Mechanical Ventilation Quiz

Mechanical Ventilation Systems

• Mechanical ventilators (respirators) are used to assist patients who cannot naturally breathe.
• They are used for acute and chronic respiratory problems and in intensive care, home care, and emergency medicine.
• Mechanical ventilators aim for natural respiration, mimicking the negative pressure generated by the diaphragm in the pleural cavity
• Negative pressure ventilators were initially designed to replicate this natural inspiration process.
• Mechanical ventilators have disadvantages including difficulty creating a seal around the chest wall, limited patient accessibility for care and monitoring, difficulty synchronizing with patient effort, and the bulky nature of the machinery.

Physiology of Respiration

• The respiratory system is a biological system of organs and structures responsible for gas exchange (respiration) in an organism.
• The respiratory system's primary function is to take in oxygen from the atmosphere and remove carbon dioxide from the blood.
• Respiratory failure is a critical condition in which the respiratory system cannot efficiently supply oxygen to the blood or remove carbon dioxide.

Introduction to Mechanical Ventilation

• Mechanical ventilators are used to artificially ventilate the lungs of patients when natural breathing is insufficient.
• Mechanical ventilators are available for short-term treatment of acute respiratory problems and long-term therapy for chronic conditions.
• The main task of these devices is to ventilate the lungs as closely as possible to natural respiration.

Negative Pressure Ventilators

• Negative pressure ventilation involves generating a negative pressure around the patient's chest cavity to expand the lungs and facilitate breathing.
• This method creates a pressure gradient to make air flow into the lungs.
• The expanding and contracting chest wall is aided by moving the thoracic walls outward.
• However, negative pressure ventilators have several disadvantages. These include the challenge of creating a proper seal around the chest, making patient access for monitoring and care more difficult and maintaining synchronization between the machine and patient effort along with the machines being bulky and noisy.

Positive Pressure Ventilators

• Positive pressure ventilators force air into the lungs.
• This is usually done by applying greater pressure than atmospheric pressure to the airways.
• They generate the inspiratory pressure for the respiratory process.

Component Overview

• Breathing circuit: A closed loop system that connects the ventilator to the patient.
• Control system: The component that regulates the breathing process and the devices. An Air Compressor
• Gas supply: Ventilators receive compressed air and oxygen via gas tanks and/or a dedicated compressor.
• Monitors and alarms: Provide continuous monitoring to alert the medical staff to any faults.
• Heating and humidification: These components maintain a comfortable temperature and humidity in the breathing circuit.
• Nebulizer Devices: Some respiratory therapy machines use nebulisers to make inhalable liquid medications into a mist.
• Filters: Equipment is protected from contamination by the filters within the device.
• Power supply: The ventilator requires power to operate various crucial parts like the compressor and other components.

Ventilation Modes

• Ventilation modes are crucial parameters of ventilation. Two main categories are: mandatory and spontaneous
• Mandatory mode: The ventilator takes control of the breathing cycle entirely. This can be further subdivided into volume-controlled and pressure-controlled modes.
• Volume-controlled mode: The ventilator delivers a pre-set amount of air to each respiration.
• Pressure-controlled mode: The ventilator delivers a pre-set pressure of air to each breathing cycle.
• Spontaneous mode: The ventilator only supports patient breaths, assisting with the respiratory mechanics to ensure sufficient ventilation and oxygenation levels.

Adaptive Pressure Control

• In this mode, the ventilator consistently tracks delivered tidal volume and airway pressure.
• It adjusts the pressure for each breath to achieve the desired tidal volume.
• It compares the produced tidal volume with the desired one, and adjusts the pressure as necessary.

Continuous Positive Airway Pressure (CPAP)

• It maintains a positive airway pressure during breathing.
• This mode is usually used in spontaneous ventilation to support patient breaths and maintain adequate breathing, with the sensitivity level set lower than PEEP.

Pressure Support

• It is similar to CPAP but with a pressure support level greater than PEEP.
• It aids patients in taking breaths on their own. Maintaining consistent pressure via this mode, while the patient exhales, the ventilator automatically shuts off the air flow and opens the valves to enable exhalation into the atmosphere.

Ventilation Specifications

• Key specifications of ventilators often include tidal volume, flow rate, inspiratory or expiratory pressures, breathing rate, inspiratory or expiratory time, and I:E ratio.
• Parameters like the inspiratory time, expiratory time, I:E ratio, gas mixture, and breath rhythm are crucial.
• Controlled mandatory ventilation, pressure-support, and other similar parameters (flow, volume, or rate) are important as well.

Breath Delivery Control

• The ventilator employs valves and compressed air, mixed in accordance with the therapist's specifications, to deliver the necessary air with the right levels of oxygen.
• The microprocessor controls these components, relying on feedback loops from pressure and flow sensors to ensure appropriate tidal volume and to adjust PEEP levels.

Monitoring and Data Display

• Vital parameters like pressure, flow, volume, temperature, and FiO2 (fraction of inspired oxygen) are frequently displayed, often with alarm systems to alert medical personnel to potential problems.
• Data on equipment performance is frequently needed, as is the case for output, ports, and analog outputs, and report generation.

Intensive Care Ventilators, Portable Ventilators, and Transport Ventilators

• Different ventilator models are designed for various use cases, like Intensive Care, Pediatrics, Portable and Transport, each with particular features and capabilities.