Respiratory Failure – COPD and Asthma 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. 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. Initial CXR 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 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? What are the factors that influence respiratory muscle strength? – Consider: Fatigue Malnutrition Hypoperfusion Myopathy Steroids Electrolyte derangements What are the factors that influence respiratory muscle load? – Consider: Bronchospasm Secretions Dynamic hyperinflation Atelectasis Increase CO2 production Infection Pneumothorax Abdominal distension What is the relationship between respiratory muscle strength and load in acute on chronic respiratory failure? The patient’s 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? 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? 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? 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. 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? 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? CXR 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? 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 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? 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? Question??