**5. Clinical Presentation and Diagnosis**

#### **5.1. History**

Patients with an AECOPD usually present with dyspnea, which may be acute but can also be a history of slowly progressive dyspnea. Coughing or sputum production may or may not be present. When expectorating sputum, it is important to assess whether sputum volume has increased and whether it is purulent (e.g. green). Purulent sputum is usually a sign of infection [57]. Fever or other signs of infection should be looked for. Hemoptysis may be present in case of a severe infection. Risk factors for atypical infections should be thought of.

#### **5.2. Laboratory tests**

Laboratory test can be performed if necessary. C-reactive protein as marker for inflamma‐ tion can be performed. Additional laboratory tests can be performed depending on the differential diagnosis. If available, an arterial blood gas can be performed. Hypoxemia may be present and in more severe cases a patient can also retain CO2. Hypercapnia is defined as arterial blood gas CO2 (*P*aCO2) level above 45 mmHg (6,00 kPa) and hypercapnic respiratory failure as *P*aCO2 of >50 mmHg (6,67 kPa). When present it is important to assess if the hypercapnia is longer existing and to assess if the patient is being able to metabolical‐ ly compensate the hypercapnia.
