dead space ventilation positive pressure

PEEP of 5, 10, 15, and 20 cmH2O was applied in random sequence. We used the multiple inert gas elimination technique to assess the effect of positive end-expiratory pressure (PEEP) on each of these components of VD/VTCO2 in 14 pentobarbital-anesthetized dogs with increased permeability edema induced by infused oleic acid. The dead space is increased by following factors: general anesthesia, artificial airway, emphysema, age, neck extension, positive pressure ventilation, pulmonary embolus, pulmonary artery thrombus, hemorrhage, hypotension, emphysema.In acute increased-permeability edema, the Bohr physiological dead space (VD/VTCO2) can be influenced by changes in anatomic dead space, ventilation-perfusion (VA/Q) heterogeneity, shunt, and the Haldane effect. The anatomic dead space is the sum of volume exhaled during the first phase and half of volume exhaled during the second phase. The first phase has no nitrogen, the second phase nitrogen concentration increases and third phase is plateau phase. The subject breathes out and deeply inhales from 0% nitrogen gas mixture and exhales into the equipment that measures nitrogen and gas volume. Physiological dead space is calculated as follows:Īlveolar dead space is calculated as follows: Slowly the expirate is switched to Douglas bag once the respiration became steady. The rate of respiration and minute volume are recorded. The expirate is passed through the dry gas meter and into the atmosphere via two-way tap.

The latter is firmly supported in the mouth by the standard mouth piece. A nose clip is applied and the subject is asked to breathe in and out through Ruben non-return valve. The examination is carried out by subject lying on the bed supported by pillow. The anatomic dead space is measured by Fowler’s method. The anatomic dead space is the volume of gas within the conducting zone and amounts to about 2 ml/kg in the upright position. The alveolar dead space is the volume of gas within unperfused alveoli and is very negligible amount. Physiologic or total dead space is the sum total of alveolar dead space and anatomic dead space. The Dead space is the volume of breath that does not participate in the gas exchange and is the ventilation of the lungs without perfusion.

Dead space ventilation positive pressure