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  <head>
    <title>014-02 Time constants, respiratory load, and ventilatory-support reasoning</title>
    <ownerName>Integrated Medical Foundations</ownerName>
  </head>
  <body>
    <outline text="Time constants, load, and ventilatory-support reasoning">
      <outline text="Time constants and uneven emptying">
        <outline text="Time constant is resistance times compliance"/>
        <outline text="High resistance or compliance empties slowly"/>
        <outline text="Stiff units accept little volume but fill quickly"/>
        <outline text="Disease broadens the distribution of time constants"/>
        <outline text="Short expiratory time traps gas in slow units"/>
        <outline text="The next breath starts above resting volume">
          <outline text="Dynamic hyperinflation and intrinsic positive pressure"/>
        </outline>
        <outline text="Longer expiratory time reduces trapping"/>
      </outline>
      <outline text="Reading airway pressure">
        <outline text="Stiff lungs need higher pressure per volume"/>
        <outline text="Peak pressure holds resistive and elastic components"/>
        <outline text="An inspiratory pause estimates plateau pressure">
          <outline text="Plateau reflects alveolar and chest-wall elastic pressure"/>
        </outline>
        <outline text="High peak with lower plateau: airway resistance"/>
        <outline text="Both high: low compliance or excessive volume"/>
        <outline text="Chest-wall load raises pressure without lung stress">
          <outline text="Oesophageal pressure estimates pleural pressure"/>
        </outline>
      </outline>
      <outline text="Load, power, and muscle endurance">
        <outline text="Recoil, resistance, intrinsic pressure, external apparatus"/>
        <outline text="Power also depends on rate and flow"/>
        <outline text="Hyperinflation shortens and flattens the diaphragm"/>
        <outline text="Malnutrition, sepsis, steroids, neuropathy weaken force"/>
        <outline text="Fever, acidosis, dead space raise demand"/>
        <outline text="Failure when load exceeds neuromuscular capacity"/>
        <outline text="Slowing rate in an exhausted patient is ominous"/>
        <outline text="Great effort with small movement needs urgent support"/>
      </outline>
      <outline text="Flow limitation and bronchodilator logic">
        <outline text="Medium bronchi carry most normal resistance"/>
        <outline text="Parallel small airways matter once widely narrowed"/>
        <outline text="Small-airway disease precedes obvious spirometry change"/>
        <outline text="Bronchodilators do not clear mucus or fibrosis"/>
        <outline text="Limited response does not exclude benefit or asthma"/>
        <outline text="Delivery depends on particle size and inspiratory flow">
          <outline text="Spacers cut coordination demand, dry powder needs flow"/>
        </outline>
      </outline>
      <outline text="Control of breathing and compensation">
        <outline text="Central receptors sense carbon dioxide derived acidity"/>
        <outline text="Metabolic hydrogen ions cross the barrier poorly">
          <outline text="Peripheral receptors give the rapid metabolic response"/>
        </outline>
        <outline text="Drive blunted by opioids, sedation, sleep, adaptation"/>
        <outline text="Drive raised by pain, fever, pregnancy, acidosis"/>
        <outline text="Judge carbon dioxide against the expected drive"/>
        <outline text="High bicarbonate may hide a metabolic alkalosis"/>
      </outline>
      <outline text="Non-invasive support">
        <outline text="Continuous pressure raises pressure through the cycle">
          <outline text="Splints airway, recruits alveoli, raises residual capacity"/>
          <outline text="Reduces left-ventricular afterload"/>
          <outline text="No separate inspiratory pressure boost"/>
        </outline>
        <outline text="Bilevel difference supports volume and carbon dioxide clearance"/>
        <outline text="Expiratory pressure offsets intrinsic positive pressure">
          <outline text="Excess worsens hyperinflation and venous return"/>
        </outline>
        <outline text="Failure: acidosis, drowsiness, refractory hypoxaemia, exhaustion"/>
      </outline>
      <outline text="Invasive ventilation and lung stress">
        <outline text="Volume control fixes volume, pressure control limits pressure"/>
        <outline text="Neither mode is protective by itself"/>
        <outline text="Volutrauma, barotrauma, atelectrauma, biotrauma"/>
        <outline text="Extreme drive causes self-inflicted lung injury"/>
        <outline text="Excess positive pressure overdistends and raises dead space">
          <outline text="It impairs venous return and right-ventricular afterload"/>
        </outline>
        <outline text="Not every opaque region is safely recruitable"/>
        <outline text="Dyssynchrony: check trigger, flow, intrinsic pressure first"/>
      </outline>
      <outline text="Weaning, secretions, and extubation">
        <outline text="The breathing trial tests several systems together"/>
        <outline text="Negative pressure raises venous return and afterload">
          <outline text="Oedema despite an improving lung infection"/>
        </outline>
        <outline text="Extubation needs patency, cough, alertness, a plan"/>
        <outline text="Passing a trial does not guarantee airway protection"/>
        <outline text="Prolonged intubation brings pneumonia and weakness"/>
        <outline text="Humidification, mobilisation, suction, physiotherapy move secretions"/>
        <outline text="Adequate tidal volume with weak expiratory force"/>
      </outline>
      <outline text="Naming the failure and reviewing settings">
        <outline text="Name the failing component explicitly">
          <outline text="Drive, pump, chest wall, airway, parenchyma, circulation"/>
        </outline>
        <outline text="State whether support reduces load and protects tissue"/>
        <outline text="Escalation without a causal statement treats numbers"/>
        <outline text="Reducing sedation watches pain, delirium, drive, dyssynchrony">
          <outline text="Over-sedation blocks assessment, cough, mobilisation, weaning"/>
          <outline text="Inadequate analgesia generates dangerous effort and demand"/>
        </outline>
        <outline text="State target depth, accumulation, withdrawal risk"/>
        <outline text="Support sleep, orientation, family contact, early movement"/>
        <outline text="After a change check the effect and new harm">
          <outline text="Plateau, driving pressure, end-expiratory flow, right heart"/>
        </outline>
        <outline text="Higher saturation can accompany overall worsening"/>
      </outline>
    </outline>
  </body>
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