Mechanical Ventilation in Respiratory Care
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How does Assist Control (AC) ventilation differ from Synchronized Intermittent Mandatory Ventilation (SIMV)?

  • AC allows spontaneous breaths between mandatory breaths
  • SIMV synchronizes mandatory breaths with the patient’s effort, allowing spontaneous breaths without supporting them (correct)
  • AC delivers mandatory breaths at a set rate with spontaneous breaths supported by the ventilator
  • SIMV provides a preset tidal volume for every breath initiated by the patient

    • Which of the following is an example of a contraindication for mechanical ventilation?

  • Exacerbation of chronic obstructive pulmonary disease (COPD)
  • Severe head trauma
  • Acute respiratory failure
  • Unstable hemodynamics (correct)

    • What is a typical clinical application of monitoring the ETCO2/PaCO2 gradient?

  • Measuring functional residual capacity
  • Diagnosing ventilator-associated pneumonia
  • Determining lung compliance
  • Assessing alveolar dead space (correct)

    • In Pressure Control Ventilation, which of the following parameters is preset?

    <p>Peak inspiratory pressure</p> Signup and view all the answers

    What is the main difference between mainstream and side-stream CO2 monitoring in capnography?

    <p>Mainstream measures CO2 directly at the airway</p> Signup and view all the answers

    What is the primary purpose of increasing functional residual capacity (FRC) in CPAP therapy?

    <p>To recruit previously unventilated or underventilated alveoli and improve oxygenation</p> Signup and view all the answers

    Which patient interface is not typically used for CPAP in neonates?

    <p>Mouthpiece</p> Signup and view all the answers

    What does the EPAP component of BiPAP mainly function to improve?

    <p>Functional residual capacity and oxygenation</p> Signup and view all the answers

    What must be ensured before the initiation of CPAP therapy?

    <p>The patient is capable of sustaining eucapnic ventilation documented by appropriate $P_{a}CO_{2}$ and pH from an arterial blood gas</p> Signup and view all the answers

    What parameter must always be set higher in BiPAP therapy?

    <p>IPAP</p> Signup and view all the answers

    What is the term used to describe the pressure difference between IPAP and EPAP in BiPAP?

    <p>Drive pressure or pressure support</p> Signup and view all the answers

    In CPAP, what can a leak in the patient interface potentially result in?

    <p>Pressure loss, fall in FRC, and decreased $SpO_{2}$</p> Signup and view all the answers

    What does a higher drive pressure in BiPAP indicate regarding patient assistance?

    <p>More assistance is required to maintain adequate ventilation</p> Signup and view all the answers

    Which parameter is controlled by the ventilator in Spontaneous mode of BiPAP?

    <p>IPAP and EPAP</p> Signup and view all the answers

    In Spontaneous-timed mode, what instigates the ventilator to initiate independent breaths?

    <p>Respiratory rate falling below the set threshold</p> Signup and view all the answers

    What triggers the breaths in the Pressure Support mode?

    <p>Both pressure and flow trigger</p> Signup and view all the answers

    What differentiates Spontaneous-timed mode from Spontaneous mode in BiPAP?

    <p>Backup rate setting and independent breath initiation</p> Signup and view all the answers

    What action should be taken if apnea is detected in a patient using the Spontaneous-timed mode?

    <p>Convert the patient to invasive ventilation</p> Signup and view all the answers

    What determines the end of the inspiratory phase in Pressure Support ventilation?

    <p>The patient's inspiratory flow dropping to a preset value</p> Signup and view all the answers

    How does the augmentation of a patient's spontaneous breath with pressure affect alveolar ventilation?

    <p>It improves alveolar ventilation proportionally to the pressure support setting used</p> Signup and view all the answers

    During inspiration in Pressure Support ventilation, what happens once the pressure target is reached?

    <p>Flow begins to decay</p> Signup and view all the answers

    What triggers a breath in Pressure Support Ventilation?

    <p>The patient's inspiratory effort meeting a pressure or flow threshold</p> Signup and view all the answers

    Why is Pressure Support ventilation considered spontaneous?

