1. I believe the answers may vary since we have to take deep breaths, however these are not standardized .The differences in volumes do not affect the outcome of the experiment because O uptake and use is dependent on tissue metabolism (rate that tissues consume oxygen ), and not on frequency or depth of the breath .For example , we can only use a certain amount of inhaled O2 , regardless of how much of it we breathe in . Since we are calculating the O2 that is consumed , it is factored in both O2 concentrations in the air and total volume of inhaled air (tidal volume ).