chapter 41. quiz 5. respiratory mechanics
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Questions and Answers

What is the primary function of the human respiratory system?

  • To regulate body temperature
  • To filter out toxins from the bloodstream
  • To facilitate the exchange of oxygen and carbon dioxide (correct)
  • To pump blood throughout the body

    • What is created to facilitate the transport of air to the alveoli and alveolar gas to the environment?

  • A temperature gradient
  • A pressure gradient (correct)
  • A humidity gradient
  • A pH gradient

    • What characterizes the lung's complex branching network of airway segments and viscoelastic tissues?

  • Tremendous variations in gas velocities and flow regimens (correct)
  • Complete absence of gas flow
  • Minimal changes in tissue velocity
  • Uniform gas velocities and flow regimens

    • What three forces must be overcome to move gas into and out of the lungs?

    <p>Resistive, elastic, and inertial forces</p> Signup and view all the answers

    What is the equation that describes the mechanical behavior of the total respiratory system?

    <p>P = PR + PE + PI</p> Signup and view all the answers

    What is the term used do describe airway pressure relative to atmosphere ?

    <p>Transrespiratory pressure</p> Signup and view all the answers

    What is the term used do describe airway pressure relative to pleural pressure ?

    <p>transpulmonary pressure</p> Signup and view all the answers

    What is assumed to be linearly related to flow in the context of respiratory mechanics?

    <p>Resistive pressure losses</p> Signup and view all the answers

    Which of the following is a source of resistive properties in the respiratory system described in the text?

    <p>all of the above</p> Signup and view all the answers

    What happens to resistive pressure losses with more rapid flow rates in the respiratory system?

    <p>They vary nonlinearly</p> Signup and view all the answers

    What do the coefficients R, E, and I represent when P refers to transrespiratory pressure for the respiratory system mechanics?

    <p>Total respiratory system</p> Signup and view all the answers

    What components contribute to the resistive properties of the respiratory system mentioned in the text?

    <p>Parenchymal and chest wall tissues</p> Signup and view all the answers

    airway resistance may reflect

    <p>airway caliber</p> Signup and view all the answers

    What is the relationship between tissue resistive losses and breathing frequency according to the text?

    <p>Inversely proportional</p> Signup and view all the answers

    In adult patients, what percentage of subglottal total lung resistance is attributed to lung tissue resistance at typical breathing rates?

    <p>80%</p> Signup and view all the answers

    What is the collective name given to losses that are proportional to flow in the context of respiratory mechanics?

    <p>Resistive losses</p> Signup and view all the answers

    What does the difference between Ppeak and Pplat represent in volume-cycled ventilation?

    <p>The resistive pressure loss</p> Signup and view all the answers

    What is the purpose of estimating resistance during volume-cycled ventilation with an end-inspiratory pause?

    <p>To detect airway caliber changes during an intraoperative asthma exacerbation , or obstruction within the ETT</p> Signup and view all the answers

    What can cause alterations in the resistive pressure loss (PR) during volume-cycled ventilation?

    <p>All of the above</p> Signup and view all the answers

    What is the formula to estimate the resistance (R) during volume-cycled ventilation?

    <p>R = Ppeak - Pplat / VI</p> Signup and view all the answers

    which of the following represent increased resistance?

    <p>middle diagram</p> Signup and view all the answers

    What is elastance defined as in the context of respiratory mechanics?

    <p>Pressure change per unit volume</p> Signup and view all the answers

    In the total respiratory system elastance calculation, what do EL and Ecw represent?

    <p>Lung elastances and chest wall elastances</p> Signup and view all the answers

    Which type of elastance refers to the change in elastic distending pressure per unit volume during breathing or ventilation?

    <p>Dynamic elastance</p> Signup and view all the answers

    What causes elastic pressures in the respiratory system?

    <p>recoil of the lungs and chest wall</p> Signup and view all the answers

    What is the mathematical relationship between the total respiratory system elastance, lung elastance, and chest wall elastance in the form of compliance ?

    <p>1/Crs = 1/CL + 1/CW</p> Signup and view all the answers

    What is the effect of emphysema on lung?

