Coping with COVID-19: ventilator splitting with differential driving pressures using standard hospital equipment.

The global COVID-19 pandemic has led to a worldwide shortage of ventilators. This shortage has initiated discussions on how to support multiple patients with a single ventilator (ventilator splitting). Ventilator splitting is incompletely tested, experimental and the effects have not been fully characterised. This study investigated the effect of ventilator splitting on system variables (inspiratory pressure, flow and volume) and the possibility of different ventilation targets for each limb using only standard hospital equipment. Experiments were conducted on two test lungs with different compliances (0.02 l.cmH2 O-1 and 0.04 l.cmH2 O-1 ). The ventilator was used in both pressure and volume control modes and was set to ventilate the low compliance lungs at end-tidal volumes of 500 ± 20 ml. A flow restrictor apparatus consisting of a Hoffman clamp and tracheal tube was connected in series to the inspiratory limb of the high compliance test lungs and the resistance modified to achieve end-tidal volumes of 500 ± 20 ml. The restriction apparatus successfully modified the inspiratory pressure, minute ventilation and volume delivered to the high compliance test lungs in both pressure control (27.3-17.8 cmH2 O, 15.2-8.0 l.min-1 and 980-499 ml, respectively) and volume control (21.0-16.7 cmH2 O, 10.7-7.9 l.min-1 and 659-498 ml, respectively) ventilation modes. Ventilator splitting is not condoned by the authors. However, these experiments demonstrate the capacity to simultaneously ventilate two test lungs of different compliances, and using only standard hospital equipment, modify the delivered pressure, flow and volume in each test lung.

Is bigger really better? Towards improved models for testing how Atlantic salmon Salmo salar smolt size affects marine survival.

A general framework is presented that should enhance our understanding of how intrinsic factors, such as body size, and extrinsic factors, such as climate, affect the dynamics and demographics of fish populations. Effects of intrinsic factors, notably studies relating juvenile Atlantic salmon Salmo salar body size to their probability to return as an adult, are often context-dependent and anecdotal, due to data constraints. By merit of its flexible specification, this framework should admit datasets with a range of situation-specific nuances, collected using different approaches, and thereby deliver more general and robust findings for more effective population management.

Hydrodynamic evaluation of aortic cardiopulmonary bypass cannulae using particle image velocimetry.

The high velocity jet from aortic arterial cannulae used during cardiopulmonary bypass potentially causes a "sandblasting" injury to the aorta, increasing the possibility of embolisation of atheromatous plaque. We investigated a range of commonly available dispersion and non-dispersion cannulae, using particle image velocimetry. The maximum velocity of the exit jet was assessed 20 and 40 mm from the cannula tip at flow rates of 3 and 5 L/min. The dispersion cannulae had lower maximum velocities compared to the non-dispersion cannulae. Dispersion cannulae had fan-shaped exit profiles and maximum velocities ranged from 0.63 to 1.52 m/s when measured at 20 mm and 5 L/min. Non-dispersion cannulae had maximum velocities ranging from 1.52 to 3.06 m/s at 20 mm and 5 L/min, with corresponding narrow velocity profiles. This study highlights the importance of understanding the hydrodynamic performance of these cannulae as it may help in selecting the most appropriate cannula to minimize the risk of thromboembolic events or aortic injury.

Numerical Simulation of a Biventricular Assist Device with Fixed Right Outflow Cannula Banding During Pulmonary Hypertension.

As a left ventricular assist device is designed to pump against the systemic vascular resistance (SVR), pulmonary congestion may occur when using such device for right ventricular support. The present study evaluates the efficacy of using a fixed right outflow banding in patients receiving biventricular assist device support under various circulatory conditions, including variations in the SVR, pulmonary vascular resistance (PVR), total blood volume (BV), as well as ventricular contractility. Effect of speed variation on the hemodynamics was also evaluated at varying degrees of PVR. Pulmonary congestion was observed at high SVR and BV. A reduction in right ventricular assist device (RVAD) speed was required to restore pulmonary pressures. Meanwhile, at a high PVR, the risk of ventricular suction was prevalent during systemic hypotension due to low SVR and BV. This could be compensated by increasing RVAD speed. Isolated right heart recovery may aggravate pulmonary congestion, as the failing left ventricle cannot accommodate the resultant increase in the right-sided flow. Compared to partial assistance, the sensitivity of the hemodynamics to changes in VAD speed increased during full assistance. In conclusion, our results demonstrated that the introduction of a banding graft with a 5 mm diameter guaranteed sufficient reserve of the pump speed spectrum for the regulation of acceptable hemodynamics over different clinical scenarios, except under critical conditions where drug administration or volume management is required.

"Of mind, body, and spirit": therapeutic foster care--an innovative approach to healing from an NTU perspective.

This article examines Progressive Life Center's (PLC) innovative Therapeutic Foster Care (TFC) program, and its incorporation of a unique clinical approach, NTU (pronounced in-to) psychotherapy, into its program model. PLC is an African American private nonprofit community-based organization that strives to improve the delivery of mental health services through culturally competent therapeutic techniques. PLC expanded its services to include TFC for seriously emotionally disturbed children, ages 2 to 18. All PLC services are delivered within the spiritual and cultural framework of NTU.

Does selective attention influence the brain-stem auditory evoked potential?

We have re-examined the problem of selective attention in relation to brain-stem auditory evoked potentials (BAEPs). We compared BAEPs recorded in the relaxed individual with those elicited during visual attention and during auditory attention. Particular emphasis was placed on the use of a demanding visual task to ensure appropriately sustained levels of concentration by the subject for the durations of the tests. We measured the latency of wave I, the wave I-V interval and the amplitudes of waves I and V in 16 subjects in each of the conditions but could find no effect attributable to changes in states of attention. We conclude that there is no evidence for the actions of gating or switching mechanisms at early stages of the auditory pathways.