Andrea Vianello S.C. Fisiopatologia Respiratoria Ospedale-Università di Padova QUANDO VENTILARE? CON COSA VENTILARE?

Andrea VianelloS.C. Fisiopatologia Respiratoria

Ospedale-Università di Padova

QUANDO VENTILARE?CON COSA VENTILARE?

RESPIRATORY FAILURE

LUNGFAILURE

PUMP FAILURE

GAS EXCHANGE FAILURE

VENTILATORY FAILURE

HYPOXEMIA HYPERCAPNIA

What’s the point of ventilation?

– Deliver O2 to alveoli

• Hb binds O2 (small amount dissolved)

• CVS transports to tissues to make ATP - do work

– Remove CO2 from pulmonary vessels• from tissues - metabolism

• To maintain or improve ventilation, & tissue oxygenation.

• To decrease the work of breathing & improve patient’s comfort.

Why ventilate?- purposes

When ventilate?- indications• Failure of pulmonary gas exchange

– Hypoxaemia: low blood O2

• “Mechanical” failure– Hypercarbia: high blood CO2

– Respiratory muscle fatigue

• Need to intubate eg patient unconscious

• Others eg – need neuro-muscular paralysis to allow surgery– cardiovascular reasons

Non-Invasive Ventilation

“a form of ventilatory

support that avoids airway

invasion”

Hill et al Crit Care Med 2007; 35:2402-7

Paziente con riacutizzazione acidotica di BPCOPaziente con riacutizzazione acidotica di BPCO

Terapia medica + O2 q.b. per SpO2 89-92%

AirwayInflammatio

n

Airwaynarrowing

&obstructio

nShortened

muscles curvature

FrictionalWOB

musclestrength

VT

PaCO2

pHPaO2

Gastrapping

Auto-PEEP

VCO2 VE

ElasticWOB

VA

AirwayInflammatio

n

Airwaynarrowing

&obstructio

nShortened

muscles curvature

FrictionalWOB

musclestrength

VT

PaCO2

pHPaO2

Gastrapping

Auto-PEEP

VCO2 VE

ElasticWOB

VA

usa i farmaci e bene !usa i farmaci e bene !

Steroids

Abx

BDs

Teophylline

AirwayInflammatio

n

Airwaynarrowing

&obstructio

nShortened

muscles curvature

FrictionalWOB

musclestrength

VT

PaCO2

pHPaO2

Gastrapping

Auto-PEEP

VCO2 VE

ElasticWOB

VA

Steroids

Abx

BDs

Teophylline

MV

MVMV

PEEP

usa i farmaci e bene !usa i farmaci e bene !

Paziente con riacutizzazione acidotica di BPCOPaziente con riacutizzazione acidotica di BPCO

Terapia medica + O2 q.b. per SpO2 89-92%

Ripetizione di EGA

NIV non indicata

pH > 7.35 >7.30 pH < 7.35 pH < 7.30 pH < 7.20

NIV consigliata

l’80% dei pazienti migliora comunque con terapia standard

Ogni 10 pazienti trattati con NIV si evita 1 ETI; NIV migliora la dispnea

NIV altamente consigliata

Senza NIV 1 paziente su 2 necessita di ETI

NIV migliora la sopravvivenza

NIV altamente consigliata

1 paziente su 2 fallisce NIV

Tuttavia con NIV migliora outcome ospedaliero e sopravvivenza a 1 anno

>7

.30

pH

< 7

.35

pH

< 7

.30

pH

< 7

.20

NIV VS TRATTAMENTO STANDARDNIV VS TRATTAMENTO STANDARD

Keenan S et al

NIV VS TRATTAMENTO STANDARDNIV VS TRATTAMENTO STANDARD

Keenan S et al

NIV VS TRATTAMENTO STANDARDNIV VS TRATTAMENTO STANDARD

Keenan S et al

The ICU studies• Confirm the feasibility of NIV• Confirm the effectiveness of NIV• Selected patients / enthusiastic

Units• Reduced complications -

particularly infectious – 16% v 48% 1 ,18 v 60% 2

• Reduce ICU / Hospital stay– 23 v 35 days 1 , 9 v 15 days 2

1. Brochard et al NEJM 1995; 333:817-22 2. Girou et al JAMA 2000; 284:2361-7

2005; 128

49 pazienti con IRA in BPCO dopo fallimento terapia medica, pH 7.2

• Simili durata di permanenza in ICU, durata VM, complicanze generali, mortalità in ICU, e mortalità in ospedale

