What is a Ventilator-Induced Lung Injury (VILI)?

Ventilator-induced lung injury (VILI) is a serious complication that can occur when a patient is placed on a mechanical ventilator to assist with breathing. VILI can cause damage to the lungs, making it harder for the patient to breathe and potentially leading to a prolonged hospital stay.

Despite advancements in mechanical ventilation techniques, VILI remains a significant problem in the intensive care unit and continues to be a topic of active research in the field of critical care medicine.

In this article, we will explore the causes and risk factors of VILI, the signs and symptoms to look out for, and the various treatment options that are available. We will also discuss the latest research and ongoing efforts to prevent and mitigate VILI. This article aims to provide a comprehensive overview of VILI to help healthcare professionals and caregivers better understand this condition and how to manage it effectively.

Causes

Ventilator-induced lung injury (VILI) is caused by the mechanical forces applied to the lungs during mechanical ventilation. This occurs when the lungs are inflated beyond their compliance (i.e., their ability to expand).

Ventilator-induced lung injuries are primarily caused by increased transpulmonary pressure during positive-pressure ventilation, which is the difference between alveolar and pleural pressure. Additionally, the use of high positive end-expiratory pressure (PEEP) levels can also result in lung injury.

Other factors that contribute to the development of VILI include the use of high oxygen concentrations, high airway pressure, long duration of mechanical ventilation, and the underlying lung disease of the patient.

Types

There are several different types of ventilator-induced lung injury (VILI) that can occur, depending on the specific mechanism of injury:

• Barotrauma: This occurs when the lungs are inflated beyond their compliance, causing damage to the alveoli and air spaces of the lungs. It can lead to a pneumothorax (i.e., collapsed lung) or pneumomediastinum (i.e., air in the space between the lungs and chest wall).
• Volutrauma: This occurs when the lungs are exposed to high tidal volumes (i.e., the amount of air delivered with each breath) and can lead to increased airway pressures and stretching of lung tissue.
• Atelectotrauma: This occurs when the alveoli are pulled apart from each other due to high airway pressures, or due to patients receiving high PEEP levels. This causes shear stress, which has damaging effects on the alveoli.
• Oxygen toxicity: This occurs when the lungs are exposed to high oxygen concentrations, which can cause damage to lung tissue.
• Shear stress: This occurs when the lungs are exposed to high pressure gradients, leading to injury in the lung’s blood vessels and microcirculation.

It’s important to note that multiple mechanisms can act together in the same patient. Additionally, some types of VILI can coexist with others, as well as with other lung diseases.

Risk Factors

The risk factors for ventilator-induced lung injury (VILI) include:

• Acute respiratory distress syndrome (ARDS): Patients with ARDS are at a higher risk of developing VILI because their lung tissue is already damaged and more susceptible to further injury.
• Prolonged mechanical ventilation: Patients who are on a mechanical ventilator for an extended period of time are at a higher risk of developing VILI.
• High airway pressure: High airway pressure can cause damage to the lungs and increase the risk of VILI.
• High oxygen concentrations: High levels of oxygen can cause inflammation and damage to the lungs, increasing the risk of VILI.
• High positive end-expiratory pressure (PEEP): High PEEP levels can cause injury to the lungs, especially in patients with ARDS.
• Underlying lung disease: Patients with chronic lung diseases such as COPD, emphysema, or cystic fibrosis are at a higher risk of developing VILI.
• Age: Elderly patients are at a higher risk of VILI because their lung tissue is more fragile and less compliant.
• Smoking history: Patients with a history of smoking are at an increased risk of VILI.

It’s important to note that many of these risk factors are related to mechanical ventilation itself. Therefore, to avoid a VILI, you should strive to avoid the initiation of mechanical ventilation or use as little support as possible with lower volume or pressure levels.

Signs and Symptoms

The signs and symptoms of ventilator-induced lung injury (VILI) can vary depending on the severity of the injury and the underlying cause. Some examples include:

• Rapid breathing: The patient’s breathing rate may increase as the body tries to compensate for the damaged lung tissue.
• Hypoxemia: VILI can cause a decrease in blood oxygen levels, resulting in shortness of breath, tachycardia, and cyanosis.
• Hypercapnia: VILI can cause an increase in carbon dioxide levels in the blood, resulting in dyspnea, drowsiness, and ventilatory failure.
• Increased work of breathing: The patient may show signs of dyspnea, including the use of accessory muscles, grunting, or nasal flaring.
• Cough: VILI can cause a productive or non-productive cough.
• Chest pain: VILI can cause chest pain, which can be diffuse or localized.
• Reduced lung compliance: VILI can cause the lungs to become less compliant and harder to inflate, leading to prolonged mechanical ventilation and other complications.

It’s important to note that some of these signs and symptoms can also occur with other lung injuries or conditions. Therefore, a thorough diagnostic evaluation is necessary to determine the specific cause of the patient’s symptoms.

Treatment

The treatment of ventilator-induced lung injury (VILI) involves the use of lung protective strategies. Some examples include:

• Low tidal volume ventilation: This approach aims to reduce the amount of air delivered to the lungs with each breath, which can help to decrease the risk of lung injury from volutrauma.
• Low airway pressure ventilation: This approach aims to reduce the amount of pressure applied to the lungs during ventilation, which can help to decrease the risk of lung injury from barotrauma.
• Low plateau pressures: Plateau pressure is the pressure in the lungs during the pause between breaths. This strategy aims to keep the plateau pressure at a lower level to avoid over-distending the lungs, which can cause damage to the alveoli.
• Low driving pressures: Driving pressure is the pressure that pushes air into the lungs during inspiration. It can be calculated as the difference between the plateau pressure and the PEEP level. Lowering the driving pressure may help to reduce the risk of barotrauma.
• Appropriate FiO2: Fraction of inspired oxygen (FiO2) is the percentage of oxygen in the air that a patient is breathing. In order to avoid injury from oxygen toxicity, It’s important to keep the FiO2 level as low as possible, but still high enough to maintain adequate oxygenation.
• Appropriate PEEP levels: This approach aims to use the lowest possible PEEP level that still allows for adequate oxygenation, which is helpful in decreasing the risk of lung injury in patients with ARDS.

Lung Protective Strategies

The following parameters should be used to minimize the risk of lung injury during mechanical ventilation:

• Tidal volume 4–8 mL/kg
• Plateau Pressure < 28 cmH2O
• Driving pressure < 15 cmH2O
• FiO2 to maintain PaO2 55–80 mmHg
• FiO2 to maintain SpO2 88–95%

Note: You should also strive to avoid patient-ventilator dyssynchrony, auto-PEEP, and air trapping.

In general, the most appropriate treatment option will depend on the specific cause and severity of the patient’s VILI, as well as on the underlying condition of the patient. Treatment plans should be individualized based on the patient’s clinical status, and close monitoring of their clinical condition is necessary.

Final Thoughts

Ventilator-Induced Lung Injury (VILI) is a serious complication of mechanical ventilation that can occur in critically ill patients. It is caused by the excessive pressure and volume delivered by the ventilator, leading to inflammation and injury of the lungs.

VILI can have serious consequences for patients, such as prolonged mechanical ventilation, increased risk of pneumonia, and even death. However, through proper monitoring and management, the incidence of VILI can be reduced.

By understanding the mechanisms and risk factors of VILI, healthcare professionals can take steps to minimize its occurrence, troubleshoot any problems, and improve patient outcomes. Thanks for reading, and, as always, breathe easy, my friend.