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.
Assessment in 37 healthy volunteers (aged 23 to 53 years) provided evidence that in a hyperbaric environment (0.4 MPa) a significant decline of expiratory and inspiratory dynamic indicators of pulmonary ventilation occurs, as compared with normobaric conditions (0.1 MPa). This phenomenon has a physical basis and it should be a contraindication for subjects with bronchopulmonary obstruction to dwell in a hyperbaric environment.
The aim of this investigation was to study the effect of environmental pressure and surface tension on the size of gas bubbles in tissues and on their inner pressure. Due to the action of surface tension, the pressure inside the bubbles is always greater than the surrounding pressure. This phenomenon is the more marked, the smaller are the bubbles. Therapeutic compression leads to diminution of the volume of gas bubbles and thus to a rise of that portion of their inner pressure which is due to surface tension. In small bubbles the surface tension may cause their dissolution and disappearance. It is therefore correct to implement therapeutic compression in decompression sickness as soon as possible before the fusion of a significant number of small bubbles into larger ones occurs.
Mathematical relationships for simple models of the filling and evacuation of the urinary bladder have been found and analyzed. These make the determination of the concentration of microbes in the urinary bladder at a given moment possible in relation to different parameters such as the rate of urine flow from the ureters, the microbe concentration in urine, the reproduction rate of microorganisms, the capacity of the urinary bladder and the size of the residue which remains in the bladder after miction.
The surface tension of blood assessed in a group of 71 healthy subjects (24 men and 47 women) by the drop method at a temperature of 22 °C was 55.89 . 10~3 N.m-1, S.D. = 3.57 . 10~3 N.m-1. It did not correlate with age or sex of the examined subjects nor with any of the following variables: red cell sedimentation rate, blood haemoglobin levels, number of erythrocytes, total serum cholesterol, total serum triacylglycerols, creatinine blood levels, ALT and AST activity. The surface tension of blood and other body fluids can play an important part not only in the genesis and development of decompression sickness but also in other processes in the organism.