Cardiovascular morbidity and mortality are markedly increased in chronic kidney disease (CKD) and may be explained in part by sympathetic hyperactivity. Impaired hyperoxic chemoreflex sensitivity (CHRS) has been attributed to an increased sympathetic activity. The aim of the present study is to examine whether chemosensor function is altered in patients with stage 3 and stage 4 CKD.

Impaired hyperoxic chemoreflex sensitivity (CHRS) is assessed in patients with stage 3 CKD [glomerular filtration rate (GFR) 30-59 ml/min/1.73 m2], in patients with stage 4 CKD [GFR 15-29 ml/min/1.73 m2], as well as in patients without any evidence of CKD. CHRS is measured by determination of the venous partial pressure of oxygen and the heart rate before and after deactivation of the chemoreceptors by inhalation of pure oxygen. The difference in the R-R intervals before and after inhalation divided by the difference in the oxygen pressures is calculated as the CHRS. A CHRS below 3.0 ms/mmHg is defined as pathological. It should be shown that using a simple clinical bedside test we provide the first evidence for impaired hyperoxic chemoreflex sensitivity in stage 3 and 4 chronic kidney disease. We thereby may lay the basis for future intervention studies assessing chemosensor function in these patients.

Inclusion Criteria:

• Patients suffering from CDK stage 3 (GFR 30-59 ml/min/1.73 m²) or stage 4 (GFR 15-29 ml/min/1.73 m²)
• For the reference Patients without evidence for CDK

Exclusion Criteria:

• Patients with heart failure, history of myocardial infarction or instable angina pectoris, atrial fibrillation, hyperthyroidism, chronic pulmonary diseases, sleep apnoea syndrome, alcohol abuse and drug induced cardiomyopathy