PT  - JOURNAL ARTICLE
AU  - Thomas Rossor
AU  - Kamal Ali
AU  - Rebecca Trenear
AU  - Simon Hannam
AU  - Gerrard Rafferty
AU  - Anne Greenough
TI  - The effects of sleeping position on the ventilatory response to hypercarbia
DP  - 2014 Sep 01
TA  - European Respiratory Journal
PG  - 276
VI  - 44
IP  - Suppl 58
4099  - http://erj.ersjournals.com/content/44/Suppl_58/276.short
4100  - http://erj.ersjournals.com/content/44/Suppl_58/276.full
SO  - Eur Respir J2014 Sep 01; 44
AB  - BackgroundProne sleeping is an established risk factor for Sudden Infant Death Syndrome (SIDS), however the mechanism by which this contributes to vulnerability remains unclear.AimsTo determine whether prone sleeping impairs the ventilatory response to hypercarbia in newborn infants.MethodsInfants born at 36 weeks post-menstrual age or greater were recruited from the postnatal ward. An open circuit, consisting of a non-return valve, capnograph, and pneumotachograph, supplied gas at 4 litres/minute to a nasal mask. In both the prone and supine position baseline ventilation was measured for five minutes with the infant breathing air. The ventilatory response to either 2% or 4% carbon dioxide (CO2) enriched air was then measured for five minutes. Following five minutes recovery the infants was exposed to the alternative CO2 level, the order of gas exposure being randomised. Mean minute volume was calculated for the final minute of exposure at each gas level, and CO2 sensitivity calculated as the gradient of the line of best fit. The time constant, defined as the time taken to achieve 63% of the maximal response to 4% CO2 was also calculated.ResultsThirty-one infants infants (median gestational age 39 weeks, range 36-42 weeks) were studied. There was no significant difference in the CO2 sensitivity between positions. The time constant of the response to CO2 was significantly longer in the prone (median 70 seconds, range 5-233 seconds) compared to the supine position (median 34 seconds, range 8-173 seconds) (p=0.031).ConclusionOur results suggest that a damped ventilatory response to hypercarbia may contribute to vulnerability to SIDS of infants sleeping in the prone position.