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

    What is a factor that reduces chest wall compliance?

    <p>Abdominal distension</p> Signup and view all the answers

    What is the term used to describe the reciprocal of elastance?

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

    What is a factor that increases total respiratory or lung elastance?

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

    which of the following represent increased elastance?

    <p>right diagram</p> Signup and view all the answers

    What can be determined by dividing the difference between Pplat and PEEP by VT during volume-cycled ventilation?

    <p>Total respiratory system elastance</p> Signup and view all the answers

    when the respiratory system elastance should be determined during ventilation?

    <p>during periods of high-flow</p> Signup and view all the answers

    Which factor is used to determine respiratory system elastance during the end-inspiratory pause in volume-cycled ventilation?

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

    What parameter is calculated by the difference between Pplat and PEEP in the context of respiratory mechanics?

    <p>Elastic pressure</p> Signup and view all the answers

    what is the formula provided for determining elastance ?

    <p>Ers = Pplat − PEEP / VT</p> Signup and view all the answers

    What is the typical range of static respiratory system compliance in normal mechanically ventilated lungs?

    <p>50-100 mL/cm H2O</p> Signup and view all the answers

    What is the effect of a recruitment maneuver on Ers?

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

    Why may Ers increase due to strain stiffening of lung tissues?

    <p>Because collagen fibers become load-bearing elements</p> Signup and view all the answers

    What is the goal of titrating PEEP to achieve an optimal balance between intratidal recruitment and parenchymal overdistention?

    <p>To maximize Crs</p> Signup and view all the answers

    which of the following can alter lung or chest wall elastance during a specified tidal volume ventilation and lead to Alterations in pressure elastance (PE) ?

    <p>all of the above</p> Signup and view all the answers

    Why is dynamic Ers higher than static elastance?

    <p>Due to viscoelasticity and gas redistribution</p> Signup and view all the answers

    What is the cause of increasing strain and load-bearing elements within the lung tissues?

    <p>Collagen fibers become more dominant</p> Signup and view all the answers

    What is the purpose of titrating PEEP to achieve an optimal balance?

    <p>To minimize Ers and maximize Crs</p> Signup and view all the answers

    What is the effect of strain stiffening on lung tissues?

    <p>Ers increases</p> Signup and view all the answers

    What is the relationship between elastin and collagen fibers at low levels of tissue strain?

    <p>Elastin fibers are the dominant</p> Signup and view all the answers

    What is typically associated with the kinetic energy of accelerating the gas column in the central airways?

    <p>Inertial pressures</p> Signup and view all the answers

    In which situations is inertia a significant contributor to the apparent airway pressure or the work of breathing?

    <p>During sudden changes in air flow</p> Signup and view all the answers

    What is inertial pressure typically expressed as the product of?

    <p>A lumped &quot;inertia&quot; parameter and volume acceleration</p> Signup and view all the answers

    What is the primary contributor to the inertial pressure during respiratory motion?

    <p>Gas column acceleration</p> Signup and view all the answers

    Why can't Rrs and Ers be estimated without an end-inspiratory pause in the ventilator waveform?

    <p>The resistive and elastic pressures cannot be separated visually.</p> Signup and view all the answers

    During pressure-controlled ventilation, what determines airway flow and VT?

    <p>Gradient between airway and alveolar pressures</p> Signup and view all the answers

    When are dynamic estimates of total respiratory Rrs and Ers valid?

    <p>During controlled modes of ventilation with a relaxed chest wall</p> Signup and view all the answers

    In which situations can the mechanics of the chest wall be accounted for when estimating transpulmonary pressure?

    <p>With the use of esophageal manometry</p> Signup and view all the answers

    What method is suggested for more robust estimates of respiratory Rrs and Ers without an end-inspiratory pause?

    <p>Multiple linear regression analysis</p> Signup and view all the answers

    How is elastance (compliance) most easily measured according to the text?

    <p>during periods of zero flow</p> Signup and view all the answers

    When can quasi-static PV curves be constructed according to the text?

    <p>during very slow inflations/deflations</p> Signup and view all the answers

    the expiratory limb of PV curve can be constructed by ?

