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D Chan - One of the best experts on this subject based on the ideXlab platform.
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determining an optimal Recovery Time for construction rebar workers after working to exhaustion in a hot and humid environment
Building and Environment, 2012Co-Authors: Albert P C Chan, Del P Wong, Michael C H Yam, D ChanAbstract:This paper is an extension to a paper previously published in the journal Building and Environment. Having determined an optimal Recovery Time in a controlled climatic environment, this paper aims to investigate the real impact on construction rebar workers by replicating the clinical experimentation to a series of field studies. Field studies were conducted during the summer Time in Hong Kong. Nineteen rebar workers performed tasks of fixing and bending steel reinforcement bars on two building construction sites until voluntary exhaustion and were allowed to recover on site until their physiological conditions returned to the pre-work level or lower. Physiological Strain Index (PSI) was used as a yardstick to determine the rate of Recovery. A total of 411 sets of meteorological and physiological data collected over fourteen working days between July and August of 2011 were collated to derive the optimal Recovery Time. It was found that on average a rebar worker could achieve 94% Recovery in 40 min; 93% in 35 min; 92% in 30 min; 88% in 25 min; 84% in 20 min; 78% in 15 min; 68% in 10 min; and 58% in 5 min. Curve estimation results showed that Recovery Time is a significant variable to predict the rate of Recovery (R2 = 0.99, P < 0.05). Additional rest Times should be introduced between works in extreme hot weather to enable workers to recover from heat stress. Frequency and duration of each rest Time should be agreed among different stakeholders based on the cumulative Recovery curve.
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determining an optimal Recovery Time for construction rebar workers after working to exhaustion in a hot and humid environment
Building and Environment, 2012Co-Authors: Albert P C Chan, Del P Wong, Wen Yi, D ChanAbstract:This paper is an extension to a paper previously published in the journal Building and Environment. Having determined an optimal Recovery Time in a controlled climatic environment, this paper aims to investigate the real impact on construction rebar workers by replicating the clinical experimentation to a series of field studies. Field studies were conducted during the summer Time in Hong Kong. Nineteen rebar workers performed tasks of fixing and bending steel reinforcement bars on two building construction sites until voluntary exhaustion and were allowed to recover on site until their physiological conditions returned to the pre-work level or lower. Physiological Strain Index (PSI) was used as a yardstick to determine the rate of Recovery. A total of 411 sets of meteorological and physiological data collected over fourteen working days between July and August of 2011 were collated to derive the optimal Recovery Time. It was found that on average a rebar worker could achieve 94% Recovery in 40 min; 93% in 35 min; 92% in 30 min; 88% in 25 min; 84% in 20 min; 78% in 15 min; 68% in 10 min; and 58% in 5 min. Curve estimation results showed that Recovery Time is a significant variable to predict the rate of Recovery (R2 = 0.99, P < 0.05). Additional rest Times should be introduced between works in extreme hot weather to enable workers to recover from heat stress. Frequency and duration of each rest Time should be agreed among different stakeholders based on the cumulative Recovery curve.
Christopher W Seymour - One of the best experts on this subject based on the ideXlab platform.
