Background: Pneumothorax is a known complication of laparoscopy, with most pneumothoraces diagnosed postoperatively with conventional chest x-ray. Electrocardiogram (ECG) conduction changes are associated with pneumothorax. In a sheep model, ECG changes were evaluated as a potential indicator of intraoperative pneumothorax. Additionally, resolution rates of helium (He) and carbon dioxide (CO2) pneumothorax were also evaluated in this model.
Methods: Under general anesthesia, 10 sheep had known volumes (20-100 cc) of either He or CO2 introduced into the left hemithorax. A 12-lead ECG recorded changes associated with the induced pneumothorax. After changes in the ECG plateaued, the gas volume in the hemithorax was increased to 2 L and the resultant pneumothorax was followed for a 2-h period using fluoroscopy to determine resolution rates for the different gas pneumothoraces. Gas volumes were aspirated after 2 h and ECGs were again recorded.
Results: Pneumothorax volumes as low as 20 cc produced consistent ECG changes. The amplitude of the precordial QRS complex was seen to diminish, and this lowering of the QRS amplitude continued as pneumothorax volume increased up to 100 cc. The ECG returned to prepneumothorax patterns with aspiration of the left chest. For different gas pneumothoraces, CO(2) pneumothorax showed almost complete resolution in the 2-h period, whereas He pneumothorax was unchanged.
Conclusions: Precordial ECG changes appear to be a very sensitive indicator of pneumothorax, with very small pneumothorax (<100 cc) consistently being detected by reduction of the QRS complex amplitude. Intraoperative use of precordial ECG leads could result in rapid identification of pneumothorax during laparoscopic surgery. Carbon dioxide pneumothorax shows near 100% resolution in a 2-h period. This supports recommendations of expectant management in asymptomatic patients with CO(2) pneumothorax. However, He pneumothorax does not resolve spontaneously quickly and may require aspiration even in asymptomatic patients.