1. Diagnosis and Management of Acute Respiratory Failure
Steven B. Leven, M.D., F.C.C.P.
Clinical Professor, Pulmonary/Critical Care Medicine UCI
Director MICU and Respiratory Therapy, UCI Medical Center

2. Objectives Understand the causes of hypoxia and hypercapnea
Know the clinical manifestations of respiratory failure
Be familiar with various oxygen delivery systems
Know indications and contraindications to noninvasive positive pressure ventilation
Know indications for endotracheal intubation
Be familiar with basic modes of mechanical ventilation

3. CASE # 1
J.T. is a 68-kg, 42-yr old female admitted after a drug overdose complicated by emesis and aspiration. Intubation and mechanical ventilation are initiated in the emergency department.

4. CASE # 1
Mechanical ventilation
AC (volume) mode
Tidal volume 750 mL
16 breaths/min
FIO2 1.0
PEEP 5 cm H2O

5. CASE # 1 Peak airway pressure 52 cm H2O
Inspiratory plateau pressure (IPP) 48 cm H2O
pH 7.38, PaCO2 36 PaO2 57
Sinus tach at 166, BP 75/50, no urine output
Patient very “agitated” and “fighting vent”
What would you do?

6. CASE #2
L.W. is a 62-yr-old, 52-kg female with severe emphysema. For 2 days she has had progressive dyspnea and was found unresponsive. ABG on 5liters NC pH 7.07 pCO2 87 pO2 62.
She required intubation and initiation of mechanical ventilation.

7. CASE #2 ICU ventilator settings AC, rate 12 breaths/min
Tidal volume 500 mL
FIO2 100%
PEEP 5 cm H2O

8. CASE #2 RR 24 I:E ratio = 1:1.5 Peak pressure 50 cm H2O, IPP 35 cm H2O
End expiratory pressure is 20 cm
pH 7.20, PaCO2 60, PaO2 215
Sinus tach 157
BP 78/45
No urine output
Patient very agitated
What would you do?

9. CASE #3
37 year old healthy malpractice plaintiff attorney presents to ER with 24 hour history of generalized weakness. Last week he had a mild bout of gastroenteritis after eating under cooked chicken. He could walk with difficulty when he arrived at ER 8 hours ago. Now he needs help to reposition himself in bed and he coughs when he attempts to drink.

10. CASE #3 Exam normal except weakness Chemistries and CBC normal
RA ABG pH 7.41 pCO2 41 pO2 84
Vital Capacity 840cc (12cc/Kg)
CXR at left

11. CASE #3 Where should this patient be cared for? ICU? Tele? Ward? Home?
Should this patient be fed?
Should he be advised to call a lawyer?
Would you put him on BiPAP?
Anything else you would do?

12. Case # 4
A 25-year-old lady, Miss. Poor Compliance, is rushed into your Emergency Department. She is an asthmatic who on arrival is sitting forward in the tripod position, using her accessory muscles to breath. She is tachypneic, diaphoretic, agitated and unable to talk. During a nebulizer tx with albuterol she becomes dusky and poorly responsive.

13. Case # 4

14. Plan of care? Get ABG? Start BiPAP?
Discuss patient’s “feelings” about being ill?
Get advice from resident (oops, he is running a code)
Other?

15. Acute Respiratory Failure
Hypoxemic
Room air PaO2  50 torr
Hypercapnic
PaCO2  50 torr
Acute vs chronic
Often Multifactorial
ARF 15

16. Pathophysiology of Hypoxemia
Ventilation/perfusion mismatch
Shunt effect (intracardiac or intrapulmonary)
Decreased diffusion of O2
Alveolar hypoventilation
FIO2 < 21% (eg. High altitude)
ARF 16

17. Pathophysiology of Hypercapnia
Alveolar ventilation is the prime determinant of CO2 exchange during mechanical ventilation
VA ~ 1/pCO2
VA=(VT-VD)f
Change in any variable affects pCO2

18. Causes of Hypercapnia Inability to sense elevated PaCO2
Inability to signal respiratory muscles
Inability to effect a response from respiratory muscles
Increased dead space

19. Inability to effect adequate response from respiratory muscles
Imbalance between demand for respiratory muscle work and the ability to supply that work
Examples of increased demand: bronchospasm, fever, low lung compliance, pleural effusion
Decreased supply: poor cardiac output, malnutrition, deconditioning

20. Increased Dead Space (wasted ventilation)
Hypovolemia
Low cardiac output
Pulmonary embolus
High airway pressures
Short-term compensation by increasing tidal volume and/or respiratory rate

