Validation of a snorkel prototype for measuring gas Exchange parameters during swimming. Med Sci Sports Exerc

To assess VO2 in swimming a snorkel device is needed to convey gasses. Toussaint (1987) validated a snorkel device connected to Douglas bag. Conversely, when a snorkel was connected to K4b2 (Cosmed, Rome, IT), the validation studies (Keskinen 2003, Gayda 2010) reported some low systematic differences versus the use of K4b2 with the standard facemask (Mask). PURPOSES : To find a possible explanation of these systematic errors, we detected the air temperature at the turbine to validate a snorkel prototype. Also, the snorkel prototype with 2 (SV2) and 4 (SV4) valves was compared with a Mask connected with K4b2. METHODS: Nine subjects performed trails on a 25m swimming pool and on bike ergometer on separate days at 3 constant loads (low, medium, high). Trails were performed in random order: with SV2 and SV4 while swimming; with Mask, SV4, and SV2 while cycling. Air temperature at the turbine of the K4b2 system was measured at each condition. RESULTS : Considering each parameter [VO2, VCO2 ,VE (table) and also VT, FEO2, FECO2] and comparing the different conditions [SV4 vs SV2 both in swimming (table) and cycling, Mask vs SV4, Mask vs SV2 (table)] by Passing-Bablok regression analysis, the 95% CI always contained the value 1 for the slope and the 0 for the intercept, thus rejecting the proportional and the systematic difference hypothesis. CONCLUSION : Temperature measure at the turbine is needed since, as erroneously believed by others, the turbine do not have any temperature sensors so that the manufacturer recommends adjusting it to the ambient value when a snorkel is used. We prove that data must be adjusted to the real temperature of expired gases in order to have valid gas exchange values. Also, SV2 and SV4 snorkel were both valid, being the SV2 more comfortable.