Mechanical ventilation versus CPAP
-what are the pros and cons?
Anne Greenough
Professor of Neonatology & Clinical Respiratory Physiology
Division of Asthma, Allergy and Lung Biology
King’s College, London, School of Medicine
PREDISPOSED INFANT
Immaturity
Family History
RDS
SEVERE LUNG DISEASE
CONTRIBUTARY
FACTORS
Infection
Surfactant
abnormalities
Disturbance of
elastase/protease
PDA/Fluid overload
PIE
HIGH LEVEL OF
RESPIRATORY SUPPORT
Baro/volutrauma
Oxygen Support
Bronchopulmonary dysplasia
Which ventilation strategy?
Strategies to reduce the likelihood of baro/volutrauma:
(i) Avoidance of intubation and mechanical ventilation
- nasal continuous positive airways pressure (nCPAP)
(ii) Respiratory support working synergistically with the
infant’s respiratory efforts
- patient triggered ventilation
(iii) Minimisation of excessive “tidal” volumes
- volume targeted ventilation
- high frequency oscillation
Early nCPAP
•
•
-
Reduced incidence of intubation and mechanical
ventilation
Jacobsen 1993, Poets 1996, Gitterman 1997
Eight centre comparison, the centre with the lowest
occurrence of BPD used CPAP in preference to IPPV
avoided hyperventilation and muscle relaxants
used permissive hypercapnia
one individual supervised ventilatory care
Avery 1987
Nasal CPAP or intubation at birth
(COIN trial)
610 infants 25 to 28 weeks gestation
IPPV
O2 dep 28 days
63%
Days of IPPV
4
O2 dep at 36 weeks
29%
Pneumothorax
3%
CPAP
51%
<0.001
3
<0.001
35%
ns
9%
=0.003
Morley et al NEJM 2008
Early surfactant and extubation to CPAP
versus selective surfactant and IPPV
Meta-analysis of six trials demonstrated CPAP:
Reduced BPD
0.51(0.26-0.99)
Reduced need for IPPV
0.67 (0.57-0.79)
Reduced airleaks
0.52 (0.28,0.96)
Surfactant
1.62 (1.41,1.86)
Stevens et al Cochrane 2007
But early versus selective surfactant reduces airleaks and
BPD/death and improves survival
Nasal trauma
• 20% infants on dual prongs affected
Robertson et al ADC 1996
• 40 infants randomised nasaopharyngeal tube or binasal prong
- similar trauma incidence
Buettiker et al Intens Care Med 2004
• 89 infants randomised to binasal prong or mask
-no significant difference in nasal trauma incidence
- nasal injury (32%) related to CPAP duration
Yong et al ADC 2005
PTV (ACV/SIMV) versus CMV
• Oxygen dependency:
at 28 days 0.93 (0.77 - 1.14)
at 36 weeks 0.91 (0.77 - 1.09)
• Severe IVH:
1.03 (0.75 - 1.43)
• Reduction in ventilation duration:
- 45.2 hours (12.1 - 78.3)
- only when PTV was started in the recovery phase
Greenough et al Cochrane review 2007
Pressure support (PS)
• Infant triggers an inflation which is pressure supported
at a preset level
• The beginning and end of inflation are triggered by the
start and end of inspiration
• Inflation is terminated when the inspiratory flow is
reduced to a certain level
- 15% maximum flow (Draeger Babylog 2000 - PSV)
- 5-25% maximum flow (Bird VIP - termination
sensitivity)
Randomised trial of SIMV versus
SIMV and pressure support (PS)
• 107 infants birthweight 500-1000gms >one week
• PS group SIMV rate reduced by 10bpm and PS
added at 30-50% of the PIP-PEEP
• PIP decreased to PaCO2 and Vt: 3 and 5 ml/kg
• SIMV reduced to keep between 40-65mmHg
Reyes et al Pediatr 2006
Randomised trial SIMV versus
SIMV + PS
all infants
SIMV PS
p
Age at final
extubation (days)
IPPV (days)
IPPV 28 days (%)
O2 at 36wks (%)
O2 (days)
44
34
69
48
72
35
22
47
33
49
.91
.18
.04
.21
.11
700-1000
SIMV PS
p
29
25
53
58
86
24 .366
15 .118
30 .116
38 .142
58 .034
Work of breathing during SIMV
with and without pressure support
20 infants mean gestational age 31 weeks, being
weaned from mechanical ventilation
SIMV
SIMV + PS
p
PTP
141 (93)
112 (85)
<0.001
PaO2
8.6 (2.6)
8.5 (1.8)
0.78
PaCO2
Resp rate
5.9 (1.3)
64 (13)