21. Manifestations of Respiratory Distress
Altered mental status – especially anxiety!!!
Anxiety is a result of respiratory distress, almost NEVER the cause.
Increased work of breathing
Tachypnea, nasal flaring
Accessory muscle use, retractions, paradoxical breathing pattern, respiratory alternans
Catecholamine release
Tachycardia, diaphoresis, hypertension
Abnormal ABG – not always!!!
Neuromuscular failure is different from above – monitor vital capacity – intubate near 15cc/kg

22. Oxygen Supplementation low flow systems 1-10 LPM
100% O2 mixes with room air to determine FIO2 - definition
FIO2 varies with patient’s breathing pattern
Rapid inspiration entrains more room air
Deep breaths entrain more room air
Rapid respiratory rate entrains more room air
Patients in more distress get lower FIO2
FIO2 is unknown since amount of entrainment is unknown
Any humidity in gas comes from entrained air- wall O2 has 0% relative humidity
Low flow devices
Simple Nasal Cannulas
Simple masks

23. High Flow O2 Devices > 20 - 60 lpm
Device provides 100% of gas to patient - definition
No entrainment of room air if mask fits
FIO2 is known and exact
Relative humidity depends on the device
High flow devices:
High flow nasal cannula
Venturi mask
Aerosol mask – heated or cool
Nonrebreather mask – some characteristics of both high and low

24. O2 Devices

25. Aerosol O2 devices

26. BiPAP or NPPV Contraindications Cardiac or respiratory arrest
Inability to cooperate, protect the airway, or clear secretions
Nonrespiratory organ failure, esp shock
Facial surgery, trauma, or deformity
Prolonged duration of mechanical ventilation anticipated
Recent esophageal anastomosis
A need for emergent intubation is an absolute contraindication to NPPV
Set inspiratory pressure (IP) and exp pressure (PEEP)
Mean pressure determines oxygenation
IP – PEEP determines ventilatory assist

27. Endotracheal Intubation
“….An opening must be attempted in the trunk of the trachea, into which a tube or cane should be put; You will then blow into this so that lung may rise again….And the heart becomes strong….”
-Andreas Vesalius (1555)

28. Indications for Endotracheal Intubation
Airway protection (outside ICU?)
Relief of airway obstruction
Respiratory failure or impending respiratory failure
Hypoxic or
Hypercapneic or both
Need for hyperventilation - ICP
Unsustainable work of breathing
Facilitate suctioning/pulmonary toilet
Shock !!!!!!!!!!!

29. Decision to intubate Clinical decision-not based on ABG
Error on the side of patient safety
What is the safest way to navigate illness?
Intubation is not an act of weakness
Think ahead- if need to intubation is expected in next 24hr, intubate now
Endotracheal tubes are not a disease and ventilators are not an addiction i.e. Intubation does not cause ventilator dependence

30. Modes of Mechanical Ventilation Point of Reference: Spontaneous Ventilation

31. Continuous Positive Airway Pressure (CPAP)
No machine breaths delivered
Allows spontaneous breathing at elevated baseline pressure
Patient controls rate and tidal volume

32. Assist-Control Ventilation
You set tidal volume and minimum rate
Additional breaths delivered with minimal inspiratory effort - pt sets actual rate
Advantages: reduced work of breathing; allows patient to modify minute ventilation
Most patients should start with this mode
Rate 12, TV 8-10 cc/kg, FiO2 100% PEEP 5

33. Synchronized Intermittent Mandatory Ventilation (SIMV)
Volume cycled breaths at a preset rate
Additional spontaneous breaths at tidal volume and rate determined by patient
Invented as weaning mode
Best weaning mode is sink or swim
Best use is to mitigate AutoPEEP

34. Pressure-Support Ventilation
Pressure assist during spontaneous inspiration with flow-cycled breath
Pressure assist at constant pressure continues until inspiratory effort decreases
Delivered tidal volume dependent on set pressure, inspiratory effort and resistance/compliance of lung/thorax

35. Inspiratory Plateau Pressure
Airway pressure measured at end of inspiration with no gas flow present
Estimates alveolar pressure at end-inspiration
IPP is best indicator of alveolar distension
PIP – IPP ~ airway resistance
Peak pressure
Plateau pressure
Inspiration Expiration

36. Inspiratory Plateau Pressure
High inspiratory plateau pressure – stiff lungs
Barotrauma - no
Volutrauma – yes – pneumothorax, etc
Decreased cardiac output
Methods to decrease IPP
Decrease tidal volume
??? Decrease PEEP
Goal IPP usually  30 cm H2O
ARDS protocol: tidal volume 6 cc/kg IBW

37. Auto-PEEP - common Occurs in setting of severe COPD or asthma
Very uncomfortable for patient - agitation
Can be measured on most ventilators
Increases peak, plateau, and mean airway pressures
Hypotension – impaired venous return
Suspect in setting of COPD or asthma pt who is agitated or hypotensive – this is common!!!

