Abstract
In order to evaluate the service life of respiratory cartridges it is important to understand the characteristics of human inspiration. Therefore, a new method had to be developed to simulate human inspiration. These data can be used to program "artificial lungs" for the determination of the service life of respiratory cartridges.
The aim of this study was to develop a method for morphological analysis of human respiration using polynomial regression. The inspiratory curves of 13 healthy male volunteers (age (median): 25 years) were analyzed. The volunteers participated in two sessions, one with and the other without using a respiratory cartridge. In each session the subjects were exposed to different levels of physical load (0 W, 50 W, 100 W, 150 W, (175 W), 200 W, (225 W) and 250 W) using a stationary bicycle. During each session the air volume flow was continuously recorded. For each level of physical load the last 10 inspiratory curves have been used for further analysis.
Polynomial regression (11th order) was applied using a software program developed by the author. To describe changes in inspiratory acceleration and retardation the first derivation of the polynomial function was used. In order to be able to compare inspiratory curves with different duration the extrema of the polynomial function were related to the total length of inspiration.
At levels of physical load from 0 to 175 W a median of three maxima of the inspiratory curves has been observed. While using the respiratory cartridge only one maximum was seen in the last level of physical load (250 W; n = 30 inspiratory curves).
The maximum air volume flow did not differ significantly between the levels of physical load with and without using a respiratory cartridge. However, with increasing physical load the maximum air volume flow increased. The respiratory frequency, duration of inspiration, tidal volume and airflow volume per minute were comparable to previous studies.
In conclusion, the use of polynomial regression models might be helpful for morphological analysis of human inspiration using large data sets.
Future studies including a larger number of subjects should be performed in order to confirm the shape of the inspiratory curves during different levels of physical load.
The application and further development of the described method might lead to better testing procedures for the evaluation of the service life of respiratory cartridges. |