    <p>inflating the lungs to TLC</p> Signup and view all the answers

    What defines compliance according to the text?

    <p>The slope of pressure-volume curve</p> Signup and view all the answers

    What does the lower inflection point (LIP) reflect when using sigmoidal functions to describe curves in the context?

    <p>Maximum alveolar recruitment</p> Signup and view all the answers

    Why is it crucial to apply enough PEEP during protective ventilation?

    <p>to avoid lower inflection point</p> Signup and view all the answers

    What phenomenon occurs in PV curves due to lung volume being dependent on the direction of distending pressure during inspiration or expiration?

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

    During protective ventilation, why is it advised to avoid the upper inflection point (UIP)?

    <p>To prevent alveolar overdistention</p> Signup and view all the answers

    What should be done in protective ventilation to avoid the lower inflection point (LIP)?

    <p>Apply Enough PEEP levels</p> Signup and view all the answers

    What should be done in protective ventilation ?

    <p>apply Enough PEEP and low tidal volume</p> Signup and view all the answers

    What is a limitation of managing ventilation based on quasi-static PV curves?

    <p>PV curves do not reflect lung mechanics during dynamic breathing processes</p> Signup and view all the answers

    What is the work of breathing represented as?

    <p>The product of the applied distending pressure and resulting volume change</p> Signup and view all the answers

    Why is the work of breathing assessed during inspiration only?

    <p>Because the respiratory musculature must overcome both elastic and resistive pressures to bring air into the lungs</p> Signup and view all the answers

    What is the frequency at which energy expenditure is minimized?

    <p>The energetically optimum breathing frequency</p> Signup and view all the answers

    What is mechanical power an index of?

    <p>The rate of energy dissipation</p> Signup and view all the answers

    Why is mechanical power used to assess the risk of developing ventilator-induced lung injury?

    <p>Because it is an index of the rate of energy dissipation</p> Signup and view all the answers

    What is the purpose of assessing the work of breathing?

    <p>To assess the risk of developing ventilator-induced lung injury</p> Signup and view all the answers

    monitoring of respiratory pressure can be measured in?

    <p>all of the above</p> Signup and view all the answers

    Why is airway pressure during controlled mechanical ventilation not the actual pressure at the airway opening?

    <p>Due to the resistive and compliant properties of the breathing circuit and face mask/ETT</p> Signup and view all the answers

    What is often improperly used as a surrogate for lung distension?

    <p>Airway pressure</p> Signup and view all the answers

    Where can pressure be measured in order to monitor respiratory pressures?

    <p>All of the above</p> Signup and view all the answers

    What does the pressure measured in the trachea or at the airway opening represent?

    <p>The pressure transduced at the anesthesia machine or ventilator</p> Signup and view all the answers

    What is transrespiratory pressure determined by?

    <p>The difference between airway pressure and atmospheric pressure</p> Signup and view all the answers

    Which of the following may contribute to high airway opening pressures?

    <p>Obesity, abdominal insufflation, and steep Trendelenburg position</p> Signup and view all the answers

    What does increased transrespiratory pressure not necessarily indicate?

    <p>Parenchymal overdistention</p> Signup and view all the answers

    What is transrespiratory pressure a measure of?

    <p>The pressure difference between the lungs and chest wall</p> Signup and view all the answers

    What is transpulmonary pressure a measure of?

    <p>The distending pressure across the lungs alone</p> Signup and view all the answers

    How can transpulmonary pressure be obtained non-invasively?

    <p>Using an esophageal balloon catheter</p> Signup and view all the answers

    Why is the esophageal balloon catheter several centimeters long?

    <p>To provide an average estimate of the pressure field surrounding the lungs</p> Signup and view all the answers

    What is a limitation of esophageal manometry?

    <p>All of the above</p> Signup and view all the answers

    In which situations is the use of esophageal manometry valuable?

    <p>All of the above</p> Signup and view all the answers

    How is the esophageal balloon catheter typically positioned?

    <p>Through the mouth or nose and into the middle-to-distal third of the esophagus</p> Signup and view all the answers

    transpulmonary pressure measurements are valuable in ?

