2. DEFINITION
Also called continuous distending pressure (CDP)
Maintenance of an increased (positive)
transpulmonary pressure during the inspiratory &
expiratory phase of respiration in a spontaniously
breathing baby.
By which alveoli are kept open which increase
the functional residual capacity(FRC) of the lungs
resulting in better gas exchange.
3. HISTORY
Harrison 1968: described grunting in neonates as
naturally producing end expiratory pressure
Gregory et al, 1971: introduced the clinical use of
distending pressure in neonates.(via endotrachial
tube or a head box)
Kattwinkel reported successful use of nasal prongs in
neonates with RDS.
Reports of significant lower incidence of chronic lung
disease from columbia university that used more
CPAP as compared to north american centre have led
to resurgence of interest in CPAP over the last 15
years.
5. DISADVANTAGES OF
CONVENTIONAL VENTILATION
High pressure- Barotrauma
Tidal volumes- Volutrauma
Atelectotrauma
Inflammation & infection- Biotrauma
CV ruptures the interalveolar septa thus
decrease the surface area of gas
exchange despite increasing lung volume.
6. Effect of Ventilator on Preterm
Lamb Lung
At 0 hour
24 hour after ventilation
Limitations of premature lung
1.Underdeveloped architect to
hold the lung open
2.Thicker and few septa so less SA
for gas exchange
Pinkerton KE, et al J Appl Physiol, 1994
13. PVR Increases at Lung Volumes
Below and Above FRC
PVR
Lung Volume
FRC
HMD MAS
14. CPAP MAGIC
Opens lung at FRC
Keeps it open at minimum constant
pressure least atelecto & barotrauma
Pulmonary arterial pressure are least
hence less V/Q mismatch less pressure
required.
No ET tube- no biotrauma
15. Larger alveolus
r = 1.5
T = 3
P = (2 x 3) / 1.5
P = 4
Smaller alveolus
r = 1
T = 3
P = (2 x 3) / 1
P = 6
CPAP
Law of LaPlace : P = 2T/r
P : pressure T : surface tension r : radius
17. Stretches lung
pleura and upper
airway
CPAP
Prevents collapse
of alveoli with
marginal stability
Stabilizes the
chest wall
Splints open
upper airway
Improves pH
Reduces airway
resistance
Recruitment of
alveoli
PaO2PaCO2
Improves V/Q mismatch and
reduces intrapulmonary shunt
Increased alveolar surface
area for gas exchange
Maintains lung at
FRC
Reduces work of
breathing
Reduces mixed and
central apnea
Reduces
obstructive apnea
Stimulates
stretch receptors
18. INDICATION OF CPAP
COMMON
Respiratory distress syndrome
Apnea of prematurity (specially obstructive apnea)
Post-extubation in preterm VLBW infants
Transient tachypnea of newborn (TTNB)
OTHER INDICATION
Pneumonia
Meconium aspiration/other aspiration syndrome
Pulmonary edema/pulmonary hemorrhage
Laryngomalacia/tracheomalacia/bronchomalacia
19. Early CPAP in RDS
was proved to be more beneficial in the atelectatic
disease
lower peak pressure required in infants treated with
CPAP
enhance surfactant conservation
reduce the need for IMV by 20%, except infants with
birth weight <1500 g.
improve mortality and decrease the incidence of BPD
prevent need for prolong intubation which reduce the
incidence of acquired subglottic stenosis
20. Failure of CPAP therapy in
RDS
very low birth weight infant
late application of CPAP
severity of RDS
associated disease e.g. sepsis,
hypotension
infants with severe degree of
extrapulmonary shunt
(Fox and coworkers, 1977)
21. CPAP in apnea of prematurity
the application of low-level CPAP decrease the incidence
of apnea of prematurity (compared to other forms of
stimulation)
improve oxygenation
stimulation or inhibition of pulmonary reflexes
alveolar stabilization
mechanical splinting of airway; reduce supraglottic
resistance in both inspiration and expiration
some investigators recommended the early use of CPAP
as a preventive measure of apnea of prematurity
22. CPAP IN INFANTS WITH MAS
pathology of meconium aspiration
atelectasis
large airway obstruction
V/Q abnormalities
application of low-to moderate
level CPAP
resolution of atelectasis
stabilization of terminal airway
incidence of pneumothorax: not
increased
precautions in case with PPHN
23. C0NTRAINDICATION OF CPAP
Progressive respiratory failure with PaCO2 levels >60
mmhg and/or inability to maintain oxygenation
(PaCO2 <50 mmHg)
Certain congenital malformation of the airway
(choanal atresia, cleft palate, tracheoesophageal
fistula, congenital diaphragmatic hernia,etc)
Severe cardiovascular instability (hypotension)
Poor respiratory drive (frequent apnea and
bradycardia) that is not improved by CPAP.
