1. Ventilation of Patients with COPD and Asthma

3. Chronic lung diseases with airflow obstruction
Asthma
Chronic Bronchitis
Emphysema

4. Chronic lung diseases with airflow obstruction
Asthma
Chronic bronchitis
Emphysema

5. Asthma Emphysema Bronchitis

6. COPD CXR

7. Near fatal asthma
Phenotypes
Gradual Onset
Sudden Onset

8. Near fatal asthma

9. Mechanical Venitlation of COPD & Asthma Exacerbations
Objectives
 Pathophysiology
- PaCO2 dederminants - Gas trapping
- Work of breathing - Auto-PEEP
 NIPPV
- IPAP
- EPAP
 Mechanical ventilation
- FIO2 - PEEP
- VT

10. Pathohysiology of Asthma/COPD Exacerbations
Airway
narrowing &
obstruction
Steroids
IPAP MV
­ Frictional
WOB
Airway
Inflammation
Abx?
PEEP
Shortened
muscles,
¯ curvature
Auto-
PEEP
BDs
­ Elastic
WOB
Gas
trapping
MV?
¯ muscle
strength
­ VCO2
 VT
­ VE
IPAP
MV?
PaCO2 pH
PaO2
 VA

11. Determinants of PaCO2 PaCO2  VCO2 VA  VCO2  VA   Work   VE
- Agitation
- Seizures
-  WOB
  Metabolism
- Fever
- CHO
-  T4
 VA
  VE
-  RR
-  VT
-  VD (without  VE)

12. Oxygen Cost of Breathing
Roussos, JCI 1959

13. PV Curve in COPD and Asthma (Stable)
Emphysema 6
Normal/
Asthma
VL (L) VT 4 2 VT
-10
-20
-30
-40
Ptp (cm H2O)
Macklem and Becklake, 1963

14. PV Curve in COPD & Asthma (Acute Exacerbtion)
Emphysema 6
Asthma
VL (L) 4 VT 2 VT
-10
-20
-30
-40
Ptp (cm H2O)

15. Implication VT falls because FRC encroaches on TLC
 Limited ability to  VT with MV/IPAP
Best way to  PaCO2 is to  VCO2
  WOB (frictional and/or elastic)
  PaCO2 even if VT, VE and VA are constant

16. Work of Breathing Total Work Elastic Work Frictional WorkRV
FRC
TLC

17. Effect of VA/Q on PaCO2 (Normal)
PAO2 = 100
PACO2 = 40
PAO2 = 100
PACO2 = 40
DCO2 =
100 ml/min
VCO2 =
100 ml/min
VCO2 =
100 ml/min
DCO2 =
100 ml/min
PvCO2
= 46
PvCO2
= 46
PcCO2
= 40
PcCO2
= 40
PaCO2
= 40

18. Effect of VA/Q on PaCO2 (Low VA/Q, Normal)
PAO2 = 50
PACO2 = 40
PAO2 = 100
PACO2 = 40
50%  VE
50%  VE
DCO2 =
50 ml/min
VCO2 =
50 ml/min
VCO2 =
150 ml/min
DCO2 =
150 ml/min
PvCO2
= 46
PvCO2
= 46
PcCO2
= 40
PcCO2
= 40
HPV
PaCO2
= 40

19. Effect of VA/Q on PaCO2 (Low VA/Q,, AECOPD)
PAO2 = 50
PACO2 = 40
PAO2 = 100
PACO2 = 40
50%  VE
VE at max
DCO2 =
50 ml/min
VCO2 =
50 ml/min
VCO2 =
100 ml/min
DCO2 =
150 ml/min
PvCO2
= 46
PvCO2
= 46
PcCO2
= 40
PcCO2
= 44
HPV
PaCO2
= 42

20. Effect of VA/Q on PaCO2 (Low VA/Q,, AECOPD,  FIO2)
PAO2 = 100
PACO2 = 44
PAO2 = 100
PACO2 = 44
 FIO2
50%  VE
VE constant
DCO2 =
100 ml/min
VCO2 =
50 ml/min
VCO2 =
50 ml/min
DCO2 =
100 ml/min
PvCO2
= 46
PvCO2
= 46
PcCO2
= 44
PcCO2
= 44
HPV
PaCO2
= 44

21. Ventilation in COPD/Asthma
Non Invasive Ventilation
Assessment of mechanics (resistance, auto-PEEP)
Pressure or volume modes?
Role of PEEP
Administering Bronchodilators

