Transcript Quantifying of Agitation in ICU Patients

Man and machines:
Insights into
ventilation strategies
May 2006
Dr Geoff Shaw
Dept of Intensive Care Christchurch Hospital
Clin Sen Lecturer Dept of Medicine CSM&HS University of Otago, NZ
Senior fellow Dept of Mechanical Engineering, University of Canterbury, NZ
The ventilator is our identity
The ventilator is our identity
Mechanical ventilation has been used clinically for
about 80 years…..
First there was
Negative pressure ventilation…
Polio in California
The ventilator is our identity
Then there was
Positive Pressure Ventilation:
90% death rate  90% survival
Dr H Lassen at Copenhagen’s Blegdams Hospital
PEEP
1967 First report of ARDS:
Ashbaugh DG, Bigelow DB, Petty TL, Levine BE. Acute respiratory
distress syndrome in adults. Lancet; 1967,(II) 319-323
1972 First formal investigation of the effect of PEEP
Improved PaO2 by applying 0-15cm PEEP in 10 patients with
ARDS. Putative mechanism  prevention of airway closure
Falke KJ, Pontoppidan H, Kumar A et al Ventilation with end- expiratory
pressure in acute lung disease; J Clin Invest 1972, 51:2315–2323
PEEP
1975 “Optimum PEEP”
Defined as best O2 transport (CO X O2 content)
highest compliance of respiratory system.
Suter PM, Fairley B, Isenberg MD. Optimum end-expiratory airway
pressure in patients with acute pulmonary failure. N Engl J Med 1975;
292:284–289
“Super PEEP”
that which produces minimal shunt
Kirby RR, Downs JB, Civetta JM et al. High level positive end expiratory
pressure (PEEP) in acute respiratory insufficiency. Chest 1975; 67:156–163
1981 “Minimal PEEP”
2cm higher than lower inflection point of inflation limb of the
pressure volume curve
Lemaire F, Harf A, Simonneau G et al [Gas exchange, static
pressure volume curve and positive-pressure ventilation at the end of
expiration. Study of 16 cases of acute respiratory insufficiency in adults].
Ann Anesthesiol Fr 1981;22:435–441
PV Curve
Radford EP (1957) Recent studies of the mechanical properties of mammalian lungs. In: Remington
JW (ed) Tissue elasticity American Physiological Society Washington, pp 177–190
VILI
PIP=14, PEEP=0
PIP= 45, PEEP=10
Webb & Tierney ARRD 1974;110;556
PIP= 45, PEEP = 0
Other therapies
1979 “ECMO”:
NIH trial 90% mortality in both groups. High volumes and
pressures
Zapol WM, Snider MT, Hill JD et al. Extracorporeal membrane oxygenation
in severe acute respiratory failure. A randomized prospective study. JAMA
1979;242:2193–2196
1980’s “ECO2R” (Extracorporeal CO2 removal)
Concept of “lung rest” Normal gas exchange targets
Unacceptable complications especially bleeding
Gattinoni L, Agostoni A, Pesenti A et al. Treatment of acute respiratory
failure with low-frequency positive pressure ventilation and extracorporeal
removal of CO2. Lancet 1980;II:292–294
Gattinoni L, Pesenti A, Mascheroni D et al. Low-frequency positive-pressure
ventilation with extracorporeal CO2 removal in severe acute respiratory
failure. JAMA 1986; 256:881–886
Concepts of ARDS in 1980’s
Lungs homogeneous, heavy and stiff
Normalise pCO2 by use of high pressures and volumes
Use of PEEP to normalise pO2
Barotrauma = “complication”
 Major concerns were haemodynamic impairments caused by
PEEP
“Baby Lung”
Quantitative assessment of
CT images in ARDS.
amount of normally aerated
tissue = 5-6 yr old child
Gattinoni L, Pesenti A, The concept of the “baby lung”.
Intensive Care Med; 2005:31:776-784
“Baby Lung”
Respiratory compliance correlates with amount of
normally aerated tissue
Gattinoni L, Pesenti A, Baglioni S et al. Inflammatory pulmonary edema and positive end-expiratory
pressure: correlations between imaging and physiologic studies. 1988; J Thorac Imaging 3:59–64
“Sponge Lung”
Assumes lung oedema in ARDS is
evenly distributed throughout the
lung from sternum to vertebrae.
