For example: char a; a= getchar(); The function getchar() reads a single character from the standard input device, the keyboard being assumed because that is the standard input device, and assigns it to the variable a.
This excludes acute and chronic respiratory failure (518.84), acute respiratory distress (518.82), acute respiratory failure following trauma and surgery (518.51), chronic respiratory failure (518.83), respiratory arrest (799.1), and respiratory failure, newborn (770.84). This applies to respiratory failure NOS.
In this context, acute respiratory failure (ARF) could be defined as an incapacity of the respiratory system to capture oxygen (PO2) and/or to remove carbon oxide (PCO2) from the bloodstream and tissue cells. It is a syndrome, and not a disease, with several possible causes.