Measurement of skeletal muscle glucose uptake in mice in response to acute treadmill running.

Skeletal muscle contractions stimulate glucose uptake into the working muscles during exercise. Because this signaling pathway is independent of insulin, exercise constitutes an important alternative pathway to increase glucose uptake, also in insulin-resistant muscle. Therefore, much effort is being put into understanding the molecular regulation of exercise-stimulated glucose uptake by skeletal muscle. To delineate the causal molecular mechanisms whereby muscle contraction or exercise regulate glucose uptake, the investigation of genetically manipulated rodents is necessary. Presented here is a modified and optimized protocol assessing exercise-induced muscle glucose uptake in mice in response to acute treadmill running. Using this high-throughput protocol, running capacity can accurately and reproducibly be determined in mice, and basal- and exercise-stimulated skeletal muscle glucose uptake and intracellular signaling can precisely and dose-dependently be measured in awake mice in vivo without the need for catheterization and with minimal loss of blood.

Transesophageal echocardiography in swine: evaluation of left and right ventricular structure, function and myocardial work.

This study aimed to determine standard left (LV) and right ventricular (RV) transesophageal echocardiographic (TEE) measurements in swine. Additionally, global myocardial work index (GWI) was estimated using pressure-strain loops (PSL). A comprehensive TEE examination was conducted in ten anesthetized, intubated and mechanically ventilated healthy female German landrace swine, weighing 44 to 57 kg. For GWI calculation, we performed LV and RV segmental strain analysis and used invasively measured LV and RV pressure to obtain PSL. The GWI and further myocardial work indices were calculated from the area of the PSL using commercially available software. Furthermore, hemodynamic measurements were obtained using indwelling catheters. We obtained complete standardized baseline values for left and right ventricular dimensions and function. Biplane LV ejection fraction was 63 ± 7 % and the LV end-diastolic volume was 70.5 ± 5.9 ml. Tissue Doppler estimated peak tricuspid annular systolic velocity was 13.1 ± 1.8 cm/s. The Doppler estimated LV and RV stroke volume index were 75.6 ± 7.2 ml/m2 and 76.7 ± 7.8 ml/m2 respectively. Pulsed wave Doppler derived cardiac output correlated well with cardiac output estimated using the thermodilution method (7.0 ± 1.2 l/min vs. 7.0 ± 1.1 l/min, r = 0.812, p = 0.004). The LV global longitudinal strain was -21.3 ± 3.9 % and the RV global longitudinal strain was -15.4 ± 2.5 %. LV GWI was 1885(1281-2121) mmHg*% and 297 ± 62 mmHg*% for the RV. LV global myocardial work efficiency was 82.6 ± 4 % and 83(72-88) % for the RV. TEE offers sufficient morphological, functional and hemodynamic assessment of the heart in swine. Myocardial contractility and mechanics can be reliably evaluated with the non-invasive GWI derived from echocardiography without additional invasive measures.

Is Systolic Right Ventricular Function Reduced after Thoracic Non-Cardiac Surgery? A Propensity Matched Echocardiographic Analysis.

PURPOSE: To assess whether thoracic non-cardiac surgery has an influence on right ventricular function (RVF) compared to known impaired postoperative RV function after cardiac surgery. METHODS: In all, 50 patients (mean age: 61 years), who underwent thoracic non-cardiac surgery were included and matched using propensity score to 50 patients, receiving coronary artery bypass graft surgery (CABG) (CABGmatched). All patients had transthoracic echocardiography (TTE) including two-dimensional speckle tracking (2D-STE) and tissue Doppler imaging (TDI) pre- and 1 week postoperatively. RESULTS: No significant changes in RV measurements including tricuspid annular plane systolic excursion (TAPSE), tricuspid annular systolic velocity (TASV), RV fractional area change (RV-FAC), and 2D-STE of the RV and RV freewall within the thoracic non-cardiac surgery patients comparing pre- and postoperative values. Comparing RV TTE values between CABGmatched patients and thoracic surgery patients, only TAPSE differed between groups preoperatively (p <0.0001), where postoperatively, all RV measurements differed significantly between the two groups: TAPSE (p <0.0001), TASV (p <0.001), RVFAC (p = 0.005), and RV 2D-STE (p <0.0001) indicating impairment of RV function post-CABG surgery compared to thoracic non-cardiac surgery. CONCLUSION: Thoracic non-cardiac surgery including an opening of the pleural cavity did not influence RV function early postoperative, whereas CABG surgery with pericardiotomy led to an impaired global RV function.

Acceleration sensors in abdominal wall position as a non-invasive approach to detect early breathing alterations induced by intolerance of increased airway resistance.

BACKGROUND: Early detection of respiratory overload is crucial to mechanically ventilated patients, especially during phases of spontaneous breathing. Although a diversity of methods and indices has been established, there is no highly specific approach to predict respiratory failure. This study aimed to evaluate acceleration sensors in abdominal and thoracic wall positions to detect alterations in breathing excursions in a setting of gradual increasing airway resistance. METHODS: Twenty-nine healthy volunteers were committed to a standardized protocol of a two-minutes step-down spontaneous breathing on a 5 mm, 4 mm and then 3 mm orally placed endotracheal tube. Accelerator sensors in thoracic and abdominal wall position monitored breathing excursions. 15 participants passed the breathing protocol ("completed" group), 14 individuals cancelled the protocol due to subjective intolerance to the increasing airway resistance ("abandoned" group). RESULTS: Gradual increased respiratory workload led to a significant decrease of acceleration in abdominal wall position in the "abandoned" group compared to the "completed" group (p < 0.001), while these gradual accelerating changes were not observed in thoracic wall position (p = 0.484). Thoracic acceleration sensors did not detect any time- and group-specific changes (p = 0.746). CONCLUSIONS: The abdominal wall position of the acceleration sensors may be a non-invasive, economical and practical approach to detect early breathing alterations prior to respiratory failure. TRIAL REGISTRATION: EK 309-15; by the Ethics Committee of the Faculty of Medicine, RWTH Aachen, Aachen, Germany. Retrospectively registered 28th of December 2015.