(not gravitationally dependent).
Gas in dependent regions is
squeezed out by superimposed
pressure including the weight of
the heart
Bone RC The ARDS lung. New insights from computed
tomography. JAMA 1993; 269:2134–2135
Gattinoni L, Pesenti A, The concept of the “baby lung”.
Intensive Care Med; 2005:31:776-784
Superimposed pressure
Opening
Pressure
Inflated
0
Small Airway
Collapse
10-20cmH2O
Alveolar Collapse
(Reabsorption)
40-60cmH2O
Consolidation
(modified from Gattinoni)

“Permissive hypercapnia”
1990 Low tidal volumes to rest lung; CO2 levels allowed
to permissively rise
Changed the goals of ventilation
Hickling KG, Henderson SJ, Jackson R. Low mortality associated with low volume pressure limited
ventilation with permissive hypercapnia in severe adult respiratory distress syndrome. Intensive
Care Med 1990; 16:372–377
Permissive hypercapnia
Late ’90’s: clinical trials of low tidal volume ventilation
Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes compared with traditional
tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000;342:1301–1308.
861 patients
Amato MB, Barbas CS, Medeiros DM, Magaldi RB, Schettino GP, Lo-Physirenzi-Filho G, Kairalla RA, Deheinzelin D, Munoz C,
Oliveira R, et al. Effect of a protective-ventilation strategy on mortality in the acute respiratory distress syndrome. N Engl J Med
1998;338:347–354.
63 patients
Stewart TE, Meade MO, Cook DJ, Granton JT, Hodder RV, Lapinsky SE,Mazer CD, McLean RF, Rogovein TS, Schouten BD, et
al. Evaluation of a ventilation strategy to prevent barotrauma in patients at high risk for acute respiratory distress syndrome. N Engl J
Med 1998;338:355–361.
120 patients
Brochard L, Roudot-Thoraval F, Roupie E, Delclaux C, Chastre J, Fernandez-Mondejar E, Clementi E, Mancebo J, Factor P,
Matamis D, et al. Tidal volume reduction for prevention of ventilator-induced lung injury in acute respiratory distress syndrome.
Multicenter Trial Group on Tidal Volume Reduction in ARDS. Am J Respir Crit Care Med 1998;158:1831–1838
116 patients
Brower RG, Shanholtz CB, Fessler HE, Shade DM, White P Jr, Wiener CM, Teeter JG, Doddo JM, Almog Y, Piantadosi S.
Prospective, randomized, controlled clinical trial comparing traditional versus reduced tidal volume ventilation in acute respiratory
distress syndrome patients. Crit Care Med 1999;27:1492–1498.
52 patients
Confusion and controversy!
Eichacker PQ,. Gerstenberger EP, Banks SM, Cui X, Natanson C. Meta-analysis of acute lung
injury and acute respiratory distress syndrome trials testing low tidal volumes. Am J Respir Crit
Care Med Vol 166. pp 1510–1514, 2002
Lung recruitment in ARDS
68 patients with ARDS:
Highly variable % potentially recruitable lung 13% ±11%
% potentially recruitable correlated with % lung maintained after
application of PEEP
Higher % potentially recruitable lung correlated with:
Lung weight
PaO2/FIO2 ratio
Compliance
Dead space
Mortality
Gattinoni L, Caironi P, Cressoni M, et al. Lung recruitment in patients with the acute respiratory
distress syndrome. N Engl J Med 2006;354:1775-86.
Gattinoni L, Caironi P, Cressoni M, et al. Lung recruitment in patients with the acute respiratory
distress syndrome. N Engl J Med 2006;354:1775-86.
Gattinoni L, Caironi P, Cressoni M, et al. Lung recruitment in patients with the acute respiratory
distress syndrome. N Engl J Med 2006;354:1775-86.
Mortality relates to recruitable lung
Gattinoni L, Caironi P, Cressoni M, et al. Lung recruitment in patients with the acute respiratory
distress syndrome. N Engl J Med 2006;354:1775-86.
Lung recruitment in ARDS
?
