Data viva — humidification devices and perioperative heat loss

Stimulus

A two-panel diagram with a pie chart beneath it. The left panel shows a passive heat and moisture exchanger: a small housing containing a hygroscopic membrane, interposed between the tracheal tube and the breathing circuit. The right panel shows an active heated water-bath humidifier: a water reservoir warmed by a heater plate, with a heated wire running along the inspiratory limb and a temperature probe sited at the patient's airway. The pie chart below divides perioperative heat loss into four sectors — radiation the largest at about 60 per cent, then convection, then evaporation, then conduction the smallest.