The aim of this study is to examine if automated oxygen delivery with O2matic allows for faster weaning from oxygen supply and better oxygen control than manually controlled oxygen therapy for patients admitted to the emergency department with acute hypoxemia. Furthermore it will be tested if O2matic compared to manual control allows for earlier discharge.

Closed-loop control of oxygen therapy is described in the literature used for preterm infants, trauma patients, medical emergency use, and for patients with Chronic Obstructive Pulmonary Disease (COPD). O2matic is a closed-loop system that is based on continuous and non-invasive measurement of pulse rate and oxygen-saturation (SpO2). The algorithm in O2matic controls oxygen delivery with the aim of keeping the SpO2 within the desired interval, which could be 88-92 % for patients at risk of hypercapnia or 94-98 % for patients with pneumonia, asthma exacerbation, heart failure and other medical emergencies, according to guidelines from British Thoracic Society (BTS). SpO2-interval can be set for the individual patients, as can the range of acceptable oxygen-flow. If SpO2 or oxygen-flow cannot be maintained within the desired intervals an alarm will sound.

All studies on closed-loop systems have shown that this method is better than manually control by nurse to maintain saturation within the desired interval. Furthermore, some studies have indicated that closed-loop has the possibility to reduce admission time and to reduce time spent with oxygen therapy, due to more efficient and faster withdrawal from oxygen supplementation.

In the present study O2matic will be tested versus manual control, for patients admitted to the emergency department with acute hypoxemia due to any reason, except for carbon monoxide (CO) poisoning and other conditions where SpO2 is not a reliable measure of hypoxemia. During the study the patients will either have oxygen controlled with O2matic or manually by nursing staff for 24 hours or until discharge or weaning from oxygen supply. All patients will have continuous logging of pulse rate, oxygen-saturation and oxygen-flow with O2matic, but only in the O2matic active group, the algorithm will control oxygen-delivery.

The primary hypothesis is that O2matic compared to manual control allows for faster weaning from oxygen supplementation, and that more patients will be weaned from oxygen supplementation within a time frame of 24 hours. Furthermore it will be tested if O2matic compared to manual control allows for earlier hospital discharge. It will be tested if O2matic is better than manual control in maintaining oxygen-saturation within the desired interval and reducing time with unintended hypoxia and hyperoxia.

No safety issues has been reported in the literature. O2matic is approved in Europe with "Conformité Européenne" (CE) mark, and approved for clinical testing by The Danish Medicines Agency, The Ethics Committee in the Capital Region of Denmark and by the regional Data Protection Board. The study will be conducted according to Good Clinical Practice (GCP) standards with independent monitoring. All adverse events and serious adverse events will be monitored and serious adverse events will be reported to Danish Medicines Agency.

Inclusion Criteria:

• Admission with hypoxemic respiratory failure
• Age >= 18 years
• Expected duration of admission > 24 hours
• Need for oxygen supplementation to maintain SpO2 >= 88 % (patients at risk of hypercapnia) or SpO2 >= 94 % (other patients)
• Cognitively able to participate in the study
• Willing to participate and give informed consent

Exclusion Criteria:

• Need or anticipated need for mechanical ventilation (intermittent Continuous Positive Airway Pressure (CPAP) is allowed)
• Patients with CO-poisoning or other condition with unreliable SpO2.
• Patients in need of oxygen supplementation at more than 10 liters/min
• Pregnancy
• Cognitive or language barriers for participation