Andrea Vianello

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QUANDO VENTILARE? CON COSA VENTILARE?

• Andrea Vianello
• S.C. Fisiopatologia Respiratoria
• Ospedale-Università di Padova

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RESPIRATORY FAILURE
LUNG FAILURE
PUMP FAILURE
GAS EXCHANGE FAILURE
VENTILATORY FAILURE
HYPERCAPNIA
HYPOXEMIA
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• Whats 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

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Why ventilate?- purposes

• To maintain or improve ventilation, tissue
  oxygenation.
• To decrease the work of breathing improve
  patients comfort.

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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

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Non-Invasive Ventilation
a form of ventilatory support that avoids airway
invasion
Hill et al Crit Care Med 2007 352402-7
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Paziente con riacutizzazione acidotica di BPCO
Terapia medica O2 q.b. per SpO2 89-92
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Airway narrowing obstruction
Airway Inflammation
? Frictional WOB
Auto- PEEP
Shortened muscles curvature
? Elastic WOB
Gas trapping
? muscle strength
? VT
? VE
? VA

• PaCO2
• pH
• PaO2

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usa i farmaci e bene !
Airway narrowing obstruction
Airway Inflammation
Steroids
? Frictional WOB
Abx
Auto- PEEP
Shortened muscles curvature
BDs
? Elastic WOB
Gas trapping
Teophylline
? muscle strength
? VT
? VE
? VA

• PaCO2
• pH
• PaO2

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usa i farmaci e bene !
Airway narrowing obstruction
Airway Inflammation
Steroids
? Frictional WOB
Abx
PEEP
Auto- PEEP
Shortened muscles curvature
BDs
? Elastic WOB
Gas trapping
Teophylline
MV
? muscle strength
? VT
? VE
MV
? VA

• PaCO2
• pH
• PaO2

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Paziente con riacutizzazione acidotica di BPCO
Terapia medica O2 q.b. per SpO2 89-92
Ripetizione di EGA
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NIV consigliata l80 dei pazienti migliora
comunque con terapia standard Ogni 10 pazienti
trattati con NIV si evita 1 ETI NIV migliora la
dispnea
gt7.30 pH lt 7.35
NIV altamente consigliata Senza NIV 1 paziente su
2 necessita di ETI NIV migliora la sopravvivenza
pH lt 7.30
NIV altamente consigliata 1 paziente su 2
fallisce NIV Tuttavia con NIV migliora outcome
ospedaliero e sopravvivenza a 1 anno
pH lt 7.20
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NIV VS TRATTAMENTO STANDARD
Keenan S et al
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NIV VS TRATTAMENTO STANDARD
Keenan S et al
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NIV VS TRATTAMENTO STANDARD
Keenan S et al
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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 333817-22 2. Girou
et al JAMA 2000 2842361-7
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2005 128
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• 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 in ICU inferiore vs pazienti VM
  invasiva (P0.02)
• A 1 anno NIV inferiore riospedalizzazione (65
  vs 100 P0.016) e minor frequenza di riutilizzo
  supplemento di ossigeno (0 vs 36)

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• 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 (P0.01) e probabilità di
  rimanenere in VM (P0.056)
• Se NIV efficace (24/64 38) migliore
  sopravvivenza e ridotta permanenza in ICU vs
  pazienti VM invasiva

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

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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

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Several ways to connect the machine to patient

• Oro-tracheal Intubation
• Tracheostomy
• Non-Invasive
• Ventilation

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Normal breath
Normal breath inspiration, awake
Lung _at_ FRC balance
Diaphragm contracts
-2cm H20
?Chest volume
?Pleural pressure
-7cm H20
Alveolar pressure falls
Air moves down pressure gradient to fill lungs
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La pompa diaframmatica genera ?P garantendo la
ventilazione polmonare, regolata da

• Equazione di moto del Sistema Respiratorio
• Pmusc V / C V x R

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Normal breath
Normal breath expiration, awake
-7cm H20
Diaphragm relaxes
Pleural / Chest volume ?
Pleural pressure rises
Alveolar pressure rises
-2cm H20
Air moves down pressure gradient out of lungs
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Ventilator breath
Portable ventilator
ICU ventilator
ICU ventilator
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Ventilator breath
Ventilator breath inspiration
Air blown in
0 cm H20
? lung pressure
Air moves down pressure gradient to fill lungs
5 to10 cm H20
? Pleural pressure
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Il ventilatore sostituisce totalmente o
parzialmente la pompa muscolare

• Equazione di moto del Sistema Respiratorio
• Pappl ( Pmusc) V / C V x R

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Ventilator breath
Ventilator breath expiration Similar to
spontaneousie passive
Ventilator stops blowing air in
Pressure gradient Alveolus-trachea
Air moves out Down gradient
? Lung volume
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Practicalities

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

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Details Inspiration Pressure or Volume?

