Conversion of nitrogen dioxide (no2) to nitric oxide (no)

Abstract

Inhalation of low levels of nitric oxide can rapidly and safely decrease pulmonary hypertension in mammals. A nitric oxide delivery system that converts nitrogen dioxide to nitric oxide employs a surface-active material, such as silica gel, coated with an aqueous solution of antioxidant, such as ascorbic acid.

1 .- 18 . (canceled) 
     
     
         19 . A method, comprising:
 conveying a gas containing nitrogen dioxide to a cartridge containing activated alumina;   passing the gas through the cartridge to remove the nitrogen dioxide, leaving a nitric oxide-containing gas; and   delivering the nitric oxide-containing gas to a patient.   
     
     
         20 . The method of  claim 19 , wherein the cartridge is a second cartridge, the method further comprising:
 conveying the gas to a first cartridge;   before passing the gas through the second cartridge, passing the gas through the first cartridge, the first cartridge including a substrate wetted with ascorbic acid such that the gas flows over the substrate and such that the ascorbic acid reacts with nitrogen dioxide to produce nitric oxide.   
     
     
         21 . The method of  claim 19 , wherein the gas originates from a reservoir containing dinitrogen tetroxide. 
     
     
         22 . The method of  claim 19 , wherein the gas originates from an unpressurized tankless source. 
     
     
         23 . The method of  claim 19 , further comprising mixing the nitric oxide-containing gas with an oxygen-containing gas before delivering the nitric oxide-containing gas to the patient. 
     
     
         24 . The method of  claim 19 , wherein the nitric oxide-containing gas is supplied to a ventilator prior to being delivered to the patient. 
     
     
         25 . The method of  claim 19 , further comprising delivering the nitric oxide-containing gas to a flexible bag prior to delivering the nitric-oxide containing gas to the patient such that a constant supply of nitric oxide can be delivered to the patient during inhalation. 
     
     
         26 . The method of  claim 19 , further comprising:
 measuring a concentration of nitrogen dioxide in the nitric oxide-containing gas before the nitric oxide-containing gas is delivered to a patient; and   generating an alarm when a concentration of nitrogen dioxide in the nitric-oxide containing gas exceeds a threshold.   
     
     
         27 . The method of  claim 19 , wherein the nitric oxide-containing gas is delivered to the patient to treat pulmonary hypertension. 
     
     
         28 . The method of  claim 19 , wherein the patient is a newborn and the nitric oxide-containing gas is delivered to treat persistent pulmonary hypertension. 
     
     
         29 . The method of  claim 19 , wherein the nitric oxide-containing gas is delivered to the patient to treat bronchopulmonary dysplasia. 
     
     
         30 . The method of  claim 19 , wherein the patient is a cardiac surgery patient. 
     
     
         31 . An apparatus, comprising:
 a cartridge including an inlet configured to receive a gas; and   activated alumina disposed within the cartridge, the activated alumina configured to remove nitrogen dioxide from the gas,   the cartridge including an outlet configured to expel the gas after it has passed through the activated alumina.   
     
     
         32 . The apparatus of  claim 31 , wherein the cartridge is a second cartridge, the inlet is a second inlet, and the outlet is a second outlet, the apparatus further comprising:
 a first cartridge including a first inlet configured to receive the gas;   a substrate configured to retain water disposed within the first cartridge; and   an aqueous antioxidant wetting the substrate, the first cartridge configured such that the gas flows from the first inlet and across the substrate such that the aqueous antioxidant converts nitrogen dioxide within the gas to nitric oxide,   the first cartridge including a first outlet configured to expel the gas after the gas has passed through the substrate, the second inlet being downstream of the first outlet.   
     
     
         33 . The apparatus of  claim 31 , further comprising a tankless source of the gas. 
     
     
         34 . The apparatus of  claim 31 , further comprising a reservoir containing dinitrogen tetroxide from which the gas is sourced. 
     
     
         35 . The apparatus of  claim 31 , the outlet of the cartridge is configured to be fluidically coupled to a ventilator such that the ventilator can deliver nitric oxide to a patient. 
     
     
         36 . The apparatus of  claim 31 , further comprising a sensor configured to produce a warning when a concentration of nitrogen dioxide in the nitric oxide-containing gas exceeds a threshold value. 
     
     
         37 . The apparatus of  claim 31 , wherein the cartridge is configured to remove all nitrogen dioxide from the nitrogen dioxide-containing gas. 
     
     
         38 . The apparatus of  claim 31 , wherein the activated alumina has a 8-14 mesh size.