The Effects of Closed Endotracheal Suction on Ventilation During Conventional and High-Frequency Oscillatory Ventilation

Abstract

ABSTRACT:In newborn infants, closed endotracheal tube (ETT) suction may reduce associated adverse effects, but it is not clear whether ventilation is maintained during the procedure. We aimed to determine the effect of ETT size, catheter size, and suction pressure on ventilation parameters measured distal to the ETT. Suction was performed on a test lung, ventilated with conventional (CMV) and high-frequency oscillatory ventilation (HFOV) using ETT sizes 2.5-4.0 mm, catheter sizes 5-8 French gauge (Fr), and suction pressures 80 -200 mm Hg. Tracheal and circuit peak inspiratory pressure, positive end-expiratory pressure, and tracheal tidal volume (V T ) were recorded for each suction episode. During both CMV and HFOV, tracheal pressures and V T were considerably reduced by suctioning; this reduction was dependent on the combination of ETT, catheter, and suction pressure. Loss of V T , inflation pressure (CMV), and pressure amplitude (HFOV) occurred primarily with insertion of the catheter, and loss of end-expiratory pressure (CMV) and mean tracheal pressure (HFOV) occurred with the application of suction. Circuit pressures were reduced to lesser degree. We conclude that airway pressures and V T are not maintained during closed endotracheal suction with either CMV or HFOV, and choice of equipment and settings will affect the degree of interruption to ventilation. (Pediatr Res 66: 400-404, 2009) E ndotracheal tube (ETT) suction is performed periodically on infants receiving mechanical ventilation to clear secretions from the ETT and airway. Although necessary, it is associated with adverse effects including atelectasis, hypoxemia, and cardiovascular instability, partly attributable to loss of airway pressure and interruption of ventilation (1-5). Closed suction, performed without disconnection from respiratory support, has been shown to reduce adverse effects (6 -8), but whether ventilation is maintained during closed suction has not been demonstrated in a neonatal population.With adult-sized ETTs, airway pressure has been shown to decrease during closed suction and concerns have been raised about the potential for very large negative airway pressures during the procedure (4,9,10). However only one study has quantified pressure and tidal volume (V T ) changes during closed suction with neonatal equipment (11). Using an in vitro model, a considerable reduction in airway pressures and V T was demonstrated, particularly when a large catheter relative to the ETT was used. However, the authors did not report results using 5 or 7 French gauge (Fr) suction catheters, nor did they measure the effect of varying the suction pressure.Airway pressures during closed suction are influenced by ventilation mode in adult models (4,10), but this effect has not been studied using neonatal ventilators. Of particular interest is the performance of closed suction catheters during highfrequency oscillatory ventilation (HFOV), because closed suction is generally recommended for patients receiving this ventilation mode (12,13).This study ai...

Endotracheal Suctioning Is Basic Intensive Care or Is it?: Commentary on article by Copnell et al. on page 405

“…In both this article (28) and previous studies from the same group (21,29), it was notable that, when using the two smaller catheters (6 and 7FG) at the highest pressure, volume loss was less than or similar to that generated by an 8-FG catheter at the lowest pressure. Thus, recommendations for suctioning need to address both catheter size and suctioning pressure.…”

“…Those data were expanded with some studies considering lung mechanics after endotracheal suctioning (19,20). Some elegant theoretical (20,21) and practical studies followed, which highlighted the complexity of flows within suction catheters and endotracheal tubes during endotracheal suction.…”

Pediatric Airway Maintenance and Clearance in the Acute Care Setting: How To Stay Out of Trouble

“…A smaller catheter provides more protection to the patient than does a lower suction pressure. 52,53 Catheter size is, unfortunately, not reported in all studies. In a small study of 17 infants, a catheter-to-ETT diameter ratio of 0.7 proved most effective without increasing the incidence of adverse outcomes.…”

“…56 This may be explained by the probable presence of turbulent flow between the ETT and suction catheter during closed suctioning. 52 The concept that closed suctioning is better because it prevents volume loss may be incorrect. As soon as the catheter is inserted into the airway, lungvolume loss begins.…”

Volume Not Guaranteed: Closed Endotracheal Suction Compromises Ventilation in Volume-Targeted Mode

“…Another study found overshoot in tidal volume using TTV mode after a rapid decrease in airway resistance, a change which occurs when suctioning ends [4] . We previously found that airway pressure distal to the ETT can become considerably negative (while circuit pressure remains unaffected) during closed suction with time-cycled, pressure-limited ventilation, but no published neonatal study to date has investigated the effect of ETT suction on ventilation in a TTV mode [5] .…”