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EFFECT OF ENHANCED SUPRAMAXIMAL FLOWS ON COUGH CLEARANCE
Citation:
Bennett, W. AND K. Zeman. EFFECT OF ENHANCED SUPRAMAXIMAL FLOWS ON COUGH CLEARANCE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/294, 1994.
Description:
Models of cough efficacy suggest that the efficiency of cough for clearing mucus from the lungs is a function of peak airflow velocities in the airways. nitial, transient supramaximal flows are characteristic of cough, especially in patients with chronic obstruction and these peak flow rates can be enhanced by placing a triggered shutter at the mouth. sing radiolabeled, monodispersed aerosols (Tc99m-iron oxide) and ganuna camera analysis, we measured the efficacy of (n) coughs vs. shutter (s) coughs for clearing mucus from the airways of patients with chronic airway obstruction. learance of the radiolabeled aerosol was studied over a 2 h period on three separate days, a control day with no coughing and two study days during which the patient performed cough maneuvers over the course of clearance measurements. n the two cough study days, the patient performed 60 controlled coughs, either natural or shutter, over a 60 min period beginning after the initial 4 min deposition scan. s expected we found that mean peak flow rates (Q) were significantly greater for the shutter cough than the natural cough, mean Qs = 9.4+/-2.0(sd) L/s and Qn = 4.1+/-1.9 L/s, p<.001. etentions at 60 minutes (R60) (as a fraction of initial deposition) were significantly different for the three study days (p=.Ol), R60 = .83+/-.17 (control),.69+/-.18 (natural cough), and .75+/-.19 (shutter cough), but only control vs natural cough R60S were significantly different from each (p=.01). By contrast, retentions at 120 minutes (R120) were significantly different for the three days, but both natural and shutter cough were significantly different from control (p=.01 and p=.02, respectively), R120 = .73+/-.16 (control), .61+/-.20 (natural cough), and .65+/-.20 (shutter cough). hus, the natural coughs, with lower peak flows but likely higher intrathomcic pressures, tended to speed particle clearance more than the shutter coughs. hese results indicate that increased supramaximal flows do not cause further improvement in mucus clearance from the lung. hey do suggest however hat increased airway compression (i.e. higher pleural pressures at the onset of cough) may be important for maximizing cough efficacy.