Whole-body impedance recording--a practical method for the diagnosis of sleep apnoea

The aim of this study was to evaluate the utility of whole-body impedance cardiography (ICGWB) in sleep studies, particularly in sleep apnoea detection. A comparison between simultaneous whole night ICGWB and standard polysomnographic recordings were made in 14 patients with a clinical suspicion of obstructive sleep apnoea, a mean age of 46 years (range 30-63 years) and a mean BMI of 29 kg m-2 (25-47). Obstructive apnoeas, central apnoeas and hypopnoeas all caused characteristic patterns in the ICGWB tracing. For an apnoea-hypopnoea index (AHI) > 15 events h-1, the sensitivity of ICGWB was 89% and the specificity 80%. In conclusion, ICGWB signal includes valuable physiological information that can be effectively used for the detection of sleep apnoea episodes. The method seems promising in cases where the multichannel polysomnography is not applicable or when ICGWB is used for haemodynamic monitoring in seriously ill and postoperative patients.