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Effective sample size estimation for a mechanical ventilation trial through Monte-Carlo simulation: Length of mechanical ventilation and Ventilator Free Days

Morton SE, Chiew YS, Pretty C, Moltchanova E, Scarrott C, Redmond D, et al.

Math Biosci, 2017 02;284:21-31.
PMID: 27301378 DOI: 10.1016/j.mbs.2016.06.001

Randomised control trials have sought to seek to improve mechanical ventilation treatment. However, few trials to date have shown clinical significance. It is hypothesised that aside from effective treatment, the outcome metrics and sample sizes of the trial also affect the significance, and thus impact trial design. In this study, a Monte-Carlo simulation method was developed and used to investigate several outcome metrics of ventilation treatment, including 1) length of mechanical ventilation (LoMV); 2) Ventilator Free Days (VFD); and 3) LoMV-28, a combination of the other metrics. As these metrics have highly skewed distributions, it also investigated the impact of imposing clinically relevant exclusion criteria on study power to enable better design for significance. Data from invasively ventilated patients from a single intensive care unit were used in this analysis to demonstrate the method. Use of LoMV as an outcome metric required 160 patients/arm to reach 80% power with a clinically expected intervention difference of 25% LoMV if clinically relevant exclusion criteria were applied to the cohort, but 400 patients/arm if they were not. However, only 130 patients/arm would be required for the same statistical significance at the same intervention difference if VFD was used. A Monte-Carlo simulation approach using local cohort data combined with objective patient selection criteria can yield better design of ventilation studies to desired power and significance, with fewer patients per arm than traditional trial design methods, which in turn reduces patient risk. Outcome metrics, such as VFD, should be used when a difference in mortality is also expected between the two cohorts. Finally, the non-parametric approach taken is readily generalisable to a range of trial types where outcome data is similarly skewed.
Benchmarking working conditions for health and safety in the frontline healthcare industry: Perspectives from Australia and Malaysia

McLinton SS, Loh MY, Dollard MF, Tuckey MMR, Idris MA, Morton S

J Adv Nurs, 2018 Apr 06.
PMID: 29633325 DOI: 10.1111/jan.13580

AIM: To present benchmarks for working conditions in healthcare industries as an initial effort into international surveillance.
BACKGROUND: The healthcare industry is fundamental to sustaining the health of Australians, yet it is under immense pressure. Budgets are limited, demands are increasing as are workplace injuries and all of these factors compromise patient care. Urgent attention is needed to reduce strains on workers and costs in health care, however, little work has been done to benchmark psychosocial factors in healthcare working conditions in the Asia-Pacific. Intercultural comparisons are important to provide an evidence base for public policy.
DESIGN: A cross-sectional design was used (like other studies of prevalence), including a mixed-methods approach with qualitative interviews to better contextualize the results.
METHODS: Data on psychosocial factors and other work variables were collected from healthcare workers in three hospitals in Australia (N = 1,258) and Malaysia (N = 1,125). 2015 benchmarks were calculated for each variable and comparison was conducted via independent samples t tests. Healthcare samples were also compared with benchmarks for non-healthcare general working populations from their respective countries: Australia (N = 973) and Malaysia (N = 225).
FINDINGS: Our study benchmarks healthcare working conditions in Australia and Malaysia against the general working population, identifying trends that indicate the industry is in need of intervention strategies and job redesign initiatives that better support psychological health and safety.
CONCLUSION: We move toward a better understanding of the precursors of psychosocial safety climate in a broader context, including similarities and differences between Australia and Malaysia in national culture, government occupational health and safety policies and top-level management practices.
Fulltext Model-based PEEP titration versus standard practice in mechanical ventilation: a randomised controlled trial

Kim KT, Morton S, Howe S, Chiew YS, Knopp JL, Docherty P, et al.

