Accuracy of tidal volume, compliance, and resistance measurements on neonatal ventilator displays: An in vitro assessment
ABSTRACT To determine the accuracy of measures of respiratory mechanics derived from neonatal ventilators using an in vitro passive physical lung model to simulate newborn pulmonary conditions.
Test lung models.
Three test lungs were constructed to simulate three severities of neonatal lung disease, with ranges of compliance from 0.5 to 2.0 mL/cm H2O and resistance from 25 to 150 cm H2O/(L/sec). Each ventilator was tested using 27 combinations of peak inspiratory pressure (15-25 cm H2O), positive end-expiratory pressure (5-7 cm H2O), and rate settings (20-60 B/min). Data were compared for five different ventilators across simulated lung severity as the ratio of ventilator readout to test lung reference value. A ratio of 1.0 indicated a completely unbiased result.
Overall, four of the five ventilators under-read expired tidal volume by about 1%-12% across all lung conditions, whereas the VIP Bird readout ranged from -4% to +4% bias. Changes in ventilator settings had only a modest effect on mechanics readout. As peak inspiratory pressure progressed from 15 to 25 cm H2O, bias in tidal volume readout changed from +5.0% to -2.5% (p < .001) in the VIP Bird, and from -11% to -9% (p < .001) in the Draeger Babylog VN500. Between positive end-expiratory pressure levels of 5 and 7 cm H2O, tidal volume bias in the Babylog varied between -13% and -7% (p < .001). In progressing from simulated normal to severely ill lung condition, bias in compliance measurements by the Avea and SLE5000 increased from -18% to -40% whereas in the VIP Bird it remained between -17% to -13%, and in the Draeger Evita XL-neo it changed from +17% to -13% and from -8% to -16% in the Babylog. Ratio of ventilator resistance readout to reference value with progressing simulated lung condition changed from 2.0 to 1.0 for the Draeger Evita, 1.6 to 1.1 for the Babylog, 4.2 to 2.0 for the SLE, and from 11.7 to 5.6 for the VIP Bird. The Avea, by design, did not display resistances >100 cm H2O/(L/sec), but overestimated the simulated normal lung resistance of 25 cm H2O/(L/sec) by a factor of 2.5.
Neonatal ventilator respiratory mechanics measurements and computation methods need further standardization to be useful in clinical settings.
Respiratory care 10/2014; 59(10):1606-7. DOI:10.4187/respcare.03616 · 1.84 Impact Factor
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ABSTRACT: Background Mechanical ventilation is a therapeutic action for newborns with respiratory diseases but may have side effects. Correct equipment knowledge and training may limit human errors. We aimed to test different neonatal mechanical ventilators’ performances by an acquisition module (a commercial pressure sensor plus an isolated chamber and a dedicated software). Methods The differences (ΔP) between peak pressure values and end-expiration pressure were investigated for each ventilator. We focused on discrepancies among measured and imposed pressure data. A statistical analysis was performed. Results We investigated the measured/imposed ΔP relation. The ΔP do not reveal univocal trends related to ventilation setting parameters and the data distributions were non-Gaussian. Conclusions Measured ΔP represent a significant parameter in newborns’ ventilation, due to the typical small volumes. The investigated ventilators showed different tendencies. Therefore, a deep specific knowledge of the intensive care devices is mandatory for caregivers to correctly exploit their operating principles.Italian Journal of Pediatrics 12/2015; 41(1). DOI:10.1186/s13052-015-0112-z
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ABSTRACT: Several new generation neonatal ventilators that incorporate conventional as well as high frequency ventilation (HFOV) have appeared on the market. Most of them offer the possibility to use HFOV in a volume-targeted mode, despite absence of any preclinical data. With a bench test, we evaluated the performances of 4 new neonatal HFOV devices and compared them to the SensorMedics HFOV device. Expiratory tidal volumes (VT) were measured for various ventilator settings and lung characteristics (ie, modifications of compliance and resistance of the system), to mimic several clinical conditions of pre-term and term infants. Increasing the frequency proportionally decreased the VT for all the ventilators, although the magnitude of the decrease was highly variable between ventilators. At 15 Hz and a pressure amplitude of 60 cm H2O, the delivered VT ranged from 3.5 to 5.9 mL between devices while simulating pre-term infant conditions and from 2.6 to 6.3 mL while simulating term infant conditions. Activating the "volume-targeted" mode in the 3 machines that offer this mode allowed the VT to remain constant over the range of frequencies and with changes of lung mechanical properties, for "pre-term infant" settings only while targeting a VT of 1 mL. These new generation neonatal ventilators were able to deliver adequate VT under pre-term infant, but not term infant respiratory system conditions. The clinical relevance of these findings will need to be determined by further studies. Copyright © 2015 by Daedalus Enterprises Inc.Respiratory care 11/2014; 60(3). DOI:10.4187/respcare.03048 · 1.84 Impact Factor