    <p>The patient triggers the breath and the tidal volume varies with the patient's effort</p> Signup and view all the answers

    What happens to the ventilatory flow once inspiration starts in Pressure Support ventilation?

    <p>It increases to build pressure until reaching the pressure target, then begins to decay</p> Signup and view all the answers

    What is indicated by the pressure graph plateauing before dropping back down?

    <p>The pressure is being held constant temporarily.</p> Signup and view all the answers

    When does the flow graph show the highest flow rate?

    <p>During the drop in pressure.</p> Signup and view all the answers

    Why does the flow graph show no flow during inspiration?

    <p>Pressure is being held constant during this time.</p> Signup and view all the answers

    What likely causes the repeating pattern seen in both the pressure and flow graphs?

    <p>Cyclic mechanical ventilation.</p> Signup and view all the answers

    What is the relationship between pressure and flow during the observed decrease in pressure?

    <p>Flow begins and increases.</p> Signup and view all the answers

    What does the label 'Flow starvation' on the pressure graph indicate?

    <p>A spike in pressure due to insufficient flow.</p> Signup and view all the answers

    During which periods does the flow graph show a rapid drop in flow?

    <p>Simultaneously with spikes in pressure.</p> Signup and view all the answers

    What is represented by the dotted line in the pressure graph?

    <p>The baseline pressure.</p> Signup and view all the answers

    How does the flow graph behave when the pressure returns to the baseline after a spike?

    <p>The flow returns to its constant high state.</p> Signup and view all the answers

    How is time represented on the flow and pressure graphs?

    <p>Horizontally with uniform scales.</p> Signup and view all the answers

    Which mode of ventilation is specifically targeted for ARF with dyssynchrony?

    <p>PRVC / VW +</p> Signup and view all the answers

    For which mode is 'Volume Control' specifically indicated?

    <p>ARF</p> Signup and view all the answers

    What is the target parameter for the SIMV - Press Cont mode?

    <p>Pressure / Spont</p> Signup and view all the answers

    Which support mode is primarily used during the weaning phase?

    <p>Pressure Support</p> Signup and view all the answers

    Which ventilation mode is least likely to be used according to the indications provided?

    <p>SIMV - Press Cont</p> Signup and view all the answers

    Which combination of pH and blood gas value indicates respiratory acidosis?

    <p>Low pH and High PCO2</p> Signup and view all the answers

    What condition is indicated by a high pH and high HCO3?

    <p>Metabolic Alkalosis</p> Signup and view all the answers

    Which acid-base disorder is likely if the pH is normal, but there is an abnormal PCO2 or HCO3?

    <p>Mixed Acid-Base Disorder</p> Signup and view all the answers

    What is the primary sign of metabolic acidosis on an ABG analysis?

    <p>Low pH and Low HCO3</p> Signup and view all the answers

    If a patient has low PCO2 and high pH, which of the following is the correct diagnosis?

    <p>Respiratory Alkalosis</p> Signup and view all the answers

    A patient presents with the following ABG results: pH: 7.52, CO2: 30, HCO3-: 24. What is the correct interpretation?

    <p>Respiratory alkalosis</p> Signup and view all the answers

    Which combination of ABG values indicates a compensated metabolic alkalosis?

    <p>pH: 7.36, CO2: 55, HCO3-: 35</p> Signup and view all the answers

    A patient's ABG results are pH: 7.28, CO2: 55, HCO3-: 24. What is the most likely diagnosis?

    <p>Respiratory acidosis</p> Signup and view all the answers

    Which ABG values would you expect to find in a patient with acute metabolic acidosis?

    <p>pH: 7.33, CO2: 40, HCO3-: 20</p> Signup and view all the answers

    What is the correct interpretation of the following ABG results: pH: 7.60, CO2: 25, HCO3-: 35?