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minute ventilation Recovery Time measured using a new simplified methodology predicts extubation outcome
Journal of Intensive Care Medicine, 2008Co-Authors: Christopher W Seymour, Scott D Halpern, Jason D Christie, Robert Gallop, Barry D FuchsAbstract:: Extubation failure is associated with poor intensive care unit and hospital outcomes. Minute ventilation Recovery Time, an integrative measure of a patient's respiratory reserve, has been shown in a pilot study to predict extubation outcome; however, the methodology is subjective and impractical for routine use. The authors hypothesize that minute ventilation Recovery Time, measured using an objective and simpler method, would predict extubation outcome. A prospective cohort study was performed in adult medical and surgical intensive care unit patients intubated for >24 hours who were weaning from mechanical ventilation. Minute ventilation Recovery Time was measured using a new, simplified, and objective method following the final spontaneous breathing trial prior to extubation. The primary outcome was extubation failure, defined as reintubation within 7 days. The study cohort comprised 88 patients, of whom 22 (25%) failed extubation after a median of 3 days. Demographic data, weaning parameters, and the proportion of patients who passed an extubation screen were similar between groups (P > .05). Minute ventilation Recovery Time was significantly longer in patients who failed extubation (15 [5-15] vs 2 [1-5] minutes, P or=5 minutes) for prediction of extubation failure were sensitivity = 0.78, specificity = 0.71, positive predictive value = 0.47, negative predictive value = 0.90, correctly classified = 0.72. Adjustment for significant covariates did not alter the relationship between minute ventilation Recovery Time >or=5 minutes and extubation failure (odds ratio = 4.9, 95% confidence interval 1.45-16.2, P < .02). C statistic was 0.79 +/- 0.17. It was concluded that minute ventilation Recovery Time, measured using a feasible methodology, can predict extubation outcome in medical and surgical intensive care unit patients.
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evaluation of a new method for measurement of minute ventilation Recovery Time
Respiratory Care, 2006Co-Authors: Christopher W Seymour, Jason D Christie, Christina Gaughan, Barry D FuchsAbstract:PURPOSE: To determine if the measurement of minute ventilation Recovery Time (V˙ERT), a recently proposed predictor of extubation outcome, can be reproduced using a more practical, simpler method. METHODS: A case series with convenience sampling was performed in the surgical intensive care unit of a tertiary-care hospital. Nineteen patients were enrolled during weaning from mechanical ventilation, prior to the initial extubation attempt. Within-subject comparisons of V˙ERT were performed, using 2 alternative methods for measuring baseline V˙E and one alternative method for determining the threshold for Recovery of V˙E during the final spontaneous breathing trial prior to extubation. Comparison methods for baseline V˙E included an 8-hour average and the last V˙E measurement prior to the spontaneous breathing trial. The alternative threshold for defining Recovery of V˙E was 100% of the baseline value (vs 110% in the original method). RESULTS: The study subjects were primarily cardiac surgery patients (63%) and were ventilated for a median of 5 days prior to extubation. V˙ERT calculated using the 8-hour average or the last V˙E measurement prior to the spontaneous breathing trial as baseline, and a threshold of 100% of baseline V˙E to define Recovery most closely approximated V˙ERT obtained by the original method and similarly classified patients at high risk for reintubation (kappa statistic = 0.78 ± 0.2). CONCLUSIONS: V˙ERT can be determined using a simpler method for measuring both baseline V˙E and the Recovery threshold. These methodological modifications may increase the feasibility of measuring V˙ERT, while reproducing the results obtained by the original method.
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measurement of a baseline minute ventilation for the calculation of minute ventilation Recovery Time is a subjective method reliable
Respiratory Care, 2005Co-Authors: Christopher W Seymour, Jason D Christie, Christina Gaughan, Barry D FuchsAbstract:BACKGROUND: Minute ventilation Recovery Time is a new predictor of extubation outcome that uses a subjective method for the determination of baseline minute ventilation (VE) during its measurement. The purpose of the current study is to evaluate the inter-rater reliability of this subjective method for determining baseline VE. METHODS: Three critical-care physicians served as independent readers. Each was trained with 5 practice VE trends, using the published method for determining baseline VE, defined as the lowest, stable nadir lasting 15–30 min prior to the final weaning trial before extubation. Readers then determined baseline VE prospectively from an 8-hour VE trend for 19 patients who were weaning from mechanical ventilation in the surgical intensive care unit of a tertiary care hospital. Each VE trend was an objective recording of VE every 15 min for 8 hours, immediately prior to the final weaning trial before extubation. RESULTS: There was excellent inter-rater reliability between trained readers for determination of a subjective VE baseline. Baseline VE was within 1 L/min for 15/19 patients (79%). Intra-class correlation across the 3 readers was 0.92 (p 0.5), and Spearman correlations between all reader pairs were significant (p CONCLUSION: After minimal training, readers can reliably determine a subjective baseline VE. This study validates the original methodology for determining baseline VE, an essential step in the measurement of minute ventilation Recovery Time.
