Respiratory Failure

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Respiratory Failure COPD and Asthma
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• 59 year old man presents to the ER with a 3 day
  history of progressively worsening shortness of
  breath.
• He has a past history of chronic lung disease
  that started about 5 years ago and he is an
  ex-smoker for about 6 months since his family
  doctor threatened to put him on home oxygen.

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• What additional information do you want on
  history?
• The patient states that he has had a chronic
  productive cough for years and over the last week
  he has noticed a changed in the amount and color
  of his sputum.
• Denies any recent travel, sick contacts (although
  grandkids visited about 10 days ago), fevers,
  chest pain, orthopnea, past hospitalizations or
  surgeries.
• Still works as an accountant.

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Initial CXR
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• On examination, his chest sounds are distant with
  some wheeze and prolonged exhalation. Heart
  sounds are difficult to hear.
• He is unable to speak in complete sentences and
  is in moderate to severe respiratory distress.
• Room air ABG pH 7.19, PCO2 76, PO2 53, HCO3 35
• WBC 12.7, Bands 9, Hgb 186, Platelets 250

6

• What is the most likely diagnosis?
• What is the differential diagnosis?
• Why is the PCO2 elevated?
• What are the determinants of blood CO2
  concentrations?
• What is dead space ventilation and what is the
  difference between anatomical and physiological
  dead space?
• How is dead space ventilation different from
  shunt?
• Why is the PO2 low?

7

• What are the factors that influence respiratory
  muscle strength?
• Consider
• Fatigue
• Malnutrition
• Hypoperfusion
• Myopathy
• Steroids
• Electrolyte derangements

8

• What are the factors that influence respiratory
  muscle load?
• Consider
• Bronchospasm
• Secretions
• Dynamic hyperinflation
• Atelectasis
• Increase CO2 production
• Infection
• Pneumothorax
• Abdominal distension

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• What is the relationship between respiratory
  muscle strength and load in acute on chronic
  respiratory failure?
• The patients respiratory distress has not
  improved with all of this physiology talk.
• What is the approach to the treatment of acute on
  chronic respiratory failure in the emergency
  department?

10

• After starting frequent bronchodilators, steroids
  and empiric antibiotics, the patient is not
  feeling better.
• What is the role for non-invasive positive
  pressure ventilation for this problem?
• What are the indications and contraindications
  for NIPPV?
• How does NIPPV work in acute on chronic
  respiratory failure?

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• After applying NIPPV, the patient begins to feel
  better and eventually is transferred to the ward.
• If he had not improved, how would you know and
  what would you do?
• Bonus question What causes the PCO2 to rise on
  high flow oxygen? How common is it? Which is
  more harmful hypercarbia or hypoxemia?

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Next Case

• 19 year old woman with a 12 year history of
  asthma presents to the ER with 3 day history of
  increasing shortness of breath and cough.
• She recently rescued a cat from the pound and
  started dating a boy who smokes.
• She has been to the ER about one per year for
  asthma attacks, admitted twice and never in ICU.
• She uses ventolin about 6 times per day.

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• On examination, she is in severe respiratory
  distress with a rate of 31, pulse 124, and O2
  saturations of 100 on face mask.
• Her blood pressure is 151/83 with a pulsus
  paradoxus of 25.
• What is a pulsus paradoxus?
• If her pulsus was 15, would you be reassured?

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• What investigations would you order?
• What treatments would you order?
• What is the role of heliox and non-invasive
  positive pressure ventilation in severe asthma?
• Her ABG on face mask is pH 7.20, PCO2 35, PO2
  123, HCO3 17
• Is this a reassuring ABG? Why or why not?

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CXR
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• After 35 minutes of continuous therapy, her work
  of breathing is about the same, she can speak in
  short words only and is becoming difficult to
  arouse.
• What do you do next?
• What are the indications for intubation in severe
  asthma?

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• She is successfully intubated on the first
  attempt. Immediately after her blood pressure
  starts to fall and she becomes pulseless but the
  monitor still shows electrical activity.
• What could be causing this PEA arrest?
• Consider
• Hypovolemia
• Loss of vascular tone
• Pneumothorax
• Electrolyte disorders especially pH
• Overventilation on the Ambu Bag

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• The RT reports that she is very stiff to bag but
  after disconnecting her from the bag and waiting
  30 seconds, she regains a pulse.
• What is dynamic hyperinflation?
• What are the consequences of dynamic
  hyperinflation?

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• Now that she is on the ventilator and more
  stable, what treatments would you use for her
  asthma?
• How would you ventilate her?
• Despite permissive hypercarbia, she is still
  difficult to ventilate?
• What other treatments are available?

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Question??