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4_+HFOV+for+LPV++and+OLC

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					High frequency oscillatory ventilation (HFOV):
How does it work and how to integrate it in the concept of
lung protective ventilation and of the open lung?


 1) What is HFOV?
    Specific characteristics of HFOV


 2) Basic mechanisms of gas exchange during HFOV
     - How to set MAP when switching from CMV
     - What are optimal settings and how to monitor
     - Basic concepts of lung recruitment during HFO


  3) How does HFOV fit in actual concepts of lung
     protection?
    /      /
HFO = HFJV = HFPPV   Humidifed Bias Flow




                               Patient
“Elimination” of tidal ventilation




                Slutsky AS ARRD 1988;138:175-83
Gas transport
mechanisms
during HFOV




                Bouchut JC et al. Anesthesiology 2004; 100:1007-12
   Pressure transmission CMV / HFOV :




                                      Tracheal
                                      pressure




                           Endinspiration        Endexpiration

Gerstman et al
      CMV                HFO
  PEEP 10, Vt 6          CDP 16




CMV               CMV
      HFOV              HFOV
HFO
Lung volumes




The Paw is used to
inflate the lung and
optimize the alveolar
surface area for gas
exchange.
 Paw = Lung Volume
Oxygenation
Oxygenation is
primarily controlled by
the mean airway
pressure (Paw) and
the FiO2 for “Diffuse
Alveolar Disease”.


The Paw is used to
inflate the lung and
optimize the alveolar
surface area for gas
exchange.
 Paw = Lung Volume
From the lab to the bedside: The principal concepts




Adapted from Suzuki H Acta Pediatr Japan 1992; 34:494-500
Lung Recruitment Using Oxygenation during Open
Lung High-Frequency Ventilation in Preterm Infants




                                                                   Adapted from Suzuki H
                                                                   Acta Pediatr Japan 1992;
                                                                   34:494-500




De Jaegere Ann et al.   Am J Respir Crit Care Med 2006: 174; 639–645
 Lung Recruitment Using Oxygenation during Open
 Lung High-Frequency Ventilation in Preterm Infants




                                                                       Adapted from Suzuki H
                                                                       Acta Pediatr Japan 1992;
                                                                       34:494-500




De Jaegere Ann et al.   Am J Respir Crit Care Med 2006: 174; 639–645
Lung Recruitment Using Oxygenation during Open
Lung High-Frequency Ventilation in Preterm Infants

           before surfactant                        after surfactant




De Jaegere Ann et al.   AJRCCM 2006: 174; 639–645
      The Open Lung Approach with HFOV
(Lung-Lavaged Rabbits) McCulloch, Forkert, Froese ARRD 137:1185-1192,1988


                                      Percentage airways with lesions
                                     100    4+
                                            Epithelial
                                            injury
                                      80
                                            Hyaline
                                            Membranes
                                      60

                                      40

                                      20

                                       0
                                           HFO-Hi HFO-Lo     CMV
Ventilation
Ventilation is primarily determined by the stroke
volume (Delta-P) or the frequency of the ventilator.


  Alveolar ventilation during CMV is defined as:
                       F x Vt
  Alveolar Ventilation during HFV is defined as:
                       F x Vt 2

Therefore, changes in volume delivery (as a function of
pressure-amplitude, frequency, or % inspiratory time)
have the most significant affect on CO2 elimination
Frequency controls the time allowed
(distance) for the piston to move.

Therefore, the lower the frequency, the
greater the volume displaced, and the higher
the frequency, the smaller the volume
displaced.
        Theory of operation
Oxygenation and CO2 elimination have been
demonstrated to be decoupled with HFOV
5 Hz versus 15 Hz: does it matter?




            Meyer J et al. PediatrRes 2006; 60: 401–406
5 Hz versus 15 Hz: does it matter?




