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Effects of inspiratory resistive loading on chest wall motion and ventilation: differences between preterm and
K S Deoras1, J S Greenspan, M R Wolfson
1Department of Pediatrics, Temple University School of Medicine, Philadelphia, Pennsylvania.
Insights
Preterm infants have unstable chest walls, limiting their ability to adjust breathing during inspiratory resistive loading compared to full-term infants. This chest wall instability impacts tidal volume and ventilation in preterm infants under respiratory stress.
Area of Science:
- Neonatal Physiology
- Respiratory Mechanics
- Infant Development
Background:
- Effective breathing relies on neural output and respiratory system mechanics.
- Chest wall stability is crucial for maintaining ventilation during breathing challenges.
- Preterm infants may have underdeveloped respiratory systems, including chest wall instability.
Purpose of the Study:
- To investigate if chest wall instability limits preterm infants' response to inspiratory resistive loading (IRL).
- To compare the respiratory responses of preterm (PT) and full-term (FT) infants to IRL.
Main Methods:
- Eight FT and 10 PT infants were subjected to IRL at 1.3, 2, and 6 times intrinsic lung resistance.
- Measurements included tidal volume (VT), minute ventilation (VE), and chest wall motion using respiratory inductive plethysmography.
- Thoracoabdominal asynchrony was quantified by the phase angle (theta) between rib cage and abdominal movements.
Main Results:
- PT infants showed significantly greater baseline chest wall asynchrony (theta = 38 +/- 9 degrees) than FT infants (theta = 9 +/- 3 degrees).
- Under high IRL, VT significantly decreased in PT infants but not FT infants.
- PT infants experienced decreased VE and increased asynchrony (theta = 56 +/- 7 degrees) during IRL, unlike FT infants.
Conclusions:
- Chest wall instability is a significant factor limiting preterm infants' respiratory response to inspiratory resistive loading.
- Preterm infants exhibit greater thoracoabdominal asynchrony, which worsens under respiratory load.
- Findings suggest impaired respiratory mechanics in preterm infants contribute to their reduced ability to cope with breathing challenges.
Abstract:
The ability to maintain effective tidal volume and minute ventilation during resistive loaded breathing depends on both adequate central neural respiratory output response and respiratory system mechanical properties such as respiratory muscle strength and chest wall stability. We hypothesized that chest wall instability limits the ability of the preterm (PT) infant to respond to inspiratory resistive loading (IRL) compared with full-term (FT) infants. To test this hypothesis, we subjected eight FT and 10 PT infants to IRL with loads of 1.3, 2, and 6 times intrinsic lung resistance and measured steady state tidal volume (VT), minute ventilation (VE), and chest wall motion. Thoracoabdominal asynchrony was measured by respiratory inductive plethysmography and quantitated by measuring the phase angle, theta, between rib cage and abdominal motion (0 degrees = synchronous motion, 180 degrees = paradoxic motion). At baseline, VT/kg (mL/kg, mean +/- SEM) was similar between PT (7.0 +/- 0.7) and FT (7.5 +/- 0.5) infants. VE/kg (mL/min/kg) was greater in PT (545 +/- 50) than in FT (385 +/- 33) infants (p < 0.05) as a result of increased respiratory frequency in the former. PT infants demonstrated significantly greater chest wall asynchrony (theta = 38 +/- 9 degrees) than FT infants (theta = 9 +/- 3 degrees) (p < 0.01). With the highest resistive loads, VT decreased significantly in the PT but not the FT infants. Furthermore, during IRL, VE decreased to 417 +/- 50 mL/min/kg (p < 0.05) and theta increased to 56 +/- 7 (p < 0.05) in the PT infants, whereas no significant change in either value was observed in the FT group.(ABSTRACT TRUNCATED AT 250 WORDS)