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Ventilatory response to added dead space and position in preterm infants at high risk age for SIDS
Tolulope Saiki1, Simon Hannam, Gerrard F Rafferty
1Division of Asthma, Allergy and Lung Biology, MRC-Asthma Centre, King's College London, London, United Kingdom.
Insights
Premature infants show a slower response to breathing challenges when in the prone position, increasing their risk for Sudden Infant Death Syndrome (SIDS). This impaired response is linked to their postmenstrual age (PMA).
Area of Science:
- Neonatal physiology
- Respiratory control in infants
- Sudden Infant Death Syndrome (SIDS) research
Background:
- Premature infants are at higher risk for Sudden Infant Death Syndrome (SIDS).
- The prone (stomach-down) sleeping position is associated with increased SIDS risk.
- Infants' ability to respond to respiratory challenges may be position-dependent.
Purpose of the Study:
- To investigate the influence of sleeping position (prone vs. supine) on premature infants' cardiorespiratory response to added dead space.
- To determine if the response to respiratory stress is impaired in the prone position at ages critical for SIDS.
Main Methods:
- Studied 20 premature infants (median gestational age 30 weeks) at a median postmenstrual age (PMA) of 45 weeks, comparing them to 25 infants at 36 weeks PMA.
- Measured minute ventilation, occlusion pressure (P0.1), and functional residual capacity (FRC) in both supine and prone positions.
- Calculated the time constant of the respiratory response to added dead space in each position.
Main Results:
- The time constant for responding to added dead space was significantly longer in the prone position (38 sec) compared to the supine position (26 sec).
- Infants in the prone position exhibited lower P0.1 and higher FRC compared to the supine position.
- In the prone position, a longer time constant (slower response) correlated with increasing PMA, indicating a dampened response with age up to the SIDS risk period.
Conclusions:
- The findings support the hypothesis that a dampened cardiorespiratory response to stress in the prone position contributes to the increased SIDS risk in premature infants.
- The position-dependent impairment in responding to respiratory challenges like added dead space may be a key factor in SIDS vulnerability.
- Understanding these physiological differences is crucial for developing targeted SIDS prevention strategies for premature infants.
Objective:
The vulnerability of prematurely born infants to sudden infant death syndrome (SIDS) in the prone position might be explained by a reduced ability to respond to a stress, such as hypercarbia, in that position; our objective, therefore, was to further explore the influence of position on the response to a stress.
Working Hypothesis:
The ability of prematurely born infants to respond to added dead space in the prone compared to the supine position would be impaired at the high risk age for SIDS.
Patients:
Twenty infants, median gestational age of 30 (range 24-32) weeks were studied at a median postmenstrual age (PMA) of 45 weeks. In addition, comparisons were made to the results of 25 infants studied at 36 weeks PMA.
Methodology:
Infants were studied supine and prone. Breath by breath minute volume was measured at baseline and after a dead space was incorporated into the breathing circuit; the time constant of the response was calculated. The pressure generated in the first 100 msec of an occlusion (P0.1 ), the maximum inspiratory pressure during an airway occlusion and functional residual capacity (FRC) were also measured in both positions.
Results:
The median time constant was longer (38 (range 15-85) vs. 26 (range 2-40) sec (P = 0.002)). P0.1 lower (P = 0.003) and FRC higher (P = 0.031) in the prone compared to the supine position. In the prone position, the time constant correlated with PMA (P = 0.047), that is, the rate of response to added dead space was significantly damped with increasing postnatal age up to the critical age for SIDS.
Conclusions:
The dampened rate of response to added dead space in the prone compared to the supine position lends support to the hypothesis that a poorer response to a stress may contribute to prematurely born infants increased risk of SIDS in the prone position.
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