Dead space washout by intentional leakage flow during conventional ventilation of premature infants-an experimental study

Abstract

Objective: Invasive mechanical ventilation poses a strong risk factor for the development of chronic lung disease in preterm infants. A reduction of the dead space as part of the total breathing volume would reduce the ventilation effort and thereby lower the risk of ventilator-induced lung injuries. In this experimental study, we compared the efficacy of mechanical dead space washout via uncontrolled and controlled leakage flow in their ability to eliminate CO₂ during conventional ventilation in preterm infants.

Methods: Three frequently used neonatal ventilators, operating under standard conventional ventilating parameters, were individually connected to a test lung. To maintain a constant physiological end-expiratory pCO₂ level during ventilation, the test lung was continuously flooded with CO₂ . A side port in the area of the connector between the endotracheal tube and the flow sensor allowed breathing gas to escape passively or in a second experimental setup, regulated by a pump. Measurements of end-expiratory pCO₂ were taken in both experiments and compared to end-expiratory pCO₂ levels of ventilation without active dead space leakage.

Results: Following dead space washout, a significant reduction of end-expiratory pCO₂ was attained. Under conditions of uncontrolled leakage, the mean decrease was 14.1% while controlled leakage saw a mean reduction of 16.1%.

Conclusion: Washout of dead space by way of leakage flow is an effective method to reduce end-expiratory pCO₂ . Both controlled and uncontrolled leakage provide comparable results, but precise regulation of leakage allows for a more stable ventilation by preventing uncontrolled loss of tidal volume during inspiration.

Keywords: dead space washout; leakage flow; mechanical ventilation; preterm infant.