Innate Immune Response of the Pig Laryngeal Mucosa to Endotracheal Intubation

Objective: The aim of this study was to measure the effects of endotracheal intubation on innate immune response within the pig laryngeal mucosa.

Study design: Prospective controlled basic science study.

Setting: The animal experiments and analyses were conducted at the University of Bristol.

Samples and methods: Eighteen pigs, matched at the major histocompatibility complex (MHC), were used in the study. The pigs were divided into 9 pairs. One of each pair (9 pigs in total) was intubated with an endotracheal tube under general anesthesia for 90 minutes. Two days later, pinch biopsies were taken from the supraglottis (specifically the false cords) and subglottis of both pigs. The experiment was repeated 8 more times. Based on quantitative immunohistochemistry, percentage areas of positive staining for CD172a, CD163, MHC class II, CD14, and CD16 were calculated separately for the epithelium and lamina propria of each biopsy.

Results: Total areas of laryngeal mucosa (epithelium and lamina propria) expressing CD172a and coexpressing CD163 and CD172a were significantly reduced at 2 days following endotracheal intubation (P = .039 and P = .037, respectively). MHC class II expression and MHC class II coexpression with CD172a were similarly reduced following intubation (P = .003 and P = .005, respectively). In the supraglottis, MHC class II coexpression with CD16 and CD14 was also reduced following endotracheal intubation (P = .037).

Conclusions: Our results indicate that endotracheal intubation reduces the number of innate immune cells within the upper airway mucosa. This may be an important first step in a cascade leading to chronic wound and scar formation causing airway stenosis.