Changes in oxygen partial pressure of brain tissue in an animal model of obstructive apnea

• Main Authors: Torres Marta, Montserrat Josep M, Almendros Isaac, González Constancio, Navajas Daniel, Farré Ramon
• Format: Article
• Language: English
• Published: BMC 2010-01-01
• Series: Respiratory Research
• Online Access: http://respiratory-research.com/content/11/1/3

<p>Abstract</p> <p>Background</p> <p>Cognitive impairment is one of the main consequences of obstructive sleep apnea (OSA) and is usually attributed in part to the oxidative stress caused by intermittent hypoxia in cerebral tissues. The presence of oxygen-reactive species in the brain tissue should be produced by the deoxygenation-reoxygenation cycles which occur at tissue level during recurrent apneic events. However, how changes in arterial blood oxygen saturation (SpO₂) during repetitive apneas translate into oxygen partial pressure (PtO₂) in brain tissue has not been studied. The objective of this study was to assess whether brain tissue is partially protected from intermittently occurring interruption of O₂supply during recurrent swings in arterial SpO₂in an animal model of OSA.</p> <p>Methods</p> <p>Twenty-four male Sprague-Dawley rats (300-350 g) were used. Sixteen rats were anesthetized and non-invasively subjected to recurrent obstructive apneas: 60 apneas/h, 15 s each, for 1 h. A control group of 8 rats was instrumented but not subjected to obstructive apneas. PtO₂in the cerebral cortex was measured using a fast-response oxygen microelectrode. SpO₂was measured by pulse oximetry. The time dependence of arterial SpO₂and brain tissue PtO₂was carried out by Friedman repeated measures ANOVA.</p> <p>Results</p> <p>Arterial SpO₂showed a stable periodic pattern (no significant changes in maximum [95.5 ± 0.5%; m ± SE] and minimum values [83.9 ± 1.3%]). By contrast, brain tissue PtO₂exhibited a different pattern from that of arterial SpO₂. The minimum cerebral cortex PtO₂computed during the first apnea (29.6 ± 2.4 mmHg) was significantly lower than baseline PtO₂(39.7 ± 2.9 mmHg; p = 0.011). In contrast to SpO₂, the minimum and maximum values of PtO₂gradually increased (p < 0.001) over the course of the 60 min studied. After 60 min, the maximum (51.9 ± 3.9 mmHg) and minimum (43.7 ± 3.8 mmHg) values of PtO₂were significantly greater relative to baseline and the first apnea dip, respectively.</p> <p>Conclusions</p> <p>These data suggest that the cerebral cortex is partially protected from intermittently occurring interruption of O₂supply induced by obstructive apneas mimicking OSA.</p>