What is Mechanical ventilation? Types, Materials, Risk Involved

What is Mechanical ventilation? Types, Materials, Risk Involved

What is a Mechanical ventilation?

 

Mechanical ventilation, or assisted ventilation, is the medical term for artificial ventilation where mechanical means are used to assist or replace spontaneous breathing. This may include a machine called a ventilator, or the breathing may be manually assisted by a qualified professional, such as an anesthesiologist, respiratory therapist (RT), Registered Nurse, or paramedic, by compressing a bag valve mask device. In most situations in intensive care units, RTs are responsible for optimizing ventilation, adjustment and weaning management.

Mechanical ventilation is called “invasive” if it involves any instrument inside the trachea by mouth, such as an endotracheal tube or the skin, such as a tracheostomy tube.  Facial or nasal masks are used for non-invasive ventilation in appropriately selected conscious patients.

The two main types of mechanical ventilation include positive pressure ventilation where air (or other gas mixture) is pushed into the lungs through the airways, and negative pressure ventilation where air is essentially being sucked into the lungs by stimulating chest movement. Apart from these two main types, there are many specific methods of mechanical ventilation, and their names have been revised over the decades as the technology continues to evolve.

The shortage of ventilators has emerged as a key aspect of the Coronavirus pandemic.

The Government has called on UK suppliers to help meet essential medical equipment demands

The Government has called on UK suppliers to help meet essential medical equipment demands

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Mechanical ventilation –  Materials

Mechanical ventilation is indicated when the patient’s spontaneous breathing is insufficient to maintain life. It is also indicated as prophylaxis for the imminent collapse of other physiological functions, or ineffective gas exchange in the lungs.

Because mechanical ventilation provides breathing support only and does not cure disease, the patient’s underlying condition should be identified and treated for resolution over time. In addition, other factors must be considered because mechanical ventilation is not without its complications

Mechanical ventilation is generally initiated to correct blood gases and reduce breathing.

Common medical signs to use include:

Acute lung injury, including acute respiratory distress syndrome (ARDS) and trauma

Apnea with respiratory arrest, including cases of drunkenness

Acute acute asthma requiring incubation

Acute or chronic respiratory acidosis, most commonly with chronic obstructive pulmonary disease (COPD) and obesity hypoventilation syndrome

Acute respiratory acidosis with partial pressure of carbon dioxide, which may be due to diaphragm paralysis due to Guillain-Barré syndrome, myasthenia gravis, motor neurone disease, spinal cord injury, or the effect of anesthetics and muscle relaxants.

What is Mechanical ventilation? Types, Materials, Risk

Noninvasive ventilation – with a ventilator providing only volume control without patient triggering.

Increased respiration as evidenced by significant tachypnea, withdrawal, and other physical signs of respiratory distress

Hypoxemia with arterial partial pressure of oxygen with supplemental fraction of oxygen induced

Hypertension including sepsis, shock, congestive heart failure
Neurological diseases such as muscular dystrophy and amyotrophic lateral sclerosis (ALS)

 

Mechanical ventilation Risk

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

Other complications include diaphragm atrophy, reduced cardiac output, and oxygen toxicity. One of the underlying complications presenting in mechanically ventilated patients is acute lung injury (ALI) / acute respiratory distress syndrome (ARDS). It is recognized that ALI / ARDS contributes significantly to patients’ morbidity and mortality.

In many healthcare systems, prolonged ventilation as part of intensive care is a limited resource (in the sense that only so many patients can receive care at any one time). It is used to support one failing organ system (lungs) and cannot reverse any underlying disease process (such as terminal cancer). For this reason, decisions can be made (sometimes difficult) about whether it is appropriate to start someone on mechanical ventilation.

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Similarly there are many ethical issues surrounding the decision to cease mechanical ventilation.

Pulmonary barotrauma is a well-known complication of positive pressure mechanical ventilation.

