Denver Health

Mechanical Ventilation of Patients with

COPD and AsthmaRichard K. Albert, M.D.Chief of Medicine

Denver HealthProfessor of MedicineUniversity of Colorado

Adjunct Professor of Engineeringand Computer ScienceUniversity of Denver

8th Pulmonary Medicine UpdateFebruary 7, 2008

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Colorado Aspen Trees

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Colorado Aspen Trees

Mechanical Venitlation ofCOPD & Asthma ExacerbationsDenver Health

Objectives Pathophysiology

- PaCO2 dederminants - Gas trapping

- Work of breathing - Auto-PEEP

NIPPV- IPAP- EPAP

Mechanical ventilation- FIO2 - PEEP

- VT

Pathohysiology ofAsthma/COPD Exacerbations

AirwayInflammation

Airwaynarrowing &obstruction

Shortenedmuscles, curvatur

e

FrictionalWOB

musclestrength

VT

PaCO2

pH PaO2

Gastrapping

Auto-PEEP

VCO2VE

ElasticWOB

VA

PEEP

IPAPMV?

Steroids

Abx?

MV?

IPAP

MV

BDs

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Determinants of PaCO2

PaCO2 VCO2

VA

VCO2

Work- Agitation- Seizures- WOB

Metabolism- Fever- CHO- T4

VA

VE

- RR- VT

- VD (without VE)

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Oxygen Cost of Breathing

Roussos, JCI 1959

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PV Curve in COPD and Asthma

(Stable)

Macklem and Becklake, 1963

-10 -20 -30 -40

2

4

6

Ptp (cm H2O)

VL (L)

VT

VT

Normal/Asthma

Emphysema

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COPD CXR

PV Curve in COPD & Asthma

(Acute Exacerbtion)

-10 -20 -30 -40

2

4

6

Ptp (cm H2O)

VL (L)

VT

VT

Asthma

Emphysema

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ImplicationDenver Health

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

Gas Trapping PInspmaxLu

ng

Volu

me

TLC

RV

PInspmax

-100 0

Respiratory muscle weakness

(Not fatigue!)

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Effect of Auto-PEEP

Patm = 0PA = 0

Ppl =- 5

Normal airway resistance (end-exhalation)

Pel = 5

Ppl needed to initiate inhalation: - 1PA drops to - 1 relative to Patm

- 5

- 5

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Ptp = 5

Effect of Auto-PEEP

PA = 10

Airway narrowing causing auto-PEEP

Patm = 0Ppl = 2

Pel = 8

Ppl needed to initiate inhalation: - 11

2

2

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Ptp = 8

Treatment of Auto-PEEP with PEEP or CPAP

Airway narrowing with auto-PEEP: Treatmentwith PEEP

PA = 10PEEP = 10Ppl 2

Pel = 8

Ppl needed to initiate inhalation: - 1The only thing PEEP does is work of breathing

2

2

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Ptp = 8

ImplicationDenver Health

PEEP, EPAP, CPAP No effect on VE, VT or VA

WOB (elastic)

- VCO2 (on next breath)

- PaCO2 (on next breath)

Treatment of Auto-PEEP with Vinsp

Longer time for exhalation, PA falls

PA = 6Ppl = 1

Pel = 6

Ppl needed to initiate inhalation: - 7

1

1

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Ptp = 5

Patm = 0

Work of BreathingW

ork

of

Bre

ath

ing

RV FRC TLC

Total Work

Elastic Work

Frictional Work

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EPAP or CPAP vs IPAP

Appendini, AJRCCM 1994 Ptp, Ptd in 7 COPD pts within 48 hrs Work of breathing measured during:

- Spontaneous breathing- CPAP = 0.8 - 0.9 auto-PEEP- PS = 10 cm H2O

- PS + CPAP Both CPAP and PS WOB

¯ Additive ? effect of underestimating auto-PEEP

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NIPPV

Pathophysiology of AECOPD & Asthma is amenable to Rx with NIPPV

EPAP for auto-PEEP IPAP for inspiratory RawWill work of breathing

VCO2

At constant VA, PaCO2 and pH

May VA

May mortality and intubation rate

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Frequency of Intubation in Controls in Studies of

