Effectiveness of a national quality improvement programme to improve survival after emergency abdominal surgery (EPOCH): a stepped-wedge cluster-randomised trial

Background: Emergency abdominal surgery is associated with poor patient outcomes. We studied the effectiveness of a national quality improvement (QI) programme to implement a care pathway to improve survival for these patients. Methods: We did a stepped-wedge cluster-randomised trial of patients aged 40 years or older undergoing emergency open major abdominal surgery. Eligible UK National Health Service (NHS) hospitals (those that had an emergency general surgical service, a substantial volume of emergency abdominal surgery cases, and contributed data to the National Emergency Laparotomy Audit) were organised into 15 geographical clusters and commenced the QI programme in a random order, based on a computer-generated random sequence, over an 85-week period with one geographical cluster commencing the intervention every 5 weeks from the second to the 16th time period. Patients were masked to the study group, but it was not possible to mask hospital staff or investigators. The primary outcome measure was mortality within 90 days of surgery. Analyses were done on an intention-to-treat basis. This study is registered with the ISRCTN registry, number ISRCTN80682973. Findings: Treatment took place between March 3, 2014, and Oct 19, 2015. 22 754 patients were assessed for elegibility. Of 15 873 eligible patients from 93 NHS hospitals, primary outcome data were analysed for 8482 patients in the usual care group and 7374 in the QI group. Eight patients in the usual care group and nine patients in the QI group were not included in the analysis because of missing primary outcome data. The primary outcome of 90-day mortality occurred in 1210 (16%) patients in the QI group compared with 1393 (16%) patients in the usual care group (HR 1·11, 0·96–1·28). Interpretation: No survival benefit was observed from this QI programme to implement a care pathway for patients undergoing emergency abdominal surgery. Future QI programmes should ensure that teams have both the time and resources needed to improve patient care. Funding: National Institute for Health Research Health Services and Delivery Research Programme

Effectiveness of a national quality improvement programme to improve survival after emergency abdominal surgery (EPOCH): a stepped-wedge cluster-randomised trial

BACKGROUND: Emergency abdominal surgery is associated with poor patient outcomes. We studied the effectiveness of a national quality improvement (QI) programme to implement a care pathway to improve survival for these patients. METHODS: We did a stepped-wedge cluster-randomised trial of patients aged 40 years or older undergoing emergency open major abdominal surgery. Eligible UK National Health Service (NHS) hospitals (those that had an emergency general surgical service, a substantial volume of emergency abdominal surgery cases, and contributed data to the National Emergency Laparotomy Audit) were organised into 15 geographical clusters and commenced the QI programme in a random order, based on a computer-generated random sequence, over an 85-week period with one geographical cluster commencing the intervention every 5 weeks from the second to the 16th time period. Patients were masked to the study group, but it was not possible to mask hospital staff or investigators. The primary outcome measure was mortality within 90 days of surgery. Analyses were done on an intention-to-treat basis. This study is registered with the ISRCTN registry, number ISRCTN80682973. FINDINGS: Treatment took place between March 3, 2014, and Oct 19, 2015. 22 754 patients were assessed for elegibility. Of 15 873 eligible patients from 93 NHS hospitals, primary outcome data were analysed for 8482 patients in the usual care group and 7374 in the QI group. Eight patients in the usual care group and nine patients in the QI group were not included in the analysis because of missing primary outcome data. The primary outcome of 90-day mortality occurred in 1210 (16%) patients in the QI group compared with 1393 (16%) patients in the usual care group (HR 1·11, 0·96-1·28). INTERPRETATION: No survival benefit was observed from this QI programme to implement a care pathway for patients undergoing emergency abdominal surgery. Future QI programmes should ensure that teams have both the time and resources needed to improve patient care. FUNDING: National Institute for Health Research Health Services and Delivery Research Programme

Numerical Study of the Laminar Flow Past a Rotating Square Cylinder at Low Spinning Rates

