COPD is one of the leading causes of morbidity, mortality and health care utilisation worldwide. Currently, COPD is the third leading cause of death worldwide and is therefore a major public health problem. Projections show an increase in the prevalence and burden of COPD in the coming decades due to ageing populations and continued exposure to risk factors.

In patients with COPD, mortality due to exacerbations is about 35%. Exacerbations represent the most important respiratory event in the history of this chronic disease and are of major socio-economic interest (about 50-75% of healthcare expenditure in this disease).

In the most severe cases, COPD exacerbations lead to respiratory distress with hypercapnic ventilatory acidosis requiring ventilatory support. These most severe episodes are common, accounting for 20% of exacerbations and are a signal of advanced disease, with a high risk of future hospitalisations and a limited long-term prognosis.

Despite progress in management, the mortality of these severe acute exacerbations is around 15% in the ICU and 20% in hospital. The long-term prognosis following hospitalisation for an acute exacerbation of COPD is poor with a 5-year mortality of around 50%. On the one hand, the means and treatments likely to improve the prognosis of these patients are of great medical and socio-economic interest, on the other hand, it seems important to identify the elements that may be associated with management failure and to treat them where appropriate.

Thus, improving scientific knowledge thanks to prospective data, evaluating the different characteristics and prognosis of patients hospitalised for a severe acute exacerbation of COPD seems, in the 21st century, a major axis in order to continue to optimise the individual management of these patients but also collectively, given the COPD public health burden.

Inclusion Criteria:

1. Age ≥ 40 years old

2. COPD documented or strongly suspected

   • Chronic respiratory symptoms (dyspnoea, cough and/or sputum)
   • Exposure to a known risk factor for COPD (such as tobacco smoke)
   • If available, respiratory function tests showing non- or partially reversible obstructive syndrome (post-bronchodilator ratio FEV1/CV < 0.7)

3. Severe acute exacerbation, defined as a worsening of the patient's usual respiratory symptoms with signs of acute respiratory distress (polypnoea ≥ 30 cycles.min-1 or use of accessory respiratory muscles) and/or hypercapnic acidosis (with PaCO2 ≥ 45 mmHg and pH ≤ 7.35)

4. Admission to an ICU, or a dedicated respiratory intensive care unit

Exclusion Criteria:

1. Known asthma (according to the criteria of the international "Global Initiative for Asthma" guidelines)
2. Patient refusal to participate (information note, application for non-opposition)

Patients admitted to ICU, a step-unit or respiratory care unit for a severe acute exacerbation of COPD