Mechanical Ventilation Vs Continued Assisted Ventilation

Mechanical ventilation is a life-saving intervention for patients who are unable to breathe on their own. Ventilators use positive pressure to deliver oxygenated air into the lungs so that gas exchange can occur.

Mechanical ventilation is a complex topic; however, it must be understood by respiratory therapists and medical professionals who care for patients in critical condition.

This article will provide a comprehensive overview of mechanical ventilation and the basics of how ventilators work.

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What is Mechanical Ventilation?

Mechanical ventilation involves the use of a machine to help a patient who is unable to breathe spontaneously. Therefore, it is indicated for patients who are unable to maintain adequate ventilation.

Ventilation is the process of taking in oxygen during inhalation while removing carbon dioxide during exhalation.

When a patient is unable to do this on their own, a ventilator can be used to assist with or completely take over the ventilatory process.

Indications

Some of the most common reasons why a patient may require mechanical ventilation include:

Insufficient oxygenation: When a patient is not receiving enough oxygen (i.e., hypoxemia), it can impact the functionality of tissues and vital organs of the body. Mechanical ventilation can help deliver oxygen to the lungs, which is then distributed throughout the body.
Insufficient ventilation: When a patient is not removing enough carbon dioxide from their body, it results in increased acidity of the blood (i.e., respiratory acidosis). Mechanical ventilation helps the patient remove carbon dioxide during exhalation.
Acute lung injury (ALI): This is an injury to the lungs that occurs from an acute event such as sepsis, pneumonia, aspiration, or trauma.
Severe asthma: During an asthma exacerbation, the airways constrict and make it difficult to move air in and out of the lungs. This can lead to respiratory failure, which often requires ventilatory support.
Severe hypotension: Conditions that cause extremely low blood pressure, such as shock, sepsis, and congestive heart failure (CHF), often require mechanical ventilation.
Inability to protect the airway: When a patient is at risk of aspirating secretions into the lung, they may require intubation and mechanical ventilation to protect their airway.
Upper airway obstruction: Conditions that cause upper airway obstructions, such as epiglottitis and laryngeal edema, can prevent patients from being able to move air into the lungs. Therefore, mechanical ventilation can help bypass the obstruction.

In general, mechanical ventilation is indicated whenever a patient's spontaneous breathing is not adequate to sustain life.

In such a case, a ventilator would be used to provide breathing support until the patient's underlying condition is reversed.

Contraindications

A patient cannot survive without adequate ventilation and oxygenation. Therefore, there are no true contraindications for mechanical ventilation.

However, there may be some circumstances where a patient chooses not to receive mechanical ventilation, such as when they have a DNR (Do Not Resuscitate) order in place.

This means that the patient legally wishes not to receive life-saving interventions. In these cases, the patient's goals of care must be respected.

Principles of Mechanical Ventilation

A practitioner must learn and understand the principles of mechanical ventilation in order to administer support to patients in need. This includes:

Ventilation: The process of moving air into and out of the lungs.
Oxygenation: The process of absorbing oxygen into the bloodstream.
Lung compliance: The lung's ability to expand and contract.
Airway resistance: The impedance of airflow through the respiratory tract.
Deadspace ventilation: The volume of ventilated air that does not participate in gas exchange.
Respiratory failure: The inability of the lungs to oxygenate the blood or remove carbon dioxide from the body.

Each principle is important in determining the amount of ventilatory support that is delivered to the patient by the machine.

What is a Mechanical Ventilator?

A mechanical ventilator is a breathing machine that uses positive pressure to deliver ventilatory breaths to patients who are in need of assistance. The machine consists of several parts that work together to generate positive pressure that helps force air into the lungs.

Mechanical ventilation is an intervention that can provide short or long-term support while the patient's underlying condition is treated.

It is often indicated for patients with cardiopulmonary disorders but is also common in postoperative patients who are recovering from anesthesia.

How Does a Ventilator Work?

Ventilators work by using positive pressure to deliver breaths to the patients. However, an artificial airway must be inserted into the patient's trachea before being connected to the machine.

