Changes of pleural pressure after thoracic surgery

Background: The negative pressure of the pleural cavity is critical to maintain lung expansion. However, the actual values of pleural pressure according to the phase of respiration after various types of pulmonary resection have not been well reported. The aim of this study was to measure the pleural pressure directly and to compare the results according to the extent of pulmonary resection. Methods: We manufactured a high-resolution digital manometer with which pleural pressure can be measured directly. A total of 43 patients who underwent thoracic surgery (lobectomy in 23, minimal resections in 20) were enrolled. The maximum, minimum, and mean pleural pressure was recorded during normal quiet breathing, forced breathing, and coughing, separately. Results: During normal quiet breathing, the average values of pleural pressure at end inspiration, end expiration, and the mean pleural pressure were −17.7, −7.0 and −11.2 cmH 2 O in lobectomy group, and −14.3, −4.6, −8.3 cmH 2 O in the minimal/no-resection group, respectively. The mean pleural pressure was significantly lower in lobectomy group compared to the minimal/no-resection group (P=0.026). During forced respiration, the same values were −44.0, −4.2 and −18.9 cmH 2 O in the lobectomy group, and −29.8, −0.1 and −12.7 cmH 2 O in the minimal/no-resection group. All of the pleural pressure values in lobectomy group were significantly lower compared to minimal/no-resection group (P=0.029, P=0.015, P=0.019, respectively). The maximal pressures during coughing were not statistically different between the two groups (38.4 vs . 34.4 cmH 2 O, P=0.687). Conclusions: We reported the actual pleural pressure changes according to the phase of respiration and type of surgery using a digital manometer. In lobectomy patients, the pleural pressure was highly negative compared to the minimal/no-resection group, especially during deep inspiration.