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Related Concept Videos

Mechanical Ventilation I: Indication and Settings01:29

Mechanical Ventilation I: Indication and Settings

Mechanical ventilation is a life-saving technique for managing acute respiratory failure and other respiratory complications. The process involves using a machine known as a ventilator to supply oxygen to the lungs and assist in removing carbon dioxide. It serves as a bridge to long-term mechanical ventilation or a temporary measure until ventilatory support is discontinued. The ventilator can maintain this function for a prolonged period, providing critical support for patients until they can...
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...
Factors Affecting Pulmonary Ventilation01:19

Factors Affecting Pulmonary Ventilation

Besides the pressure difference between the external environment and the lungs, the airflow rate and ease of pulmonary ventilation are also influenced by three other factors: surface tension of the fluid in the alveoli, compliance of the lungs, and airway resistance.
Alveolar Surface Tension
The alveolar fluid lines the luminal surface of the alveoli and exerts a force called surface tension. This force is caused by the polar water molecules in the liquid being more strongly attracted to each...
Physiological Control of Respiration01:23

Physiological Control of Respiration

Introduction
Breathing, a seemingly passive process, is regulated by the respiratory center in the brainstem. This center coordinates the involuntary control of respirations, which means it occurs without conscious effort, ensuring a smooth and uninterrupted pattern.
Regulation of Ventilation
The body maintains ventilation by monitoring levels of carbon dioxide (CO2), oxygen (O2), and hydrogen ion concentration (pH) in the arterial blood. Among these factors, the level of CO2 plays a crucial...
Ventilatory Modes01:14

Ventilatory Modes

Mechanical ventilators are life-saving devices that support or replace spontaneous breathing. They deliver breaths to patients through varying methods known as ventilator modes. Understanding these modes is critical for healthcare providers managing patients with respiratory failure.
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 Ventilation01:23

Mechanical Ventilation III: Noninvasive Ventilation

Noninvasive positive-pressure ventilation (NIPPV), continuous positive airway pressure (CPAP), and bilevel positive airway pressure (BiPAP) are essential methods in respiratory care. These ventilation techniques offer unique benefits for patients with various respiratory conditions, providing adequate support without requiring intubation. Let's explore how each method is crucial in improving patient outcomes and enhancing respiratory therapy.
Noninvasive Positive-Pressure Ventilation (NIPPV)

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Updated: Jun 18, 2026

Ex Vivo Porcine Experimental Model for Studying and Teaching Lung Mechanics
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Ex Vivo Porcine Experimental Model for Studying and Teaching Lung Mechanics

Published on: April 19, 2024

Ventilatory efficiency: Physiological modelling and mechanistic validation.

Paulo T Muller1, Beate Stubbe2, Till Ittermann2

  • 1Faculty of Medicine, Department of Pneumology, Federal University of Mato Grosso do Sul, Campo Grande, Brazil.

The Journal of Physiology
|June 17, 2026
PubMed
Summary
This summary is machine-generated.

A new index, the bounded ventilatory efficiency index (ηV̇E), accurately measures exercise efficiency beyond the first ventilatory threshold (VT1). This index remains stable across the lifespan and is a key predictor of diffusing capacity in individuals with lung conditions.

Keywords:
diffusing capacityexercise physiologyreference valuessemi‐logarithmic modellingventilatory efficiency

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Last Updated: Jun 18, 2026

Ex Vivo Porcine Experimental Model for Studying and Teaching Lung Mechanics
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3D Cine Magnetic Resonance Imaging of Respiratory Motion in Mechanically Ventilated Mice and Rats
08:22

3D Cine Magnetic Resonance Imaging of Respiratory Motion in Mechanically Ventilated Mice and Rats

Published on: September 19, 2025

Area of Science:

  • Exercise Physiology
  • Pulmonary Function Testing
  • Biomedical Engineering

Background:

  • Traditional ventilatory efficiency indices like the V̇E-V̇CO2 slope are limited in capturing nonlinear ventilatory behavior beyond the first ventilatory threshold (VT1).
  • Existing methods may underestimate crucial ventilatory adjustments during the critical phase from VT1 to peak exercise.

Purpose of the Study:

  • To introduce and validate a novel bounded ventilatory efficiency index (ηV̇E) using a semi-logarithmic model to better represent post-VT1 ventilatory dynamics.
  • To establish normative values for ηV̇E in a large cohort of healthy adults and assess its relationship with age, sex, and lung function.
  • To evaluate the utility of ηV̇E in predicting diffusing capacity in individuals with isolated diffusive disturbances.

Main Methods:

  • Application of a semi-logarithmic model to linearize the post-VT1 ventilatory response, calculating an empirical slope (b_emp).
  • Normalization of b_emp to a theoretical CO2 clearance limit, scaled by predicted maximal voluntary ventilation (MVV_pred), to derive ηV̇E.
  • Analysis of data from 1150 healthy adults and a post hoc cohort with isolated diffusive disturbance.

Main Results:

  • The ηV̇E index demonstrated minimal sex-related variation and weak positive associations with age and FEV1_pred, accounting for only 8.5% of total variance.
  • Empirical and theoretical slopes declined with age, but ηV̇E remained stable across the lifespan, supported by deterministic simulations.
  • In individuals with diffusive disturbance, ηV̇E was the sole significant independent predictor of reduced diffusing capacity, highlighting its physiological relevance over geometric factors.

Conclusions:

  • The bounded ventilatory efficiency index (ηV̇E) offers a reproducible, scale-independent, and physiologically relevant measure of ventilatory efficiency across health and aging.
  • ηV̇E refines the interpretation of ventilatory efficiency by integrating ventilatory drive, gas exchange, and diffusion capacity.
  • This framework provides a unified and applicable tool for physiological and clinical evaluation of ventilatory function.