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minute ventilation Recovery Time a predictor of extubation outcome
Chest, 2003Co-Authors: Anthony Martinez, Christopher W SeymourAbstract:Study objectives: To determine if minute ventilation ( e ) measured as a trend following the final weaning trial prior to extubation may identify patients ready for extubation and be useful as a predictive measure of extubation outcome. Design: Prospective observational study. Setting: Community hospital medical/surgical ICU. Patients: Sixty-nine patients receiving mechanical ventilation enrolled in an ICU weaning protocol who underwent planned extubation during 6 months of prospective evaluation. The failed extubation group included patients reintubated within 7 days. Patients were excluded if they received ventilation by noninvasive mask, bilevel positive airway pressure, tracheostomy, or were self-extubated. Interventions: Patients tolerating a spontaneous breathing trial (SBT) and ready for planned extubation were placed back on their pre-SBT ventilator settings for up to 25 min, during which respiratory parameters were recorded. Respiratory parameters (respiratory rate, tidal volume, e , rapid shallow breathing index [ f /V t ]) were obtained at three Time points: baseline (pre-SBT), posttrial (immediate conclusion of SBT), and Recovery (return to baseline). Patients were assumed to recover when e decreased to 110% of the predetermined baseline. Measurements and results: Fifty-nine patients were successfully extubated, and 10 patients required reintubation after 2.5 ± 2.6 days (mean ± SD). Both groups were similar in age, comorbid status, primary diagnosis, APACHE (acute physiology and chronic health evaluation) II score, mode of weaning, and SBT length (p > 0.1). Respiratory parameters measured were similar at all three Time points studied (p > 0.1). e Recovery Time of successful extubations was significantly shorter than failed extubations (3.6 ± 2.7 min vs 9.6 ± 5.8 min, p e Recovery Time was an independent predictor of extubation outcome (p e Recovery Time (0.85 ± 0.07) was larger than that for baseline e , posttrial e , posttrial f /V t , or Pa co 2 . Conclusions: e Recovery Time is an easy-to-measure parameter that may assist in determining respiratory reserve. Preliminary data demonstrates that it may be a useful adjunct in the decision to discontinue mechanical ventilation.
Shuyang Zhang - One of the best experts on this subject based on the ideXlab platform.
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metro disruption management optimal initiation Time of substitute bus services under uncertain system Recovery Time
Transportation Research Part C-emerging Technologies, 2018Co-Authors: Shuyang ZhangAbstract:Abstract Determining the initiation Time of substitute bus (SB) services is critical for metro disruption management, especially under uncertain Recovery Time. This study develops a mathematical formulation to determine the optimal initiation Time (OIT) of SB services by trading-off their initiation cost and passenger delay cost, thereby minimizing the total system cost. Given the probability distribution of metro disruption duration, we determine the OIT by formulating an optimization problem to minimize the expected total system cost. We then conduct sensitivity analyses of the initiation cost of SB services, passenger value of Time, and SB services rate. The results show that SB services ought to be activated only if the metro incident lasts longer than a certain Time interval, depending on the factors mentioned earlier, and the OIT should advance with the predicted incident duration. This paper derives analytical results for the case of linear passenger arrival, and determines the results numerically for the case of non-linear passenger arrival when analytical closed-form solutions are not available. The findings will facilitate transit operators to develop response plans in the aftermath of a metro disruption.
Albert P C Chan - One of the best experts on this subject based on the ideXlab platform.
