Measuring Expired Isoprene in Human Breath During Exercise

Researchers have recommended isoprene to be used as a marker in human breath to assess blood cholesterol. The use of breath isoprene has been theoretically proved as an effective and non-invasive diagnostic tool in determining the variations in blood cholesterol levels in humans.

Isoprene is washed from the muscles and exhaled during exercise. The pulmonary gas exchange process is thought to be the key mechanism behind this. This is apparent with an initial increase in expired concentration, followed by a decrease and stabilization.

The HPR20 Transient MS (Figure 1) was found to be suitable for this application, due to its quick response, extensive dynamic range and improved sensitivity provided by a PIC detector. A heated Quartz Inlet Capillary (QIC) was fixed to a modified proprietary breathing mask.

Figure 1. The Hiden HPR20 Transient MS

Experimental

A submaximal exercise regimen was set on a stationary bicycle for subjects of different ages and fitness levels. The control of resistance was given to the subject, and the effort level was controlled via the rate of perceived exertion. The test procedure included 1 minute's rest, gentle exercise for 5 minutes followed by a 5 minute rest period.

The initial level of isoprene was estimated to be ∼50 ppbv. From Figure 2, the initial 'washing out' of the isoprene from the muscles to the blood stream was observed to be approximately 200 ppbv.

Following this, the isoprene level was lowered to a baseline level, indicating the failure of blood isoprene level to return to its initial level during the rest period. The blood isoprene level was then increased to the initial level only after an hour of rest.

Figure 2. Trend data showing the change in isoprene concentration in expired breath during a submaximal exercise test.

Figure 3 shows the isoprene levels of each breath obtained using the HPR20 Transient MS. This also indicates the quick response of the instrument. Using these results, both end tidal as well as breathing rate can be measured. The results obtained were in contrast with the offline measurements that do not provide detailed information.

Figure 3. MASsoft v7 Data showing breath by breath isoprene levels during an exercise test.

Conclusion

The results prove the viability of performing analysis of exhaled isoprene in real time. They also demonstrate that the Hiden HPR-20 TMS is a versatile and high sensitivity tool for rapid analysis of compounds in human breath.

This information has been sourced, reviewed and adapted from materials provided by Hiden Analytical.

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