Low-Intensity Mechanical Ventilation in the Operating Room: a Pilot Study (VIOLET)

The aim of the study is to assess whether a bundle of protective low-intensity mechanical ventilation interventions reduces perioperative atelectasis and postoperative pulmonary complications, compared with standard care in a robot-assisted surgical setting. The feasibility of this ventilation bundle will also be assessed.

Study Overview

• Status: Enrolling by invitation
• Conditions: Robotic Surgery; Post Operative Pulmonary Complications
• Intervention / Treatment: Device: Low Intensity Mechanical Ventilation

Detailed Description

The investigators hypothesize that protective low-intensity mechanical ventilation during robot-assisted surgery reduces perioperative atelectasis and postoperative pulmonary complications.

• Study Type: Interventional
• Enrollment (Estimated): 60
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02115
      • Beth Israel Deaconess Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Adult patients undergoing elective intra-abdominal or pelvic robot-assisted surgery with a planned duration of at least 2 hours, under general anesthesia with planned extubation at the end of the procedure

Exclusion Criteria:

• Known pregnancy
• Pre-existing intubation or tracheostomy
• Contraindications for esophageal manometry: severe midface trauma or recent nasal surgery, esophageal varices, recent gastric or esophageal surgery
• Contraindications for electrical impedance tomography (EIT): inability to place EIT belt, presence of an active electronic implantable device (e.g., pacemaker, ICD)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
No Intervention: Control; A guided standard of care protocol will be applied in the control group. This includes a PEEP of 5 cmH₂O, with adjustment by the anesthesia provider if SpO₂ falls below 96% or whenever deemed clinically necessary, a tidal volume of 6-10 mL/kg predicted body weight, and a respiratory rate adjusted to maintain end-tidal CO₂ between 35 and 45 mmHg throughout anesthesia. FiO₂ will be set to 100% during the washout phase at the end of surgery to limit resorption atelectasis.
Experimental: Intervention; A bundle of protective low-intensity mechanical ventilation strategies will be applied throughout the procedure. All interventions consist of modification of ventilator settings.	Device: Low Intensity Mechanical Ventilation; A bundle of protective low-intensity mechanical ventilation strategies will be applied throughout the procedure: Recruitment maneuver; Tidal volume set to 8 ml/kg predicted body weight (PBW) and stepwise adjustment to achieve a driving pressure (Plateau pressure - PEEP) < 13 cmH2O with a minimum tidal volume of 5ml/kg PBW; Respiratory rate adjustment to maintain a target end-tidal carbon dioxide concentration (etCO₂) between 45 and 55 mmHg.; Reassessment and adaptation after Trendelenburg positioning and pneumoperitoneum.; Re-adjustment of Tidal Volume and PEEP ventilator settings to (2.) after exsufflation and return to the supine position. FiO₂ set to 70% during the washout phase of the inhalational anesthetic until extubation.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
ΔEELV between baseline and after extubation before leaving the operating room.	Change in end-expiratory lung volume (EELV), measured using electrical impedance tomography between baseline and after extubation before leaving the operating room.	Perioperative Day 0: From pre-intubation baseline in the operating room (prior to induction of anesthesia) to the first post-extubation EIT assessment (within 10 min after extubation on Day 0).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Proportion of patients with postoperative pulmonary complications at day 7	Re-intubation, emergency non-invasive ventilation or pneumonia	This secondary outcome will be assessed in the time between day of surgery until 7 days after the day of surgery
Change in right-ventricular systolic function (TAPSE, mm) from pre-intubation baseline to first post-extubation echocardiogram	Right-ventricular systolic function will be assessed by transthoracic echocardiography using tricuspid annular plane systolic excursion (TAPSE, measured in millimeters). TAPSE will be recorded at pre-intubation baseline and at the first postoperative transthoracic echocardiographic examination after extubation. The primary outcome for this measure will be the change in TAPSE (post-extubation minus baseline, mm).	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, just before extubation
Change in right-ventricular fractional area change (RV-FAC, %) from pre-intubation baseline to first post-extubation echocardiogram	Right-ventricular systolic function will be assessed by transthoracic echocardiography using right-ventricular fractional area change (RV-FAC, expressed as percentage). RV-FAC will be recorded at pre-intubation baseline and at the first postoperative transthoracic echocardiographic examination after extubation. The outcome for this measure will be the change in RV-FAC (post-extubation minus baseline, %).	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, just before extubation
Change in left ventricular ejection fraction (LVEF, %) from pre-intubation baseline to first post-extubation echocardiogram	Left ventricular systolic function will be assessed by transthoracic echocardiography using left ventricular ejection fraction (LVEF, expressed as percentage). LVEF will be recorded at pre-intubation baseline and at the first postoperative transthoracic echocardiographic examination after extubation. The outcome for this measure will be the change in LVEF (post-extubation minus baseline, %).	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, just before extubation
Change in estimated pulmonary artery systolic pressure (PASP, mmHg) from pre-intubation baseline to first post-extubation echocardiogram	Pulmonary hemodynamics will be assessed by transthoracic echocardiography using estimated pulmonary artery systolic pressure (PASP, measured in millimeters of mercury). PASP will be recorded at pre-intubation baseline and at the first postoperative transthoracic echocardiographic examination after extubation. The outcome for this measure will be the change in PASP (post-extubation minus baseline, mmHg)	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, just before extubation
Recruitment rate	Proportion of patients enrolled in the study-defined as those who provided acceptance and signed informed consent-relative to all patients approached.	Day 0
Intervention deliverability	proportion of patients in the intervention arm in whom the full bundle of protective low-intensity ventilation strategies is delivered as planned across all predefined intraoperative phases.	From intubation to extubation at Day 0
EELV	End-expiratory lung volume measured by Electrical Impedance Tomography in mL	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, after insufflation and positioning, after PEEP/TV/RR reassessment, just before extubation, after extubation, after PACU admission and 60min after PACU admission
COV	Center of ventilation measured by Electrical Impedance Tomography in percentage	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, after insufflation and positioning, after PEEP/TV/RR reassessment, just before extubation, after extubation, after PACU admission and 60min after PACU admission
RVDI	Regional ventilation delay inhomogeneity measured by Electrical Impedance Tomography (unitless)	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, after insufflation and positioning, after PEEP/TV/RR reassessment, just before extubation, after extubation, after PACU admission and 60min after PACU admission
GI	Global inhomogeneity index measured by Electrical Impedance Tomography (unitless)	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, after insufflation and positioning, after PEEP/TV/RR reassessment, just before extubation, after extubation, after PACU admission and 60min after PACU admission
Dorsal ROI	Maximum dorsal ratio of impedance measured by Electrical Impedance Tomography (unitless)	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, after insufflation and positioning, after PEEP/TV/RR reassessment, just before extubation, after extubation, after PACU admission and 60min after PACU admission
EEPL	End-expiratory transpulmonary pressure, calculated as airway pressure minus esophageal pressure (cmH₂O)	Perioperative Day 0: after intubation, after PEEP/TV/RR titration, after insufflation and positioning, after PEEP/TV/RR reassessment, just before extubation
EIPL	End-inspiratory transpulmonary pressure, calculated as airway pressure minus esophageal pressure (cmH₂O)	Perioperative Day 0: after intubation, after PEEP/TV/RR titration, after insufflation and positioning, after PEEP/TV/RR reassessment, just before extubation
Relationship between body mass index with optimal PEEP	Correlation between BMI (kg/m²) and the optimal positive end-expiratory pressure (PEEP, cmH₂O) determined after pneumoperitoneum insufflation and patient positioning for surgery.	Intraoperative Day 0: after insufflation of pneumoperitoneum and positioning the patient for surgery
Relationship of the degree of Trendelenburg inclination with optimal PEEP	Correlation between the degree of Trendelenburg inclination (in degree) and the optimal positive end-expiratory pressure (PEEP, cmH₂O) determined after pneumoperitoneum insufflation and patient positioning for surgery.	Intraoperative Day 0: after insufflation of pneumoperitoneum and positioning the patient for surgery
Relationship of the pneumoperitoneum (insufflation) with optimal PEEP	Correlation between the pneumoperitoneum (insufflation in cmH2O) and the optimal positive end-expiratory pressure (PEEP, cmH₂O) determined after pneumoperitoneum insufflation and patient positioning for surgery.	Intraoperative Day 0: after insufflation of pneumoperitoneum and positioning the patient for surgery
Intraoperative oxygenation	Intraoperative peripheral pulsed oxygen saturation (SpO2)	Perioperative Day 0: before anesthesia, after intubation, after PEEP/TV/RR titration, after insufflation and positioning, after PEEP/TV/RR reassessment, just before extubation, after extubation
Postoperative oxygenation	Postoperative peripheral pulsed oxygen saturation (SpO2)	Postoperative Day 0: after PACU admission and 60min after PACU admission

