Driving Pressure in Neurosurgery
Condition: Neurosurgery
Study type: Interventional

Summary: 
      The effect of driving pressure (DP)-guided positive end expiratory pressure (PEEP) on early
      postoperative pulmonary ventilation is to be determined for patients undergoing neurosurgery.
      Patients are recruited to receive volume controlled ventilation with either a fixed PEEP
      (5cmH2O) or DP titrated PEEP. Early postoperative regional distribution of lung ventilation,
      expressed as global inhomogeneity (GI) is evaluated by electrical impedance tomography (EIT),
      a noninvasive, radiation free modality. Center of ventilation (COV) by EIT, as well as the
      lung ultrasonography（LUS), perioperative ventilatory parameters, arterial oxygenation index
      (PaO2/FiO2) , serum indicators and postoperative pulmonary complications are secondary
      outcome variables.
    

Detailed description: 
      After screened for preoperative risk factors, 44 patients undergoing elective neurosurgery
      and planned to be extubated in the operating room are randomly assigned to two groups: (1)
      PEEP = 5cmH2O; (2) driving pressure (DP)-guided PEEP. The ventilation protocol consists of
      volume-controlled mechanical ventilation (Datex Ohmeda S/5 Advance; General Electric Company
      Healthcare, Helsinki, Finland) at a tidal volume (VT) of 8 ml/kg predicted body weight (PBW),
      fresh gas of 2 litre /min, inspiratory to expiratory ratio of 1:2, and a respiratory rate
      adjusted to normocapnia (arterial carbon dioxide partial pressure between 35 and 45 mmHg).
      For group 2, trial for the lowest DP was started 10 min after position adjustment by
      increasing PEEP from 2 to 10 cm H2O incrementally. DP was calculated as "plateau pressure -
      PEEP". Each PEEP level was maintained for 10 respiratory cycles, with DP in the last cycle
      recorded. Then the PEEP level producing the lowest DP was identified and maintained
      intraoperatively. A plateau pressure of no more than 30 cmH2O is targeted in each group.
      Early postoperative distribution of regional ventilation global inhomogeneity (GI) is the
      primary endpoint evaluated by EIT (electrical impedance tomography), which was performed by a
      trained technician who is blinded to randomization. Center of ventilation (COV) by EIT, lung
      ultrasonography（LUS) , and arterial blood gas are evaluated, with inflammatory and oxidative
      mediators tested from venous sample. Brain relaxation will be scored by the neurosurgeon.
      Postoperative pulmonary complications within 3 days are also recorded.
    

Intervention name(s): PEEP
Intervention type(s): Procedure
Intervention description(s): Driving pressure (DP) is calculated as "plateau pressure - PEEP". 10min after position adjustment, PEEP is increased from 2 to 10 cm H2O incrementally. Each PEEP level is maintained for 10 respiratory cycles, with DP in the last cycle recorded. Then the PEEP level producing the lowest DP will be identified and maintained intraoperatively.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Prevention