Reliable tidal volume estimates at the airway opening with an infant monitor during high-frequency oscillatory ventilation.
OBJECTIVE
To assess the suitability of a hot-wire anemometer infant monitoring system (Florian, Acutronic Medical Systems AG, Hirzel, Switzerland) for measuring flow and tidal volume (Vt) proximal to the endotracheal tube during high-frequency oscillatory ventilation.


METHODS
In vitro model study.


METHODS
Respiratory research laboratory.


METHODS
In vitro lung model simulating moderate to severe respiratory distress.


METHODS
The lung model was ventilated with a SensorMedics 3100A ventilator. Vt was recorded from the monitor display (Vt-disp) and compared with the gold standard (Vt-adiab), which was calculated using the adiabatic gas equation from pressure changes inside the model.


RESULTS
A range of Vt (1-10 mL), frequencies (5-15 Hz), pressure amplitudes (10-90 cm H2O), inspiratory times (30% to 50%), and Fio2 (0.21-1.0) was used. Accuracy was determined by using modified Bland-Altman plots (95% limits of agreement). An exponential decrease in Vt was observed with increasing oscillatory frequency. Mean DeltaVt-disp was 0.6 mL (limits of agreement, -1.0 to 2.1) with a linear frequency dependence. Mean DeltaVt-disp was -0.2 mL (limits of agreement, -0.5 to 0.1) with increasing pressure amplitude and -0.2 mL (limits of agreement, -0.3 to -0.1) with increasing inspiratory time. Humidity and heating did not affect error, whereas increasing Fio2 from 0.21 to 1.0 increased mean error by 6.3% (+/-2.5%).


CONCLUSIONS
The Florian infant hot-wire flowmeter and monitoring system provides reliable measurements of Vt at the airway opening during high-frequency oscillatory ventilation when employed at frequencies of 8-13 Hz. The bedside application could improve monitoring of patients receiving high-frequency oscillatory ventilation, favor a better understanding of the physiologic consequences of different high-frequency oscillatory ventilation strategies, and therefore optimize treatment.
Scalfaro
P
P
Pediatric Intensive Care Unit, CHUV University Hospital Lausanne, Switzerland.
Pillow
J J
JJ
Sly
P D
PD
Cotting
J
J
D000403:Airway Resistance / Q000502:physiology; D004867:Equipment Design; D004869:Equipment Safety; D006612:High-Frequency Ventilation / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007231:Infant, Newborn; D008954:Models, Biological; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013990:Tidal Volume; D012122:Ventilators, Mechanical