![]() These adverse effects include inflammatory changes within the alveoli, rupture of alveolar septae, emphysema and pneumothorax. This creates a problem, however, as numerous experimental studies in multiple species have been published confirming adverse effects in the lungs if airway pressures exceed 30 cm H 2O. When the lungs are abnormal or diseased they become less compliant, and if 'normal' tidal volumes (10-15 ml/kg) are delivered to the airway, since the lungs are stiffer than normal, the airway pressures may reach values as high as 50 or 60 cm H 2O. In animals with normal lungs, this is not a problem, as the low end of this airway pressure range will usually be achieved if the patient is ventilated with tidal volumes of 10-12 ml/kg. General recommendations suggest that during positive pressure ventilation we should aim to achieve a peak airway pressure of 10-20 cm H 2O. ![]() Ventilator Settings in Animals with Lung Disease Furthermore, PPV is not necessarily a benign procedure, since inappropriately delivered PPV can result in worsening of lung disease and hasten the death of the patient. In general, we believe that better outcomes may be achieved if PPV is initiated early, rather than waiting until the animal is moribund before providing aggressive respiratory support. Animals with elevated PaCO 2 (> 50 mmHg), those with PaO 2 values less than 55 mmHg on oxygen supplementation, or those with obvious ongoing respiratory distress or paradoxical respiration despite oxygen supplementation, are candidates for PPV. The decision to initiate PPV is made based on the clinical condition of the animal and the degree of dyspnea, the arterial blood gas results and response to oxygen supplementation while spontaneously breathing, the prognosis, and the wishes of the owner. As criticalists, our job is to recognize the patients who will most benefit, and then to apply positive pressure ventilation in such a way as to minimize its adverse effects and therefore optimize patient outcome. Despite all of these drawbacks, it provides a wonderful means of life support that can truly make the difference between life and death. Positive pressure ventilation (PPV) is invasive, time-consuming, often frustrating, and consumes tremendous resources, both financial and emotional. Books & VINcyclopedia of Diseases (Formerly Associate).VINcyclopedia of Diseases (Formerly Associate). ![]()
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