A concern related to the care of the mechanically ventilated patient is the development of VAP. For many years this concern focused on the ventilator circuit and humidifier. Accordingly, the circuit and humidifier have been changed on a regular basis in an attempt to decrease the VAP rate. However, as the evidence evolved, it became apparent that the origin of VAP is more likely from sites other than the ventilator circuit and thus the prevailing practice has become one of changing circuits less frequently. If this practice is safe, it will offer substantial cost savings. Other issues related to the components of the circuit and VAP have also become more important recently.