A numerical model of an intensive care ventilator-humidifier system

Current intensive care ventilator-humidifier systems neither monitor nor adequately control inspired gas humidity. Problems of low delivered humidity delivered humidity and condensation within ventilator circuitry are commonly encountered. To help to address these problems, a numerical model of a complete ventilator-humidifier-patient intensive care system has been developed. The model, based on a finite difference technique, can predict pressures, flow rates, temperatures and relative humidities at discrete points throughout the system. A comparison of numerical predictions and measurements in a real system is reported. A strong qualitative agreement is demonstrated in all cases studied, and a good quantitative agreement is obtained in most cases. It is concluded that such models could be used to assess methods of controlling ventilator-humidifier systems to prevent the occurrence of condensation. Similar models could be developed for other medical gas delivery systems. Copyright (C) 1996 Elsevier Science Ltd for IPEMB.