1998 OPEN FORUM Abstracts
THE EFFECT OF THE VENTILATOR CIRCUIT ON THE SV 300 DELIVERY OF PRESSURE-CONTROLLED VENTILATION FOR THE PEDIATRIC RANGE
Katie Kinninger RCP, Wayne Johnson RCP, Elzbieta Bak MS, John Newhart RCP, Rick Ford RCP, David Burns MD UCSD Medical Center, San Diego, California
BACKROUND: At the onset of inspiration during clinical use of the Servo Ventilator 300 (SV 300) (Siemens-Elema AB, Solna, Sweden) with pressure-controlled ventilation selected for the pediatric range, we observed a rapid inspiratory flow resulting in an airway pressure overshoot "spike". The presence of overshoot has no clinical significance, because it is not transmitted to the alveolar level. It can, however, cause the microprocessor controls of the ventilator to detect upper pressure limits and unnecessarily activate alarm limits of the system and cause the loss of delivered inspiratory tidal volume. The overshoot could be eliminated by selecting the adult range or by replacing the pediatric (15mm diameter) disposable ventilator circuit with a reusable neonatal (10mm diameter) circuit. The objective of this study was to document the effect of different pediatric and neonatal ventilator circuits on the SV 300 delivery of pressure controlled ventilation in pediatric and adult ranges. Methods: Utilizing these previously observed clinical conditions, a bench test was performed on a single-compartment lung model with seven commercial ventilator circuit brands: Siemens #6697023 silicon circuit (SV), Simplex #N2723 Tygon circuit (SS), Marquest #1555203 Tygon circuit (MS), Simplex #P3945 heated wire circuit (SHW), Marquest #156545 heated wire circuit (MHW), Hudson #780-24 heated wire circuit (HHW), and Hudson #780-22 circuit with a water trap (HWT). The SV, SS and MS are neonatal, smooth-bore circuits with an internal diameter (I.D.) of 10 mm while SHW, MHW, HHW and HWT are corrugated pediatric circuits with I.D. of 15mm. The pressure and flow transducers were inserted between the inspiratory outlet of the SV 300 and the proximal end of the inspiratory limb of the tested ventilator circuit. The following parameters were measured: peak inspiratory flow (PIF), volume delivered during inspiration (Vi) to the TTL lung model system including volume in the ventilator circuit, and the PEEP level. The overshoot pressure (Pov) was defined as the difference between the peak inspiratory pressure (pressure at the peak of the spike) and the plateau pressure (pressure at the inspiratory plateau, before the point of flow reversal that begins expiration).
Results: Vi (L) PIF (L/s) Pov PEEP
CIRCUIT Ped Adu Ped Adu Ped Adu Ped Adu
SV .247 .237 .432 .397 1.9 0.7 5.1 6.9
SS .244 .237 .427 .392 1.8 0.8 4.8 6.2
MS .238 .230 .442 .407 2.0 0.9 5.3 6.3
SHW .272 .257 .513 .462 2.3 0.6 4.3 6.1
MHW .276 .256 .553 .487 3.0 0.6 4.1 6.4
HHW .284 .268 .586 .503 3.0 0.0 4.4 6.3
HWT .296 .277 .608 .543 3.5 0.9 4.3 6.6
Conclusions: The diameter size of the ventilator circuit can have clinically significant influence on the characteristics of the pressure controlled ventilation mode in the pediatric range delivered by the SV 300 ventilator. Potential clinical problems can be avoided by monitoring pressure and flow waveforms.
The 44th International Respiratory Congress Abstracts-On-Disk®, November 7 - 10, 1998, Atlanta, Georgia.