Gattinoni L Am J Respir Crit Care Med 2001; 164:1701–1711
Over-stretch = “Volutrauma”
Ventilation induced lung
injury (VILI)
Epithelial and endothelial
cells are anchored to the
lung “skeleton”
Elastin fibres
Bunched up collagen fibres
Gattinoni L, Pesenti A, The concept of the “baby lung”. Intensive Care Med; 2005:31:776-784
Stress and strain
Stress = K (Youngs module of material) x Strain
Stress = PL (transpulmonary pressure)
Strain = Vt (Δ Lung Vol) / “baby lung” (volume at ZEEP)
K
= E spec (Specific lung elastance)
Hence:
E spec = PL x Baby Lung / Vt
E spec =
Transpulmonary Pressure at which the EELV doubles
(~12-13cm normally)
Gattanoni’s hypothesis...
If…
E spec
is constant within narrow limits in ARDS
Then…
An estimate of stress and strain can be made by knowing
either size of “baby lung”, or PL
(Neither are measured routinely in ICU)
“Volutrauma”:
Volume–dependent elastance E2
Volume
Non-linear portion; volume
dependent compliance (E2)
Paw = Airway pressure
E1 = volumeindependent respiratory
elastance
Linear portion; constant compliance;
independent of volume (E1)
Pressure
E2 = Volume-dependent
component of elastance
VT = tidal volume
Po = static recoil
pressure at endexpiration PEEP (tot)
Bersten AD. Measurement of overinflation by multiple linear regression analysis in patients with
acute lung injury. Eur Respir J 1998; 12: 526–532.
“Volutrauma”:
= safe zone
= dangerous
overstretched zone
VEI = End expiratory volume
above resting volume
Bersten AD. Measurement of overinflation by multiple linear regression analysis in patients with
acute lung injury. Eur Respir J 1998; 12: 526–532.
“Volutrauma”:
= safe zone
= dangerous
overstretched zone
%E2 was >30% in 50% of
data where Pel <30 cm!
Pel,dyn =Dynamic elastic airway pressure
Bersten AD. Measurement of overinflation by multiple linear regression analysis in patients with
acute lung injury. Eur Respir J 1998; 12: 526–532.
Airway Pressure-time curves
During inspiration, if:
a =the slope of the P-t relation at t = 1 s
c = the pressure at t = 0.
b = dimensionless number  shape of the P-t curve
b <1, P-t curve is convex; ↑ compliance
b >1 P-t curve is convex; ↓ compliance
b =1 P-t curve is straight; ↔compliance
Ranieri VM, Zhang H, Mascia L, et al. Pressure–time curve predicts minimally injurious ventilatory
strategy in an isolated rat lung model. Anesthesiology 2000; 93:1320–8
Airway Pressure-time curves
Ranieri VM, Zhang H, Mascia L, et al. Pressure–time curve predicts minimally injurious ventilatory
strategy in an isolated rat lung model. Anesthesiology 2000; 93:1320–8
Hypothetical model of Pplateau vs Vt
~based on meta analysis of 5 trials of low volume
ventilation
Eichacker PQ,. Gerstenberger EP, Banks SM, Cui X, Natanson C. Meta-analysis of acute lung
injury and acute respiratory distress syndrome trials testing low tidal volumes. Am J Respir Crit
Care Med Vol 166. pp 1510–1514, 2002
Under-stretch = “Atelectrauma”
Condom model demonstrating
intrapulmonary stresses
“Atelectasis” as modelled by
applying negative pressure to a
condom surrounded by an
“alveolar pressure” of 20 cmH2O
Mead J, Takishima T, Leith D. Stress distribution in lungs: a model of pulmonary elasticity. J Appl
Physiol 1970; 28:596-608
“Atelectrauma”
Shear forces in the zone of lung
opening, caused by stretching of
densely distributed alveolar
membranes, obliquely attached
to bronchiolar basal membranes
Jonson B. Elastic pressure-volume curves in acute lung injury and acute respiratory distress
syndrome Intensive Care Med 31:205–212, 2005, with permission from:
Jonson B (1982) In: Prakash O (ed) Applied physiology in clinical respiratory care. Nijhoff, The
Hague, pp 123– 139
Atelectasis = Stress
Mead and colleagues
have postulated that:
Peff =-PL (V/V0)2/3
Where PL = Palv - Ppl
PL = transpulmonary pressure,
Palv = alveolar pressure,
Ppl = pleural pressure
V = Inflated volume,
V0 = collapsed volume
Consider inflating a partially
collapsed lung to PL=30cmH2O.
