Conventional Mechanical Conventional Mechanical Ventilation for Respiratory Ventilation for Respiratory

Failure in COPDFailure in COPD

Dr.T.R.Chandrashekar Dr.T.R.Chandrashekar M.DM.D

Director critical careDirector critical careK.R.Hospital, BangaloreK.R.Hospital, Bangalore..

COPDCOPD It is defined as a It is defined as a preventablepreventable and and treatable treatable

disease state characterized by airflow disease state characterized by airflow limitation that is not fully reversible limitation that is not fully reversible

The airflow limitation is in most cases is both The airflow limitation is in most cases is both

progressiveprogressive and associated with an abnormal and associated with an abnormal inflammatory response of the lungs to noxious inflammatory response of the lungs to noxious particles or gasesparticles or gases..

Although COPD affects the lungs, it also Although COPD affects the lungs, it also produces significant produces significant systemic consequencessystemic consequences

Systemic effects of COPDSystemic effects of COPDEffects Mechanism

Why COPD is Important ?Why COPD is Important ? COPD is the only chronic disease that is COPD is the only chronic disease that is

showing progressive upward trend in both showing progressive upward trend in both mortalitymortality and and morbiditymorbidity

It is expected to be the It is expected to be the thirdthird leading cause leading cause of death by 2020of death by 2020

Approximately Approximately 14 million14 million Indians are Indians are currently suffering form COPD*currently suffering form COPD*

Currently there are 94 million smokers in Currently there are 94 million smokers in IndiaIndia

10 lacs Indians die in a year due to smoking 10 lacs Indians die in a year due to smoking related diseasesrelated diseases

**The Indian J Chest Dis & Allied Sciences 2001; 43:139-47The Indian J Chest Dis & Allied Sciences 2001; 43:139-47

In COPD limitation is EFIn COPD limitation is EF No conventional ventilator supports No conventional ventilator supports

expiration activelyexpiration actively How does MV help ?How does MV help ? Although the load is expiratory the Although the load is expiratory the

failure is inspiratory failure is inspiratory

Inspiratory muscle loading and fatigueis of central pathophysiological importance in the development of acute respiratory failure

Pathophysiology of COPDPathophysiology of COPD

Expiratory flow limitation is the primary problem

Lung Capacity and DiseaseLung Capacity and Disease

Space for fresh air

TLC

The Vicious CycleThe Vicious Cycle

Increased resistance Airtrapping

DecreasedCompliance

↑PVR

>DH

>DH

WOB

FATIGUE

↑PCO2/↓Pao2↓PH

V/Q mismatch

Identify & Measure

Complications

Manage

COPDKey factor is

DH Auto PEEP

PEEPiEELV

Concept of DHConcept of DH It is a adaptive mechanism which It is a adaptive mechanism which

leads to increased elastic recoil leads to increased elastic recoil force and keeps airways patent to force and keeps airways patent to force out air but….force out air but….

Due to use of accessory muscle Due to use of accessory muscle usage increased force is also applied usage increased force is also applied to airways which lead to collapse & to airways which lead to collapse & exaggerate the EFLexaggerate the EFL

Concept of Auto PEEP, DHConcept of Auto PEEP, DH AUTO PEEP is defined as the AUTO PEEP is defined as the

difference between PEEP set by the difference between PEEP set by the clinician and the PEEP as measured clinician and the PEEP as measured by the ventilator with an expiratory by the ventilator with an expiratory hold. hold.

Identification of Auto PEEPIdentification of Auto PEEP

Inspiration

Expiration

NormalNormalPatientPatient

Time (sec)

Flow

(L/m

in)

Air TrappingAuto-PEEP

}

Measurement of Auto PEEPMeasurement of Auto PEEP

Reduce set PEEP to zero before measuring Auto PEEP

Paralysed patient only

AT HE END OF EXPIRATION 2 -3 SEC OCCULSION

Auto-PEEP and Volume of Trapped Auto-PEEP and Volume of Trapped GasGas

Tuxen, Am Rev Respir Dis 1989; 140:5

WHAT ARE EFFECTS OF AUTO PEEP?WHAT ARE EFFECTS OF AUTO PEEP?