    <p>Partially compensated metabolic alkalosis</p> Signup and view all the answers

    Study Notes

    Mechanical Ventilation

    • Indications for mechanical ventilation: respiratory failure, apnea, airway protection, and cardiac arrest
      • Example: patient with severe pneumonia and respiratory failure
    • Contraindications for mechanical ventilation: patient with a Do Not Resuscitate (DNR) order, those with a poor prognosis, and those who are medically unsuitable
      • Example: terminally ill patient with a DNR order
    • Goals of mechanical ventilation: oxygenation, ventilation, and respiratory muscle rest
    • Normal physiologic ventilation: diaphragmatic contraction and negative pressure generation
    • Negative pressure ventilation: uses negative pressure to expand the chest cavity, such as with an iron lung
    • Positive pressure ventilation: uses positive pressure to expand the lungs, such as with a mechanical ventilator
    • Inspiratory phase variables: tidal volume, inspiratory pressure, and flow rate
    • Expiratory phase variables: expiratory pressure, flow rate, and time

    Modes of Mechanical Ventilation

    • Assist Control/Continuous Mandatory Ventilation (AC/CMV): delivers a set tidal volume at a fixed rate, with additional breaths supported as needed
    • Synchronized Intermittent Mandatory Ventilation (SIMV): delivers a set tidal volume at a fixed rate, with additional breaths allowed but not supported
    • Pressure Control Ventilation (PCV): delivers a set pressure at a fixed rate, with the tidal volume variable
    • Pressure Support Ventilation (PSV): provides a set pressure support during spontaneous breathing
    • Continuous Positive Airway Pressure (CPAP): provides a constant pressure during both inspiration and expiration
    • Airway Pressure Release Ventilation (APRV): provides a high pressure during inspiration and a low pressure during expiration

    Hazards and Complications of Mechanical Ventilation

    • Pulmonary barotrauma and volutrauma
    • Oxygen toxicity
    • Ventilator-associated pneumonia (VAP)
    • Respiratory alkalosis
    • Cardiac depression

    Effects of Mechanical Ventilation on Lung Mechanics

    • Increased lung volume and compliance
    • Decreased functional residual capacity (FRC)
    • Altered ventilation-perfusion relationships
    • Redistribution of blood flow

    Initial Ventilator Settings and Modifications

    • Initial settings: based on patient data, such as height, weight, and lung disease
    • Modifications: based on patient response, such as arterial blood gases, oxygen saturation, and ventilator waveforms

    Capnography

    • Phases of a normal capnogram: I (inspiratory), II (expiratory), and III (alveolar)
    • ETCO2/PaCO2ETCO_2/PaCO_2ETCO2​/PaCO2​ gradient: normally 2-5 mmHg, indicating alveolar ventilation and perfusion
    • Abnormal capnograms: indicating respiratory or cardiac disease, rebreathing, or exhausted CO2 absorbers
    • Clinical interventions: based on capnogram morphology and gradient, such as adjusting ventilation or perfusion
    • Normal ventilation-perfusion relationships: dependent on regional lung volume and perfusion
    • Abnormal ventilation-perfusion relationships: indicating respiratory disease, such as COPD or ARDS
    • Mainstream vs. side-stream CO2CO_2CO2​ technology: mainstream more accurate, but side-stream more convenient and easier to use

    Continuous Positive Airway Pressure (CPAP)

    • CPAP applies positive baseline pressure above ambient pressure during continuous spontaneous ventilation
    • Increases functional residual capacity (FRC) by recruiting previously unventilated or underventilated alveoli, improving oxygenation
    • Patient must be capable of sustaining eucapnic ventilation before CPAP initiation, confirmed by an appropriate PaCO2P_{a}CO_{2}Pa​CO2​ and pH from an arterial blood gas
    • Patient interface includes a mask, artificial airway, or nasal prongs in neonates, and must seal to allow pressure to build above ambient pressure
    • Leaks in the interface can result in pressure loss, decreased FRC, oxygen saturation (SpO2SpO_{2}SpO2​), and partial pressure of oxygen (PaO2P_{a}O_{2}Pa​O2​)

    Bilevel Positive Airway Pressure (BiPAP)

