Paradoxical respiratory sinus arrhythmia due to a large thoracic empyema in an ambulatory patient

•We report a case of thoracic empyema causing paradoxical RSA.•RSA is believed to enhance tidal volume efficacy and reduce intrapulmonary shunting.•Empyema caused respiratory phase related dynamic biventricular outflow obstruction.•PRSA and biventricular outflow obstruction was relieved on evacuation of empyema.

We report a case of paradoxical respiratory sinus arrhythmia (PRSA) caused by a retro-cardiac empyema in an ambulatory patient. The case describes the dynamics and deleterious impact of PRSA on cardio-respiratory cycle, its electrocardiographic, radiologic and echocardiographic findings. Furthermore, it discusses a probable mechanism of paradoxical respiratory sinus arrhythmia in the setting of a retrocardiac mass and suggests a need for physicians to check for the changes in ventilation perfusion mismatch and rise in physiological dead space in such patients. In conclusion, to the best of our knowledge, this is the first documented report of paradoxical respiratory sinus arrhythmia in an ambulatory, non-anesthetized spontaneously breathing patient.