Collaborators and Investigators

• Sponsor: Beth Israel Deaconess Medical Center

Publications and helpful links

General Publications

• Schaefer MS, Wania V, Bastin B, Schmalz U, Kienbaum P, Beiderlinden M, Treschan TA. Electrical impedance tomography during major open upper abdominal surgery: a pilot-study. BMC Anesthesiol. 2014 Jul 5;14:51. doi: 10.1186/1471-2253-14-51. eCollection 2014.
• Schaefer MS, Treschan TA, Gauch J, Neukirchen M, Kienbaum P. Influence of xenon on pulmonary mechanics and lung aeration in patients with healthy lungs. Br J Anaesth. 2018 Jun;120(6):1394-1400. doi: 10.1016/j.bja.2018.02.064. Epub 2018 Apr 13.

Study record dates

Study Major Dates

• Study Start (Actual): April 2, 2026
• Primary Completion (Estimated): October 31, 2026
• Study Completion (Estimated): March 31, 2027

Study Registration Dates

• First Submitted: November 20, 2025
• First Submitted That Met QC Criteria: December 2, 2025
• First Posted (Actual): December 11, 2025

Study Record Updates

• Last Update Posted (Actual): April 8, 2026
• Last Update Submitted That Met QC Criteria: April 2, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Lung protective ventilation; Electric Impedance Tomography (EIT)
• Other Study ID Numbers: 2025P000986

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: No