This is a prospective, single-center, randomized controlled trial designed to evaluate
the effects of recruitment maneuvers and EIT-guided PEEP selection against conventional
ventilation on regional ventilation, gas exchange, and pulmonary mechanics in patients
undergoing abdominal laparoscopic surgery. Adult patients undergoing abdominal
laparoscopic surgery will be enrolled in the study. Patients in the intervention group
will receive intraoperative regular recruitment maneuvers and PEEP titrated using EIT
with a stepwise decremental PEEP trial, while those in the control group will have a
constant PEEP of 5 cmH2O. The primary outcomes are regional ventilation, blood
oxygenation, and pulmonary mechanics. Secondary outcomes include hemodynamic effects,
pneumothorax or barotrauma events during the intraoperative period, pulmonary
complications during the first 5 days postoperative, and length of hospital stay.
Standard Ventilation Management:
Patients in both groups receive volume-controlled ventilation at the lowest possible
inspired oxygen fraction (FiO2), with a minimum of 0.4, to maintain peripheral oxygen
saturation (SpO2) above 92%. The inspiratory to expiratory ratio (I:E) is set at 1:2, and
the respiratory rate is adjusted to achieve normocapnia, defined as an end-tidal carbon
dioxide partial pressure between 35 and 45 mmHg. Tidal volume (VT) is set at 7 ml/kg
predicted body weight (PBW), calculated using the following formula: for males, 50 + 0.91
× (height in centimeters - 152.4), and for females, 45.5 + 0.91 × (height in centimeters
Intervention Patients were randomized into either the intervention group or the control
group.
Intervention Group: The individualized high PEEP with RMs group will commence with a PEEP
of 5 cm H2O and will undergo an RM followed by a decremental PEEP trial. RMs are
conducted only when hemodynamic stability is confirmed by the attending anesthesiologist.
For this process, the ventilator is set to pressure-controlled ventilation mode, with a
respiratory rate of 16 breaths per minute and ΔP=15 (ΔP is calculated by subtracting PEEP
from the plateau pressure (Pplat)). In intervals of 5 breaths, PEEP is incrementally
increased by 5 cm H2O, starting at 5 cm H2O and reaching up to 20 cm H2O. The decremental
PEEP trial is immediately performed following the first RM, beginning at a PEEP of 20 cm
H2O with a respiratory rate of 15 breaths per minute while maintaining the ventilator in
pressure-controlled ventilation mode. Every 30 seconds, PEEP is decreased by increments
of 2 cm H2O until it reaches a minimum of 6 cm H2O. This decremental PEEP trial is
succeeded by a second RM, after which the individualized PEEP level will be established
as determined by the decremental PEEP trial and sustained until the completion of
ventilation.
Control Group: Patients will receive a constant PEEP of 5 cm H2O without RMs throughout
the entire intraoperative ventilation period.
Rescue strategies Desaturation (defined as SpO2 ≤ 90% or if preoperative SpO2 < 90% an
absolute decrease in SpO2 > 5%) If desaturations occur and there are no airway problems,
severe hemodynamic impairment or ventilator malfunction, a rescue strategy is allowed by
increasing FiO2 first, eventually followed by RM and PEEP increases.
Preapproved protocol deviations
If one of the following complications occurs and does not respond to conventional
therapy, PEEP can be changed, according to the judgment of the anesthesiologist in
charge:
(i) After PEEP titration, a mean arterial pressure (MAP) < 65 mmHg, lasting > 1 min and
not responding to fluids and/or vasoactive drugs.
(ii) New arrhythmias not responding to the treatment suggested by the Advanced Cardiac
Life Support guidelines.
(iii) Need for a dosage of vasoactive drugs at the highest level tolerated, according to
the decision of the anesthesiologist in charge.
(iv) Need of massive transfusion, more than five units of blood to maintain hematocrit >
21% and hemoglobin> 7 mg/dL.
(v) Surgical complication resulting in a life-threatening situation. Any deviation from
the protocol, excluding those mentioned above, is classified as a protocol violation.
Protocol violations are to be reported and will be discussed with the data safety
monitoring board.