25. CPAP MACHINES
An ideal CPAP delivery system consists of:
A continuous supply of warm, humidified, blended
gases at a flow rate of 2-3 times the infant minute
ventilation.
A device to connect CPAP circuit to infants airway.
Means of creating a positive pressure in CPAP circuit.
26.
27. CPAP DELIVERY SYSTEM
Ventilator : ideal system to
provide CPAP but very costly
CPAP system : should have
1. End expiratory pressure of 0-15
cm of water.
2. Humidification of upto 100%
3. Gas flow 5-8 L/min
4. Warming of gases to 34-37˚c
5. Blending oxygen-air mixture FiO2
0.21-1.0
6. Low noise compressor
7. Compatibility to run days & weeks
8. Reasonable cost
30. SETTING PRESSURE, FLOW &
FiO2
1. Pressure- regulated by depth of immersion of
expiratory limb(water level being constant).start
with 5 cm water in case of RDS or pneumonia and 4
cm water for apnea management.(range- 4-8)
2. Flow- it should be minimal to produce bubbling in
the bubble chamber(2-5 L/min is sufficient)
3. FiO2- start with a FiO2 of 40 to 50% and after
adjusting the pressure,titrate FiO2 to maintain SpO2
between 89% to 94%.
33. MONITORING THE INFANT
CONDITION
Recommended monitoring:
• Respiratory status (RR, work of
breathing)
• Pre ductal oxygen saturation
• Cardiovascular status (HR, BP,
perfusion)
• GI status (abdominal distention, bowel
sounds)
• Neurological state (tone, activity,
responsiveness)
• Thermoregulation (temp)
34. WEANING FROM CPAP
It is considered when clinical condition
for which CPAP was indicated is
passive.
e.g. in case of RDS we have to see for
improvement in Silverman Anderson
score i.e. if score is less than 4 we can
try weaning
36. WEANING FROM CPAP
CPAP for apnea may be removed after 24 -48 hrs of apnea
free interval.
If the baby is stable on CPAP,first wean off the oxygen in
steps of 5% and then wean PEEP to minimum of 4cm in
step of 1cm/change.
When baby is in FiO2<30%, PEEP 4cm, with normal
saturation and minimal retraction CPAP can be removed.
37. CPAP FAILURE
CPAP failure is considered if FiO2 required is
>60% and PEEP required is > 7cm of water.
If baby is continuing to have retraction,
grunting and apnea is considered fo
mechanical ventilation.
If PaO2<50%, SpO2<85%, and PaCO2>60%
on CPAP with FiO2>60% and PEEP >7cm of
water is also considered for mechanical
ventilation.
39. Maintaining Optimal
Airway Care: Humidification
• Maintain adequate
humidification of the
circuit to prevent
drying of secretions.
• Adjust settings to
maintain gas
humidification at or
close to 100%.
• Set the humidifier
temperature to 36.8-
37.3o C.
40. Complications associated with
bubble nasal CPAP
● Pneumothorax / PIE
- more in the acute phase
- not a contraindication for continuing CPAP
● Nasal obstruction
- Remove secretions and check for proper positioning
of the prongs
● Nasal septal erosion or necrosis
- Keep prongs away from the septum
● Gastric distension
Intermittent or continuous aspiration of the stomach
● Feeding intolerance
41. Preventing Complications:
Gastric Distention
• NCPAP is not a
contraindication to
enteric feeding.
• Infants may
experience mild
abdominal
distention during
NCPAP delivery
from swallowing air.
43. Preventing Complications:
Gastric Distention
To prevent gastric
distention:
• Assess the infant’s
abdomen regularly
• Pass an oro-gastric tube
to aspirate excess air
before feeds q 2-4 hr
• An 8 Fr oro-gastric tube
may be left indwelling
to allow for continuous
air removal
Let us understand the relationship between Lung volume – X axis with Pulmonary vascular resistance – y Axis .
PVR is least once the lung is open at the FRC , at this blood flow is maximum with Best ventilation perfusion matching and gas exchange.
You can see on Right- baby with MAS has higher lung volume while on left HMD has lower lung volume both RESULT in high PVR .
In clinical practice , for a baby on CPAP with higher pressure the lung will over distend while low CPAP will cause reduced FRC – in both PVR will increase causing Rt to left shunt impairing pulmonary blood flow .Thus we must ensure lung is opened at FRC for best blood flow and better gas exchange .
Imagine two alveoli are connected to same terminal airway – the smaller alveoli will have tendency to collapse and empty into larger due to higher collapsing pressure
Notice Rt smaller alveoli has pressure 6 cm while left bigger one 4 cm as the radius small r is 1 and 1.5 respectively .