Breath-hold safety divers exhibit pulmonary stress but not decompression strain.

BACKGROUND

Breath-hold (BH) diving induces hypoxia-reoxygenation cycles and hydrostatic stress. Although decompression illness is traditionally associated with compressed-gas diving, neurological events have been reported after repetitive BH dives. The decompression stress, pulmonary effects, and inflammatory responses in BH safety divers (BHSDs) remain unclear.

METHODS

Fourteen BHSDs (11 males, 3 females; 35 ± 6 years) performed 174 dives (mean depth 18.8 ± 12.3 m). Vascular gas emboli (VGE) were assessed by echocardiography, pulmonary B-lines by lung ultrasound, salivary IL-6 and TNF-α by ELISA, and hydration by bioimpedance spectroscopy. Measurements were collected pre- and post-dive over two competition days and at 24-h and 48-h recovery. Linear and generalized linear mixed-effects models with Holm-corrected contrasts were used.

RESULTS

No VGE were detected. Pulmonary B-lines increased significantly post-dive on Day 1 (rate ratio = 1.60; p = 0.037) and Day 2 (RR = 2.30; p = 0.0008), returning below baseline at 48-h recovery (RR = 0.25; p = 0.0003). Salivary IL-6 peaked at 24-h recovery (+6.52 pg.mL-1; p < 0.0001), remaining elevated at 48 h (p < 0.0001). TNF-α rose from Day 2, reaching 25.16 pg.mL⁻¹ at 48-h recovery (p < 0.0001) with no return toward baseline. Hydration remained stable (p = 0.69).

CONCLUSION

A moderate inflammatory signal was observed up to two days following BH sessions. The BHSDs did not demonstrate any VGE but rather exhibited pulmonary B-lines consistent with the observed salivary inflammatory markers. Despite the absence of documented incidents or accidents, it is strongly recommended that BHSDs allocate additional days for recovery.