C P A PC P A PContinuous Positive Airway Pressure

Mesfin Woldesenbet, M.D.

Neonatal-Perinatal medicine

Pediatrix Medical Group

August 2011

Abbreviations

• FRC: Functional Residual Capacity

• RDS: Respiratory Distress Syndrome

• HMD: Hyaline Membrane Disease

• TTN: Transient Tachypnea of the Newborn

• PEEP: Positive End-Expiratory Pressure

• CPAP: Continuous Positive Airway Pressure

Historical Perspectives

• Early 1950’s- Iron lungs used in polio epidemic were the first successful negative pressure ventilators.

• Late 1950’s- Volume-controlled, positive pressure ventilators were designed

• 1959 the first of such ventilators were used on newborns

Historical Perspectives – cont.

• Early 1960’s - assisted ventilation for hyaline membrane disease became more common, but was used only with strict criteria

*pH less than 7.0

*PO2 < 30-40 mmHg in 100% oxygen

*Paco2 greater than 80 mmHg

These were very sick newborns

Historical Perspectives - cont

• In 1971 CPAP using an endotracheal tube was a breakthrough in the treatment of newborn RDS which demonstrated dramatic improvement of oxygenation.

Historical Perspectives –cont.

• In 1973 CPAP using nasal catheters positioned in the midnares was used on infants weighing >1500gms who had RDS requiring >60% oxygen to maintain a PaO2 of 50-60 mmHg.

• These early interventions increased survival of preterm infants.

CPAP today

• It is Continuous Positive Airway Pressure applied to the airways of a spontaneously breathing patient throughout the respiratory cycle. It is accomplished by nasal prongs that provide heated and humidified oxygen mixtures continuous or variable flow from a circuit connected to a ventilator set in CPAP mode or a bottle filled with liquid (Bubble CPAP).

PEEP/CPAP

• LaPlace’s law: It is difficult to blow up a small balloon the first time because it takes more applied pressure to start the stretching process necessary for inflation.

• The difficulty of inspiration during the baby’s first breath is great because all the balloons (i.e. alveoli) must be inflated from a collapsed state

• Premature infant’s alveoli are even more difficult to inflate because of the lack of surfactant, which coats the alveoli and reduce surface tension.

• The oxygen exchange from air to blood is proportional to the surface area of the exchange membrane (alveoli).

Larger alveolus

r = 2T = 3

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

Smaller alveolus

r = 1T = 3

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

CPAP

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

Benefits of PEEP/CPAP

• PEEP keeps the alveoli open at the end of expiration so that they do not stick together and are easier to re-inflate.

• This results in increased surface area in the alveoli for better oxygen exchange from the air to blood.

• Controlled PEEP has been shown to improve oxygenation when used for babies who need more than normal resuscitation at birth but are breathing spontaneously.

Desired Outcomes for all methods of Ventilatory Support

• Reduction in the work of breathing as indicated by a decrease in respiratory rate by 30-40%.

• Reduction in the severity of retractions, grunting and nasal flaring.

• Improved lung volumes and appearance of lung on X-RAY

• Improved patient comfort (assessed)• Reduction in apnea, bradycardia and cyanosis

Effects of CPAP

1. Increases transpulmonary pressure and functional residual capacity (FRC)

2. Prevents alveolar collapse, decreases intrapulmonary shunt and improves lung compliance

3. Conserves surfactant4. Prevents pharyngeal wall collapse5. Stabilizes the chest wall6. Increases airway diameter and splints the airways7. Splints the diaphragm8. Stimulates lung growth

Indication of CPAP

1. Diseases with low FRC, e.g. RDS, TTN, PDA, pulmonary edema, etc.

2. Apnea and bradycardia of prematurity3. Meconium aspiration syndrome (MAS)4. Airway closure disease, e.g. BPD5. Tracheomalacia6. Partial paralysis of diaphragm7. Respiratory support after extubation

