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.
While mechanical ventilation is a complex topic, it’s one that must be understood by respiratory therapists and medical professionals who care for patients in critical condition.
This article provides a comprehensive overview of mechanical ventilation and breaks down the basics of how ventilators work.
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What is Mechanical Ventilation?
Mechanical ventilation is a medical procedure that assists or replaces spontaneous breathing by using a machine called a ventilator. It delivers air to the lungs, usually through a tube inserted into the trachea, ensuring adequate oxygenation and carbon dioxide removal for patients unable to breathe independently.
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.
Note: 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.
Given the essential nature of maintaining sufficient ventilation and oxygenation, there are no absolute contraindications to mechanical ventilation.
Nonetheless, certain situations may lead a patient to decline mechanical ventilation.
This is often seen in the context of a Do Not Resuscitate (DNR) order, where the patient has legally expressed a preference against receiving life-sustaining treatments.
In such instances, it’s imperative to honor the patient’s healthcare directives and align medical interventions with their established goals of care.
Principles of Mechanical Ventilation
A practitioner must learn and understand the principles of mechanical ventilation in order to administer support to patients in need.
- 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.
Note: 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 medical device designed to assist or fully control a patient’s breathing when they are unable to do so on their own. It works by delivering air, often enriched with oxygen, into the lungs through a tube placed in the patient’s airway.
The ventilator can be set to control the rate, volume, and pressure of air delivered, and it monitors various parameters to ensure the patient’s respiratory needs are met.
Ventilators are used in intensive care units, during surgery under general anesthesia, and for long-term care in chronic respiratory failure cases.
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 and involves inserting an endotracheal tube through the nose or mouth 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.
Benefits of Mechanical Ventilation
Mechanical ventilation offers several critical benefits, particularly for patients with severe respiratory issues.
These benefits include:
- Decreases Work of Breathing: By taking over the breathing process, the ventilator significantly reduces the energy and effort the patient needs to expend on each breath, facilitating recovery and conservation of energy.
- Maintains Oxygenation: The device is capable of administering a high concentration of oxygen (up to 100% FiO2), ensuring optimal oxygenation. Additionally, it can provide positive end-expiratory pressure (PEEP), crucial for enhancing oxygenation in patients with persistent low oxygen levels.
- Facilitates Carbon Dioxide Removal: The ventilator aids in efficiently expelling carbon dioxide by adjusting the respiratory rate or tidal volume, crucial for maintaining the body’s acid-base balance.
- Ensures Stability: By stabilizing breathing, the ventilator creates a conducive environment for the body, allowing other treatments and medications to more effectively address the underlying condition.
Note: While mechanical ventilation is life-saving and has these benefits, it’s also associated with risks and complications, and its use is typically a complex decision made by a medical team, considering the patient’s overall condition and prognosis.
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.
Note: 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 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 is less common than 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.
The primary types artificial airways used during mechanical ventilation include:
- Endotracheal Tube: A long, thin tube that is inserted through the nose or mouth and then passed down the throat into the trachea.
- Tracheostomy Tube: A shorter tube that is inserted through a small incision in the neck and then directly into the trachea.
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:
Note: Noninvasive ventilation is commonly indicated to improve oxygenation and ventilation and to provide relief for respiratory distress prior to intubation and conventional mechanical ventilation.
A ventilator mode refers to the way a mechanical ventilator assists a patient with breathing. Each mode is designed to suit different patient needs and conditions, providing varying levels of support.
The mode dictates how the ventilator delivers breaths, synchronizes with the patient’s own breathing efforts, and responds to the patient’s respiratory demands.
Ventilator Control Variables
Mechanical ventilation is primarily regulated through two control variables:
- Volume Control (VC): This ventilation mode allows the healthcare provider to preset the volume of air delivered to the patient’s lungs. As the delivered volume remains constant, the peak inspiratory pressure (PIP) may fluctuate based on the patient’s lung compliance and airway resistance. The key benefit of VC is the assurance of consistent minute ventilation, enabling precise management of the patient’s respiratory gas exchange.
- Pressure Control (PC): In this mode, the operator sets a specific pressure level to be achieved with each breath. While the pressure is maintained consistently, the actual volume of air the patient receives can vary, influenced by the lung compliance and airway resistance characteristics of the individual. The principal advantage of PC is the safeguard it provides against overinflation of the lungs, thereby minimizing the risk of barotrauma and other ventilator-induced lung injuries, as it prevents excessive pressure buildup within the lungs.
