Anesthesia circuit modeling under two-phase flow conditions

The typical anesthesia circuit used in all hospital operating rooms consists of a ventilator connected via long flexible hoses to a patient. Humidification is added on the inspiratory side of the circuit which leads to condensation and water accumulation within the hoses. Such accumulation can lead to as much as 50 ml of water within the inspired side over several hours. While it is possible to drain this water periodically, in practice the anesthesiologist usually minimizes such disturbances to the patient and allows it to accumulate. Water present in significant quantities within the airflow passage creates a complex two-phase fluid flow condition analogous to wind induced water waves within a confined channel. The changing mechanical load which the anesthesia circuit under these conditions presents to the respirator and patient has never been defined in terms of mathematical models. Increased mechanical loading on the patient expiratory side could also lead to excessive lung hyperinflation. The purpose of this research is to develop models of actual anesthesia circuits used in the operating room to address these issues. Such models should also be useful as a starting point in dealing with clearance of pulmonary secretions from mucus lined airways