In this 5-year observational study, 7.3% of the patients with MV required PMV. PMV patients occupied ICU/HCU and hospital beds for an extraordinary amount of time and had higher hospital mortality than non-PMV patients. Emergency ICU admission and steroid use during MV were associated with PMV in multivariable logistic regression analysis. Further, most PMV patients were liberated from MV whether they survived to discharge or not, and 12.9% still required MV at discharge. Six months after discharge, mortality rate of these patients was 41.6%, and only 8.3% survived with successful liberation from MV.
Relationship with previous studies
According to the previous observational studies, the rates of PMV patients against those with MV were 5.1–28.0% [2,3,4, 12,13,14, 20]. In addition, previous studies have shown that PMV patients had a longer duration of MV, ICU stay, and hospital stay compared with those who did not. According to these studies, duration of MV among PMV patients was 29–51 days, ICU stay was 33–52 days, and hospital stay was 51–77 days [2, 4, 12,13,14, 20]. These studies were conducted in countries lacking the concept of weaning centers, and the results were consistent with those observed in our study.
In our study, emergency ICU admission and steroid use during MV were associated with PMV in multivariable logistic regression analysis. Since few studies have investigated factors related to PMV, we applied the following variables that could potentially affect the development of PMV: age, sex, type of admission to ICU, acute respiratory disease, septic shock, APACHE II score, and steroid use and neuromuscular blocker use during MV, with reference to the factors related to longer duration of MV . In a previous study, the rate of emergency ICU admission in PMV patients was higher than that of non-PMV patients in univariate analysis . Also, previous studies have reported that a large majority of PMV patients were admitted to ICU due to emergency medical reasons including sepsis, respiratory disease, and trauma which is consistent with our study [2,3,4, 14]. Therefore, emergency ICU admission may be a predictor associated with development of PMV. In addition, although the relationship between ICU-acquired weakness (ICUAW) and steroid use remains controversial [22, 23], steroid use may affect weakness of the respiratory muscle including diaphragm, and thus may prolong the MV duration. However, because the sample size was limited, some confounding factors may exit in the association between PMV and steroid use. Further researches are needed to investigate the risk factor for PMV.
An earlier study in a single RWC showed that the 6-month and 1-year mortality after discharge of patients who still required MV was 65.3% and 78.7%, respectively . A systematic review and meta-analysis reported that pooled 1-year mortality of PMV patients discharged from post-acute care hospitals such as LTACHs was 59% . In our study, 6-month mortality after discharge of PMV patients was 41.6%. Further, it was difficult to compare our study with previous studies [11, 24], due to differences in the research setting. In any case, the long-term mortality of PMV patients was expected to be high. Nevertheless, at present, optimal patient selection at the time of MV initiation remains unclear and is a target for future research.
Significance and implications
Previous studies conducted in LTACHs and RWCs reported the rate of patients liberated from MV and survived to discharge to be 35.0–54.1% [8,9,10,11, 25, 26]. A previous study conducted in an LTACH showed median time to be liberated from MV was 13.5 days, median days on MV before transfer was 29 days, and total duration of MV was 42.5 days . Another multicenter study conducted in LTACHs reported that median time to be liberated from MV was 15 days, median days on MV before transfer was 25 days, and total duration of MV was 40 days . Although research setting was different, these results were similar to those of our study wherein the rate of patients who were liberated from MV and discharged alive against PMV patients was 31.2%; most PMV patients were successfully released from MV within 60 days; and the median duration of MV was 37.0 days. These data indicate that ICUs and HCUs in acute care hospitals in Japan play a role of LTACHs or RWCs.
In our study, MV was applied in ICU/HCU for up to 135 days, which was far longer than the coverage period of ICU/HCU payment (up to 14 days for ICU payment and up to 21 days for ICU/HCU payment in a single admission). Although liberation from MV in PMV patients requires a certain degree of workload on intensivists, most of this effort is not covered by the current payment system in DPC hospitals, consequently burdening acute care hospitals with the economic load. As a result, clinical decisions regarding mechanical ventilation may be made in a less aggressive manner due to financial reasons. Moreover, occupying ICU or HCU beds for an extended period may interfere with admission of other critically ill patients, thereby potentially infringing fair allocation of limited critical care resources .
Whether to have specialized centers for PMV patients who need long-term acute care remains contentious. Although PMV patients might be regarded as “outlier” subjects in the ordinary care process of critically ill patients, our results indicated that 7.3% of MV patients were shifted to PMV, which is a substantial proportion. A multicenter investigation performed in the UK reported that establishing weaning centers would potentially reduce acute bed occupancy by 8–10% and overall treatment costs . Because health insurance systems among countries are diverse, this estimation cannot be directly applied to Japan. However, nationwide data demonstrating an overall picture of PMV in Japan is needed.
Strengths and limitations
To the best of our knowledge, this is the first study to describe the clinical features and long-term outcomes, including post-discharge outcomes, of PMV patients in the acute care setting in Japan. However, our study has several limitations. First, as this study was a single-center study, the sample size was limited, and all the important data that affected PMV may not have been collected. Therefore, it may affect our results of multivariable logistic regression analysis. Second, our hospital is a tertiary care hospital that has an emergency and critical care center and located in the metropolitan area. Our results might be useful to other acute care hospitals with similar characteristics. However, it was not clear if our results apply to hospitals with different features such as academic hospitals comprising only surgical ICUs. Lastly, our ICU comprises a mixed and high-intensity ICU with many board-certified intensivists. Reportedly, not many ICUs in Japan had > 1 intensivists and were managed with high-intensity policy . Therefore, decision-making to initiate MV, managing policy for MV patients, and number of efforts that were applied to PMV patients of other hospitals might differ from those of our hospital.