Changes in lung ultrastructure after 7-hour pure oxygen ventilation through endotracheal intubation in dogs

Li YUAN; Shiduan WANG; Meixia LIU

ABSTRACT

BACKGROUND:

It has been clinically confirmed that inhalation of hyperoxic oxygen for 36-48 hours can causes irreversible hyperoxic lung injury.Whether inhaling oxygen less than 50％ can reduce the potential oxygen toxicity in lung injury?

OBJECTIVE:

To observe the changes of lung ultrastructures after pure xygen inhalation for 7 hours through endotracheal intubation in dogs.

DESIGN:

A randomized and controlled animal experiment.

SETTING:

Department of Anesthesiology,Affiliated Hospital of Medical College,Qingdao University.MATERIALSTotally 20 healthy hybrid dogs (6 females and 14 males),weighing 15-16 kg,were provided by the Animal Experimental Center in the Affiliated Hospital of Medical College,Qingdao University.BIRD 8400STi respiratory machine (Bird,USA) and HP-M102A multi-functional monitor (HP,USA) were used.

METHODS:

The experiment was completed in the Experimental Animal Center in the Affiliated Hospital of Medical College,Qingdao University from July 1999 to January 2000.①

Interventions:

The dogs were randomly ventilated with either fraction of inspired oxygen (FiO2) of 1 (group 1,n =10) or FiO2 of 0.34 (group 2,n =10),there were 3 females and 7 males in each group.All the dogs were ventilated for 7 hours.② EvaluationThe mean arterial pressure and heart rate were monitored at 1,3,5 and 7 hours after endotracheal intubation.Anesthetic gas monitor (Ohmeda 5250 RGM) was used to observe the fractional inspired oxygen concentration,end-tidal partial pressure of carbon dioxide (PetCO2), respiratory frequency and peaks of respiratory organs.Changes of lung ultrastructures of right lower lung lobe were observed with electron microscopy after 7-hour mechanical ventilation.MAIN OUTCOME

MEASURES:

① Hemodynamic parameters; ② Changes of lung ultrastructures.

RESULTS:

All the 20 dogs were involved in the anlaysis of analysis.① Results of hemodynamic parametersThere was no significant difference between the two groups at each time point mean arterial pressure,PetCO2,peaks of respiratory organs and heart rate (P ＞ 0.05).② Changes of lung ultrastructuresThe results of electron microscope showed that in group 1,there were swelling mitochondria was arranged in disorder,less matrix,and hyalomere appeared,thin double-deck membrane in 50％ samples; Interalveolar septum stroma was with edema in 60％ samples;Polymorphonuclear leukocyte gathered in vessel or emigrated out of vessel in 50％ samples; In group 2,double-deck membranes of mitochondria were integral,densely matrix showed micro-granule shape in 90％ samples; Pinocytosis in epithelial cells of type Ⅰ lung strengthened,being destroyed,and pinocytosis in endothelial cells strengthened in 10％ samples; Interalveolar septum stroma was with edema,no polymorphonuclear leukocyte gathered in vessel or emigrated out of vessel or corpuscule was empty in type Ⅱ alveolar epithelium in 20％ samples.

CONCLUSION:

More pathological ultramicroscopic changes are observed after 7-hour mechanical ventilation with pure oxygen,which reduces after mechanical ventilation with 34％ oxygen.Oxygen concentration should be decreased while long-time mechanical ventilation is executed so as to reduce potential lung injury with oxygen toxicity.