Morphometric estimation of pulmonary diffusion capacity in two horse lungs.

The study on two gelding horses aimed to estimate morphometrically the pulmonary diffusion capacity. Employing fixative solutions during deep anaesthesia, samples from 22 lung regions were analyzed microscopically. From the obtained data, the researchers calculated the total pulmonary diffusion capacity for oxygen, which showed regional differences within the lung.

Materials and Method

• The study focused on two half-bred gelding horses, both weighing 510 kg with an average lung volume of approximately 38 litres.
• The horses’ lungs were fixed in situ or in their original place, using a glutaraldehyde solution. These solutions were introduced into the airways during deep anaesthesia.

Data Collection and Analysis

• The researchers randomly sampled and morphometrically analysed 22 regions of the lungs. Morphometry here refers to the quantitative measurement of the shape and structure of the lungs.
• These analyses were conducted on electron microscopic films.
• The study discovered that 86% of the total lung volume was dedicated to gas exchange.
• The air space and the interalveolar septa (the walls between the alveoli) are included in this area.
• The average surface areas of the alveolus (the functional unit of the lung) and the capillaries were also documented.
• Meanwhile, the tissue barrier’s arithmetic mean thickness and the harmonic mean thicknesses for the plasma barrier were also calculated and presented.

Results

• With the obtained morphometric data, the team calculated the total pulmonary diffusion capacity for oxygen. This measure specifies how efficiently the lungs transfer oxygen to the blood.
• The highest and lowest capacity calculated were reported as 3.55 l/min x mm Hg and 1.75 l/min x mm Hg, respectively.
• However, the study found substantial regional differences within each lung, particularly between the apical (near the top) and diaphragmatic (near the bottom) lobes.
• The comparison revealed that the apical lobes have a larger volume density of alveoli but a smaller volume and surface density of capillaries than the diaphragmatic lobes.