Fig. 2

Box plot of tidal volume (VT) (a), positive end-expiratory pressure (PEEP) (b) and pressure support (PS) (c). Dotted lines represent the 10% error range. Black line represents exact VT value delivery. Values are provided as median and interquartile. A p value equal or below 0.05 was considered significant. *p < 0.05; ^§ p < 0.05 as compared to S1, PB980 and Servo-U. ^† p < 0.005 as compared to R860, PB980 and Servo-U. There was a significant difference in terms of VT delivery precision between devices (a; p = 0.0498). All devices except S1 depicted a median VT value within the 10% error range. PB980 had the lowest error in terms of VT delivery, but Servo-U had the highest precision in response to respiratory mechanics modifications. V500 and V680 had relatively low error, but low precision in response to respiratory mechanics modifications. While median PEEP delivery was within the reliability range for all devices (b), V500 was significantly different to the other devices in terms of precision. S1 had the lowest error, but with rather low precision. Servo-U, PB980 and R860 had low error and high precision. When considering mean values, three devices delivered PS values higher than the reliability range (Servo-U: 13 ± 6%; PB980: 11 ± 12%; S1: 17 ± 14.4%; p < 0.001). Pressure support delivery was higher than the 10% error range for two devices (Servo-U and S1). Precision in response to respiratory mechanics modifications was low for PB980, S1 and R860