CPAPA Gentler Mode of Respiratory Support

• It is Continuous Positive Airway Pressure applied to the airways of a spontaneously breathing patient throughout the respiratory cycle.

• By which alveoli are kept open which increase the functional residual capacity(FRC) of the lungs resulting in better gas exchange.

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. ‘-1973

• 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.

A Device for Administration of Continuous Positive Airway Pressure by the Nasal RouteJohn Kattwinkel, David Fleming, Chul C. Cha, Avroy A. Fanaroff, Marshall H. Klaus

• Surface tension is the elastic tendency of a fluid surface which makes it acquire the least surface area possible.

Larger alveolusr = 2T = 3

P = (2 x 3) / 2P = 3

Smaller alveolusr = 1T = 3

P = (2 x 3) / 1P = 6

CPAP

Law of LaPlace : P = 2T/r P : pressure T : surface tension r : radius

• Thus smaller (diameter) alveoli will have a tendency to empty into larger (diameter) alveoli connected to each other.

• If the surface tension is reduced by giving exogenous surfactant, the inward pressure which leads to collapse can be reduced.

• By giving CPAP, one neutralizes the inward collapsing pressure.

• The net effect of both is more than additive. This principle is applied in clinical practice for INSURE (Intubate give Surfactant and Extubate to CPAP).

Closing Volume

• Closing volume is the volume of lung inflated when small airways in the dependent parts of the lung begin to collapse during expiration.

Physiological Benefits of CPAP:

• Results in improved oxygenation, wash out of CO2, and better blood pH.

• Stimulates ’J’ receptors by stretching the lung/pleura and providing positive feedback to respiratory centre by Hering Bruer reflex.

• Results in better Type II-pneumocyte function and even recycling of surfactant thus contributing to early recovery from HMD.

• Results in better ventilation-perfusion match, improved minute ventilation and decreased work of breathing.

• Splints the upper airways thus preventing obstructive apnea

Indications: Diseases with low FRC

RDS, TTNB. Diseases with airway instability

Apnea of prematurityBPDTracheomalacia

Weaning from IMV Patchy atelectasis

MAS, aspiration, pneumonia

Contraindication

• Severe Cardiovascular instabality ( SHOCK) • Progressive respiratory failure with PaCO2 >60

mm hg and inability to maintain oxygenation(PaO2<50mmhg)

• Certain congenital malformations of the airway like choanal atresia, cleft palate, tracheo osophageal fistula, CDH.

CPAP Machine:

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. (patient interface)• Means of creating a positive pressure in CPAP circuit.

Types of CPAP

• Continuous flow– Ventilator generated– Bubbling CPAP

• Variable flow– Infant flow drivers.

Bubble CPAP- principle

36

Patient

Nasal prongs/NP ET tubeUnder

H20 seal

Bubble=Oscillations

Patient interfaces for cpap

Hudson’s prongs Bi-nasopharyngeal prongs

ET tube

Short bi-nasal prongs Argyle prongs

Delivery system advantages disadvantages remarks

Nasal prongs(single or binasal)eg:argyle,hudson, IFD prongs.

Simple device. Lower resistance. Mouth leak acts like a pop-off mechanism.

Relatively difficult to fix. Risk of trauma to nassal septum. Leak through mouth means end expiration pressure is variable.

Studies have shown that they are more effective than nasopharyngeal prongs(in post extubation setting)

Nasopharyngeal prongs(using cut endotracheal tube)

Easy availability. Economical. More secure fixation.

More easily blocked by secretions: likely to get kinked.

Though more economical, they are inferior to short binasal prongs.

Nasal canualae. Easy application Unreliable pressure. May need high flows to genarate pressure. FiO2 delivered may be high.

Mainly tried in apnea of prematurity. Paucity of data in other condition. Still a experimental.

Nasal mask minimal nasal trauma.

Difficulty in obtaining a tight seal

New generation mask are to be studied.

Steps of Initiation of CPAP:

Nasal CPAP Application

1. Position the baby in supine position with the head elevated about 30 degrees

2. Place a small roll under the baby’s neck

3. Put a pre-made hat or stockinet on the baby’s head to hold the CPAP tubings

Nasal CPAP Application

4. Choose FiO2 to keep PaO2 at 50-80

mmhg or O2 saturation at

85% – 95%

Nasal CPAP Application

5 Adjust a flow rate 5-10 Lpm to:

a) provide adequate flow to prevent rebreathings CO2

b) compensate leakage from tubing connectors and around CPAP prongs

c) generate desired CPAP pressure (usually 5 cmH2O)

6. Keep inspired gas temperature at 36-40O C (0 ~ –3)

Nasal CPAP Application

7. Insert the lightweight corrugated tubing (preferrably with heating wire inside) in a bottle of 0.25% acetic acid solution or sterile water filled up to a height of 7 cm. The tube is immersed to a depth of 5 cm to create 5 cmH2O CPAP as long as air bubbling out of solution

Nasal CPAP Application

Lubricate the nasal CPAP prongs with sterile water or saline. Place the prongs curved side down and direct into nasal cavities

Nasal CPAP Application

10Secure tubings on both sides of the hat with either safety pins and rubber band or velcro

Nasal CPAPMaintenance

1. Observe baby’s vital signs, oxygenation and activity2. Systematically check CPAP systems, inspired gas

temperature, air bubbling out of acetic acid solution. Empty condensed water in the circuit

3. Check CPAP prongs position and keep CPAP cannulae off the septum at all times.

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- 37.3c

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 87% to 93%.

Adequacy of CPAP

• Comfortable baby• No retraction, no grunt• Normal capillary refill, BP• Normal saturations: 87-93%

• Normal ABG (PaO2 60-80, PaCO2 40-60, pH 7.35-7.45, BE±2)

Failure of CPAP

• Continuing retractions, grunt.• Recurrent apneas• PaO2 < 50mm Hg at highest setting.• PaCO2 > 60 mm Hg• Baby not tolerating CPAP • FiO2 required is greater than

70%,PEEP>7 .• Inability to maintain SPO2>85%

Before considering CPAP failure ensure:

WEANING FROM CPAP

• It is considered when clinical condition for which CPAP was indicated is passive.

• 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.

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

Prevention of Gastric distension:

• NCPAP is not a contraindication to enteric feeding. • Infants may experience mild abdominal distention

during NCPAP delivery from swallowing air. • 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

Conclusion• CPAP used in RDS, apnea, weaning.• Pressure generator – Bubble CPAP

• Circuit of choice– Heated humidifier

• Nasal device of choice– NP CPAP > cannula

• CPAP range 4-8

References:

• Ashok Deorari et al .Workbook on CPAP –Science Evidence and practice,2014.

• Eduardo Bancalari.Principles of respiratory Monitoring and theraphy.Avery s diseses of Newborn7th 3d:613-628

• Aparna ,Non Invasive ventilation in Newborn. www.newbornwhocc.org/pdf/Non-invasive-Ventilation.pdf

• Samir Gupta .CPAP .To bubble or not to Bubble.Non invasive ventilation.Clinics in Perinatology:647-661,December2016.