Corresponding author’s e-mail: jdwang@ntu.tw

1. Estimation of quality-adjusted life expectancy in patients under prolonged mechanical ventilation Mei-Chuan Hung, MPH 1, Yuan-Horng Yan, MD, MSc 2, Po-Sheng Fan, MD 2, Ming-Shian Lin, MD 2, Cheng-Ren Chen, MD 2, Lu-Cheng Kuo, MD 3, Chong-Jen Yu, MD, PhD 3 and Jung-Der Wang, MD, ScD 1, 3 There is a general lack of data regarding the survival and quality of life (QOL) for patients under prolonged mechanical ventilation (PMV), which makes it infeasible to communicate among patients, their families, and healthcare workers for clinical decision making before and throughout the course of installing mechanical ventilation. Therefore, the purpose of this study was to estimate the QOL utility, lifetime survival, quality-adjusted life expectancy (QALE), and expected utility loss for patients using PMV. 1 Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, Taipei, Taiwan; 2 Department of Internal Medicine, Chia-Yi Christian Hospital, Chiayi, Taiwan; 3 Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan; 4 Department of Environmental and Occupational Medicine, National Taiwan University Hospital, Taipei, Taiwan Background and Objective Material and Methods A total of 633 patients fulfilled the definition of requiring more than 21 days of PMV and were followed for nine years to obtain their survival status during 1998-2007. One hundred and forty-two patients were measured their quality of life with EQ-5D questionnaire during 2008-2009. In general, such patients did not survive for more than 1-3 years, but occasionally there were patients with a longer survival. Thus, lifetime survival of PMV patients (up to 300 months) were obtained using a linear extrapolation of a logit-transformed curve of the survival ratio between the PMV and an age-, gender- matched reference population generated by the Monte Carlo method from the life table of the general population of Taiwan. The detailed method and the mathematical proof under the assumption of constant excess hazard can be found in our previous reports. The survival probabilities for each time point were adjusted with utility measurement of quality of life and then extrapolated to 300 months to obtain the QALE. Further, we compared the age-, gender-matched reference population to calculate the expected lifetime utility loss. The health gap was calculated and defined as the proportion of expected loss of lifetime utility of patients with PMV in comparison with age- and gender-matched hypothetical referents simulated from vital statistics of Taiwan, which is usually considered as an indicator of health inequality. Results and Discussion The life expectancy and loss of life expectancy were 1.95 years and 8.48 years in patients, respectively. The QALE of 55 patients with partial cognitive ability and were able to respond was 0.58 quality-adjusted life years (QALY), while those of 87 patients with poor consciousness were 0.28 and 0.29 QALY, respectively, for EQ-5D measured by family caregivers and nurses. The sensitivity analysis did not show a significant difference between patients and their proxies based on different value systems in U.K. and U.S. The results of health gap were 94% and 97% for patients with a partial cognition and poor cognition, respectively.Moreover, the results can also serve as a starting point for a public dialogue on resources allocation of NHI on critical care, aging and palliative care. Future studies should further integrate the medical cost into the estimation of the cost per QALY gained together with consideration of reduction of health gap to preserve health equality. Figure 1. The life expectancy (namely, area under the dotted line) and loss of life expectancy (namely, shadowed area between the two curves) in years for 633 patients under PMV (prolonged mechanical ventilation) after extrapolation to 300 months. Conclusions Overall, the average QALE of patients under PMV was poor. Future studies of cost-effectiveness and reduction of health gap are indicated to preserve health equality. Figure 2. Quality adjusted survival for patients under PMV (prolonged mechanical ventilation) after adjustment of survival function (N=633) with the utility values of quality of life measured with EQ-5D. The upper and lower panels depict the results of patients’ preference values (N=55) and their family caregivers’ on behalf of them (N=87), respectively, with the QALE (quality-adjusted life expectancy) of 0.58 and 0.28 QALY by summing the areas under the quality-adjusted survival curves. Corresponding author’s e-mail: jdwang@ntu.edu.tw OMIH