Operating room efficiency in a low resource setting: a pilot study from a large tertiary referral center in Ethiopia

Background The operating room (OR) is one of the most expensive areas of a hospital, requiring large capital and recurring investments, and necessitating efficient throughput to reduce costs per patient encounter. On top of increasing costs, inefficient utilization of operating rooms results in prolonged waiting lists, high rate of cancellation, frustration of OR personnel as well as increased anxiety that negatively impacts the health of patients. This problem is magnified in developing countries, where there is a high unmet surgical need. However, no system currently exists to assess operating room utilization in Ethiopia. Methodology A prospective study was conducted over a period of 3 months (May 1 to July 31, 2019) in a tertiary hospital. Surgical case start time, end time, room turnover time, cancellations and reason for cancellation were observed to evaluate the efficiency of eight operating rooms. Results A total of 933 elective procedures were observed during the study period. Of these, 246 were cancelled, yielding a cancellation rate of 35.8%. The most common reasons for cancellation were related to lack of OR time and patient preparation (8.7% and 7.7% respectively). Shortage of facilities (instrument, blood, ICU bed) were causes of cancelation in 7.7%. Start time was delayed in 93.4% (mean 8:56 am ± 52 min) of cases. Last case completion time was early in 47.9% and delayed in 20.6% (mean 2:54 pm ± 156 min). Turnover time was prolonged in 34.5% (mean 25 min ± 49 min). Total operating room utilization ranged from 10.5% to 174%. Operating rooms were underutilized in 42.7% while overutilization was found in 14.6%. Conclusion We found a high cancellation rate, most attributable to late start times leading to delays for the remainder of cases, and lack of preoperative patient preparation. In a setting with a high unmet burden of surgical disease, OR efficiency must be maximized with improved patient evaluation workflows, adequate OR staffing and commitment to punctual start times. We recommend future quality improvement projects focusing on these areas to increase OR efficiency.

Computational investigation of blood cell transport in retinal microaneurysms

Microaneurysms (MAs) are one of the earliest clinically visible signs of diabetic retinopathy (DR). MA leakage or rupture may precipitate local pathology in the surrounding neural retina that impacts visual function. Thrombosis in MAs may affect their turnover time, an indicator associated with visual and anatomic outcomes in the diabetic eyes. In this work, we perform computational modeling of blood flow in microchannels containing various MAs to investigate the pathologies of MAs in DR. The particle-based model employed in this study can explicitly represent red blood cells (RBCs) and platelets as well as their interaction in the blood flow, a process that is very difficult to observe in vivo. Our simulations illustrate that while the main blood flow from the parent vessels can perfuse the entire lumen of MAs with small body-to-neck ratio (BNR), it can only perfuse part of the lumen in MAs with large BNR, particularly at a low hematocrit level, leading to possible hypoxic conditions inside MAs. We also quantify the impacts of the size of MAs, blood flow velocity, hematocrit and RBC stiffness and adhesion on the likelihood of platelets entering MAs as well as their residence time inside, two factors that are thought to be associated with thrombus formation in MAs. Our results show that enlarged MA size, increased blood velocity and hematocrit in the parent vessel of MAs as well as the RBC-RBC adhesion promote the migration of platelets into MAs and also prolong their residence time, thereby increasing the propensity of thrombosis within MAs. Overall, our work suggests that computational simulations using particle-based models can help to understand the microvascular pathology pertaining to MAs in DR and provide insights to stimulate and steer new experimental and computational studies in this area.

Spray dispersion regimes following atomization in a turbulent co-axial gas jet

A canonical co-axial round-jet two-fluid atomizer where atomization occurs over a wide range of momentum ratios: $M=1.9 - 376.4$ is studied. The near field of the spray, where the droplet formation process takes place, is characterized and linked to droplet dispersion in the far field of the jet. Counterintuitively, our results indicate that in the low-momentum regime, increasing the momentum in the gas phase leads to less droplet dispersion. A critical momentum ratio of the order of $M_c=50$ , that separates this regime from a high-momentum one with less dispersion, is found in both the near and far fields. A phenomenological model is proposed that determines the susceptibility of droplets to disperse beyond the nominal extent of the gas phase based on a critical Stokes number, $St=\tau _p/T_E=1.9$ , formulated based on the local Eulerian large scale eddy turnover time, $T_E$ , and the droplets’ response time, $\tau _p$ . A two-dimensional phase space summarizes the extent of these different regimes in the context of spray characteristics found in the literature.

