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

OBJECTIVES: To present further development of a fibre-optical respiratory rate monitor and evaluate the function in the final version.
METHODS: Respiration was recorded in 18 healthy volunteers of ages 9-83 years by three different methods simultaneously: fibre-optical monitoring, capnography and manually. 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 subjects were excluded because of pronounced differences between all three methods. One person was later diagnosed as having a nasal septum deviation. Recordings with any kind of technical problem were also excluded.
RESULTS: In total 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 methods was -0.5 to +1.5 when the mean respiratory frequency was 14 breaths per minute. Analysis of variance revealed that the fibre-optical monitor tended to overestimate the mean respiratory rate (p < 0.001).
CONCLUSION: The fibre-optical monitor has sufficient accuracy for clinical monitoring. It is easy to use and inexpensive. Combinations with pulse oximetry seem attractive, to use especially for application outside "high tech areas," for example when respiratory depressant drugs are used or in ambulances.