Oxygenation pattern and compensatory responses to hypoxia and hypercapnia following bilateral carotid body resection in humans.

Carotid body resection has been proposed as a novel treatment for sympathetically mediated diseases but the safety of bilateral carotid body resection (bCBR) for blood oxygenation during hypoxic stress (long-haul flights or high altitude) remains uncertain. Also unknown is whether central ventilatory drive is sufficient to maintain adequate oxygen saturation when exposed to hypercapnia with concomitant hypoxia. Thus, we administered: 15% O2 , 12% O2 , 5% CO2 /12% O2 and 5% CO2 /95% O2 to a group of four patients with congestive heart failure (65 ± 2.9 years) in whom bCBR was performed 5 years earlier. Ventilatory, haemodynamic and blood oxygen saturation ( S p O 2 ) responses were recorded non-invasively and compared to control groups with intact peripheral chemoreceptors (both healthy and heart failure patients). First, we confirmed that the ventilatory response to hypoxia was eliminated in patients with bCBR, although the increase in cardiac output was preserved. Second, administration of hypoxic gas mixtures resulted in a larger decrease in S p O 2 and greater short-term variability of the S p O 2 leading to a lower minimal S p O 2 for both hypoxia levels in the bCBR group compared to heart failure controls (82.5 ± 1.2% vs. 91.6 ± 2.3% for 15% O2 and 73.8 ± 4.0% vs. 83.7 ± 3.1% for 12% O2 ). Third, in bCBR patients the ventilatory response to hypercapnia was present and sufficient to maintain a minimal S p O 2 at a level comparable to heart failure controls following administration of 5% CO2 /12% O2 (88.7 ± 4.2% vs. 91.1 ± 2.8%). We conclude that bCBR carries a risk of significant oxygen desaturation even during mild hypoxia. Despite preservation of central chemosensitivity, future studies should focus on unilateral CBR or on pharmacological modulation of peripheral chemosensitivity.