Respiratory system 2nd line of defense Acts within min -maximal in 12-24 rs H2 CO3 produced converted to coal and excreted by the lungs. Alveolar ventilation also increases as pH decreases(rate and depth) Coarse, CAnNot eliminate fixed acidRespiratory System ◼ 2nd line of defense. ◼ Acts within min. -maximal in 12-24 hrs. ◼ H2CO3 produced converted to CO2 , and excreted by the lungs. ◼ Alveolar ventilation also increases as pH decreases (rate and depth). ◼ Coarse , CANNOT eliminate fixed acid