mL·kg⁻¹ (95% limits of agreement 4.95-10.0 mL·kg⁻¹) for tidal volume, 14.3 ppb (2.6-26.1 ppb) for eNO, 23.9 mL·kg⁻¹ (16.0-31.8 mL·kg⁻¹) for functional residual capacity, 6.75 (5.63-7.87) for lung clearance index and 3.78 kPa·s·L⁻¹ (1.14-6.42 kPa·s·L⁻¹) for R(int). In males, TBFVL outcomes were associated with anthropometric parameters and in females, with maternal smoking during pregnancy, maternal asthma and Caesarean section. This large normative data set in unsedated infants offers reference values for future research and particularly for studies where sedation may put infants at risk. Furthermore, it highlights the impact of maternal and environmental risk factors on neonatal lung function.

Repeatability of nerve fiber layer thickness measurements in patients with glaucoma and without glaucoma using spectral-domain and time-domain OCT

The aim of this work is to assess the repeatability of spectral-domain-OCT (SD-OCT) retinal nerve fiber layer thickness (RNFL) thickness measurements in a non-glaucoma group and patients with glaucoma and to compare these results to conventional time-domain-OCT (TD-OCT).

How reliable are Hounsfield-unit measurements in forensic radiology?

OBJECTIVE: To assess the reliability of computed tomography (CT) numbers, also known as Hounsfield-units (HU) in the differentiation and identification of forensically relevant materials and to provide instructions to improve the reproducibility of HU measurements in daily forensic practice. MATERIALS AND METHODS: We scanned a phantom containing non-organic materials (glass, rocks and metals) on three different CT scanners with standardized parameters. The t-test was used to assess the influence of the scanner, the size and shape of different types of regions-of-interest (ROI), the composition and shape of the object, and the reader performance on HU measurements. Intra-class correlation coefficient was used to assess intra- and inter-reader reliability. RESULTS: HU values did not change significantly as a function of ROI-shape or -size (p>0.05). Intra-reader reliability reached ICC values >0.929 (p<0.001). Inter-reader reliability was also excellent with an ICC of 0.994 (p<0.001). Four of seven objects yielded significantly different CT numbers at different levels within the object (p<0.05). In 6/7 objects the HU changed significantly from CT scanner to CT scanner (p<0.05). CONCLUSION: Reproducible CT number measurements can be achieved through correct ROI-placement and repeat measurements within the object of interest. However, HU may differ from CT-scanner to CT-scanner. In order to obtain comparable CT numbers we suggest that a dedicated Forensic Reference Phantom be developed.

Sonographic Assessment of Fetal Cardiac Function: Introduction and Direct Measurement of Cardiac Function

Noninvasive blood flow measurements based on Doppler ultrasound studies are the main clinical tool for studying the cardiovascular status in fetuses at risk for circulatory compromise. Usually, qualitative analysis of peripheral arteries and, in particular clinical situations such as severe growth restriction or volume overload, also of venous vessels close to the heart or of flow patterns in the heart are being used to gauge the level of compensation in a fetus. Quantitative assessment of the driving force of the fetal circulation, the cardiac output, however, remains an elusive goal in fetal medicine. This article reviews the methods for direct and indirect assessment of cardiac function and explains new clinical applications. Part 1 of this review describes the concept of cardiac function and cardiac output and the techniques that have been used to quantify output. Part 2 summarizes the use of arterial and venous Doppler studies in the fetus and gives a detailed description of indirect measures of cardiac function (like indices derived from the duration of segments of the cardiac cycle) with current examples of their application.

Structure and function of the glucose PTS transporter from Escherichia coli

The glucose transporter IICB of the Escherichia coli phosphotransferase system (PTS) consists of a polytopic membrane domain (IIC) responsible for substrate transport and a hydrophilic C-terminal domain (IIB) responsible for substrate phosphorylation. We have overexpressed and purified a triple mutant of IIC (mut-IIC), which had recently been shown to be suitable for crystallization purposes. Mut-IIC was homodimeric as determined by blue native-PAGE and gel-filtration, and had an eyeglasses-like structure as shown by negative-stain transmission electron microscopy (TEM) and single particle analysis. Glucose binding and transport by mut-IIC, mut-IICB and wildtype-IICB were compared with scintillation proximity and in vivo transport assays. Binding was reduced and transport was impaired by the triple mutation. The scintillation proximity assay allowed determination of substrate binding, affinity and specificity of wildtype-IICB by a direct method. 2D crystallization of mut-IIC yielded highly-ordered tubular crystals and made possible the calculation of a projection structure at 12Å resolution by negative-stain TEM. Immunogold labeling TEM revealed the sidedness of the tubular crystals, and high-resolution atomic force microscopy the surface structure of mut-IIC. This work presents the structure of a glucose PTS transporter at the highest resolution achieved so far and sets the basis for future structural studies.

Tidal volume single breath washout of two tracer gases--a practical and promising lung function test

Background Small airway disease frequently occurs in chronic lung diseases and may cause ventilation inhomogeneity (VI), which can be assessed by washout tests of inert tracer gas. Using two tracer gases with unequal molar mass (MM) and diffusivity increases specificity for VI in different lung zones. Currently washout tests are underutilised due to the time and effort required for measurements. The aim of this study was to develop and validate a simple technique for a new tidal single breath washout test (SBW) of sulfur hexafluoride (SF6) and helium (He) using an ultrasonic flowmeter (USFM). Methods The tracer gas mixture contained 5% SF6 and 26.3% He, had similar total MM as air, and was applied for a single tidal breath in 13 healthy adults. The USFM measured MM, which was then plotted against expired volume. USFM and mass spectrometer signals were compared in six subjects performing three SBW. Repeatability and reproducibility of SBW, i.e., area under the MM curve (AUC), were determined in seven subjects performing three SBW 24 hours apart. Results USFM reliably measured MM during all SBW tests (n = 60). MM from USFM reflected SF6 and He washout patterns measured by mass spectrometer. USFM signals were highly associated with mass spectrometer signals, e.g., for MM, linear regression r-squared was 0.98. Intra-subject coefficient of variation of AUC was 6.8%, and coefficient of repeatability was 11.8%. Conclusion The USFM accurately measured relative changes in SF6 and He washout. SBW tests were repeatable and reproducible in healthy adults. We have developed a fast, reliable, and straightforward USFM based SBW method, which provides valid information on SF6 and He washout patterns during tidal breathing.