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Arch Dis Child Fetal Neonatal Ed 2001;85:F127-F132 ( September )

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.
METHODS---Twelve 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&cmacr;O2 difference, where P&cmacr;O2 is mixed capillary oxygen pressure.
RESULTS---Ten 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&cmacr;O2 differences (range 9.7-64.4 kPa, median 19.8 kPa, normal < 7 kPa) equivalent to a median VA/Q of 0.2 (normal median VA/Q = 0.8). Sequential improvement in shunt and VA/Q were shown in most infants after treatment. Sudden large changes in these variables were shown in two infants.
CONCLUSION---This 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


This article has been cited by other articles:


Home page
 Arch. Dis. Child. Fetal Neonatal Ed.Home page
D Quine, C M Wong, E M Boyle, J G Jones, and B J Stenson
Non-invasive measurement of reduced ventilation:perfusion ratio and shunt in infants with bronchopulmonary dysplasia: a physiological definition of the disease
Arch. Dis. Child. Fetal Neonatal Ed., November 1, 2006; 91(6): F409 - F414.
[Abstract] [Full Text] [PDF]


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