            Meyer J et al. PediatrRes 2006; 60: 401–406
   Mean airway pressure, amplitude and frequency

MAP (CDP):   recruits alveoli/airways and maintains alveolar volume
              it is closely related to lung volumes and oxygenation



Amplitude:   there is a close relationship between pressure amplitude
             and tidal volume

             tidal volume depends on:
             1) the volume displaced by the piston or diaphragm,
             2) the resistance of the airways,
             3) the compliance of the ventilator circuit, and
             4) the patient’s lung mechanics

             therefore: search for visible chest vibrations

             change amplitude to control ventilation (PaCO2)
Bouchut JC et al. Anesthesiology 2004; 100:1007-12
How to set initial MAP when switching to HFOV



100                                                     100
 90                                                           90
 80                                                           80
 70                                                           70




                                                volume (ml)
 60                                                           60
 50                                                           50
 40                                                           40
 30                                                           30
 20                                                           20
 10                                                           10
 0                                                            0
      0   5   10     15   20    25    30   35                      0   5   10     15   20    25    30   35
                   pressure (cmH2O)                                             pressure (cmH2O)
Recruitment concept during HFO

                                                            And
                                                            reduce
                                                            FiO2!




Adapted from Suzuki H Acta Pediatr Japan 1992; 34:494-500
                                 A recruitment procedure in iRDS
Volume above FRC by respitrace



                                             Drop in SO2




                                        10
                                  5     10       15        20    25   30   35
                                              Airway pressures
 Recruit first the lung and then keep open the
 lung at the lowest pressure necessary!


                                      Some bedside rules:

                                      1) Lower FiO2 before CDP (=MAP)

                                      2) Always try to define lung
                                      closing pressure to assure that
                                      you will use lowest pressures
                                      required
                                      3) Try to work always the highest
                                      frequency possible - increase the
                                      amplitude in a first step to correct
                                      for high pCO2
                                      4) If you’re “lost”
Adapted from Suzuki H                    - always decrease CDP first!
Acta Pediatr Japan 1992; 34:494-500
The clinical experience:

     HFO vs CMV
Elective HFOV vs CMV: Death or CLD at 36 w GA or discharge
                         All trials




               Favors HFO         Favors CMV

                    With volume recruitment
Cumulative Meta-Analysis: Incidence of CLD




           Bollen et al. AJRCCM 2003; 168: 1150–1155
Elective HFOV
versus CMV

CLD at 36-37 wks
PMA or discharge




Henderson-Smart DJ
Cochrane Database of Systematic
Reviews 2007, Issue 3. Art. No.:
CD000104. DOI:
10.1002/14651858.CD000104.pub2.
Elective HFOV
versus CMV

CLD at 36-37 wks
PMA or discharge




Henderson-Smart DJ
Cochrane Database of Systematic
                                   35% 39%      NNT 25
Reviews 2007, Issue 3. Art. No.:
CD000104. DOI:
10.1002/14651858.CD000104.pub2.
Elective HFOV
versus CMV

Combined Outcome:
Death or CLD at 36-37
wks PMA or discharge




Henderson-Smart DJ
Cochrane Database of Systematic
Reviews 2007, Issue 3. Art. No.:
CD000104. DOI:
10.1002/14651858.CD000104.pub2.
HFOV compared with CMV for Diffuse Alveolar
Disease or Air Leak in Pediatrics
Arnold et al. Crit Care Med 1994;22




58 Children (29 CMV, 29 HFO)


Protocol:          MAP was set 4-8 cm H2O > CMV-MAP
                   Decrease FiO2 before MAP

Results:
No difference in Death, Length of Vent., Air Leak.
Significant improvement in oxygenation with HFO over time.*
Less need for O2 at 30 days with HFO.*                        * p<0.05


HFOV is safe and improves oxygenation as well as outcome
                                              MOAT II: Overall Survival
                                           HFOV        CV
                                N          75          73
                                P/F        114 (37)    111 (42)
                           1

