Study Identifies Patient Risk Factors for In-hospital Death
These factors include the need for invasive mechanical ventilation (IMV), having chronic heart failure, and having a low number of immune white blood cells, the study found.
Specifically, 65.9% of patients who died required invasive ventilation as compared with 7.1% of survivors.
“Hospitalization for acute COPD exacerbation is becoming more frequent, and it places an enormous burden on patients and health care systems,” according to the researchers, who added that “recognizing factors associated with mortality in these patients could reduce health care costs and improve end-of-life care.”
The study, “Predictors of mortality in COPD exacerbation cases presenting to the respiratory intensive care unit,” was published in Respiratory Research.
COPD patients who experience acute exacerbations or AECOPD — flare-ups in which breathing usually worsens — frequently require hospitalization. Acute exacerbations may reduce lung function and quality of life, and are associated with high hospital mortality rates, meaning a high number of patient deaths.
Although previous studies have already identified clinical features that can contribute to mortality in people with AECOPD, few have included patients who have specifically been admitted to a respiratory intensive care unit (RICU).
“Knowledge about prognosis of disease and factors that predict poor outcome is important to help physicians to advise patients on the expected natural course of an illness,” the investigators wrote.
Now, researchers in China sought to identify the risk factors that may predict in-hospital mortality. To do that, the team retrospectively analyzed the medical records of 384 patients diagnosed with AECOPD who were admitted to the RICU at Beijing Hospital from January 2011 to December 2018.
AECOPD was defined as worsening of shortness of breath, increased cough and/or phlegm (sputum) quantity, or phlegm with pus that required further treatment.
Patients were on average 78.2 years old, and there were more men (72.9%) than women (27.1%) in the group analyzed.
A total of 44 (11.5%) of the AECOPD patients admitted to the RICU died in the hospital and 340 (88.5%) survived.
Those who died needed ventilation for a longer period of time than was required by survivors — a mean of 438.3 hours (more than 18 days) compared with 269.7 hours (about 11 days). The need for more intensive breathing assistance, or IMV, also was higher in the group of patients who died (65.9% versus 7.1% among survivors).
Ventilation is considered invasive if oxygen support is provided via either an endotracheal tube (a tube placed through the mouth into the trachea, or windpipe) or a tracheostomy tube (a tube inserted into a tracheostomy stoma, or the hole made in the neck into the trachea). Non-invasive ventilation, or NIV, meanwhile, usually consists of oxygen given via a face mask.
“The results of the present study were consistent with previous studies. This finding is not surprising: typically, patients who require IMV rather than NIV [non-invasive ventilation] are in a severe disease stage,” the researchers wrote.
The results also showed that those who died had a lower activities of daily living index (ADL) at admission (mean of 28.6) than did survivors (mean 43.1). Patients with a lower ADL have less capacity for basic activities of daily living, such as self-care.
The team also investigated the presence of other medical conditions (comorbidities) besides COPD among the entire patient population in the study. Respiratory failure — affecting 76.6% — of patients was the most common co-existing condition, followed by hypertension (55.7%), coronary heart disease (29.9%), and chronic heart failure (19.8%).
Notably, chronic heart failure was more frequent among the patients who died than in survivors (50.0% versus 15.9%).
Next, a panel of laboratory tests was carried out to search for factors associated with an increased risk of in-hospital mortality. Patients who did not survive were found to have had higher levels of leukocytes, or white blood cells, but lower levels of lymphocytes — a specific type of leukocyte that helps fight infections.
Additionally, a lower number of those who died had lymphocytopenia, a condition defined as having particularly low levels of lymphocytes, as compared with those who survived.
Three inflammation markers — neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and creatinine (CRP) — also were higher in the patients who died. Likewise, levels of NT-proBNP, an indicator of heart failure, and D-dimer, an indirect measure of blood clotting, also were increased in those who did not survivors. No significant differences were seen in lung function when comparing those who died to the survivors.
Using statistical analysis, the team identified chronic heart failure, having reduced levels of white blood cells, lymphocytopenia, and the need for IMV as independent risk factors of in-hospital mortality in AECOPD patients in RICU.
“Requirement for IMV was a significant predictor of in-hospital mortality of AECOPD,” the researchers said. In fact, the odds of dying were about 30 times greater (odds ratio of 30.31) in those who needed IMV.
The odds of death were found to be 7.63 times greater in those with chronic heart failure, 5.77 times higher among those with reduced levels of white blood cells, and 3.60 times higher in those with lymphocytopenia. Overall, according to the researchers, odds ratio values higher than one show an increased likelihood of in-hospital death.
“In the present study, lymphocyte count was shown to be a useful, widely available, and inexpensive predictor that may help identify AECOPD patients admitted to the RICU at high risk of in-hospital mortality,” the researchers suggested.
The study did have certain limitations, the scientists noted, including a lack of information on the patients’ nutritional status or quality of life prior to admission. It also was based on patients only treated at a single hospital.