DETERMINATION OF PRODUCTION OF NITRIC-OXIDE BY LOWER AIRWAYS OF HUMANS-THEORY

Exercise and inflammatory lung disorders such as asthma and acute lung injury increase exhaled nitric oxide (NO). This finding is interprete d as a rise in production of NO by the lungs (VNO) but fails to take i nto account the diffusing capacity for NO (DNO) that carries NO into t he pulmonary capillary blood. We have derived equations to measure VNO from the following rates, which determine NO tension in the lungs (PL ) at any moment from I)production (VNO); 2) diffusion, where DNO(PL) = rate of removal by lung capillary blood; and 3) ventilation, where VA (PL)/(PB - 47) = the rate of NO removal by alveolar ventilation (VA) a nd PB is barometric pressure. During open-circuit breathing when PL is not in equilibrium, d/dt PL[V-L/(PB - 47)] (where V-L is volume of NO in the lower airways) = VNO - DNO(PL) - VA(PL)/(PB - 47). When PL rea ches a steady state so that d/dt = 0 and VA is eliminated by rebreathi ng or breath holding, then PL = VNO/DNO. PL can be interpreted as NO p roduction per unit of DNO. This equation predicts that diseases that d iminish DNO but do not alter VNO will increase expired NO levels. Thes e equations permit precise measurements of VNO that can be applied to determining factors controlling NO production by the lungs.