The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

EVALUATION OF THE SENSORMEDICS 3100a AND 3100b VENTILATORS USING HOT-WIRE ANEMOMETRY

Tom Blackson, BS, RRT1, 3,Tim Cox, BS, RRT2, Karen Jensen, RRT1, Thomas H.Shaffer PhD4 1Christiana Care Health System, 2duPont Hospital for Children, 3Delaware Technical and Community College, Wilmington Campus, DE., 4Lung Center, AI duPont Hospital for Children, Wilm. DE

Background: High Frequency Oscillatory Ventilation (HFOV) uses very small lung tidal volumes, oscillated by piston action around a set mean airway pressure, to accomplish oxygenation and ventilation in patients with acute lung injury. Currently, there are two FDA approved devices in the US that provide HFOV, the SensorMedics 3100A and 3100B (Viasys Healthcare, Yorba Linda, Ca.). The 3100A is indicated for ventilatory support of patients < 35kg while the 3100B is indicated for patients > 35 kg. Clinical experience with the 3100A reveals a sub-population of acutely ill patients for whom the 3100A can not accomplish effective ventilation. Clinicians have speculated that use of the 3100B under these circumstances may provide safe and effective ventilation while allowing continuation of a high frequency ventilatory strategy.

Purpose: To compare the ventilation performance characteristics of the 3100A and 3100B ventilators on a test lung model using hot-wire anemometry (HW).

Materials/Methods: In vitro studies were conducted using the SensorMedics 3100A and 3100B to ventilate a Michigan test lung: C= 0.001 L/cm H2O; R= 3.0 mm ID ETT. Both ventilators were assembled and calibrated according to manufacturer's recommendations. Tidal volume (VT), frequency (f), carbon dioxide elimination coefficient (VT2 x f), mean airway pressure (PAW), and peak inspiratory pressure (PIP), were measured using a hot wire anemometer, (Acutronic Medical Systems), over HFOV settings: (f;5 - 15 Hz), pressure amplitudes (P;10 - 90 cm H2O), inspiratory time (TI; 33 ), mean airway pressure of 25 cm H2O, bias flow rate of 20 L/min., and 60% oxygen.

Results: The 3100B delivered significantly less VT and VT2 x f than the 3100A at P settings greater that 30 cm H2O, (*p < 0.05). The 3100A delivered significantly greater PIP than the 3100B at P settings greater than 40 cm H2O, (*p < 0.05). The Paw measured from the 3100A varied significantly from the 3100A digital display of P at f = 15 Hz and P display greater than 50 cm H2O.

Carbon Dioxide Elimination Coefficient (mL2*Hz) *p < 0.05

  3100A 3100B
P (cmH2O) 5 Hz 10 Hz 15 Hz 5 Hz 10 Hz 15 Hz
10 47.8 0.8 5.0 47.5 3.0 5.1
20 130.4 3.5 18.7 121.3 35.2 17.6
30 258.1 35.1 58.8 225.6 73.1 32.8
40 523.2 161.5 127.3 369.9* 142.5* 71.2*
50 858.9 299.9 224.3 577.3* 227.3* 133.7*
60 1238.1 524.1 355.4 815.2* 374.4* 222.7*
70 1705.7 830.1 521.6 1133.3* 503.7* 330.6*
80 2108.5 1048.7 638.7 1533.7* 695.9* 463.4*
90 2362.9 1251.9 750.7 1994.0* 939.1* 615.1*

Conclusions: The 3100A and 3100B ventilators produced significantly different levels of ventilation despite identical settings and monitoring displays when ventilating this test lung model.

Clinical Implications:
Clinicians should use extreme caution when considering use of the 3100B for patients in whom the 3100A has demonstrated ineffective ventilation. Clinical use of both the 3100A and the 3100B ventilators may benefit from more objective monitoring of delivered pressures and volumes.

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