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Influence of increasing postnatal age on respiratory timing and reflex activity in preterm ventilated infants
1Dept. of Child Health, King's College Hospital, London, U.K.
Insights
Postnatal age does not significantly alter respiratory timing or the Hering Breuer reflex in ventilated infants receiving continuous positive airway pressure (CPAP). These findings impact optimal ventilation strategies for neonates with respiratory distress syndrome.
Area of Science:
- Neonatal Physiology
- Respiratory Medicine
- Pediatric Critical Care
Background:
- Infants with respiratory distress syndrome often require mechanical ventilation and continuous positive airway pressure (CPAP).
- Understanding respiratory control and reflexes, such as the Hering Breuer reflex, is crucial for optimizing ventilation in neonates.
- The influence of postnatal development on these parameters remains an area of investigation.
Purpose of the Study:
- To investigate the impact of postnatal age on spontaneous respiratory timing and the Hering Breuer reflex in ventilated infants.
- To determine if respiratory timings and reflex activity change during the early neonatal period.
- To inform optimal mechanical ventilation strategies for neonates.
Main Methods:
- Studied 53 ventilated infants (median gestational age 29 weeks) on 119 occasions.
- Measured inspiratory and expiratory times during brief disconnections from ventilation and during 3 cmH2O CPAP.
- Defined Hering Breuer reflex by >10% prolongation of inspiratory/expiratory time on CPAP versus disconnection.
Main Results:
- No significant changes in respiratory timing were observed between postnatal days 1-5 and weeks 1-4.
- Inspiratory and expiratory times were generally longer on CPAP, reaching significance in the first two days and weeks.
- The Hering Breuer reflex occurred in a similar proportion of infants regardless of postnatal age.
Conclusions:
- Postnatal age does not influence respiratory timing or Hering Breuer reflex activity in ventilated neonates with spontaneous respiratory efforts.
- These findings suggest that current ventilation rates may not need adjustment based on postnatal age in this population.
- Further research may refine ventilation strategies for neonates requiring respiratory support.
Abstract:
The influence of postnatal age on spontaneous respiratory time, measured both on and off continuous positive airways pressure (CPAP), and the occurrence of the Hering Breuer reflex has been investigated. Consecutive ventilated infants were recruited and only studied when making respiratory efforts during mechanical ventilation. Fifty-three infants were studied on 119 occasions, their median gestational age was 29 weeks and birthweight 1142 gms. All the infants were initially ventilated for the respiratory distress syndrome. Inspiratory and expiratory times were measured from simultaneous flow and oesophageal pressure recordings during a 20-second period of disconnection and during a similar period on 3 cmH2O CPAP. Prolongation of the inspiratory and expiratory time on CPAP compared to that measured during disconnection of more than 10% was evidence of the Hering Breuer reflex. No significant change in the inspiratory or expiratory time either on or off CPAP was noted either between days 1 to 5 or weeks 1 to 4. Both inspiratory and expiratory time tended to be longer on CPAP than during disconnection and these differences reached significance on days 1 and 2 and weeks 1 and 2. No influence of postnatal age was demonstrated on the proportion of infants in whom the Hering Breuer reflex was demonstrated. Our results suggest that, during the neonatal period, there is no influence of postnatal age on respiratory timings or reflex activity amongst ventilated infants who make spontaneous respiratory efforts during ventilation. These results have important implications regarding the optimum rate at which such infants should be ventilated.