Negative Tracheal Pressure During Neonatal Endotracheal Suction

Abstract

Endotracheal tube (ETT) suction is the most frequently performed invasive procedure in ventilated newborn infants and is associated with adverse effects related to negative tracheal pressure. We aimed to measure suction catheter gas flow and intratracheal pressure during ETT suction of a test lung and develop a mathematical model to predict tracheal pressure from catheter and ETT dimensions and applied pressure. Tracheal pressure and catheter flow were recorded during suction of ETT sizes 2.5-4.0 mm connected to a test lung with catheters 5-8 French Gauge and applied pressures of 80 -200 mm Hg. The fraction of applied pressure transmitted to the trachea was calculated for each combination, and data fitted to three nonlinear models for analysis. E ndotracheal tube (ETT) suction is the most frequently performed invasive procedure in ventilated newborn infants, and is important to maintain ETT patency and to prevent complications of secretion retention (1,2). It is associated, however, with the potential for significant adverse effects including loss of lung volume, hypoxemia, and localized injury to the tracheobronchial tree (3-11). The cause of these adverse effects may be the exposure of the tracheobronchial tree to negative pressure (5,(12)(13)(14).The chief determinants of intratracheal pressure during suction are thought to be applied suction pressure (P suction ) and catheter size relative to ETT size (14,15). The effect of suction on intratracheal pressure has been evaluated in vitro and in vivo for adult ETT and catheter sizes (16,17), and in vivo studies have examined the effects of P suction and the relationship between ETT and suction catheter size on changes in oxygenation, respiratory mechanics, and cardiovascular dynamics (5,18,19). Although larger catheters and higher P suction are found to generate lower intratracheal pressure than smaller catheters, the exact relationship between these variables has not been determined (16,17,20).In an in vitro lung model, intratracheal pressure was found to be inversely related to the cross-sectional area between the ETT and catheter for neonatal and pediatric ETT sizes during suction (using an applied pressure of 500 mm Hg) (20). However, this relationship was not mathematically defined. Rosen and Hillard (21) derived an equation to quantify intratracheal pressure in terms of ETT and suction catheter dimensions and applied suction pressure, but this equation did not account for the annular shape of the area between the ETT and catheter and has not been verified empirically (15).The aim of this study was, in an in vitro lung model, to measure intratracheal pressure and catheter gas flow (VЈ catheter ) over the range of clinically used P suction for neonatal ETTs and suction catheters. In addition, we aimed to develop a mathematical model to define the relationship between the intratracheal pressure generated during suction and ETT size, suction catheter size, and P suction . MATERIALS AND METHODSEthical approval is not required for bench-top experiments...

The Effect of Suction Method, Catheter Size, and Suction Pressure on Lung Volume Changes During Endotracheal Suction in Piglets

“…regardless of catheter size (25)(26)(27)36). Our findings support our previous contention that catheter size and suction pressure should be considered in relation to each other (15). With open suction, lung volume changes were unaffected by catheter size or suction pressure.…”

“…With open suction, lung volume changes were unaffected by catheter size or suction pressure. This finding is consistent with a study of oxygenation and hemodynamic changes with suction in ventilated children (4) but is somewhat surprising in light of in vitro studies (15,17). In contrast, in another pediatric study catheter size was implicated in reduction in dynamic compliance after suction (19).…”

“…Larger catheters, that occlude more of the ETT lumen, have been shown in vitro to generate high negative airway pressures during both open and closed suction (15)(16)(17). In adults, it is recommended that the diameter of the suction catheter should be less than half that of the ETT (35).…”

“…At least in vitro, suction catheter size and suction pressure have been implicated in determining tracheal pressure during suction (15)(16)(17), the presumed precursor to volume loss. Whether tracheal pressure changes result in clinically observable effects is unclear (4,18 -20) and there is no consensus on appropriate catheter sizes or suction pressures for clinical use in children or neonates (21)(22)(23)(24)(25)(26)(27).…”

Paediatric lung recruitment: a review of the clinical evidence

“…51 However a number of studies have cautioned clinicians about negative pressures associated with the use of closed suction units and a reduction in secretion clearance particularly in paediatrics. [52][53][54] Consequently, the use of closed suction systems, at least in the paediatric population, remains questionable. In addition, saline instillation exacerbates gas maldistribution and worsens de-recruitment by increasing threshold opening pressures.…”