• Do you push in..
• A gas at a set pressure? pressure..
• A set volume of gas? volume.

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Details Inspiration Pressure or Volume?
Pressure cm H20
Time
Pressure cm H20
Time
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Pressure Ventilators

• 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 patients inspiratory flow demand
  throughout inspiration, patient effort is reduced
  and comfort increased.

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• 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.

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Details Inspiration Pressure or Volume?
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Volume Ventilators

• 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
• - Patients lung
  compliance
• - Patientventilator
  resistance factors

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Peak Inspiratory Pressure (PIP ) must be
monitored in volume modes because it varies from
breath to breath
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Peak Inspiratory Pressure
P
aw
Time (s)
cmH2O
1
2
3
-10
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Details Pressure vs Volume in the Acute Setting
Secretions
hypoventilation
Vt preserved
partial compensation
hypoventilation
sensitive
insensitive
Schönhofer ERS Monograph 2001 16 259-73, mod
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Details leak compensation
without leakage
with leakage
Vol
Vol
Pressure
Pressure
Pre-set
Mehta et al. Eur Respir J 2001 17 259-267
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Interaction
Ventilator
Respiratory muscle pump
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Ventilator
Respiratory muscle pump
work of breathing
spontaneous assisted controlled
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Noninvasive mechanical ventilation in acute
exacerbation of restrictive thoracic disease
Eur Respir Mon 2001 670-73
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4 Phases

• Inspiratory triggering
• Inspiration
• Termination
• of inspiration
• Expiration

Nilsestuen et al. Respir Care 2005 50202-232
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Details trigger sensitivity
trigger asynchrony
insensitive trigger
sensitive trigger
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

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Trigger poco sensibile allo sforzo inspiratorio
non segue latto meccanico del respiratore
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Trigger troppo sensibile latto meccanico si
innesca spontaneamente
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Asynchrony between patient and ventilator
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PSV
- pressione inspiratoria - sensibilità trigger -
eventuale rampa (tempo di raggiungimento PS)
Loperatore imposta
?

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

Caratteristiche
- gt sincronismo paziente-ventilatore
? gt comfort - possibile graduazione
sforzo inspiratorio
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lenta media rapida
Diversi tipi di rampa
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PSV
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

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A-CV
-volume corrente -frequenza respiratoria
-rapporto I/E -sensibilità del trigger
Loperatore imposta

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

?
- volume corrente insufflato garantito - rapporto
I/E variabile
Caratteristiche
- possibile sovrassistenza ? alcalosi
respiratoria - insorgenza di PEEP intrinseca
Problemi
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A-CV
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Hybrid modes combine 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
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VAPS Volume Assured Pressure Support
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VAPS Volume Assured Pressure Support
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Storre et al. Chest 2006130 815-821
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• 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

Storre et al. Chest 2006 130 815-821
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Efficacy and comfort of Volume-Guaranteed
Pressure Support (PSV-VTG) in patients with
chronic ventilatory failure of neuromuscular
origin
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• 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 patents 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 gt40 br/min.

Efficacy and comfort of Volume-Guaranteed
Pressure Support (PSV-VTG) in patients with
chronic ventilatory failure of neuromuscular
origin
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Efficacy and comfort of Volume-Guaranteed
Pressure Support (PSV-VTG) in patients with
chronic ventilatory failure of neuromuscular
origin
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Details PEEP?
Pressure cm H20
PEEP
Time
Positive End Expiratory Pressure
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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

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Effects of PEEP
over-distended alveoli
Compliance ?Volume ? Pressure
Volume
energy needed to open alveoli ?damaged during
open/closing - abnormal forces
Pressure
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Effects of PEEP
Compliance ?Volume ? Pressure
Volume
PEEP start inspiration from a higher
pressure ??damage during open/closing
Pressure
Raised PEEP
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Regional ventilation PEEP
Spontaneous, standing
over-distended alveoli
Compliance ?Volume ? Pressure
Volume
Pressure
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Regional ventilation PEEP
Mechanical Ventilation
Compliance ?Volume ? Pressure
Volume
Pressure
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Details Cardiovascular effects

• Compresses Pulmonary vessels
• Reduced RV outflow
• Reduced LV inflow

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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

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Vent settings to improve ltoxygenationgt

• 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

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PEEP Indications

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

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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 patients requirements.