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

2. RESPIRATORY FAILURE HYPOXEMIA HYPERCAPNIA LUNG PUMP FAILURE FAILURE
GAS EXCHANGE
FAILURE
VENTILATORY
FAILURE
HYPOXEMIA
HYPERCAPNIA

3. 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

4. Why ventilate?- purposes
To maintain or improve ventilation, & tissue oxygenation.
To decrease the work of breathing & improve patient’s comfort.

5. 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

6. Non-Invasive Ventilation
“a form of ventilatory support that avoids airway invasion”
Hill et al Crit Care Med 2007; 35:2402-7

7. Terapia medica + O2 q.b. per SpO2 89-92%
Paziente con riacutizzazione acidotica di BPCO
Terapia medica + O2 q.b. per SpO %

8. Airway Airway narrowing &  Frictional Inflammation obstruction WOB
Shortened
muscles
curvature
Auto-
PEEP
 Elastic
WOB
Gas
trapping
 muscle
strength
 VCO2
 VT
 VE
 VA
PaCO2 pH
PaO2

9. usa i farmaci e bene ! Airway Airway narrowing &  Frictional
obstruction
Airway
Inflammation
Steroids
 Frictional
WOB
Abx
Shortened
muscles
curvature
Auto-
PEEP
BDs
 Elastic
WOB
Gas
trapping
Teophylline
 muscle
strength
 VCO2
 VT
 VE
 VA
PaCO2 pH
PaO2

10. usa i farmaci e bene ! Airway Airway narrowing &  Frictional
obstruction
Airway
Inflammation
Steroids
 Frictional
WOB
Abx
PEEP
Shortened
muscles
curvature
Auto-
PEEP
BDs
 Elastic
WOB
Gas
trapping
Teophylline MV MV
 muscle
strength
 VCO2
 VT
 VE MV
 VA
PaCO2 pH
PaO2

11. Ripetizione di EGA NIV non indicata
Paziente con riacutizzazione acidotica di BPCO
Terapia medica + O2 q.b. per SpO %
Ripetizione di EGA
NIV non indicata
pH > 7.35
>7.30 pH < 7.35
pH < 7.30
pH < 7.20

12. NIV altamente consigliata
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
>7.30 pH < 7.35
NIV altamente consigliata
Senza NIV 1 paziente su 2 necessita di ETI
NIV migliora la sopravvivenza
pH < 7.30
NIV altamente consigliata
1 paziente su 2 fallisce NIV
Tuttavia con NIV migliora outcome ospedaliero e sopravvivenza a 1 anno
pH < 7.20

13. NIV VS TRATTAMENTO STANDARD
Questi vantaggi si sono tradotti in una riduzione significativa della permanenza in ospedale, ed in una riduzione della fR e miglioramento ad 1 ora degli scambi gassosi (riduzione della PaCO2)
Keenan S et al

14. NIV VS TRATTAMENTO STANDARD
Keenan S et al

15. NIV VS TRATTAMENTO STANDARD
Keenan S et al

16. 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: Girou et al JAMA 2000; 284:2361-7

17. 2005; 128
… ci sono alcune considerazioni su questo lavoro che riguardano:
Il fatto di aver in qualche modo selezionato per la randomizzazione solo 64 pazienti su 256 facendo un po’ quello che gli inglesi chiamano “cherry picking” cioè la scelta delle ciliegie migliori dal cestino.
In secondo luogo la miscellanea di cause di IRA con una lieve disproporzione tra i 2 gruppi a vantaggio del gruppo NIV per quanto riguarda i sottogruppi di patologie note per essere più responsive alla NIV (IRA da BPCO e edema polmonare).
IN sostanza però questo studio ci deve ricordare che:
La NIV non è un surrogato della VM per via invasiva e che la NIV rimane inappropriata per molti pazienti con IRA soprattutto quelli con ARDS e MOF
Ma che tuttavia la NIV può essere usata con le opportune indicazioni con l’aspettativa di evitare l’intubazione in alcuni pazienti e le sue complicanze
Che la NIV deve essere comunque applicata in centri selezionati con esperienza e con la possibilità di rapidamente accedere a strutture per la VM per via invasiva.

