PEEP guided by electrical impedance tomography during one-lung ventilation in elderly patients undergoing thoracoscopic surgery

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 PEEP5 or the electrical impedance tomography (EIT) group (PEEPEIT). Each group underwent volume-controlled ventilation (tidal volume 6 mL/kg predicted body weight) with the PEEP either fixed at 5 cmH2O or set at an individualized EIT setting. The primary endpoint was the ratio of the arterial oxygen partial pressure to the fractional inspired oxygen (PaO2/FiO2). The secondary endpoints included the driving pressure, and dynamic respiratory system compliance (Cdyn). Other outcomes, such as the mean airway pressure (Pmean), 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 cmH2O) than the fixed PEEP. PaO2/FiO2 was 47 mmHg higher (95% CI: 7-86 mmHg; P=0.021), Cdyn was 4.3 mL/cmH2O higher (95% CI: 2.1-6.7 cmH2O; P<0.001), and the driving pressure was 3.7 cmH2O lower (95% CI: 2.2-5.1 mmH2O; P<0.001) at 0.5 h during one-lung ventilation (OLV) in the PEEPEIT group than in the PEEP5 group. At 1 h during OLV, PaO2/FiO2 was 93 mmHg higher (95% CI: 58-128 mmHg; P<0.001), Cdyn was 4.4 mL/cmH2O higher (95% CI: 1.9-6.9 mL/cmH2O; P=0.001), and the driving pressure was 4.9 cmH2O lower (95% CI: 3.8-6.1 cmH2O; P<0.001) in the PEEPEIT group than in the PEEP5 group. PaO2/FiO2 was 107 mmHg higher (95% CI: 56-158 mmHg; P<0.001) in the PEEPEIT group than in the PEEP5 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.

Keywords: Elderly patients; electrical impedance tomography (EIT); lung-protective ventilation; one-lung ventilation; positive end-expiratory pressure level.

Conflict of interest statement

Conflicts of Interest: Zhanqi Zhao receives a consulting fee from Dräger Medical. Inéz Frerichs receives funding from the European Union’s 7th Framework Programme for Research and Technological Development (WELCOME, Grant No. 611223) and the European Union’s Framework Programme for Research and Innovation Horizon2020 (CRADL, Grant No. 668259, WELMO, Grant 825572) and reimbursements for speaking fees, conference costs and travel costs from Dräger Medical. The other authors have no conflicts of interest to disclose.

2019 Annals of Translational Medicine. All rights reserved.

Figures

Figure 1

Individual PEEP titration method using lung electrical impedance tomography (EIT). (A) Mean tidal volume image of one-lung ventilation. Pixel values are relative impedances reported in arbitrary units. (B) Decremental PEEP trial from 15 to 1 cmH2O with increments of 2 cmH2O and a duration of one minute at each level. (C) The intercept point of the cumulated collapse and overdistension percentage curves (black arrow) is the optimal PEEP.

Figure 2

Workflow of the thoracoscopic surgery protocol applied in aged patients from both groups. Ppeak, peak pressure; SpO2, peripheral capillary oxygen saturation; PEEPind, electrical impedance tomography-based individualized PEEP; PEEP5, a fixed PEEP of 5 cmH2O PEEP; PBW, predicted body weight; DLV, two-lung ventilation; OLV, one-lung ventilation; VCV, volume-controlled ventilation; VT, tidal volume; RR, respiratory rate; I:E, inspiration to expiration time.

Figure 3

Comparison of PaO2/FiO2 (A), driving pressure (B) and pulmonary dynamic compliance (C) between the two study groups at different time points. PaO2, partial pressure of oxygen in arterial blood; FiO2, fraction of inspired oxygen; ΔP, driving pressure; Cdyn, pulmonary dynamic compliance; DLV, double-lung ventilation; OLV, one-lung ventilation; PEEP, positive end-expiratory pressure; PEEPind, individual PEEP determined with EIT; *, significant difference compared to the control group, P<0.05.