Hyperbaric oxygen therapy (HBOT) is used for tissue hypoxia and ischemia reperfusion injury, but can cause lung damage. Pulmonary oxygen toxicity is still under investigations, but data describing the effects of HBOT on respiratory mechanics ( in particular on the viscoelastic behavior of the respiratory system) are not available.

OBJECTIVES: 

The aim of this study was to measure the effects of a single standard HBOT on respiratory mechanics in normal anesthetized rats.

METHODS: Measurements were made in control rats and in experimental animals after HBOT, 100% O2 at 2.5 atm (1 atm = 101.325 kPa) for 90 min. The end-inspiratory occlusion method was applied in anesthetized, paralyzed, positive pressure-ventilated rats to assess the possible effects of HBOT on respiratory mechanics in normal rats. Using the end-inflation occlusion method, it was possible to quantify the ohmic and viscoelastic airway resistance and elastance of the respiratory system. Ohmic resistance is the normalized-to-flow pressure dissipation due to viscous forces opposing the airflow in the airways, as predicted by the Poiseuille law.

RESULTS: 

HBOT induced an increment in the elastance, ohmic airway resistance and in the total resistive pressure dissipation. The viscoelastic resistance due to stress relaxation was increased compared to control group.

CONCLUSIONS: 

HBOT acts in normal rats to increase the ohmic component of airway resistance. The elastic and viscoelastic components are altered as well, suggesting that HBOT effects on respiratory mechanics characteristics may be a prelude events of pulmonary oxygen toxicity. Investigations of fundamental mechanisms are still needed.