A method and corresponding device are described for combating microbes and infections by delivering intermittent high doses of nitric oxide to a mammal for a period of time and which cycles between high and low concentration of nitric oxide gas. The high concentration of nitric oxide is preferably delivered intermittently for brief periods of time that are interspersed with periods of time with either no nitric oxide delivery or lower concentrations of nitric oxide. The method is advantageous because at higher concentration, nitric oxide gas overwhelms the defense mechanism of pathogens that use the mammalian body to replenish their thiol defense system. A lower dose or concentration of nitric oxide gas delivered in between the bursts of high concentration nitric oxide maintains nitrosative stress pressure on the pathogens and also reduces the risk of toxicity of nitric oxide gas.