Every manufacturer depends on the supply of raw materials, components, and sub-assemblies from other factories that specialize in the production of those parts. The production speed of a complete product depends on the delivery time of those components and on the following assembling.
When manufacturers cannot deliver enough products on time when using standard mass-production methods, then 3D printing can be a solution. 3D printers and the raw materials after often off the shelf available and production can start as soon as the design drawings are ready. More traditional prototyping methods, such as CNC, can be an option if the design of the part lends itself for those techniques.
Respirator valves have already been 3D printed successfully in response to the increased need for mechanical ventilation in Italian hospitals. However, medical devices pose unique problems that require additional precautions in 3D printing.