demonstrated in a study conducted on dogs that HFOV in comparision to CPPV exhibited no effect on cardiac output which means that there is no direct relation between HFOV and cardiac output. (Irvin Mayers, 1989).
There is considerable effect of HFOV on the circulatory system. The high pressure generated by this method of ventilation causes the intrathoracic pressures to rise and exert force on the heart and interrupt the cardiac output. The decrease in cardiac output inturn reduce the blood pressure and a vicious cycle maybe set up. The process of avoiding this complication involves proper monitoring of the patients hemodynamic status including proper monitoring of not just the blood pressure but also the kidney function, urine output and organ perfusion. The change is the thoracic pressures as a result of the high frequency oscillatory ventilation can exhibit a physical exert on the heart. This can be monitored by conducting a chest x ray 30-60 minutes after beginning the ventilatory cycle to observe if the thorax is compressing the heart or not.
When a patient is transitioned from conventional ventilation to HFOV a sustained state of a positive pressure inside the thoracic cavity may influence the venous return or cardiac output and impede it. The result of this would be a decrease in blood pressure or hypotension. This condition can also be further worsened if their exists a state of acidemia due to this hypotension. The solution to this problem can be to make a check and make sure that the patient is euvolemic before HFOV is initiated. Also proper arrangements should be made that when needed the patient can be conveniently volume resuscitated.
Although there exist many upsides to the use of HFOV, its use in adult patients is quite low infact rare. The reason for this maybe the lack of comfort of the medical staff in handling such an equipment, inability of dispensing the nebulized medication and the lack of mobility predisposed by it. Downside of HFOV represents in the form of its various possible complications which include disturbances in the distention of the lung, ET occlusion due to secretions, pneumothorax and compromise to the hemodynamics.
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