Note: Both control variables are integral to tailoring mechanical ventilation to meet each patient’s unique respiratory needs, ensuring optimal support while mitigating the risks of potential complications.
Types of Ventilator Modes
The primary ventilator modes used in clinical settings include:
- 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)
Note: Each mode offers specific benefits and is chosen based on the patient’s respiratory mechanics, gas exchange requirements, and the overall goals of ventilation, whether it’s full respiratory support or assistance during a weaning process.
Primary Ventilator Modes
The two primary modes of mechanical ventilation include:
- Assist/Control (A/C)
- Synchronous Intermittent Mandatory Ventilation (SIMV)
The assist/control (A/C) mode allows the ventilator to deliver a minimum number of preset mandatory breaths, 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.
Ventilator settings are the adjustable parameters on a mechanical ventilator that control how the machine assists with a patient’s breathing.
These settings are tailored to meet the individual respiratory needs of the patient and can be adjusted by healthcare professionals based on the patient’s condition and response to treatment.
Key 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.
Note: These settings are critical for ensuring the ventilator provides optimal respiratory support, maximizing the benefits while minimizing the risks of complications. Regular monitoring and adjustment of these settings are essential parts of ventilator management in critical care.
Initiation of Mechanical Ventilation
Initiating mechanical ventilation is a critical procedure often performed in emergency or intensive care settings when a patient’s respiratory function is compromised.
Initial Ventilator Settings
Setting up a mechanical ventilator requires careful consideration of the patient’s individual needs and respiratory status.
Initial ventilator settings are typically based on the patient’s ideal body weight (IBW), the underlying cause of respiratory failure, and the goal of ventilation.
Here are the common parameters and typical initial settings:
- 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
Note: These initial settings are a starting point and must be fine-tuned based on continuous assessment of the patient’s respiratory status, blood gas analysis, and overall clinical condition. The goal is to provide adequate ventilation and oxygenation while minimizing the potential for lung injury and other complications.
Artificial Airways for Mechanical Ventilation
Artificial airways are essential components of mechanical ventilation, providing a secure and patent route for the delivery of oxygen and ventilatory support.
There are several types of artificial airways, each suited for different clinical scenarios and durations of use.
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
In addition to the primary artificial airways, there are other specialized types designed for specific clinical situations or patient needs.
- 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
Note: Each of these devices serves a specific purpose and is chosen based on the patient’s condition, the clinical setting, and the level of airway control or isolation required. The use of these devices often requires specific training and expertise to ensure they are used safely and effectively.
Drugs Used in Mechanical Ventilation
During mechanical ventilation, various drugs are used to manage pain, anxiety, and ensure patient-ventilator synchrony.
These medications help make the process more comfortable for the patient and facilitate optimal ventilation.
Common categories and examples of these drugs include:
- Cathartic agents
- Depolarizing agents
- Nondepolarizing agents
- Inotropic agents
- Opioid analgesics
- Parasympatholytic bronchodilators
- Sympathomimetic bronchodilators
- Xanthine bronchodilators
Summary: Neuromuscular blocking agents are administered to help with intubation, and sedatives are given to 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.
Managing a Patient on the Ventilator
Managing a patient on a ventilator involves a multidisciplinary approach to ensure the patient’s safety, comfort, and progression towards recovery.
Here are the key aspects of ventilator management:
- 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
Note: Managing a patient on a ventilator is complex and requires a careful, patient-centered approach. Regular reassessment and adjustment of the care plan are essential to ensure optimal outcomes.
Monitoring a Mechanically Ventilated Patient
Monitoring a mechanically ventilated patient is crucial for ensuring effective ventilation, identifying potential complications early, and guiding adjustments in ventilator settings or overall management.
Here are the parameters that must be monitored when a patient is on the ventilator:
- Vital signs
- Breath sounds
- Chest imaging
- Chest movement
- Fluid balance
- Blood gas results
- Cerebral perfusion pressure
Note: Regular, comprehensive monitoring is essential for the optimal management of mechanically ventilated patients. It allows for timely interventions and adjustments based on the patient’s evolving condition.
Ventilator alarms are critical safety features on mechanical ventilators designed to alert healthcare providers to potential problems or changes in the patient’s condition or the ventilator function.