This includes pneumothorax, subcutaneous emphysema, pneumomediastinum, and pneumoperitoneum.
Ventilator-related lung injury (VALI) refers to an acute lung injury that occurs during mechanical ventilation. It is clinically unrecognizable from acute lung injury or acute respiratory distress syndrome (ALI / ARDS).

Atrophy using a diaphragm can result from controlled mechanical ventilation, a rapid form of atrophy that contains the diaphragmatic muscle fibers that can develop during the first day of mechanical ventilation.

Similarly there are many ethical issues surrounding the decision to cease mechanical ventilation.

Multi-person negative-pressure ventilator

Multi-person negative-pressure ventilators – at Boston Children’s Hospital, 1950s. (From Children’s Hospital – Boston)

Pulmonary barotrauma is a well-known complication of positive pressure mechanical ventilation.

This includes pneumothorax, subcutaneous emphysema, pneumomediastinum, and pneumoperitoneum.
Ventilator-related lung injury (VALI) refers to an acute lung injury that occurs during mechanical ventilation. It is clinically unrecognizable from acute lung injury or acute respiratory distress syndrome (ALI / ARDS).

Atrophy using a diaphragm can result from controlled mechanical ventilation, a rapid form of atrophy that contains the diaphragmatic muscle fibers that can develop during the first day of mechanical ventilation.

This case of atrophy in the diaphragm is also the cause of atrophy in all respiratory-related muscles during controlled mechanical ventilation.

Impaired mucocular mobility in the airways can result from positive pressure ventilation; transport of bronchial mucus is often impaired, and is associated with retention of secretions and pneumonia.

Application and duration

It can be used as a short-term measure, for example during surgery or critical illness (often when an intensive care unit is installed). It can be used at home or in a nursing or rehab setting if patients have chronic illnesses that require long-term ventilation assistance.

Because of the anatomy of the human pharynx, the larynx, and the esophagus and the circumstances that require ventilation, additional measures to protect the airway during positive pressure ventilation are often needed to allow untreated air to the trachea and avoid air. pass to the esophagus and stomach.

Patient on a ventilator amid the coronavirus pandemic

Patient on a ventilator amid the coronavirus pandemic

The common method is by inserting a tube into the trachea: intubation, which provides a clear path to the air. This can be either an endotracheal tube, inserted through the natural openings of the mouth or nose, or a tracheostomy inserted through an artificial opening in the neck.

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In other circumstances simple airway, oropharyngeal airway or laryngeal mask airway movements may be used. If the patient is able to protect his or her own airway and non-invasive ventilation or negative pressure ventilation is used then an airway attachment may not be required.

Types of ventilators

Ventilators come in many different styles and breathing styles to sustain life.

There are hand held ventilators such as luggage valve masks and anesthesia bags that require users to hold the ventilator to the surface or to an artificial airway and carry out manual breaths.

Mechanical ventilators are breathing machines that do not require operator effort and are usually computer controlled or pneumatic controlled.

Mechanical ventilators typically require power from a battery or wall outlet (DC or AC) although some respirators work on a pneumatic system that does not require power.

There are a variety of technologies available for ventilation, which fall into two main categories (and then fewer categories), both of which are the older technology of negative pressure mechanisms, and the more common positive pressure types.

Common positive pressure mechanical ventilators include:

Transport ventilators – These ventilators are small and rougher, and can be powered pneumatically or through AC or DC power sources.

Intensive care ventilators – These ventilators are larger and usually run on AC power (though almost all include a battery to facilitate transportation within facilities and as a backup in the event of a power failure).

This type of ventilator often provides greater control over a wide variety of ventilation parameters (such as respiratory rise time). Many ICU breathing machines also incorporate graphics to provide visual feedback of each breath.

Neonatal ventilators (Bubble Bubble [requires clarification]) – Designed with consideration for the premature newborn, these are a specialized subset of ICU breathing machines designed to achieve the volumes and ‘ the smaller, more precise pressures required to ventilate these patients.

