Biopsies, sputum eosinophil levels and exhaled nitric oxide levels are the tests used currently when monitoring airway inflammation in asthma patients. The 2006 study by Piacentini suggests an easier method for testing inflammation. Piacentini used subjects with mild asthma and control subjects without asthma to test different markers of inflammation. The subjects rested for one hour before the initial test and rested for ten minutes between tests. Room temperature, humidity and axillary body temperature were strictly controlled.
This study found a positive correlation between end-expiratory manoeuvre plateau temperature (PLET), eosinophil percentage in sputum and exhaled nitric oxide. The use of salbutamol, a bronchodilator, caused an increase in PLET for both the asthmatics and the controls. The study also found no correlation between the above numbers and the rate on increase in exhaled breath temperature, which was a previously suggested method for measuring inflammation. This study also found that using a microbial filter during exhalation tests skewed the test curves and should not be used.
The conclusion is that PLET (exhaled air temperature) is a good marker of airway inflammation in asthma patients and could be used in adjusting treatment plans for asthma patients. More studies need to be done to determine a standardized procedure for testing PLET.
Piacentini GL, Peroni D, Crestani E, Zardini F, Bodini A, Costella S, Boner.
Exhaled air temperature in asthma: methods and relationship with markers of disease. Clinical and Experimental Allergy, 37, 415-419
Paredi P, Kharitonov SA, Barnes PJ. Faster rise of exhaled breath temperature in asthma: a novel marker of airway inflammation? Am J Respir Crit Care Med 2002; 165:181–4.
Paredi P, Kharitonov SA, Barnes PJ. Correlation of exhaled breath temperature with bronchial blood flow in asthma. Respir Res 2005; 6:15.
Piacentini GL, Bodini A, Zerman L et al. Relationship between exhaled air temperature and exhaled nitric oxide in childhood asthma. Eur Respir J 2002; 20:108–11.
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Note to anyone who has a question or comment. I will be out of town for 10 days (getting married). So, I will not respond until after thanksgiving. Thank you for your understanding.
So did the study have a hypothesis as to why asthmatics show an increase in PLET? I guess I can assume why but was just wondering what the authors thought about the issue. Also, did the study state HOW different the PLET is compared to controls? I assume it's a statistically significant difference if they are foreseeing it as a potential diagnostic aid for asthmatics. Very interesting approach to asthma treatment!
Stephen B - Very interesting. I pulled up the original article. I wondered the statistical significance was clinically significant. This study is amazing, they found statistical significance with a very small sample size. With a total of 57 participants, the study was comprised of "Mild Asthmatics" (n=41) and controls(n=only 16!) showed an almost average 2.5 degree Celsius difference. You might almost wonder if you need an instrument at all to detect that big of a change at all. How hot would severe asthmatics PLET scores be?
It is the answer you came up with I am sure. The increase in PLET (30.18 vs. 27.47 Degrees Celsius) is due to inflammation. They have a nice graph in the article showing the different PLET values. As we all know from hurting something, a broken foot for example, inflammation involves an increase in temperature. I would guess that heat (PLET) will increase with the severity of the asthma.
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