The study will be conducted as a single-center, prospective cohort study. The primary objective of this study is to investigate the responsiveness of sonographic parameters of diaphragm to detect change in Borg score for dyspnea during hospitalisation for AECOPD without respiratory acidosis.

To investigate the responsiveness of sonographic parameters to detect change in Borg score for dyspnea during hospitalisation for AECOPD without respiratory acidosis, we propose a prospective cohort design.

After inclusion, participants will have assessment of diaphragm function (excursion, thickness, thickening fraction) using ultrasound within 48 hours of admission to the emergency ward, striving to assessment within 24 hours of admission. Additionally, dyspnea grade will be assessed using validated questionnaires.

Further diagnostic work-up and treatment for AECOPD is performed at the discretion of the treating physician.

Both ultrasound measurements and dyspnea grade questionnaires will be repeated when the participant is reported suitable for hospital discharge by the treating physician.

Inclusion Criteria:

• Hospitalisation primarily because of severe acute exacerbation of COPD
• COPD, according to GOLD 2018 definition
• Post-bronchodilator FEV1/FVC < 0,70 and FEV1% < 80%pred. within last 5 years

Exclusion Criteria:

• Respiratory acidosis (pH < 7.35 ánd PaCO2 > 6 kPA)
• Need for (non-)invasive ventilation based on other criteria (e.g. severe hypoxia) upon presentation.
• Established diagnosis of diaphragm diaphragm paralysis.
• Inability for diaphragm imaging (e.g. mechanical ventilation, or unable to follow vocal instructions).
• Those not able or unwilling to give written informed consent.
• Pregnant women

Our population consists of 18-years or older patients who are hospitalised primarily due to AECOPD without respiratory acidosis.