Post on 26-Mar-2015
transcript
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.