Hemodynamic compromise.Hemodynamic compromise.

Due to increase in FRC, respiration starts in Due to increase in FRC, respiration starts in the flatter portion of the P/V curve, where the flatter portion of the P/V curve, where change in volume for a change in pressure is change in volume for a change in pressure is less –Increased WOB.less –Increased WOB.

Trigger will have to cross the auto PEEP level Trigger will have to cross the auto PEEP level before inspiration is initiated.before inspiration is initiated.

Missed breathsMissed breaths

Mechanical Effects of AECOPDMechanical Effects of AECOPD

Thorax 2006;61:354-61

AUTOPEEP AND TRIGGER

Time (sec)

Pressure (cmH20)

AUTOPEEP

BASELINE BASELINE SHIFTS

Missed breath

Auto PEEP

Wasted effort, increased WOB

There are only 3 factors that There are only 3 factors that determine auto-PEEP.determine auto-PEEP.

Minute ventilation. (It doesn’t matter Minute ventilation. (It doesn’t matter whether it’s from respiratory rate or whether it’s from respiratory rate or VT). VT).

I: E [inspiratory: expiratory] ratio. I: E [inspiratory: expiratory] ratio. Expiratory time constants.Expiratory time constants.

Let us learn how to manipulate these parameters

To prevent Auto PEEP

CO2 removal is inversely proportional to Minute Ventilation

CO2 removal is inversely proportional to Effective Alveolar Ventilation

Effective Alveolar Ventilation = Minute Ventilation – Dead Space Ventilation

Po2 is 60, PCo2 is 68

Increase Vt to 500ml

Increase RR 15

After one hr repeat ABG shows PO2 of 58PCO2 of 83

COPD on ventilator on VC COPD on ventilator on VC Vt 500ml, Fio2 40%, PEEP 4cms H2o Vt 500ml, Fio2 40%, PEEP 4cms H2o

RR10/mt, I:E 1:2RR10/mt, I:E 1:2 Minute ventilation of 500x10=5000

Minute ventilation of 500x15=7500

Effective Alveolar ventilationEffective Alveolar ventilation Vt=500mlVt=500ml RR=10RR=10 MV=5lMV=5l EAV=MV-Dead space EAV=MV-Dead space Dead space Dead space

ventilationventilation =150x10=1.5l=150x10=1.5l

EAV=5l-1.5l=3.5lEAV=5l-1.5l=3.5l

Vt-500mlVt-500ml RR= 15RR= 15 MV=7.5lMV=7.5l EAV=MV-Dead space EAV=MV-Dead space Dead space Dead space

ventilationventilation =300x15=4.5l=300x15=4.5l

EAV=7.5l-4.5l=3.0lEAV=7.5l-4.5l=3.0l

FRC EELV/DH

COPD

compliance

Resistance PVR

Respiratory rate Respiratory rate RR 10breaths/ min, RR 10breaths/ min, If I:E ratio 1:2 Total cycle time 60 sec/10 = 6 secTotal cycle time 60 sec/10 = 6 sec

Inspiration = 2seconds Expiration 4 secondsRR 20 breaths/ mt, I:E Ratio 1:2, TCT=60/20=3 sec

Inspiration = 1seconds Expiration 2 seconds

3 sec

1sec2 sec

Minute ventilationMinute ventilation Tidal volume=6-7ml/kgTidal volume=6-7ml/kg Rate 12/mt, IC is reducedRate 12/mt, IC is reduced Low minute ventilation leads to Low minute ventilation leads to ↑↑PCO2 PCO2

which is the price we pay for preventing which is the price we pay for preventing DH,DH,

In fact current literature suggests that In fact current literature suggests that risk of dynamic hyperinflation is much risk of dynamic hyperinflation is much larger than those of permissive larger than those of permissive hypercapnia.hypercapnia.

Provide enough ventilation to Provide enough ventilation to keep a keep a normal PH,normal PH, not a normal PCO2. not a normal PCO2.

Manipulate - I:E RatioManipulate - I:E Ratio

Pressure

Time

Gives more time for expiration and reduces DH

T insp. . I : E = 1 : 2

I : E = 1: 3

PEEP

PIP

PIP

PEEP

T insp.

