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Diaphragmatic work of breathing in premature human infants
Insights
New methods assess infant diaphragmatic work during rib cage distortion. Increased work and caloric cost in preterm infants may lead to diaphragm fatigue and growth failure.
Area of Science:
- Neonatal physiology
- Respiratory mechanics
Background:
- Current methods for assessing infant work of breathing do not account for increased loads during rib cage distortion.
- Loss of intercostal muscle activity contributes to abnormal breathing patterns in infants.
Purpose of the Study:
- To develop and validate a new technique for assessing diaphragmatic work in preterm infants experiencing rib cage distortion.
- To quantify the increased diaphragmatic work and energy expenditure associated with paradoxical rib cage motion.
Main Methods:
- Measurements of transdiaphragmatic pressure and abdominal volume displacement were used to assess diaphragmatic work.
- The study included eleven preterm infants without evidence of lung disease.
- Diaphragmatic electrical activity was measured using its moving time average.
Main Results:
- Inspiratory diaphragmatic work increased significantly during periods of paradoxical rib cage motion (12.4 g x cm x ml-1) compared to minimal distortion (5.9 g x cm x ml-1).
- Inspiratory work strongly correlated with the electrical activity of the diaphragm.
- The caloric cost of diaphragmatic work could reach 10% of basal metabolic rate during rib cage distortion.
Conclusions:
- The developed technique effectively assesses diaphragmatic work during altered respiratory mechanics in preterm infants.
- Increased diaphragmatic work and metabolic demand in preterm infants with rib cage distortion may contribute to diaphragm fatigue and impaired growth.
- These findings highlight the importance of considering respiratory mechanics when evaluating the energy expenditure of preterm infants.
Abstract:
Present methods of assessing the work of breathing in human infants do not account for the added load when intercostal muscle activity is lost and rib cage distortion occurs. We have developed a technique for assessing diaphragmatic work in this circumstance utilizing measurements of transdiaphragmatic pressure and abdominal volume displacement. Eleven preterm infants without evidence of lung disease were studied. During periods of minimal rib cage distortion, inspiratory diaphragmatic work averaged 5.9 g X cm X ml-1, increasing to an average of 12.4 g X cm X ml-1 with periods of paradoxical rib cage motion (P less than 0.01). Inspiratory work was strongly correlated with the electrical activity of the diaphragm as measured from its moving time average (P less than 0.05). Assuming a mechanical efficiency of 4% in these infants, the caloric cost of diaphragmatic work may reach 10% of their basal metabolic rate in periods with rib cage distortion. When lung disease is superimposed, the increased metabolic demands of the diaphragm may predispose preterm infants to fatigue and may contribute to a failure to grow.