Mechanical ventilation in air flow obstruction

ونفخت “ “ سويته ونفخت فإذا سويته فإذافقعوا روحي من فقعوا فيه روحي من فيه

ساجدين ساجدين له ““له۷۲۷۲ص ص

Mechanical Mechanical Ventilation in Ventilation in Severe Airflow Severe Airflow

ObstructionObstructionNabil Abouchala, MDNabil Abouchala, MD

ConsultantConsultant

Pulmonary & Critical Care MedicinePulmonary & Critical Care Medicine

[email protected]@yahoo.com

Chronic lung diseases Chronic lung diseases with airflow with airflow obstructionobstruction

Chronic lung diseases Chronic lung diseases with airflow with airflow obstructionobstruction

Asthma Emphysema Bronchitis

Potentially fatal Potentially fatal asthmaasthma

5000 deaths/yr in US5000 deaths/yr in US

Two variants:Two variants:– progressive worsening 1-3 daysprogressive worsening 1-3 days– ““sudden death”sudden death”

Risk factorsRisk factors– History of near fatal asthma/intubationsHistory of near fatal asthma/intubations– Frequent hospitals/EDs (> 2/year)Frequent hospitals/EDs (> 2/year)– Co-morbidities (CV, COPD. Psych, drug abuse)Co-morbidities (CV, COPD. Psych, drug abuse)– Frequent meds (>2 puffers/month)Frequent meds (>2 puffers/month)– Poor socioeconomic statusPoor socioeconomic status

Ventilation in Ventilation in COPD/AsthmaCOPD/Asthma


Which Patients with Which Patients with COPD benefit from NIV ?COPD benefit from NIV ?

Which Patients with COPD Which Patients with COPD benefit from NIV ?benefit from NIV ?Hospital MortalityHospital Mortality

12%

2%

NNT 8


12%

2%

NNT 8


NNT 8

Target Treatment for Target Treatment for Maximum Benefit of NIV in Maximum Benefit of NIV in COPD ExacerbationsCOPD Exacerbations

Likely to improve

Severity Likely toFail NIV

Target group for NIV

Potential Benefit

Less severe

Higher pH

> 7.30

Very severe COPD exacerbation

Severe hypercapnia

(PCO2 > 90)

Severe acidemia

pH < 7.10


Case presentationA 68-year-old man with COPD is brought to the

emergency room in severe respiratory distress. The man weighs 65 kg (143 lb). Arterial blood gases document severe respiratory acidosis (PaCO2 is 104 mm Hg; pH is 7.10). After providing tracheal intubation and sedation, you order positive pressure ventilation in the assist control (AC) mode.

The most appropriate ventilatory setting at this point:

RR TV Peak inspiratory(mL) flow rate (L/min)

_A. 28 600 40B. 16 1000 60C. 24 1000 80D. 10 500 80E. 30 400 40

Tidal ventilation

Lung volume

VT

FRC

VT

VEE

Time

VEI

I :E1:1

I : E1: 6

Air-trapping in Asthma/COPD Air-trapping in Asthma/COPD Patients on Mechanical Patients on Mechanical VentilationVentilation

Obstructive Airway Obstructive Airway DiseaseDisease

Beware of auto-PEEP!Beware of auto-PEEP!

Detrimental effects of autoPEEPDetrimental effects of autoPEEPTrigger with acute

exacerbation

Tachypnea (decreased I:E ratio)

Increased airway resistance

Increased work of breathing

Increased work of breathing

HyperinflationHyperinflation

autoPEEPautoPEEP

Decreased effectiveness of

inspiratory musclesIncreased oxygen cost of

breathingIncreased oxygen cost of

breathing

Respiratory muscle fatigueRespiratory

muscle fatigue

Excessive Inspiratory Excessive Inspiratory TimeTimeExcessive Inspiratory Excessive Inspiratory TimeTime

Inspiration

Expiration

NormalNormalPatientPatient

Time (sec)

Flo

w (

L/m

in)

Air TrappingAuto-PEEP

}

Increase WOB and “Fighting” of the ventilator

Case presentationA 35-yr-old male is admitted with severe bronchial asthma

requiring ventilatory support. He is fully sedated and paralyzed, on assist-control mechanical ventilation with a set rate of 15 breaths/min; tidal volume of 1000 mL, and an inspiratory flow rate of 60 L/min, which gives an inspiratory-expiratory (I:E) ratio of 1:3. He is not on any PEEP, and an end-expiratory hold maneuver reveals an auto PEEP of 15 cm H2O.

Which one of the following options is most effective in minimizing the auto-PEEP?

A. Decreasing the RR 12 /min, giving an I:E ratio of 1:4

B. Increasing the flow to 120 L/min, giving an I:E ratio of 1:7

C. Decreasing the tidal volume to 900 mL

D. Adding an external PEEP of 5 cm H2O

Auto-PEEPAuto-PEEP

15 2 0

AA

15 15 15

BB

Measurement of auto-PEEP by expiratory occlusion


Pressure or Volume Pressure or Volume Mode?Mode?

VolumeVolume Predictable TVPredictable TV Peak-Plat gradientPeak-Plat gradient Monitor PlatMonitor Plat Better acidosis Better acidosis

controlcontrol

PressurePressure Minimise over-Minimise over-

distensiondistension Monitor Tidal Monitor Tidal

volumevolume Excess volumes as Excess volumes as

airway resistance airway resistance improvesimproves

Initial Ventilator Initial Ventilator SettingsSettings Inspiratory time 0.8 – 1.2 secsInspiratory time 0.8 – 1.2 secs RR 10-12RR 10-12 TV 6-8 ml/KgTV 6-8 ml/Kg Pplat < 30 cm H2OPplat < 30 cm H2O PEEP ??PEEP ??