• con NIV 48% evitano ETI, sopravvivono con permanenza con NIV 48% evitano ETI, sopravvivono con permanenza in ICU inferiorein ICU inferiore vs pazienti VM invasiva (P=0.02)

• A 1 anno: NIV inferiore riospedalizzazione (65% vs 100% P=0.016) e minor frequenza di riutilizzo supplemento di ossigeno (0% vs 36%)

Studio caso-controllo: 64 paz. con IRA trattati con NIV pH = 7.18

• 40/64 (62%) fallimento NIV (RR con NIV - 38%)

• Simili mortalità in ICU, e mortalità in ospedale; durata di permanenza in ICU e post ICU, ma:

• Inferiori complicanze (P=0.01) e probabilità di rimanenere in VM (P=0.056)

• Se NIV efficace (24/64 = 38%) migliore sopravvivenza e migliore sopravvivenza e ridotta permanenza in ICUridotta permanenza in ICU vs pazienti VM invasiva

NIV riduce necessità di ETI e ospedalizzazione, migliora outcome a lungo

termine

Definition: What is it?

• Mechanical Ventilation=Machine to ventilate lungs = move air in (+ out) – Several ways to..move air in (IPPV vs others)

Intermittent Positive Pressure Ventilation

Definition: What is it?

• Mechanical Ventilation=Machine to ventilate lungs = move air in (+ out) – Several ways to..move air in (IPPV vs others)

Intermittent Positive Pressure Ventilation– Several ways to connect the ventilator to

the patient

Several ways to connect the machine to patient

• Oro-tracheal Intubation

• Tracheostomy

• Non-Invasive

Ventilation

Normal breath inspiration, awake

Diaphragm contracts

Chest volume

Pleural pressure

Air moves down pressure gradientto fill lungs

-2cm H20

-7cm H20

Alveolarpressure falls

Normal breath

Lung @ FRC= balance

La pompa diaframmatica genera P garantendo

la ventilazione polmonare, regolata da:

Equazione di moto del Sistema Respiratorio:

Pmusc = V / C + V’ x R

Normal breath expiration, awake

Diaphragm relaxes

Pleural / Chest volume

Pleural pressure rises

Normal breath

Alveolarpressure rises

Air moves down pressure gradientout of lungs

-7cm H20

-2cm H20

Portable ventilatorPortable ventilator

ICU ventilatorICU ventilatorICU ventilatorICU ventilator

Ventilator breath

Ventilator breath inspiration

Air blown in

lung pressure Air moves down pressure gradientto fill lungs

Pleuralpressure

0 cm H20

+5 to+10 cm H20

Ventilator breath

Il ventilatore sostituisce totalmente o parzialmente la pompa muscolare:

Equazione di moto del Sistema Respiratorio:

Pappl (+ Pmusc) = V / C + V’ x R

Ventilator breath expirationSimilar to spontaneous…ie passive

Ventilator stops blowing air in

Pressure gradientAlveolus-trachea

Air moves outDown gradient Lung volume

Ventilator breath

Practicalities

• Ventilator settings: • Pressure vs volume• ‘Assist’ vs ‘Control’• Trigger sensitivity• PEEP?

Details: Inspiration Pressure or Volume?

• Do you push in..– A gas at a set pressure? = ‘pressure…..’– A set volume of gas? = ‘volume….’

Time

Pre

ssur

e cm

H20

Time

Pre

ssur

e cm

H20

Details: Inspiration Pressure or Volume?

• The use of pressure ventilators is increasing in critical care units.

• A typical pressure mode delivers a selected gas pressure to the patient early in inspiration, and sustains the pressure throughout the inspiratory phase.

• By meeting the patient’s inspiratory flow demand throughout inspiration, patient effort is reduced and comfort increased.

Pressure Ventilators

• Although pressure is consistent with these modes, volume is not.

• Volume will change with changes in resistance or compliance

• Therefore, exhaled tidal volume is the variable to monitor closely.

• With pressure modes, the pressure level to be delivered is selected, and with some mode options, rate and inspiratory time are preset as well.

Details: Inspiration Pressure or Volume?

