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Questions and Answers

What has been termed atelectrauma in the context of lung injury?

  • Increased pulmonary capillary pressure causing edema
  • Infection-induced lung injury from pneumonia
  • Recruitment-derecruitment leading to shear stress and surfactant loss (correct)
  • Ventilator asynchrony due to patient discomfort

    • Which condition is NOT listed as a predisposition to barotrauma?

  • Obstructive sleep apnea during ventilation (correct)
  • Aspiration of gastric acid
  • Bullous lung disease associated with emphysema
  • High levels of PEEP with high tidal volumes

    • What distinguishes ventilator-associated lung injury (VALI) from ventilator-induced lung injury (VILI)?

  • VALI occurs due to mechanical ventilation in humans (correct)
  • VILI is not recognized as a component of mechanical ventilation
  • VALI is related to direct lung tissue damage only
  • VILI is exclusively caused by aspiration events

    • What happens during barotrauma when positive pressure ventilation is used?

    <p>Alveolar rupture occurs, leading to interstitial air accumulation</p> Signup and view all the answers

    Which of the following conditions is characterized by excess pressure and is linked to ventilator use?

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

    What is a common form of VALI that can occur during mechanical ventilation?

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

    What type of lung injury is caused by both shear stress and loss of surfactant?

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

    What is a consequence of patient-ventilator asynchrony?

    <p>Increased risk of ventilator-associated pneumonia</p> Signup and view all the answers

    What is the primary cause of ventilator-induced lung injury (VILI)?

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

    What condition may follow pneumomediastinum?

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

    What is indicated by the presence of crepitant skin in a patient on mechanical ventilation?

    <p>Subcutaneous emphysema</p> Signup and view all the answers

    What anatomical area is affected by VILI?

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

    What happens if air dissects along tissue planes from the mediastinum?

    <p>Produces subcutaneous emphysema</p> Signup and view all the answers

    What is a common complication associated with mechanical ventilation and barotrauma?

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

    Which of the following is least likely to be a result of a pneumothorax?

    <p>Increased lung compliance</p> Signup and view all the answers

    What characteristic finding might suggest a pneumothorax upon physical examination?

    <p>Absence of breath sounds</p> Signup and view all the answers

    What is associated with a reduced incidence of barotrauma?

    <p>Lower tidal volume</p> Signup and view all the answers

    What can occur as a result of a pneumothorax?

    <p>Lung collapse with mediastinal shifting</p> Signup and view all the answers

    How can a pneumothorax be detected physically?

    <p>Resonant or hyperresonant percussion note</p> Signup and view all the answers

    What is indicated by chest radiographs in the case of a pneumothorax?

    <p>Lack of vascular markings</p> Signup and view all the answers

    What treatment is usually required for a significant pneumothorax?

    <p>Placement of a chest tube</p> Signup and view all the answers

    In a supine patient, where is pneumothorax most likely to be located?

    <p>Anterior surface of the lung</p> Signup and view all the answers

    What complication can arise from air dissecting along tissue planes near the heart?

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

    What may interfere with the detection of a small pneumothorax in a supine patient?

    <p>Air under the diaphragm in peritoneum</p> Signup and view all the answers

    What is the result of auto positive end-expiratory pressure (PEEP) on lung volume?

    <p>It causes progressive air trapping in the lungs.</p> Signup and view all the answers

    During which phase of respiration is auto-PEEP most likely to occur?

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

    How does the flow-time waveform differ in a patient with air trapping compared to a normal expiratory pattern?

    <p>It rises continuously without returning to zero.</p> Signup and view all the answers

    What does the dotted line in the flow-time waveform represent?

    <p>Normal expiratory flow pattern</p> Signup and view all the answers

    Which of the following best describes functional residual capacity (FRC)?

    <p>The volume of air remaining in the lungs after normal expiration.</p> Signup and view all the answers

    What impact does positive pressure ventilation have on the pulmonary system?

