Non-invasive assessment of shunt and ventilation/perfusion ratio in neonates with pulmonary failure
H L Smith, J G Jones
Cambridge
University Department of Anaesthesia, Addenbrooke's Hospital,
Cambridge, UK
Correspondence to: Professor Jones, Department of Anaesthesia, Cambridge University, Level 4, Addenbrooke's Hospital, Cambridge CB2 2QQ, UK gareth{at}garjons.demon.co.uk
Accepted 14 May 2001
AIMS
To make
non-invasive measurements of right to left (R-L) shunt and reduced
ventilation/perfusion ratio (VA/Q) in neonates with
pulmonary failure and to examine sequential changes in these variables
after treatment.
METHODSTwelve
neonates with pulmonary failure were studied. They ranged in
gestational age from 24 to 37 (median 27) weeks and were 1-39 (median
4) days old. Shunt and reduced VA/Q were derived from their
effects on the relation between inspired oxygen pressure (PIO2) and arterial oxygen saturation measured
with a pulse oximeter (SpO2). Pairs of
PIO2 v
SpO2 data points were obtained by varying PIO2 in a stepwise fashion. A computer
algorithm based on a model of pulmonary gas exchange fitted a curve to
these data. With PIO2 on the abscissa, an
increase in shunt produced a downward movement of the curve, whereas
reducing VA/Q to < 0.8 shifted the curve to the right.
The right shift gives a variable that is inversely related to
VA/Q, the
PIO2 
P
RESULTSTen of the 12 infants on the first study day had large shunts (range 5.9-31.0%,
median 19.9%, normal < 8%) and large
PIO2 P
CONCLUSIONThis simple
non-invasive method distinguishes between shunt and reduced
VA/Q in neonates with pulmonary failure.
Keywords: shunt; VA/Q; non-invasive; oxygen saturation
© 2001 by Archives of Disease in Childhood
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This article has been cited by other articles:
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Quine, D, Wong, C M, Boyle, E M, Jones, J G, Stenson, B J
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