When the nanorobot passes through the lung capillaries, O2 partial pressure is high and CO2 partial pressure is low, so the onboard computer tells the sorting rotors to load the tanks with oxygen and to dump the CO2. When the device later finds itself in the oxygen-starved peripheral tissues, the sensor readings are reversed. CO2 partial pressure is relatively high and O2 partial pressure relatively low, so the onboard computer commands the sorting rotors to release O2 and to absorb CO2. Respirocytes mimic the action of the natural haemoglobin-filled red blood cells and can deliver 236 times more oxygen per unit volume than a natural red cell