The fluid dynamic interaction between a uniform free stream flow and the rotation induced flow from a sharp edged body is numerically investigated. A two-dimensional (2D) finite volume based computation is performed in this regard to simulate the laminar fluid flow around a rotating square cylinder in an unconfined medium. Body fitted grid system along with moving boundaries is used to obtain the numerical solution of the incompressible Navier–Stokes equations. The Reynolds number based on the free stream flow is kept in the range 10≤Re≤20010≤Re≤200 with a dimensionless rotational speed of the cylinder in the range 0≤Ω≤50≤Ω≤5. At low Re=10Re=10, the flow field remains steady irrespective of the rotational speed. For 50≤Re≤20050≤Re≤200, regular low frequency Kármán vortex shedding (VS) is observed up to a critical rate of rotation (ΩcrΩcr). Beyond ΩcrΩcr, the global flow shows steady nature, although high frequency oscillations in the aerodynamic coefficients are present. The rotating circular cylinder also shows likewise degeneration of Kármán VS at some critical rotational speed. However, significant differences can be seen at higher rotation. Such fluid dynamic transport around a spinning square in an unconfined free stream flow is reported for the first time

Convective transport around rows of square cylinders arranged in a staggered fashion at moderate Reynolds number

The thermohydrodynamic interactions among multiple bodies fixed in an incident flow are analyzed through two-dimensional numerical computation. The bodies are identical in shape and size with square cross section and arranged in two rows in a staggered fashion within an unconfined domain. Simulation is carried out using a finite-volume-based method considering a uniform cross flow of air (Prandtl number, Pr =0.71) at a moderate Reynolds number (Re = 100). Apart from the Reynolds number, certain geometrical parameters such as the streamwise and transverse spacing of the objects may significantly influence the wake dynamics, vortex structure formation, and the associated thermal transport. Accordingly, both the dimensionless transverse spacing (S/d = 1, 3, and 5, with S and d the transverse spacing and cylinder size, respectively) and the nondimensional streamwise gap (L/d = 1, 3, and 5, with L being the streamwise gap) are varied to elucidate their roles in controlling the hydrodynamic and thermal transport. Even at such a moderate Reynolds number, the flow and thermal fields show chaotic behavior at smaller transverse spacing, this behavior being established through various chaos characterization tools. However, at larger spacing, the usual unsteady vortex dynamics persists. Shedding in the gap is inhibited at smaller streamwise spacing. Again, at larger spacing, the normal shedding characteristics continue. Average heat transfer from the cylinders is higher at smaller streamwise and transverse spacing

Hydromagnetic Mixed Convective Transport in a Nonisothermally Heated Lid-Driven Square Enclosure Including a Heat-Conducting Circular Cylinder

A two-dimensional numerical study is performed in an effort to understand the fundamental characteristics of hydromagnetic mixed convective transport in a nonisothermally heated vertical lid-driven square enclosure filled with an electrically conducting fluid in the presence of a heat-conducting solid circular cylinder. Additionally, entropy generation due to heat transfer, fluid friction, and magnetic effect is also determined. Simulations are performed for various controlling parameters such as the Richardson number (1 ≤ Ri ≤ 10), Hartmann number (0 ≤ Ha ≤ 50), Prandtl number (0.02 ≤ Pr ≤ 7), Reynolds number based on the lid velocity (Re = 100, 150, and 200), and amplitude of the sinusoidal function (A = 0.25, 0.5, and 1), keeping the solid–fluid thermal conductivity ratio fixed as K = 5. The flow and thermal fields are analyzed through streamline and isotherm plots for various Ha, Ri, Re, and Pr. Furthermore, the drag coefficient on the moving lid and Nusselt numbers on heated surfaces are also computed to understand the effects of Ha, Ri, Re, Pr, and n on them. It is observed that the drag on the moving lid decreases with Re and increases with Ri and Ha, however, remains insensitive with Pr. The heat-transfer rate from the hot right wall increases as usual with Re, Pr, and Ri but decreases with Ha. The sinusoidally heated bottom wall shows a decrease in the heat-transfer rate with increasing Pr, and at higher Pr, it also decreases with Re. Furthermore, increasing magnetic field strength causes an increase in the heat-transfer rate from the bottom wall. It also decreases with decreasing value of the amplitude of the sinusoidal function

