[Structural changes in the lungs induced by different levels of hyperbaric oxygenation]

Area of Science:

• Pulmonary Pathology
• Hyperbaric Medicine
• Cell Biology

Context:

• Hyperbaric oxygen therapy (HBOT) involves breathing pure oxygen at increased atmospheric pressure.
• Understanding the safe limits of HBOT is crucial for clinical applications and preventing lung injury.
• Previous research has established general risks, but specific safe pressure and duration thresholds require further elucidation.

Purpose:

• To investigate the morphological and ultrastructural lung changes in rabbits exposed to varying durations and pressures of hyperbaric oxygen.
• To determine safe regimens for hyperbaric oxygenation by assessing lung tissue response.
• To identify the cellular and structural components of the lung most vulnerable to hyperbaric oxygen toxicity.

Summary:

• Rabbits exposed to 100% oxygen at 2-4 ata for 60 minutes daily over 1-3 weeks showed pressure- and duration-dependent lung changes.
• Pressures of 2 ata for 2 weeks or 2.5 ata for 1 week were identified as safe hyperbaric oxygenation regimens.
• Higher pressures (3-4 ata) induced microcirculatory disturbances, aero-hematogenic barrier damage, edema, and cellular degeneration, particularly in endothelium and type I alveolocytes.
• Type II alveolocytes demonstrated greater stability, while mitochondrial and lamellar body hypertrophy was noted in damaged areas.

Impact:

• Establishes specific safe pressure and duration limits for hyperbaric oxygen therapy in preclinical models.
• Provides critical data for optimizing HBOT protocols to maximize therapeutic benefits while minimizing pulmonary risks.
• Highlights the differential vulnerability of lung cell types to hyperbaric oxygen, guiding future research into protective strategies.