Background of the study The respiratory rate (RR) is an important vital sign to be monitored in the emergency room, as it is a sensitive predictor of risk and critical illness . An increased RR is a sensitive and independent marker of increased mortality in patients with community acquired pneumonia and in unselected patients presenting to the emergency department (ED): This is why the RR is a component in many risk scores for prediction of adverse outcomes, such as the 'Confusion/Urea/Respiratory rate/Blood pressure/-Age 65 or older' (CURB-65) score, the Modified Early Warning Score (MEWS), Trauma Score, Revised Trauma Score, APACHE II (Acute Physiology and Chronic Health Evaluation) and PRISM (Paediatric Risk of Mortality ). Additionally, it is part of the Systemic Inflammatory Response Syndrome (SIRS) Sepsis-definition and definitions for weaning a patient from a ventilator (RSBI, Rapid Shallow Breathing Index, ). In some cases, measurement of the oxygen saturation is not sufficient as tachypnoea may not always have a connection to hypoxia . Hence, RR plays an important role in triage of patients presenting to the emergency room. Especially tachypnoea brings the need for more detailed monitoring and investigation. Tachypnea/Bradypnoea can be seen as a red flag and may indicate a big variety of diseases like heart failure, pneumonia, metabolic disturbances or pulmonary embolism. Recent studies could demonstrate that also trends of RR are reliable predictors of clinical outcome. Especially an increase in tachypnoea during hospitalisation is associated with high mortality A careful and exact measurement is essential. In emergency situations the RR is one component of the Emergency Severity Index (ESI) algorithm and a mandatory vital sign measured at decision point "D". However, its measurement is often omitted due to time constraints . Moreover documented pathologic RR in ER scenarios indicating hypoxia are often neglected leading to fatal events and contributing to deaths caused by medical errors.

According to recommendations of the World Health Organization (WHO) the RR should be measured by counting the breaths over a period of 1 minute by counting how many times the chest rises. This should be done when the patient is at rest. This appears impractical due to time consumption and workload for nursing staff in an emergency department. Studies have shown that this fact is a main reason why RR is often not recorded and critical situations might be missed. A prospective study by Lovett et al. demonstrated that the measurement of RR by nursing staff and even by impedance plethysmography as a common used device have a low sensitivity in detecting brady- or tachypnoea. The vital sign measurements may also differ according to observer variability. The approach to use mobile devices for RR measurement has shown encouraging results to improve efficiency in comparison to traditional methods though the field of using mobile devices is still in an experimental stadium.

The investigators aim to compare the results given by the camera-based measurements to the results given by capnography. The goal of the survey is to analyse the accuracy of measurements performed by the software.

The investigators will recruit healthy volunteers without any history of pulmonary diseases for an analysis of RR monitoring. Upon agreement the investigators will measure the RR camera-based by a device and simultaneously count the RR by capnography as a reference method. The data will be collected through a standardised protocol and archived in an Access(R) database. Different settings (e.g. supine vs sitting) will be assessed. Results will be depicted in a Bland-Altmann plot. In a first step the investigators plan to do a feasibility study, after that, as a second step, they will continue to measure the RR in different positions and situations to simulate a situation similar to emergency conditions.