MHD flow and heat transfer behind a square cylinder in a duct under strong axial magnetic field

We capture through numerical simulation the MHD (magnetohydrodynamic) vortex dynamics around a square object in a square duct subjected to a strong externally imposed axial magnetic field. A quasi two-dimensional conditionality allows us to follow a two-dimensional modeling approach. The pertinent MHD control parameters such as the Reynolds and Hartmann numbers are kept in the range 0<Re⩽6000 and 0<Ha⩽2160, respectively. The various regimes of the MHD wake are found in-line with those obtained by Dousset and Pothérat under similar conditions using a circular object (Dousset and Pothérat, 2008). Four different regimes are identified out of which the first three regimes are the classical non-MHD 2D cylinder wakes. The transition from one to another regime is controlled by the friction parameter Re/Ha. The fourth regime is characterized by the vortices evolved from the duct side walls due to the boundary layer separation which strongly disturbs the Kármán vortex street. In order to explore the thermal transport phenomena under the action of the axially imposed magnetic field, the channel bottom wall is considered heated while the top wall is maintained at the free stream temperature keeping the cylinder adiabatic. The heat transfer rate from the heated channel wall strongly depends on the imposed magnetic field strength as well as Reynolds number. Additionally, an enhancement in heat transfer is experienced by placing the square cylinder in the channel over the bare channel, however, simultaneously a degradation in heat transfer would occur if the square object is replaced by a same size circular object

Magnetohydrodynamic Natural Convection in a Square Enclosure with Four Circular Cylinders Positioned at Different Rectangular Locations

We deploy a finite volume numerical computation to investigate the two-dimensional hydromagnetic natural convection in a cooled square enclosure in the presence of four inner heated circular cylinders with identical shape. The inner circular cylinders are placed in a rectangular array with equal distance away from each other within the enclosure and moving along the diagonals of the enclosure. All the walls of the enclosure are kept isothermal with temperatures less than that of the cylinders. A uniform magnetic field is applied along the horizontal direction normal to the vertical wall. All solid walls are assumed electrically insulated. Simulations are performed for a range of the controlling parameters such as the Rayleigh number 103 to 106, Hartmann number 0 to 50, and the dimensionless horizontal and vertical distance from the center of a cylinder to center of another cylinder 0.3 to 0.7. The study specifically aims to understand the effects of the location of the cylinders in the enclosure on the magnetoconvective transport, when they moved along the diagonals of the enclosure. It is observed that the unsteady behavior of the flow and thermal fields at relatively larger Rayleigh numbers and for some cylinder position are suppressed by imposition of the magnetic field. The heat transfer strongly depends on the position of the cylinders and the strength of the magnetic field. Hence, by controlling the position of the objects and the magnetic field strength, a significant control on the hydrodynamic and thermal transport can be achieved

Convective transport around a rotating square cylinder at moderate Reynolds numbers

Two-dimensional numerical simulation is performed to analyze the thermofluidic transport around a rotating square cylinder in an unconfined medium. The convective transport originates as a consequence of the interaction between a uniform free-stream flow and the flow evolving due to the rotation of the sharp-edged body. A finite volume-based method and a body-fitted grid system along with the moving boundaries are used to obtain the numerical solution of the incompressible Navier–Stokes and energy equations. The Reynolds number based on the free-stream flow is considered in the range 10 ≤ Re ≤ 200, and the dimensionless rotational speed of the cylinder is kept 0 ≤ Ω ≤ 5. Depending on the Reynolds number and the rotational speed of the cylinder, the transport characteristics change. For the range 10 ≤ Re < 50, the flow remains steady irrespective of the rotational speed. In the range 50 ≤ Re ≤ 200, regular low-frequency Kármán vortex shedding (VS) is observed up to a critical rate of rotation (Ωcr ). Beyond Ωcr , the global convective transport shows a steady nature. The rotating circular cylinder also shows likewise degeneration of Kármán VS at some critical rotational speed. However, the heat transfer behavior varies significantly with a rotating circular cylinder. Such thermofluidic transport around a spinning square in an unconfined free-stream flow is reported for the first time