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Continuous Positive Airway Pressure (CPAP)

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CPAP BabyContinuous positive airway pressure (CPAP) is used to maintain continuous positive pressure during both inspiratory and expiratory phases when the infant is breathing spontaneously.

Bubble CPAP delivered via binasal prongs is the preferred mode of initial ventilatory support in infants with respiratory distress.

It was initially introduced into the NICU at National Women's Hospital in 1997.

Its effects include:

  • Increase in functional residual capacity leading to an increase in PaO2
  • Increases pulmonary compliance
  • Increases spontaneous tidal volume and reduces respiratory effort
  • Decrease in alveolar-arterial oxygen pressure gradient
  • Prevents alveolar collapse
  • Increases airway diameter
  • Conserves surfactant
  • Splints the airway
  • Splints the diaphragm
  • Reduces mechanical obstruction (eg. meconium)

The baby may be nursed prone, skin to skin (kangaroo), supine or side lying (that is, there are no limitations to positioning!). Orogastric feeds are as ordered / tolerated.

Indications for CPAP

  • Any signs of significant respiratory distress:
    Tachypnoea
    Flaring
    Grunting
    Retractions
    Cyanosis
    O2 requirement
  • Diseases with low functional residual capacity (FRC):
    RDS
    TTN
    Pulmonary oedema
  • Meconium Aspiration Syndrome
  • Airway closure disease
    BPD
    Bronchiolitis
    Apnoea and bradycardia of prematurity
  • Weaning from mechanical ventilation
  • Tracheomalacia
  • Diaphragmatic paralysis

Requirements for effective CPAP

Low Resistance Delivery System - Large bore tubing 
- Short, wide connection to patient 
Consistent, reliable pressure generation - Appropriate, snug-fitting nasal prong size 
- Well positioned and secure 
- Prevention of leak via mouth with chin strap 
- Carefully set-up and maintained circuit 
Optimally Maintained Airway - Warmed, humidified gas 
- Neck in mild extension 
- Appropriate airway care, eg. suctioning 
Applicable to the Very Low Birthweight Infant - Hudson prongs size 0 through 5 
Relatively atraumatic, safe and cost-effective   
Early application At first onset of symptoms 
Meticulous, consistent technique Skilled caregivers

Complications

Nasal Septal Erosion or Necrosis This is preventable when using appropriate sized prongs that are correctly positioned. 
Pneumothorax - Usually occurs in acute phase. 
- It is uncommon (<5%). 
- It usually results from the underlying disease process rather than positive pressure alone. 
- It is not a contraindication to the use of CPAP. 
Abdominal Distension from Swallowing Air
(see radiographic images below)
This is benign 
- Easily reduced with gastric drainage or aspiration (see "CPAP Belly" below)
Nasal obstruction From improper prong placement or inadequate airway care 

CPAP Belly

Clinically, there is distension of the abdomen without discolouration of the abdominal wall and without tenderness. Feeds are often tolerated but gastric aspirate residuals are not uncommon. The aspirates are usually undigested milk, and bilious aspirates should make you think of other causes. Occasionally the distension can be so great as to cause respiratory embarrassment.

Radiographically, there is evidence of intestinal air, without features which would suggest other more sinister processes (i.e. intramural gas, free air, thick-walled bowel loops).

Treatment is to:
- Ensure that a large-bore intragastric tube is vented
- Allow time off CPAP if possible
- Encourage the baby to pass stool (using glycerine suppositories) if this is a problem

Commencement and setup of CPAP

Follow the steps below to set up Hudson CPAP Circuit:

Step Action Rationale
1 Use disposable self-filling humidifier top with a 1 litre bag of water attached. Adequate humidity will prevent drying of secretions. 
2 A flow of 6-10 litres per minute is delivered via a blender. An oxygen analyser is used continuously and calibrated once a shift:

- To air if O2 <60%
- To 100% O2 if >60% 
A flow of 6-10 L/m:
- provides adequate pressure to wash out carbon dioxide from the system
- compensates for the normal air leakage from tubing connections
- generates adequate CPAP pressure (verified by bubbling of the water in the CPAP generator).
N.B The baby should receive the specific percentage of oxygen required. 
3 A pressure relief valve is part of the circuit with the valve fixed to blow off at 17cm H2O.

This ensures that any pressure in excess of 17cm H2O will blow off the pressure relief valve should the expiratory line become occluded.
 
This is a safety precaution only. The pressure relief valve does not affect the CPAP pressure.
Occlude pressure line connection port with white plug provided.  This completes the CPAP circuit.
NB: check the CPAP circuit is complete (bubbling) before applying to baby. 
The default pressure is set at 6cm H2O
Pressures greater than this (up to 10cm H2O) may be used.  
This controls the pressure generated in the system. It is important to check the water level and adjust for evaporation, if required. 
Place a roll under the infant's neck to slightly extend the neck.  Ensures optimum airway. 
Suction airway prior to application of CPAP prongs.
Pass an orogastric tube and aspirate stomach contents (a larger baby may not need an indwelling tube if Nil By Mouth)  
If these procedures are done prior to prong placement then less handling is required after infant is on CPAP. 
Preductal SaO2 probe in place. (preferably right arm)   Optimal saturation maintained according to unit target saturations 
CPAP hat is applied to baby - it must not be too tight a fit as this causes excessive moulding to the head but should be sufficiently snug to stay in place.

