Mechanical ventilation

Understanding Mechanical Ventilation: A Lifeline in Critical Care

Imagine a world where breathing is no longer an automatic function, but a task requiring external assistance. This is the reality faced by many patients who require mechanical ventilation.

The Basics of Mechanical Ventilation

Mechanical ventilation is like having a personal assistant for your lungs. It’s medical-assisted artificial ventilation using a machine to provide air into and out of the lungs, ensuring that oxygen reaches every cell in the body while carbon dioxide is removed efficiently.

Types of Mechanical Ventilation

There are two main types: positive pressure ventilation (air pushed into lungs) and negative pressure ventilation (air pulled into lungs). Positive pressure ventilation was developed during World War II for fighter pilots, making it a fascinating blend of military technology and medical necessity.

A Historical Journey Through Mechanical Ventilation

The concept of mechanical ventilation has roots that stretch back to ancient Greece. Galen first described the idea, but it wasn’t until Robert Hooke and Vesalius experimented with it that we saw real advancements. Fast forward to 1908 when George Poe demonstrated a mechanical respirator by asphyxiating dogs and seemingly bringing them back to life—quite a dramatic demonstration!

Modern Mechanical Ventilation

Today, modern mechanical ventilation includes intermittent mandatory ventilation and synchronized intermittent mandatory ventilation. These modes are like the different gears in a car, each suited for specific driving conditions.

Risks and Complications

Mechanical ventilation isn’t without its challenges. Risks include volutrauma and barotrauma stemming from ventilator settings, pneumothorax, subcutaneous emphysema, pneumomediastinum, and pneumoperitoneum. Another significant complication is ventilator-associated lung injury, which can manifest as acute respiratory distress syndrome (ARDS).

Indications for Mechanical Ventilation

The patient’s underlying condition should be identified and treated while on the ventilator. Common medical indications include surgery, lung injury, pneumonia, asthma, paralysis, acid/base derangements, and neurological diseases.

Patient Monitoring and Care

Monitoring is crucial in ensuring that the patient receives optimal care. Pulse oximetry is commonly used when titrating FIO2 (fraction of inspired oxygen). A reliable target of SpO2 (oxygen saturation) is greater than 95%. The total PEEP (positive end-expiratory pressure) can be determined by doing an expiratory hold on the ventilator. If this is higher than the set PEEP, it indicates air trapping.

Advanced Monitoring Tools

Modern ventilators have advanced monitoring tools that help in assessing lung function and patient trends. Flow-volume and pressure-volume loops can show changes in compliance and resistance. Functional Residual Capacity (FRC) can be determined using the GE Carestation, providing valuable insights into lung mechanics.

The Role of Triggers and Cycles

Triggers are what cause a breath to be delivered by a mechanical ventilator. Breaths may be triggered by a patient taking their own breath, a ventilator operator pressing a manual breath button, or based on the set respiratory rate. The cycle is what causes the breath to transition from the inspiratory phase to the exhalation phase. Breaths in mechanical ventilation can be cycled based on time or flow, and are limited by set maximum pressure or volume.

Artificial Airways: A Lifeline for Patients

Artificial airways provide protection against airway collapse and aspiration. They include face masks, non-invasive ventilation, tracheal intubation, supraglottic airways, cricothyrotomy, and tracheostomy. A tracheostomy is a surgically created passage into the trachea, providing a well-tolerated option for patients with severe respiratory disease or those expected to have difficulty weaning from mechanical ventilation.

Tracheostomy tubes come in different types, including mouthpieces that do not provide aspiration protection but have lipseal designs for added stability. These tubes are essential in ensuring that the patient’s airway remains open and protected during prolonged periods of mechanical ventilation.

In conclusion, mechanical ventilation is a complex yet crucial aspect of critical care. It’s a lifeline for patients who cannot breathe on their own and requires careful management and monitoring to ensure the best possible outcomes. As technology continues to evolve, so too will our understanding and application of this vital medical intervention.