Respiratory rate is a routinely monitored vital parameter in hospitals. Despite the change in respiratory rate often being the first sign of patient deterioration, it is not always a sufficient indicator of patient’s ventilatory status. A number of adverse events could be reacted to earlier if also the respiratory volume was monitored.In this work, feasibility of indirect respiratory volume measurements was assessed. Impedance pneumography (IP) and respiratory inductance plethysmography (RIP) measurement data from 15 measurement sessions with voluntary test subjects were analyzed. Signal amplitude was used to track relative minute volume values. Furthermore, a signal quality indicator was developed to detect sections of signal where the relative volume estimate was unreliable.The average coefficient of determination, R2, for the best RIP signal evaluation method was 0.71 while it was 0.53 for IP. RIP is more accurate than IP, but requires an extra sensor whereas IP can be measured simultaneously with ECG using the same electrodes. The developed signal quality index method improved coefficient of determination between the reference method and IP measurement to R2 = 0.66. The relative volume information is lost with patient posture change, but this change could be detected using other methods. These results show that IP and RIP can detect trends in respiratory volume.
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