Discussion

To our knowledge, this is the first study to analyze a nationally representative PMV dataset to estimate the incidence rates, CIR, and life expectancies stratified by age and different clusters of diagnoses. Our findings showed that new cases of PMV increased significantly from 9,296 to 21,818 between 1998 and 2004. The age-specific incidence rates increased as people grow older, a result that is consistent with previous reports from scholars in the U.S. and Canada [1-2, 4, 23]. However, the highest age-specific incidence rate of PMV was observed in patients older than 85 years in Taiwan, and this rate was approximately 4 to 5 times higher than those reported in the U.S. [24]. We attempted to quantify the lifetime risk of PMV by calculating the CIR17-85, which increased from 0.103 to 0.145 between 1998 and 2007 (Table 1.1). This finding implies that an adult person in Taiwan who lives until the age of 85 has 10-15% chance of requiring PMV. Given the resource-intensiveness of PMV, this issue requires special attention. When the Bureau of National Health Insurance of Taiwan began to audit the quality of the integrated respiratory care system in 2003, including the rates of successful weaning, readmission and nosocomial infection, the incidence of PMV

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-In the past, there has been a general lack of data regarding the life expectancies associated with different diagnoses for patients undergoing PMV. This has made it difficult for stakeholders to reach consensus clinical decisions regarding optimal treatment strategies. The issue becomes even more complicated when payment is provided via NHI or a third party. It is understandable that the patient and his/her family always expect successful weaning and good recovery, even after more than 21 days of continuous mechanical ventilation or PMV. However, according to our previous study, most patients undergoing PMV survive only approximately 1.5 to 2 years, and approximately 62% of them suffer from cognitive impairments and poor quality of life.

Accounting for these factors results in an overall quality-adjusted life expectancy of only 0.3-0.4 to 0.6-0.7 quality-adjusted life years (QALYs) [25-26]. Thus, this study further provided crucial estimates of the median survival and life expectancies of patients undergoing PMV with different diagnoses or co-morbidities, as summarized in Tables 1.2 and 1.3. Table 1.2 shows that the life expectancies were shortest for PMV patients with chronic renal failure and cancer or any condition co-morbid with them, followed by Parkinson’s disease and stroke. In contrast, the life expectancies for degenerative neurological diseases, liver cirrhosis, injuries and poisonings were greater than 3.6 years. When stratified by age categories, the median survival and life expectancies for PMV patients older than 85 years were below 4.6 months and 21.8 months, respectively, which were also observed for all of the different types of co-morbidities (Tables 1.2 and 1.3). The above figures call into question the cost-effectiveness of current policies and should be considered by policy makers and the public in discussions regarding the bioethics of PMV care, especially given the limited resources of the NHI in Taiwan. Although more and more countries have tried to implement the principle of universal coverage in their national health insurance plans

[27], our results provide data highlighting the needed evidence for developing strategies of sustainable management.

Although previous studies have shown similar characteristics of multiple co-morbidities in PMV patients, these reports did not stratify patients into special clusters [1, 9, 24, 28].

The LCA showed that the underlying co-morbidities associated with PMV could be largely classified into the major categories of heart diseases, septicaemia/shock, and chronic obstructive pulmonary disease based on the high prevalence of each cluster.

Overall, LCA indicates that the life expectancies generally decreased with older age. In particular, we found that approximately 50% of the PMV patients with a combination diagnosis of septicaemia and shock usually survived for less than 4 months, and their life expectancies were usually shorter than those determined for the other clusters within the same age stratum. The generally longer survival time of PMV patients with COPD corroborated the hypothesis that the establishment of mechanical ventilation provides more direct access for clinicians to solve problems coming from the respiratory tract, while patients with other underlying diseases may not be improved significantly unless their underlying disorders were also resolved. This advantage disappeared in individuals over 85 years of age because a high proportion of these COPD patients also suffered from other major diseases, including urinary tract infection (29%) and other respiratory diseases (26%), as shown in Table 1.3.

Our study has several limitations. First, the database did not contain any information regarding the severity and/or actual clinical data of the PMV patients. Thus, we were unable to further stratify these patients. However, because they were all under PMV care for more than 21 days, all of the patients were associated with extremely severe conditions, which resulted in a very short life expectancy and suggested that 10 years of

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-must fulfil all of the reimbursement regulations of the NHI, it is possible that some diagnoses are over-represented because they were more easily reimbursed. However, the National Health Insurance of Taiwan has offered a list of 30 major categories of catastrophic illnesses that are exempt from partial co-payments, and each has its specific diagnostic criteria to prevent any abuse [29]. For example, all types of malignant neoplasm do not require co-payments, and evidence of histopathology and/or cytology is generally required for diagnoses of cancer. A diagnosis of end stage renal disease requires documentation of chronic kidney disease with an irreversible creatinine level of

more than 8 mg/dL, or creatinine level more than 6 mg/dL with diabetes mellitus as a co-morbid condition [30]. Thus, we have strict criteria for almost all the major diagnoses listed in Table 1.2. The potential selection bias for the common diseases listed in Table 1.3 is probably minimal because the 43 broad categories were collapsed from the 260 categories of CCS codes [13], and latent class analysis ensured that each category was as homogeneous as possible.