Terminology in Ventilator Settings

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Introduction:-

When working with ventilators, healthcare providers use specific terminology to describe the settings and functions of the device.
These Terminology in Ventilator Settings is crucial for the effective management of patients requiring mechanical ventilation. This guide covers the essential ventilator terminology.

Ventilator Settings

  1. Respiratory Rate (RR) or Frequency :-

    • Definition :- The number of breaths the ventilator delivers per minute.
    • Units :- Breaths per minute (bpm)
    • Typical Range :- 12-20 bpm

  2. Fraction of Inspired Oxygen (FiO2) :-

    • Definition :- The percentage of oxygen in the air mixture delivered to the patient.
    • Units :- Percentage (%)
    • Typical Range :- 21% (room air) to 100%

  3. Positive End-Expiratory Pressure (PEEP) :-

    • Definition :- The pressure in the lungs (alveolar pressure) at the end of exhalation.
    • Units :- Centimeters of water (cmH2O)
    • Typical Range :- 5-20 cmH2O

  4. What is Auto-PEEP? :-

    Auto-PEEP stands for “Auto Positive End-Expiratory Pressure.” It occurs when pressure builds up in the lungs at the end of exhalation because the patient doesn’t fully exhale all the air before the next breath starts. This can happen in patients on mechanical ventilation.

    Causes of Auto-PEEP :-

    1. Inadequate Expiratory Time: If the ventilator settings do not allow enough time for exhalation, air can get trapped in the lungs.
    2. Airway Obstruction: Conditions like asthma or chronic obstructive pulmonary disease (COPD) can cause narrowing of the airways, making it hard to exhale completely.
    3. High Respiratory Rate: Breathing too quickly can prevent full exhalation before the next breath starts.

    How to Identify Auto-PEEP :-

    1. Observe the Patient: Look for signs of difficulty in breathing, such as increased effort to breathe out, use of accessory muscles, or discomfort.
    2. Ventilator Waveforms: Check the ventilator screen for abnormal waveforms. Auto-PEEP can cause changes in pressure-time and flow-time curves. For example, the flow curve may not return to baseline before the next breath starts.
    3. Measure PEEP: Use the ventilator to measure the total PEEP (Auto PEEP=Total PEEP-Set PEEP). Compare this to the set PEEP to see if there’s a difference.
    4. End-Expiratory Pause: Perform an end-expiratory pause maneuver on the ventilator. This holds the breath at the end of exhalation, allowing trapped air to equalize with the ventilator circuit. The pressure measured during this pause is the total PEEP, including auto-PEEP.

    How to Manage Auto-PEEP :-

    1. Increase Expiratory Time: Adjust the ventilator settings to allow more time for exhalation. This can be done by reducing the respiratory rate or increasing the expiratory phase.
    2. Reduce Tidal Volume: Lowering the amount of air delivered with each breath can help prevent air trapping.
    3. Bronchodilators: Medications that open up the airways can help improve exhalation in patients with obstructive airway diseases.
    4. Check for Obstructions: Ensure that the ventilator tubing and airways are clear of mucus or other obstructions.

  5. Tidal Volume (Vt) :-

    • Definition :- The amount of air delivered to the lungs with each breath.
    • Units :- Milliliters (mL)
    • Typical Range :- 8-10 mL/kg of ideal body weight
Exhaled Tidal Volume :-
Exhaled tidal volume is the amount of air a person breathes out during a normal, relaxed breath. 
    1. Accuracy in Measurement: Exhaled tidal volume is the most accurate measure of the amount of air the patient actually receives from each breath. This ensures that the patient is getting the right amount of air needed for proper breathing.
    2. Ventilator Settings Adjustment: It guides healthcare providers in setting the correct ventilator settings for patients.
    3. Detecting Respiratory Issues: Changes can indicate lung problems like infections or fluid buildup.

What to Do if Exhaled Tidal Volume Deviates :-

If the exhaled tidal volume (ETV) is different from the set tidal volume (TV) by 10% or more, it means there might be a problem. Here’s how to troubleshoot in simple steps:
  1. Check for Leaks: Look for any leaks in the ventilator tubing or around the mask. Even a small hole can cause air to escape.
  2. Inspect Connections: Make sure all the connections are tight and secure. Loose connections can lead to air loss.
  3. Examine the Patient: Sometimes, changes in the patient’s condition can affect ETV. Check if the patient is comfortable and breathing properly.
  4. Evaluate Ventilator Settings: Double-check the ventilator settings to ensure they are correctly set according to the patient’s needs.
  5. Assess the Ventilator: If everything else seems fine, there might be an issue with the ventilator itself. Call for technical support to inspect the machine.

