The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

THE EFFECT OF AN INLINE SUCTION CATHETER ON PRESSURE DELIVERY DURING HIGH FREQUENCY OSCILLATORY VENTILATION (HFOV).



Dennis Gaudet, RRT; Matthew P. Branconnier, RRT; Dean R. Hess, PhD RRT, FAARC. Massachusetts General Hospital and Harvard Medical School, Boston MA.

Background: It is commonly accepted that, during HFOV, it is important to maintain the circuit between the ventilator and the patient with minimal bends or angles to avoid interference with pressure transmission. This has led some hospitals to exclude the use of inline suction catheters for patients receiving HFOV. This practice potentially leads to a less than optimal frequency of endotracheal suctioning as disconnecting the patient from HFOV for open suctioning may contribute to alveolar derecruitment and patient decompensation.

Hypothesis: Pressure delivery by HFOV is not affected by the presence of inline suction catheters.

Method:
A calibrated Sensormedics 3100A (SensorMedics, Yorba Linda CA) with a flexiblecircuit was connected to a cuffless endotracheal tube (Mallincrodt), the distal end of which was attached to a pressure sensor and Michigan Instruments neonatal test lung in a leak-free manner. All combinations of the following variables were evaluated: endotracheal tubes with internal diameters of 2.5, 3.0, 3.5 mm; Ballard 6 French inline suction catheters with a 45o (Y) or 90o (elbow) angle, or no catheter in line; mean airway pressure of 10 and 20 cm H2O; amplitude of 20, 25, 30, and 35 cm H2O; frequencies of 10, 12, and 14 Hz. Data acquisition software (Analysis Plus) was used to record pressure at 100 Hz from the distal endotracheal tube (Novametrix NICO). For each set of variables, mean airway pressure and pressure amplitude were measured at the distal endotracheal tube; 10 representative breaths were analyzed.

Results: Data are tabulated below for HFOV settings of mean airway pressure 20 cm H2O, amplitude 25 cm H2O, frequency 12 Hz. A similar pattern of results occurred for other ventilator settings. Note that even statistically significant differences a too small to be considered clinically important.

  Endotracheal tube size No inline catheter 90o angle catheter 45o angle catheter P-value
Mean airway pressure at distal endotracheal tube (cm H2O) 2.5 19.4 ± 0.1 19.5 ± 0.1 19.0 ± 0.1 0.001
3.0 19.4 ± 0.3 19.8 ± 1.0 19.3 ± 0.9 0.294
3.5 19.4 ± 0.3 19.6 ± 0.3 19.6 ± 0.3 0.166
Amplitude at distal endotracheal tube (cm H2O) 2.5 6.0 ± 0.4 5.7 ± 0.4 5.6 ± 0.3 0.059
3.0 9.6 ± 0.3 8.9 ± 0.4 8.7 ± 0.4 0.001
3.5 12.2 ± 0.3 11.8 ± 0.2 12.2 ± 0.4 0.015

Conclusions: The effects of inline suction catheter placement with the HFOV circuit are small and unlikely to adversely affect pressure transmission during HFOV. Further work should focus on the potential patient benefit for the use of inline suction in neonates receiving HFOV.

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