22. Ventilation in COPD/Asthma
Non Invasive Ventilation
Assessment of mechanics (resistance, auto-PEEP)
Pressure or volume modes?
Role of PEEP
Administering Bronchodilators

23. Which Patients with COPD benefit from NIV ?

24. NIPPV Pathophysiology of AECOPD & Asthma is amenable to Rx with NIPPV
· EPAP for auto-PEEP
· IPAP for inspiratory Raw
Will  work of breathing
·  VCO2
· At constant VA,  PaCO2 and  pH
May  VA
May  mortality and intubation rate

25. Which Patients with COPD benefit from NIV ? Hospital Mortality
12%
NNT 8 2%

26. NIV in Severe Asthma 17 Episodes of ARF due to asthma
2 patients required intubation for worsening PaC02
Duration of NPPV was 16±21 h.
All patients survived. Length of hospital stay was 5±4 days

27. Ventilation in COPD/Asthma
Non Invasive Ventilation
Assessment of mechanics (resistance, auto-PEEP)
Pressure or volume modes?
Role of PEEP
Administering Bronchodilators

29.  Peak Airway Pressure & Normal Plateau
Resistance
Resistance
Compliance
Time
Time

30. Air-trapping in Asthma/COPD Patients on Mechanical Ventilation
Lung
volume
Tidal ventilation
VEI VT V T
I :E
1:1 Hi
I : E
1: 6 V EE
FRC
Time

31. Assessment of Mechanics
Raw= Peak - Plateau
Auto-PEEP

32. Obstructive Airway Disease
Beware of auto-PEEP!

34. After the third breath, the airway was occluded at end-expiration using the end-expiratory hold function on the ventilator. During the period of zero flow, pressure in the alveoli and ventilator circuit equilibrate, and the plateau pressure reflects auto or intrinsic positive end-expiratory pressure (PEEPi), indicated by the arrow.

35. Giving CPAP to a patient who has auto-PEEP
The increased work of breathing associated with auto-PEEP can be offloaded by applying CPAP to the trachea/mouth, and splinting open the connecting airways.

36. The use of external PEEP in the setting of auto-PEEP may be conceptualized by the "waterfall over a dam" analogy. In this analogy, the presence of dynamic hyperinflation and 10 cmH20 of auto-PEEP is represented in the top panel by the reservoir of water trickling over the dam represented by the solid block. In the middle panel, as long as the external PEEP is less than or equal to the amount of auto-PEEP, the amount of water in the upstream reservoir, representing dynamic hyperinflation, does not increase. However, once the amount of water in the reservoir does increase (bottom panel), dynamic hyperinflation worsens.

39. Excessive Inspiratory Time
Inspiration
Normal
Patient
Increase WOB and “Fighting” of the ventilator
Time (sec)
Flow (L/min) }
Air Trapping
Auto-PEEP
Expiration

40. Ventilation in COPD/Asthma
Non Invasive Ventilation
Assessment of mechanics (resistance, auto-PEEP)
Pressure or volume modes?
Role of PEEP
Administering Bronchodilators

41. Pressure or Volume Mode?
Predictable TV
Peak-Plat gradient
Monitor Plat
Better acidosis control
Pressure
Minimise over-distension
Monitor Tidal volume
Excess volumes as airway resistance improves

42. Mechanical Ventilation of COPD & Asthma Exacerbations
Mode:
 AC vs IMV  PS
 ? rest respiratory muscles: CMV
 Better sleep with AC vs. IMV-PS
 Ventilator-induced diaphragm changes (?)
Triggering: key issue with either mode
 PEEP to counter auto-PEEP
 Major cause of patient-ventilator
dissynchrony

43. Initial Ventilator Settings
Inspiratory time 0.8 – 1.2 secs
RR 10-12
TV 6-8 ml/Kg
Pplat < 30 cm H2O
PEEP ??

44. Assessment of Hyperinflation
CVS effects  disconnect
Pplat
PEEPi measurement

45. Reducing Hyperinflation
I : E
1: 2
Reduce rate
Reduce tidal volume
Increase expiratory time
Increase inspiratory flow rate
Increased Peak Airway Pressure
Monitor (Pplat)
Tolerate increased CO2
(minimise dead space)
I : E
1: 6

46. COPD flow and frequency
As flow increased from 30 to 60 and 90 L/min (from right to left), frequency increased from (18 to 23 and 26 breaths/min, respectively), Auto-PEEP decreased (from 15.6 to 14.4 and 13.3 cm H2O, respectively) and end-expiratory chest volume also fell. Increases in flow from 30 L/min to 60 and 90 L/min also led to decreases in the swings in Pes from 21.5 to 19.5 and 16.8 cm H2O.

