Noisy Pressure Support Ventilation (noisy-PSV) would lead to improved lung function, while preserving respiratory muscle unloading. Basically, noisy PSV differs from other assisted mechanical ventilation modes that may also increase the variability of the respiratory pattern (e.g. proportional assist ventilation) by the fact that the variability does not depend on changes in the patient's inspiratory efforts. The aim of this study is to evaluate the optimal variability for noisy PSV in patients with ALI based on its effects on respiratory mechanics, breathing comfort, gas exchange, and hemodynamics. The investigators hypothesize that noise in pressure support leads to variations in VT that are able to improve lung function and that physiologic variables respond differently to the degree of variability in pressure support
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
20
Noisy-PSV 1: different levels of variable pressure support (PS) will be randomized: a) PS variability equal to 0%, b) PS variability equal to 45%, c) PS variability equal to 90%.
Noisy-PSV 2 : different levels of variable Pressure Support (PS) will be randomized: a) PS equal to Baseline and variability 0%; b) PS equal to Baseline and variability set in order achieve an increase or decrease of pressure of 5 cmH2O; c) PS equal to Baseline - 5 cmH2O and variability 0%; d) PS equal to Baseline - 5 cmH2O and set in order achieve an increase or decrease of pressure of 5 cmH2O.
Intensive Care Medicine Unit - IRCCS San Martino - IST
Genoa, Italy
Effect on arterial oxygenation in each setting of variability
The investigators perform an arterial blood gas and oxygenation is evaluated with PaO2/FiO2 ratio
Time frame: after 45 minutes of mechanical ventilation with each level of variable pressure support
work of breathing
work of breathing will be recorded as pressure-time product (PTP) measured on the esophageal pressure curve.
Time frame: every 9 minutes, up to 45 minutes, of mechanical ventilation in each level of variable pressure support
effects on hemodynamic
the investigator will record blood pressure and cardiac output
Time frame: after 45 minutes of mechanical ventilation with each level of variable pressure support
effect on arterial carbon dioxide
The investigators perform an arterial blood gas and arterial carbon dioxide is evaluated with PaCO2.
Time frame: after 45 minutes of mechanical ventilation with each level of variable pressure support
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