• The volume ventilator has been historically used in critical care settings

• A respiratory rate, inspiratory time, and tidal volume are selected for the mechanical breaths.

• The basic principle of this ventilator is that a designated volume of air is delivered with each breath.

• The amount of pressure required to deliver the set volume depends on :

- Patient’s lung compliance - Patient–ventilator resistance factors

Volume Ventilators

30

Time (s)

-10

1 2

awPcmH2O

Peak Inspiratory Pressure

3

Peak Inspiratory Pressure (PIP ) must be monitored in volume modes because it varies from breath to breath

Schönhofer ERS Monograph 2001; 16: 259-73, mod

hypoventilationhypoventilationpartial compensationpartial compensation

sensitivesensitive insensitiveinsensitive

Secretions hypoventilationhypoventilation Vt preservedVt preserved

Details: Pressure vs Volumein the Acute Setting

Vol Vol Pressure Pressure

without leakage with leakage

small leak

huge leak

Mehta et al. Eur Respir J 2001; 17: 259-267

Pre-set

Details: leak compensation

Respiratory muscle

pump

Ventilator

Interaction

Respiratory muscle pump

Ventilator

work of breathing

spontaneous assisted controlled

.

.

0

50

100

150

200

250

1 2

Patient

Oxyg

en

co

nsu

mp

tio

n m

L x

min

-1

CMV

PSV

SB

SBT

Noninvasive mechanical ventilation in acute exacerbation of restrictive thoracic disease

Eur Respir Mon 2001; 6:70-73

Nilsestuen et al. Respir Care 2005; 50:202-232

1. Inspiratory triggering

2. Inspiration

3. Terminationof inspiration

4. Expiration

4 Phases

Pressure

Flow

Volume

Time

trigger asynchrony

insensitivetrigger

sensitivetrigger

auto-triggering

• trigger sensitivity to low

• high level of PSV

• hypercapnic encephalopathy

• sedation

• sleep

• intrinsic PEEP (COPD)

• tubing obstruction

• trigger sensitivity to high

• resistance changes

• tubing leakage

• cardiac oscillation

Details: trigger sensitivity

Trigger poco sensibile: allo sforzo inspiratorio non segue l’atto meccanico

del respiratore

Trigger troppo sensibile: l’atto meccanico si innesca spontaneamente

Pao

Pes

patient 1 patient 2 patient 3

Asynchrony between patient and ventilator

Problems:• Increased work of breathing• Need for sedation• „Fighting the ventilator“• Ventilation-Perfusion-Mismatch • Dynamic hyperinflation

Consequences:• Insufficient ventilation• Withdrawal from NIV• Weaning failure• Prolonged ICU stay• Costs

Prognosis !

L’operatorL’operatore imposta:e imposta:

PSVPSV

CaratteristichCaratteristiche:e:

- pressure-controlled- flow-cycled- patient-triggered

- pressione inspiratoria- sensibilità trigger- eventuale “rampa” (tempo di raggiungimento PS)

- > sincronismo paziente-ventilatore > comfort- possibile graduazione sforzo inspiratorio

lenta media rapida

Diversi tipi di rampa

PSVPSV

Problemi:Problemi: - difficoltà di impostazione- livello PS VT: 6-8ml/Kg; RR: 20-35b/min

P0.1: 2-4 cm H2O abolizione dissincronismi toraco- addominali

- possibile sovrassistenza

L’operatore L’operatore

impostaimposta::

A-CVA-CV

CaratteristicheCaratteristiche::

-volume-controlled-time-cycled-machine e/o patient-triggered (assistito)-pressure-limited (eventuale)

-volume corrente-frequenza respiratoria -rapporto I/E-sensibilità del trigger

ProblemiProblemi: : - possibile sovrassistenza alcalosi respiratoria- insorgenza di PEEP intrinseca

- volume corrente insufflato garantito- rapporto I/E variabile

A-CVA-CV

Hybrid modescombine the advantages of pressure pre-set and volume pre-set

VAPS

Volume Assured Pressure Support

• Automatic adjustment of inspiratory pressure (range setting)

