Publish in this journal
Journal Information
Vol. 40. Issue 10.
Pages 459-462 (October 2004)
Download PDF
More article options
Vol. 40. Issue 10.
Pages 459-462 (October 2004)
Original Articles
DOI: 10.1016/S1579-2129(06)60356-X
Full text access
Altitude, the Ratio of PaO2 to Fraction of Inspired Oxygen, and Shunt: Impact on the Assessment of Acute Lung Injury
J.R. Pérez-Padilla
Corresponding author

Correspondence: Dr. J.R. Pérez-Padilla. Departamento de Fisiología Pulmonar y Clínica de Sueño. Instituto Nacional de Enfermedades Respiratorias. Tlalpan 4502. México DF. México
Departamento de Fisiología Pulmonar and Clínica de Sueño, Instituto Nacional de Enfermedades Respiratorias, México DF, Mexico
Article information
Download PDF

The ratio of PaO2 to the fraction of inspired oxygen (PaO2/FIO2) is commonly used to determine the severity of acute lung injury and acute respiratory distress syndrome (ARDS). The research presented here used computational models of the lung to analyze the effect of altitude on the PaO2/FIO2 ratio and pulmonary shunt.

At a given shunt, the PaO2/FIO2 ratio is lower at higher altitudes. Therefore, when evaluating for ARDS based on a PaO2/FIO2 ratio of <200 mm Hg, patients residing at high altitudes will have less shunt and, presumably, less severe lung injury than patients at sea level.

This should be taken into consideration when comparing patients from different altitudes. Shunt should more often be measured directly or be estimated assuming a constant arteriovenous oxygen content difference.

Key Words:
Oxygenation index
Ratio PaO2 to fraction of inspired oxygen (FIO2),
Acute respiratory distress syndrome (ARDS)

El cociente presión arterial de oxígeno/fracción inspiratoria de oxígeno (PaO2/FiO2) se utiliza comúnmente para definir el grado de lesión pulmonar y el síndrome de insuficiencia respiratoria progresiva del adulto. En el presente trabajo se analizan las modificaciones que experimenta el índice con la altura sobre el nivel del mar y con los cortocircuitos en modelos computacionales de pulmón.

El cociente PaO2/FiO2 disminuye con la altura sobre el nivel del mar al mismo cortocircuito. Por lo tanto, los pacientes que residen a alturas considerables sobre el nivel del mar tienen un cortocircuito menor y presumiblemente un grado de daño pulmonar menor que los residentes al nivel del mar en el momento de cumplir el criterio de síndrome de insuficiencia respiratoria progresiva del adulto con un cociente PaO2/FiO2 de 200 Torr.

Esta variación debe tomarse en cuenta para la comparación de pacientes cuando provienen de alturas diferentes e indica que se ha de utilizar más frecuentemente la medición directa del cortocircuito o bien el cortocircuito calculado, asumiendo una diferencia arteriovenosa del contenido de oxígeno constante.

Palabras clave:
Índices de oxigenación
Síndrome de insuficiencia respiratoria progresiva del adulto (SIR-PA)
Full text is only aviable in PDF
BA Shapiro, WT Peruzzi.
Manejo clínico de los gases sanguíneos, Editorial Médica Panamericana, (1996),
RD Cane, BA Shapiro, R Templin.
Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in the critically ill.
Crit Care Med, 12 (1988), pp. 1243-1245
JM Dean, RC Wetzel, MC Rogers.
Arterial blood gas derived variables as estimates of intrapulmonary shunt in critically ill children.
Crit Care Med, 13 (1985), pp. 1029-1033
M Nirmalan, T Willard, MO Columb, P Nightingale.
Effect of changes in arterial-mixed venous oxygen content difference (C(a-v)O2) on indices of pulmonary oxygen transfer in a model ARDS lung.
Br J Anaesth, 86 (2001), pp. 477-485
CE Hahn.
KISS and indices of pulmonary oxygen transfer.
Br J Anaesth, 86 (2001), pp. 465-467
H Zetterstrom.
Assessment of the efficiency of pulmonary oxygenation. The choice of oxygenation index.
Acta Anaesthesiol Scand, 32 (1998), pp. 579-584
MK Gould, SJ Ruoss, NW Rizk, RL Doyle, TA Raffin.
Indices of hypoxemia in patients with acute respiratory distress syndrome: reliability, validity, and clinical usefulness.
Crit Care Med, 25 (1997), pp. 6-8
MS Gowda, RA Klocke.
Variables of indices of hypoxemia in adult respiratory distress syndrome.
Crit Care Med, 25 (1997), pp. 41-45
JH Wandrup.
Quantifying pulmonary oxygen transfer deficits in critically ill patients.
Acta Anaesthesiol Scand Suppl, 107 (1995), pp. 37-44
A Coetzee, J Swanevelder, G van der Spuy, J Jansen.
Gas exchange indices-how valid are they?.
S Afr Med J, 85 (1995), pp. 1227-1232
GR Bernard, A Artigas, KL Brigham, J Carlet, K Falke, L Hudson, et al.
The American-European Consensus Conference on ARDS. Definitions, mechanisms, relevant outcomes, and clinical trial coordination.
Am J Respir Crit Care Med, 149 (1994), pp. 818-824
A Artigas, GR Bernard, J Carlet, D Dreyfuss, L Gattinoni, L Hudson, et al.
The American-European Consensus Conference on ARDS, part 2. Ventilatory, pharmacologic, supportive therapy, study design strategies, and issues related to recovery and remodeling. Acute respiratory distress syndrome.
Am J Respir Crit Care Med, 157 (1998), pp. 1332-1347
JP Whiteley, DJ Gavaghan, CE Hahn.
Variation of venous admixture, SF6 shunt, PaO2, and the PaO2/FiO2 ratio with FIO2.
Br J Anaesth, 88 (2002), pp. 771-778
IA Herrick, LK Champion, AB Froese.
A clinical comparison of indices of pulmonary gas exchange with changes in the inspired oxygen concentration.
Can J Anaesth, 37 (1990), pp. 69-76
M Ward, JS Milledge, JB West.
Human and medical geography of mountain regions.
High altitude medicine and physiology, pp. 47
JR Pérez-Padilla.
Distribution of Mexican population residing at different altitudes. Implications for hypoxemia.
Arch Med Res, 33 (2002), pp. 162-166
JB West.
Ventilation-perfusion inequality and overall gas exchange in computer models of the lung.
Respir Physiol, 7 (1969), pp. 88-110
O Siggaard-Andersen, M Siggaard-Andersen.
The oxygen status algorithm: a computer program for calculating and displaying pH and blood gas data.
Scand J Clin Lab Invest Suppl, 203 (1990), pp. 29-45
JB West.
High life: a history of high-altitude physiology and medicine, pp. 413
A Boussuges, F Molenat, H Burnet, E Cauchy, B Gardette, JM Sainty, et al.
Operation Everest III (Comex 97): modifications of cardiac function secondary to altitude- induced hypoxia.
Am J Respir Crit Care Med, 161 (2000), pp. 264-270
C Santos, M Ferrer, J Roca, A Torres, C Hernández, R Rodríguez-Roisin.
Pulmonary gas exchange response to oxygen breathing in acute lung injury.
Am J Respir Crit Care Med, 161 (2000), pp. 26-31
Copyright © 2004. Sociedad Española de Neumología y Cirugía Torácica (SEPAR)
Archivos de Bronconeumología (English Edition)

Subscribe to our newsletter

Article options
es en

¿Es usted profesional sanitario apto para prescribir o dispensar medicamentos?

Are you a health professional able to prescribe or dispense drugs?