Acute Respiratory Failure and Asthma

1. Acute Respiratory Failure and Asthma Anthony Saleh, MD, FCCP March 18th, 2011

2. Disclosures • No financial disclosures • Avid New York Yankee fan • Michael Jordan admirer • Favorite movie: “Godfather 1” • Major supporter of respiratory therapists

3. Outline • Scope of the problem • Pathophysiology • Management • Invasive/ Non invasive • Specific Ventilatory Strategies

4. Asthma: Definition • A chronic inflammatory disorder of the airways in which many cells and cellular elements play a role • Susceptible patients develop recurrent episodes of wheezing, chest tightness, and coughing, especially at night or in the early morning • These episodes are associated with widespread but variable airflow obstruction, that is often reversible

5. Prevalence • Increasing worldwide over the past few decades • In the United States approximately 16.1 million adults and 6.8 million children have a diagnosis of asthma • Overall prevalence about 8 % • Fatalities slowly declining, but still excessive • Multiple etiologies for poor outcome

6. Asthma Fatalities (cont) • Peaked in 2003 • Higher death rates in: Older patients (greater than 65), females, Puerto Ricans, non Hispanic blacks • Some proposed mechanisms: Inner city lower socioeconomic class • Lack of education • Health care disparities

7. Pathophysiology • A complex inflammatory disease of the airways • Inflammation is the hallmark with ensuing complicated cascades • A variety of pathways are intertwined • Treatment focuses on multiple different sites of inflammatory activity

8. Management • Acute, severe asthma remains a very difficult issue • Patients typically have persistent reductions in peak expiratory flow rates of less than 40% predicted • May have progressive hypercarbia, altered sensorium, and a marked increase in work of breathing

9. Management (cont) • Pharmacologic interventions: • Frequent, aggressive bronchodilators • Systemic corticosteroids mandated • Oxygen therapy to prevent desaturations • +/- intravenous magnesium sulfate

10. Yankee Trivia • What is Mariano Rivera’s post season ERA?

11. Answer • 0.71 (an all time low)

12. Godfather Trivia • How many shots were fired at Don Corleone (and how many hit him??)

13. Answer • 9 fired • 5 successful (but he survived)

14. Respiratory Therapy Trivia • How can you get a patient on VDR ventilation?

15. Answer • Make Felix (the “Don of VDR”) Khusid an offer he can’t refuse!!

16. Non Invasive Ventilation in Asthma • Paucity of studies to support it’s use • Advantages seen in other entities (COPD, pulmonary edema) not matched in well controlled studies • Theoretical improvement yet to be proven in well designed trials

17. NIPPV in Asthma (cont) • 1st study: Soroksky A. Stav D. Shpirer I. Chest 2003; 123: 1018-1025 • Randomized double blind, placebo controlled trial conducted in the emergency department of an Isreali hospital • NIPPV group: 17 patients • Control group: 16 patients

18. Soroksky Study (cont) • 4 criteria had to be fulfilled: • FEV1<60% predicted • RR>30 breaths/minute • Asthma of at least 1 years duration • Duration of current attack >7 days • PCO2 not an entry criterion

19. Soroksky Study (Results) • NPPV group had a pressure range 8-15 cm IPAP and up to 5 cm EPAP • Study patients had an improvement in: • More rapid improvement in lung function • Respiratory rate • Decreased hospitalizations • Small trial---uncertain clinical significance

20. NIPPV in Asthma • Next study: Murase, et al. Respirology 2010; 15: 714-720 • Retrospective cohort study • Rate of endotracheal intubation (ETI) lower in the NIV group • This study had patients with somewhat more severe asthma (based on ABG analysis) • Major limitations with study design

21. NIPPV in Asthma • 3rd study: Gupta, et al. Respiratory Care, May 2010, Vol 55, No 5 • Prospective, randomized controlled trial • 1st study performed in respiratory care unit (as opposed to the emergency department)

22. NIPPV in Asthma (cont) • NIV similar in efficacy to standard therapy in improving respiratory rate, FEV1, ph, PaO2/FiO2, and PaCO2 • NIV was associated with a trend of improved lung function in a larger number of patients, shorter ICU and hospital stays, a trend toward quicker clinical improvement, and less need for inhaled bronchodilators

23. NIPPV in Asthma (Summary) • Theoretically advantageous • Excellent clinical utility in other conditions (COPD, Pulmonary edema) has not been matched in asthma • While a few studies have shown some benefit, larger more controlled studies are required • Easy availability of NIPPV may lead to overuse

24. NIPPV in Asthma (cont) • It appears reasonable to start NIPPV if a patient has no contraindications to it’s use • Be cautious as to not overuse it • If intubation and mechanical ventilation required, do not delay it

25. Who is the greatest post season pitcher of all time?

26. Answer • Mariano Rivera

27. Invasive Ventilatory Management • Fortunately, a minority of patients with asthma require mechanical ventilatory assistance • Frought with potential complications • Patients are frequently anxious and require deep sedation and at times paralysis

