  Objective: To study to what extent or durations of ventilation effect in a
single no-decompression dive of 12 meters to a diver. Methods: There are 29
healthy volunteers divers assigned into SCUBA diving of 12m-depth underwater
(the Experimental Group, EG)and chamber dive under 2.2 ATA for 20min (the
Control Group, CG) matched with the factors of the age,gender,BMI and Forced
Vital Capacity (FVC).Ventilation functions were measured by spirometer before
diving and in 1h and 24h of post-hyperbaric exposure. Used independent samples
T tests to compare the differences between the EG and CG.Analyzed of variance
through repeated measurement data of different time point before or after high
pressure exposure by SPSS 20.0. Results: The Inspiratory Reserve Volume(IRV)
rises while the Expiratory Reserve Volume(ERV) falls significantly in 1h after
high pressure release(p<0.05).So as with the Inspiratory Capacity (IC) and the
Vital Capacity (VC) increased accordingly. The Ratio of FEV1.0 to VC (FEV1.0%t)
is higher in CG than EG (t=-2.189,p=0.033) due to the change of VC. But the
effects did not last for 24 h after high pressure relief. Conclusions:
Ventilation is restricted during the 20min of hyperbaric exposure whether under
12m-depth water or in a 2.2ATA hyperbaric chamber. But the effect recovered
close to normal within 24 h. But the effect recovered close to normal within 24
h. The extent of restriction of underwater diving is larger than the dry air
hyperbaric chamber dive. Higher water medium density, submerged compressing
blood volume of lower limbs and raising inertia added by portable underwater
breathing apparatus all might be attributable to the ventilation effects.