18. 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 (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%)

19. 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 ridotta permanenza in ICU vs pazienti VM invasiva
NIV riduce necessità di ETI e ospedalizzazione, migliora outcome a lungo termine

20. 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

22. 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

23. Several ways to connect the machine to patient
Oro-tracheal Intubation
Tracheostomy
Non-Invasive
Ventilation

24. Normal breath Normal breath inspiration, awake Lung @ FRC= balance
Diaphragm contracts
-2cm H20
Chest volume
Pleural pressure
-7cm H20
Alveolar
pressure falls
Air moves down
pressure gradient
to fill lungs

25. La pompa diaframmatica genera P garantendo la ventilazione polmonare, regolata da:
Equazione di moto del Sistema Respiratorio:
Pmusc = V / C + V’ x R

26. Normal breath Normal breath expiration, awake -7cm H20
Diaphragm relaxes
Pleural /
Chest volume 
Pleural pressure
rises
-2cm H20
Alveolar
pressure rises
Air moves down
pressure gradient
out of lungs

27. Ventilator breath
Portable ventilator
ICU ventilator
ICU ventilator

28. Ventilator breath Ventilator breath inspiration Air blown in 0 cm H20
 lung pressure
Air moves down
pressure gradient
to fill lungs
+5 to+10 cm H20
 Pleural
pressure

29. Pappl (+ Pmusc) = V / C + V’ x R
Il ventilatore sostituisce totalmente o parzialmente la pompa muscolare:
Equazione di moto del Sistema Respiratorio:
Pappl (+ Pmusc) = V / C + V’ x R

30. Ventilator breath Ventilator breath expiration
Similar to spontaneous…ie passive
Ventilator stops
blowing air in
Pressure gradient
Alveolus-trachea
Air moves out
Down gradient
 Lung volume

31. Practicalities Ventilator settings: Pressure vs volume
‘Assist’ vs ‘Control’
Trigger sensitivity
PEEP?

32. Details: Inspiration Pressure or Volume?
Do you push in..
A gas at a set pressure? = ‘pressure…..’
A set volume of gas? = ‘volume….’

33. Details: Inspiration Pressure or Volume?
Pressure cm H20
Time
Pressure cm H20
Time

34. 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 patient’s inspiratory flow demand throughout inspiration, patient effort is reduced and comfort increased.

35. 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.

36. Details: Inspiration Pressure or Volume?

37. 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 :
- Patient’s lung compliance
- Patient–ventilator resistance factors

38. Peak Inspiratory Pressure (PIP ) must be monitored in volume modes because it varies from breath to breath 30
Peak Inspiratory Pressure P aw
cmH2O
Time (s) 1 2 3
-10

39. Details: Pressure vs Volume
in the Acute Setting
Secretions
hypoventilation
Vt preserved
partial compensation
hypoventilation
sensitive
insensitive
Schönhofer ERS Monograph 2001; 16: , mod

40. Details: leak compensation
without leakage
with leakage
small leak
huge leak
Pre-set
Pressure
Vol
Pressure
Vol
Mehta et al. Eur Respir J 2001; 17:

41. Interaction
Ventilator
Respiratory muscle
pump

42. work of breathing Ventilator Respiratory muscle pump .
spontaneous assisted controlled

44. Noninvasive mechanical ventilation in acute exacerbation of restrictive thoracic disease
Eur Respir Mon 2001; 6:70-73

46. 4 Phases Inspiratory triggering Inspiration Termination of inspiration
Pressure
Flow
Volume
Time
Inspiratory triggering
Inspiration
Termination
of inspiration
Expiration
Nilsestuen et al. Respir Care 2005; 50:

47. Details: trigger sensitivity
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

48. Trigger poco sensibile: allo sforzo inspiratorio non segue l’atto meccanico del respiratore

49. Trigger troppo sensibile: l’atto meccanico si innesca spontaneamente

50. Pao
Pes
patient 1
patient 2
patient 3

51. 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 !

