Effect of inspiratory resistance and PEEP on 99mTc-DTPA clearance.
Experiments were performed to determine the effect of markedly negative pleural pressure (Ppl) or positive end-expiratory pressure (PEEP) on the pulmonary clearance (k) of technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA). A submicronic aerosol containing 99mTc-DTPA was insufflated into the lungs of anesthetized intubated sheep. In six experiments k was 0.44 +/- 0.46% (SD)/min during the initial 30 min and was unchanged during the subsequent 30-min interval [k = 0.21 +/- 12%/min] when there was markedly increased inspiratory resistance. A 3-mm-diam orifice in the inspiratory tubing created the resistance. It resulted on average in a 13-cmH2O decrease in inspiratory Ppl. In eight additional experiments sheep were exposed to 2, 10, and 15 cmH2O PEEP (20 min at each level). During 2 cmH2O PEEP k = 0.47 +/- 0.15%/min, and clearance increased slightly at 10 cmH2O PEEP [0.76 +/- 0.28%/min, P less than 0.01]. When PEEP was increased to 15 cmH2O a marked increase in clearance occurred [k = 1.95 +/- 1.08%/min, P less than 0.001]. The experiments demonstrate that markedly negative inspiratory pressures do not accelerate the clearance of 99mTc-DTPA from normal lungs. The effect of PEEP on k is nonlinear, with large effects being seen only with very large increases in PEEP.
D000403:Airway Resistance; D000818:Animals; D002199:Capillary Permeability; D004369:Pentetic Acid; D011175:Positive-Pressure Respiration; D011650:Pulmonary Alveoli / Q000098:blood supply / Q000503:physiopathology; D011654:Pulmonary Edema / Q000175:diagnosis / Q000503:physiopathology; D012756:Sheep; D013667:Technetium; D016284:Technetium Tc 99m Pentetate
D013667:Technetium; D004369:Pentetic Acid; D016284:Technetium Tc 99m Pentetate