Chest pain with shortness...

A 68-year-old man presented with complaints of sudden onset chest pain and shortness of breath. His medical history was significant for emphysema and for a 30 pack-year history of smoking. There was no history of recent trauma. 

Upon arrival at the Emergency Department, the patient’s blood pressure was 148/95 mm Hg, pulse was 91 beats/min, respiratory rate was 16 breaths/min, and temperature was 35.8C (96.4F). Pulse oximetry measured oxygen saturation at 93%. 

On physical examination the patient did not display signs of respiratory distress, but a rub was described on the right side. An ECG was obtained, which was flagged for suspected arm lead reversal (Figure 1). The ECG had inverted P waves in lead I and right-axis deviation, but chest leads had a normal progression. The limb leads were removed, then put back on the patient; correct placement was confirmed, and a second ECG was obtained. The second ECG also was flagged for suspected arm lead reversal and had inverted P waves in lead I and right-axis deviation. A chest X ray was done. Tube thoracostomy with a pleural catheter resulted in expansion of the right lung, with resolution of symptoms. A third ECG was then obtained, which showed resolution of previous ECG findings; the P waves in lead I were now upright, and the axis was normal (Figure 3). The full ECGs prior to and after tube thoracostomy have been provided for comparison (Figures 4, 5).