Abstract
BACKGROUND: To examine the influence of positive end-expiratory pressure (PEEP) settings on lung mechanics and oxygenation in elderly patients undergoing thoracoscopic surgery. METHODS: One hundred patients aged >65 years were randomly allocated into either the PEEP(5) or the electrical impedance tomography (EIT) group (PEEP(EIT)). Each group underwent volume-controlled ventilation (tidal volume 6 mL/kg predicted body weight) with the PEEP either fixed at 5 cmH(2)O or set at an individualized EIT setting. The primary endpoint was the ratio of the arterial oxygen partial pressure to the fractional inspired oxygen (PaO(2)/FiO(2)). The secondary endpoints included the driving pressure, and dynamic respiratory system compliance (C(dyn)). Other outcomes, such as the mean airway pressure (P(mean)), mean arterial pressure (MAP), lung complications and the length of hospital stay were explored. RESULTS: The optimal PEEP set by EIT was significantly higher (range from 9-13 cmH(2)O) than the fixed PEEP. PaO(2)/FiO(2) was 47 mmHg higher (95% CI: 7-86 mmHg; P=0.021), C(dyn) was 4.3 mL/cmH(2)O higher (95% CI: 2.1-6.7 cmH(2)O; P<0.001), and the driving pressure was 3.7 cmH(2)O lower (95% CI: 2.2-5.1 mmH(2)O; P<0.001) at 0.5 h during one-lung ventilation (OLV) in the PEEP(EIT) group than in the PEEP(5) group. At 1 h during OLV, PaO(2)/FiO(2) was 93 mmHg higher (95% CI: 58-128 mmHg; P<0.001), C(dyn) was 4.4 mL/cmH(2)O higher (95% CI: 1.9-6.9 mL/cmH(2)O; P=0.001), and the driving pressure was 4.9 cmH(2)O lower (95% CI: 3.8-6.1 cmH(2)O; P<0.001) in the PEEP(EIT) group than in the PEEP(5) group. PaO(2)/FiO(2) was 107 mmHg higher (95% CI: 56-158 mmHg; P<0.001) in the PEEP(EIT) group than in the PEEP(5) group during double-lung ventilation at the end of surgery. CONCLUSIONS: PEEP values determined with EIT effectively improved oxygenation and lung mechanics during one lung ventilation in elderly patients undergoing thoracoscopic surgery.