These alarms are intended to prompt immediate assessment and intervention to ensure the patient’s safety and the effectiveness of ventilation.
Common ventilator alarms include:
- High Pressure
- Low Pressure
- Low Volume
- High Frequency
- High PEEP
- Low PEEP
Note: Healthcare providers must respond promptly to ventilator alarms, systematically assess both the patient and equipment, and address the underlying cause to ensure patient safety and effective ventilatory support.
Ventilator waveforms are graphical representations of respiratory variables displayed on a mechanical ventilator’s screen. They provide real-time visual feedback on the patient’s respiratory status and the interaction between the patient and the ventilator.
Analyzing these waveforms helps clinicians assess ventilator settings, recognize patient-ventilator synchrony or asynchrony, and identify potential issues.
The primary types of ventilator waveforms include:
- Flow-volume loop
- Pressure-volume loop
- Constant flow waveform
- Descending ramp flow waveform
- Pressure-time waveform
- Flow-time (V-t) waveform
Ventilator waveforms are a critical component of ventilator management, providing a dynamic and visual insight into respiratory mechanics and the effectiveness of ventilatory support.
Proper interpretation of these waveforms is essential for optimizing patient care and ventilator settings.
Ventilator troubleshooting is essential in managing mechanically ventilated patients, as it involves identifying and rectifying issues that can compromise patient safety and the effectiveness of ventilation.
Some examples of potential problems that can occur during mechanical ventilation include:
- 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
- Excessive PEEP
- Improper waveforms
- Obstructed expiratory valve
- Apnea due to a disconnection
Troubleshooting ventilator issues requires a systematic approach that considers both the patient and the equipment. Swift identification and correction of problems are crucial to ensuring effective ventilation and patient safety.
The primary objective is to ensure that the patient receives sufficient ventilation and optimal oxygen delivery.
If a problem arises in the patient-ventilator interface, it may become necessary to detach the patient from the ventilator and temporarily administer breaths using a manual resuscitation bag, ensuring uninterrupted respiratory support until the underlying issue is rectified.
Ventilator weaning is the gradual process of reducing and eventually discontinuing mechanical ventilation, transitioning the patient to breathe independently without the assistance of the ventilator.
This process is critical for patients who have been on mechanical ventilation for an extended period.
Weaning success occurs when a patient is able to tolerate spontaneous breathing for 48 hours following extubation without the need for reintubation.
Here are the factors that contribute to weaning success:
- 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 transpires when a patient either fails to successfully complete a spontaneous breathing trial (SBT) or requires reintubation within 48 hours after detachment from the ventilator.
Typically, the likelihood of weaning failure increases with the duration of mechanical ventilation; prolonged dependence on ventilatory support often indicates a more challenging weaning process.
Additionally, individuals with chronic conditions like COPD are at an increased risk of encountering difficulties during the weaning phase due to their compromised respiratory function.
Weaning from mechanical ventilation involves a set of clinical indicators that suggest a patient is ready to start reducing their dependence on the machine.
Meeting these criteria is essential before initiating a spontaneous breathing trial (SBT) or gradually decreasing ventilatory support.
Common weaning criteria include:
- Adequate cough
- Manageable secretions
- Hemodynamic stability
- Arterial blood gas (ABG)
- Rate (f)
- Tidal volume (VT)
- Vital capacity (VC)
- Minute ventilation (MV)
- Maximum expiratory pressure (MEP)
- Rapid shallow breathing index (f/VT)
- PaO2/FiO2 (P/F)
- Static compliance
- Airway resistance
- Spontaneous breathing trial (SBT)
Meeting these criteria indicates that the patient might be ready to undergo a spontaneous breathing trial, marking the beginning of the weaning process.
For weaning from mechanical ventilation to be successful, the acute medical condition that initially necessitated respiratory support should either be completely resolved or show substantial improvement.
What is a Spontaneous Breathing Trial?
A spontaneous breathing trial (SBT) is a test to determine a patient’s readiness to be weaned off mechanical ventilation and breathe independently.
During an SBT, the mechanical support is reduced or temporarily disconnected, allowing the patient to breathe on their own while still being closely monitored.
An SBT is considered successful if the patient is able to maintain adequate oxygenation and ventilation without significant distress.
If the patient does not meet the required criteria, he or she should be placed back on the ventilator and given additional time to rest and recover.
What is Extubation?
