Related Experiment Video
Updated: Dec 2, 2025

Monitoring Lung Function with Electrical Impedance Tomography in the Intensive Care Unit
Published on: September 6, 2024
Bench Assessment of Expiratory Valve Resistance of Current ICU Ventilators in Dynamic Conditions
Alexandre Pinède1, Martin Cour1,2, Florian Degivry1
1Médecine Intensive-Réanimation, Groupement Hospitalier Centre, Hôpital Edouard Herriot, Lyon, France.
Background:
We hypothesized that the lack of benefit of setting a low versus a high PEEP in patients with ARDS may be due in part to differences in the dynamic behavior of the expiratory valve in ventilators. We tested this hypothesis by conducting a bench comparison of the dynamic behavior of expiratory valves on ICU ventilators currently in use.
Methods:
We attached 7 ICU ventilators (C5, C6, Carescape, PB980, ServoU, V500, and V680) to the ASL 5000 lung model (passive condition with compliance 20 mL/cm H2O and resistance 5 cm H2O/L/s) and set in volume controlled mode (tidal volume 0.8 L, breathing frequency 10 breaths/min). Flow and pressure were measured just before the exhalation valve. At PEEP of 5, 10, and 15 cm H2O, the median instantaneous expiratory resistance, the time to valve opening, and the pressure time products above or below the values of PEEP (expressed in cm H2O × s) were determined.
Results:
Median instantaneous expiratory resistance values differed between the ventilators and PEEP settings with a significant interaction: at PEEP 5 cm H2O, the median (interquartile range) expiratory resistance values were 3.9 (3.5-4.7), 3.0 (3.0-3.1), 20.9 (15.8-24.9), 27.4 (26.5-43.2), 13.8 (13.6-13.9), 4.4 (4.0-4.6), and 34.3 (33.7-33.8) cm H2O/L/s, for the C5, C6, Carescape, PB980, ServoU, V500, and V680, respectively. For all the PEEP settings, the corresponding times to valve opening were 0.080 (0.077-0.082), 0.082 (0.080-0.085), 0.110 (0.105-0.110), 0.100 (0.085-1.05), 0.072 (0.062-0.072), 0.145 (0.115-0.150), and 0.075 (0.070-0.080) s, respectively, and pressure-time products were 2.8 (2.1-7.4), 6.8 (6.7-7.3), 2.4 (2.1-2.4), 3.5 (2.7-3.6), 1.8 (1.8-2.1), 2.8 (2.7-2.9), and 5.7 (5.4-5.9) cm H2O × s, respectively.
Conclusions:
The resistance of active expiratory valves differed significantly between the 7 ICU ventilators tested.
More Related Videos
Related Concept Videos
Mechanical Ventilation II: Invasive Ventilation
Negative-Pressure Ventilators
Negative-pressure ventilators create a vacuum around the chest or body to draw air into the lungs, simulating breathing. This method does not require an...
Mechanical Ventilation I: Indication and Settings
Assessment of Ventilation I: Respiratory Rate
A Ventilation assessment is critical for monitoring a patient's health status. Respiration, one of the most accessible vital signs, provides insights into the function of numerous body systems and can indicate serious health issues, such as brainstem injuries from head trauma.
Critical Guidelines for Assessing Ventilation:
Assessment of Ventilation II: Respiratory Depth and Rhythm
Respiratory depth measures the volume of air inhaled or exhaled during a breath. It can vary from shallow to deep and typically remains consistent when a person is at rest or asleep. Occasionally, individuals will automatically inhale deeply, known as sighing, which inflates the lungs with more air than normal breathing.
To assess respiratory depth, observe the degree of chest excursion or movement:
Ventilatory Modes
There are three ventilatory modes: full support, partial support, and spontaneous. These are described below.
Full Support Modes
Full support modes include controlled mechanical ventilation, continuous mandatory...
Mechanical Ventilation III: Noninvasive Ventilation
Noninvasive Positive-Pressure Ventilation...

