Proportional Ventilatory Support: A Comparison of Proportional Assist Ventilation, Proportional Pressure Support and Proportional Pressure Ventilation

Background: Proportional ventilatory support (PVS) refers to modes of ventilation that provide support that is proportional to the patient\u27s inspiratory effort. Research has shown that PVS improves patient ventilator synchrony. Several ventilators are now available that provide a type of PVS. The purpose of this study was to evaluate Proportional Assist Ventilation (PAV+) on the PB 840 and PB 980, Proportional Pressure Ventilation (PPV) on the Respironics V60, and Proportional Pressure Support (PPS) on the Drager V500, using the IngMar Medical ASL 5000 (ASL) at three different inspiratory efforts (Pmus). Methods: The ASL was set to simulate a COPD lung model: compliance 59 mL/cmH2O; resistance in 22 cmH2O/L/s; resistance out 18 cmH2O/L/s; respiratory rate 14 bpm; Pmus 12 cmH2O. Ventilator settings: PAV+ % Supp 25%, 45%, and 65%, Esens 3 LPM; PPV 25%, 45%, and 65%, Max E 17 cmH2O/L, Max R 20 cmH2O/L/s; PPS flow assist 25%, 45%, and 65% of the averaged resistance, volume assist 25%, 45% and 65% of the elastance, inspiratory termination 25%; PEEP 7 cmH2O. Each ventilator was connected to the ASL using a 7.5 mm ETT. After the ventilator was connected, the mode was run at ventilator support (VS) 25%. The ventilator was given one minute after the change had been made to stabilize; data was gathered for an additional minute using the automated ASL software. Next VS was increased to 45% and 65%, following the same procedure. Then, Pmus was increased to 18 and 24 cmH2O, gathering data as described, at each level of VS. Results: As VS increased, tidal volume (VT) and peak inspiratory pressure (PIP) increased on all ventilators. As VS increased, time to trigger (TT) decreased on all ventilators. As Pmus increased, TT increased. On the PB 840, PB 980 and V500, as VS increased, inspiratory time (Ti) increased; conversely, on the V60 as VS increased, Ti decreased. The PB 980 had the highest average Ti, VT, PIP, and TT. Ti on the PB 980 increased due to multiple inspiratory pauses, which resulted in AutoPEEP. The V60 had the shortest TT. Conclusion: This study demonstrated that PAV+, PPV, and PPS each provide an increase in VT and PIP as patient effort or VS increases. Using PPV and PPS requires the clinician to know the resistance and elastance of the lung. Clinicians need to be careful to input the value for elastance, not compliance. Further research needs to compare PVS in patients to determine the clinical benefit of each mode

Simulation, modelling and development of the metris RCA

In partnership with Metris UK we discuss the utilisation of modelling and simulation methods in the development of a revolutionary 7-axis Robot CMM Arm (RCA). An offline virtual model is described, facilitating pre-emptive collision avoidance and assessment of optimal placement of the RCA relative to scan specimens. Workspace accessibility of the RCA is examined under a range of geometrical assumptions and we discuss the effects of arbitrary offsets resulting from manufacturing tolerances. Degeneracy is identified in the number of ways a given pose may be attained and it is demonstrated how a simplified model may be exploited to solve the inverse kinematics problem of finding the “correct” set of joint angles. We demonstrate how the seventh axis may be utilised to avoid obstacles or otherwise awkward poses, giving the unit greater dexterity than traditional CMMs. The results of finite element analysis and static force modelling on the RCA are presented which provide an estimate of the forces exerted on the internal measurement arm in a range of poses

Characteristics, accuracy and reverification of robotised articulated arm CMMs

VDI article 2617 specifies characteristics to describe the accuracy of articulated arm coordinate measuring machines (AACMMs) and outlines procedures for checking them. However the VDI prescription was written with a former generation of machines in mind: manual arms exploiting traditional touch probe technologies. Recent advances in metrology have given rise to noncontact laser scanning tools and robotic automation of articulated arms – technologies which are not adequately characterised using the VDI specification. In this paper we examine the “guidelines” presented in VDI 2617, finding many of them to be ambiguous and open to interpretation, with some tests appearing even to be optional. The engineer is left significant flexibility in the execution of the test procedures and the manufacturer is free to specify many of the test parameters. Such flexibility renders the VDI tests of limited value and the results can be misleading. We illustrate, with examples using the Nikon RCA, how a liberal interpretation of the VDI guidelines can significantly improve accuracy characterisation and suggest ways in which to mitigate this problem. We propose a series of stringent tests and revised definitions, in the same vein as VDI 2617 and similar US standards, to clarify the accuracy characterisation process. The revised methodology includes modified acceptance and reverification tests which aim to accommodate emerging technologies, laser scanning devices in particular, while maintaining the spirit of the existing and established standards. We seek to supply robust re-definitions for the accepted terms “zero point” and “useful arm length”, pre-supposing nothing about the geometry of the measuring device. We also identify a source of error unique to robotised AACMMs employing laser scanners – the forward-reverse pass error. We show how eliminating this error significantly improves the repeatability of a device and propose a novel approach to the testing of probing error based on statistical uncertainty

Fast Adaptive Voltage and Boost Frequencies for Central Processing Units

This publication describes methods, techniques, and apparatuses that enable a user equipment (UE) to quickly increase or lower the supply voltage and/or the clock frequency to handle changes in load operating conditions of the components of a system on chip (SoC). The UE uses a dynamic voltage and frequency scaling (DVFS) to handle changes in load operating conditions. During the DVFS, an application processor (AP) writes the supply voltage and the clock frequency settings to shared memory between the SoC, the AP, and a microcontroller unit (MCU). The MCU, then, can change the supply voltage using a voltage controller and/or change the clock frequency using a clock controller, which includes multiple phase-locked loops (PLLs). The utilization of a clock controller with multiple PLLs enables the MCU to trigger a switch between preset clock frequencies much faster than when using a clock controller with a single PLL. Further, the MCU can anticipate the load operating conditions of the components of the SoC and can quickly adjust the supply voltage and the clock frequency settings to run the anticipated load, enabling the UE to save power and increase performance

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