Pulmonary gas exchange is reduced by the cardiovascular diving response in resting humans
Authors: Johan P. A. Andersson, Gustaf Biasoletto-Tjellström, Erika K. A. Schagatay
DOI / Source: 10.1016/j.resp.2007.10.016
Date: 28 October 2007
Reading level: Beginner
Why This Matters for Freedivers
This is one of the clearest “yes, it saves oxygen” papers for static-style breath-holds: when the dive response is stronger (cold face immersion), your lungs give up oxygen more slowly. That means you can preserve your lung oxygen store for longer—exactly what you want in static, and a big part of why face immersion can make a breath-hold feel easier and safer.
Synopsis
Freedivers often feel a big difference between holding their breath in air versus holding it with the face in cold water. In water, the heart rate drops more, the body feels “switched into diving mode,” and many people can hold longer. But what’s actually happening to the oxygen in your lungs. Does the human dive response really reduce how fast oxygen is transferred from the lungs into the blood — even when you’re not exercising.
This study tested that directly in resting humans.
What they did
Sixteen healthy men lay prone and relaxed. They performed breath-holds in two conditions:
1) Apnea in air (face held just above the water surface).
2) Apnea with face immersion in cold water (10–11°C).
The key detail is that the breath-holds were the same duration in both conditions. After each subject did two max apneas to establish capacity, the researchers set a fixed “submax” time (about 20 seconds shorter than the shorter max attempt). Then they did four fixed-time apneas (two in each condition, alternating). Average fixed apnea duration was about 145 seconds.
They standardised the starting breath too: before each apnea, subjects exhaled to residual volume and then inhaled a set volume equal to 90% of their prone vital capacity. No intentional hyperventilation.
What they measured
They used respiratory gas analysis to calculate pulmonary O₂ uptake (how much oxygen was removed from the lungs per minute) and CO₂ elimination during the apnea. They also tracked: - heart rate, - blood pressure, - skin blood flow (a marker of peripheral vasoconstriction), - oxygen saturation (SaO₂), - plasma lactate (in most participants).
The main finding: oxygen leaves the lungs more slowly
Compared with normal breathing at rest, oxygen uptake from the lungs dropped during breath-holding (that’s expected). But the crucial point is:
- During apnea in air, pulmonary O₂ uptake dropped from the resting control.
- During apnea with cold face immersion, pulmonary O₂ uptake dropped even more.
In numbers, resting oxygen uptake was about 4.6 ml/min/kg, fell to 3.6 during apnea in air, and fell further to 3.4 with face immersion. That’s an oxygen-conserving effect: the “diving mode” made your lungs spend oxygen more slowly.
SaO₂ and end-tidal oxygen also fell in both conditions, but the drop was smaller with face immersion — consistent with preserving the lung oxygen store for longer.
What about CO₂ and lactate
CO₂ elimination from blood to lungs was massively reduced during apnea (again expected), and it was similarly reduced in both conditions. Plasma lactate didn’t rise in this protocol, which surprised the authors because some older studies saw lactate increases after apneas. They suggest this could be because many subjects were trained breath-hold divers (training may change lactate response), or because lactate timing is tricky and they may have missed a brief peak.
Why this happens
The most likely mechanism is the classic cardiovascular dive response: - bradycardia (lower heart rate), - reduced cardiac output, - peripheral vasoconstriction (less blood flow to skin and limbs).
With less blood flow pulling oxygen out of the lungs, the lungs’ oxygen store is depleted more slowly. The trade is that peripheral tissues may rely more on local oxygen stores or anaerobic pathways, while vital organs get protected.
Takeaway
Even at rest, the human dive response is not just a “heart rate trick.” It measurably reduces pulmonary oxygen uptake. That’s a clean physiological explanation for why face immersion can help static breath-holds: you’re literally slowing down the rate at which you drain your lung oxygen.
Abstract
The diving response reduces the pulmonary O2 uptake in exercising humans, but it has been debated whether this effect is present at rest. Therefore, respiratory and cardiovascular responses were recorded in 16 resting subjects, performing apnea in air and apnea with face immersion in cold water (10°C). Duration of apneas were predetermined to be identical in both conditions (average: 145 s) and based on individual maximal capacity (average: 184 s). Compared to apnea in air, an augmented diving response was elicited by apnea with face immersion. The O2 uptake from the lungs was reduced compared to the resting eupneic control (4.6 ml min−1 kg−1), during apnea in air (3.6 ml min−1 kg−1) and even more so during apnea with face immersion (3.4 ml min−1 kg−1). We conclude that the cardiovascular adjustments of the diving response reduces pulmonary gas exchange in resting humans, allowing longer apneas by preserving the lungs’ O2 store for use by vital organs.