Accuracy of tidal volume delivery by five different models of large-animal ventilators.

OBJECTIVE

To determine the accuracy of tidal volume (V) delivery among 5 different models of large-animal ventilators when tested at various settings for V delivery, peak inspiratory flow (PIF) rate, and fresh gas flow (FGF) rate.

SAMPLE

4 different models of pneumatically powered ventilators and 1 electrically powered piston-driven ventilator.

PROCEDURES

After a leak flow check, each ventilator was tested 10 times for each experimental setting combination of 5 levels of preset V, 3 PIF rates, and 4 FGF rates. A thermal mass flow and volume meter was used as the gold-standard method to measure delivered V. In addition, circuit systems of rubber versus polyvinyl chloride breathing hoses were evaluated with the piston-driven ventilator. Differences between preset and delivered V (volume error [ΔV]) were calculated as a percentage of preset V, and ANOVA was used to compare results across devices. Pearson correlation coefficient analyses and the coefficient of determination () were used to assess potential associations between the ΔV and the preset V, PIF rate, and FGF rate.

RESULTS

For each combination of experimental settings, ventilators had ΔV values that ranged from 1.2% to 22.2%. Mean ± SD ΔV was 4.8 ± 2.5% for the piston-driven ventilator, compared with 6.6 ± 3.2%, 10.6 ± 2.9%, 13.8 ± 2.97%, and 15.2 ± 2.6% for the 4 pneumatic ventilators. The ΔV increased with higher PIF rates ( = 0.69), decreased with higher FGF rates ( = 0.62), and decreased with higher preset V ( = 0.58).

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that the tested ventilators all had ΔV but that the extent of each of ΔV varied among ventilators. Close monitoring of delivered V with external flow and volume meters is warranted, particularly when pneumatic ventilators are used or when very precise V delivery is required.