Assessment of Assessment of HyperinflationHyperinflation

Assessment of Assessment of HyperinflationHyperinflation

Reducing Reducing HyperinflationHyperinflation

Reduce rateReduce rate Reduce tidal volumeReduce tidal volume Increase expiratory timeIncrease expiratory time

– Increase inspiratory flow rateIncrease inspiratory flow rate– Increased Peak Airway PressureIncreased Peak Airway Pressure

Monitor (Pplat)Monitor (Pplat) Tolerate increased CO2Tolerate increased CO2

(minimise dead space)(minimise dead space)

I : E1: 6

I : E1: 2

Hypotension after Hypotension after initiation of Mechanical initiation of Mechanical VentilationVentilation

Conversion to positive Conversion to positive intrathoracic pressureintrathoracic pressure– Decreased venous return, Decreased venous return,

cardiac outputcardiac output– Exacerbated by hypovolemiaExacerbated by hypovolemia

Auto-PEEP increases Auto-PEEP increases intrathoracic pressureintrathoracic pressure


PplPpl

EPPEPP

Pel

PalvPalv

PaoPao

1010

10

+10

1010

10

00

Waterfall ConceptExternal & Internal PEEP

10

External PEEPExternal PEEP

Offload effects of PEEPiOffload effects of PEEPi– Waterfall theory PEEPi not additive until above Waterfall theory PEEPi not additive until above

critical closing pressure of airwaycritical closing pressure of airway Reduce inspiratory muscle loadReduce inspiratory muscle load Improve ventilator triggeringImprove ventilator triggering Excess level will increase hyperinflationExcess level will increase hyperinflation 80% of PEEPi can be matched without 80% of PEEPi can be matched without

increase PEEP totincrease PEEP tot ?? reduce hyperinflation by improving ?? reduce hyperinflation by improving

expirationexpiration

Titrating PEEP to PEEPiTitrating PEEP to PEEPi

until no missed trigger effortsuntil no missed trigger efforts Minimise inspiratory effortMinimise inspiratory effort

– ClinicallyClinically– Oesophageal pressure/CVPOesophageal pressure/CVP

Until increase in hyperinflationUntil increase in hyperinflation– Pplat on volume modesPplat on volume modes– Until TV reduces on Pressure controlUntil TV reduces on Pressure control

Titrating PEEP to PEEPiTitrating PEEP to PEEPi


TheophyllineTheophylline

Administration of Administration of BronchodilatorsBronchodilators

Nebuliser or MDI?Nebuliser or MDI? Lung deposition of radiolabelled drug*Lung deposition of radiolabelled drug*

– MDI 5.6% v Nebuliser 1.2%MDI 5.6% v Nebuliser 1.2% Urinary excretion**Urinary excretion**

– MDI with spacer 38%MDI with spacer 38%– MDI in line 9%MDI in line 9%– Nebuliser 16%Nebuliser 16%

4-10 puffs MDI effective in reducing R4-10 puffs MDI effective in reducing RAWAW

Administration of Administration of BronchodilatorsBronchodilators

Nebuliser or MDI?Nebuliser or MDI? Lung deposition of radiolabelled drug*Lung deposition of radiolabelled drug*

– MDI 5.6%MDI 5.6% v Nebuliser 1.2% v Nebuliser 1.2% Urinary excretion**Urinary excretion**

– MDI with spacer 38%MDI with spacer 38%

– MDI in line 9%MDI in line 9%– Nebuliser 16%Nebuliser 16%

4-10 puffs4-10 puffs MDI effective in reducing R MDI effective in reducing RAWAW

* Chest 1999; 115:1653-1657* Chest 1999; 115:1653-1657**Am Rev Respir Dis 1990; 141:440–444**Am Rev Respir Dis 1990; 141:440–444

Outcome of Ventilation & Outcome of Ventilation & COPDCOPD

166 patients requiring MV166 patients requiring MV Median duration 4.1 daysMedian duration 4.1 days 9% required > 21 days ventilation9% required > 21 days ventilation Hospital mortality 28%Hospital mortality 28% 9% discharged with 9% discharged with

tracheostomy tracheostomy MV MV 60% of MV time spent weaning60% of MV time spent weaning

Nevins & Epstein Chest 2001;119:1840Nevins & Epstein Chest 2001;119:1840

Weaning and COPDWeaning and COPD

Weaning protocolsWeaning protocols Non Invasive ventilationNon Invasive ventilation External PEEP to offload PEEPiExternal PEEP to offload PEEPi Optimise cardiac functionOptimise cardiac function

– DiureticsDiuretics– ACE inhibitorsACE inhibitors

AcetazolamideAcetazolamide

Myopathy in AsthmaMyopathy in Asthma

Steroid myopathySteroid myopathy Muscle relaxantsMuscle relaxants Polyneuropathy of the critically illPolyneuropathy of the critically ill

Myopathy in AsthmaMyopathy in Asthma

Principles of managing the Principles of managing the ventilated patient with ventilated patient with obstructive lung diseaseobstructive lung disease

Mechanical ventilation in air flow obstruction

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