                          0.9                                     30d p=0.057
                                                                  90d p=0.078
Proportion of Survivors



                          0.8

                          0.7

                          0.6                                              HFOV

                          0.5

                          0.4
                                                                           CV
                          0.3

                          0.2
                                0     10     20 30 40 50 60 70 80               90
                                            Days Aft e r Randomiz ation

                                Derdak S Am J Respir Crit Care Med 2002; 166:801–808
Predictors of Outcome


1) Oxygenation Index Response
         MAP x FiO2 x 100
   (OI =                  )
              PaO2


2) Entry Indicators of Compliance
   (Peak Inspiratory Pressure)
MOAT II: Predictors of Outcome




   Derdak S Am J Respir Crit Care Med 2002; 166:801–808
       MOAT II: Survival - PIP  38 cmH20 (post-hoc)
                           1
                                                          30d p=0.019
                          0.9                             90d p=0.026
Proportion of Survivors




                          0.8

                          0.7
                                                                   HFOV
                          0.6

                          0.5
                                                                        CV
                          0.4

                          0.3

                          0.2
                                0   10    20 30 40 50 60 70 80           90 HFV-Meeting
                                         Days Aft e r Randomiz ation         2001
Early (< 24 h) versus late (>24 hours)
   intervention in pediatric ARDS




            Fedora M Bratisl Lek Listy 2000; 101: 8-13
Metha S et al. Crit Care Med 2001; 29:1360 –1369
Time concepts for lung protection




  Katzenstein AL et al. Surgical pathology of non-neoplastic lung disease.
  Saunders, Philadelphia, 1982



Neither a ventilation strategy nor a
mode can repair the injured lungs
  First Intention HFO with early lung volume recruitment

Demographic data and severity of lung disease

all patients                                              HFO (n=32)            CMV (n=39) p - value
  Birth weight (g)                                         981 ± 242              965 ± 254              n.s.*
  Estimated gestational age (weeks)                         27.7 ± 2.0            27.7 ± 1.8             n.s.*
  Antenatal steroid treatment, no (%)                         13 (41)               14 (36)             n.s.#
  APGAR score < 4 at 1 min, no (%)                            13 (44)               17 (44)             n.s.#
  APGAR score < 6 at 5 min, no (%)                             7 (22)                5 (13)             n.s.#
  Degree of HMD (1 - 4) on CXR                               2.9 ± 0.8              3 ± 0.9              n.s.*
  aA-ratio (first blood gas analysis)                      0.16 ± 0.09           0.20 ± 0.16             n.s.*

Values are given as mean ± SD, or as the number (percentage) of patients; * unpaired t-test; ** Chi-square;
# Fisher's exact

                                                      Rimensberger PC et al. Pediatrics 2000; 105:1202-1208
         First Intention HFO with early lung volume
                          recruitment
Observational study, historical cohort: 71 premature infants with RDS at birth


         Mean airway pressure                                           PaO2/FiO2 ratio
30                                                    300

25                                                    250
                                                                                               HFO
20                                                    200

15                                     HFO            150

10                                                    100
                                                                                               CMV

5                                      CMV             50


0                                                       0

     0   2   4   6   8   10 12 14 16 18 20 22 24            0   2   4   6   8   10 12 14 16 18 20 22 24
                          time (h)                                               time (h)


                                             Rimensberger PC et al. Pediatrics 2000; 105:1202-1208
 First Intention HFO with early lung volume
                 recruitment

              days of ventilation                                 oxygen dependency
100                                                100
                                     • HFO                                                 • HFO
                                     • CMV                                                 • CMV
80                                                  80


60                                                  60


40                             p = 0.0004           40                             P < 0.0001


20                                                  20
                                                                                                n=3

 0                                                   0
     0   20   40   60     80   100   120    140          0   20   40   60     80   100 120 140
                        days                                                days