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determining an optimal Recovery Time for construction rebar workers after working to exhaustion in a hot and humid environment
Building and Environment, 2012Co-Authors: Albert P C Chan, Del P Wong, Michael C H Yam, D ChanAbstract:This paper is an extension to a paper previously published in the journal Building and Environment. Having determined an optimal Recovery Time in a controlled climatic environment, this paper aims to investigate the real impact on construction rebar workers by replicating the clinical experimentation to a series of field studies. Field studies were conducted during the summer Time in Hong Kong. Nineteen rebar workers performed tasks of fixing and bending steel reinforcement bars on two building construction sites until voluntary exhaustion and were allowed to recover on site until their physiological conditions returned to the pre-work level or lower. Physiological Strain Index (PSI) was used as a yardstick to determine the rate of Recovery. A total of 411 sets of meteorological and physiological data collected over fourteen working days between July and August of 2011 were collated to derive the optimal Recovery Time. It was found that on average a rebar worker could achieve 94% Recovery in 40 min; 93% in 35 min; 92% in 30 min; 88% in 25 min; 84% in 20 min; 78% in 15 min; 68% in 10 min; and 58% in 5 min. Curve estimation results showed that Recovery Time is a significant variable to predict the rate of Recovery (R2 = 0.99, P < 0.05). Additional rest Times should be introduced between works in extreme hot weather to enable workers to recover from heat stress. Frequency and duration of each rest Time should be agreed among different stakeholders based on the cumulative Recovery curve.
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determining an optimal Recovery Time for construction rebar workers after working to exhaustion in a hot and humid environment
Building and Environment, 2012Co-Authors: Albert P C Chan, Del P Wong, Wen Yi, D ChanAbstract:This paper is an extension to a paper previously published in the journal Building and Environment. Having determined an optimal Recovery Time in a controlled climatic environment, this paper aims to investigate the real impact on construction rebar workers by replicating the clinical experimentation to a series of field studies. Field studies were conducted during the summer Time in Hong Kong. Nineteen rebar workers performed tasks of fixing and bending steel reinforcement bars on two building construction sites until voluntary exhaustion and were allowed to recover on site until their physiological conditions returned to the pre-work level or lower. Physiological Strain Index (PSI) was used as a yardstick to determine the rate of Recovery. A total of 411 sets of meteorological and physiological data collected over fourteen working days between July and August of 2011 were collated to derive the optimal Recovery Time. It was found that on average a rebar worker could achieve 94% Recovery in 40 min; 93% in 35 min; 92% in 30 min; 88% in 25 min; 84% in 20 min; 78% in 15 min; 68% in 10 min; and 58% in 5 min. Curve estimation results showed that Recovery Time is a significant variable to predict the rate of Recovery (R2 = 0.99, P < 0.05). Additional rest Times should be introduced between works in extreme hot weather to enable workers to recover from heat stress. Frequency and duration of each rest Time should be agreed among different stakeholders based on the cumulative Recovery curve.
Barry D Fuchs - One of the best experts on this subject based on the ideXlab platform.
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minute ventilation Recovery Time measured using a new simplified methodology predicts extubation outcome
Journal of Intensive Care Medicine, 2008Co-Authors: Christopher W Seymour, Scott D Halpern, Jason D Christie, Robert Gallop, Barry D FuchsAbstract:: Extubation failure is associated with poor intensive care unit and hospital outcomes. Minute ventilation Recovery Time, an integrative measure of a patient's respiratory reserve, has been shown in a pilot study to predict extubation outcome; however, the methodology is subjective and impractical for routine use. The authors hypothesize that minute ventilation Recovery Time, measured using an objective and simpler method, would predict extubation outcome. A prospective cohort study was performed in adult medical and surgical intensive care unit patients intubated for >24 hours who were weaning from mechanical ventilation. Minute ventilation Recovery Time was measured using a new, simplified, and objective method following the final spontaneous breathing trial prior to extubation. The primary outcome was extubation failure, defined as reintubation within 7 days. The study cohort comprised 88 patients, of whom 22 (25%) failed extubation after a median of 3 days. Demographic data, weaning parameters, and the proportion of patients who passed an extubation screen were similar between groups (P > .05). Minute ventilation Recovery Time was significantly longer in patients who failed extubation (15 [5-15] vs 2 [1-5] minutes, P or=5 minutes) for prediction of extubation failure were sensitivity = 0.78, specificity = 0.71, positive predictive value = 0.47, negative predictive value = 0.90, correctly classified = 0.72. Adjustment for significant covariates did not alter the relationship between minute ventilation Recovery Time >or=5 minutes and extubation failure (odds ratio = 4.9, 95% confidence interval 1.45-16.2, P < .02). C statistic was 0.79 +/- 0.17. It was concluded that minute ventilation Recovery Time, measured using a feasible methodology, can predict extubation outcome in medical and surgical intensive care unit patients.
