Effect of air humidity on spinability and transport capacity of canine airway secretions

Abstract

The effect of varying the inspired air humidity on a rheological property (spinability) and transport capacity of airway mucus has been analyzed in 10 mongrel dogs. Tracheal mucus was collected in anesthetized dogs inspiring through an endotracheal tube the air of a climate chamber maintained at constant temperature (T°: 20°C). In one test, the dogs inspired air at an absolute humidity (AH) of 9 g water/m³ air directly through the endotracheal tube. In the other test, the dogs inspired through an artificial nose connected to the endotracheal tube giving a AH of 30 g water/m³ air. Tracheal mucus was collected at the external distal end of the endotracheal tube. The spinability (Sp) or thread-forming properties of mucus was measured. The relative mucociliary transport rate (TR) of mucus was analyzed on a frog palate epithelium preparation. The transport rate was significantly (p < 0.01) lower (range: 0.59–0.80) when the AH of the inspired air was low in comparison to that obtained with high AH (range: 0.70–1.13). The variations in mucus Sp due to changing AH were positively and significantly correlated (r = 0.80, p < 0.01) with the corresponding variations in TR. These results suggest that lowering the AH of air induces a decrease in the transport capacity which appears to be dependent on the change of spinability that occurs in the mucus.