Effects of duty cycle and positive end-expiratory pressure on mucus clearance during mechanical ventilation*

Abstract

In the semirecumbent position, mucus clearance is improved with prolongation of the duty cycle. However, in clinical practice, positive findings must be balanced against the potentially adverse hemodynamic and respiratory effects.

Effects of Manual Rib Cage Compressions on Expiratory Flow and Mucus Clearance During Mechanical Ventilation*

“…The study was conducted in animals undergoing a concomitant 4-day study to assess the effects of ventilatory settings on mucus clearance (10). During the concurrent study, 8-hr experiments were conducted on a daily basis and it always commenced prior to this study.…”

“…Inspiratory gases were conditioned through a heated humidifier. Internal endotracheal tube cuff pressure was maintained at 28 cm H 2 O. Midazolam and fentanyl were administered as previously reported (10). Boluses of 50 mg of intravenous sodium thiopental were administered as needed.…”

“…Pigs were paralyzed with a loading (0.6 mg/kg) and maintenance (0.4-0.6 mg/kg/h) dose of vecuronium. We surgically cannulated the femoral artery for systemic arterial pressure monitoring and collection of blood samples (10). Pulmonary artery catheterization was used to measure pulmonary artery, central venous, pulmonary artery occlusion pressures and cardiac output (CO).…”

“…The use of these techniques is supported by laboratory evidence that mucus clearance is enhanced when expiratory flow exceeds inspiratory flow (6)(7)(8)(9)(10)(11).…”

Effect of Inspiratory Time and Lung Compliance on Flow Bias Generated During Manual Hyperinflation: A Bench Study

“…In particular, the threshold of MIF Ϫ MEF Ͻ Ϫ7.9 L/min is based on the delivery of mechanical ventilation in intubated swine for 30 min at flows much lower than those achieved during the shorter applications of manual hyperinflation. 20 …”