A model investigation of the impact of ventilation-perfusion mismatch on oxygenation during apnea in preterm infants.

Abstract

Ventilation-perfusion (V/Q) mismatch is a prominent feature of preterm infants and adults with lung disease. V/Q mismatch is known to cause arterial hypoxemia under steady-state conditions, and has been proposed as the cause of rapid arterial oxygen desaturation during apnea. However, there is little evidence to support a role for V/Q mismatch in the dynamic changes in arterial oxygenation that occur during apnea. Using a mathematical model, we quantified the effect of V/Q mismatch on the rate of desaturation during apnea to ascertain whether it could lead to rates of up to 10%s(-1) as observed in preterm infants. We used a lung-body model for the preterm infant that incorporated 50 parallel alveolar-capillary units that were ventilated and perfused with the severity of V/Q mismatch (sigma) defined conventionally according to sigma=S.D. of the distribution of V/Q ratios. Average desaturation rate 10s from apnea onset was strongly elevated with worsening V/Q mismatch as a result of an earlier desaturation of low V/Q units compared with high V/Q units. However, V/Q mismatch had little impact after apnea onset, with peak desaturation rate only substantially increased if mismatching caused a lowered resting arterial O(2) saturation. In conclusion, V/Q mismatch causes a more immediate onset of desaturation during apnea, and therefore places preterm infants and adults with lung disease at risk of hypoxemic dips. However, V/Q mismatch does not accelerate desaturation rate beyond apnea onset and cannot, therefore, explain the rapid desaturation observed during recurrent apnea in preterm infants.

• Authors: Scott A Sands, Bradley A Edwards, Vanessa J Kelly, Malcolm R Davidson, Malcolm H Wilkinson, Philip J Berger
• Journal: Journal of theoretical biology (J Theor Biol) Vol. 264 Issue 3 Pg. 657-62 (Jun 07 2010) ISSN: 1095-8541 [Electronic] England
• PMID: 20362590 (Publication Type: Journal Article)
• Copyright: Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Topics

• Apnea (physiopathology)
• Humans
• Infant, Newborn
• Infant, Premature (physiology)
• Lung (blood supply, physiopathology)
• Models, Biological
• Oxygen Consumption
• Pulmonary Ventilation (physiology)
• Respiration