Let the volume of the degassed region be
1/10 of its final inflated volume.
PL is therefore amplified by 102/3
Thus the initial pressure tending to
expand the atelectatic region is:
30 x 102/3 = 140 cm H2O
!!
Mead J, Takishima T, Leith D. Stress distribution in lungs: a model of pulmonary elasticity. J Appl
Physiol 1970; 28:596-608
Alveolar wall stress in 2-D condom model
Wall areas stressed next to regions of
hyperiflation and collapse
Surfactant depletion in pig model
Recruitment occurs throughout static inflation
Courtesy of Gary Nieman, Syracuse NY
Deflation /re-inflation PV curves
Saline-lavaged rabbits
Solid lines show re-inflation plots
after deflation from 30 cm H2O
airway pressure to different endexpiratory pressures.
Little hysteresis with deflation to 15
cm H2O,  little derecruitment
above that pressure.
Hickling KG: Reinterpreting the pressure-volume curve in patients with acute respiratory distress
syndrome. Curr Opin Crit Care 2002, 8:32–38 Published with permission from:
Rimensberger PC, Cox PN, Frndova H, et al.: The open lung during small tidal volume ventilation:
Concepts of recruitment and “optimal” positive end expiratory pressure. Crit Care Med 1999,
27:1946–1952.
Stored curves
Date &
time
P/-V Tool 2
Actual Settings
5
35
Current
settings
Total time
To open
setting window
Start/Stop button
Cursor buttons
10
3
1
23
P-start
cmH2O
P-top
cmH2O
end PEEP
cmH2O
Ramp speed
cmH2O/s
T-pause
s
T-total
s
V
2000-/12-12
15:33:34
3.78
30

492
Xxxxxxxxx
erttrert
Xxxxxxxxx
erttrert 
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erttrert

15
Inspiratory
limb (green)
Expiratory
limb (yellow)
Settings
Start/Stop

Cursor 1
Cursor 2
To open Plot
window
To select and
view stored
curves
Assist lines
1/5
P
Plot
Cursor 1
Cursor 2
C cursor
Insp. limb
100 / 5
900 / 22
37.5
Exp. limb
155 / 5
1120 / 22
36.5
History
Close
Cursor 1 for
both limbs
Cursor 2 for
both limbs
Compliances for
both red lines
Data of insp. limb
Data of Exp. limb
Pressure
Galileo datalogger: Inflation deflation method
Flow
Hickling KG. Using the expiratory pressure volume curve- VILI at the bedside. 25th Symposium of
Intensive Care and Emergency Medicine, March 21-25, 2005
Volume
Galileo datalogger: Inflation deflation method
Pressure
Hickling KG. Using the expiratory pressure volume curve- VILI at the bedside. 25th Symposium of
Intensive Care and Emergency Medicine, March 21-25, 2005
Models of threshold opening and closing pressures
Inspiratory tidal PV plots
Incremental = black symbols
Decremental = open symbols
TOP = 0–40, TCP = 0–4.
At each PEEP level the volume at
equivalent pressures and the mean
tidal PV slope are greater during
decremental PEEP.