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evaluation of a new method for measurement of minute ventilation Recovery Time
Respiratory Care, 2006Co-Authors: Christopher W Seymour, Jason D Christie, Christina Gaughan, Barry D FuchsAbstract:PURPOSE: To determine if the measurement of minute ventilation Recovery Time (V˙ERT), a recently proposed predictor of extubation outcome, can be reproduced using a more practical, simpler method. METHODS: A case series with convenience sampling was performed in the surgical intensive care unit of a tertiary-care hospital. Nineteen patients were enrolled during weaning from mechanical ventilation, prior to the initial extubation attempt. Within-subject comparisons of V˙ERT were performed, using 2 alternative methods for measuring baseline V˙E and one alternative method for determining the threshold for Recovery of V˙E during the final spontaneous breathing trial prior to extubation. Comparison methods for baseline V˙E included an 8-hour average and the last V˙E measurement prior to the spontaneous breathing trial. The alternative threshold for defining Recovery of V˙E was 100% of the baseline value (vs 110% in the original method). RESULTS: The study subjects were primarily cardiac surgery patients (63%) and were ventilated for a median of 5 days prior to extubation. V˙ERT calculated using the 8-hour average or the last V˙E measurement prior to the spontaneous breathing trial as baseline, and a threshold of 100% of baseline V˙E to define Recovery most closely approximated V˙ERT obtained by the original method and similarly classified patients at high risk for reintubation (kappa statistic = 0.78 ± 0.2). CONCLUSIONS: V˙ERT can be determined using a simpler method for measuring both baseline V˙E and the Recovery threshold. These methodological modifications may increase the feasibility of measuring V˙ERT, while reproducing the results obtained by the original method.
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measurement of a baseline minute ventilation for the calculation of minute ventilation Recovery Time is a subjective method reliable
Respiratory Care, 2005Co-Authors: Christopher W Seymour, Jason D Christie, Christina Gaughan, Barry D FuchsAbstract:BACKGROUND: Minute ventilation Recovery Time is a new predictor of extubation outcome that uses a subjective method for the determination of baseline minute ventilation (VE) during its measurement. The purpose of the current study is to evaluate the inter-rater reliability of this subjective method for determining baseline VE. METHODS: Three critical-care physicians served as independent readers. Each was trained with 5 practice VE trends, using the published method for determining baseline VE, defined as the lowest, stable nadir lasting 15–30 min prior to the final weaning trial before extubation. Readers then determined baseline VE prospectively from an 8-hour VE trend for 19 patients who were weaning from mechanical ventilation in the surgical intensive care unit of a tertiary care hospital. Each VE trend was an objective recording of VE every 15 min for 8 hours, immediately prior to the final weaning trial before extubation. RESULTS: There was excellent inter-rater reliability between trained readers for determination of a subjective VE baseline. Baseline VE was within 1 L/min for 15/19 patients (79%). Intra-class correlation across the 3 readers was 0.92 (p 0.5), and Spearman correlations between all reader pairs were significant (p CONCLUSION: After minimal training, readers can reliably determine a subjective baseline VE. This study validates the original methodology for determining baseline VE, an essential step in the measurement of minute ventilation Recovery Time.
