Hello Paul, and thanks for clarifying your question.
Turns out you're in luck. The research needed to answer your question
only seems to have recently become available.
An article in the lastest issue of Pediatrics:
PEDIATRICS Vol. 112 No. 1 July 2003, pp. 29-32
Effect of Posture on Oxygenation, Lung Volume, and Respiratory
Mechanics in Premature Infants Studied Before Discharge
Ravindra Yeshwant Bhat, MD, et al.
provides the data you are seeking.
The abstract of the article can be viewed at:
and the full-text is available there as well for a small one-time fee.
The study found that the lung capacity for 20 premature infants with a
median gestational age of 30 weeks (range: 27-32 weeks) had a mean
range of 23-27 mL/kg of bodyweight, depending on the whether the
infants were in a prone or supine position, and whether they received
oxygen or not.
More specifically, the data broke out this way:
Lung volume mL/kg
Infants receiving oxygen:
--Prone position: 25 (range 14-36)
--Supine position 23 (13-32)
--Prone postion: 27 (19-39)
--Supine position: 26 (17.7-35)
As you can see, there is a considerable range in lung capacity,
varying from 14-39 mL/kg.
Lung volume was assessed in the infants by "measurement of functional
residual capacity (FRC) using a helium gas dilution technique and a
specially designed infant circuit".
Due to copyright restrictions, I cannot reproduce the full article
here. However, if you need any additional detail about the data
cited, methods used, or other aspects of the research, just let me
know by posting a Request for Clarification, and I'll be happy to
assist you further.