This process is known as intubation, which involves the insertion of an endotracheal tube through the mouth and into the trachea.

Once the tube is in place, it establishes a link between the patient and the ventilator so that positive-pressure breaths can be delivered.

Ventilators are not used to heal and treat a patient of their underlying disease. Rather, they are used to provide breathing support until the patient is stable and treated with medications and other modalities.

Mechanical Ventilation Benefits

There are many benefits for patients who are receiving mechanical ventilation, including the following:

Decreases work of breathing: The ventilator assists with the patient's breathing, which can help to decrease the amount of energy and work required for each breath.
Maintains adequate oxygenation: The ventilator can deliver an FiO2 of up to 100% to help with oxygenation. It also can deliver positive end-expiratory pressure (PEEP), which is helpful in patients with refractory hypoxemia.
Helps remove carbon dioxide: The ventilator can help the patient remove carbon dioxide from their body with an increased respiratory rate or tidal volume.
Provides stability: The ventilator helps keep the patient stable, allowing medications and other modalities to reverse their underlying condition.

The benefits of mechanical ventilation often far outweigh the risks, which is why it is such a common intervention in the field of respiratory care. However, there are some complications that can occur.

Mechanical Ventilation Complications

Mechanical ventilation is necessary for patients who are critically ill; however, it does come with some risks and complications, including the following:

Barotrauma: An injury to lung tissue that results in alveolar overdistention caused by increased levels of pressure.
Ventilator-associated pneumonia (VAP): A type of pneumonia that develops 48 hours or more after a patient has been intubated and placed on the ventilator.
Auto-PEEP: A complication of mechanical ventilation that occurs when a positive pressure remains in the alveoli at the end-exhalation phase of the breathing cycle.
Oxygen toxicity: A type of cell damage that can occur when a patient is exposed to high levels of oxygen for an extended period of time.
Ventilator-induced lung injury (VILI): An acute lung injury that occurs while a patient is receiving mechanical ventilatory support.

However, the risks and complications of mechanical ventilation can be minimized with proper care and monitoring by medical professionals.

Types of Mechanical Ventilation

There are four primary types of mechanical ventilation, each with its own indications, settings, contraindications, and risks. The different types include:

Positive-pressure ventilation
Negative-pressure ventilation
Invasive mechanical ventilation
Noninvasive ventilation

Positive-Pressure Ventilation

Positive-pressure ventilation is the most common type of mechanical ventilation. It's known as "conventional mechanical ventilation" and is generally what people are talking about when they say that "someone is on the ventilator."

This type works by using positive pressure that is greater than the atmospheric pressure to push air into the lungs. The air then fills the alveoli, where the exchange of oxygen and carbon dioxide takes place.

Negative-Pressure Ventilation

Negative-pressure ventilation is not as common as positive-pressure ventilation, but it may still be used in certain situations. This type works by generating negative pressure outside of the thoracic cavity that is less than atmospheric pressure.

As a result, air moves from an area of higher pressure (outside the body) to an area of lower pressure (inside the lungs). Some examples of negative-pressure ventilation include:

Iron lung: A negative-pressure ventilator that was invented in the 1920s that was primarily used to treat patients with polio.
Cuirass ventilation: A type of negative-pressure ventilation that is delivered through a tight-fitting garment that covers the chest and abdomen.

Invasive Mechanical Ventilation

Invasive mechanical ventilation is a type that involves the insertion of an artificial airway into the trachea. This establishes a direct connection between the ventilator and the patient's lungs.

There are two primary types of artificial airways that can be used:

Endotracheal tube
Tracheostomy tube

An endotracheal tube is a long, thin tube that is inserted through the nose or mouth and then passed down the throat into the trachea.

A tracheostomy tube, on the other hand, is a shorter tube that is inserted through a small incision in the neck and then directly into the trachea.

Noninvasive Ventilation

Noninvasive ventilation (NIV) is a type of ventilatory support that doesn't require the insertion of an artificial airway. It requires the use of a face mask that creates a tight seal over the patient's nose or mouth.