Ribbed stockinette is available in two sizes to make hats

Individual hats are also available for infants weighing approximately 1000-2000 grams  
A snug fitting hat is a must. The hat is the anchor for the prongs. A loose hat will allow any movement of the head to dislodge the prongs. 
10  Applying the prongs. Gently insert the prongs that fit the nares snugly without causing pressure:

Place curve side down into the baby's nose (follow the natural curve of the nose)
Adjust the angle of the prongs and the way the corrugated tubing is twisted until the correct positioning is achieved.  

Infant size    Prong size
  <700g                0
 700-1250g          1
1250-2000g         2
2000 - 3000g       3
  >3000g              4
  >4000g              5

Apply duoderm base tapes to cheeks with rough (hook side) velcro patches attached.
Wrap 'soft' (loop side) velcro around the prongs.
Nasal prongs should fill the nasal opening completely without stretching the skin or putting undue pressure on the nares (blanching around the rim of the nostrils suggests that the prongs are too large).

The corrugated tubing will not be touching the baby's skin.

There will be no lateral pressure on the septum causing it to be pinched or twisted.

There will be a small space between the tip of the septum and the bridge between the prongs.
11  Secure the inspiration and expiration lines to the CPAP hat using small safety pins and rubber bands. Ensure safety pins are away from the eyes.    If prongs are correctly positioned in the nose and the tubing allowed to sit naturally in place, rotating pressure on the prongs is avoided.
12  Position chin strap. This can be simply made using non-elastic tape and gauze.

Cut a piece of tape that will reach from one side of the hat across under the chin and attach to the other side of the hat.

The tape needs to be backed with folded gauze to prevent the adhesive contacting the skin.

The jaw is gently pulled forward, closing the mouth.

A pacifier (dummy) may be used with the chinstrap in place if this will help the baby settle.  
 An air leak via the mouth will reduce the effectiveness of the system by allowing a significant loss of positive pressure.

Keeping the design simple will be both cost-effective and convenient, as the chinstrap may need replacing every few hours. It will easily become soiled and the tape loses its adhesives each time it is detached from the hat for suctioning or feeding.

The strap will not be so firm as to prevent the infant from crying or yawning.

Troubleshooting

 "It's not Bubbling!"

This indicates loss of air flow or a pressure leak somewhere in the system. A simple way to check if it is a 'circuit' problem or a 'baby' problem is to remove the prongs from the nose and occlude them with your fingers.

If the system doesn't bubble it means the problem is with the circuit. Systematically check the circuit, tightening all connections as you go. (see Commencement and Setup of CPAP above). Begin at the wall and end at the water-bubble generator.

If the system does bubble, when you occlude the prongs with your fingers then the pressure leak is at the nose or mouth. Air will escape if the prongs are too small or if they are not curved down into the nose and fitting snugly. The suggested sizes (based on weight) are a guide only as babies nose sizes do vary. A chin strap will reduce leak via the mouth. A dummy may help an unsettled baby.

Check white tubing for accumulation of "rainout", as this will swing backwards and forwards in the tubing without an audible bubble.

A Duoderm Patch may be applied to nares for problems with a seal / no bubbling, following assessment by a member of the CPAP Resource Team. (Information sheet will be given out at the appropriate time)

"The prongs won't stay in place!"

  • Are they the right size?
  • Does the hat fit snugly? The hat is the anchor for the prongs so a loose hat will allow any movement of the head to dislodge the prongs.
  • Are the corrugated tubes fixed firmly in place on the side of the hat and are they at the correct angle to keep the prongs in place? If there is rotating pressure on the prongs they may twist out of the nose. If in doubt, try undoing the rubber bands and with the prongs correctly positioned in the nose, allow the tubing to sit naturally in place. Reposition the pins and the rubber bands as necessary. Ensure that the base tapes are secure on the face. Do the existing ones need replacing? See application instructions in Commencement and Setup above.

"The baby won't settle!"

  • Are the prongs positioned in the nares appropriately and comfortably?
  • Does s/he need suctioning? This may seem a contradiction when suggesting ways to settle a baby down, but a build up of secretion can cause considerable distress to a baby whose breathing is already compromised.
  • Once you are sure the airway is clear try the usual calming techniques of containment, nesting, swaddling, pacifier, etc.
  • Aspirate any excess gastric air and vent tube to room air if necessary.
  • Try positioning the baby prone as this can help relieve abdominal distension and diaphragmatic pressure.
  • Often just "hands off" will allow the baby to slowly settle, especially in the early hours as they adjust to the CPAP.

"How can we avoid septal damage?

Prevention is the key. Tissue will break down if it is subjected to continuous pressure, friction and/or moisture. Avoiding these contributing factors will maintain an intact septum:

  • Use the correct sized prongs as outlined in the application instructions
  • Secure them in place with a snug fitting hat, correctly positioned pins and rubber bands over the corrugated tubing
  • Use velcro base tapes to hold the prongs and tubing secure
  • Don't allow the bridge of the prongs to press up against the septum
  • Avoid twisting of the prongs with resultant lateral pressure against the septum
  • Do not use creams, ointments or gels (use saline drops to moisten the nares for initial prong insertion or during suctioning if necessary)
  • Frequent observation of the septum and prong position is essential. Be wary of eye pads that cover the nose on babies under phototherapy as these can obstruct your view of the septum.

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Document Control

  • Date last published: 01 October 2018
  • Document type: Clinical Guideline
  • Services responsible: Neonatology
  • Owner: Newborn Services Clinical Practice Committee
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years