    <p>adjustment of appropriate levels of PEEP</p> Signup and view all the answers

    What is required to measure transpulmonary pressure?

    <p>Measurement of airway opening pressure and estimates of the pressure within the pleural space</p> Signup and view all the answers

    Where is the pressure measured to estimate intrapleural pressure?

    <p>In the esophagus</p> Signup and view all the answers

    What is recommended to limit in order to minimize alveolar overdistension?

    <p>Plateau pressures</p> Signup and view all the answers

    Which respiratory variable is considered one of the most important when stratifying mortality risk during ARDS?

    <p>Driving pressure</p> Signup and view all the answers

    What does the driving pressure involve in its computation?

    <p>Pplat and PEEP</p> Signup and view all the answers

    the same plateau pressure could correspond to ?

    <p>very different transpulmonary pressures</p> Signup and view all the answers

    to minimize alveolar overdistension, recommendations suggest limiting plateau pressures to ?

    <p>26-30 cm H2O</p> Signup and view all the answers

    What is auto-PEEP that is typically observed in ventilated patients with COPD caused by?

    <p>positive pressure present within the alveoli at end-exhalation</p> Signup and view all the answers

    How can the amount of auto-PEEP be estimated in mechanically ventilated patients?

    <p>By occluding the airway at end exhalation</p> Signup and view all the answers

    Consequences of of auto-PEEP?

    <p>significant respiratory and hemodynamic compromise</p> Signup and view all the answers

    How is auto-PEEP can be assess in spontaneously breathing patients ?

    <p>by esophageal balloon</p> Signup and view all the answers

    What is a primary cause of auto-PEEP in patients with ARDS, sepsis, and respiratory muscle weakness?

    <p>Combination of increased airway resistance and reduced lung elastic recoil</p> Signup and view all the answers

    factors that can contribute to Auto-PEEP/intrinsic-PEEP ?

    <p>all the answers are correct</p> Signup and view all the answers

    Where should the flow-measuring device be placed for accurate measurement?

    <p>Between the circuit Y-connector and the proximal end of the ETT/LMA</p> Signup and view all the answers

    What is a clinical use of flow monitoring?

    <p>Detection of nonzero end-expiratory flows</p> Signup and view all the answers

    What can occur if auto-PEEP is not addressed?

    <p>Increased risk of lung hyperinflation and reduction of venous return</p> Signup and view all the answers

    where most ventilators and anesthesia machines measure flow?

    <p>close to machine</p> Signup and view all the answers

    What can be done to eliminate auto-PEEP?

    <p>Increase expiratory time and reduce the tidal volume and respiratory rate</p> Signup and view all the answers

    What is a limitation of measuring flow close to the ventilator?

    <p>Flow rates may differ from those at the patient's lungs</p> Signup and view all the answers

    What is the most common method to infer airway flow during ventilation?

    <p>Measurement of a differential pressure decrease across a fluid resistive element</p> Signup and view all the answers

    Why are pneumotachographs not used routinely?

    <p>They are sensitive to temperature and humidity, and difficult to clean and sterilize</p> Signup and view all the answers

    What is an advantage of orifice flowmeters?

    <p>They have a large internal diameter that limits the formation of condensation and minimizes obstruction</p> Signup and view all the answers

    What is used in most anesthesia machines for flow measurement?

    <p>Hot wire anemometers</p> Signup and view all the answers

    What is required for sensing bidirectional flow in a single conduit using hot wire anemometers?

    <p>Two wires in series</p> Signup and view all the answers

    Why do hot wire anemometers require calibration?

    <p>To account for variations in gas density or humidity</p> Signup and view all the answers

    What is an advantage of hot wire anemometers compared to pneumotachographs and orifice flowmeters?

    <p>They have a better dynamic response</p> Signup and view all the answers

    how most anesthesia machines and ventilators determine volume ?

    <p>electrically/numerically integrating the corresponding flow signal.</p> Signup and view all the answers

    Why is accurate measurement of volume essential in anesthesia machines and ventilators?

    <p>To accurately account for gas quantity</p> Signup and view all the answers

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