Validation of a novel respiratory rate monitor based on exhaled humidity

Postoperative monitoring of ventilation is largely restricted to the measurement of haemoglobin-oxygen saturation (Sp(o2)) and respiratory rate (RR) derived from the ECG. Sp(o2) measurement is inadequate when used with supplemental oxygen and ECG-derived RR is subject to artifacts. A new monitor measures RR by quantifying the humidity of exhaled air (respiR8). The accuracy of the system was tested using a breathing simulator. In healthy volunteers, the respiR8 monitor was compared with two other methods of measuring RR: capnometry and counting of thoracic breathing movements. The ability of the monitor to track changes in RR resulting from the infusion of 2.5 g kg(1) fentanyl was assessed and compared with RR measured from a validated flow measurement system. The RR in 50 postoperative patients measured with the respiR8 was compared with that derived from the ECG. RR values were compared by population-based BlandAltman analyses. The respiR8 monitor was accurate in the range required in clinical practice. There was a close agreement between RR from respiR8, capnometry, and manual counting of respiratory movements without bias (limits of agreement 1 bpm). The respiR8 monitor was well able to accurately track RR changes from fentanyl. In postoperative patients, RR from respiR8 and ECG had a bias of 1.7 (5.7) bpm due to greater RR values observed from the ECG due to artifacts. The respiR8 gives an accurate measurement of RR and is useful in postoperative care.