He Hangyong, Sun Ying, Sun Bing, Zhan Qingyuan
Department of Respiratory and Critical Care Medicine, Beijing Institute of Respiratory Medicine, Beijing Chao-Yang Hospital, Capital Medical University, No.8 Gongti Nanlu, Beijing 100020, China.
Department of Pulmonary and Critical Care Medicine, China-Japan Friendship Hospital, No.2 Yinghuadongjie, Chaoyang district Beijing 100029, China.
Clin Respir J. 2018 Feb;12(2):491-498. doi: 10.1111/crj.12549. Epub 2016 Sep 28.
To evaluate the mortality risk factors of patients with severe chronic obstructive pulmonary disease (COPD) in the intensive care unit (ICU) by utilizing parametric model of survival analysis, and to estimate patients' prognoses based on the risk and survival functions in the model.
The clinical data and outcomes of COPD patients admitted to a respiratory intensive care unit (RICU) at Beijing Chao-Yang Hospital from January 2009 to June 2014 were prospectively collected. Based on the clinical outcomes, these patients were divided into a survival group and a death group. A univariate analysis was conducted to identify statistically significant variables. According to the distribution characteristics of these data, residual plots were prepared for an exponential model, a Weibull model and a Gamma model. The Gamma model was determined to be the best fitted for these data and was used as the analytical tool. Therefore, the variables with differences obtained from the univariate analysis were put into the Gamma model to determine the patients' mortality risk factors. The risk and survival functions were also generated according to the model formula.
A total of 160 patients (111 survival, 49 death) were enrolled. The univariate analysis showed that, compared with the survival group, patients in the death group had higher Charlson Comorbidity Index score (CCI), higher body temperature, higher white blood cell counts, higher proportions of neutrophils, higher serum creatinine levels and higher pH levels; lower resting carbon dioxide pressure (PCO ); and more cases complicated with invasive pulmonary aspergillosis (IPA). A further analysis with the Gamma model revealed that concurrent or non-concurrent IPA, white blood cell count, pH level and PCO were associated with the patients' mortality risk and that the predicted value (PV) of the patients' mortality risk = 2.8655 + 0.4070 × IPA + 0.0048 × WBC + 0.0049 × pH - 0.0097 × PCO . Moreover, the survival function formula was obtained according to the Gamma model: S(x) = 1 - I (0.7507 x, -3.3773), where I is an incomplete gamma function.
Formula generated from parametric model may help to predict the prognosis of patients with severe COPD in ICU, and this method need to be evaluated in further studies. According to our formula, IPA is an important risk factor of mortality for patients with severe COPD in the ICU.
利用生存分析参数模型评估重症监护病房（ICU）中重度慢性阻塞性肺疾病（COPD）患者的死亡风险因素，并基于模型中的风险和生存函数估计患者的预后。
前瞻性收集2009年1月至2014年6月在北京朝阳医院呼吸重症监护病房（RICU）收治的COPD患者的临床资料和结局。根据临床结局，将这些患者分为生存组和死亡组。进行单因素分析以确定具有统计学意义的变量。根据这些数据的分布特征，为指数模型、威布尔模型和伽马模型绘制残差图。确定伽马模型最适合这些数据，并将其用作分析工具。因此，将单因素分析中获得的有差异的变量纳入伽马模型以确定患者的死亡风险因素。还根据模型公式生成风险和生存函数。
共纳入160例患者（111例生存，49例死亡）。单因素分析显示，与生存组相比，死亡组患者的查尔森合并症指数（CCI）得分更高、体温更高、白细胞计数更高、中性粒细胞比例更高、血清肌酐水平更高、pH值更高；静息二氧化碳分压（PCO）更低；侵袭性肺曲霉病（IPA）合并症更多。用伽马模型进一步分析显示，并发或非并发IPA、白细胞计数、pH值和PCO与患者的死亡风险相关，患者死亡风险预测值（PV）=2.8655 + 0.4070×IPA + 0.0048×白细胞（WBC）+ 0.0049×pH - 0.0097×PCO。此外，根据伽马模型获得生存函数公式：S(x)=1 - I(0.7507x, -3.3773)，其中I是不完全伽马函数。
参数模型生成的公式可能有助于预测ICU中重度COPD患者的预后，该方法需要在进一步研究中进行评估。根据我们的公式，IPA是ICU中重度COPD患者死亡的重要风险因素。
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