T exp

Total cycle time

Peak flowPeak flow Normally in adults it is set between Normally in adults it is set between

40-60l/min, or can be calculated as 40-60l/min, or can be calculated as follows follows

Ins timeTidal volumePEAK

FLOW = X 60

A peak flow of around 80-90l/mt

RISE TIMERISE TIME

40PCIRCcmH2O

INSP

Lmin

EXP

302010 010

-2080604020020

-80

4060

V.

0 4 8 12s2 6 10

Slow rise Moderate rise Fast rise

TETE TE

TI

PEAK FLOWPEAK FLOW

Peak Flow 30l/mt

Peak Flow 90l/mt

Addition of external PEEP Addition of external PEEP “The Paradox“The Paradox “ “

+6 +6 +7

Pleural

Alveolus

Mouth

start of Inspiration

Airway Pressures with Auto-PEEP

Auto-PEEP = +6

Wilson et al, U of Iowa

Can PEEP be used in all COPD pts?Can PEEP be used in all COPD pts? Whenever accessory muscles are in use to Whenever accessory muscles are in use to

counter act them PEEP can be usedcounter act them PEEP can be used when patients are on partial/ supported when patients are on partial/ supported

modesmodes

In asthmatics and when patients are In asthmatics and when patients are paralysed the response can be variable paralysed the response can be variable and unpredictable…and unpredictable…

Then the question arises how to be sure it Then the question arises how to be sure it is not harmful?is not harmful?

Monitoring the response to external Monitoring the response to external PEEPPEEP

Pres

sure

(cm

H2O

)

Flow

(L/m

in)

time (s)

Pres

sure

(cm

H2O

)

Flow

(L/m

in)

time (s)

0 cm H2O PEEP

8 cm H2O PEEP

Auto peep

Calculation of Exp time constantsCalculation of Exp time constants Compliance x ResistanceCompliance x Resistance 0.1l/cmH2O x 5 cmH2O/l/sec= o.5 sec0.1l/cmH2O x 5 cmH2O/l/sec= o.5 sec 0.5 x3= 1.5 sec0.5 x3= 1.5 sec Increased resistanceIncreased resistance 0.1 x 20 = 2sec0.1 x 20 = 2sec 2x3=6sec2x3=6sec

Management of Auto PEEP.Management of Auto PEEP.1) low tidal volume1) low tidal volume Decrease the RRDecrease the RR

2) Increase expiratory time.2) Increase expiratory time.3) Increase peak flow3) Increase peak flow4) Addition of Extrinsic PEEP4) Addition of Extrinsic PEEP5)5) Sedation/Control of FeverSedation/Control of Fever6) Bronchodilatation6) Bronchodilatation

}}}

Low MINUTE VENTILATION

Ventilatory support in Ventilatory support in COPD……COPD……

ARF-COPDARF-COPD

ABGABGPH-7.45PH-7.45PO2-57mmHgPO2-57mmHgPCO2-65mmHgPCO2-65mmHgSpo2-89%Spo2-89%HCo3-34mmolesHCo3-34mmoles

Patient is 60 yr old has Patient is 60 yr old has COPD on room airCOPD on room air

Comfortable Comfortable RR-25/mtRR-25/mt HR-100/mtHR-100/mt

ARF-COPDARF-COPD

ABGABGPH-7.30PH-7.30PO2-57mmHgPO2-57mmHgPCO2-65mmHgPCO2-65mmHgSpo2-89%Spo2-89%HCo3-23mmolesHCo3-23mmoles

Patient is restlessPatient is restlessDisoriented Disoriented Accessory muscle usedAccessory muscle usedRR-35/mtRR-35/mtParadoxical breathingParadoxical breathing0n 4l of oxygen on resv 0n 4l of oxygen on resv

bag.bag.

