Ventilatory response to added dead space and position in preterm infants at high risk age for SIDS

Tolulope Saiki (1) , Simon Hannam (1) , Gerrard F Rafferty (1) , Anthony D Milner (1) , Anne Greenough (2)

1 Division of Asthma, Allergy and Lung Biology, MRC Asthma Centre for Allergic Mechanisms in Asthma
2 King's College London School of Medicine at Guy's, King's College and St Thomas' Hospitals

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) versus 26 (range 2-40) seconds (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), ie. 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.

Mots clés: Medicine

Tolulope Saiki, Simon Hannam, Gerrard F Rafferty, Anthony D Milner, Anne Greenough. Ventilatory response to added dead space and position in preterm infants at high risk age for SIDS. Pediatric Pulmonology, 2010, 46 (3), pp.239. ⟨10.1002/ppul.21358⟩. ⟨hal-00599817⟩