Influence of Inspiratory Pause on Ventilatory Efficiency in Robotic Surgery. A Prospective Paired Study.

Summary

The investigators aim to determine if the modification of the end inspiratory pause (EIP) during mechanical ventilation adds benefit when applied to patients undergoing robotic surgery and who are ventilated under an individualized open lung approach (iOLA) strategy. The EIP is an adjustable parameter of volume controlled ventilation modes usually set as a percentage of the total inspiratory time. It represents the phase comprised between the moment in which the volume programmed in the ventilator has already been administered (which marks the end of the inspiratory flow), and the opening of the expiratory valve (which marks the beginning of expiration).

The investigators will study whether modifications of the EIP produce variations in the "quantity" of the lung that participates in gas exchange (respiratory volume). To do so, the investigators will sequentially apply different EIP to participants (paired study). The investigators´ hypothesis is that increasing the EIP up to a level, may diminish the lung volume that does not participate in breathing (the physiological dead space- VDphys), thereby increasing the respiratory volume. To note: the VDphys includes the "conduction" volume, that represented by trachea, bronchi, et cetera, which is in charge of driving the "air" towards the respiratory zones, and the alveolar dead space (those zones of the respiratory volume that due to different reasons do not directly participate in gas exchange: alveoli ventilated but not perfused, areas of overdistension, etc. The investigators will measure dead volumes by mean of specific non-invasive monitoring (volumetric capnography) coupled to the anesthesia workstation, and the mechanics of lung and the distribution of the gas within it by means of electric impedance tomography, a non-invasive technique showing continuous images of patient's lung. The estimation of the respiratory volume will help the investigators to more precisely adjust the amount of oxygen and anesthetic gases that must be administered in function of patients´ gases consumption, a calculated parameter that is function of the respiratory volume and that will also be tested during the study. The investigators will also accurately measure patient oxygenation by means of arterial blood samples extracted from a radial artery catheter. Apart from sequential modifications in the EIP, the ventilation strategy applied to patients will be that used in the investigators´ usual practice (described below).

Conditions

• Mechanical Ventilation
• Positive End-Expiratory Pressure
• Anesthesia

Interventions

PROCEDURE

Modifying EIP under a tOLA before pneumoperitoneum

Phase 1: Moment (M) 1) Standard PPV and an initial EIP of 10% M 2) ARM with titration of optimal PEEP (PEEPop) on a decremental PEEP trial, followed by a new ARM and setting a tailored open-lung PEEP (tOL-PEEP), that 2 cm H2O higher than PEEPop M 3) Incremental modification of the EIP in steps of 10% (from 10 to 40%)

PROCEDURE

Modifying EIP under a tOLA with pneumoperitoneum

Phase 2: M 4) The investigators will apply the EIP that guarantees the lowest Pdriv M 5) After applying pneumoperitoneum and trendelenburg M 6) Atelectasis test (see below) M 7) M 7a) In case of atelectasis test = negative: the investigators will modify the EIP in incremental or decremental steps of 10% M 7b) In case of atelectasis test=positive: ARM M 8) In those cases recruited (M 7b), modify the EIP (as in M 7a) Once the EIP that guarantees the best ventilation conditions has been stablished based on the lowest Pdriv (and higher Crs), the investigators will maintain these conditions until the end of surgery, with periodic evaluation of the pulmonary collapse by means of the atelectasis test (see below) performed every 40 minutes or regardless of time if an oxygen saturation by pulse oximetry (SpO2) \< 97% is detected.

PROCEDURE

Atelectasis test

It is performed during mechanical ventilation, due to suspicion of alveolar collapse. Alveolar collapse will be suspected on observation of a reduction in Crs \> 10% over post-recruitment values. In these cases the atelectasis test will be performed, consisting of a reduction in FiO2 to 0.21, maintaining this FiO2 for 5 minutes. If lung collapse is \>10%, a fall in SpO2 below 97% will be expected (positive atelectasis test), in which case, an ARM and a PEEPop titration test will be performed.

Sponsors & Collaborators

• Fundación Pública Andaluza para la gestión de la Investigación en Sevilla

  lead OTHER

Principal Investigators

• Manuel de la Matta, MD · Hospitales Universitarios Virgen del Rocío

Study Design

Allocation

NA

Purpose

TREATMENT

Masking

NONE

Model

SINGLE_GROUP

Eligibility

Min Age

18 Years

Max Age

99 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2023-02-01

Primary Completion

2023-05-30

Completion

2023-11-30

Countries

• Spain

Study Locations