Airway pressure changes during one-lung ventilation.

This investigation analyzed the changes in inspiratory airway pressures during transition from two-lung to one-lung ventilation in patients tracheally intubated with a double-lumen endotracheal tube (DLT) using a classical method of intubation without fiberoptic bronchoscopy. All patients were anesthetized in a standardized fashion. Ventilation was accomplished with the Siemens 900 constant-flow mechanical ventilator (Solna, Sweden). Peak (Ppeak) and plateau (Pplateau) inspiratory airway pressures were recorded with an on-line respiratory monitor before and after clamping the tracheal limb of the DLT. The position of the DLTs was evaluated by fiberoptic bronchoscopy with the patient in supine position. Of the 51 intubations, the DLT was malpositioned in 15 cases (29.5%). Ppeak and Pplateau increased significantly when switched from two-lung ventilation to one-lung ventilation in both correctly and incorrectly positioned DLTs. When the DLT was in a correct position, Ppeak increased by a mean of 55.1% and Pplateau increased by a mean of 41.9%. When the DLT was malpositioned, this increase was significantly larger (74.9% and 68.8%, respectively). Three tests commonly used as markers of malpositioned DLTs were evaluated based on the data of this study, and it was established that, although the pressure differences related to position are statistically significant, as a single value, they cannot be used for clinical decision making.

Intrinsic positive end-expiratory pressure during one-lung ventilation for thoracic surgery. The influence of preoperative pulmonary function.

OBJECTIVE: To detect and to quantify intrinsic positive end-expiratory pressure (PEEPi) during thoracic surgery in the dependent lung of patients intubated with a double-lumen endotracheal tube (DLT) in the lateral position. METHODS: Twenty consecutive patients undergoing elective pulmonary resection were anesthetized, paralyzed, and intubated with a DLT. Their lungs were ventilated (Siemens Servo 900 C ventilator; Siemens Elevna; Solna, Sweden) with constant inspiratory flow. Fraction of inspired oxygen, tidal volume (10 mL/kg), frequency (10/min), and inspiratory time/total time (0.33) were kept constant during the study. PEEPi and ventilatory data were measured in the dependent lung in the supine then in the lateral position with a closed hemithorax. The obtained data were analyzed according to the presence (group PH) or absence (group N) of pulmonary hyperinflation determined from the preoperative pulmonary function data as higher than 120% of predicted value of functional residual capacity (FRC) and residual volume (RV). DATA ANALYSIS: In the dependent lung of patients in group PH (n = 11), PEEPi was present in the supine (n = 8) and in the lateral (n = 11) positions in the range of 1 to 10 cm H2O. In group N (n = 9), PEEPi was detected in one patient and only in the supine position. In the whole group of 20 patients, the preoperative value of FRC (% predicted) and RV (% predicted) was statistically significantly correlated to the presence of PEEPi, whereas the preoperative FEV1 (% predicted) was poorly related to PEEPi in both positions. There was no significant correlation between the value of PaCO2 and PEEPi during one-lung ventilation (OLV) but patients in group PH had a significantly higher PaCO2 during OLV than group N (p = 0.012). CONCLUSIONS: In patients with chronic obstructive lung disease and pulmonary hyperinflation, PEEPi occurs commonly during the period of OLV and only occasionally in patients with normal lungs. As the ventilatory pattern, the size of DLT, and the side of surgery were similar in the two groups of patients, we conclude that the occurrence of PEEPi in our patients was influenced mainly by the preexisting pulmonary hyperinflation and airflow obstruction.