Characteristic of volume-controlled ventilation with small tide volume in hyperbaric oxygen chamber

To evaluate the characteristics of tidal volume (VT) delivered by a Shangrila590 ventilator with preset tide volume (VTset) 50-300 mL in volume-controlled ventilation (VCV) during hyperbaric oxygen (HBO₂) therapy.

Experiments were conducted in a multi-place HBO₂ chamber at 1.0, 2.0, and 2.8 atmospheres absolute (ATA abs) and were divided into three groups accordingly. The ventilator was connected to the test lung in the chamber. The VTset of the ventilator was adjusted before the experiments. At five VTset levels (50, 100, 150, 200, 300 mL), the VT and inspiratory peak pressure (Ppeak) detected by the ventilator and the test lung were recorded for 30 cycles (n=30). The measurements of the test lung were considered to be the true value, and the ventilator and test lung data were compared to evaluate the accuracy of the ventilator. Test lung compliance (CTL) was detected by the ventilator, and breathing circuit compliance (CBC) was calculated by measuring the pressure and volume of the breathing circuit. Ventilation data were compared among three groups to clarify the change during HBO₂.

At every VTset, the VT detected by the test lung was different from the ventilator at 1.0~2.8 atm abs (p<0.05), and the VT changed differently among the three groups (p<0.05). CTL and the CBC decreased with increasing ambient pressure (p<0.05). The Ppeak of VCV increased (p<0.05) with increasing ambient pressure.

The Shangrila590 ventilator has limitations in small VTset (50- 300 mL) VCV during HBO₂ therapy. CBC and CTL levels change due to high gas density. High Ppeak may occur in VCV with stable VT, also caused by high gas density.