Purpose of breathing

Purpose of breathing

Breathing brings in oxygen necessary for cellular respiration and eliminates the resulting carbon dioxide. If oxygen supply does not meet demand, desperate cells revert to anaerobic metabolism, resulting in lactic acidosis.1 Our oxygen requirement depends on the metabolic rate, but for a resting individual 3 mL O2/kg/min, should suffice. Meanwhile, we generate CO2 at a rate dependent on the respiratory quotient “R:”

where V˙C O2 and V˙O2 are the minute production of carbon dioxide and consump-tion of oxygen, respectively. R depends on the energy source (carbohydrates, proteins, fat). R approaches 1 in several conditions including pregnancy and patients on total peripheral nutrition (TPN), but we usually peg it at 0.8.