Agent-based simulations for protecting nursing homes with prevention and vaccination strategies

Due to its high lethality among older people, the safety of nursing homes has been of central importance during the COVID-19 pandemic. With test procedures and vaccines becoming available at scale, nursing homes might relax prohibitory measures while controlling the spread of infections. By control we mean that each index case infects less than one other person on average. Here, we develop an agent-based epidemiological model for the spread of SARS-CoV-2 calibrated to Austrian nursing homes to identify optimal prevention strategies. We find that the effectiveness of mitigation testing depends critically on test turnover time (time until test result), the detection threshold of tests and mitigation testing frequencies. Under realistic conditions and in absence of vaccinations, we find that mitigation testing of employees only might be sufficient to control outbreaks if tests have low turnover times and detection thresholds. If vaccines that are 60% effective against high viral load and transmission are available, control is achieved if 80% or more of the residents are vaccinated, even without mitigation testing and if residents are allowed to have visitors. Since these results strongly depend on vaccine efficacy against infection, retention of testing infrastructures, regular testing and sequencing of virus genomes is advised to enable early identification of new variants of concern.

Observation Based Budget and Lifetime of Excess Atmospheric Carbon Dioxide

The global budgets of CO2 and of excess CO2 (i.e., above preindustrial) in the biogeosphere are examined by a top-down, observationally constrained approach. Global stocks in the atmosphere, mixed-layer and deep ocean, and labile and obdurate terrestrial biosphere, and fluxes between them are quantified; total uptake of carbon by the terrestrial biosphere is constrained by observations, but apportionment to the two terrestrial compartments is only weakly constrained, requiring examination of sensitivity to this apportionment. Because of near equilibrium between the atmosphere and the mixed-layer ocean and near steady state between the atmosphere and the labile biosphere, these three compartments are tightly coupled. For best-estimate present-day anthropogenic emissions the turnover time of excess carbon in these compartments to the deep ocean and obdurate biosphere is 67 to 158 years. Atmospheric CO2 over the Anthropocene is accurately represented by a five-compartment model with four independent parameters: two universal geophysical quantities and two, specific to CO2, treated as variable. The model also accurately represents atmospheric radiocarbon, particularly the large increase due to atmospheric testing of nuclear weapons and the subsequent decrease. The adjustment time of excess atmospheric CO2, evaluated from the rate of decrease following abrupt cessation of emissions, is 78 to 140 years, consistent with the turnover time, approaching a long-time floor of 15–20 % of the value at the time of cessation. The lifetime of excess CO2 found here, several-fold shorter than estimates from current carbon-cycle models, indicates that cessation of anthropogenic emissions atmospheric would result in substantial recovery of CO2 toward its preindustrial value in less than a century.

Turnover Time of the East Sea (Sea of Japan) Meridional Overturning Circulation

The East Sea (ES; Sea of Japan) meridional overturning circulation (MOC) serves as a crucial mechanism for the transportation of dissolved, colloidal, and suspended particulate matters, including pollutants, on the surface to deep waters via thermohaline circulation. Therefore, understanding the structure of the ES MOC is critical for characterizing its temporal and spatial distribution. Numerous studies have estimated these parameters indirectly using chemical tracers, severely limiting the accuracy of the results. In this study, we provide a method for directly estimating the turnover times of the ES MOC using the stream functions calculated from HYbrid Coordinate Ocean Model (HYCOM) reanalysis data by averaging the flow pattern in the meridional 2-D plane. Because the flow pattern is not consistent but various over time, three cases of stream function fields were computed over a 20-year period. The turnover time was estimated by calculating the time required for water particles to circulate along the streamlines. In the cases of multiple (two or three) convection cells, we considered all possible scenarios of the exchange of water particles between adjacent cells, so that they circulated over those cells until finally returning to the original position and completing the journey on the ES MOC. Three different cell cases were tested, and each case had different water particle exchange scenarios. The resulting turnover times were 17.91–58.59 years, 26.41–37.28 years, and 8.68–45.44 years for the mean, deep, and shallow convection cases, respectively. The maximum turnover time, namely 58.59 years, was obtained when circulating the water particle over all three cells, and it was approximately half of that estimated by the chemical tracers in previous studies (∼100 years). This underestimation arose because the streamlines and water particle movement were not calculated in the shallow (<300 m) and deep areas (>3,000 m) in this study. Regardless, the results of this study provide insight into the ES MOC dynamics and indicate that the traditional chemical turnover time represents only one of the various turnover scenarios that could exist in the ES.