    • BiPAP applies positive airway pressure during inspiration and exhalation (baseline pressure) during spontaneous ventilation
    • Inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP) are set independently
    • IPAP must always be set higher than EPAP
    • IPAP improves ventilation (PaCO2P_{a}CO_{2}Pa​CO2​) and oxygenation in conditions due to hypoventilation
    • EPAP functions like CPAP, recruiting underventilated alveoli during exhalation, increasing FRC and oxygenation
    • Drive pressure (IPAP-EPAP) measures the pressure assistance required to maintain adequate ventilation (PaCO2P_{a}CO_{2}Pa​CO2​ and pH), and increasing it improves ventilation (PaCO2P_{a}CO_{2}Pa​CO2​)

    Pressure Support

    • Breath is triggered by meeting either a pressure or flow threshold, making it a spontaneous ventilation type
    • Tidal volume delivered varies based on patient's effort
    • Inspiratory time lasts only as long as the patient is actively inhaling
    • Breath cycle ends when patient's inspiratory flow reaches a preset value

    Augmentation

    • Augmenting spontaneous breath with pressure improves alveolar ventilation
    • Improved alveolar ventilation reduces hypercapnia and improves oxygenation
    • Degree of improved alveolar ventilation is proportional to pressure support setting used

    Inspiration

    • Ventilator targets a set pressure during inspiration
    • Flow increases to build pressure in the circuit during inspiratory phase
    • Flow decays once pressure target is reached
    • Cycle ends when inspiratory flow drops to a preset threshold (usually a percentage of peak flow)

    Pressure

    • Graph illustrates pressure changes over time, exhibiting a repeating pattern
    • Pressure increases, plateaus, and then drops back down, with each subsequent increase reaching a slightly higher pressure
    • Pressure rise is highlighted on the graph with an arrow pointing upwards from the highest pressure point

    Flow

    • Graph depicts flow changes over time, displaying a repeating pattern
    • Flow is zero when pressure is being maintained
    • When pressure drops, flow begins and increases before decreasing again as pressure returns to baseline
    • Flow is absent during inspiration, as indicated on the graph
    • The relationships between pressure and flow likely represent the breathing process

    Pressure and Flow Graph

    • The graph displays pressure and flow over time, with pressure shown on the top graph and flow on the bottom graph.

    Pressure

    • A dotted line represents the baseline pressure on the top graph.
    • Pressure spikes above the baseline at certain times before returning to the baseline.
    • One such spike is labeled as "Flow starvation", indicating a specific instance of pressure increase.

    Flow

    • The bottom graph shows that the flow is typically high and constant.
    • There are two distinct periods where the flow drops rapidly before returning to its initial state.
    • Time is measured in seconds and displayed on the horizontal axis.

    Modes of Ventilation

    Control / Assist Control Mode

    • Targets volume and uses volume control, indicated for Acute Respiratory Failure (ARF)
    • Targets pressure and uses pressure control, indicated for Acute Respiratory Distress Syndrome (ARDS)
    • Targets volume with pressure-regulated flow and uses PRVC / VW+, indicated for ARF with dyssynchrony

    SIMV Mode

    • Targets volume and spontaneity, uses SIMV-Vol Cont, indicated for ARF
    • Targets pressure and spontaneity, uses SIMV-Press Cont, indicated for infrequent use
    • Targets volume or pressure with support, uses VC or PC with PS, indicated for ARF

    Support Mode

    • Targets volume and uses volume support, indicated for weaning
    • Targets pressure and uses pressure support, indicated for weaning

    ABG Analysis

    pH Levels and Associated Conditions

    • Low pH: Indicates Acidemia
    • High pH: Indicates Alkalemia
    • Normal pH: No Abnormality or Mixed Acid-Base Disorder

    Identifying Acidemia

    • High PCO2: Respiratory Acidosis
    • Low HCO3: Metabolic Acidosis

    Identifying Alkalemia

    • Low PCO2: Respiratory Alkalosis
    • High HCO3: Metabolic Alkalosis

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    Description

    This quiz covers the indications, contraindications, and goals of mechanical ventilation, including respiratory failure, apnea, airway protection, and cardiac arrest. Test your knowledge on when and why mechanical ventilation is used in medical care.

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