53.  PSV L’operatore imposta: Caratteristiche: - pressione inspiratoria
- sensibilità trigger
- eventuale “rampa” (tempo di raggiungimento PS)
L’operatore imposta: 
- pressure-controlled
flow-cycled
patient-triggered
Caratteristiche:
- > sincronismo paziente-ventilatore  > comfort
- possibile graduazione sforzo inspiratorio

54. lenta media rapida
Diversi tipi di rampa

55. PSV Problemi: difficoltà di impostazione possibile sovrassistenza
livello PS  VT: 6-8ml/Kg; RR: 20-35b/min
P0.1: 2-4 cm H2O
abolizione dissincronismi toraco addominali
possibile sovrassistenza

56.  A-CV L’operatore imposta: Caratteristiche: Problemi:
-volume corrente
-frequenza respiratoria
-rapporto I/E
-sensibilità del trigger
L’operatore 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:

57. A-CV

58. Volume Assured Pressure Support
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

59. Volume Assured Pressure Support
VAPS
Volume Assured Pressure Support

60. Volume Assured Pressure Support
VAPS
Volume Assured Pressure Support

61. Storre et al. Chest 2006;130:

62. AVAPS improves quality of ventilation
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:

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

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

66. Four types of asynchronies:
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.

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

68. Details: PEEP? Positive End Expiratory Pressure Pressure cm H20 PEEP
Time
Positive End Expiratory Pressure

69. Effects of PEEP Normal, Awake Lying down / Paralysis / +- pathology
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’

70. Effects of PEEP ‘over-distended’ alveoli Compliance= Volume
 Pressure
Volume
Curva pressione/volume del sistema respiratorio. La distensibilità è massima nella zona in cui si respira normalmente: 0.1L/cmH2O. Fenomeno dell’isteresi: forza ad una determinata lunghezza è maggiore in fase di allungamento.
energy needed to open alveoli
?damaged during open/closing
- abnormal forces
Pressure

71. Effects of PEEP Compliance= Volume  Pressure Volume
PEEP: start inspiration from a higher pressure
↓?damage during open/closing
Pressure
Raised ‘PEEP’

72. Regional ventilation: PEEP
Spontaneous, standing
‘over-distended’ alveoli
Compliance=
Volume
 Pressure
Volume
Gradiente di pressione pleurica: 0.2cmH2O/cm dipende da forze elastiche (parete) e forze gravitarie (peso polmone) e genera diversa espansibilità parti polmone
Pressure

73. Regional ventilation: PEEP
Mechanical Ventilation
Compliance=
Volume
 Pressure
Volume
Situazione si modifica quando il soggetto respiri ad un livello dimaggiore espirazione, in cui sono le parti alte ad essere più espansibili. Volume di chiusura: volume al quale si chiudono i bronchioli delle regioni polmonari declivi. In alcuni casi è prossimo ad FRC. Applicazione di PEEP aumenta FRC sopra il volume di chiusura delle vie aeree.
Pressure

74. Details: Cardiovascular effects
Compresses Pulmonary vessels
Reduced RV outflow
Reduced LV inflow

78. 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

79. Vent settings to improve <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
Common examples of methylation-induced silencing:
Imprinted genes (Prader-Willi, Angelmann Syndromes)
Inactivated 2nd X chromosome in females
DNA methylation results in histone deacetylation, compacted chromatin, and repression of gene activity
Methylation can have a profound effect in tumorigenesis by silencing tumor suppressors

80. PEEP: Indications Clinical Physiological 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% 

81. 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.