NIPPVStudy N %Kramer, 1995 15 73

Wysocki,1995 20 70

Brochard. 1995 42 74

Burk, 1973 ? 29-54

Albert, 1980 44 2

Bone, 1984 50 26

Niewoehner, 1999 271 3

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Mortality in Controls in Studies of NIPPV

Study N %Bott, 1993 30 30Kramer, 1995 15 13Wysocki,1995 20 50Brochard. 1995 42 29Sukumalchantra, 1966 43 18Campbell, 1967 198 6Albert, 1980 44 0Stauffer, 1993* 67 19Niewoehner, 1999 271 3

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Mechanical Ventilation ofCOPD & 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

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Mechanical Ventilation ofCOPD & Asthma Exacerbations

Tidal Volume (with AC) Recommendations: 8-12 ml/kg For 60 kg man = 480 to 720 ml Frequently > FEV1 ! Use smaller VT (encroaching on TLC)

Minimize effect of auto-PEEP High inspiratory flow (ignore peak Paw) PEEP

Adjust ventilator to patient, not vice-versa

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V/Q in Emphysema (H-Pattern):

Normal and High V/Q

0 0.001 0.01 1 10 1000

0.1

0.2

0.3

0.4

0.5

V/Q Ratio

Venti

lati

on

(

) Perf

usi

on

(

)

Wagner, JCI 1977

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V/Q in Emphysema (L-Pattern): Normal and Low

V/Q

0 0.001 0.01 1 10 1000

0.1

0.2

0.3

0.4

0.5

V/Q Ratio

Venti

lati

on

(

) Perf

usi

on

(

)

Wagner, JCI 1977

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Effect of VA/Q on PaCO2

(Normal)

VCO2 =100 ml/min

PcCO2

= 40

PaCO2

= 40

PcCO2

= 40

PvCO2

= 46PvCO2

= 46

DCO2 = 100 ml/min

DCO2 = 100 ml/min

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PAO2 = 100PACO2 = 40

PAO2 = 100PACO2 = 40

VCO2 =100 ml/min

Effect of VA/Q on PaCO2

(Low VA/Q, Normal)

PcCO2

= 40

PaCO2

= 40

PcCO2

= 40

PvCO2

= 46

DCO2 = 50 ml/min

DCO2 = 150 ml/min

HPV

50% VE

VCO2 = 50 ml/min

50% VE

VCO2 = 150 ml/min

PvCO2

= 46

PAO2 = 50PACO2 = 40

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PAO2 = 100PACO2 = 40

Effect of VA/Q on PaCO2

(Low VA/Q,, AECOPD)

PcCO2

= 44

PaCO2

= 42

PcCO2

= 40

PvCO2

= 46PvCO2

= 46

DCO2 = 50 ml/min

HPV

VE at max50% VE

VCO2 = 50 ml/min

VCO2 = 100 ml/min

DCO2 = 150 ml/min

PAO2 = 50PACO2 = 40

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PAO2 = 100PACO2 = 40

Effect of VA/Q on PaCO2

(Low VA/Q,, AECOPD, FIO2)

PcCO2

= 44

PaCO2

= 44

PcCO2

= 44

PvCO2

= 46PvCO2

= 46

DCO2 = 100 ml/min

HPV

VE constant50% VE

VCO2 = 50 ml/min

VCO2 = 50 ml/min

DCO2 = 100 ml/min

FIO2PAO2 = 100PACO2 = 44

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PAO2 = 100PACO2 = 44

Acute Exacerbations of COPDDenver Health

What do I do? NIPPV with EPAP

- Auto-PEEP- Work of breathing- VCO2

Mechanical ventilation - PEEP to facilitate triggering- Low VT

- Lowest safe FIO2

Acute Exacerbations of COPDDenver Health

Summary Pathophysiology

- VCO2 - Gas trapping

- Work of breathing - Auto-PEEP

NIPPV- IPAP- EPAP

Mechanical ventilation- FIO2 - PEEP

- VT

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8th Pulmonary Medicine Update February 6, 2008