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What Is Mechanical Ventilation and How Does It Work

An overview of the crucial helping mechanism in the face of the current outbreak; mechanical ventilation.

What Is Mechanical Ventilation and How Does It Work
Iron Lung at Fort Sam  Articseahorse/Wikimedia Commons 

Mechanical ventilators are important tools in the care of the critically ill. Mechanical ventilation allows the body to continue receiving oxygen in situations such as surgery, recuperation from a serious illness that makes breathing difficult, or in some cases is used when patients are no longer able to breathe on their own at all. A patient is connected to a ventilator through a hollow tube that goes into the mouth and down the trachea.

  • Ventilators allow patients to both inhale oxygen and exhale carbon dioxide through mechanical means. They also provide patients with temperature and moisture controlled air through the use of a humidifier. Pressure, flow, and volume of oxygen are also controlled through mechanical ventilation. While the advances in technology that allow medical care providers to take advantage of mechanical ventilation have saved numerous lives, putting a patient on a ventilator is a serious choice due to the risk of complications.  

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Types of Mechanical Ventilation

While there are many varieties of ventilators, there are two primary classifications of mechanical ventilators; those that apply positive pressure and those that apply negative pressure. Positive pressure ventilation applies positive pressure to the airways. Negative pressure ventilation applies negative pressure to the body’s surface (the chest and abdomen. Positive pressure ventilators are more commonly used than negative-pressure ventilators. The iron lung devices made infamous by the polio epidemic are examples of negative pressure ventilators.

Iron lungs were large, cumbersome devices that encompassed the whole body except for the head and varied air pressure within the device to force breathing. Many polio patients were forced to spend their lives in hospitals, in wards lined with other patients dependent on the machines as well. Since then, smaller versions of the iron lung have emerged that cover less of the body. Despite those developments, positive pressure ventilators are still chosen more often in the treatment plans of modernity.

How Ventilators Work

Ventilators consist of several main parts. Every ventilator has an input or power source, be it electrical energy or compressed gas. It is essential that ventilators do not lose power, so some have A/C power lines with rechargeable batteries. More commonly, however, ventilators are run with compressed gas. The energy from the gas or electric source is then transmitted by a drive mechanism that controls the flow of air to and from the patient. The control system determines pressure, volume, and flow - the necessary settings of machine breathing. By monitoring a patient’s oxygen levels, heart rate, blood pressure, and respiratory rate, medical teams can make adjustments to the settings of the ventilator to meet the particular needs of the patient. 

What Patients Experience

Mechanical ventilation with machines that positive pressure involves intubation. A medical professional inserts a tube into the patient’s mouth or nose, and into their trachea. Afterwards, the tube is connected to the machine. Oftentimes, patients are given sedatives or pain medication to make them comfortable while they are on the ventilator. Any attempt at speaking and or exhaling on the part of the patient while they are intubated can cause discomfort and disturb the ventilator.

Eating is also problematic while on a ventilator because of the tube. While the ventilation process can be unnerving, many patients are sedated during the actual intubation and while using a ventilator in order to make it a more bearable experience. In critical care situations, as the patient is well enough, their care team will begin encouraging them to spend less time using the ventilator until they are able to breathe independently. This process is known as weaning. Weaning is important because of the multitude of risks faced by patients who require prolonged ventilator usage. 

Risks of Ventilation

Ventilation helps patients who are extremely ill conserve energy by helping them to breathe, or breathing for them when they cannot do so on their own. However, it is rarely an ideal long term alternative. The risks of infection, damage to the lungs, or inability to resume breathing independently are all concerning to physicians and care teams. The risk of infection from artificial ventilation can include ventilator-induced pneumonia, which can be fatal in some cases.

Other risks include airway injuries from the endotracheal tube or alveolar damage from excessive stretching of lung tissue during assisted ventilation. Additionally, ventilation can cause lung collapse. While the risks are numerous, in many cases, a ventilator provides support at a critical juncture in the medical crises of many patients. 

While mechanical ventilation has come a long way since the days of the iron lung, it is still a medical technology that has a very high level of risk for patients. Some patients have signed documents that assert their right to have mechanical ventilation eliminated from their treatment options. This is in part because mechanical ventilation prolongs the dying process. Some people due to spiritual beliefs or concern for the emotional impact on relatives, prefer to avoid life-extending treatments in the event that they are no longer able to breathe independently. On the other end of the spectrum are patients who receive a second chance at life because of this technology. 

Quadriplegics, people with neurological conditions, respiratory conditions, or other conditions that impair independent breathing may use ventilators on a long term basis as part of their care plans.

These people may require round the clock nursing care or other caregiving options to assist in keeping their ventilators in place, clean, and functioning according to the patients' needs. Because of these care services and the technology of medical ventilators, certain conditions are no longer seen as life-ending. Beyond this, people using ventilators as long term devices are in many cases able to resume their daily activities and return to work or school. Depending on the person’s remaining vocal cord function, a speech valve can be placed into the tracheostomy, or the tube itself can be deflated to allow for speech.

Ventilators for such patients have also allowed patients to be less reliant on full-time ventilation in some cases. Technology is always changing, and there are a wide variety of options for mechanical ventilation.

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