Final answer:
According to the head injury standard, the rate at which we should hyperventilate an adult, child, and infant if ETCO2 is not available is 20 breaths per minute for adults, 25 breaths per minute for children, and 30 breaths per minute for infants.
Step-by-step explanation:
According to the head injury standard, if ETCO2 is not available, the rate at which we should hyperventilate an adult, child, and infant would be:
Adult: 20 breaths per minute
Child: 25 breaths per minute
Infant: 30 breaths per minute