This allows the machine to force oxygen-rich air into the patient's lungs using positive pressure. The two primary types of NIV include:

CPAP
BiPAP

Noninvasive ventilation is commonly indicated to improve oxygenation and ventilation and to provide relief for respiratory distress prior to intubation and conventional mechanical ventilation.

Ventilator Modes

A ventilator mode is a setting that determines how the machine will deliver breaths to the patient. The characteristics of each mode determine how the ventilator functions.

Ventilator Control Variables

There are two primary control variables in mechanical ventilation:

Volume control (VC): A type of ventilation where the delivered volume can be set (i.e., controlled) by the operator. Since the delivered volume is fixed, the patient's peak inspiratory pressure (PIP) will vary depending on their lung compliance and airway resistance.
Pressure control (PC): A type of ventilation where the delivered level of pressure can be set (i.e., controlled) by the operator. Since the delivered pressure is fixed, the patient's tidal volume will vary depending on their lung compliance and airway resistance.

The primary advantage of volume-controlled ventilation is that a set volume allows the operator to regulate the patient's minute ventilation.

The primary advantage of pressure-controlled ventilation is that it protects the lungs from overinflation due to too much pressure, which prevents barotrauma and ventilator-induced lung injuries.

Types of Ventilator Modes

There are several types of ventilator modes, including the following:

Assist/Control (A/C)
Synchronous Intermittent Mandatory Ventilation (SIMV)
Pressure Support Ventilation (PSV)
Continuous Positive Airway Pressure (CPAP)
Volume Support (VS)
Control Mode Ventilation (CMV)
Airway Pressure Release Ventilation (APRV)
Mandatory Minute Ventilation (MMV)
Inverse Ratio Ventilation (IRV)
High-Frequency Oscillatory Ventilation (HFOV)

Each ventilator mode is different and has its own characteristics. This includes unique settings and how the machine will deliver breaths to the patient.

Primary Ventilator Modes

We've covered each mode in more detail in our comprehensive guide to the modes of mechanical ventilation; however, here's a brief overview of the two primary modes:

Assist/Control (A/C)
Synchronous Intermittent Mandatory Ventilation (SIMV)

Assist/Control (A/C)

The assist/control (A/C) mode is used to deliver a minimum number of preset mandatory breaths by the ventilator, but the patient can also trigger assisted breaths.

Therefore, the patient can make an effort to breathe, and the machine will use positive pressure to assist in delivering the breath.

This mode provides full ventilatory support; therefore, it is commonly used when mechanical ventilation is first initiated. It helps keep the patient's work of breathing requirement very low.

Synchronous Intermittent Mandatory Ventilation (SIMV)

The synchronous intermittent mandatory ventilation (SIMV) mode delivers a preset minimum number of mandatory breaths, but it also allows the patient to initiate spontaneous breaths in between the preset breaths.

Since the patient is able to initiate spontaneous breaths, it means they are contributing to some of their minute ventilation. Therefore, SIMV is indicated when a patient only needs partial ventilatory support.

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Ventilator Settings

Ventilator settings are the specific parameters that are set on the machine in order to provide the patient with optimal ventilation. The most common types of ventilator settings include:

Mode: The primary setting that determines how the ventilator functions.
Tidal volume: The volume of air that is delivered with each breath.
Frequency (rate): The number of breaths that are delivered per minute.
FiO2: The percentage of inspired oxygen that is being delivered to the patient.
Flow rate: The rate at which a volume of air is being delivered to the patient.
I:E ratio: The ratio of the inspiratory portion compared to the expiratory portion of the breathing cycle.
Sensitivity: The setting that determines how much effort (i.e., negative pressure) the patient must generate in order to trigger a breath to be delivered.
PEEP: Positive end-expiratory pressure that is applied at the end of the expiratory phase in order to prevent alveolar collapse.
Alarms: Ventilators are equipped with alarms that act as safety mechanisms to alert caregivers when there is a problem related to the patient-ventilator interaction.

