Comparative Study of the Non-dependent Continuous Positive Pressure Ventilation and High Frequency Positive Pressure Ventilation During One-lung Ventilation for Thoracoscopy

Thirty patients aged 18-60 years (ASA physical status II-III) scheduled for elective video-assisted thoracoscopic surgery with at least one hour of one-lung ventilation (OLV) will be included in this randomized prospective placebo-controlled crossover study at the authors' center after obtaining approval of the institutional ethical committee and informed written consent. The patients will be randomized to a CPCP2-HFPPV group(n = 15)or a HFPPV-CPAP2 group(n = 15).

A power analysis of the data obtained from our preliminary pilot study indicated that 26 patients will be sufficient to detect a one SD changes in the visual analog scale assessment of the surgical field, with a type-I error of 0.05 and a power of 85%, with added 10% more patients, for a final sample size of 30 patients to account for patients dropping out during the study. All operations will be performed by the same surgeons.

The patients will be premedicated with fentanyl (1.0 μg/Kg) and i.v. midazolam (0.03 mg/Kg). All patients will be monitored with five leads electrocardiography, pulse oximetry, and non-invasive blood pressure and 7mL/Kg of 6% Hydroxyethyl Starch 130/0.4 (Voluven, Fresenius Kabi, Bad Homburg, Germany) will be given intravenously before induction of general anesthesia. An arterial line (20 G) will be inserted under local anesthesia. A thoracic epidural catheter (T4-T7) will be inserted with the patient in sitting position, and a test dose (1.5% lidocaine 3 mL plus epinephrine 1:200.000) will be administered in order to exclude an intravascular or intrathecal position of the catheter. No more epidural local anesthetics will be used during the study in order to avoid effects on hypoxic pulmonary vasoconstriction.

Anesthesiologists who gave the anesthetic will not be involved in the collection of the patient's data. General anesthesia will be induced with propofol (2-3 mg/kg), fentanyl (2-3 µg/kg), and cisatracurium (0.2 mg/kg) was given for muscle relaxation.

The trachea will be intubated with a left-sided double-lumen tube (DLT) [Broncho-Cath®; Mallinckrodt Medical Ltd., Dublin, Ireland]. The correct position of the tube will be confirmed with a fiberoptic bronchoscope after intubation and after positioning the patient in the lateral decubitus position. Other patient monitoring included end-tidal CO2, neuromuscular blockade, and nasopharyngeal temperature will be used. Anesthesia will be maintained with continuous infusions of propofol (6-8 mg/kg/h) and fentanyl (1 µg/kg/h). Increments of cisatracurium (0.03 mg/kg) will be given to maintain suppression of the second twitch using a train-of-four stimulation.