• Target volume set

• Measurement of inspiratory pressure and expiratory volume

• Calculation of missing inspiratory volume

• Increase of inspiratory pressure

Assurance of tidal volume + comfort of pressure pre-set

VAPS

Volume Assured Pressure Support

VAPS

Volume Assured Pressure Support

Storre et al. Chest 2006;130: 815-821

Storre et al. Chest 2006; 130: 815-821

• AVAPS provides elegant adjustments of inspiratory pressures

according to a pre-set target volume

• AVAPS improves quality of ventilation

• Improvements of sleep quality and quality of life are comparable to

BiPAP-S/T

• However: Sleep quality is not completely normalized

• Further studies are needed

Efficacy and comfort of Volume-Guaranteed Pressure Support (PSV-VTG) in patients with chronic ventilatory failure of neuromuscular origin

Efficacy and comfort of Volume-Guaranteed Pressure Support (PSV-VTG) in patients with chronic ventilatory failure of neuromuscular origin

Efficacy and comfort of Volume-Guaranteed Pressure Support (PSV-VTG) in patients with chronic ventilatory failure of neuromuscular origin

Four types of asynchronies:• Ineffective inspiratory effort (IE): thoraco-abdominal displacements not assisted by the ventilator positive pressure boost;• Inspiratory trigger delay: a time lag between the initiation of the patent’s IE and the onset of inspiratory support;• Prolonged inspiration or late expiratory cycling (hang-up): prolongation of mechanical insufflation beyond the end of patient inspiration;• Autotriggering: rapid succession of at least three pressurizations at a RR of >40 br/min.

Efficacy and comfort of Volume-Guaranteed Pressure Support (PSV-VTG) in patients with chronic ventilatory failure of neuromuscular origin

Time

Pre

ssur

e cm

H20

Details: PEEP?

PEEP

Positive End Expiratory Pressure

Effects of PEEP

Normal, Awake – in expiration alveoli do not close (closing capacity)– change size

Lying down / Paralysis / +- pathology– Lungs smaller, compressed– Harder to distend, starting from a smaller volume– In expiration alveoli close (closing capacity)

PEEP– Keeps alveoli open in expiration– Danger: applied to all alveoli– Start at higher point on ‘compliance curve’

Effects of PEEPV

olum

e

Pressure

Compliance=

Volume Pressure

energy needed to open alveoli

?damaged during open/closing

- abnormal forces

‘over-distended’ alveoli

Effects of PEEPV

olum

e

Pressure

Compliance=

Volume Pressure

Raised ‘PEEP’

PEEP: start inspiration from a higher pressure

↓?damage during open/closing

Regional ventilation: PEEPV

olum

e

Pressure

Compliance=

Volume Pressure

‘over-distended’ alveoli

Spontaneous, standing

Regional ventilation: PEEPV

olum

e

Pressure

Compliance=

Volume Pressure

Mechanical Ventilation

Details: Cardiovascular effects

• Compresses Pulmonary vessels

• Reduced RV outflow

• Reduced LV inflow

Details: Cardiovascular effects

• Compresses Pulmonary vessels• Reduced LV inflow

Cardiac Output: Stroke Volume– Blood Pressure = CO x resistance –

Blood Pressure

– Neurohormonal

• Reduced RV outflow- backtracks to body– Head- Intracranial Pressure– Others - venous pressure

Vent settings to improve Vent settings to improve <oxygenation><oxygenation>

PEEP • Increases FRC

• Prevents progressive atelectasis and intrapulmonary shunting

• Prevents repetitive opening/closing (injury)

• Recruits collapsed alveoli and improves V/Q matching• Resolves intrapulmonary shunting

• Improves compliance

• Enables maintenance of adequate PaO2 at a safe FiO2 level

• Disadvantages• Increases intrathoracic pressure (may

require pulmonary a. catheter)

• Rupture: PTX, pulmonary edema

Clinical • Auto-PEEP• Cardiogenic pulmonary edema (↑ LV preload)• Hypoxemia with FIO2 > 0.5• Collapsing alveoli (ARDS, postop atelectasis)• Chest wall instability (chest trauma)Physiological• PaO2 < 60 mm Hg on FIO2 0.8• PaO2 ↑ < 10 mm Hg with FIO2 F of 0.2• PA-aO2 > 300 on FIO2 1.0• Shunt > 30% 

PEEP: Indications

NIV treatment: summary

• The ventilator management of NIV is continuously evolving;

• New ventilators are introduced, offering novel features;

• Clinical applications have been expanding;• Clinicians must make selections that best

match the ventilator with the patient’s requirements.