Student Research: Cheryl Hart
PhD, , 1998
Faculty Advisor: Michael G. Yost
Theory and Evaluation of a New Physiologic Sampling Pump
Physiologic sampling pumps (PSPs) seek to change pump rate in proportion to the minute ventilation of the worker. The aim to account for (1) differences in minute ventilation between individuals and (2) correlation between air concentration of contaminants and minute ventilation. This dissertation presents PSP theory and evaluated a new PSP for use in the real world. Additionally, it develops an equation termed the physiologic volume-weighted average (P-VWA), which is comparable in significance to a time-weighted average (TWA).
A computer simulation evaluated the effect of correlation between air concentration and minute ventilation on inhaled dose estimates. The simulation outcome was a ratio of the inhaled dose estimates (DPSP/DTSP), termed the Exposure Ratio, which was strongly related to both the correlation between air concentration and minute ventilation, and the GSDs of their distribution.
The laboratory phase of this research evaluated a new heart rate-controlled PSP. Subjects bicycled on an ergometer to a set protocol while their minute ventilation and heart rates were recorded. Two methods were used to estimate minute ventilation from heart rate: (1) an individual calibration curve and (2) a predictive equation derived from a database of exercise test data. The PSP itself functioned according to design, but both estimation methods failed to achieve the a priori accuracy and precision goals.
A pilot study was performed to validate that the PSP could be used in real-world conditions. The PSP performed very smoothly: it could easily be used by Industrial Hygienists in workplaces, given an acceptable predictive equation related heart rate to minute ventilation.
This research also verified that the integrity of the charcoal tube sampling mechanism would not be compromised by breakthrough, even at high solvent levels.
This dissertation is significant because:
1) It demonstrates that given a better predictive equation relating heart rate to minute ventilation, a PSP could be built that would fit all criteria for real-world application;
2) It is the first time PSP theory has been developed and presented in the literature;
3) It is the first analysis of the effect of correlation between air concentration and minute ventilation on inhaled dose estimates.