Tracheal mucosal damage after aspiration. A scanning electron Microscope study

Area of Science:

• Gastroenterology
• Pulmonology
• Toxicology

Background:

• Aspiration of gastric contents is a known cause of pneumonitis.
• The specific effects of gastric aspiration on the large airways, particularly the trachea, are not well understood.

Purpose of the Study:

• To investigate the impact of varying gastric content compositions and pH levels on tracheal mucosa integrity and healing.
• To assess the severity of tracheal damage induced by aspiration of saline, hydrochloric acid, and canine gastric juice in a mouse model.

Main Methods:

• 63 healthy A/J mice were divided into four groups and intratracheally instilled with sterile saline (pH 5.9), hydrochloric acid (pH 1.5), canine gastric juice (pH 1.5), or canine gastric juice (pH 5.9).
• Tracheal tissues were examined using scanning electron microscopy at various time points (1, 6, 24, 48, 72 hours, and 7 days) post-aspiration.
• Lung inflammation was also assessed to determine the extent of associated pulmonary damage.

Main Results:

• Aspiration of hydrochloric acid (pH 1.5) caused significant desquamation of the tracheal epithelium, with regeneration beginning at 3 days and complete recovery by 7 days.
• Canine gastric juice (pH 1.5) induced similar but more delayed regenerative responses compared to hydrochloric acid.
• Canine gastric juice (pH 5.9) resulted in milder desquamation and delayed regeneration, indicating that both acidity and gastric juice components contribute to tracheal injury.

Conclusions:

• Gastric contents cause substantial tracheal mucosal damage, independent of clinically significant pneumonia.
• Lower pH levels of aspirated gastric contents exacerbate tracheal injury.
• Components within gastric juice itself may impede the healing process of the tracheal mucosa.