Advan. Physiol. Edu. 27: 242-243, 2003;
doi:10.1152/advan.00035.2003
1043-4046/03 $5.00
ADV PHYSIOL EDUC 27:242-243, 2003
© 2003 American Physiological Society
ILLUMINATION
Two-Dimensional Oxygen Map For Graphic Representation of Different Hypoxic Conditions
S. Kostianev and
D. Iluchev
Dept. of Pathophysiology, University of Medicine, Plovdiv, Bulgaria, E-mail: kostian{at}plovdiv.techno-link.com
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Abstract
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As educators, we are continually designing new methods and procedures to enhance learning. During this process, good ideas are frequently generated and tested, but the extent of such activities may not be adequate for a full manuscript. Nonetheless, the ideas may be quite beneficial in improving the teaching and learning of physiology. Illuminations is a column designed to facilitate the sharing of these ideas (illuminations). The format of submissions is quite simple: a succinct description of about one or two double-spaced pages (less title and authorship) of something you have used for the classroom, teaching, lab, conference room, etc. You may include one or two simple figures or references. Submit ideas for inclusion in Illuminations directly to the Associate Editor in charge, Stephen DiCarlo (sdicarlo@med.wayne.edu).
The simultaneous measurement of oxygen partial pressure, oxygen saturation, and hemoglobin content are important for diagnosing pulmonary complications (1, 2). The differentiation between hypoxia (a decrease in oxygen partial pressure, PO2) and hypoxemia (a decrease in oxygen content, CTO2) is fundamental to an understanding of hypoxic conditions as well as for the diagnosis and optimal management of critically ill patients. The differentiation between hypoxia and hypoxemia helps specify the pathophysiological mechanism of the impaired oxygen balance and indicates whether oxygen therapy, additional ventilation, and/or active hemoglobin are required (2). The different combinations that could occur from the relationship between PO2 and CTO2 (9 in number) and the bulky terminology (e.g., hypoxic normoxemia) are difficult for many students to understand. Therefore, we present a two-dimensional oxygen map that can be used for a graphic representation and straightforward understanding of different hypoxic conditions (Fig. 1). In our department, we have used this map as an effective aid for teaching oxygen disturbances for more than 10 years. The oxygen map was designed by dividing the area around the oxygen dissociation curve into nine zones. Of the nine zones, A, B, D, and H are those that are clinically important in subjects breathing atmospheric air. Zones A and B include patients with respiratory insufficiency and zones D and H those having abnormal hemoglobin values. Zones E, F, and G are of significance in patients on normo- or hyperbaric oxygen therapy. Finally, zone N is normoxic normoxemia. As an illustration of the assessment capabilities of the diagram we show some typical cases.
- Hypoxic hypoxemia (zone A) can be found in patients with acute or exacerbated chronic respiratory insufficiency who need intensive care (common condition).
- Treatment principles: adequate ventilation and supplemental oxygen.
- Hypoxic normoxemia (zone B) is most often found in patients with stable chronic respiratory insufficiency and compensatory polyglobulia, e.g., patients with chronic obstructive pulmonary disease (common condition);
- Adequate treatment of respiratory insufficiency and oxygen therapy.
- Normoxic hyperoxemia (zone D) is characteristic of patients with polyglobulia (rare condition).
- The therapeutic target is reduction of the polyglobulia.
- Normoxic hypoxia (zone H) is found in patients with various types of anemias and dyshemoglobinopathies (common condition).
- Blood (erythrocytes) transfusion is usually needed.
- Hyperoxic hypoxemia (zone G) can be found in patients with hematoxic hypoxemia on oxygen therapy (rare condition).
- Removal of the noxious agent is often the only treatment needed. In severe cases with methemoglobinemia (Mhgb levels >30%), methylene blue may be utilized; in case of severe carboxihemoglobinemia, continuous oxygen therapy.
For the purpose of more accurate blood gas analysis, the conditions of hypoxia and hypoxemia are graded as mild, moderate, severe, and extreme. We believe that these diagnostic zones not only illustrate the types of arterial blood oxygen disturbance but also suggest the therapeutic approach with respect to the need of oxygen, ventilation, or active hemoglobin and their optimal combination in the course of the treatment. In addition, the oxygen map shows the effect of correction (arrows in Fig. 1).
In conclusion, the two-dimensional oxygen map can be used successfully for a straightforward understanding of different hypoxic conditions. The visualization of the relationships between oxygen PO2 and oxygen concentration is quite beneficial in improving teaching and learning in the field of respiratory pathophysiology.
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References
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- Iluchev D and Kostianev S. The deep picture method—a prerequisite for new studies in blood gas analysis. Blood Gas News 3: 7–10, 1994.
- Siggaard-Andersen O and Siggaard-Andersen M. The oxygen status algorithm: a computer program for calculating and displaying pH and blood gas data. Scand J Clin Lab Invest 50, Suppl 203: 29–45, 1990.
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Copyright © 2003 by the American Physiological Society.
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