Air Hunger - A Primal Sensation And A Primary Element Of Dyspnea
Authors: Robert B. Banzett, Robert W. Lansing and Andrew P. Binks
DOI / Source: https://doi.org/10.1002/cphy.c200001
Date: February 2021
Reading level: Advanced
Why This Matters for Freedivers
This paper supports a crucial freediving lesson: the urge to breathe is driven mainly by CO₂ and breathing mechanics, not by how “safe” your oxygen level is—so discomfort is not a reliable safety gauge. It also helps explain why calm technique and familiarization matter: air hunger isn’t only physical; it strongly recruits the brain’s threat/emotion systems, which can amplify stress and worsen decisions during a dive.
Synopsis
Most freedivers know the feeling: early in a breath-hold you’re calm, then a powerful “need to breathe” starts to build and can take over your whole attention. This paper explains that sensation in detail and calls it air hunger—a primal alarm signal your brain uses to protect gas exchange. It’s not just “discomfort”: it can trigger strong emotions like anxiety, fear, and frustration, which is why it’s also a major part of clinical shortness of breath (dyspnea). 
The key idea is that air hunger comes from a mismatch: your brain’s drive to breathe is high, but the ventilation you’re actually getting is “not enough.” The paper reviews what increases that drive (especially rising CO₂, and to a lesser degree hypoxia, exercise, and acidosis) and what relieves air hunger (most strongly lung inflation/ventilation—even a few breaths can rapidly reduce the sensation). It also summarizes experiments showing people can rate air hunger reliably on scales, and it describes brain regions that light up during air hunger—especially areas involved in homeostasis and emotion—helping explain why it feels so urgent and can get “panicky.”
Abstract
The sensation that develops as a long breath hold continues is what this article is about. We term this sensation of an urge to breathe “air hunger.” Air hunger, a primal sensation, alerts us to a failure to meet an urgent homeostatic need maintaining gas exchange. Anxiety, frustration, and fear evoked by air hunger motivate behavioral actions to address the failure. The unpleas- antness and emotional consequences of air hunger make it the most debilitating component of clinical dyspnea, a symptom associated with respiratory, cardiovascular, and metabolic diseases. In most clinical populations studied, air hunger is the predominant form of dyspnea (colloqui- ally, shortness of breath). Most experimental subjects can reliably quantify air hunger using rating scales, that is, there is a consistent relationship between stimulus and rating. Stimuli that increase air hunger include hypercapnia, hypoxia, exercise, and acidosis; tidal expansion of the lungs reduces air hunger. Thus, the defining experimental paradigm to evoke air hunger is to elevate the drive to breathe while mechanically restricting ventilation. Functional brain imaging studies have shown that air hunger activates the insular cortex (an integration center for perceptions related to homeostasis, including pain, food hunger, and thirst), as well as limbic structures involved with anxiety and fear. Although much has been learned about air hunger in the past few decades, much remains to be discovered, such as an accepted method to quantify air hunger in nonhuman animals, fundamental questions about neural mechanisms, and adequate and safe methods to mitigate air hunger in clinical situations.