Trials, 2020 Feb 01;21(1):130.
PMID: 32007099 DOI: 10.1186/s13063-019-4035-7

BACKGROUND: Positive end-expiratory pressure (PEEP) at minimum respiratory elastance during mechanical ventilation (MV) in patients with acute respiratory distress syndrome (ARDS) may improve patient care and outcome. The Clinical utilisation of respiratory elastance (CURE) trial is a two-arm, randomised controlled trial (RCT) investigating the performance of PEEP selected at an objective, model-based minimal respiratory system elastance in patients with ARDS.
METHODS AND DESIGN: The CURE RCT compares two groups of patients requiring invasive MV with a partial pressure of arterial oxygen/fraction of inspired oxygen (PaO2/FiO2) ratio ≤ 200; one criterion of the Berlin consensus definition of moderate (≤ 200) or severe (≤ 100) ARDS. All patients are ventilated using pressure controlled (bi-level) ventilation with tidal volume = 6-8 ml/kg. Patients randomised to the control group will have PEEP selected per standard practice (SPV). Patients randomised to the intervention will have PEEP selected based on a minimal elastance using a model-based computerised method. The CURE RCT is a single-centre trial in the intensive care unit (ICU) of Christchurch hospital, New Zealand, with a target sample size of 320 patients over a maximum of 3 years. The primary outcome is the area under the curve (AUC) ratio of arterial blood oxygenation to the fraction of inspired oxygen over time. Secondary outcomes include length of time of MV, ventilator-free days (VFD) up to 28 days, ICU and hospital length of stay, AUC of oxygen saturation (SpO2)/FiO2 during MV, number of desaturation events (SpO2
Fulltext Association of the lupus low disease activity state (LLDAS) with health-related quality of life in a multinational prospective study

Golder V, Kandane-Rathnayake R, Hoi AY, Huq M, Louthrenoo W, An Y, et al.

Arthritis Res Ther, 2017 03 20;19(1):62.
PMID: 28320433 DOI: 10.1186/s13075-017-1256-6

BACKGROUND: Systemic lupus erythematosus (SLE) is associated with significant impairment of health-related quality of life (HR-QoL). Recently, meeting a definition of a lupus low disease activity state (LLDAS), analogous to low disease activity in rheumatoid arthritis, was preliminarily validated as associated with protection from damage accrual. The LLDAS definition has not been previously evaluated for association with patient-reported outcomes. The objective of this study was to determine whether LLDAS is associated with better HR-QoL, and examine predictors of HR-QoL, in a large multiethnic, multinational cohort of patients with SLE.
METHODS: HR-QoL was measured using the Medical Outcomes Study 36-item short form health survey (SF-36v2) in a prospective study of 1422 patients. Disease status was measured using the SLE disease activity index (SLEDAI-2 K), physician global assessment (PGA) and LLDAS.
RESULTS: Significant differences in SF-36 domain scores were found between patients stratified by ethnic group, education level and damage score, and with the presence of active musculoskeletal or cutaneous manifestations. In multiple linear regression analysis, Asian ethnicity (p
Fulltext Frequency and predictors of the lupus low disease activity state in a multi-national and multi-ethnic cohort

Golder V, Kandane-Rathnayake R, Hoi AY, Huq M, Louthrenoo W, An Y, et al.

Arthritis Res Ther, 2016 11 09;18(1):260.
PMID: 27829463 DOI: 10.1186/s13075-016-1163-2

BACKGROUND: Systemic lupus erythematosus (SLE) is a chronic heterogeneous disease with considerable burden from disease activity and damage. A novel clinical treatment target in the form of the lupus low disease activity state (LLDAS) has been recently reported, with retrospective validation showing that time spent in LLDAS translates to reduced damage accrual. The objectives of this study were to describe the frequency and identify the predictors of attaining LLDAS in a large multinational cohort of patients with SLE.
METHODS: Data were collected at the recruitment visit in patients with SLE enrolled in a longitudinal study in nine countries. Data were analysed cross-sectionally against the recently published definition of LLDAS, and the frequency and characteristics associated with presence of LLDAS were determined. Stepwise multivariable logistic regression was used to determine predictors of LLDAS.
RESULTS: Of the 1846 patients assessed, criteria for LLDAS were met by 44 %. Patients with shorter disease duration were less likely to be in LLDAS (OR 0.31, 95 % CI 0.19-0.49, p