Extubation is the process of safely removing an endotracheal tube, which is inserted through the mouth or nose into the trachea to establish a stable airway for mechanical ventilation.
The decision to extubate is based on several critical factors, ensuring the patient’s readiness to breathe independently:
- Airway Protection: The patient must demonstrate the ability to protect their airway, preventing aspiration of secretions into the lungs.
- Respiratory Function: Adequate strength and function of the respiratory muscles are required to ensure the patient can breathe effectively without assistance.
- Secretion Management: The patient should be able to effectively clear secretions without risk of airway obstruction.
- Oxygenation: The patient must maintain satisfactory oxygen levels without excessive support from the ventilator.
- Hemodynamic Stability: The patient’s cardiovascular system should be stable, indicating they can tolerate the potential stress of extubation.
- Cooperation with Medical Team: The patient should be able to understand and cooperate with the healthcare team’s instructions during and after the procedure.
Extubation is considered appropriate when the patient meets these criteria, signifying their readiness to have the endotracheal tube safely removed from their trachea.
This procedure is typically carried out by skilled respiratory therapists, in close collaboration with the rest of the medical team.
Neonatal Mechanical Ventilation
Neonatal mechanical ventilation is a specialized medical intervention used in neonatal intensive care units to assist or fully support the breathing of newborns who are unable to breathe adequately on their own.
This delicate process is tailored to the unique physiology of infants, particularly premature babies with underdeveloped lungs.
The ventilators used are designed to deliver very small, precise volumes of air to protect the fragile neonatal lungs from injury.
The settings and modes of ventilation are carefully selected and constantly monitored to ensure optimal oxygenation and minimal stress on the infant’s respiratory system.
Successful neonatal mechanical ventilation requires a multidisciplinary approach involving neonatologists, nurses, and respiratory therapists to ensure the best possible outcomes for these vulnerable patients.
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FAQs About Mechanical Ventilation
What are the Goals of Mechanical Ventilation?
The primary purpose of mechanical ventilation is to assist or replace a patient’s natural breathing when it’s insufficient to sustain life.
The main objectives 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
Note: Given the unique nature of each patient’s condition, the specific reasons for requiring mechanical ventilation can vary. The approach is customized to address the individual needs and underlying issues of each patient.
What is the Difference Between Invasive and Noninvasive Mechanical Ventilation?
Invasive and noninvasive mechanical ventilation are two approaches to providing respiratory support.
Invasive mechanical ventilation involves inserting an endotracheal tube through the patient’s nose or mouth or a tracheostomy tube directly into the trachea to deliver oxygen and ventilation directly to the lungs.
This method is typically used for severe respiratory failure or when a patient requires long-term ventilation.
Noninvasive mechanical ventilation, on the other hand, uses a mask or similar interface to deliver positive pressure to the airways without the need for intubation.
It’s often used for patients with less severe respiratory distress or as a step down from invasive ventilation.
What are the Types of Lung Compliance?
Lung compliance, a measure of the lung’s ability to expand, includes two primary types:
- Static Compliance: Assesses lung elasticity when there is no air movement, important for evaluating conditions affecting lung tissue like pulmonary fibrosis or ARDS.
- Dynamic Compliance: Measures compliance during breathing cycles, factoring in airway resistance, crucial for conditions like asthma or COPD.
What are the Types of Deadspace Ventilation?
Deadspace ventilation involves areas where air does not engage in gas exchange. The primary types include:
- Anatomical Deadspace: Air in respiratory passages that does not reach the alveoli.
- Alveolar Deadspace: Air in alveoli that does not participate in gas exchange, often due to blood flow issues.
- Physiological Deadspace: The total sum of anatomical and alveolar deadspace, representing all the air not used in gas exchange.
Note: 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?
Acute lung injury (ALI) is a condition characterized by sudden lung inflammation and alveolar damage that results in a rapid onset of respiratory distress.
It’s less severe than ARDS but involves similar symptoms like difficulty breathing and low blood oxygen levels.
Causes include pneumonia, trauma, or inhalation of harmful substances.
What is Ventilator-Associated Pneumonia (VAP)?
Ventilator-associated pneumonia (VAP) is a hospital-acquired infection that develops at least 48 hours after the initiation of mechanical ventilation.
It’s a serious complication that can result in a prolonged hospital stay, increased healthcare costs, and a higher risk of morbidity and mortality.