Meconium Aspiration Syndrome (MAS)

Inspiration Expiration

Meconium Aspiration Syndrome (MAS)

With CPAP No CPAP

CPAP Devices• Head hood

• Face shield

• Face mask

• Nasal mask

• Nasal prongs – Hudson, INCA, Draeger, Fisher&Pakel, SiPAP, Arabella, NeoPAP

• Nasal cannula – Vapotherm

• Nasal pharyngeal tube

• Endotracheal tube

Nasal CPAP Set up ( 1 )

1. Oxygen blender

2. Flowmeter(5-10 LPM)

3. Heated humidifier

4. Thermometer

5. Inspiratory tubing

6. Nasal cannulae

7. Velcro

Nasal CPAP Set up ( 2 )

8. Manometer (optional)

9. Expiratory tubing

10. A bottle containing a solution of 0.25% acetic acid filled up to a depth of 7 cm. Distal tubing immersed to a depth of 5 cm to create +5 cmH2O

Nasal CPAP Application (1)

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 (2)

4. Choose FiO2 to keep PaO2 at 50’s

or

O2 saturation at

85% – 95%

Nasal CPAP Application (3)

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)

Nasal CPAP Application (4)

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

Nasal CPAP Application (5)

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 (6)

CPAP CannulaeSize B.W.0 < 700g1 ~1000g2 ~ 2000g3 ~ 3000g4 ~ 4000g5 infant

8. Choose the proper size of nasal Cannulae

Nasal CPAP Application (7)

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

Nasal CPAP Application (8)

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

Nasal CPAPMaintenance (1)

1. Observe baby’s vital signs, oxygenation and activity

2. 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. A snug cap is used to securely hold the tubings in place and using self-adhesive Velcro to keep cannulae away from the septum if necessary

Nasal CPAPMaintenance (2)

4. Suction nasal cavities, mouth, pharynx and stomach q4h and prn

5. Change the baby’s position

6. Change CPAP circuit once a week

Nasal CPAPWeaning

• CPAP is kept at 5 - 7 cmH2O

• FiO2 is adjusted to keep PaO2 in 50’s, or oxygen saturation around 85%-95%

Nasal CPAPDiscontinued

• No tachypnea or retraction

• No apnea and bradycardia

• FiO2 is usually room air

Nasal CPAPComplications

• Nasal obstruction from secretions or improper application of nasal prongs

• Gastric distention from swallowing air

• Nasal septum erosion or necrosis

• Fluctuating FiO2

• Air leak: <5%, usually occurs during acute phase

Percent use of ENCPAP

6%

Success with Early NCPAP and Incidence of BPD

Incidence of BPD

33%

Aly, H. et al. Pediatrics 115:1660-5, 2005.

References

• A. Graham, N. Finer. The use of continuous positive airway pressure and positive end-expiratory pressure in the delivery room. Pediatric Research, 49 (400), pp 2299.

• C. O’Donnell, P. Davis, C. Morley. Positive end-expiratory pressure for resuscitation of newborn infants at birth. NICHD, Issue 4, Last edited 8/04.

• Clark, et al., Lung protective strategies of ventilation in the neonate: What are they. Pediatrics Vol 105 No. 1, January 2000, pp 112-114.

• M. Keszler. Volume targeted ventilation. NeoReviews, May 1, 2006; 7(5), pp250-257.

• NOVA Online. How the body uses O2. Updated November, 2000.

• P. Seddon, G. Davis. Validity of esophageal pressure measurements with positive end-expiratory pressure in preterm infants. Pediatric Pulmonology, August 4, 2003; 36(3), pp 216-222.

• P. Sharek, R. Baker, F. Litman, J. Kaempf, K. Burch, E. Schwarz, S. Sun and N. Payle. Evaluation and development of potentially better practices to prevent chronic lung disease and reduce lung injury in neonates. Pediatrics, April 1, 2003; 111(4), pp 426-431