Analysis and applications of respiratory surface EMG:report of a round table meeting

Surface electromyography (sEMG) can be used to measure the electrical activity of the respiratory muscles. The possible applications of sEMG span from patients suffering from acute respiratory failure to patients receiving chronic home mechanical ventilation, to evaluate muscle function, titrate ventilatory support and guide treatment. However, sEMG is mainly used as a monitoring tool for research and its use in clinical practice is still limited—in part due to a lack of standardization and transparent reporting. During this round table meeting, recommendations on data acquisition, processing, interpretation, and potential clinical applications of respiratory sEMG were discussed. This paper informs the clinical researcher interested in respiratory muscle monitoring about the current state of the art on sEMG, knowledge gaps and potential future applications for patients with respiratory failure.</p

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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Droplets and outgrowths on high-Tc laser ablated thin films

YBa2Cu30x thin films have been grown on silicon, SrTi03 and Zr02 substrates using the pulsed laser deposition technique. Special attention has been paid to droplets and outgrowths which appear on the thin films during the growth process. The droplet density was studied as a function of the laser spot size, the laser energy and the target density. The number of droplets could be reduced to 1 per 100 μm2 for a 100 nm thick film, by ta1cing a large laser spot size and low energy density. The droplet density does not depend on the target density in the range from 80 to 94 % . The number of outgrowths could be reduced to 1 per 100 μm2 for a 100 nm thick film by reducing the deposition temperature or increasing the laser frequency. However, the critical temperature of these layers was reduced by 5 to 10 K. Using SAM no differences in composition between an outgrowth and the rest of the film could be detected

New type of wasted effort during neurally adjusted ventilatory assist: A case report

In patients with dynamic hyperinflation, such as patients with chronic obstructive pulmonary disease (COPD), development of intrinsic positive end-expiratory pressure (PEEPi) complicates ventilator triggering in conventional assisted ventilation modes, such as pressure support, and causes wasted efforts. The use of extrinsic PEEP (PEEPe) can counterbalance PEEPi and as such facilitate triggering. With neurally adjusted ventilatory assist (NAVA) the ventilator is triggered by an increase in diaphragm electrical activity and does not depend on generation of inspiratory flow. Numerous studies report the absence of ‘classical’ wasted efforts with NAVA. Therefore, the widespread assumption among physicians is that wasted efforts cannot occur with NAVA. We present a 58-year-old male with an acute exacerbation of COPD in which we identify a new type of wasted effort unique to NAVA. We show that during NAVA in the presence of PEEPi it is as important to perform titration of PEEPe as with conventional modes, in order to prevent wasted efforts

Droplets and outgrowths on high-Tc laser ablated thin films

YBa2Cu30x thin films have been grown on silicon, SrTi03 and Zr02 substrates using the pulsed laser deposition technique. Special attention has been paid to droplets and outgrowths which appear on the thin films during the growth process. The droplet density was studied as a function of the laser spot size, the laser energy and the target density. The number of droplets could be reduced to 1 per 100 μm2 for a 100 nm thick film, by ta1cing a large laser spot size and low energy density. The droplet density does not depend on the target density in the range from 80 to 94 % . The number of outgrowths could be reduced to 1 per 100 μm2 for a 100 nm thick film by reducing the deposition temperature or increasing the laser frequency. However, the critical temperature of these layers was reduced by 5 to 10 K. Using SAM no differences in composition between an outgrowth and the rest of the film could be detected

Partial Neuromuscular Blockade during Partial Ventilatory Support in Sedated Patients with High Tidal Volumes

