Optimum frequency for lung recruitment during surgery in patients undergoing one-lung ventilation

Objective To investigate the optimum frequency for lung recruitment during surgery in the patients undergoing one-lung ventilation(OLV). Methods Eighty patients of both sexes, aged 48-64 yr, weighing 55-80 kg, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, were randomly divided into lung recruitment with different frequency groups(LR1-4 groups, n=20 each)using a random number table.The patients were mechanically ventilated(tidal volume 6 ml/kg, respiratory rate 12-16 breaths/min, positive end-expiratory pressure 5 cmH2O, and peak airway pressure<35 cmH2O during OLV)and the end-tidal pressure of carbon dioxide was maintained at 35-45 mmHg.Lung recruitment was performed once every 30, 60 and 120 min in LR1-3 groups, respectively, and lung recruitment was performed only once before the chest was closed in group LR4.At 5 min after restoration of two-lung ventilation, the airway pressure was maintained at 40 cmH2O for 15 s. After admission to the operating room(T0), immediately after onset of OLV(T1), at 30 min, 1 h, 2 h and 3 h of OLV(T2-5), at the end of OLV(T6), at 30 min after restoration of two-lung ventilation(T7), and at 30 min after tracheal intubation(T8), blood samples were collected from the radial artery for blood gas analysis, and oxygenation index(OI)and intrapulmonary shunt(Qs/Qt)were calculated.At T0, T4, T7 and 2 h and 24 h after operation(T9, 10), blood samples were collected from the internal jugular vein for determination of serum interleukin-6(IL-6), tumor necrosis factor-alpha(TNF-α)and IL-10 concentrations by enzyme-linked immunosorbent assay. Results Compared with group LR1, the OI was significantly increased, and Qs/Qt was significantly decreased at T6 in LR2 and LR4 groups(P 0.05). There was no significant difference in OI and Qs/Qt at each time point between group LR2 and group LR4(P>0.05). Compared with group LR1, the serum IL-6, TNF-α and IL-10 concentrations were significantly decreased at T4-10 in LR2 and LR3 groups and at T4 in group LR4(P 0.05). Conclusion The optimum frequency for lung recruitment during OLV is 1 time per 60 min in the patients undergoing thoracic surgery. Key words: Positive-pressure respiration; Respiratory function tests; Respiration, artificial