Two-minute disconnection technique with a double-lumen tube to speed the collapse of the non-ventilated lung for one-lung ventilation in thoracoscopic surgery

This randomized, prospective double-blind study enrolled 50 patients from Jan, 7, 2017 to Feb, 1, 2017. This study was approved by the Institutional Review Board of Shanghai Jiaotong University Shanghai Chest Hospital (KS-2015-32), and the patients provided written informed consent (Chinese Clinical Trial Registry number, ChiCTR-IPR-17010352).

The patients were classified as physical status I or II according to the American Society of Anesthesiologists, ranged in age between 20 and 65 years old and were scheduled to undergo video-assisted thoracoscopic surgery requiring OLV. The exclusion criteria included patients with the following conditions: abnormal expiratory recoil (FEV₁ < 70% of predicted value), chronic obstructive pulmonary disease (COPD) or severe asthma, a history of thoracic surgery, a risk of blood or infected secretions contaminating the dependent lung or NewYork Heart Association (NYHA) heart failure class II to IV and cerebrovascular disease.

The patients received no premedication. When the patients arrived in the operating room, they were monitored by pulse oximetry, electrocardiography (ECG), non-invasive blood pressure (NIBP), bispectral index (BIS) values and bilateral frontal rSO₂ (MNIR-100; Mingxi Medical, Chongqin, China). Using a catheter inserted into a peripheral vein, 6 ml/kg of crystalloid was injected into the patients. Invasive blood pressure monitoring was achieved by cannulating the radial artery after administering lidocaine local anaesthesia. The patients were randomly assigned to groups N and C. After anaesthesia was induced with a target-controlled infusion (TCI) of 2% propofol, at an effect-site concentration (Ce) of 4 μg/ml, 0.6 μg/kg sufentanil, 0.2 mg/kg cisatracurium, and 1 μg/kg dexmedetomidine (DEX) for 10 min, the patients were intubated with a non-operation lateral DLT (size F35 for women and size F37 for men) by experienced thoracic anaesthesiologists involved in the study, and the correct position was confirmed using a fibreoptic bronchoscope (FOB). In the initial two-lung ventilation (TLV) and one-lung ventilation (OLV) period, the tidal volume was 7 ml/kg, the respiratory rate was 12 bpm, and the I/E ratio was 1:2. Anaesthesia was maintained using 0.12 mg/kg/h cisatracurium and 2% propofol Ce at 2–3 μg/ml titrated to maintain BIS between 40 and 50; mean arterial blood pressures (MAPs) and heart rates (HRs) were 20% less than the baseline values. The patient was placed in a lateral decubitus position after right internal jugular central venous catheterization. The correct DLT position was confirmed again using a FOB. In group N, OLV was initiated after the DLT was disconnected for 2 min; the initiation time commenced when the surgeon performed the skin incision. In group C, OLV was initiated when the surgeon started to incise the skin. In both groups, anaesthesia induction and OLV were initiated and maintained using 100% oxygen. The VATS procedure enabled the surgeon to explore the pleura cavity using a 30° video thoracoscopic camera; through a 1.5 cm single skin incision and one to three trocars, the thoracoscopic instruments could move through the lung. After opening the pleura, when the lung was visible, the surgeon started to score the quality of lung collapse using a four-point ordinal scale. Campos et al. and Mourisse et al. [8, 9]^, 1 = extremely poor-no collapse of lung; 2 = poor-partial collapse of lung with interference with surgical exposure; 3 = good-total collapse, but the lung still had some residual air; and 4 = excellent-complete collapse of lung with perfect surgical exposure). At the end of the surgery, after the lung recruitment manoeuvre, the inspiratory pressure increased to 40 cmH₂O for 10 s. Two-lung ventilation was maintained with 50% oxygen and 5 cmH₂O of positive end expiratory pressure (PEEP). When the operation was completed, the patients were discharged to the PACU.

MBP, HR, rSO₂ levels, SpO₂ values, and blood gas analysis outcomes were recorded at the following time points: when inhaling air (T₀), after inhaling 100% oxygen while in the supine position and under double lung ventilation for five mins (T₁), at two mins after the skin incision (T₂), at 10 min after the skin incision (T₃) and after the lung recruitment manoeuvers and inhaling 50% oxygen for five mins (T₄).

The primary outcome was the time needed for complete lung collapse between the two groups. The outcome was measured from the start of the skin incision to the time of total lung collapse and was graded between 3 to 4 according to the video viewed by a surgeon who was blinded to the lung collapse technique. The secondary outcomes were the surgeon’s satisfaction with the surgical conditions using a visual analogue scale (0 = unsatisfied; 10 = very satisfied), the development of hypoxaemia (SpO₂ < 90%) and the need for CPAP during OLV. The same surgeons who were blinded to the lung collapse technique performed all surgical procedures. All of the data were recorded by another anaesthesiologist who was unfamiliar with the lung collapse technique.

The previous study evaluated the degree of lung collapse in which the number of patients per group was 16 and detected global differences among the three groups [6]. The number of patients in each group was determined by a power calculation based on the results of Campos et al. [8] It was calculated that 18 patients were needed per group assuming an α risk of 0.05, a β risk of 0.10 and a mean difference of 50%. Because of the risk of failure with regard to lung adhesion or intubation, we decided to enrol 50 patients in the trial. The data are expressed as the mean ± standard deviation (SD) or as the number of patients. The statistical analyses were performed using a paired Student’s t-test. The categorical variables were performed using the χ²-test. We performed the statistical analyses using SPSS version 21.0 (SPSS Inc. Chicago, IL, USA). A p-value < 0.05 was considered statistically significant.