Related Experiment Video
Updated: Jul 7, 2026

Monitoring Lung Function with Electrical Impedance Tomography in the Intensive Care Unit
Published on: September 6, 2024
A ventilator requirement index
John R Bach1, Miguel Goncalves, Michal Eisenberg
1Department of Physical Medicine and Rehabilitation, UMDNJ-New Jersey Medical School, Newark, New Jersey, USA.
Objective:
To determine the efficacy of vital capacity (VC) and a proposed ventilator requirement index (VRI) for justifying ventilator prescription and use for patients with neuromuscular/chest wall diseases (NMD).
Design:
Prospective observational study in which 319 patients with NMD, including 187 ventilator users, were separated into four groups: (1) asymptomatic, (2) abnormal specific screening factors and/or symptomatic, (3) ventilator use 8-20 hrs/day, and (4) >20 hrs/day of ventilator use. The VRI was defined as 60 x Ti/(Ttot)2 x (Vt/VC) x RR, where Ti = inspiratory time of one breath (secs), Ttot = total time of one breath (secs), Vt = tidal volume (ml) at rest, VC = vital capacity (ml), and RR = respiratory rate.
Results:
The overall analysis of variance F-tests and post hoc pairwise contrasts were significant (P < 0.001) for differences in the VC and VRI across groups. Thus, VC and VRI are independent predictors of group membership. Satisfying VC or VRI criteria signaled the highest number of patients benefiting from ventilator use.
Conclusions:
The prescription of one or two ventilators can be justified by both VC and VRI, with the combination being most sensitive.
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
Mechanical Ventilation III: Noninvasive Ventilation
Noninvasive Positive-Pressure Ventilation (NIPPV)
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:
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...
Respiratory Volumes and Capacities