  1. Inspiratory to Expiratory Ratio (I:E Ratio) :-

    • Definition :- The ratio of the duration of inhalation to exhalation.
    • Typical Ratio :- 1:2 (inspiration time is half of expiration time)

  3. Inverse Inspiratory to Expiratory Ratio :

    The inverse inspiratory to expiratory ratio is when the time spent breathing in (inhaling) is longer than the time spent breathing out (exhaling). For example, if the ratio is 2:1,3:1  it means inhalation lasts twice as long as exhalation.

    Significance :-

    1. Improves Oxygenation: More time inhaling allows more oxygen to enter the lungs and, consequently, the bloodstream.
    2. Keeps Alveoli Open: The longer inhalation time helps keep the tiny air sacs in the lungs (alveoli) open, preventing collapse and improving overall lung function.
    This technique is often used in ventilator settings for patients with severe lung conditions to ensure they receive adequate oxygen and maintain healthy lung function.
  4. Inspiratory Pressure :-
    • Definition :- The pressure applied to the lungs during inhalation.
    • Units :- Centimeters of water (cmH2O)
    • Typical Range :- 15-25 cmH2O

  5. Peak Inspiratory Pressure (PIP) :-

    • Definition :- The maximum pressure reached during inhalation.
    • Units :- Centimeters of water (cmH2O)
    • Typical Range :- Less than 35 cmH2O

  6. Plateau Pressure (Pplat) :-

    • Definition :- The pressure measured during a pause at the end of inhalation.
    • Units :- Centimeters of water (cmH2O)
    • Typical Range :- Less than 30 cmH2O

Ventilator Modes

  1. Volume-Controlled Ventilation (VCV) :-

    • Delivers a set volume of air with each breath.

  2. Pressure-Controlled Ventilation (PCV) :-

    • Delivers air at a predetermined pressure.

  3. Assist-Control Ventilation (ACV) :-

    • Allows the patient to initiate breaths, but ensures each breath reaches a preset volume or pressure.

  4. Synchronized Intermittent Mandatory Ventilation (SIMV) :-

    • Provides a set number of mandatory breaths while allowing spontaneous breathing in between.

  5. Continuous Positive Airway Pressure (CPAP) :-

    • Provides a constant level of pressure to keep airways open.

  6. Bilevel Positive Airway Pressure (BiPAP) :-

    • Provides two levels of pressure: higher during inhalation and lower during exhalation.

Monitoring Parameters

  1. Minute Ventilation (Ve) :-

    • Definition :- The total volume of air entering or leaving the lungs per minute.
    • Units :- Liters per minute (L/min)
    • Formula :- Ve = Vt x RR

  2. Alveolar Ventilation :-

    • Definition :- The volume of air that reaches the alveoli per minute.
    • Units :- Liters per minute (L/min)

  3. Oxygen Saturation (SpO2) :-

    • Definition :- The percentage of hemoglobin saturated with oxygen.
    • Units :- Percentage (%)
    • Typical Range :- 95-100%

  4. End-Tidal CO2 (EtCO2) :-

    • Definition :- The partial pressure of carbon dioxide at the end of exhalation.
    • Units :- Millimeters of mercury (mmHg)
    • Typical Range :- 35-45 mmHg

Additional Terms

  1. Compliance :-

    • Definition :- The ability of the lungs to expand in response to pressure.
    • Units :- Milliliters per centimeter of water (mL/cmH2O)

  2. Triggers Terminology in Ventilator Settings

    • Definition: A trigger in a ventilator is a signal that tells the machine to help the patient breathe. It can be started by the patient trying to breathe or by a timer on the machine.
    • Proper triggering enhances patient comfort, optimizes ventilation efficiency, and prevents ventilator-induced lung injury.

  3. Resistance :-

    • Definition :- The opposition to airflow within the respiratory tract.
    • Units :- Centimeters of water per liter per second (cmH2O/L/s)

  4. Dead Space :-

    • Definition :- The volume of air that does not participate in gas exchange.
    • Units :- Milliliters (mL)

  5. Sigh:- 

  • Definition:- A sigh on a ventilator is a larger-than-normal tidal volume breath(1.5-2 time) delivered at a set interval
  • Sighs in mechanical ventilation provide hyperinflation, prevent atelectasis, improve oxygenation, reduce lung injury, mimic natural breathing, and enhance respiratory function, supporting critically ill patients and promoting better recovery and comfort.

  1. Ventilator-Induced Lung Injury (VILI) :-

    • Definition :- Lung damage caused by mechanical ventilation.
    • Includes barotrauma, volutrauma, and atelectrauma.

Conclusion:-

Understanding ventilator terminology is essential for healthcare providers managing patients on mechanical ventilation. This knowledge ensures accurate settings, effective monitoring, and timely interventions, ultimately improving patient outcomes.

Also Read ⇒ Ventilator-Associated Risks

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