Each ventilator setting has different characteristics that must be controlled or adjusted to determine the amount of support that is delivered to the patient.

Initiation of Mechanical Ventilation

The initiation of mechanical ventilation is a complex process that requires the coordinated efforts of doctors and respiratory therapists.

The decision to use mechanical ventilation is based on the patient's respiratory status and the underlying cause of the respiratory failure.

Initial Ventilator Settings

Once it has been determined that mechanical ventilation is needed, the operator must know how to properly input the initial ventilator settings. This includes the following:

Mode: The most common initial ventilator modes are A/C and SIMV; however, any operational mode will work when setting up the initial ventilator settings.
Tidal volume: 6–8 mL/kg of the patient's ideal body weight (IBW)
Frequency: 10–20 breaths/min
FiO2: 30–60%, or the previous FiO2 prior to intubation (up to 100%)
Flow rate: 40–60 L/min
I:E ratio: Between 1:2 and 1:4
Sensitivity: Between -1 and -2
PEEP: 4–6 cmH2O

The initial ventilator settings are set based on the patient's condition but must be adjusted as their condition changes.

For example, it's common for a patient to receive an FiO2 of 100% when they are first intubated and placed on the ventilator. However, as the patient's oxygenation status improves, the FiO2 setting should be decreased.

Artificial Airways for Mechanical Ventilation

Prior to being connected to the ventilator, a patient must first be intubated. This is a process that involves the insertion of an artificial airway into the trachea.

The two primary types of artificial airways that are used for mechanical ventilation are endotracheal tubes and tracheostomy tubes.

Endotracheal tubes are inserted through the nose or mouth and then passed through the vocal cords into the trachea. Tracheostomy tubes are inserted through a surgical incision in the neck and directly into the trachea.

Other Types of Artificial Airways

The secondary types of artificial airways that may be indicated in certain situations include the following:

Oropharyngeal airway
Nasopharyngeal airway
Laryngeal mask airway (LMA)
King laryngeal tube
Esophageal obturator airway
Esophageal gastric tube airway
Esophageal-tracheal combitube
Double-lumen endobronchial tube

Each type of artificial airway has its own advantages and disadvantages that must be considered when used during mechanical ventilation.

Drugs Used in Mechanical Ventilation

There are certain medications that can be administered during mechanical ventilation to help with patient comfort and airway management.

For example, neuromuscular blocking agents are administered to help with intubation. Sedatives are given to help decrease the patient's level of consciousness and anxiety.

Analgesics can be administered to provide relief for pain, while bronchodilators are used to help open the airways and reduce airflow resistance. Some examples of the types of drugs that are used for mechanical ventilation include:

Antiemetics
Barbiturates
Benzodiazepines
Cathartic agents
Corticosteroids
Depolarizing agents
Nondepolarizing agents
Inotropic agents
Opioid analgesics
Parasympatholytic bronchodilators
Sympathomimetic bronchodilators
Xanthine bronchodilators

Check out our full guide if you want to learn more about the drugs that are used in mechanical ventilation, where we go into more detail about each medication.

Managing a Patient on the Ventilator

Ventilator management is the process of operating a mechanical ventilator and ensuring that it delivers adequate levels of support to the patient. This includes:

Assessing oxygenation
Assessing ventilation
Assessing lung mechanics
Adjusting ventilator settings
Reviewing the patient's progress
Managing the ventilator circuit
Managing the artificial airway
Providing humidification therapy
Implementing VAP-prevention strategies
Providing nutritional support
Maintaining fluid and electrolyte balance
Documenting the results

The primary goal of mechanical ventilation is to improve the patient's oxygenation and ventilation while minimizing ventilator-induced lung injuries.

Therefore, as previously mentioned, it's important to make adjustments to the ventilator settings depending on the patient's condition.

Monitoring a Mechanically Ventilated Patient

Mechanical ventilation is a type of life support that requires close monitoring of the patient. This includes the process of assessing how the patient is responding to positive pressure ventilation.

