Lung packing—also called glossopharyngeal insufflation or buccal pumping—is the technique of “pumping” extra air into the lungs after a full inhale, pushing lung volume above normal total lung capacity. Freedivers mainly use it to help equalisation at depth and (to a lesser extent) to increase oxygen stored in the lungs.
It can be useful. But it comes with a specific set of downsides that show up again and again across freediving physiology: it raises pressure inside the chest, stresses the lung tissue, and can destabilize circulation at exactly the worst time—right before a breath-hold.
Below is a consolidated set of the key negatives and health issues associated with packing.
Packing can increase intrathoracic pressure enough to reduce venous return (blood coming back to the heart). Less filling leads to lower stroke volume and lower cardiac output, which can reduce brain blood flow and trigger dizziness or fainting. This has been directly demonstrated with cardiac imaging and flow measurements in competitive divers.
Why it matters: fainting on land is bad; fainting on a boat, dock, or in shallow water before/after a dive can be catastrophic.
Even without full syncope, the same mechanism can leave you with less stable blood pressure and a less robust circulation going into the apnea. That means you may start the dive already closer to the edge—especially if you’re standing (i.e. apnea walk), moving, stressed, dehydrated, or combining packing with other risky habits.
Packing can push the lungs into an overstretched, high-pressure zone. The lung’s gas-exchange surface is thin and delicate—great for oxygen transfer, not great for extreme mechanical stress. Aggressive packing (or straining against a closed glottis) can increase the chance of pulmonary barotrauma (air leaks, tissue injury) even before the dive starts.
One of the most serious (though uncommon) hazards tied to pulmonary barotrauma is arterial gas embolism (AGE). If overpressure causes tiny ruptures in the lung’s air spaces, gas can enter the bloodstream and reach the arterial circulation. That can send bubbles to the brain or other organs and cause sudden, stroke-like symptoms.
What it can look like: abrupt confusion, weakness, vision disturbance, difficulty speaking, severe dizziness/vertigo, seizure-like activity, or collapse—especially if symptoms appear very quickly after packing or shortly after surfacing.
Why it matters: this is an emergency. If neurological symptoms appear, treat it as time-critical and seek urgent medical evaluation.
Deep freediving already loads the lungs via blood shift and pressure changes. Packing can add another layer of stress by combining very high initial inflation with high capillary pressures during/after deep diving. In practical terms, that may contribute to conditions where the lung barrier becomes “leaky,” leading to pulmonary edema (fluid in the lungs) and symptoms like cough, chest tightness, breathlessness, unusual fatigue, or sometimes blood.
Packing risk is not just “packing vs no packing.” The danger rises when it’s stacked with other lung/circulation stressors:
This is why some divers “get away with it” for a long time and then suddenly don’t—the load can be additive.
Packing can make depth/equalisation easier, which can encourage divers to push depth faster than their tissues, technique, and safety systems are ready for. The technique can become a shortcut—when it should be treated like specialized equipment: useful in the right hands, dangerous when used casually.
When the lungs and chest are overfilled, pressure rises inside the thorax. Your heart and the big veins returning blood to it get partially “squeezed,” so the heart fills less effectively. If filling drops enough, output drops and you can feel dizzy or faint—especially while standing.
Think of it as two different stress profiles:
Combine both aggressively and you may raise the risk of cough, chest tightness, shortness of breath, or post-dive performance drops.
If any of these appear after deep diving—especially in a session that involved packing—treat them as stop signals, not “normal post-session weirdness”:
The safer move is to stop diving, warm up, monitor, and seek medical advice if symptoms persist or are significant. Sudden neurological symptoms should be treated as an emergency.
is also important to be aware that any pre-existing lung injuries or scar tissue from previous lung injury or illness can make the tissue more uneven and fragile and therefore predispose it to lung barotauma, especially with the extra stress of packing.