Sleeping position and responses to a carbon dioxide challenge in convalescent prematurely born infants studied post-term.
OBJECTIVE
To test the hypothesis that the ventilatory response to a carbon dioxide (CO2) challenge would be lower in the prone compared to the supine position in prematurely born infants studied post-term. To determine whether there were postural-related differences in respiratory drive, respiratory muscle strength, thoracoabdominal synchrony and/or lung volume.


METHODS
Prospective cohort study.


METHODS
Tertiary neonatal unit.


METHODS
Eighteen infants (median gestational age 31 (range 22-32) weeks) were studied at a median of 5 (range 2-11) weeks post-term.


METHODS
The ventilatory responses to three added carbon dioxide (CO2) levels (0% baseline, 2% and 4%) were assessed in the prone and supine positions.


METHODS
The airway pressure change after the first 100 ms of an occluded inspiration (P0.1) (respiratory drive) and the maximum inspiratory pressure during crying with an occluded airway (Pimax) (respiratory muscle strength) were measured. The P0.1/Pimax ratio at each CO2 level and slope of the P0.1/Pimax response were calculated.


RESULTS
The mean P0.1 (p<0.05) and P0.1/Pimax (p<0.05) were higher and the functional residual capacity (p=0.031) lower in the supine compared to the prone position. The mean P0.1 and P0.1/Pimax increased independently of position as the percentage CO2 increased (p<0.001). There was no tendency for the differences in P0.1 and P0.1/Pimax between the prone and supine position to vary by CO2 level.


CONCLUSIONS
Convalescent, prematurely born infants studied post-term have a reduced respiratory drive, but not a lower ventilatory response to a CO2 challenge, in the prone compared to the supine position.
Division of Asthma, Allergy & Lung Biology, MRC-Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, , London, UK.
Tolulope
T
Saiki
Anthony D
AD
Milner
Simon
S
Hannam
Gerrard F
GF
Rafferty
Janet L
JL
Peacock
Anne
A
Greenough
D002245:Carbon Dioxide / Q000008:administration & dosage*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000139:chemically induced*; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D008176:Lung Volume Measurements; D008297:Male; D056888:Patient Positioning / Q000379:methods*; D010991:Plethysmography; D011446:Prospective Studies; D012129:Respiratory Function Tests / Q000295:instrumentation / Q000379:methods*
D002245:Carbon Dioxide
Respiratory; SIDS