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NBME 7 (to samomcos) - sunshine2009
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12-22-2009, 04:02 PM
A healthy 40 y. woman inhales to total lung capacity and then exhales forcefully ,,The rate of expiratory airflow is highest at total lung capacity and decreases linearly as exhaltaion continues....Which is the cause of the observed decrease in expiratory airflow? Answ> Airway compression.... Would you please explain the mech? Millions of thanx
12-22-2009, 05:00 PM
might not be as good as samomcos' explanation.........
whenever u exhale forcefully, u r actually applying a radial compression on the walls of the airways via the lung parenchyma, thus reducing the circumference through which the air had to flow out........ if this were not the case then the lungs wd have collapsed due a rapid outflow of air..........so this is kind of a protective mechanism......... At TLC the airways are fully dilated n hence when the exhalation wd start from this point it will be high n when a forceful exhalation is done, there wd be narrowing of the airway n this wd cause dec in exp flow rate....... |
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