SUMMARY. A circular diagram (Lanza 1984) was used to study the oxygenation state of I I patients with extensive bums (18% to 90% BSA, UBS from 42 to 270) admitted to the Edouard Herriot Hospital Burns Centre in Lyons. The patients were divided into three groups and three blood samples were taken from each patient in the first three weeks. Three circular diagrams were obtained, for each group, by tabulating the mean values of the parameters monitored, which were: PO.5, S25, SVO2, PVO2, SaO2, PaO2, T, PHv, PHa, PvCO2, Hb, CaO2, CaO2 (S25).
Examination of the diagrams revealed the repetition, in the three groups, of a single model, regardless of the varying gravity of the patients (the only exception is represented in the graph based on the parameters of sample A in Group 3).
Characteristic features are:
1) leftward shift of Hb curve
2) venous phase of O2 metabolism more or less tending to scarce peripheral utilization
3) increase in T.
It may thus be concluded that the bum patient presents impairment of O2 metabolism at tissue and pulmonary level which, though not severe enough to cause the patient's death, plays a negative role in a more general picture of organic pathology.

The study was carried out on 11 patients (1 woman, 10 men) aged between 24 and 54 years admitted to the Burn Centre at the H6pital Edouard Herriot, Lyons. Their burns ranged between 18% and 90% of body area (UBS between 42 and 270) (Tab. 1).

On the basis of the UBS the patients were divided into 3 groups:

GROUP 1
4 patients with UBS between 0 and 100. Average age 38 years (+/- 17.29). UBS average 65.2 (+/- 25.79).

The patients in the three groups were followed up (when possible) for 3 weeks. Each patient had blood removed within 5 days of admission (A) and again in the 2nd (B) and 3rd (C) week after the burn lesion.
The study was carried out on arterial blood samples and on venous blood taken from the right atrium in order to evaluate the 14 parameters (PO.5, S25, SVO2, SaO2, PVO2, PaO2, PvCO2, PaCO2, PHv, PHa, Hb, CaO2H, CaO2 (S25), T) which appear in the diagram.
Circular diagrams were made for each group of patients. These were derived from the average of the parameter values obtained for corresponding tests.

- Apparatus for measuring PO2, PCO2 pH (ABL 1 Radiometer)
- Tonometer with bain-marie thermostatically fixed at 37 'C provided with electrode for PO2
- IL Co-Oxyineter 282
- Personal Computer

Results

Study of the diagrams made with the values of the base blood samples in the three groups shows: in all three a leftward shift of the haemoglobin dissociation curve ana consequently an increase in S25; a more appreciable reduction of Hb in group 3 with a reduction of CaO2H and CaO2 (S25), this last depending on the increase in S25.
The increase in PaO2 in group 3 is due to the fact that from the beginning 3 patients had to be ventilated.
It is interesting to note that while in groups 1 and 2 there was an increase in T, an SvO2 with a value falling on the base circumference or slightly outside it, and a PV02 almost equal to normal values, in group 3 T was only just outside the base circumference (statistically significant datum: P< 0,0 1) while SvO2 and PvO2 were clearly within the circle.
With regard to the subsequent diagrams it can be said that their appearance was similar in all three groups, i.e. the leftward shift of the haemoglobin dissociation curve persisted in all three groups in the second week, together with the increase in S25 and a tissue phase characterized by slightly increased SVO2 levels at normal PvO2 levels.
There were no particular variations in the third week except an increase in SVO2 and PVO2 in allthree groups.
There was however a different behaviour of T in groups 1 and 2 compared to group 3. In the first two groups an initial lengthening of T was followed by a tendency to shortening, while in group 3 T was almost normal in the first test, with a tendency to increase from the first to the third week (Tab 2) (Fig.2-10).

Discussion

The most striking aspect of the above results is the repetition in all three groups of the same model regardless of the different degrees of gravity of the patients examined.
The only exception is in the diagram for the first test on the most acute patients. This diagram seems the most favourable for the patients. A comparison between it and the corresponding diagrams for patients with less extensive bums shows:

1) T almost normal
2) a venous phase characterized by good tissue extraction.

Experimental studies on dogs have shown that after administration of sodium nitroprussiate and of nitroglycerine T tends to increase while the administration of vasopressin shortens T, as a result, respectively, of an increase or a drop in the shunt effect (4, 5)
It could iherefore be hypothesized that the lengthening of T in the patients in groups 1 and 2 may be connected to an increase of the capillary shunt following phenomena of interstitial oedema and atelectasis, while the normal T in group 3 may be due in the more acute patients to a redistribution in the pulmonary circulation caused by vasoconstriction. This condition, by reducing the shunt effect, might mask a pulmonary situation analogous to that of the other groups; with regard to this, the good venous extraction would also confirm centralization of the circulation.
In the subsequent tests there is a progressive increase in T, which reaches the highest levels of the three groups; in groups 1 and 2 it tends instead to shorten.
It would therefore seem that the first diagram of group 3, far from being the best, may conceal a haemodynamic condition connected with the shock phase.
It would be hazardous to draw any definite conclusions, considering the limited number of patients examined, but we believe that the use of this diagram makes it possible to monitor data relative to the oxygenation state of the acute burn patient by providing a visual representation which correlates all parameters both of the transport phase and O2 tissue utilization, and the pulmonary condition at the time.
We are thus of the opinion that the use of this method in larger number of patients with a greater range of conditions may be recommended because, if our considerations are valid, the circular diagram could prove extremely useful.

RESUME. On a étudié l'état d'oxygénation en se servant d'un diagramme circulaire (Lanza 1984) chez I I patients pr6sentant des brûlures sur 18% ~ 90% du corps (UBS de 42 A 270) hospitalisés an Centre des Brûlés de I'Hôpital Edouard Herriot de Lyon. Sur les malades, répartis en 3 groupes, on a pratiqué trois prélévements au cours des trois premieres semaines Thospitalisation. Trois diagrammes circulaires ont été obtenus en passant A la tabulatrice les valeurs moyermes des paramétres qui sont: PO.5, S25, SVO2, PVO2, SaO2, PaO2, T, PHv, PHa, PvCO2, Hb, CaO2, CaO2 (S25).
L'étude des diagrammes a mis en évidence la répétition, chez les 3 groupes, d'un meme modéle indépendamment de la gravité des malades pris en considération (seule exception, le graphique dérivant des paramétres du prélévement A du troisiéme groupe).
Les caractéristiques principales en sont:
a) déplacement A gauche de la courbe de I'Hb
b) phase veineuse du metabolisme de O2 tendant plus ou moins A une faible utilisation périphérique
c) augmentation de T.
On pent donc conclure que le brûlé présente une altération du métabolisme de O2 au niveau. du tissu et des poumons, pas au point de causer la mort du patient mais suffisante pour s'insérer négativement dans un cadre plus vaste de pathologie de l'organisme.