2004 OPEN FORUM Abstracts
Effect of closed circuit suctioning on airway pressures and portable ventilator performance.
D. Branson, MS, RRT, Jay A. Johannigman MD. University of
Cincinnati, 231 Albert Sabin Way; Cincinnati, OH 45267-0558)
Background: The use of closed circuit suctioning (CSS) has become routine in hospitals and is now more frequently being used in home care. We evaluated the response of portable ventilators to CCS in a lung model. We hypothesized that the type of ventilator gas delivery system (piston, turbine, compressor) and mode of ventilation might effect ventilator response.
Method: Eight portable ventilators were studied: Pulmonetics LTV-1000 and LTV-800; Puritan Bennett Acheiva and LP-10, Impact Eagle 754 and 750; Viasys Tbird; and Newport HT-50. We connected each ventilator to a lung model (TTL, Michigan Instruments) using standard circuits. A CSS catheter (Ballard, 14 Fr) was placed between the circuit and lung model. Airway pressure, volume, flow, and oxygen concentration were measured continuously. Suctioning was applied for 15 secs using -120 mmHg and maximum (unregulated) suction. Data was collected 60 secs before CSS, during CSS, and for 60 secs after CSS. Ventilators were operated in Volume control CMV, Pressure control CMV, and in 4 ventilators PSV. PEEP of 0 and 10 cm H2O was used at each condition and VT was varied from 200 to 1000 mL. During PSV and PCV pressure limit was set at 20 cm H2O above PEEP. Respiratory rate was set at 10 breaths/min.
Results: Actuation of CSS resulted in auto-triggering during VCV. Respiratory rate increased from 12 to 28±6 breaths/min (p<0.05). PEEP decreased from 10 cm H2O to 4± 3.3 cm H2O with unregulated suction. Unregulated suctioning was associated with the greatest decrease in PEEP. (p< 0.01). FIO2 was stable in all ventilators except Impact 750 and LP-10. In both cases, during VCV, CSS resulted in drawing room air through anti-asphyxia valves and decreasing FIO2 from 1.0 to 0.72±0.14. (p<0.01) The lower the VT the greater the reduction in FIO2.PCV was associated with a lower change in peak airway pressure compared to VCV. No ventilator failed and all ventilators resumed normal function within 6 breaths of terminating CSS. Flow through the suction catheter was 32 L/min at -120 mm Hg suction and 44 L/min at unregulated suction. The degree of reduction in peak pressure was greatest with low VT and low set inspiratory flow (ratio of suction flow to set flow) during VCV.
Conclusion: During CSS portable ventilator operation is affected. All tested ventilators maintained operation and retuned to normal operation within 6 breaths of ceasing CSS. PEEP fell significantly during CSS with the greatest changes during VCV at low VT and unregulated suction. FIO2 can decrease during VCV in certain ventilators.