    <p>It may lead to increased auto-PEEP.</p> Signup and view all the answers

    Why is air trapping considered detrimental in patients with obstructive lung disease?

    <p>It causes lung overinflation.</p> Signup and view all the answers

    What occurs to tidal volume (VT) during episodes of air trapping in the lungs?

    <p>It decreases significantly.</p> Signup and view all the answers

    What does the Braschi valve primarily measure in the positive pressure ventilation system?

    <p>Auto positive end-expiratory pressure</p> Signup and view all the answers

    What happens to the exhalation valve during the process of positive pressure ventilation?

    <p>It opens to allow air to flow out</p> Signup and view all the answers

    Which component connects to the inspiratory side of the ventilation circuit?

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

    What is the significance of maintaining proper pressures in a positive pressure ventilation system?

    <p>To ensure adequate oxygenation and ventilation</p> Signup and view all the answers

    What might occur if the pressure manometer indicates an abnormal reading?

    <p>There may be a leak or malfunction in the system</p> Signup and view all the answers

    What causes the patient to forcibly inhale or exhale during positive pressure ventilation?

    <p>The reduction in their active breathing efforts</p> Signup and view all the answers

    Which of the following best describes a one-way valve in the context of the ventilation circuit?

    <p>It prevents exhaled air from re-entering the circuit</p> Signup and view all the answers

    In the context of ventilation pressure measurements, what does a pressure of P0 signify?

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

    What type of lung injury is caused by the repeated opening and closing of lung units in ARDS?

    <p>Shear stress</p> Signup and view all the answers

    What is a consequence of shear stress in adjacent unstable alveoli?

    <p>Alveolar rupture</p> Signup and view all the answers

    What transpulmonary pressure is associated with significant stress exerted between adjacent alveoli?

    <p>30 cm H2O</p> Signup and view all the answers

    What is referred to as atelectrauma?

    <p>Alveolar rupture and instability</p> Signup and view all the answers

    What happens to surfactant molecules during the repeated opening and closing of alveoli?

    <p>They experience molecular reorientation.</p> Signup and view all the answers

    What are potential results of microvascular injury due to shear stress?

    <p>Decreased oxygen transfer efficiency</p> Signup and view all the answers

    In the context of lung injury, what is the effect of high airway pressure on collapsed alveoli?

    <p>It worsens their instability.</p> Signup and view all the answers

    What structural damage might occur due to the forces exerted on lung tissues during ARDS?

    <p>Tearing of the alveolar epithelium</p> Signup and view all the answers

    Study Notes

    Effects of Positive Pressure Ventilation on the Pulmonary System

    • Positive pressure ventilation carries inherent risks and complications including ventilator-associated and ventilator-induced lung injury, gas distribution/blood flow effects, hypo/hyperventilation, air trapping, oxygen toxicity, increased work of breathing (WOB), patient-ventilator asynchrony, mechanical problems, and artificial airway complications.

    • Lung Injury: High pressures (greater than 45cm H₂O) and volumes (10-12 mL/kg) during ventilation can cause lung injury (barotrauma, volutrauma). Volutrauma stems from overdistention due to high volumes, while barotrauma is caused by high pressures.

    • Barotrauma (Extraalveolar Air): Positive pressure ventilation can cause alveolar rupture, leading to extraalveolar air leaks like subcutaneous emphysema, pneumothorax, pneumomediastinum, pneumoperitoneum, and pneumopericardium. This is a significant risk, particularly in patients with lung bullae or chest injury. Factors that increase risk are high peak airway pressures with low end-expiratory pressure, bullous lung disease (emphysema, tuberculosis), high levels of positive end-expiratory pressure (PEEP) with high tidal volumes (VT), aspiration of gastric acid, and necrotizing pneumonias.

    • Pneumothorax: Extraalveolar air may accumulate in the pleural space, causing lung collapse and mediastinal shift. Diagnosis involves percussion (hyperresonance), absence of breath sounds, and imaging (radiographs). Treatment involves chest tube insertion.

