Mechanical ventilation
Mechanical ventilation is a medical intervention that utilizes specialized machines to assist individuals with compromised breathing, often due to illness or injury. There are two primary forms of mechanical ventilation: noninvasive and invasive. Noninvasive ventilation typically employs a pressurized mask to deliver oxygen, while invasive ventilation involves the insertion of an endotracheal tube into the trachea to provide oxygen-rich gas directly into the lungs. This process can be essential for patients who are unable to breathe independently or for those who require extra respiratory support.
The history of mechanical ventilation dates back to ancient medical theories and has evolved significantly since the development of the first ventilators in the late 19th century. Modern ventilators are equipped with advanced technology that allows healthcare providers to monitor and adjust air pressure, flow, and volume to suit individual patient needs. While mechanical ventilation is a lifesaving measure, patients may experience discomfort, particularly with invasive procedures, leading to the use of sedatives and pain management strategies. Some patients may struggle with transitioning back to independent breathing after long-term mechanical ventilation, as the respiratory muscles can weaken from disuse. Overall, mechanical ventilation plays a critical role in contemporary healthcare, particularly in acute care settings.
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Mechanical ventilation
Mechanical ventilation is the process of using specialized machinery to increase oxygen in the body. It can be accomplished noninvasively, through a pressurized mask, or invasively, through an endotracheal tube. Mechanical ventilation is used to assist individuals who have trouble breathing independently, usually as a result of some kind of illness or injury. Some individuals require mechanical ventilation to complete the entire breathing process on their behalf, while others only require assistance. Many individuals find the process of invasive mechanical ventilation unpleasant. They cannot eat, drink, or speak while the endotracheal tube is inserted. For this reason, doctors often prescribe sedatives or pain-numbing medications alongside invasive mechanical ventilation.
Background
Galen was a Greek physician active in the second century AD. He dissected animals, studied breathing, and theorized that breathing was essential for the circulation of blood. Robert Hooke, a scientist and natural philosopher, tested Galen's theories in 1667. Although he confirmed that breathing was essential for life and not just a sign of life, Hooke did not understand the purpose of breathing. In 1774, Joseph Priestley and Carl Wilhelm Scheele discovered oxygen. Soon afterward, they discovered oxygen's importance to respiration.
In the late nineteenth century, the first true ventilators were developed. These devices required the patient's body to be enclosed in the machine from the neck down. A plunger was used to decrease pressure inside the box, which caused the lungs to expand, mimicking inhalation. When the pressure was increased, the lungs contracted, mimicking exhalation. Repeating these actions mimicked the breathing process. This was called negative pressure ventilation. It developed into the commonly known "iron lung."
Doctors had trouble treating patients in iron lungs and similar machines because they could not access the patients' bodies. To solve this problem, Peter Lord invented the ventilator room, in which giant pistons made an entire room function like an iron lung. The patient's head was placed outside the room through a specialized hole in the wall. Because they were incredibly expensive, most ventilator rooms were built to hold multiple patients.
These technologies rapidly advanced in the 1950s, when polio resurged in the United States and Europe. Early on in the outbreak, most doctors believed that polio patients were dying from renal failure. However, medical researchers soon realized that patients were dying from respiratory failure. The use of mechanical ventilation drastically reduced polio fatality rates immediately.
Over the following decades, technology related to mechanical ventilation continued to advance. Improved flow delivery, exhalation valves, and computerization improved ventilators. Other improvements brought better understanding of the respiratory system.
Overview
Modern medical professionals use numerous forms of mechanical ventilation. Positive pressure ventilators use a series of tubes to deliver oxygen-rich gas to the patient through a mask or a set of nasal tubes. The network of tubes is called a patient circuit. This method is a noninvasive form of mechanical ventilation.
For more intensive care, or in specific situations that require it, doctors may order invasive mechanical ventilation. Like noninvasive mechanical ventilation, invasive mechanical ventilation utilizes a patient circuit. However, instead of delivering oxygen-rich gas through a mask or a set of nose prongs, it delivers gas through an endotracheal tube.
Endotracheal tubes are single-use, PVC tubes designed to extend down the trachea. In most emergency situations, endotracheal tubes are inserted through the mouth. However, they may be inserted through the nose or through an incision in the trachea.
Most ventilation systems include an airway pressure monitor. These sensors measure the air pressure within the tubes and the patient's airway. They also may measure the speed at which air flows and the volume of air. Many airway pressure monitors allow medical professionals to modify these conditions to increase or decrease the pressure, volume, or speed of air in the patient circuit to better suit the patient's condition.
The primary purpose of mechanical ventilation is to increase the amount of oxygen in the body by increasing the flow of oxygen to the lungs. It may be used to reduce strain on the muscles utilized in the respiratory process or to help the body remove carbon dioxide. Some patients require mechanical ventilation at all times. These patients are wholly unable to breathe on their own, often as a result of an injury to the brain or spinal cord. Other patients use mechanical ventilation to supplement weakened breathing. These patients may use mechanical ventilation at night or for a set period during the day.
The presence of a ventilator in the windpipe should not cause pain, but for some patients, it can feel very unpleasant and cause distress. Some patients experience more extreme distress than others. To help mitigate this, patients who have been prescribed invasive mechanical ventilation often receive sedatives and pain-controlling medication, too. These medications help calm the muscles of the windpipe and ease negative sensations associated with intubation.
Some patients feel as if mechanical ventilation makes it more difficult to breathe on their own. This may be caused by the muscle movement that results from intubation. To combat such muscle movements, doctors may prescribe neuromuscular blocking agents. In addition, individuals being treated with mechanical ventilation are instructed to breathe in time with the mechanical ventilator. Breathing out while the mechanical ventilator is pressing air into the body, or vice versa, will make it more difficult for the mechanical ventilator to work.
Patients who need mechanical ventilation for long periods sometimes experience negative side effects when transitioning back to independent breathing. The muscles that control respiration can weaken as a result of doing little work. These patients may find independent breathing difficult or exhausting.
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