Evaluation of a new fibre-optical monitor for respiratory rate monitoring

Objectives. To present further development of a fibre-optical respiratory r ate monitor and evaluate the function in the final version. Methods. Respir ation was recorded in 18 healthy volunteers of ages 9-83 years by three dif ferent methods simultaneously: fibre-optical monitoring, capnography and ma nually. The recordings were made breath by breath in four 3-minute periods in each subject. In total there were 54 observations, corresponding to 648 minutes. The recordings were fed simultaneously into a computer. Two subjec ts were excluded because of pronounced differences between all three method s. One person was later diagnosed as having a nasal septum deviation. Recor dings with any kind of technical problem were also excluded. Results. In to tal 516 minutes were analysed. Students' paired t-test showed a mean of 0.5 and 0.3 more breaths were recorded by fibre-optical monitor compared with the manual method and capnography respectively. The 95% confidence interval of the differences between the fibre-optical monitor and the other two met hods was -0.5 to +1.5 when the mean respiratory frequency was 14 breaths pe r minute. Analysis of variance revealed that the fibre-optical monitor tend ed to overestimate the mean respiratory rate (p < 0.001). Conclusion. The f ibre-optical monitor has sufficient accuracy for clinical monitoring. It is easy to use and inexpensive. Combinations with pulse oximetry seem attract ive, to use especially for application outside "high tech areas," for examp le when respiratory depressant drugs are used or in ambulances.