Hickling KG: Reinterpreting the pressure-volume curve in patients with acute respiratory distress
syndrome. Curr Opin Crit Care 2002, 8:32–38 Redrawn from:
Hickling KG: Best compliance during a decremental, but not incremental, positive end-expiratory
pressure trial is related to open-lung positive end expiratory pressure: a mathematical model of
acute respiratory distress syndrome lungs. Am J Respir Crit Care Med 2001, 163:69–78
Models of threshold opening and closing pressures
The mean tidal PV slope
plotted against PEEP
Incremental PEEP = black symbols
Decremental PEEP = open symbols
Max PV slope with:
Incremental PEEP is at 20 cm H2O
Decremental PEEP is at 16 cm H2O
Hickling KG: Best compliance during a decremental, but not incremental, positive end-expiratory
pressure trial is related to open-lung positive end expiratory pressure: a mathematical model of
acute respiratory distress syndrome lungs. Am J Respir Crit Care Med 2001, 163:69–78
Models of threshold opening and closing pressures
Flow pressure curves
Simulated data
Max change in slope
corresponds to beginning of
de-recruitment
But very difficult to judge
slope changes by eye
especially when very steep
Hence a flow pressure curve
can indicate the max rate of
de-recruitment
Hickling KG. Using the expiratory pressure volume curve- VILI at the bedside. 25th Symposium of
Intensive Care and Emergency Medicine, Brussels, Belgium, March 21-25, 2005
Derecruitment
Pressure
Galileo datalogger: Flow-Pressure
Flow
Hickling KG. Using the expiratory pressure volume curve- VILI at the bedside. 25th Symposium of
Intensive Care and Emergency Medicine, March 21-25, 2005
Models of threshold opening and closing pressures
(A) Airway pressure vs volume /recruited volume determined from CT
(open circles and dotted line; expressed as percent of maximum volume) and
recruitment (black circles and solid line; expressed as percent maximum recruitment)
(B) Frequency distribution of estimated opening pressures.
Note that recruited volume continues throughout inflation, up to 50 cm H2O pressure.
Hickling KG: Reinterpreting the pressure-volume curve in patients with acute respiratory distress
syndrome. Curr Opin Crit Care 2002, 8:32–38 Redrawn from:
Crotti S, Mascheroni D, Caironi P, et al.: Recruitment and de-recruitment during acute respiratory
failure: A clinical study. Am J Respir Crit Care Med 2001, 164:131–140.
Real-time acquisition of threshold opening and
closing pressures
Recruitment is described by Threshold Opening Pressure (TOP)
Number of Units
Derecruitment is described by Threshold Closing Pressure (TCP)
Skewed normal distribution
Unique to a patient and condition
TCP
TOP
Pressure
Chase J, Yuta T, Shaw G, Horn B, Hann C A minimal model of mechanically ventilated lung
mechanics to optimise ventilation therapy in the treatment of ARDS in critical care. Proceedings of
the 12th International Conference on Bioengineering, Singapore 2005
PEEP
TCP
Unique distributions for different
levels of PEEP are found
TOP
Chase J, Yuta T, Shaw G, Horn B, Hann C A minimal model of mechanically ventilated lung
mechanics to optimise ventilation therapy in the treatment of ARDS in critical care. Proceedings of
the 12th International Conference on Bioengineering, Singapore 2005
Optimisation of ventilation
Parameter identification = patient specific model
Simulation to determine effect of settings on PV curve
Optimise ventilator settings as desired
Chase J, Yuta T, Shaw G, Horn B, Hann C A minimal model of mechanically ventilated lung
mechanics to optimise ventilation therapy in the treatment of ARDS in critical care. Proceedings of
the 12th International Conference on Bioengineering, Singapore 2005
‘Strengths’ in using this approach…..
Real time assessment of recruitment status which is
dependent on PEEP, ventilation strategy, and disease
Readily identifies TCP distributions
 optimization of PEEP
Provides opportunity to simulate a ventilation strategy
before application.
TOP distribution characteristics
Prediction of “overstretch”. E.g. Δ recruitment < % max rate
 ? Correlated with E2% or CT scan
Limitations…
Although flow resistive forces through the endotracheal
tube are accounted for, the model assumes the pressure
at the carina will reflect what is happening to alveolar
units.
Unforeseen resistive changes (eg major bronchial airway
obstruction) could therefore lead to incorrect inferences
about recruitment status
Needs to be clinically validated
A model for teaching and research
Mechanical lung model with 6 units of variable compliance
(weighted) bellows and variable insp /exp resistances (taps)
Mimicking nature
5cm PEEP
15cm PEEP
Sponsored by NZ$8000 grant from Hamilton Medical, Switzerland
Mimicking nature
Normal PV loop
PV loop of “Asthma”
PV loops at different
levels of PEEP
(Note tidal volume is
referenced to zero
volume)
Chase JG, Yuta T, Shaw GM, Mulligan K, Hann CE. A novel mechanical lung model of pulmonary
diseases to assist with teaching and research (in review )
Mind what
you have
learned. Save
you it can.
Acknowledgements
Toshi Yuta
Kerry Mulligan
Assoc. Prof.
Geoff Chase
Dr Chris Hann
Beverley Horn