Pressure changes during tracheal suctioning--a laboratory study

Suctioning is essential in managing tracheal tubes, but also has drawbacks. Using a bench model, we demonstrated the extent and time course of pressure changes during suctioning, examined their relationship with tracheal tube and catheter diameters and assessed the effects of artificial 'sputum' and of compensatory gas flow in the system. We suctioned at -20 kPa (-150 mmHg) and -80 kPa (-600 mmHg) using three different sized catheters and a 5.9-mm diameter bronchoscope through tracheal tubes ranging from 6.5 mm to 9.0 mm in diameter. Pressure changes ranged from -0.1 kPa (-0.8 mmHg) to -20.4 kPa (-153.0 mmHg). We demonstrated more negative pressures with decreasing tracheal tube diameter (p = 0.024) and increasing catheter diameter (p = 0.038). Addition of artificial 'sputum' led to more negative, but unpredictable, pressures than those seen with clean tubes (p = 0.012). Bronchoscopic suctioning produced pressure changes even greater than the largest suction catheter (p = 0.0039). Using a closed system with continuous positive airway pressure and 155 l.min(-1) compensatory gas flow attenuated the pressure changes generated both with a 4.0-mm catheter (p = 0.0005) and on bronchoscopic suctioning (p = 0.0078). The time taken to reach 50% of minimum pressure was always less than 1 s. The use of high compensatory flows during suctioning merits clinical evaluation.