Nitric oxide therapies

An apparatus, comprising:

• a cartridge including an inlet configured to receive a nitrogen dioxide-containing gas;
• a porous solid matrix including sintered polymeric resin and silica gel;
• and
• an aqueous antioxidant wetting the porous solid matrix,
• the cartridge configured such that when nitrogen dioxide-containing gas flows from the inlet and across the porous solid matrix, the aqueous antioxidant converts nitrogen dioxide to nitric oxide,
• the cartridge includes an outlet configured to expel nitric oxide-containing gas that has passed through the substrate.

A method, comprising:

• conveying a nitrogen dioxide-containing gas to a cartridge;
• passing the nitrogen dioxide-containing gas through the cartridge to remove the nitrogen dioxide and to produce a nitrogen oxide-containing gas, the cartridge including a porous solid matrix includes silica gel and a polymeric resin, the porous solid matrix wetted with an aqueous antioxidant;
• and
• delivering the nitric oxide-containing gas to a patient.

A method, comprising:

• sintering a polymeric resin and silica gel to form a porous solid matrix;
• wetting the porous solid matrix with an antioxidant;
• and
• placing the porous solid matrix in a cartridge such that the cartridge is configured to convert nitrogen dioxide to nitric oxide.