Modulation of fluid temperature fluctuations by particles in turbulence

Modulation of fluid temperature fluctuations by particles due to thermal interaction in homogeneous isotropic turbulence is studied. For simplicity, only thermal coupling between the fluid and particles is considered, and momentum coupling is neglected. Application of the statistical theory used in cloud turbulence research leads to the prediction that modulation of the intensity of fluid temperature fluctuations by particles is expressed as a function of the Damköhler number, which is defined as the ratio of the turbulence large-eddy turnover time to the fluid thermal relaxation time. Direct numerical simulations are conducted for two-way thermal coupling between the fluid temperature field and point particles in homogeneous isotropic turbulence. The simulation results are shown to agree well with the theoretical predictions.

Impact of the SARS-CoV-2 pandemic on turnover time and revenue in the endoscopy unit: single-center experience

Background and study aims The SARS-CoV-2 pandemic heavily impacted the New York metro area causing most institutions to either reduce case volume or fully close remaining open units incorporated specific guidelines for procedures lockdown potentially leading to a greater turn-over time. We analyzed the quantitative and financial impact of this lost time on our tertiary care center’s endoscopy unit. Patients and methods This single-center, retrospective study included demographics, procedure details and turn-over times (TOT) from all endoscopic procedures between December 1, 2019 to June 30, 2020. Cases were categorized as pre-COVID-19 group from December 1, 2019 to March 15, 2020 and during COVID-19 (lockdown) group from March 16, 2020 to June 30, 2020. The financial impact was assessed using national averages for reimbursement of outpatient endoscopic procedures provided by Center for Medicare and Medicaid Services. Results A total of 3622 procedures were performed during the study period: 2297 in the pre-COVID-19 period, 1325 in the COVID-19 period, representing a 42.32 % decrease. In the COVID-19 lockdown group, there was a significant increase in TOT in both the general endoscopy cases (18.11 minutes, P = 0.000) and advanced endoscopy cases (17.7 minutes, P = 0.000). The 42.3 % decrease in volume equated to at least $1.6 million USD in lost revenue during the lockdown. Conclusions COVID-19 pandemic led to an increase in TOT with overall reduced procedure volume and a negative effect on revenue. Providing continued endoscopic management during a pandemic avoids delays in reopening the endoscopy unit and hampers the post-pandemic surge of delayed cases and its financial impact.

EP.TU.651Training Opportunity In A Non Covid Private Hospital During The Initals Phase Of Sars-Cov-2 Pandemic-Our Experience

Aim We would like to share our experience in the unique opportunity our surgical trainees had, while operating in a NON COVID private hospital. Methods We did a retrospective data collection from 1st of April till 31st May 2020. The data was collected about the patients who underwent elective surgery in a non COVID private hospital selected by our NHS trust. The selected patients were asked to self-isolate for 2 weeks prior to surgery date. They also underwent 2 swab tests, the first one a week before and another one 48 hours before the surgery date along with a chest X-ray. Only the patients who tested negative on swabs were operated in the private setup. Results There were 17 elective laparoscopic cholecystectomies and 42 breast surgeries performed. The primary operating surgeon were trainees in around 80 percent cases. Ours was the first NHS trust to start this in the North East England. There was no increase in operating time, but the turnover time was nearly doubled because the guidelines for safe anesthesia and surgery during this pandemic were strictly followed. We did not have any complications or readmission related to surgery in this cohort of patients. There was no reported SARS-CoV-2 infection to patients and the involved medical staff. Conclusion The opportunity for continuity of surgical training in a private setup is a possibility and should be explored more in future.

DO RADIOCARBON AGES OF PLANT WAX BIOMARKERS AGREE WITH 14C-TOC/OSL-BASED AGE MODELS IN AN ARID HIGH-ALTITUDE LAKE SYSTEM?

ABSTRACT To elucidate the dynamics of terrestrial leaf waxes in a high-altitude lake system, we performed compound-specific radiocarbon analysis (CSRA) of long-chain n-alkanes in two sediment core sections from Lake Karakul (Pamirs, Tajikistan) and in surface soil samples from the catchment area. We aimed to answer the question whether the n-alkanes are delivered into the lake sediment with substantial delay due to storage in soils, which may cause a potential bias when used as paleoenvironmental proxies. In the surface soils, the CSRA results reveal an age range of n-alkanes from modern to 2278 ± 155 cal BP. In the two sediment core samples, three of the four n-alkane ages fell on the lower ends of the 1σ-uncertainty ranges of modeled ages of the sediments (based on AMS 14C-TOC and OSL dating results). We conclude that sedimentary leaf waxes represent compounds with intermediate turnover time in soils, for example originating from alluvial plains close to the shores. Overall, the results provide evidence that sedimentary leaf wax compounds in this cold and arid setting are potentially older than the conventional age model indicates, but these findings need to be interpreted in context of the generally large uncertainty ranges of such age models.