Related Experiment Video

Updated: Sep 28, 2026

Monitoring Lung Function with Electrical Impedance Tomography in the Intensive Care Unit
05:56

Monitoring Lung Function with Electrical Impedance Tomography in the Intensive Care Unit

Published on: September 6, 2024

Accuracy of displayed values of tidal volume in the pediatric intensive care unit

Rosemary A Castle1, Catherine J Dunne, Quen Mok

  • 1Portex Anaesthesia, Intensive Therapy and Respiratory Medicine Unit, Institute of Child Health, London, UK.

Critical Care Medicine
|November 21, 2002
PubMed

Insights

Ventilator expired tidal volumes (VT(E)) measured at the expiratory valve are inaccurate in children. Measurement at the airway opening is crucial for reliable ventilation monitoring.

Area of Science:

  • Pediatric critical care medicine
  • Respiratory physiology
  • Mechanical ventilation

Background:

  • Accurate measurement of expired tidal volumes (VT(E)) is essential for effective mechanical ventilation in children.
  • Many ventilators measure exhaled volume at the expiratory valve, but the accuracy of these readings is not always clear.

Purpose of the Study:

  • To assess the accuracy of expired tidal volumes (VT(E)) displayed by a frequently used ventilator (Servo 300) that measures exhaled volume at the expiratory valve.
  • To compare the ventilator's displayed VT(E) with measurements taken at the airway opening.

Main Methods:

  • A prospective study was conducted in a pediatric tertiary referral center.
  • 56 intubated children (3 weeks to 16.6 years) on Servo 300 ventilators were included.
  • Exhaled VT(E) was measured simultaneously using the Servo 300 and a validated CO2SMO Plus respiratory monitor (airway opening measurement).

Main Results:

  • The CO2SMO Plus respiratory monitor demonstrated in vitro accuracy within +/-5%.
  • The Servo 300's displayed VT(E) overestimated true VT(E) by 2-91%, with errors varying by pressure, VT(E), and circuit size.
  • After correction for circuit compliance, the Servo 300's effective VT(E) underestimated true VT(E) by up to 64% in infants and overestimated by up to 29% in older children.

Conclusions:

  • The accuracy of delivered tidal volumes is highly dependent on the measurement site.
  • Ventilator-displayed VT(E) measured at the expiratory valve is an inconsistent and misleading indicator of true delivered volumes.
  • Measurement at the airway opening is necessary for accurate ventilation monitoring in pediatric patients.
Abstract

More Related Videos

Combining Volumetric Capnography And Barometric Plethysmography To Measure The Lung Structure-function Relationship08:25

Combining Volumetric Capnography And Barometric Plethysmography To Measure The Lung Structure-function Relationship

Published on: January 8, 2019

Related Concept Videos

Respiratory Volumes01:15

Respiratory Volumes

Respiratory volumes are crucial metrics, meticulously measured to quantify the air exchanged in and out of the lungs during various phases of the breathing cycle. These precise measurements are vital for assessing lung function, diagnosing respiratory conditions, and monitoring overall respiratory health. Each parameter provides specific insights into the mechanics of breathing and the functional capacity of the lungs.
Tidal Volume (TV) Tidal volume (TV) is the air inhaled or exhaled in a...
Assessment of Ventilation I: Respiratory Rate01:20

Assessment of Ventilation I: Respiratory Rate

Assessment of Ventilation
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:
Respiratory Volumes and Capacities01:22

Respiratory Volumes and Capacities

The respiratory system is responsible for the intake of oxygen and the expulsion of carbon dioxide from the body. Respiratory volumes describe the volume of air in the lungs at different phases of the respiratory cycle. Tidal volume is the air breathed in and out during normal, quiet breathing. Inspiratory reserve volume is the air that can be forcefully inspired beyond the tidal volume. In contrast, expiratory reserve volume refers to the air that can be expelled from the lungs after a normal...
Respiratory Capacities01:24

Respiratory Capacities

Respiratory capacities are crucial indicators of lung function, representing the maximum amount of air an individual's respiratory system can handle during various breathing phases.
One key metric is the Inspiratory Capacity (IC), which represents the maximum amount of air that can be inhaled with full effort. IC is calculated by summing the tidal volume and inspiratory reserve volume, typically ranging from 2.4 to 3.6 liters.
The Functional Residual Capacity (FRC) represents the air in the...
Mechanical Ventilation II: Invasive Ventilation01:23

Mechanical Ventilation II: Invasive Ventilation

Ventilators are essential medical equipment used to aid patients with respiratory difficulties. Their primary function is to assist or replace spontaneous breathing by providing mechanical ventilation. There are two general classes of mechanical ventilators: negative-pressure and positive-pressure ventilators.
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...
Lung Capacity01:47

Lung Capacity

The air in the lungs is measured in volumes and capacities. Lung volume measures reflect the amount of air taken in, released, or left over after a lung function, like a single inhalation. Lung capacity measures are sums of two or more lung volume measures.