Comparative study of three flexiVent system configurations using mechanical test loads

The sole commercial system currently employing the forced oscillation technique (FOT) in small laboratory animals (flexiVent; SCIREQ Inc., Canada) was recently redesigned along with its operating software. Yet, many users still work with the legacy version or a mixed configuration. This study aimed to compare result accuracy and precision between three flexiVent system configurations and to quantify the impact of configuration changes on measured parameters. Physiologically relevant resistance or elastance were measured at 2.5 Hz on the following three system configurations using characterized mechanical test loads: (i) legacy flexiVent-flexiVent v5.3.4 (Leg-fV5), (ii) legacy flexiVent-flexiWare v7.2.1 (Leg-fW7), and (iii) flexiVent FX-flexiWare v7.2.1 (FX-fW7). Results demonstrated measurements of high precision that were consistent between system configurations. There was no statistical difference between system configurations in terms of measuring a predicted resistance. Measurements of elastance, on the other hand, were configuration-sensitive with FX-fW7 generating values that were closer to theoretical ones than the other two configurations. The largest impact on measurement outcomes was associated with the most noteworthy configuration change (i.e., software and hardware replacement). This effect was however constrained, with variations in the order of 3-5%, approximately. In conclusion, the latest version of the sole commercial pre-clinical FOT system currently available generated results that were equivalent or better than those acquired with two other system configurations. Given that configuration changes were associated with subtle parameter differences, best practice would recommend consistency within a study and reporting the full details of the system used.