Mechanical ventilation assists or takes over breathing when a person’s respiratory system is failing. This support is necessary when the body cannot maintain adequate gas exchange, resulting in dangerously low oxygen or excessively high carbon dioxide levels in the blood. The goal is to stabilize the patient by decreasing the work of breathing, allowing the body to focus on healing the underlying illness or injury. When spontaneous breathing is insufficient, mechanical support becomes a life-sustaining necessity.
Defining Invasive Mechanical Ventilation
Invasive mechanical ventilation (IMV) requires an artificial airway to deliver breaths directly into the lungs. The term “invasive” refers to the physical penetration of the patient’s airway by a tube, creating a secure conduit for the medical gas. This artificial airway is typically an endotracheal tube (ETT) inserted through the mouth or nose, past the vocal cords, and into the trachea.
IMV is distinct from non-invasive ventilation (NIV), which uses a tight-fitting mask over the nose and mouth for support, such as CPAP or BiPAP. Because IMV bypasses the upper airway, it allows for precise control over the volume and pressure of air delivered, making it suitable for severe respiratory failure. The tube placement also protects the airway from aspiration, a risk for patients with a decreased level of consciousness.
Clinical Scenarios Requiring Invasive Ventilation
The decision to initiate IMV is based on a patient’s inability to maintain gas exchange or protect their airway. Acute respiratory failure is a common indication, often caused by conditions like severe pneumonia, acute respiratory distress syndrome (ARDS), or acute exacerbations of chronic lung diseases. In these cases, the lungs are too stiff or inflamed to effectively transfer oxygen and remove carbon dioxide.
Airway protection is another primary reason, especially for patients with decreased consciousness due to stroke, severe head trauma, or drug overdose. These patients cannot reliably cough or swallow, risking the inhalation of stomach contents into their lungs. The endotracheal tube seals the airway, preventing this complication. IMV is also required during complex surgical procedures necessitating general anesthesia, or when controlled hyperventilation is needed to manage conditions like severe brain swelling.
The Procedure and Mechanism of Action
The process begins with intubation, the placement of the endotracheal tube. This procedure is typically performed in a monitored setting, such as an emergency room or intensive care unit, requiring the patient to be sedated for comfort. For patients needing long-term ventilation (usually beyond 10 to 14 days), a tracheostomy may be performed, where the tube is surgically placed directly into the trachea.
Once the artificial airway is secure, it connects to the mechanical ventilator, a machine that delivers positive pressure ventilation. This mechanism actively pushes oxygen-enriched air into the lungs to inflate them. The machine assists breathing by overcoming the natural resistance of the patient’s lungs and chest wall.
The ventilator is programmed to control parameters, including the respiratory rate and the volume of air delivered with each breath (tidal volume). Clinicians select a specific mode, such as volume-control (fixed air volume) or pressure-control (fixed pressure), to tailor support to the patient’s lung condition. Positive End-Expiratory Pressure (PEEP) is also applied, which maintains pressure in the lungs at the end of exhalation. This prevents the alveoli from collapsing, maximizing the surface area for oxygen transfer.
Potential Complications and Patient Monitoring
While IMV is a life-saving measure, its use carries risks requiring continuous attention. A significant complication is Ventilator-Associated Pneumonia (VAP), an infection occurring when bacteria migrate down the breathing tube. Positive pressure delivery can also cause physical lung injury, such as barotrauma (damage from excessive pressure) or volutrauma (damage from excessive volume).
To mitigate these risks, patients undergo continuous monitoring. Vital signs, including heart rate, blood pressure, and oxygen saturation, are constantly tracked. The ventilator has alarms to alert staff to issues like high airway pressure or low delivered volume. The deep sedation required for intubation can also lead to complications like delirium or muscle weakness from prolonged immobility. The healthcare team routinely assesses the patient’s readiness to breathe on their own and discontinue support.