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
Gerstman et al
Endexpiration
CMV
HFO
PEEP 10, Vt 6
CDP 16
CMV
HFOV
CMV
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
De Jaegere Ann et al.
AJRCCM 2006: 174; 639–645
after surfactant
The Open Lung Approach with HFOV
(Lung-Lavaged Rabbits) McCulloch, Forkert, Froese ARRD 137:1185-1192,1988
Percentage airways with lesions
100
80
60
4+
Epithelial
injury
Hyaline
Membranes
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
90
90
80
80
70
70
volume (ml)
100
60
50
40
30
60
50
40
30
20
20
10
10
0
0
0
5
10
15
20
25
pressure (cmH2O)
30
35
0
5
10
15
20
25
pressure (cmH2O)
30
35
Recruitment concept during HFO
And
reduce
FiO2!
Adapted from Suzuki H Acta Pediatr Japan 1992; 34:494-500
Volume above FRC by respitrace
A recruitment procedure in iRDS
Drop in SO2
5
10
10
15
20
Airway pressures
25
30
35
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
Adapted from Suzuki H
Acta Pediatr Japan 1992; 34:494-500
4) If you’re “lost”
- always decrease CDP first!
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
Reviews 2007, Issue 3. Art. No.:
CD000104. DOI:
10.1002/14651858.CD000104.pub2.
35% 39%

NNT 25
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.*
HFOV is safe and improves oxygenation as well as outcome
* p<0.05
MOAT II: Overall Survival
N
P/F
HFOV
CV
75
114 (37)
73
111 (42)
1
30d p=0.057
90d p=0.078
Proportion of Survivors
0.9
0.8
0.7
HFOV
0.6
0.5
0.4
CV
0.3
0.2
0
10
20 30 40 50 60 70 80
Days Af te r Random izat ion
90
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
90d p=0.026
Proportion of Survivors
0.9
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
Days Af te r Random izat ion
90 HFV-Meeting
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.#
2.9 ± 0.8
3 ± 0.9
n.s.*
0.16 ± 0.09
0.20 ± 0.16
n.s.*
Degree of HMD (1 - 4) on CXR
aA-ratio (first blood gas analysis)
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
20
200
HFO
15
HFO
150
CMV
100
10
CMV
5
50
0
0
0
2
4
6
8
10 12 14 16 18 20 22 24
time (h)
0
2
4
6
8
10 12 14 16 18 20 22 24
time (h)
Rimensberger PC et al. Pediatrics 2000; 105:1202-1208
First Intention HFO with early lung volume
recruitment
days of ventilation
100
oxygen dependency
• HFO
• CMV
80
60
100
• HFO
• CMV
80
60
p = 0.0004
40
P < 0.0001
40
20
20
n=3
0
0
0
20
40
60
80
days
100
120
140
0
20
40
60
80
days
100 120 140
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)
survivors to 30 days
Ventilation (days)
Oxygen dependency (days)
Oxygen at 28 d, no (%)
HFO (n=27) CMV (n=35)
5 (3-6)
14 (6-23)
0.0004 *
12 (4-17)
51 (20-60) <0.0001 *
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)
p - value
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
08’10
MAP 16 cmH2O, Amplitude 28, FiO2 0.21
08’25
Recruitment during both, HFO and CMV, follows similar
concepts when using small tidal volume ventilation
100
100
90
90
80
70
volume (ml)
80
HFO after
recruitment
60
60
50
50
40
40
30
30
20
20
10
10
0
0
0
5
10
15
CMV after
recruitment
70
20
25
pressure (cmH2O)
30
35
0
5
10
15
20
25
30
35
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
Volume (l)
The difficulty to place the ventilatory cycle within the
safe window during CMV when compared to HFOV
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