Respiratory Support in Meconium Aspiration Syndrome: A Practical Guide

Abstract

Meconium aspiration syndrome (MAS) is a complex respiratory disease of the term and near-term neonate. Inhalation of meconium causes airway obstruction, atelectasis, epithelial injury, surfactant inhibition, and pulmonary hypertension, the chief clinical manifestations of which are hypoxaemia and poor lung compliance. Supplemental oxygen is the mainstay of therapy for MAS, with around one-third of infants requiring intubation and mechanical ventilation. For those ventilated, high ventilator pressures, as well as a relatively long inspiratory time and slow ventilator rate, may be necessary to achieve adequate oxygenation. High-frequency ventilation may offer a benefit in infants with refractory hypoxaemia and/or gas trapping. Inhaled nitric oxide is effective in those with pulmonary hypertension, and other adjunctive therapies, including surfactant administration and lung lavage, should be considered in selected cases. With judicious use of available modes of ventilation and adjunctive therapies, infants with even the most severe MAS can usually be supported through the disease, with an acceptably low risk of short- and long-term morbidities.

Meconium aspiration syndrome: challenges and solutions

“…If there is obvious gas trapping, PEEP should be decreased (3-4 cm) with optimal expiratory time (0.5-0.7) and rapid ventilator rates. 54 In infants with associated PPHN, higher rates (50-70) with higher FiO 2 (80%-100%) should be considered to maintain PaO 2 between 70 and 100 mm Hg and PaCO 2 between 35 and 45 mm Hg along with volume expansion, vasopressors, and other supportive measures. 53,54 Hyperventilation-induced alkalosis should be avoided due to risk of cerebral vasoconstriction-induced neurologic injury and sensorineural hearing loss.…”

“…55 High frequency oscillatory ventilation is the more commonly used mode, especially in those with significant atelectasis, where application of higher mean airway pressures (around 25 cm) with recruitment maneuvers at moderate frequency (6-8 Hz) has been found to be beneficial. 54 It also lends a clinical advantage in MAS with associated severe PPHN, as the response to inhaled NO is better with HFOV than conventional ventilation, with recent evidence suggesting failure of this combination and requirement of ECMO in only 5% of such babies. 54 High frequency jet ventilation has also been found to be beneficial in optimizing oxygenation and prevention of ECMO in severe MAS especially with an underlying combination of atelectasis and gas trapping.…”

“…54 It also lends a clinical advantage in MAS with associated severe PPHN, as the response to inhaled NO is better with HFOV than conventional ventilation, with recent evidence suggesting failure of this combination and requirement of ECMO in only 5% of such babies. 54 High frequency jet ventilation has also been found to be beneficial in optimizing oxygenation and prevention of ECMO in severe MAS especially with an underlying combination of atelectasis and gas trapping. 56 Hence, high-frequency ventilation should be considered over conventional pneumothorax in settings of severe MAS with intractable hypoxemia, persistent respiratory acidosis, or high risk of pneumothorax.…”

Effects on Lung Function of Small-Volume Conventional Ventilation and High-Frequency Oscillatory Ventilation in a Model of Meconium Aspiration Syndrome

“…Approximately one-third of all infants with diagnosis of MAS require intubation and mechanical ventilation. Indications for intubation of infants with MAS include (a) high oxygen requirement (FiO 2 > 0.8), (b) respiratory acidosis with arterial pH persistently less than 7.25, (c) pulmonary hypertension, and (d) circulatory compromise with poor systemic blood pressure and perfusion (Dargaville 2012).…”

High-Frequency Oscillatory Ventilation with Low Oscillatory Frequency in Pulmonary Interstitial Emphysema

“…It is possible that a lower frequency (5-6 Hz) would more closely replicate the longer expiratory time of HFJV, and thus encourage interstitial gas resorption. Use of lower oscillatory frequencies certainly appears to reduce gas trapping in term infants with meconium aspiration managed on HFOV [9,16]. …”