Introduction: The use of ultrasound protocols has revolutionized care in emergency medicine and can help in the diagnosis of respiratory failure in emergency care; therefore, medical training for the use of these protocols has become important. It has also been demonstrated that medical smartphone apps have positive results in daily practice, in addition to being a potentially valuable educational tool. Objective: Thus, the objective was to develop an emergency pulmonary ultrasound application. The “BLUE SIM” is a cell phone application that simulates clinical cases using the “Bedside Lung Ultrasound in Emergency” protocol, which can help students and health professionals regarding the use of pulmonary ultrasound in the care of acute respiratory failure. The hypothesis is that the “BLUE SIM” will be a usable and acceptable application among users. Method: After the development, the application was evaluated with a group of 36 volunteers, which included 18 physical therapists and 18 other professionals consisting of physicians, nurses and medical students. The usability and usefulness of a mobile application for the iOS system was analyzed, using the System Utility Score (SUS) usability scale and the Technology Acceptance Model (TAM) as references. The obtained data were tabulated and analyzed using Fisher’s exact test or Mann-Whitney test. Result: When applying the SUS questionnaire (usability), the application obtained a score of 76.8%. A score of 75% was obtained exclusively among physical therapists, with no statistical difference between the general group of all emergency professionals and the group of physical therapists only (p=0.239). According to the usefulness perception analysis, 93.9% of the emergency professionals had a positive response, while a score of 88.9% was obtained among physical therapists (p=0.04). Conclusion: It was concluded that the developed application was classified as useful in learning the diagnosis of respiratory failure among health professionals; however, they considered that training is necessary for its use.