                                            Rimensberger PC et al. Pediatrics 2000; 105:1202-1208
First Intention HFO with early lung volume
                recruitment

Survival and CLD Morbidity

all patients                                               HFO (n=32) CMV (n=39)                      p - value

survivors to 30 days                                       HFO (n=27) CMV (n=35)
 Ventilation (days)                                          5 (3-6)   14 (6-23)  0.0004 *
 Oxygen dependency (days)                                   12 (4-17)  51 (20-60) <0.0001 *
 Oxygen at 28 d, no (%)                                      6 (22)     22 (63)    0.002 #

survivors to 36 weeks PCA          HFO (n=27) CMV (n=34)
 CLD; Oxygen > 36 weeks PCA, no (%) 0 (0)      12 (35)                                                0.0006 #

Values are given as the median (95% CI) or the number (percentage) of patients; * Mantel-Cox log-rank; # Fisher's exact




                                           Rimensberger PC et al. Pediatrics 2000; 105:1202-1208
Recruitment bei der Hyalinen Membranenkrankheit (RDS)
      28 wks GA, 8 hours after birth, on HFOV, no surfactant received


                                 MAP 26 cmH2O




MAP 12 cmH2O, Amplitude 40, FiO2 0.8        MAP 16 cmH2O, Amplitude 28, FiO2 0.21




                             08’10                                                  08’25
Recruitment during both, HFO and CMV, follows similar
 concepts when using small tidal volume ventilation


        100                                                  100
              90                                             90
              80                                             80
                       HFO after                                       CMV after
              70                                             70
                       recruitment                                     recruitment
volume (ml)




              60                                             60
              50                                             50
              40                                             40
              30                                             30
              20                                             20
              10                                             10
              0                                               0
                   0   5   10     15   20    25    30   35         0    5    10     15   20    25    30   35
                                pressure (cmH2O)                                  pressure (cmH2O)


                                            Rimensberger PC Intensive Care Med 2000; 26; 745-755
1. Similar effect on oxygenation



                                   2. Similar protective effect on histology



                                    Rimensberger PC Intensive Care Med 2000; 26; 745-755
Lung recruitment (open lung concept) during both,
CMV and HFO reduces VILI in newborn piglets



  Lavaged   PPVOLC   HFOOLC




                     PPVCON




                                 Van Kaam A Ped Research 2003
Lung recruitment (open lung concept) during both,
CMV and HFO reduces VILI in newborn piglets
PPVcon                   PPVOLC




HVOOLC                  Controls




                            Van Kaam A Ped Research 2003
OLV improves gas exchange and attenuates secondary
lung injury in a piglet model of meconium aspiration

pO2




pCO2




                       Van Kaam A et al. Crit Care Med 2004; 32:443–449
OLC in a neonatal piglet lavage model




                             Van Kaam A   Biol Neonate 2003;83:273-80
Recruitment and the Open Lung Concept is all
about avoiding collapse and overdistention
Recruitment and the Open Lung Concept
  during HFOV is all about keeping the
  lung open at the least pressure cost
    The difficulty to place the ventilatory cycle within the
    safe window during CMV when compared to HFOV
Volume (l)




                                    ALI
                                (surfactant
                               depleted lung)




                                     severe
                                     (A)RDS




                 Airway pressure (cmH2O)

                                                Adapted from Suzuki H
                                                Acta Pediatr Japan 1992; 34:494-500
Hickling KG et al. AJRCCM 2001; 163:69-78
                                            “The beauty of simplicity”

                                            HFOV: Turn 1 knob …
                                              and observe 2 parameters
                                                          (O2, CO2)




CMV: chose your allowable Vt

Turn then 1 (or 2 knobs) …
    and observe 3 parameters
           (O2, CO2, Cdyn)
and remember to adapt Ti and Te
  Time constant: T = Crs x Rrs              Adapted from Suzuki H
                                            Acta Pediatr Japan 1992; 34:494-500

				
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