The parameters that must be monitored when a patient is on the ventilator include:

Vital signs
Breath sounds
Chest imaging
Chest movement
Fluid balance
Blood gas results
Capnography
Cerebral perfusion pressure

Mechanical ventilation monitoring is a job duty of both respiratory therapists and nurses in the intensive care unit (ICU); however, only RTs are responsible for making adjustments to the ventilator settings.

Ventilator Alarms

Ventilator alarms are designed to notify medical professionals when there is a problem with the patient-ventilator interaction. There are several types of ventilator alarms, including:

High Pressure
Low Pressure
Low Volume
High Frequency
Apnea
High PEEP
Low PEEP

Ventilator alarms can be visual, audible, or both, depending on the mode, settings, patient's condition, and type of ventilator.

Ventilator Waveforms

Ventilator waveforms are graphical representations of the patient's breathing pattern that is displayed on the ventilator. The most common types of waveforms used to assess a patient's ventilation include:

Flow-volume loop
Pressure-volume loop
Constant flow waveform
Descending ramp flow waveform
Pressure-time waveform
Flow-time (V-t) waveform

These ventilator waveforms can be used to assess the patient's lung mechanics, ventilator settings, and response to mechanical ventilation.

Ventilator Troubleshooting

There are a number of things that can go wrong during mechanical ventilation. Therefore, ventilator troubleshooting refers to the process of identifying and resolving problems in the patient-ventilator interaction.

Some examples of potential problems during mechanical ventilation include:

Bronchospasm
Secretion buildup
Airway obstruction
Dynamic hyperinflation
Kink in the endotracheal tube
Patient biting the endotracheal tube
Improper patient positioning
Drug-induced distress
Abdominal distension
Leaks in the circuit
Inadequate oxygenation
Inadequate ventilatory support
Improper ventilator settings
Patient-ventilator asynchrony
Ventilator alarm sounding
Technical machine errors
Lung overinflation
Auto-PEEP
Excessive PEEP
Improper waveforms
Obstructed expiratory valve
Apnea due to a disconnection

Respiratory therapists must be familiar with common ventilator problems and how to resolve them quickly and efficiently. This involves assessing the situation, analyzing pertinent data, and finding a viable solution.

The primary goal is to protect the patient by ensuring that they are receiving adequate ventilation and oxygenation.

Therefore, if a problem occurs in the patient-ventilator system, it may require disconnecting the patient and delivering breaths with a manual resuscitator until the problem is resolved.

Ventilator Weaning

Weaning from mechanical ventilation is the process of slowly reducing the level of support that a patient needs in order to eventually be able to breathe on their own.

Weaning success occurs when a patient is able to tolerate spontaneous breathing for 48 hours following extubation without the need for reintubation.

There are several factors that contribute to weaning success, including:

The type of respiratory disease
The severity
The patient's age
The presence of comorbidities
The length of time spent on the ventilator

Weaning failure occurs when a patient does not pass a spontaneous breathing trial (SBT) or if there is a need for reintubation within 48 hours of being removed from the ventilator.

In general, the greater the amount of time a patient is on the ventilator, the higher the risk of weaning failure. Patients with chronic diseases, such as COPD, are also more likely to experience weaning failure.

Weaning Criteria

There are several weaning criteria that must be met before extubation and the discontinuance of mechanical ventilation are considered, including:

Adequate cough
Manageable secretions
Hemodynamic stability
Arterial blood gas (ABG)
Rate (f)
Tidal volume (VT)
Vital capacity (VC)
Minute ventilation (MV)
MIP/NIF
Maximum expiratory pressure (MEP)
Rapid shallow breathing index (f/VT)
PaO2
SaO2
PaO2/FiO2 (P/F)
Qs/Qt
P(A-a)O2
Static compliance
Airway resistance
VD/VT
Spontaneous breathing trial (SBT)

The acute condition that initially required mechanical ventilation must be resolved or significantly improved in order for weaning to be successful.

What is a Spontaneous Breathing Trial?

A spontaneous breathing trial (SBT) is a test used to assess a patient's readiness for weaning from mechanical ventilation.

