2003 OPEN FORUM Abstracts
Inline suctioning during mechanical ventilation
Ashraf El Masry, M.D., Purris Williams, RRT, Daniel Chipman RRT, Joseph Kratohvil RRT, Robert M.Kacmarek,Ph.D., RRT. Departments of Anesthesia and Critical care, and Respiratory Care, Massachusetts General Hospital and Harvard Medical School.
Background and significance: Closed suctioning systems are increasingly used to avoid the lung volume loss, impairment of gas exchange and environmental contamination associated with open suction. However, generation of negative pressure during suctioning may affect mechanical ventilator performance with subsequent alterations of airway pressures and lung volumes.
Methods: Eleven different ICU mechanical ventilators were evaluated during PA/C, VA/C, CPAP and PS while performing closed suctioning for 15 sec using 2 different suctioning pressures, -120 mm Hg and ≈ -200 mm Hg. A dual chamber lung model (TTL) was used to simulate the respiratory system. Pressure and flow at the Y (airway) were recorded 10 sec before, during 15 sec of continuous suctioning and for 30 sec after cessation of suctioning. During PA/C and VA/C two combinations of settings were evaluated, VT 900 ml, PEEP 5 cm H2O, RR 12/min and lung compliance 60 ml/cm H2O and VT 450 ml, PEEP 10 cm H2O, RR 20/min and lung compliance 30 ml/cm H2O. All ventilators also were tested during CPAP (10 cm H2O) and PS (10 cmH2O with 5 cm H2O PEEP) at a rate of 20/min and compliance 60ml/cm H2O. Data were analyzed using one-way ANOVA and a P value < 0.05 was considered significant.
RESULTS: The response to closed suction varied among ventilators, mode and suction pressure (P<0.05). However, none of the ventilators tested malfunctioned regardless of mode or suction pressure. All ventilators were able to provide gas delivery during suctioning and resumed pre-suction gas delivery patterns within 1-2 breaths after cessation of suction. Flow, and end expiratory pressures delivered from ventilators varied considerably depending on mode and suction pressure (P<0.05). During PA/C and VA/C all ventilators experienced an increase in RR, but few ventilators changed their rate with PS and CPAP.
CONCLUSION: Closed suctioning does not cause mechanical ventilator malfunction, however alteration of gas delivery patterns can occur during suctioning depending on mode of ventilation and suctioning pressure. In relationship to end expiratory pressure change the Siemens Servo 300, Siemens Servo I, Drager Evita 4, and Respironics Espirit performed best.
Table 1: Summary of Peak inspiratory and end expiratory pressures with each ventilator during inline suctioning.
All values are in cm H2O