Anemia and health performance score evaluation as decisive factors for noninvasive mechanical ventilation decisions in AECOPD: are there new key cornerstones?

Abstract

Dear editor Determination of prognosis of exacerbation of chronic obstructive pulmonary disease (AECOPD) is a key cornerstone for health cost, organization, systems, and influences determinations of rationale in the use of non-invasive ventilation (NIV).1 However, systemic complexity of AECOPD makes it difficult to establish a “gold and perfect” prognosis model.1 Recently, a growing number of biological parameters such as anemia and health performance score evaluations are becoming decisive factors for NIV decisions.2 In an interesting study, Haja Mydin et al determined that anemia, and performance status based on World Health Organization performance status (WHO-PS) were independent prognostic markers in acute hypercapnic respiratory failure (AHRF) due to AECOPD.3 The authors considered the major findings were that WHO-PS >3, and anemia, were the best prognostic factors to identify patients unlikely to benefit from NIV. We believe that the study makes a useful contribution to the establishment of predictors of poor prognosis in patients with AECOPD and it may help to make appropriate decisions for rational use of NIV. However, there are some concerns related to this study. Firstly, the mechanism of anemia in chronic obstructive pulmonary disease (COPD) and its impact on survival are still unclear; principally it may be associated with acute systemic inflammation in COPD. Nevertheless, anemia prevalence shows a wide range among studies (7.5%–34%) and many confounding factors associated to comorbidities may exist.4,5 Particularly, the major prevalence of women in this study as sex–factor, could be a conditioning factor. Furthermore, the study did not specify if anemia was associated with hospital readmission.5 Secondly, a high frequency of hospital admissions for AECOPD had no prognostic significance in this study, but it was not clarified if previous episodes needed NIV or endotracheal intubation.6 Previous reports show that the use of NIV during AECOPD may improve long-term outcomes, in comparison with traditional therapy, including endotracheal intubation.5,6 Thirdly, the authors consider that the APACHE II score7 is rarely used outside of the intensive care unit (ICU), in favor of more simple parameters. We do not agree with this interpretation, and believe it deserves some consideration as other studies have demonstrated the usefulness of the APACHE II score7 as a solid independent predictor of hospital mortality on multiple regression analysis studies, and a marker for NIV response and health organization in AECOPD, and at large. To our knowledge there are no studies showing that it is not useful in assessing prognosis. Low performance status is an established prognostic factor for poor outcomes for patients with AECOPD, but this information was well known before the widespread use of NIV in general hospitals.8 Finally, the patient population included in this study may be too low with not enough representation to perform a suitable search for independent prognostic markers of a varied clinical condition such as AECOPD. A previous study9 recruited a larger number of patients with a wider spectrum of severity eg, 1,033 consecutive patients in the multicenter Confalonieri et al study. Moreover, it was noted that the mortality rate was very high (33.8%), in comparison with the majority of randomized clinical trials on NIV in patients with acute hypercapnic failure due to COPD exacerbation, and even more than past studies including ICU patients before the NIV era.5,9 In conclusion, we agree that anemia and a low performance status could have a negative impact on the outcome of patients with AECOPD, but possible patient selection bias and the lack of a control group make the interpretation of the results less firm for Haja Mydin et al,3 with regards to the decision to use or not use NIV for ventilatory treatment.