Changes in the oxygenation of head and neck tumors during carbogen breathing.

The oxygenation of head and neck tumors and changes during carbogen breathing were assessed in 20 patients. The median oxygen tension (pO2) for each patient was lower in tumors before breathing carbogen than in normal tissues. The median pooled pO2 of all the tumors was 20 mmHg; for normal tissue it was 60 mmHg. Low values (below 10 mmHg) were found in 4 patients for the normal tissue and in 18 patients for tumors. During carbogen breathing, the median (61 mmHg) pO2 readings for all tumors was higher than that recorded before carbogen breathing. The frequency of low (< 10 mmHg) pO2 values decreased with carbogen breathing in 11 patients; only 4 patients still exhibited very low values (< 2 mmHg). Maximal effect was obtained within 1-6 min of gas exposure. The pO2 stayed high under carbogen breathing in 15 out of 16 patients. Return to pre-carbogen levels of oxygenation occurred in 1 min after the end of gas exposure. These data suggest that carbogen breathing increases tumor oxygenation as assessed by polarography. The breathing time appears to be important for therapeutical use and should to be taken into consideration.