Why the study?
The physiological breaking point terminating breath holding after face immersion is thought to be driven primarily by blood gases, but whether other factors such as lung volume contribute significantly was unclear.
Does breath holding at Total Lung Capacity compared to Functional Residual Capacity delay the physiological breaking point during simulated diving in healthy adults?
Does breath holding at Total Lung Capacity compared to Functional Residual Capacity delay the physiological breaking point during simulated diving in healthy adults?
Absolute Event Rate: 59% vs 32%
p-value: p=<0.001
High lung volume (Total Lung Capacity) significantly prolongs breath-holding duration during face immersion compared to lower lung volume, independent of the gas mixture pre-breathed.
May extend safe apnea tolerance via lung volume optimization in immersion; leaves open translation to diving safety or clinical protocols.
During breath holding after face immersion there develops an urge to breathe. The point that would initiate the termination of the breath hold, the “physiological breaking point,” is thought to be primarily due to changes in blood gases. However, we theorized that other factors, such as lung volume, also contributes significantly to terminating breath holds during face immersion. Accordingly, nine naïve subjects (controls) and seven underwater hockey players (divers) voluntarily initiated face immersions in room temperature water at Total Lung Capacity (TLC) and Functional Residual Capacity (FRC) after pre-breathing air, 100% O 2 , 15% O 2 / 85% N 2 , or 5% CO 2 / 95% O 2 . Heart rate (HR), arterial blood pressure (BP), end-tidal CO 2 (etCO 2 ), and breath hold durations (BHD) were monitored during all face immersions. The decrease in HR and increase in BP were not significantly different at the two lung volumes, although the increase in BP was usually greater at FRC. BHD was significantly longer at TLC (54 ± 2 s) than at FRC (30 ± 2 s). Also, with each pre-breathed gas BHD was always longer at TLC. We found no consistent etCO 2 at which the breath holding terminated. BDHs were significantly longer in divers than in controls. We suggest that during breath holding with face immersion high lung volume acts directly within the brainstem to actively delay the attainment of the physiological breaking point, rather than acting indirectly as a sink to produce a slower build-up of PCO 2 .
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McCulloch et al. (2021) studied Healthy volunteers (n=16). Breath holding at Total Lung Capacity (TLC) vs. Breath holding at Functional Residual Capacity (FRC) was evaluated on Breath hold duration (BHD) (p=<0.001).
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