Baseline Pco2, PH, WOB, Hemodynamic stability,FIO2,Mentation

Should be kept in mind while interpreting ABG’s and decision to ventilate

Spontaneous Weaning

Controlled

Conventional ventilation NIVMechanical ventilation

Ventilation difficulties in COPDVentilation difficulties in COPD Ventilating a COPD patient is Ventilating a COPD patient is

difficult because the disease may difficult because the disease may notnot have a reversible component, have a reversible component,

Quantifying dynamic hyper inflation Quantifying dynamic hyper inflation at bedside is very difficult at bedside is very difficult

COPD patients are difficult to wean. COPD patients are difficult to wean. Co morbidities & systemic effectsCo morbidities & systemic effects

60 yr old COPD patient is60 yr old COPD patient is Drowsy, disorientedDrowsy, disoriented RR-40/mt, accessory muscle+,RR-40/mt, accessory muscle+, BP-80/50mmHg,BP-80/50mmHg, ABG –PH-7.08, ABG –PH-7.08, PCO2-85mmHg,Pao2-49mmHg,PCO2-85mmHg,Pao2-49mmHg, SPo2-83% on 5l of oxygen SPo2-83% on 5l of oxygen oror COPD pt on NIV after 2hrs restless , not COPD pt on NIV after 2hrs restless , not

synchronizing, PH,PCO2,PO2 deterioratedsynchronizing, PH,PCO2,PO2 deteriorated

Case scenario

Indications for Invasive Indications for Invasive Mechanical Ventilation.Mechanical Ventilation.

NIPPV failure.NIPPV failure.

Severe dyspnea with use of accessory muscles+.Severe dyspnea with use of accessory muscles+. RR> 35 breaths per minute.RR> 35 breaths per minute. Life-threatening hypoxemia (PaO2, 50-40 mm Hg).Life-threatening hypoxemia (PaO2, 50-40 mm Hg). Severe acidosis (pH < 7.25) and hypercapnia ( >60 Severe acidosis (pH < 7.25) and hypercapnia ( >60

mm Hg).mm Hg). Respiratory arrest. Somnolence, impaired mental Respiratory arrest. Somnolence, impaired mental

status.status. Cardiovascular complications (hypotension, shock, Cardiovascular complications (hypotension, shock,

heart failure).heart failure).

Intubation and MVIntubation and MV

Decision to intubate if the patient is Decision to intubate if the patient is not a candidate for NIV or has not not a candidate for NIV or has not done well on NIV- has to be made done well on NIV- has to be made decisivelydecisively and if delayed both and if delayed both morbidity and mortality are higher.morbidity and mortality are higher.

Post intubation bagging has to be Post intubation bagging has to be low tidal volume and low rate low tidal volume and low rate 6-7/mt.6-7/mt. If paralysed keep them on relaxants for a day or two.

Fill them adequately before induction ,

Add a small dose of a inotrope in a corpulmonale patient

Ventilatory settings in passive ptVentilatory settings in passive pt Set a moderate FIO2, usually 40%, target Set a moderate FIO2, usually 40%, target

a SPO2 of 90%a SPO2 of 90% Mode –Volume controlled, square wave.Mode –Volume controlled, square wave. Tidal volume =Tidal volume = RR=RR=

I: E ratio =I: E ratio =

FlowFlow

7ml/kg12/mt

=80-100l/mt

1:3 or more depending on expiratory time constants

Ventilation in a passive patientVentilation in a passive patient External-PEEP application has a External-PEEP application has a variable and variable and

unpredictable responseunpredictable response

Due to no contribution of the expiratory Due to no contribution of the expiratory muscles, the reason how external PEEP helps to muscles, the reason how external PEEP helps to reduce DHreduce DH

Reducing the lung heterogeneity. Reducing the lung heterogeneity.

Opening up previously closed units it could help Opening up previously closed units it could help in mucus clearance and bronchodilator therapy.in mucus clearance and bronchodilator therapy.

Paw

(cm

HPa

w (

cm H

22O)

O)

Normal

Normal PPlat(Normal Compliance)

Increased PIP

} Increased PTA(increased Airway Resistance))

Increased Airway Resistance

Begin InspirationBegin Expiration

P aw (

cm H

2O)

Time (sec)

Airwa

y Res

istan

ce

Distending

(Alveolar) Pressure

Expiration

Inflation Hold(seconds)

PIP

A PIP = 40-45 cmH2O.A PIP = 40-45 cmH2O. Ppl pressure < 30cmH2O.Ppl pressure < 30cmH2O. Minimal sensitivity- Pressure or Flow Minimal sensitivity- Pressure or Flow

trigger.trigger. PEEP setting- Start at 5 cmH2O, any PEEP setting- Start at 5 cmH2O, any

further increase always look at PIP and further increase always look at PIP and plateau pressure.plateau pressure.