It involves a period of time where limited or no support is provided by the ventilator, during which the patient's vital signs and respiratory status are closely monitored.

An SBT is considered successful if the patient is able to maintain adequate oxygenation and ventilation without any significant distress.

If the patient does not meet the required criteria, they should be placed back on the ventilator and given additional time to rest and recover.

What is Extubation?

Extubation is the process of removing an endotracheal tube from the patient's trachea and discontinuing mechanical ventilation.

The decision to perform extubation is based on the following factors:

The ability to protect the airway
The ability to maintain adequate respiratory function
The ability to manage secretions
The ability to maintain adequate oxygenation
The ability to maintain hemodynamic stability
The ability to cooperate with the medical team

If the patient meets the above criteria, extubation would be indicated, and the endotracheal tube can be removed from the trachea. This procedure is typically performed by respiratory therapists.

Neonatal Mechanical Ventilation

Neonatal mechanical ventilation is the process of delivering positive pressure to an infant's lungs for breathing support. It is indicated when the infant's respiratory efforts are insufficient to maintain adequate oxygenation and ventilation.

Mechanical ventilation in newborns is different than in adults due to anatomical differences.

For example, infants have much smaller lungs; therefore, they will require smaller tidal volumes. Additionally, the pressure needed to ventilate a neonate's lungs is much lower than in adults.

The differences in pulmonary mechanics between infants and adults require special considerations when providing mechanical ventilatory support.

FAQ

What are the Goals of Mechanical Ventilation?

Mechanical ventilation is indicated when a patient's spontaneous breathing is not adequate to sustain life. Therefore, the primary goals include:

To improve gas exchange
To reverse hypoxemia
To reverse acute respiratory failure
To provide relief for respiratory distress
To reverse respiratory muscle fatigue
To improve pulmonary mechanics
To prevent or reverse atelectasis
To improve lung compliance
To prevent lung injury
To maintain lung and airway functionality
To prevent respiratory muscular dystrophy

Each patient is different; therefore, each patient may need mechanical ventilatory support for a different reason depending on their underlying condition.

What is the Difference Between Invasive and Noninvasive Mechanical Ventilation?

Invasive mechanical ventilation is when an endotracheal tube is inserted into the trachea to establish an artificial airway for ventilatory support.

This type is indicated in patients with severe respiratory failure. It is also used for those who are unable to maintain their own airway or who are at risk of aspirating.

Noninvasive mechanical ventilation is a type of support that can be applied without the insertion of an artificial airway. This type is typically used in patients with mild to moderate respiratory distress. BiPAP and CPAP are two examples of noninvasive ventilation.

What are the Types of Lung Compliance?

Lung compliance is a measurement of how easily the lungs can expand and contract. There are two primary types:

Static
Dynamic

Static compliance is a measurement of the lung's ability to expand when there is no airflow. It is determined by the amount of pressure required to inflate the lungs at a given volume.

Dynamic compliance is a measurement of the lung's ability to expand when airflow is present. It is determined by the amount of pressure required to produce a given flow rate.

What are the Types of Deadspace Ventilation?

Deadspace ventilation is when there is airflow to the alveoli, but no gas exchange is taking place. The three primary types of deadspace include:

Anatomic deadspace: The volume of air in the conducting airways that does not participate in gas exchange.
Alveolar deadspace: The volume of air that reaches the alveoli but does not participate in gas exchange due to a lack of perfusion.
Physiologic deadspace: The sum of the anatomic and alveolar deadspace, which is the total volume of air that does not participate in gas exchange.

Deadspace is known as "wasted ventilation" because it involves inhaled air that does not participate in gas exchange due to a lack of perfusion.

What is Acute Respiratory Distress Syndrome?

Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by fluid accumulation in the alveoli and refractory hypoxemia.

This results in decreased lung compliance and severe oxygen insufficiency. The treatment for ARDS typically requires mechanical ventilation with high levels of PEEP.

What is an Acute Lung Injury?

