Post on 22-May-2015
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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
Denver Health
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
Denver Health
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
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
Denver Health
8th Pulmonary Medicine Update February 6, 2008