Can Transthoracic Echocardiography Be Used to Predict Fluid Responsiveness in the Critically Ill Patient? A Systematic Review

Introduction. We systematically evaluated the use of transthoracic echocardiography in the assessment of dynamic markers of preload to predict fluid responsiveness in the critically ill adult patient. Methods. Studies in the critically ill using transthoracic echocardiography (TTE) to predict a response in stroke volume or cardiac output to a fluid load were selected. Selection was limited to English language and adult patients. Studies on patients with an open thorax or abdomen were excluded. Results. The predictive power of diagnostic accuracy of inferior vena cava diameter and transaortic Doppler signal changes with the respiratory cycle or passive leg raising in mechanically ventilated patients was strong throughout the articles reviewed. Limitations of the technique relate to patient tolerance of the procedure, adequacy of acoustic windows, and operator skill. Conclusions. Transthoracic echocardiographic techniques accurately predict fluid responsiveness in critically ill patients. Discriminative power is not affected by the technique selected

Transthoracic Echocardiographic Assessment of the Heart in Pregnancy-a position statement on behalf of the British Society of Echocardiography and the United Kingdom Maternal Cardiology Society.

Pregnancy is a dynamic process associated with profound hormonally mediated haemodynamic changes which result in structural and functional adaptations in the cardiovascular system. An understanding of the myocardial adaptations is important for echocardiographers and clinicians undertaking or interpreting echocardiograms on pregnant and post-partum women. This guideline, on behalf of the British Society of Echocardiography and United Kingdom Maternal Cardiology Society, reviews the expected echocardiographic findings in normal pregnancy and in different cardiac disease states, as well as echocardiographic signs of decompensation. It aims to lay out a structure for echocardiographic scanning and surveillance during and after pregnancy as well as suggesting practical advice on scanning pregnant women

Use of helium-oxygen mixture in adult patients presenting with exacerbations of asthma and chronic obstructive pulmonary disease: a systematic review.

We examined systematically all controlled and cross-over randomised trials in patients with acute exacerbations of asthma and chronic obstructive pulmonary disease comparing Heliox against air-oxygen mixtures. Fourteen studies were identified. In asthma studies, peak expiratory flow rate (PEFR) was increased by an average of 29.6% (95% CI 16.6-42.6) by Heliox-driven nebulisers, or by 13.3 l.min(-1) (95% CI 3.71-22.81) absolute. In studies of patients with chronic obstructive pulmonary disease receiving non-invasive ventilation the arterial carbon dioxide tension (P(a)co(2)) and respiratory rate were unchanged: weighted mean difference for P(a)co(2)-0.29kPa (95% CI - 0.64-0.07) favoured Heliox, and for respiratory rate 1.6 breaths.min(-1) (95% CI - 0.93, 4.14) favoured control. Heliox minimally reduced the work of breathing in intubated patients, and reduced intrinsic positive end expiratory pressure (iPEEP). The use of Heliox to drive nebulisers in patients with acute asthma slightly improves airflow measures. We were unable to determine whether this improved recovery

The assessment of left ventricular diastolic function: guidance and recommendations from the British Society of Echocardiography

Impairment of left ventricular (LV) diastolic function is common amongst those with left heart disease and is associated with significant morbidity. Given that, in simple terms, the ventricle can only eject the volume with which it fills and that approximately one half of hospitalisations for heart failure (HF) are in those with normal/'preserved' left ventricular ejection fraction (HFpEF) (Bianco et al. in JACC Cardiovasc Imaging. 13:258-271, 2020. 10.1016/j.jcmg.2018.12.035), where abnormalities of ventricular filling are the cause of symptoms, it is clear that the assessment of left ventricular diastolic function (LVDF) is crucial for understanding global cardiac function and for identifying the wider effects of disease processes. Invasive methods of measuring LV relaxation and filling pressures are considered the gold-standard for investigating diastolic function. However, the high temporal resolution of trans-thoracic echocardiography (TTE) with widely validated and reproducible measures available at the patient's bedside and without the need for invasive procedures involving ionising radiation have established echocardiography as the primary imaging modality. The comprehensive assessment of LVDF is therefore a fundamental element of the standard TTE (Robinson et al. in Echo Res Pract7:G59-G93, 2020. 10.1530/ERP-20-0026). However, the echocardiographic assessment of diastolic function is complex. In the broadest and most basic terms, ventricular diastole comprises an early filling phase when blood is drawn, by suction, into the ventricle as it rapidly recoils and lengthens following the preceding systolic contraction and shortening. This is followed in late diastole by distension of the compliant LV when atrial contraction actively contributes to ventricular filling. When LVDF is normal, ventricular filling is achieved at low pressure both at rest and during exertion. However, this basic description merely summarises the complex physiology that enables the diastolic process and defines it according to the mechanical method by which the ventricles fill, overlooking the myocardial function, properties of chamber compliance and pressure differentials that determine the capacity for LV filling. Unlike ventricular systolic function where single parameters are utilised to define myocardial performance (LV ejection fraction (LVEF) and Global Longitudinal Strain (GLS)), the assessment of diastolic function relies on the interpretation of multiple myocardial and blood-flow velocity parameters, along with left atrial (LA) size and function, in order to diagnose the presence and degree of impairment. The echocardiographic assessment of diastolic function is therefore multifaceted and complex, requiring an algorithmic approach that incorporates parameters of myocardial relaxation/recoil, chamber compliance and function under variable loading conditions and the intra-cavity pressures under which these processes occur. This guideline outlines a structured approach to the assessment of diastolic function and includes recommendations for the assessment of LV relaxation and filling pressures. Non-routine echocardiographic measures are described alongside guidance for application in specific circumstances. Provocative methods for revealing increased filling pressure on exertion are described and novel and emerging modalities considered. For rapid access to the core recommendations of the diastolic guideline, a quick-reference guide (additional file 1) accompanies the main guideline document. This describes in very brief detail the diastolic investigation in each patient group and includes all algorithms and core reference tables

Centroid Localization of Uncooperative Nodes in Wireless Networks Using a Relative Span Weighting Method

Increasingly ubiquitous wireless technologies require novel localization techniques to pinpoint the position of an uncooperative node, whether the target is a malicious device engaging in a security exploit or a low-battery handset in the middle of a critical emergency. Such scenarios necessitate that a radio signal source be localized by other network nodes efficiently, using minimal information. We propose two new algorithms for estimating the position of an uncooperative transmitter, based on the received signal strength (RSS) of a single target message at a set of receivers whose coordinates are known. As an extension to the concept of centroid localization, our mechanisms weigh each receiver's coordinates based on the message's relative RSS at that receiver, with respect to the span of RSS values over all receivers. The weights may decrease from the highest RSS receiver either linearly or exponentially. Our simulation results demonstrate that for all but the most sparsely populated wireless networks, our exponentially weighted mechanism localizes a target node within the regulations stipulated for emergency services location accuracy