Effect of Nasal High Flow Therapy on CO_2 Tension - Physico-mathematical Modelling

摘要

The respiratory system of a human embodies complex assembly of tissues and organs (typically internal and external intercostal muscles, diaphragm, lung and rib cage), which are coordinated in a fashion that allows the influx and efflux of air into the airways and lungs. Like all other biological systems, the respiratory system is susceptible to injuries and diseases. Where ventilation has been severely impaired leading to poor gaseous exchange across the lung tissue, biomechanical therapeutic modalities such as continuous positive airway pressure (CPAP) and mechanical ventilators have been prescribed for such patients. Currently, Nasal High Flow therapy (NHFT), a novel ventilation technique has been reported to improve gaseous exchange in both neonates and adults by supplying a constant flow of humidified and warmed air into the lungs. NHFT is presently applied in the management of apnoea of prematurity, respiratory distress syndrome, bronchiolitis, and acute lung injury. In spite of reported success, its mechanisms of action (MOA) are not wholly understood. This work, in terms of relevance, provides some insights into the MOA of NHFT by underscoring the mathematical basis for reported improved gaseous exchange during the administration of NHFT. The mathematical model predictions appreciably agreed with bench-top measurements - indicating 17% and 24% reduction in end tidal CO_2 concentration upon the respective administration of 30 l/min and 60 l/min NHFT.