Similar to ARDS, an acute lung injury (ALI) is a diffuse alveolar injury characterized by the accumulation of fluid in the alveoli. It is typically caused by an acute event such as sepsis, pneumonia, aspiration, or trauma.

What is Ventilator-Associated Pneumonia (VAP)?

Ventilator-associated pneumonia (VAP) is a type of pneumonia that is acquired 48 hours or more after intubation and the initiation of mechanical ventilation. Therefore, it is a hospital-acquired infection, meaning that it is not present at the time of admission.

This can be problematic because patients that develop this infection are typically already critically ill. Some of the most common causes of ventilator-associated pneumonia include:

Endotracheal tube insertion
Aspiration of bacteria
Inappropriate body positioning
Inadequate suctioning
Inadequate oral care
Circuit contamination
Inadequate weaning

Prevention is the most important aspect of care for patients at risk of ventilator-associated pneumonia. This can be accomplished through a variety of VAP-prevention techniques.

Who Can Operate a Mechanical Ventilator?

The operation of a mechanical ventilator is a highly skilled task that requires specialized training. In most cases, it should only be performed by respiratory therapists, physicians, and pulmonologists.

Managing a patient on a ventilator requires a specific license, credentials, and formal training.

In general, nurses are typically educated on the basics of mechanical ventilation. However, they are not typically trained on how to initiate or make adjustments to the ventilator settings. Therefore, this skill is not within their scope of practice.

How Long is a Patient Connected to a Ventilator?

The length of time a patient is connected to a ventilator will vary depending on the reason for intubation and the severity of their illness or injury.

In some cases, patients can be extubated and transitioned to a less invasive form of mechanical ventilation within a few days. However, other patients may require mechanical ventilation for several weeks or even months.

The decision to extubate a patient is made on a case-by-case basis. The patient's respiratory status, ability to protect their airway, and overall clinical condition are all factors that contribute to the decision.

What is Ventilator Dyssynchrony?

Ventilator dyssynchrony is when the timing of the patient's respiratory efforts is out of sync with the machine.

This increases the work of breathing and results in respiratory distress, making it difficult for the patient to breathe comfortably on the machine.

Which Vital Signs Should Be Monitored During Mechanical Ventilation?

Vital signs are a key element in the assessment of a patient who is receiving mechanical ventilation. The vital signs that should be monitored include:

Heart rate
Respiratory rate
Oxygen saturation
Blood pressure
Temperature

These vital signs provide important information about the patient's overall condition and how they are responding to mechanical ventilation.

What are the Spontaneous Ventilator Modes?

There are three modes of mechanical ventilation in which the patient must be able to breathe spontaneously before use, including:

Continuous Positive Airway Pressure (CPAP)
Pressure Support Ventilation (PSV)
Volume Support (VS)

Apnea and death can occur if any of these modes are used on a patient who is unable to breathe on their own.

This is because these modes do not provide mandatory breaths; therefore, if the patient cannot initiate a breath, they will not receive any machine-delivered breaths.

How to Improve Oxygenation in a Patient on the Ventilator?

To improve the oxygenation status of a patient who is receiving mechanical ventilatory support, the practitioner may consider the following:

Increase the FiO2
Improve circulation
Initiate CPAP
Initiate PEEP
Airway Pressure Release Ventilation (APRV)
Inverse Ratio Ventilation (IRV)
Prone positioning
Improve the patient's ventilatory status

Each of these interventions has a direct or indirect effect on the patient's arterial oxygen level (PaO2).

How to Improve the Ventilation Parameters of a Patient on the Ventilator?

To improve the ventilatory parameters of a patient who is receiving mechanical ventilation, the operator may consider the following:

Increase the frequency
Increase the tidal volume
Reduce mechanical deadspace

Decreased ventilation results in increased levels of the partial pressure of carbon dioxide in arterial blood (PaCO2), which is known as respiratory acidosis.

Therefore, in order to improve the patient's ventilatory status, it is necessary to increase the tidal volume or frequency that is delivered by the ventilator. This will help the patient to exhale more CO2 and improve their blood gas values.