Some of the most common causes include:
- Endotracheal tube insertion
- Aspiration of bacteria
- Inappropriate body positioning
- Inadequate suctioning
- Inadequate oral care
- Circuit contamination
- Inadequate weaning
Note: Prevention is the most important aspect of care for patients at risk of ventilator-associated pneumonia, which is accomplished through a variety of VAP-prevention techniques.
Who Can Operate a Mechanical Ventilator?
Operating a mechanical ventilator requires specialized knowledge and skills. It’s typically managed by trained healthcare professionals such as respiratory therapists, physicians, and pulmonologists.
These professionals are trained in setting up the ventilator, adjusting settings based on patient needs, and monitoring the patient’s response to ventilatory support.
How Long is a Patient Connected to a Ventilator?
The duration a patient remains connected to a ventilator varies widely and depends on the underlying reason for ventilation, the patient’s response to treatment, and their overall condition.
Some patients may require ventilation for only a few hours during surgery, while others, especially those with severe respiratory conditions, may need it for weeks or even longer.
Note: The goal is always to wean the patient off the ventilator as soon as it’s safe to do so.
What is Ventilator Dyssynchrony?
Ventilator dyssynchrony occurs when there’s a mismatch between the patient’s spontaneous breathing efforts and the mechanical support provided by the ventilator.
This can lead to increased work of breathing, discomfort, and potentially adverse outcomes. Types of dyssynchrony include ineffective triggering, double triggering, and auto-triggering.
Managing dyssynchrony involves adjusting ventilator settings, optimizing sedation, and ensuring the patient’s comfort and synchrony with the ventilator.
Which Vital Signs Should Be Monitored During Mechanical Ventilation?
During mechanical ventilation, it’s crucial to monitor several vital signs to ensure patient safety and optimal ventilation.
- Heart rate
- Respiratory rate
- Oxygen saturation
- Blood pressure
Note: Monitoring these parameters helps in the timely detection and management of potential complications or adjustments in ventilator settings.
What are the Spontaneous Ventilator Modes?
Spontaneous ventilator modes are settings that allow the patient to initiate and control their breathing efforts while receiving support from the ventilator.
Common spontaneous modes include:
- Continuous Positive Airway Pressure (CPAP)
- Pressure Support Ventilation (PSV)
- Volume Support (VS)
These modes are typically used during the weaning process or for patients who require partial respiratory support.
It’s important to understand that in certain ventilator modes, if a patient is unable to initiate their own breaths, they may not receive any assistance from the machine.
These modes rely on the patient’s ability to start a breath, meaning that without spontaneous breathing effort, the ventilator will not deliver breaths.
Consequently, patients who can’t breathe independently are at risk of apnea and potentially life-threatening consequences if using these specific modes.
It’s essential for these patients to be on ventilator settings that provide automatic, machine-delivered breaths to ensure their safety.
How to Improve Oxygenation in a Patient on the Ventilator?
Improving the oxygenation status of a patient who is receiving mechanical ventilatory support involves the following strategies:
- 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
Note: These interventions have 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?
Improving the ventilatory parameters of a patient receiving mechanical ventilation involves the following strategies:
- Increase the frequency
- Increase the tidal volume
- Reduce mechanical deadspace
Decreased ventilation results in increased PaCO2 levels, which is known as respiratory acidosis.
Therefore, to improve the patient’s ventilatory status, the tidal volume or frequency delivered by the ventilator must be increased.
This will help the patient exhale more CO2 and improve their blood gas values.
Extracorporeal membrane oxygenation (ECMO) is 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.
- Airway dryness
- Decreased cardiac output
- Dry mouth
- Secretion build-up inside the mask
- Eye irritation from an air leak
- Pressure sores from the mask
Note: 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?
In mechanical ventilation, flow refers to the rate at which air is delivered to the patient’s lungs from the ventilator and is measured in liters per minute (L/min).
Flow can be set and adjusted based on the patient’s needs, ensuring adequate ventilation and patient comfort.
Proper flow settings are crucial to match the patient’s demand, prevent lung overdistension, and ensure synchronized interaction between the patient and the ventilator.
The flow pattern can be constant, decelerating, or accelerating, and is determined by the chosen mode of ventilation and the specific needs of the patient.
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.
Respiratory therapists and medical professionals who work with critically ill patients should develop a thorough understanding of how ventilators work.
This includes topics such as:
- 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.
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.
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