Can SaO2 Measurements During Recovery Be Used to Detect Lung Barotrauma in Freedivers
Authors: Erika Schagatay
DOI / Source: n/a
Date: 14 November 2015
Reading level: Beginner
Why This Matters for Freedivers
Lung squeeze can be sneaky. You might feel “mostly fine,” but your lungs may still be struggling to move oxygen into your blood—and that can turn a second deep dive (same day or next day) into a much bigger problem. This report gives a simple, practical tool: using a finger pulse oximeter during recovery to spot delayed oxygen saturation as a warning sign that you should rest.
Synopsis
This “user-friendly” preliminary report comes from an AIDA-supported project focused on a big safety question in deep freediving: can we detect lung squeeze (pulmonary barotrauma / pulmonary edema) using something as simple as a finger pulse oximeter?
The idea is straightforward. After a deep dive, your oxygen saturation (SaO2) is usually low for a short time because you’ve used oxygen stores and haven’t fully “caught up” yet. But if your lungs are irritated or filled with fluid (even mildly), gas exchange is less efficient—so SaO2 can stay low for longer than normal. The report aims to map what “normal recovery” looks like after deep competition dives, then check whether delayed recovery matches real symptoms like chest discomfort, coughing, heavy breathing, or blood.
Measurements were collected during real AIDA depth competitions (CWT, CNF, and FIM), because athletes strain more and push closer to limits in competition than in training. SaO2 was recorded right after judging and tracked until it reached at least 97% for several minutes, or up to 10 minutes (and sometimes longer). Around 100 dives (25–100 m) were included after removing incomplete recordings. To define “normal recovery,” the analysis first excluded dives with chest symptoms or blackout, then used the remaining dives to establish typical recovery patterns.
The key practical finding is a “recovery window.” In dives without symptoms, SaO2 typically returned to 97% within: - about 4 minutes after dives shallower than 50 m, and - about 8–9 minutes after dives deeper than 50 m, with most symptom-free divers recovering within 10 minutes.
When symptomatic dives were included, the pattern became useful for screening: - If SaO2 was still below 97% at 10 minutes, lung symptoms were common. - If SaO2 was below 95% at 10 minutes, symptoms were very likely (almost always present in this dataset). There were a few exceptions both ways (some “false positives” and “false negatives”), which is why the report recommends continued monitoring and using symptoms + SaO2 together rather than relying on a single number.
The report also includes a smaller pilot comparison using lung ultrasound “comets” (a sign of lung fluid). Lower SaO2 values tended to match more ultrasound signs of fluid, supporting the idea that delayed SaO2 recovery can reflect pulmonary edema after deep dives.
Bottom line: this is a practical, field-ready safety idea. SaO2 recovery monitoring won’t diagnose everything, but it can help you catch “something’s not right” early—especially after deep, hard, or repetitive dives—so you can rest instead of stacking risk.
Abstract
This preliminary competition-based report evaluates whether oxygen saturation (SaO2) recovery measured by finger pulse oximetry can help detect lung barotrauma in freedivers. SaO2 recovery was recorded after approximately 100 depth competition dives (CWT, CNF, FIM; 25–100 m). Normal recovery patterns were established by excluding dives with chest symptoms or blackout, then comparing these patterns to dives with symptoms. In symptom-free dives, SaO2 typically reached 97% within about 4 minutes after dives <50 m and within about 8–9 minutes after dives >50 m, with most divers recovered within 10 minutes. At 10 minutes, SaO2 values below 97% were often associated with chest symptoms, and values below 95% were strongly associated with symptoms. Parallel ultrasound observations suggested lower SaO2 aligned with signs of lung fluid. The report concludes that SaO2 recovery monitoring is a useful, practical tool to help identify possible lung barotrauma after deep freediving.