Any increase in these pressures, decrease Any increase in these pressures, decrease PEEP. (Keep a close watch on PEEP. (Keep a close watch on hemodynamics)hemodynamics)

Ventilating a spontaneous patientVentilating a spontaneous patient

PS /PC mode/PAVPS /PC mode/PAV Pressure support to generate 7ml/Kg Pressure support to generate 7ml/Kg

VTVT Minimal trigger setting- flow or Minimal trigger setting- flow or

pressurepressure Peak flow -80-100l/minPeak flow -80-100l/min PEEP can be added starting at PEEP can be added starting at

5cmH2O in an increments of 2cmH2O 5cmH2O in an increments of 2cmH2O

Ventilating a spontaneous patientVentilating a spontaneous patient You rarely require more than 10cmH2O PEEP.You rarely require more than 10cmH2O PEEP. Expiratory sensitivity (PS) can be set much Expiratory sensitivity (PS) can be set much

above the default setting of 25%.( 40%)above the default setting of 25%.( 40%) If the patient is not synchronizing, increasing If the patient is not synchronizing, increasing

PS could lead to increased VT, DH, and missed PS could lead to increased VT, DH, and missed breaths. breaths.

In such a situation other causes like fever, pain In such a situation other causes like fever, pain etc have to be looked for. In case no other etc have to be looked for. In case no other cause can be found, sedation can be usedcause can be found, sedation can be used..

5353

CYCLING AT CYCLING AT 40% OF 40% OF FLOWFLOW

CYCLING AT 25% CYCLING AT 25% 0F PEAK FLOW0F PEAK FLOW

PRESSURE PRESSURE SUPPORTSUPPORT

Flow cycling

Flow

Time

Peak flow

40%

25%

WeaningWeaning Weaning begins when the Weaning begins when the

precipitating factor of the respiratory precipitating factor of the respiratory failure is partially or totally reversed. failure is partially or totally reversed.

Marginal respiratory mechanics. Marginal respiratory mechanics. Factors which increase resistance like Factors which increase resistance like

size of the tube, deposition of size of the tube, deposition of secretions in the tube, secretions in the tube, kinking/curvature of the tube, kinking/curvature of the tube, presence of elbow-shaped parts, HME presence of elbow-shaped parts, HME in the circuitin the circuit

Steroids + Relaxants Myopathy

WeaningWeaning Role of tracheostmy is uncertain, but due to Role of tracheostmy is uncertain, but due to

marginal respiratory mechanics it is thought it may marginal respiratory mechanics it is thought it may help in weaning. help in weaning.

Weaning can be done with PS mode to SBT. Weaning can be done with PS mode to SBT.

In very difficult cases extubation on to NIV is a In very difficult cases extubation on to NIV is a optionoption

Corpulmonale may warrant small dose of inotrope, a Corpulmonale may warrant small dose of inotrope, a dose of diuretic & low fluid strategy during weaning.dose of diuretic & low fluid strategy during weaning.

IN COPDIN COPD Preventing VILI is not the primary objective Preventing VILI is not the primary objective

here;here;

Avoiding barotrauma, improving airway Avoiding barotrauma, improving airway clearance, and reducing the consequences of clearance, and reducing the consequences of hyperinflation have been the motivators. hyperinflation have been the motivators.

Yet, use of small VT for avoidance of high Yet, use of small VT for avoidance of high plateau pressure,plateau pressure,

Acceptance of permissive hypercapnia,Acceptance of permissive hypercapnia,

Judicious use of PEEP to lessen effort and Judicious use of PEEP to lessen effort and perhaps to reopen compromised airways in perhaps to reopen compromised airways in some patients now guide the care of obstructed some patients now guide the care of obstructed patients patients as well.as well.

Stop Smoking……