A noninvasive method for evaluating the effect of thoracotomy on shunt and ventilation perfusion inequality

Gray, Lewis D; Rush, E.M.; Jones, J. G.

doi:10.1111/j.1365-2044.1997.153-az0159.x

Cited by 26 publications

(23 citation statements)

References 17 publications

(17 reference statements)

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“…With a few exceptions the curves were stable—that is, a single shunt equation fitted all the P io 2 v Sp o 2 data points obtained from one subject during one data collection period. The results were similar to those seen in a variety of adult patients with pulmonary failure during anaesthesia,9thoracotomy,10 and after fat embolism 11…”

Section: Discussionsupporting

confidence: 77%

Non-invasive assessment of shunt and ventilation/perfusion ratio in neonates with pulmonary failure

Smith

Jones

2001

Archives of Disease in Childhood - Fetal and Neonatal Edition

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Aims-To make non-invasive measurements of right to left (R-L) shunt and reduced ventilation/perfusion ratio (V A /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 V A /Q were derived from their eVects on the relation between inspired oxygen pressure (PIO 2 ) and arterial oxygen saturation measured with a pulse oximeter (SpO 2 ). Pairs of PIO 2 v SpO 2 data points were obtained by varying PIO 2 in a stepwise fashion. A computer algorithm based on a model of pulmonary gas exchange fitted a curve to these data. With PIO 2 on the abscissa, an increase in shunt produced a downward movement of the curve, whereas reducing V A /Q to < 0.8 shifted the curve to the right. The right shift gives a variable that is inversely related to V A /Q, the PIO 2 − P c O 2 diVerence, where P c O 2 is mixed capillary oxygen pressure. A reduced ventilation/perfusion ratio (V A /Q) and an increased shunt cause quite diVerent, but characteristic, eVects on the relation between inspired oxygen pressure (PIO 2 ) and arterial oxygen saturation (SaO 2 ). 1 2 A reduced V A /Q in the absence of shunt reduces both alveolar oxygen (PAO 2 ) and oxygen saturation but increasing the PIO 2 washes out alveolar nitrogen, restores PAO 2 , and corrects desaturation. In contrast, an isolated shunt reduces oxygen saturation, but increasing PIO 2 does not correct this because the shunted blood is never exposed to the increased PIO 2 . The nonshunted blood is almost fully saturated, and even administering 100% oxygen adds only a small amount of dissolved oxygen, which cannot compensate for the eVect of the shunt. Results-TenIt may be important in neonates to diVerentiate between a reduced V A /Q and a shunt. For example, in an animal model of surfactant deficiency when surfactant was administered into the airways either as a bolus or as an aerosol, V A /Q worsened with the former but improved with the latter.3 There may also be a prognostic significance of diVerent degrees of

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Section: Discussionsupporting

confidence: 77%

Non-invasive assessment of shunt and ventilation/perfusion ratio in neonates with pulmonary failure

Smith

Jones

2001

Archives of Disease in Childhood - Fetal and Neonatal Edition

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“…It was realized by Riley et al [4,5] that mathematical models with two parameters are needed to describe the effects of changes in the alveolar oxygen fraction on S a O 2 . The shape and position of these curves are related to pulmonary gas exchange [2,6,7]. The shape and position of these curves are related to pulmonary gas exchange [2,6,7].…”

Section: Introductionmentioning

confidence: 99%

Non-invasive estimation of shunt and ventilation-perfusion mismatch

et al. 2003

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“…The two-parameter model of Sapsford et al [77] has been shown to fit data from normal subjects; patients before and after thoracotomy [77,78], patients during [77,79] and after [79] abdominal surgery, in neonates with pulmonary failure [81], and in infants with bronchopulmonary dysplasia [82,83]. The two-parameter model of Kjaergaard et al has been shown to fit data from normal subjects [84], patients before [75,84À86] and after [75,84À87] surgery, patients presenting in intensive care [66,84], and patients with incompensated heart failure studied before and after diuretic therapy [84].…”

Section: Application Of Models In Routine Clinical Practicementioning

confidence: 99%