MV Learning Principles and Ventilation Techniques

Mechanical Ventilation

• Mechanical ventilation is a form of therapy used on patients unable to breathe on their own
• It is used to maintain proper oxygen and carbon dioxide levels in the body, a process called gas exchange
• A mechanical ventilator is a device that provides positive pressure ventilation to normalize a patient's arterial blood gas levels and maintain an adequate acid-base balance.

Introduction to Mechanical Ventilation

• Mechanical ventilation is a life support method for critically ill patients in ICUs, used short-term or long-term
• It is frequently used to treat patients with cardiopulmonary disorders, as well as postoperative patients recovering from anesthesia or sedation
• The ventilator provides a full breathing cycle during inspiration and expiration, relieving the patient of the work of breathing while recovering from the underlying condition

Mechanical Ventilator

• A mechanical ventilator is a machine that assists in the patient's ability to ventilate
• It helps the patient take in oxygen and remove carbon dioxide from the lungs
• While on the ventilator, a hollow tube called an endotracheal tube connects the patient to the machine
• The patient stays on the ventilator until able to achieve spontaneous breathing on their own.

Benefits of Mechanical Ventilation

• Decreases the patient's work of breathing, allowing respiratory muscles to rest and recover
• Provides adequate amounts of oxygen
• Provides stability, allowing medications to function while the patient heals
• Achieves adequate ventilation by removing carbon dioxide for effective gas exchange

Types of Ventilators

• Negative Pressure Ventilators (Iron Lung, Chest Cuirass): Apply negative pressure to the body to help with breathing. Advantages include not bypassing the body's natural defenses, and being durable and easy to operate. Disadvantages are a strict controller, isolation of the patient, and restrictions to nursing care.
• Positive Pressure Ventilators: Apply positive pressure to the airway opening to help with breathing. This type is the therapy of choice today due to its flexibility and less clumsy design.

High-Frequency Ventilation

• High-frequency ventilation uses above-normal ventilating rates with below-normal ventilating volumes.

Classification of Mechanical Ventilation

• Invasive: Positive pressure ventilation via endotracheal or tracheotomy tube.
• Non-Invasive: Positive pressure ventilation via a mask covering the mouth and/or nose.

First Rule in Mechanical Ventilation

• Look to the patient first, then to the machine

Natural vs. Mechanical Ventilation

• Natural breathing uses ambient air that varies in temperature and relative humidity (RH)
• Mechanical ventilation uses source air that is dry and cold, which is then warmed and humidified artificially at the lower trachea.

Possible Components of a Mechanical Ventilator

• Proximal flow sensor
• CO2 airway adaptor
• HME
• Flex tube
• ETT or tracheostomy tube
• Face mask

Ventilator Mode

• Ventilator mode: A way of describing how a mechanical ventilator assists a patient with inspiration.
• Primary control variables: The two primary control variables are volume control and pressure control, used in various ventilator modes.
• Volume Control: The ventilator sets a predetermined tidal volume.
• Pressure Control: The ventilator sets a predetermined pressure level during inspiration.
• The use of these modes depends on patients individual needs and physiological function

Ventilator Modes: Primary Modes

• Assist/Control (A/C): The ventilator delivers a preset number of mandatory breaths but allows the patient to trigger assisted breaths.
• Synchronous Intermittent Mandatory Ventilation (SIMV): The ventilator delivers a preset number of mandatory breaths, allowing the patient to initiate spontaneous breaths between them.

Ventilator Modes: Spontaneous Modes

• Continuous Positive Airway Pressure (CPAP): Maintains a constant pressure above atmospheric pressure throughout the breathing cycle.
• Pressure Support Ventilation (PSV): A pressure-control mode for the patient’s spontaneous breaths.
• Volume Support (VS): The ventilator delivers a supported breath to help the patient reach a predetermined tidal volume.