38. I:E Ratio during Mechanical Ventilation
If expiratory time too short for full exhalation
Breath stacking
Auto-PEEP
Reduce auto-PEEP by reducing inspiratory time/increasing expiratory time
Increase peak inspiratory flow rate – 100 lpm
Decrease respiratory rate (use IMV without PSV) – rate of 12 usually is good
Decrease tidal volume to 8 cc per kg IBW

39. CASE # 1
J.T. is a 68-kg, 42-yr old female admitted after a drug overdose complicated by emesis and aspiration. Intubation and mechanical ventilation are initiated in the emergency department.

40. CASE # 1 AC (volume) mode Tidal volume 700 mL 10 breaths/min
Mechanical ventilation
AC (volume) mode
Tidal volume 700 mL
10 breaths/min
FIO2 1.0 – always start at 100%
PEEP 5 cm H2O

41. CASE # 1 Peak airway pressure 52 cm H2O
Inspiratory plateau pressure (IPP) 48 cm H2O
pH 7.38, PaCO2 36 torr PaO2 57 torr
Sinus tach at 166, BP 75/50
Patient very “agitated” and “fighting vent”
What are the issues here?

42. CASE # 1 FIO2 100%? TV 10cc/Kg? High inspiratory plateau pressure?
What is diagnosis?
What are the consequences of
FIO2 100%?
TV 10cc/Kg?
High inspiratory plateau pressure?
Hypotension and tachycardia?
agitation and fighting vent
What variables should be changed to improve PaO2? BP? Protect lungs?

43. ARDS Decreased lung compliance results in high airway pressures
Tidal volume goal 6cc/Kg
Maintain IPP  30 cm H2O
PEEP to improve oxygenation
Aim for FIO2 50% - O2 toxic at > 50%
Patients often need volume loading
Sedation usually needed and sometimes also paralytic

44. CASE #2
L.W. is a 62-yr-old, 52-kg female with severe emphysema. For 2 days she has had progressive dyspnea and was found unresponsive. ABG on liters NC pH 7.07 pCO2 87 pO2 42.
She required intubation and initiation of mechanical ventilation.

45. CASE #2 ICU ventilator settings AC, rate 12 breaths/min FIO2 1.0
Tidal volume 600 mL
Peak flow 50 l/sec
PEEP 5 cm H2O

46. CASE #2 RR 24 I:E ratio = 1:1.5 Peak pressure 50 cm H2O, IPP 35 cm H2O
End Expiratory Alveolar Pressure 20 cm H2O
pH 7.28, PaCO2 60 torr, PaO2 215 torr
Sinus tach 157
BP 78/45
No urine output
Patient very agitated

47. CASE #2 change in peak flow rate ? change in respiratory rate ?
What complication of therapy is at work?
What variable(s) should be changed to improve the ABG ? BP? UO? Agitation?
change in peak flow rate ?
change in respiratory rate ?
change in ventilator mode?
bronchodilators ?

48. Analysis - Patient L.W. Hypercapnia acceptable if pH OK
High peak airway pressure can be OK
Wide peak-plateau pressure difference indicates obstructive disease
Be alert for auto-PEEP
Hypotension and tachycardia suggest auto-PEEP and or inadequate preload

49. Obstructive Airway Disease
Obstructive diseases require adequate expiratory time
PaCO2 should be kept at patient’s baseline level

50. CASE #3
37 year old healthy lawyer admitted from ER with 24 hour history of generalized weakness. Last week he had a mild bout of gastroenteritis. He could walk with difficulty when he arrived at ER 12 hours ago. Now he needs help to reposition himself in bed and he coughs when he attempts to drink.

51. CASE #3 Exam normal except weakness Chemistries and CBC normal
RA ABG pH 7.41 pCO2 41 pO2 84
Vital Capacity 840cc (12cc/Kg)

52. CASE #3 What is this patient’s diagnosis?
Is this patient in respiratory failure?
What is this patient’s most urgent need?

53. CASE #3 Neuromuscular Respiratory Failure
Patients do not appear to struggle
ABG does not tell you when to intubate
Delay may result in aspiration and arrest
Follow vital capacity closely in ICU
Intubate when VC approaches 15cc/Kg

54. Case # 4
A 25-year-old lady, Miss. Poor Compliance, is rushed into your Emergency Department. She is an asthmatic who on arrival is sitting forward in the tripod position, using her accessory muscles to breath. She is tachypneic, diaphoretic, agitated and unable to talk. During a nebulizer tx with albuterol she becomes dusky and poorly responsive.

55. Case # 4

56. Plan of care? Get ABG? Start BiPAP?
Discuss patient’s “feelings” about being ill?
Check her health insurance
Get advice from resident (oops, he is running a code)
Other?