BACKGROUND AND PURPOSE: Increasing arterial @entity26 partial pressure ( @entity4095 ) by breathing hyperoxic gases is an effective means of improving @entity5 oxygenation, although the efficacy of adding @entity515 to the inspiratory gas has been discussed controversially. This study aimed at analyzing the impact of different inspiratory @entity515 fractions on the time course of oxygenation and perfusion changes in experimental @entity5 during and after inspiratory @entity871 . MATERIAL AND METHODS: Perfusion and oxygenation of @entity35 DS- @entity242 were studied during spontaneous breathing of pure @entity26 or hyperoxic gas mixtures containing different @entity515 fractions (1, 2.5 or 5%). Red blood cell (RBC) flux was assessed as a measure of @entity5 perfusion using the laser Doppler technique and temporal changes in mean @entity5 @entity4095 were measured polarographically. RESULTS: Mean @entity5 @entity4095 increased 3.6-fold with pure @entity26 , approx. 3.3-fold when 1 or 2.5% @entity515 was added and 2.7-fold during @entity15436 breathing. RBC flux also increased by 25-30% with all gases. With pure @entity26 and with 1% @entity515 (+99% O2), perfusion changes paralleled those of the mean arterial blood pressure whereas with higher @entity515 fractions, a decrease in resistance to flow was observed. The differences found with the various gas mixtures were more pronounced after the end of @entity871 . With pure @entity26 , perfusion immediately returned to pretreatment values whereas with higher @entity515 fractions perfusion remained elevated for at least 30 min. CONCLUSIONS: Higher inspiratory @entity515 fractions (2.5 or 5%) lead to a prolonged improvement of @entity5 perfusion after the end of inspiratory @entity871 when compared with pure @entity26 breathing. Since no principal differences in oxygenation and perfusion were seen between the gases containing 2.5 and 5% @entity515 , the former may be preferable for inspiratory @entity871 .

Dynamics of XXXX oxygenation and red blood cell flux in response to inspiratory @entity871 combined with different levels of inspiratory hypercapnia.

@entity242 :: ('MESH:D012509', 'Disease') :: ['sarcomas'] @entity15436 :: ('MESH:C011700', 'Chemical') :: ['carbogen'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor', 'tumors'] @entity871 :: ('MESH:D018496', 'Disease') :: ['hyperoxia'] @entity26 :: ('MESH:D010100', 'Chemical') :: ['oxygen'] @entity515 :: ('CHEBI:29334', 'Chemical') :: ['CO2'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity4095 :: ('MESH:C093415', 'Chemical') :: ['pO2']
@entity5 :: (MESH:D009369,Disease) :: ['tumor']
