User:Pulmonological/sandbox

{{{User sandbox}} Mechanical ventilation is a process that utilizes an automatic machine designed to provide all or part of the work the body must produce to move gas into and out of the lungs. The machine utilized to automate this system is called a mechanical ventilator. The act of moving air into and out of the lungs is called breathing or ventilation.

Negative-pressure ventilator
Any negative pressure ventilator.

Conventional ventilator
Any positive pressure ventilator delivering Vf <150.

High-frequency ventilator
Any ventilator able to deliver a Vf >150.

Indications
Mechanical ventilation is indicated when the patient's spontaneous ventilation is inadequate to maintain life. It is also indicated as prophylaxis for imminent collapse of other physiologic functions, or ineffective gas exchange in the lungs. Because mechanical ventilation only serves to provide assistance for breathing and does not cure a disease, the patient's underlying condition should be correctable and should resolve over time. In addition, other factors must be taken into consideration because mechanical ventilation is not without its complications

Complications
Mechanical ventilation is often a life-saving intervention, but carries many potential complications including pneumothorax, airway injury, alveolar damage, and ventilator-associated pneumonia.

In many healthcare systems prolonged ventilation as part of intensive care is a limited resource (in that there are only so many patients that can receive care at any given moment). It is used to support a single failing organ system (the lungs) and cannot reverse any underlying disease process (such as terminal cancer). For this reason there can be (occasionally difficult) decisions to be made about whether it is suitable to commence someone on mechanical ventilation. Equally many ethical issues surround the decision to discontinue mechanical ventilation.

Sedation risk
Patients may be given sedatives to make them more comfortable while the ventilator pushes air in and out of the lungs. These medications make patients sleepy and help them forget unpleasant experiences. The medications can build up in the body and the patient may remain in a deep sleep for hours to days, even after the medicine is stopped.

Pneumothorax risk
The mechanical ventilator pushes air into the lungs. It is possible for a part of the lung to get over-expanded which can injure it. Air sacs may leak air into the chest cavity and cause the lung to collapse. If this air leak happens, clinicians can place a tube in the chest between the ribs to drain out the air leaking from the lung. The tube allows the lung to re-expand and seal the leak. Rarely, collapse of the lung can cause death.

Infection risk
The endotracheal tube in the windpipe makes it easier for bacteria to get into the lungs. As a result, the lungs develop an infection called pneumonia. The risk of pneumonia is about 1% for each day spent on the ventilator. Pneumonia can often be treated with antibiotics. Sometimes the pneumonia can be severe or difficult to treat because of resistant bacteria.

Volume control
Volume control results in a more even distribution of ventilation when compared to pressure control. Volume control distributes equally among lung units with a different time constant where the units have equal resistances but unequal compliance, as seen in acute respiratory distress syndrome.

Volume controlled continuous mandatory ventilation (VC-CMV) is indicated when it is necessary to maintain precise regulation of minute volume or a blood gas parameter such as the PaCO2 in a patient who has minimal or absent respiratory effort. In CMV the ventilator makes no attempt to synchronize with the patient respiratory effort.

Spontaneous control
CPAP and BPAP

Rehabilitation
text soon

History
The Roman physician Galen may have been the first to describe mechanical ventilation: "If you take a dead animal and blow air through its larynx [through a reed], you will fill its bronchi and watch its lungs attain the greatest distention." Vesalius too describes ventilation by inserting a reed or cane into the trachea of animals. In 1908 George Poe demonstrated his mechanical respirator by asphyxiating dogs and seemingly bringing them back to life.

Economics
For patients with acute respiratory failure, mechanical ventilation provides the most definitive life-sustaining therapy. Because of the intense resources required to care for these patients, its use accounts for considerable costs. There is great societal need to ensure that use of mechanical ventilation maximizes societal benefits while minimizing costs, and that mechanical ventilation, and ventilator support in general, is delivered in the most efficient and cost-effective manner.

ARDS Clinical Network
In order to work toward the development of effective evidence-based therapy for Acute Respiratory Distress Syndrome (ARDS), the National Heart, Lung, and Blood Institute, National Institutes of Health, initiated a clinical network to carry out multi center clinical trials of ARDS treatments. The ARDS Network was established as a contract program in 1994 following a national competition.