6.0 (1.6)
0.55
55 (11)
0.001
Patel et al ADC 2009
Volume targeted ventilation
• No significant reduction in death or death and
BPD
• Reduced duration of ventilation 2.39 days
• Reduced pneumothoraces RR 0.23
• Reduced 3-4 ICH RR 0.32
• 4 trials identified – 178 infants
McCallion et al Cochrane database 2005
Volume targeted ventilation
• Volume support – desired volume is selected, the duration of
inflation depends on the time taken for the volume to be delivered
Bird VIP
• Volume limited – pressure support for any inflation is aborted if
the measured volume exceeds the preset upper limit
SLE 5000, Bearcub 750
• Volume guarantee – preset expiratory tidal volume is delivered,
but the preset Ti determines the duration of inflation
Draeger Babylog
• Volume controlled – constant flow during inspiration – the
required volume is delivered over the Ti
Stephanie
Delivery depends on ventilator type
• Draeger positive pressure plateau
• Stephanie pressure increasing till Ti termination
• SLE and VIP Bird inflation terminating when the volume
was delivered
• At the same settings – different MAP delivery
Sharma et al Acta Ped 2006
Impact of VG on CO2 tensions
• Randomised trial of 40 infants 27 weeks
gestation
• SIMV +/-VG 4mls/kg
• In infants > 25weeks VG halved the
incidence of hypocarbia
• Ineffective in infants <26 weeks GA
Cheema et al EHD 2006
Volume controlled vs pressure limited
• Randomised trial - 90 infants BW 600 to 1500gms, GA
24 –32 wks
• Bird VIP, volume controlled (VC) or pressure limited
• Success criteria oxygenation/MAP reached at 23 hrs VC
versus 33 hrs (p=0.15) (BW<1000gms p=0.03)
• No significant differences in other outcomes
Singh et al J Pediatr 2006
• VT 4-6mls/kg
VG level and work of breathing
20 infants mean GA 28 weeks (10 ACV; 10 SIMV)
PTP levels at VG levels of 4, 5 and 6 mls/kg
VG level
ACV
SIMV
0
144 (47)
173 (88)
4
203 (82)
237 (100)
5
168 (59)
180 (78)
6
135 (47)
147 (51)
Patel et al Pediatr 2009
Prophylactic HFO
13 published prophylactic trials ( < 12 hours)
• BPD at 36 weeks PMA or discharge in survivors
RR 0.88 (0.79 – 0.99)
• Death by 36 weeks PCA
RR 0.98 (0.83 – 1.16)
• Death or BPD at 36 weeks PMA or discharge
RR 0.92 (0.85-1.00)
• Pulmonary airleak
RR 1.14 (1.00-1.29)
• 3-4 IVH
RR 1.11 (0.95-1.1.3)
• PVL
RR 1.10 (0.84-1.44)
UKOS Trial
• Infants between 23 weeks and 28 +6 weeks gestational
age, CMV or HFOV within 60 minutes of birth
n
Died
Survived O2
dependant at 36 weeks
Airleak
Cerebral abnormality
CMV
397
26%
HFO
400
25%
41%
41%
18%
16%
25%
17%
Johnson et al NEJM 2002
Pulmonary function at one year
Means and 95% CI of the differences in the means:
CMV
HFOV (95%CI diff)
Respiratory rate (bpm)
31.2
33.9
(-6.1,0.7)
TGV (mls/kg)
26.9
26.5
(-2.5,3.4)
FRC (mls/kg)
24.1
23.5
(-2.1,3.2)
FRC:TGV
0.90
0.90
(-0.06,0.06)
Resistance (cmH2O/l/s)
33
34
(-8,6)
Thomas et al ARJCCM 2003
Effect of preterm delivery on airway function in first year of life
2
V’maxFRC z-score
1
0
-1
-2
-3
-4
-5
40
50
60
70
80
Crown-heel length (cm)
90
Worsening V’maxFRC in infants with BPD
• 36 infants mean birthweight 837 (152) gms and
gestational age 26.8 (1.7) gms
• BW < 1250gms, IPPV>7 days, BPD
• Initial ventilation: IPPV or HFOV in the youngest and
smallest infants
• Evaluated at 6 and 12 months
• Maximum flow at functional residual capacity
(V’maxFRC)
Hofhuis et al AJRCCM 2002
Mechanical ventilation versus CPAP
Current evidence:
• High volume HFO reduces BPD, but whether it
improves long term lung function requires follow-up
of infants entered into RCTs
• Weaning is best by modes supporting every breath
–whether ACV or PSV is better merits testing
• Severe respiratory distress – a trial of rescue HFOV
with long term outcomes is needed
• CPAP as the preferred mode?