Mid Sweden University

Physiological field research on breath-hold divers (freedivers) is challenging as divers are exposed to hyperbaric environments hostile to classical physiological measurement methods. Two main challenges are; I) The need of developing methods allowing measurements of physiological variables underwater at depth, II) To accompany the studied freediver in the water. The rapid vertical descent and ascent makes it impossible for researchers to use SCUBA to follow the participants to depth. We present new approaches in scientific diving to meet these demands. Our methods development of underwater technology has included water- and pressure-proof dataloggers to record and store data from a 12 lead ECG (250Hz) and photoplethysmograms from two SpO2 probes using red- and infrared signals (30Hz), combined with ambient pressure and temperature loggers. We previously used SCUBA to enable real-time blood pressure and ECG measurements on freedivers, by waiting for them at the bottom of their pre-determined depth. A breath-hold diving approach for the researcher was found to be superior due to enhanced flexibility in contrast to a heavy, static SCUBA setup. A method was developed in order to perform such scientific freediving safely, the basis being diving in e.g., the professional Japanese Ama divers. Combining the use of novel wearable water- and pressureproof physiological measurement methods with “scientific freediving”, seems to provide optimal work flexibility for both our study participants and the researcher, and may be the preferred approach for our future research.