Studies on pressure-volume relationships in excised equine lungs.

The research article discusses the examination of pressure-volume relationships in lungs from fetal and neonatal horses, investigating their stability and alterations due to breathing.

Research Methodology

• The researchers studied 48 lungs taken from young (fetal and neonatal) horses. This was done to examine how the volume of these lungs relates to the change in pressure within, ranging from 0 to 40 cmH2O.
• The data was obtained in the form of inflation-deflation curves where the volume was plotted against pressure. These graphical representations were then analyzed in four different ways.

Analyzing Lung Stability

• The stability of horse lungs was evaluated through three metrics: hysteresis, stability indices and volume of air retained at maximal pressure (Vmax).
• The term ‘hysteresis’ in this context refers to the difference between the inflation and deflation parts of the pressure-volume curves. Significant hysteresis suggests an energy loss possibly due to the elasticity of lung tissues.
• ‘Vmax’ is the volume of air retained in the lungs when they are under maximum pressure. This gives an estimate of the lungs’ maximum capacity.

Difference Between Ventilated and Non-vetilated Lungs

• The researchers also noticed that the deflation curves of ventilated and non-ventilated lungs differed significantly. This finding is consistent with previous research conducted on other species.
• The scientists believe that breathing modifies the elasticity of the lung tissues during the neonatal period. This possibility is suggested by a noticeable increase in the maximum volume of air (Vmax) that can be retained in the lungs, in foals that have been breathing for over 24 hours, compared to those that are stillborn or less than 24 hours old.

Stability Indices

• Stability indices such as the percentage of air retained in the lungs during deflation from Vmax to pressures of 10 or 5 cmH2O, were examined. These indices were found to be related to interfacial factors – the physical and chemical properties at the surface of the materials which constitute the lung tissues. Interfacial factors may include aspects like surface tension, adhesion, and friction between the interfacing materials.