Extracorporeal membrane oxygenation (ECMO) may be indicated in severe cases, which involves pumping blood outside of the body through a machine that facilitates gas exchange.

What are the Complications of Noninvasive Ventilation?

Noninvasive ventilation is helpful for patients with mild to moderate respiratory distress; however, it does have some potential complications. This includes:

Aerophagia
Airway dryness
Aspiration
Claustrophobia
Decreased cardiac output
Dry mouth
Secretion build-up inside the mask
Eye irritation from an air leak
Pressure sores from the mask

Each of these complications can be addressed with a properly-sized interface and adequate management by the caregivers.

What is the Normal PEEP in Mechanical Ventilation?

Positive end-expiratory pressure (PEEP) is the pressure that is applied to the airway at the end of exhalation. It is useful in improving oxygenation and preventing alveolar collapse.

The normal level of PEEP in mechanical ventilation is 5 cmH2O.

However, the PEEP setting may need to be increased in patients with refractory hypoxemia or severe oxygenation defects. In general, PEEP should be titrated based on the patient's response in order to maintain the PaO2 within the normal range.

What Complication is Common in Neonates Who Receive Prolonged Mechanical Ventilation at Birth?

The most common complication in neonates who receive prolonged mechanical ventilation is bronchopulmonary dysplasia (BPD).

This is a chronic lung disease that is characterized by inflammation and the development of scar tissue in the airways. Neonates who are born prematurely and have a low birth weight are at a higher risk for developing BPD.

BPD can lead to respiratory failure and death, so it is important for neonatal caregivers to be aware of the signs and symptoms of this condition. Early diagnosis and treatment are essential for the best possible outcome.

What is Flow in Mechanical Ventilation?

Flow in mechanical ventilation refers to the patient's inspiratory flow rate. It determines how fast a volume of air is delivered to the lung by the ventilator.

The flow setting can be adjusted depending on the inspiratory demands of the patient.

A normal inspiratory flow rate is set at approximately 60 L/min, although most ventilators can deliver up to 120 L/min. A higher flow rate may be useful if a patient needs a prolonged expiratory time due to the presence of an obstructive lung disease.

However, a flow rate that is set too low can result in patient-ventilator dyssynchrony and an increased work of breathing. A flow rate that is set too high can result in a decreased mean airway pressure.

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Final Thoughts

Mechanical ventilation is a life-saving intervention for patients with respiratory failure. It uses positive pressure to deliver breaths to the patient.

This facilitates the absorption of oxygen during inhalation while removing carbon dioxide from the body during exhalation.

It's important for respiratory therapists and medical professionals who work with critically ill patients to develop a good understanding of how ventilators work. This includes learning about the following:

Types of ventilators
Ventilator modes
Ventilator settings
Initiating mechanical ventilation
Airway management
Ventilator alarms and troubleshooting
Managing patients on the ventilator
Ventilator weaning

By understanding the basics of mechanical ventilation, medical professionals can provide better care for their patients and know how to respond in the event of an emergency.

Thanks for reading, and, as always, breathe easy, my friend.

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.

References

Clinical Application of Mechanical Ventilation. 4th ed., Cengage Learning, 2013.
Pilbeam's Mechanical Ventilation: Physiological and Clinical Applications. 6th ed., Mosby, 2015.
Principles And Practice of Mechanical Ventilation, Third Edition (Tobin, Principles and Practice of Mechanical Ventilation). 3rd ed., McGraw-Hill Education / Medical, 2012.
"Mechanical Ventilation – StatPearls – NCBI Bookshelf." StatPearls, www.ncbi.nlm.nih.gov/books/NBK539742.
Carpio, Andres Mora. "Ventilator Management – StatPearls – NCBI Bookshelf." StatPearls, 17 May 2020, www.ncbi.nlm.nih.gov/books/NBK448186.
"Invasive Mechanical Ventilation." PubMed Central (PMC), 1 Dec. 2018, www.ncbi.nlm.nih.gov/pmc/articles/PMC6284234.