    • Tension Pneumothorax: A life-threatening complication where air is trapped in the pleural space, causing pressure buildup that shifts mediastinal structures. Immediate intervention is required.

    • Pneumomediastinum: A more diffuse air-filled space surrounding the lung.

    • Subcutaneous Emphysema: Air in the subcutaneous tissues, characterized by crepitus.

    • Pneumoperitoneum: Air in the peritoneal cavity, potentially causing diaphragm dysfunction.

    • Biotrauma: Repeated opening/closing of lung units during ventilation creates shear stress and surfactant loss. Excessive opening and closing of lung units may also affect inflammatory mediators potentially leading to multisystem organ failure (biotrauma).

    • Ventilator-Associated Lung Injury (VALI): Lung injury resulting from mechanical ventilation.

    • Ventilator-Induced Lung Injury (VILI): Microscopic lung injury occurring at the level of the acinus, it resembles ARDS. Difficult to diagnose in humans.

    Chest Wall and Transpulmonary Pressures

    • Transpulmonary Pressure (PL): Difference between alveolar (airway) pressure and intrapleural pressure.
    • High PL values increase risk of lung injury.

    Chest Wall Compliance and Protection from Overdistention

    • Forces from ribs, muscles, diaphragm and abdomen create chest wall pressure.
    • Forces on the diaphragm and vena cava increase with abdominal pressure (>20cmH2O).

    Difficulty Triggering in Patients With Chronic Obstructive Pulmonary Disease (COPD)

    • Reduced inspiratory capacity with increased WOB, decreased VE.
    • Indicators of difficulty are: progressive peak pressure increase, decreased tidal volume.

    Acid-Base Imbalances

    • Hypoventilation: Increased PaCO₂ (hypercapnia) and acidosis (leading to right shift in oxyhemoglobin dissociation curve, reduced capacity to carry O₂), possible coma.
    • Hyperventilation: Reduced PaCO₂ and alkalosis (leading to left shift of oxyhemoglobin dissociation curve, reduced O₂ delivery). Possible tetany, cerebral hypoxia.

    Clinical and Electrocardiographic (ECG) Changes Associated With Respiratory Acidosis and Alkalosis

    • Clinical signs: Cool skin (decreased PaCO₂), twitching, tetany.
    • ECG changes: Elevated and peaked T waves, ST-segment depression, widened QRS complexes, prolonged P-R interval (with hypokalemia).
    • ECG changes: Prolonged Q-T interval, low, rounded T waves, depressed ST segment, inverted T waves, inverted P waves, atrioventricular block, premature ventricular contractions, paroxysmal tachycardia, and atrial flutter (with hypokalemia).

    Air Trapping (Auto-PEEP)

    • Auto-PEEP is increased airway resistance during exhalation, caused by the time taken to exhale.
    • Factors that increase risk are airway obstruction (COPD, asthma), short expiratory times, and mechanical devices that impede exhalation.
    • This leads to an increase in functional residual capacity (FRC), reduced venous return, and increased cardiac workload.

    Work of Breathing (WOB)

    • Normal WOB is about 0.5 J/L. High WOB (>1.5J/L) leads to fatigue and difficulty weaning.
    • Methods to reduce WOB include use of proper ET size, minimizing auto-PEEP and using appropriate ventilator settings (e.g., higher flow rate, shorter inspiratory time).

    Patient-Ventilator Synchrony

    • Trigger, flow, cycle, and mode synchrony can be difficult due to the delay in sensor response.
    • Auto-PEEP can hinder patient-ventilator synchrony.

    Ventilator Mechanical and Operational Hazards

    • Malfunctions like disconnection, power issues, alarm failures, or humidification/heating issues can occur.
    • Inadequate alarm systems and staffing issues can make detection and intervention of failures more difficult.
    • Mechanical/operational issues can increase complications.

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