Objective

The ideal chest drain suction pressure (intra-pleural pressure) in thoracic surgery is unknown. We examine the effect of different intra-pleural pressures following common thoracic surgery procedures on respiratory physiology.

Methods

Chest wall motion analysis technology (Optoelectronic plethysmography (OEP)) was used to measure chest wall mechanics of 13 patients (8 had lung resection, 4 COPD patients, 2 had Pleurectomy bullectomy, 2 had secondary phumothorax and 4 with air leak) They were subjected to 10 minutes of Intra pleural pressures of -0.8 (gravity), -2 and -5 kPa (via electronic chest drains) and changes in chest wall volumes were measured. Data was collected during quiet breathing.

Results

With exception of secondary pneumothorax, all patients had 81 +/- 11 mls and 97 +/- 17 mls reduction in overall chest wall tidal volume when subjected to -2 and -5 kPa of drain suction respectively, compared to gravity mode (figure 1) (p <0.05). This was mirrored by a reduction in minute ventilation. Furthermore, the amount of air leak correlated positively with the degree of suction (Air leak increased by 185 +/- 172 ml during -2 kPa of suction compared to gravity mode (p <0.05)).

Conclusion

This is the first published data to show the physiological advantage of gravity mode over higher grades of suction on chest wall mechanics, and the positive correlation between the degree of suction and amount of air leak.