47. Hypercapnia: How permissive?
Defence of intracellular pH
Apnoeic oxygenation in dogs to pH 6.5 and PaCO2 of 55kPa
Anaesthetic mishap with PaCO2 of > 300 mmHg (40 kPa) and pH of 6.6 survived without sequelae
Am J Respir Crit Care Med 1994; 150:

48. Ventilation in COPD/Asthma
Non Invasive Ventilation
Assessment of mechanics (resistance, auto-PEEP)
Pressure or volume modes?
Role of PEEP
Administering Bronchodilators

49. External & Internal PEEP
Waterfall Concept
Pao
Pao 10 10
EPP
EPP 10
+10 10
Palv
Palv 10 10 10
Pel
Ppl
Ppl

50. Effect of Auto-PEEP Normal airway resistance (end-exhalation)
Ptp = 5
- 5
PA = 0
Patm = 0
Ppl =
- 5
Pel = 5
- 5
D Ppl needed to initiate inhalation: - 1
PA drops to - 1 relative to Patm

51. Effect of Auto-PEEP Airway narrowing causing auto-PEEP
Ptp = 8 2
PA = 10
Ppl = 2
Patm = 0 2
Pel = 8
D Ppl needed to initiate inhalation: - 11

52. Treatment of Auto-PEEP with PEEP or CPAP
Airway narrowing with auto-PEEP: Treatment
with PEEP
Ptp = 8 2
PA = 10
Ppl 2
PEEP = 10 2
Pel = 8
D Ppl needed to initiate inhalation: - 1
The only thing PEEP does is ¯ work of breathing

53. Implication PEEP, EPAP, CPAP  No effect on VE, VT or VA
  WOB (elastic)
-  VCO2 (on next breath)
-  PaCO2 (on next breath)

54. Treatment of Auto-PEEP with  Vinsp
Longer time for exhalation, PA falls
Ptp = 5 1
PA = 6
Patm = 0
Ppl = 1 1
Pel = 6
D Ppl needed to initiate inhalation: - 7

55. External PEEP Reduce inspiratory muscle load
Improve ventilator triggering
80% of PEEPi can be matched without increase PEEP tot
Reduce hyperinflation by improving expiration

56. Titrating PEEP to PEEPi

57. Heliox and Obstructive Airway Disease
Low density high thermal conductivity
Reduce pressure gradient in turbulent flow
Administered in
NIV
IPPV
Nebulisers
Role in Asthma and COPD?

59. Ventilation in COPD/Asthma
Non Invasive Ventilation
Assessment of mechanics (resistance, auto-PEEP)
Pressure or volume modes?
Role of PEEP
Administering Bronchodilators

60. Theophylline
Used for OVER 50 years
Lack of benefit has been shown when aggressive inhalation B2-agonist + systemic corticosteroids

61. Administration of Bronchodilators

62. Administration of Bronchodilators
Nebuliser or MDI?
Lung deposition of radiolabelled drug*
MDI 5.6% v Nebuliser 1.2%
Urinary excretion**
MDI with spacer 38%
MDI in line 9%
Nebuliser 16%
4-10 puffs MDI effective in reducing RAW
* Chest 1999; 115:
**Am Rev Respir Dis 1990; 141:440–444

63. MDI adapters for use with MV circuits

65. Myopathy in Asthma Steroid myopathy Muscle relaxants
Polyneuropathy of the critically ill

66. Polyneuropathy of the critically ill
Myopathy in Asthma
Proximal muscle
Subacute (3 weeks)
Normal CPK
Steroid myopathy
Distal & proximal
High myoglobin
High CPK
Muscle relaxants
Sensorimotor
Polyneuropathy of the critically ill

67. Principles of managing the ventilated patient with obstructive lung disease
Provide adequate support for muscle rest with adequate pH and PO2
Do not over ventilate
Minimize minute volume requirements
Minimize the risk of barotrauma
Maintain adequate bronchial hygiene
Maintain appropriate nutrition