Flow resistance of airways under hyperbaric conditions.

Based on the known relations governing flow resistance of a tube during laminar and turbulent flow and the value of the so-called Reynold's number the following conclusions were derived: 1. The flow resistance of airways increases under hyperbaric conditions because a) the turbulent flow participates in the airways to a greater extent due to its gradual extension to minor airways, and b) during turbulent flow the flow resistance is directly proportional to the pressure of the inhaled gas. 2. If the pressure in the surrounding environment increases n-times, this has an impact on the distribution of laminar and turbulent flow in the airways and their flow resistance, similarly as if the flow rates would increase n-times under normobaric conditions. 3. Dynamic indicators of lung ventilation corresponding to higher flow rates (e.g. PEF - peak expiratory flow) are reduced under hyperbaric conditions to a greater extent than the dynamic parameters corresponding to lower flow rates (e.g. FMEF25-75 - forced midexpiratory flow) determined usually by conditions in the minor airways, where the flow usually remains laminar or intermediate.