Related Experiment Video
Updated: Nov 7, 2025

A Model to Simulate Clinically Relevant Hypoxia in Humans
Published on: December 22, 2016
[Pathophysiology of COVID-19 related happy hypoxemia]
Gautier Breville1, Alice Accorroni1, Gilles Allali1
1Service de neurologie, Département des neurosciences cliniques, HUG, 1211 Genève 14.
Abstract:
A significative proportion of patients with pulmonary-related COVID-19 initially present with « silent » or « happy » hypoxemia, a term denoting an absence of dyspnea or other respiratory distress symptoms in face of profound hypoxemia. COVID-19 is a multisystemic disease characterized by the diffusion of SARS-COV-2 through the blood and a widespread secondary immune response. Most of the organs are involved, including the brain and this translates into the development of acute encephalopathy and other complications. Silent hypoxemia and the consequent "vanishing dyspnea" represent a loss of warning signal and may be associated with a rapid clinical worsening and a fatal outcome. In this article, we will describe the physiological basis of ventilation and we will elucidate the different pathophysiological mechanisms underlying the phenomenon of silent hypoxemia in COVID-19.
Related Concept Videos
Acute Respiratory Failure-II
The underlying physiological abnormalities that contribute to hypoxemic respiratory failure include:
Hypoxia
Types of Hypoxia
There are four primary types of hypoxia, each resulting from a different cause:
1. Anemic hypoxia: This type occurs due to insufficient oxygen delivery caused by a lack of red blood cells (RBCs) or RBCs with abnormal or...
Treatment for Pulmonary Arterial Hypertension: Oxygen Therapy for Respiratory Failure
Oxygen therapy is vital in increasing and maintaining blood oxygen levels in PAH patients. As a result, it aids in reducing fatigue,...
Physiological Control of Respiration
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...
Pneumonia II: Pathophysiology
Hyperpnea and Hyperventilation