Positive airway pressure ventilators (PAP) – These ventilators are specifically designed for non-invasive ventilation. This includes breathing machines for use at home to treat chronic conditions such as sleep apnea or COPD.

Mechanical ventilation

Mechanical ventilation uses several separate systems for ventilation referred to as the mode. There are modes in many different presentation concepts but each mode falls into one of three categories; volume cycling, [need clarification] weight cycling,  spontaneous cycling. [clarification required] In general, the choice of which mechanical ventilation method to use for a particular patient is based on the familiarity of clinicians with the modes and availability of equipment at a particular institution.

Positive pressure

The design of modern positive-pressure airstrips was largely based on technical advances by the army during World War II to supply oxygen to high altitude fighter pilots. Such ventilators replaced the iron lungs with the development of secure endotracheal tubes with high-pressure / low-pressure cuffs. Positive pressure breathing machines rose in popularity during the polio epidemic in the 1950s in Scandinavia and the United States and marked the beginning of modern ventilation therapy.

Positive pressure by manual delivery of 50% oxygen through a traceostomy tube led to a lower mortality rate among patients with polio and respiratory paralysis. However, due to the man power needed for such manual intervention, mechanical positive pressure breathing machines became more and more popular.

Negative pressure machines

Negative pressure mechanical ventilators are produced in small, field-like and larger formats. The dominant design of the smaller devices is called a cuirass, a shell-like unit used to create negative chest pressure only using a combination of a fitting shell and a soft bladder.

In recent years, this device has been manufactured using various size polycarbonate shells with multiple seals, and a high pressure oscillation pump to maintain biphasic cuirass ventilation.

Its main use has been in patients with neuromuscular disorders who have some residual muscular function. in Oxford.

Intermittent pressure ventilator in the abdomen

Another type is the intermittent abdominal pressure breathing machine that exerts pressure externally through a swollen bladder, forcing exhalation, sometimes called exsufflation.

The first such apparatus was the Bragg-Paul Pulsator. The name of one such device, the Pneumobelt made by Puritan Bennett to some extent, has become the generic name of the type.

Breath distribution mechanisms

Trigger

The trigger is what causes breath to be delivered by a mechanical ventilator. Respirations can be triggered by a patient taking his or her own breath, a ventilator operator pressing a breath button manually, or by the ventilator based on the specific breath rate and ventilation method.

Cycling

The cycle is what causes the breath to transition from the breathing phase to the breathing phase. A mechanical respirator can breathe after a certain time is reached, or a preset flow is reached or a percentage of the maximum flow distributed during a breath depending on the breath type and settings. Inhalers can also be cycled when an alarm condition is reached as a high pressure limit, which is a main strategy for pressure-regulated volume control.

Limit

Limit is how the breath is controlled. Respirations can be limited to a certain maximum circuit pressure or a certain maximum flow.

Exhalation of breath

Breathing in mechanical ventilation is almost always passive. The ventilator respiratory valve is opened, and respiratory flow is allowed until basic pressure (PEEP) is reached. Respiratory flow is determined by patient factors such as compliance and resistance.

Respiratory monitoring

One of the main reasons why a patient is admitted to an ICU is to provide mechanical ventilation. Patient monitoring in mechanical ventilation has many clinical applications: Improving understanding of pathophysiology, assisting with diagnosis, guiding patient management, avoiding complications and assessing trends.

Most modern breathing machines have basic monitoring equipment. There are also monitors that work independently of the ventilator that allow measurement of patients after the ventilator is removed, such as a T-tube test.

History

The Greek doctor Galen may have been the first to describe mechanical ventilation: “If you take a dead animal and blow air through its larynx, you fill its bronchi and watch its lungs reach maximum attention. In 1908 George Poe showed its mechanical respirator. by asphyxiating dogs and apparently bringing them back.

 

 

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REF : Wikipedia

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