Ventilator Modes: Other Modes

• Control Mode Ventilation (CMV): The ventilator delivers a preset tidal volume at a set time-triggered frequency.
• Airway Pressure Release Ventilation (APRV): A mode using two levels of continuous positive airway pressure with an intermittent release phase for spontaneous breaths.
• Adaptive Support Ventilation (ASV): Adjusts the number of mandatory breaths and pressure support levels based on the patient's breathing pattern.
• Mandatory Minute Ventilation (MMV): Increases mandatory breaths when spontaneous breathing decreases to maintain a safe minimum minute ventilation.
• Proportional Assist Ventilation (PAV): Delivers variable pressure support based on the patient's work of breathing.
• Pressure Regulated Volume Control (PRVC): Ensures low peak airway pressure by manipulating flow and inspiratory time.
• Volume Assured Pressure Support (VAPS): Maintains stable tidal volume by incorporating both pressure support and volume-assisted cycles
• High-Frequency Oscillatory Ventilation (HFOV): Uses high frequencies of ventilation, typically for patients with severe respiratory conditions.

Ventilator Settings

• Mode: The approach used for controlling the ventilator's operation, selecting an appropriate mode depends on patient need for a full or partial support
• Tidal Volume: The volume of air delivered in each breath.
• Frequency/Respiratory Rate: The rate at which breaths are delivered per minute.
• FiO2 (Fraction of Inspired Oxygen): The concentration of oxygen in the delivered air.
• Flow Rate: The speed of oxygen delivery.
• I:E Ratio: The ratio of inspiratory to expiratory time.
• Sensitivity/Trigger Sensitivity: The intensity of effort required to trigger a breath from the ventilator.
• PEEP (Positive End Expiratory Pressure): The positive pressure maintained during the expiratory phase of breathing.
• Alarms: Indicators used to detect potential issues with the ventilation process.

Indications for Mechanical Ventilation

• Insufficient Oxygenation: Inadequate tissue and vital organ oxygenation resulting in hypoxemia
• Insufficient Ventilation: Inadequate removal of carbon dioxide resulting in a buildup leading to acidosis, seen in conditions like COPD, apnea, or neuromuscular disorders.
• Acute Lung Injury: (ALI), acute respiratory distress syndrome (ARDS) and other events- pneumonia, sepsis and trauma.
• Severe Hypotension: Severe low blood pressure, such as in shock, sepsis, or congestive heart failure (CHF)
• Inability to Protect the Airway: Unconsciousness or inability to protect the airway.

Contraindications for Mechanical Ventilation

• A patient who cannot survive without adequate ventilation or oxygenation.
• Patients who state that they do not want mechanical ventilation or being intubated, noted as DNI.

Complications of Mechanical Ventilation

• Barotrauma: Lung collapse caused by overinflation due to high pressure levels
• Volutrauma: Alveolar filling with fluid due to high tidal volumes (amount of air transported into lungs)
• Ventilator-Associated Pneumonia (VAP): Lung infection developing 48 hours or more after intubation.
• Auto-PEEP (Intrinsic PEEP): Lung over-inflation from prolonged inspiratory time or restrictive airways.
• Oxygen Toxicity: Excessive oxygen delivered for prolonged time can be harmful to the health.

Ventilator Settings: Initial Settings

• Initial Mode Selection: Choose based on patient need (full support via A/C or partial via SIMV)
• Tidal Volume (ml/kg of IBW): Set to 5-10 ml/kg of IBW.
• Frequency (Rate): Set to 10-20 breaths/minute.
• FiO2: Use 30-60%, unless the patient had a higher percentage before intubation, use that value instead. Try to lower the percentage as needed.
• Flow Rate (L/min): Set to 40-60 L/min.
• I:E Ratio: Set to 1:2 to 1:4.
• Sensitivity (cmH2O): Set to -1 to -2 cmH2O.
• PEEP (cmH2O): Set to 4-6 cmH2O.

Test your understanding of the first rule in MV learning and its application in medical decision-making. This quiz also covers important concepts related to Pressure Support Ventilation (PSV) and Automatic Tube Compensation (ATC), focusing on how these techniques impact patient care.