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Proportional assist ventilation decreases thoracoabdominal asynchrony and chest wall distortion in preterm infants
G Musante1, A Schulze, T Gerhardt
1Department of Pediatrics, Division of Neonatology, University of Miami School of Medicine, Miami, Florida, USA.
Insights
Proportional assist ventilation (PAV) effectively reduces thoracoabdominal asynchrony and chest wall distortion in preterm infants. This breathing support synchronizes with infant effort, improving respiratory mechanics.
Area of Science:
- Neonatal Physiology
- Respiratory Mechanics
- Pediatric Pulmonology
Background:
- Preterm infants often exhibit thoracoabdominal asynchrony (TAA) and chest wall distortion (CWD) due to chest wall immaturity.
- Continuous positive airway pressure (CPAP) is used to stent the chest wall, reducing TAA and CWD.
- A more responsive ventilatory support strategy may offer superior outcomes compared to CPAP alone.
Purpose of the Study:
- To test the hypothesis that proportional assist ventilation (PAV) reduces TAA and CWD in preterm infants.
- To compare the effects of PAV at different support levels against CPAP.
Main Methods:
- Ten preterm infants were studied using respiratory inductive plethysmography to measure TAA and CWD.
- Measurements were taken during alternating periods of CPAP and two levels of PAV (Gain 1 and Gain 2).
- Tidal volume, airway pressure, and esophageal pressure were also monitored.
Main Results:
- PAV significantly reduced TAA (phase angle) and CWD (total compartmental displacement ratio) compared to CPAP.
- Increasing PAV support levels led to greater reductions in TAA and CWD.
- PAV increased tidal volume and chest wall excursion while decreasing abdominal movement, indicating improved respiratory effort distribution.
Conclusions:
- Proportional assist ventilation is effective in reducing TAA and CWD in preterm infants.
- PAV provides ventilatory support in synchrony with and proportional to infant inspiratory effort.
- This synchronized support mechanism improves chest wall mechanics and respiratory efficiency in vulnerable neonates.
Abstract:
Thoracoabdominal asynchrony (TAA) and chest wall distortion (CWD) are commonly seen in preterm infants secondary to a highly compliant rib cage and poor compensation of distorting forces by inspiratory rib cage muscles. Continuous positive airway pressure (CPAP) reduces TAA and CWD by stenting the chest wall. We hypothesized that application of positive airway pressure only during inspiration and in proportion to an infant's inspiratory effort should have a similar but more pronounced effect than CPAP alone. A ventilator providing airway pressure changes in proportion to flow and volume generated by an infant (proportional assist ventilation) was used to unload the respiratory pump during inspiration. Ten preterm infants were studied [birth weight, 745 (635-1175) g; gestational age, 26.5 (24-31) wk; postnatal age 3 (1-7) d; medium (range)]. TAA and CWD were determined by respiratory inductive plethysmography. TAA was expressed as the phase angle between the rib cage and abdominal motion and CWD as the total compartmental displacement ratio. In addition, we measured tidal volume with a pneumotachograph and esophageal and airway pressure deflections with pressure transducers. Measurements were obtained during alternating periods of CPAP and two different degrees of support (Gain 1 = 1.09 +/- 0.68, Gain 2 = 1.84 +/- 0.84 cm H(2)O/mL) that were provided by a proportional assist ventilator. Phase angle and the total compartmental displacement ratio decreased with increasing gain compared with CPAP alone. Peak airway pressure increased from 0.6 to 3.8 to 7.6 cm H(2)O above positive end-expiratory pressure (PEEP) with CPAP, Gain 1, and Gain 2, respectively, as tidal volume increased from 2.8 to 4.1 to 4.7 mL/kg. Esophageal pressure changes decreased only little with increasing gain. Chest wall excursion increased and abdominal movement decreased, indicating a redistribution of tidal volume between chest and abdomen. We conclude that proportional assist ventilation reduces TAA and CWD by generating a small increase in airway pressure that occurs in synchrony and in proportion to each inspiratory effort.