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Partial Liquid VentilationIndications
The main indication for PLV is respiratory distress syndrome (RDS) in infants, secondary to surfactant deficiency. RDS can be caused by numerous factors that include, meconium aspiration, premature lungs with inadequate surfactant production, and hyaline membrane disease.
Surfactant plays an important role in reducing surface tension of the alveoli. A reduction in surfactant will make the lung more difficult to expand, therefore increasing the pressures needed to inflate the lung. If a patient were on a ventilator and had decreased surfactant, ventilatory pressures would need to be increased to maintain adequate volumes. Pressures that exceed 30 cmH2O could cause damage to the lungs. Inadequate lung expansion will lead to a decrease in oxygen levels and an increase in arterial carbon dioxide levels.
PFCs may be indicated to deliver some medications such as antibiotics, bronchodilators, vasodilators, and surfactants to areas that are not reachable by standard ventilation or liquids. Also, since PFC is a heavy liquid, mucous and foreign bodies are displaced and ride on top of the PFC. The removal of these substances help reduce the chance of a person getting pneumonia.
Complications
Partial liquid ventilation has seen very successful results. There have only been a few documented complications. These complications include pneumothorax, mucous plugging of the endotracheal tube, and less commonly, flurothorax. Flurothorax is PFCs that have escaped into the surrounding pleural space. PFCs can remain in the lung or body tissues for up to three years but there has been no data to show this as a negative effect.
Total vs. Partial Liquid Lung Ventilation
Total liquid lung ventilation or Tidal liquid ventilation was performed as the first liquid ventilation of any kind. However, it was not as successful as the current experiences with partial liquid ventilation. Tidal lung ventilation is total liquid ventilation. Instead of air being moved into and out of the lungs, a special "ventilator" moves a type of PFC into and out of the lungs. During this time, the patient must be sedated and paralyzed to decrease their anxiety. During inspiration, the ventilator delivers oxygen rich PFC to the lungs. Carbon dioxide is removed during exhalation. In liquid filled lungs, pulmonary blood flow is more uniformly distributed than in gaseous ventilation. When compared to West's three zone theory of the lungs, liquid ventilation essentially abolishes the 3 zones, making the lung one zone eliminating the liquid/air interface. This results in an increase in pulmonary vascular resistance.
The main problem with TLV has been the absence of mechanical technology to deliver, warm, and oxygenate the PFC. The human lung also presents resistance to the movement of a high density fluid which increases the time constant of the lung. Until the technology is reached to overcome these limitations, TLV is only experimental and cannot be used for treatments.
PLV
Partial liquid lung ventilation or PLV, has been used recently for treatment of pediatric patients in respiratory distress syndrome. During the initial studies it had great success with little or no long term side effects. With the new phase 3 studies, more and more adult patients are receiving perflubron and showing success also. PLV differs from TLV in that a much smaller amount of PFC is instilled into the lungs. Ventilation is then performed with a conventional gas ventilator.
PLV does not require any additional devices or an understanding of the physics of liquid flow thorough the airways, ETT and liquid ventilation devices. PLV is fairly simple to understand.PFC is administered to the level of the patient's functional residual capacity. As the PFC enters the lungs, it spreads throughout the airways and into the alveoli. This distribution aids in the recruitment of other alveoli.
The PFC then essentially acts as an alveolar-capillary membrane through which oxygen and carbon dioxide readily diffuse.
