Risk of death and readmission of hospital-admitted COPD exacerbations: European COPD Audit

Discussion

This study presents the largest European dataset of prospectively collected real-world data of quality of care and outcomes for hospital-admitted COPD exacerbation. The study confirms the findings from smaller national audits and highlights gaps in quality of care in many European countries when compared with evidence-based recommendations, and importantly provides insights into where interventions could be made which might improve outcomes for patients.

Acidotic respiratory failure on admission and the subsequent need for ventilatory support were found to be important and consistent predictors of in-hospital mortality and post-discharge mortality. The only factor associated with a reduced risk of death during the 90-day post-discharge follow-up was the number of respiratory specialists per 1000 beds.

Respiratory acidosis, reflecting the severity of the exacerbation, was a finding in 18.8% of admitted patients with blood gases available. National COPD audits from the UK and Spain [13, 14] have reported similar proportions of respiratory acidosis, and this European audit confirms the previous findings. Respiratory acidosis, when split into severe (pH <7.25) and mild (pH 7.25–7.35) as a surrogate of the severity of the exacerbation, was a strong predictor of in-hospital and post-discharge mortality. It is therefore of concern that 18.5% of patients were assessed and managed without this information. Blood gas analysis is recommended in COPD guidelines [15, 16] and although incomplete adherence to these recommendations was first reported in the 1997 UK COPD Audit [17], it is concerning to report similar figures across Europe 13 years later.

Respiratory acidosis is considered a modifiable condition in the acute setting and noninvasive ventilation (NIV) is one of the very few interventions with strong evidence from the published literature to effectively reduce mortality [18–20]. The high mortality of COPD patients with severely impaired respiratory function has been noted since the early 1990s [1, 21, 22], but was improved by early ventilation for mild respiratory acidosis in randomised controlled trials (RCTs) [21]. These survival benefits are incompletely transferred into everyday practice, as exemplified by a 45.0% ventilation rate of mild acidotic patients in the present study. Moreover, the number of intubated patients after NIV failure was very small, indicating that NIV was a ceiling therapy for most of the cases who died after NIV. Reasons for delaying or withholding NIV are dependent on physicians’ decisions, but may also be influenced by the availability of NIV and access to the intensive care unit (ICU) for COPD patients, as first reported by Roberts et al. [14] and confirmed by this European COPD Audit [9]. This is alarming when guidelines recommend that NIV should be delivered in a dedicated setting and ICU admission should be considered in respiratory failure for COPD [16]. It is likely to be key that the medical team with the appropriate knowledge and skills is on hand to make these critical decisions. It is noteworthy that the audit demonstrated an association between reduced post-discharge mortality and the ratio of respiratory specialists to beds, which supports the view that early access to specialists may be the optimum service model.

On the basis of these findings, we recommend that European hospitals develop a COPD care pathway which includes the analysis of arterial blood gases on admission and a subsequent decision model for acidotic patients to receive NIV as indicated by a respiratory specialist comparable with the acute intervention model for myocardial infarction [23].

We observed a 35.1% readmission rate for all patients discharged within 90 days, which was also strongly related to post-discharge mortality. Readmission is still considered to be avoidable and led to the establishment of a penalty system for readmission within 30 days in the USA [24–26]. However, the prediction of readmission is still poor and most of the published data fail to show any improvement of readmission rates in COPD as a result of financial penalties [26, 27]. In our study, readmission was related to the risk factor of previous admissions, thereby possibly reflecting the frequent exacerbator phenotype.

Pulmonary rehabilitation programmes following acute exacerbation of COPD have effectively reduced readmission and mortality [28, 29]. Moreover the inclusion of a number of interventions into a discharge care bundle [30, 31] has also been shown to reduce readmission rates. Identification of the risk factors highly associated with readmission rate would allow more vigorous post-discharge care bundles to be tailored for these patients.

The CCI, but no specific disease group, although a fair number of specific comorbidities was investigated, was associated with increased in-hospital and post-discharge mortality.

The lower risk of readmission and post-discharge mortality associated with diabetes confirmed the findings of previous smaller studies [32, 33], but does not elucidate the possible underlying mechanisms. The thesis of the protective potential of a higher body mass index in diabetic patients has been discussed by McGhan et al. [32], but is still speculative. Another explanation model is that comorbidities may include unidentified treatment options which in diabetes therapy might lead to less blood sugar escalation caused by systemic corticosteroid therapy considered harmful in the studies of Baker et al. [34] and Chakrabarti et al. [35].

Lung function test results to confirm the diagnosis of COPD and categorise the severity of disease were not available in >50% of patients at the time of admission. When available, COPD stage IV patients had a higher need of ventilatory support. Spirometry data available to admitting clinicians would help to confirm the diagnosis and to risk-stratify patients. The availability of spirometry would probably both influence the decision model of acute care and the discharge care bundle.

We acknowledge that the European COPD Audit has limitations as it was established as a pilot to evaluate the potential for widespread European data collection. Thus, selection bias relating to the voluntarily participating centres clearly could be an issue. Participating hospitals at the national level were not randomly recruited, which resulted in wide variations of the catchment of population between countries. Thus, results of a single country are not considered to be representative of the national COPD population. However, for countries such as the UK and Spain with the highest experience in national audits [36, 37] there were not significant differences in results when a smaller number of centres participated in the European Audit. The lack of data from European countries such as Germany and France does, however, limit the generalisation of the results across all Europe. Moreover, audit data do not compare with the standards of RCTs and the absence of spirometry in half of the included cases raises issues about the confirmation of diagnosis. Nevertheless, the audit is an accurate reflection of real-world clinical practice, and highlights the gaps between the RCT-based evidence of ideal clinical practice and the standards delivered in routine care.

The pilot study was not designed to detect barriers to the implementation of guideline recommendations, but only shows the gaps of quality of care. The intention of an audit is to identify the deficiencies of care measured against standards and then to challenge clinicians to form action plans to improve care before again measuring the quality of the care given to patients in their practice [38].

In summary, the European COPD Audit identifies areas of clinical practice which if improved should result in better outcomes for patients. It is unacceptable that half of all patients admitted with COPD do not have documented spirometry to confirm the diagnosis nor to stratify the risk to the individual. It is also unacceptable that a fifth of patients do not undergo blood gas analysis for critical decision making regarding ventilatory support. In addition, the study identifies the number of respiratory physicians as a modifiable risk factor to influence post-discharge mortality.

In conclusion, the study asks for optimising the risk stratification on admission for COPD exacerbation, identifying respiratory acidosis effectively in the first hours of an admission, deploying specialist respiratory care teams in time and following these risk factors at discharge to implement evidence-based interventions.