RATIONALE: Controlled mechanical ventilation is used to deliver lung-protective ventilation in patients with acute respiratory distress syndrome. Despite recognized benefits, such as preserved diaphragm activity, partial support ventilation modes may be incompatible with lung-protective ventilation due to high Vt and high transpulmonary pressure. As an alternative to high-dose sedatives and controlled mechanical ventilation, pharmacologically induced neuromechanical uncoupling of the diaphragm should facilitate lung-protective ventilation under partial support modes. OBJECTIVES: To investigate whether partial neuromuscular blockade can facilitate lung-protective ventilation while maintaining diaphragm activity under partial ventilatory support. METHODS: In a proof-of-concept study, we enrolled 10 patients with lung injury and a Vt greater than 8 ml/kg under pressure support ventilation (PSV) and under sedation. After baseline measurements, rocuronium administration was titrated to a target Vt of 6 ml/kg during neurally adjusted ventilatory assist (NAVA). Thereafter, patients were ventilated in PSV and NAVA under continuous rocuronium infusion for 2 hours. Respiratory parameters, hemodynamic parameters, and blood gas values were measured. MEASUREMENTS AND MAIN RESULTS: Rocuronium titration resulted in significant declines of Vt (mean ± SEM, 9.3 ± 0.6 to 5.6 ± 0.2 ml/kg; P < 0.0001), transpulmonary pressure (26.7 ± 2.5 to 10.7 ± 1.2 cm H2O; P < 0.0001), and diaphragm electrical activity (17.4 ± 2.3 to 4.5 ± 0.7 μV; P < 0.0001), and could be maintained under continuous rocuronium infusion. During titration, pH decreased (7.42 ± 0.02 to 7.35 ± 0.02; P < 0.0001), and mean arterial blood pressure increased (84 ± 6 to 99 ± 6 mm Hg; P = 0.0004), as did heart rate (83 ± 7 to 93 ± 8 beats/min; P = 0.0004). CONCLUSIONS: Partial neuromuscular blockade facilitates lung-protective ventilation during partial ventilatory support, while maintaining diaphragm activity, in sedated patients with lung injury

Assessment of dead-space ventilation in patients with acute respiratory distress syndrome: a prospective observational study

BACKGROUND: Physiological dead space (VD/VT) represents the fraction of ventilation not participating in gas exchange. In patients with acute respiratory distress syndrome (ARDS), VD/VT has prognostic value and can be used to guide ventilator settings. However, VD/VT is rarely calculated in clinical practice, because its measurement is perceived as challenging. Recently, a novel technique to calculate partial pressure of carbon dioxide in alveolar air (PACO2) using volumetric capnography (VCap) was validated. The purpose of the present study was to evaluate how VCap and other available techniques to measure PACO2 and partial pressure of carbon dioxide in mixed expired air (PeCO2) affect calculated VD/VT. METHODS: In a prospective, observational study, 15 post-cardiac surgery patients and 15 patients with ARDS were included. PACO2 was measured using VCap to calculate Bohr dead space or substituted with partial pressure of carbon dioxide in arterial blood (PaCO2) to calculate the Enghoff modification. PeCO2 was measured in expired air using three techniques: Douglas bag (DBag), indirect calorimetry (InCal), and VCap. Subsequently, VD/VT was calculated using four methods: Enghoff-DBag, Enghoff-InCal, Enghoff-VCap, and Bohr-VCap. RESULTS: PaCO2 was higher than PACO2, particularly in patients with ARDS (post-cardiac surgery PACO2 = 4.3 ± 0.6 kPa vs. PaCO2 = 5.2 ± 0.5 kPa, P < 0.05; ARDS PACO2 = 3.9 ± 0.8 kPa vs. PaCO2 = 6.9 ± 1.7 kPa, P < 0.05). There was good agreement in PeCO2 calculated with DBag vs. VCap (post-cardiac surgery bias = 0.04 ± 0.19 kPa; ARDS bias = 0.03 ± 0.27 kPa) and relatively low agreement with DBag vs. InCal (post-cardiac surgery bias = -1.17 ± 0.50 kPa; ARDS mean bias = -0.15 ± 0.53 kPa). These differences strongly affected calculated VD/VT. For example, in patients with ARDS, VD/VTcalculated with Enghoff-InCal was much higher than Bohr-VCap (VD/VT Enghoff-InCal = 66 ± 10 % vs. VD/VT Bohr-VCap = 45 ± 7 %; P < 0.05). CONCLUSIONS: Different techniques to measure PACO2 and PeCO2 result in clinically relevant mean and individual differences in calculated VD/VT, particularly in patients with ARDS. Volumetric capnography is a promising technique to calculate true Bohr dead space. Our results demonstrate the challenges clinicians face in interpreting an apparently simple measurement such as VD/VT