28. Invasive Ventilatory Support (cont) • Obstruction in asthma is different from the obstruction in COPD • Bronchospasm, edema, and increased secretions • Obstruction is fixed in asthma, making inspiration as difficult as exhalation

29. Invasive Management (cont) • Major concern: Development of intrinsic PEEP • Increased work of breathing also very worrisome • Once instituted, must pay very close attention to specific ventilator details

30. Invasive Management (Initial Ventilator Settings) • Mode: Volume assist/control • Inspiratory time: 1-1.5 seconds to allow gas to move past obstructions • Flow waveforms: decelerating • Tidal volume: 5-8 cc/kg IBW • Peak flow: Appropriate to allow tidal volume delivery in allotted time

31. Initial Ventilator Settings (cont) • PEEP: 0-5 cm H2O • Plateau pressure: less than 30 cm H2O • Rate: 8-16 breaths/min, producing minimum auto-PEEP • Permissive hypercarbia: unavoidable • FIO2: to maintain PaO2>60 mm Hg

32. Invasive Management • As with ARDS/ALI, asthmatics are at risk of developing ventilator induced lung injury (VILI) because of the pressure required to ventilate • Although high peak pressures are seen, plateau pressures usually remain below 30 cm H2O

33. Invasive Management • It is not uncommon to have peak pressures in excess of 60-70 cm of H2O • Dramatic drop off in peak/plateau characteristic • Hypercarbia common and expected in many instances

34. Question 1 • A 25 year old asthmatic is intubated for severe respiratory distress. He is quite agitated and thrashing about, in spite of heavy sedation and is out of synch with the ventilator. He is on a tidal volume of 8cc/kg and his ABG on 100% FiO2 and PEEP of 5 is: 7.15/75/67/93/26. His plateau pressure is 31 cm H2O. The next best intervention would be to:

35. A: Increase the tidal volume to 10cc/kg • B: Increase the PEEP to 10 cm H2O • C: Start neuromuscular blockade • D: Decrease FiO2 to 80%

36. Answer • C: Start neuromuscular blockade

37. Neuromuscular Blockade in Asthma • British Journal of Hospital Medicine, January 2009, Vol 70, No 1 • These agents help prevent respiratory dysynchrony • Help lower peak pressures • Allow longer expiratory times to reduce dynamic hyperinflation

38. Neuromuscular Blockade (cont) • Many of these patients are young, males, and can be difficult to sedate • Unfortunately, these agents have a variety of adverse, potentially serious side effects • Must weigh the potential risks/benefits of using these agents • If these agents are to be used, they should be stopped as soon as possible

39. Neuromuscular Blockade (cont) • Neuromuscular blocking agents alone can be associated with prolonged muscle weakness • Combination of corticosteroids and aminosteroid neuromuscular blocking agents (such as vecuronium) may be associated with an increased risk of neuromuscular weakness

40. Summary of Neuromuscular Blockade • Asthma represents a group of patients who may particularly benefit from this modality • Use with caution and be prepared to stop as quickly as possible • Be aware of potential complications • Avoid aminosteroid blocking agents

41. Yankee Trivia • How many innings did Mariano Rivera pitch in game seven of the 2003 ALCS against the rival Boston Red Sox?

42. Answer • 3 shut out innings in a dramatic 6-5 Yankee win (Aaron Boone’s walk off home run)

43. How many NBA Championships are here?

44. Answer • 17 • Bill Russell:11 • Michael Jordan:6

45. Ventilatory Management • Intubation and Mechanical Ventilation of the Asthmatic Patient in Acute Respiratory Failure • Brenner B, Cobridge T, and Kazzi A. Proceedings of the American Thoracic Society. Volume 6 pp 371-379, 2009 • Reviewed evidence based data regarding intubation and mechanical ventilation of acute severe asthma in emergency departments

46. Invasive Management • 7 Key areas addressed • Prevention of intubation • Criteria for intubation • Intubation technique • Ventilator settings • Immediate post intubation care • Medical management in the ventilated patient • Prevention and treatment of complications

47. Prevention of Intubation • Best intubation is NO intubation • Mortality 10-20% in patients requiring intubation • Aggressive medical therapy, ?? Early NIPPV

48. Criteria for Intubation • 4 Indications for intubation: • Cardiac arrest • Respiratory arrest or severe bradypnea • Physical exhaustion • Altered sensorium, such as lethargy or agitation • Good clinical judgement always supercedes numbers

49. Intubation Technique • Some advocate awake intubation • Main method used is rapid sequence intubation with ketamine and succinylcholine • Propofol preferred over ketamine in hypertensive patients • Avoid succinylcholine in patients with hyperkalemia

50. Invasive Management (Initial Ventilator Settings) • Mode: Volume assist/control • Inspiratory time: 1-1.5 seconds to allow gas to move past obstructions • Flow waveforms: decelerating • Tidal volume: 5-8 cc/kg IBW • Peak flow: Appropriate to allow tidal volume delivery in allotted time