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Prolonged expiratory duration with elevated lung volume in newborn infants
Insights
Continuous negative pressure ventilation improved lung volume in both full-term and premature infants. This method also regulated respiratory rate and prolonged exhalation duration, suggesting potential benefits for infant respiration.
Area of Science:
- Neonatal Physiology
- Respiratory Medicine
Background:
- Infant respiratory distress syndrome (IRDS) is a common condition.
- Understanding the regulation of breathing in infants is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the effects of continuous negative extrathoracic pressure (CNEP) on lung volumes and respiratory timing in full-term and premature infants.
- To explore the role of vagal feedback in respiratory control during CNEP.
Main Methods:
- Application of 5-7 cm H2O continuous negative pressure (CNEP) around the thorax.
- Measurement of end-expiratory lung volume, respiratory rate, inspiratory duration (Ti), and expiratory duration (Te).
- Analysis of respiratory parameters in both full-term and premature infants.
Main Results:
- CNEP increased end-expiratory lung volume in both groups (17.5 ml in full-term, 7.7 ml in premature infants).
- Respiratory rate decreased significantly in full-term infants (52 to 43 min-1).
- Expiratory duration (Te) increased in full-term infants and in some premature infants, suggesting altered respiratory control.
Conclusions:
- Continuous negative extrathoracic pressure can improve lung volumes and alter respiratory timing in infants.
- Phasic vagal feedback appears to regulate inspiratory duration (Ti), while tonic vagal activity controls expiratory duration (Te).
- Premature infants may benefit from optimized functional residual capacity (FRC) achieved through continuous distending pressure for respiratory regularization.
Unlabelled:
End-expiratory lung volume increased 17.5 +/- 5.4 ml (mean +/- SD) in full term infants and 7.7 +/- 2.1 ml in premature infants when 5--7 cm H2O continuous negative pressure (CNEG) was applied around the thorax. In the full term infants, respiratory rate decreased from 52--43 min-1 (P less than 0.001), mean inspiratory duration (ti) was unchanged, and mean duration of expiration (te) increased from 0.62 +/- 0.14 (SE)-0.84 +/- 0.22 sec (P less than 0.001) after application of CNEG. Te of occluded efforts on CNEG was also prolonged (P less than 0.005), although less than te of spontaneous breaths on CNEG (P less than 0.005). Te increased in four of eight premature infants when CNEG was applied. We conclude that phasic vagal feedback regulates Ti and te is controlled by tonic vagal activity.
Speculation:
Premature infants may have an optimum functional residual capacity (FRC) which can be achieved with continuous distending pressure, resulting in regularization of respiration.