This prospective observational study will evaluate the accuracy of the Welch Allyn Connex Spot Monitor equipped with a Masimo SpO₂ finger sensor in measuring respiratory rate in the emergency department. Respiratory rate is a key predictor of patient deterioration, yet it is frequently measured inaccurately when assessed manually. In this study, respiratory rate values obtained by the monitor will be compared against manual counts performed by trained observers (physicians). An additional analysis will compare respiratory rates measured by trained observers with those recorded by triage nurses during triage. A subgroup analysis will also investigate whether cardiac arrhythmias influence measurement accuracy.

The aim is to examine if respiratory rates measured by the Welch Allyn Connex Spot Monitor are comparable to those obtained by trained observers and triage nurses in the emergency department.

Design: prospective observational method comparison study

Inclusion Criteria:

- all patients aged ≥18 years.

Exclusion Criteria:

• patients receiving invasive or non-invasive respiratory support;
• patients with disorders causing involuntary movements;
• skin or digit abnormalities preventing proper application of the pulse oximeter;
• clinically unstable patients on arrival (requiring immediate transfer to the resuscitation area);
• patients with a left ventricular assist device (LVAD).

The study will be conducted on patients admitted to the Emergency Department of Semmelweis University.