Cpap

CPAP

CPAP and PEEP CPAP refers to a positive pressure applied to the airways of a spontaneously breathing baby throughout the respiratory cycle. PEEP refers to the positive pressure applied to a mechanically ventilated neonate during the expiratory phase of respiration.

History • Use of CPAP began in 1970s as the missing link between supplemental oxygen and mechanical ventilation. • During the 1980s & early 1990s CPAP fell out of favor as it was believed to cause increased incidence of air leaks, gastric distension, damage due to hard nasal prongs. • Resurgence in interest in late 90s.

Benefits of Using NPPV Compared to Invasive Ventilation • Avoids the trauma associated with intubation and the complications associated with artificial airways • Reduces the risk of ventilator associated pneumonia (VAP) • Reduces the risk of ventilator induced lung injury associated with high ventilating pressures

Contd… • Provides ventilatory assistance with greater comfort, convenience and less cost than invasive ventilation • Reduces requirements for heavy sedation

Physiology

How can CPAP or PEEP help the baby with a respiratory problem? • It reduces upper airway occlusion by decreasing upper airway resistance and increasing the pharyngeal cross sectional area. • It reduces obstructive apnoeas. • It increases the FRC. • It increases the compliance and tidal volume of stiff lungs with a low FRC by stabilising the chest wall and counteracting the paradoxical movements

• It reduces inspiratory resistance by dilating the airways. This permits a larger tidal volume for a given pressure, so reducing the work of breathing. • It regularises and slows the respiratory rate. • It conserves surfactant on the alveolar surface. • It diminishes alveolar oedema. • Nasal CPAP after extubation reduces the proportion of babies requiring reventilation.

Optimal lung inflation. • Defined as the lung volume at which the recruitable lung is open but not over-inflated. • CPAP is one method which best achieves optimal lung inflation with resultant good oxygenation and ventilation and hopefully less CLD.

Methods of generating CPAP Continuous flow CPAP

Variable flow CPAP

• It consists of gas flow generated at a source and directed against the expiratory limb of a circuit.

• It generates CPAP at the airway proximal to the infant’s nares.

Continuous flow CPAP • In ventilator-derived CPAP, a variable resistance in a valve is adjusted to provide this resistance to flow. • In bubble CPAP the distal end of the expiratory tubing is immersed under either 0.25% acetic acid or sterile water to a specific depth to provide the desired level of CPAP. • Another continuous flow system is Benveniste gas-jet valve.

Variable flow CPAP • These devices have dual injector jets directed at each nasal prong in order to maintain a constant pressure. Patient nasal connection

Intra nasal pressure monitoring Fresh gas inlet

Interchangeable Nasal prongs Twin jet injector Nozzles. Expiratory channel

Child’s exhalation

Connection to Nasal prongs.

Fluidic flip of Inspiratory Gases.

• The major advantage of variable flow CPAP is reducing the work breathing. • In continuous flow CPAP, during exhalation infant must exhale against the flow of incoming air. • The fluidic flip of variable flow devices assists exhalation.

• Additionally the variable flow devices appear to be able to maintain a more uniform pressure level compared to continuous-flow CPAP. • The most commonly used variable-flow system is the Infant flow driver (IFD).

Devices through which CPAP is provided. • Nasal devices Prongs Types- short – 6-15mm (nasal prongs) long – 40-90mm (nasopharyngeal prongs) Nasal cannula Nasal masks • Face masks • Head box with nasal seal • Endotracheal tubes.

WHICH NASAL CPAP DEVICE SHOULD BE USED? • Nasal and nasopharyngeal prongs remain the most common method of administering CPAP in neonates. • Devices in common use for the delivery of nasal CPAP include single and double (binasal) prongs, in both short (nasal) and long (nasopharyngeal) forms.

Types of prongs • Argyle • Hudson • Inca • Fisher & Paykel • EME • Nasopharyngeal

Single versus double prong devices • The evidence, from a meta-analysis of randomised clinical trials of nasal CPAP devices in very preterm neonates, is that short binasal devices are more effective at preventing re-intubation when compared with single nasal prong devices. A randomised trial in more mature preterm infants with early respiratory distress reported better oxygenation, respiratory rate, and weaning success with a short binasal device when compared with single prong nasopharyngeal CPAP.

Which short binasal prongs should be used? •There are . several short binasal prongs available to the clinician, including the Argyle prong, Hudson prong, infant flow driver (IFD), and INCA prongs. •Studies using lung models suggested that the prototype IFD, compared with Argyle prongs and Hudson prongs, generated more stable pressures.

Can nasal cannulae be used to deliver nasal CPAP? • Nasal cannulae are used to deliver oxygen into the nose at low flow, usually with no intention of generating positive pressures in the airway. However nasal cannulae, with an outer diameter of 3 mm and flows up to 2 l/min, have been reported to deliver CPAP. A study of CPAP via nasal cannulae found it as effective in the treatment of apnoea of prematurity as conventional CPAP prongs.

HOW SHOULD NASAL CPAP DEVICES BE FIXED? There are many different techniques for fixing the devices to the infant. The exact technique does not matter as long as the device is secure and not traumatising the nose, face, or head. More research is needed to define the least traumatic nasal device and method of fixation.

IS MOUTH CLOSURE IMPORTANT? When NCPAP or NPCPAP are applied, there often is enough downward pressure on the palate, providing a natural seal so that there is minimal to no pressure loss through the mouth.

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ET CPAP Disadvantages • Increased resistance • Increased dead space • Requires invasive intubation

Bubble nasal CPAP

Bubble CPAP Delivery System

Oscillations from the bubbling reverberated back into the infant's airway and it is speculated that the observed vibrations enhance gas exchange

Is bubble CPAP superior to conventional CPAP? • Few randomised studies have compared these two approaches, but those that have (Colaizy, 2004; McEvoy, 2004; Lee, 1998) have recorded reductions of up to 50% in the need for mechanical ventilation in favour of bubble CPAP. • Another advantage is low cost: bubble CPAP equipment costs are 15% of those for mechanical ventilation, and the technique can be administered by nursing staff.

An indigenous bubble CPAP

An indigenously developed low cost device is certainly welcome but not at the cost of compromised safety and potential harm.

Primary uses of CPAP Disorders in which use of CPAP has been studied in RCTs are 2. Treatment of apnea of prematurity, 3. In Post-extubation management following mechanical ventilation, 4. Early management of RDS.

Apnea of prematurity • Because longer episodes of apnea frequently involve an obstructive component, CPAP appears to be effective by splinting the upper airway with positive pressure and decreasing the risk of pharyngeal or laryngeal obstruction. • CPAP probably also benefits apnoea by increasing functional residual capacity (FRC) and so improving oxygenation status. • It has been shown that at higher FRC, time from cessation of breathing to desaturation and resultant bradycardia is prolonged.

However, the Cochrane review regarding CPAP use for AOP concludes that this area needs additional evaluation.

Post-extubation management following mechanical ventilation The Cochrane Collaboration review concluded: “Nasal CPAP is effective in preventing failure of extubation and reducing oxygen use at 28 days of life in preterm infants following a period of endotracheal intubation and IPPV.”

NCPAP as primary therapy for RDS • If a preterm baby with RDS is spontaneously breathing well enough to maintain adequate heart rate, but with distress (manifested by some combination of grunting, flaring and retraction), mechanical ventilation with PEEP may be indicated. • Rather than immediately employing mechanical ventilation, many neonatologists will strongly consider the use of CPAP in this setting, usually at a medium level of pressure.

In a survey of all 58 neonatal units with intensive care cots in the Northern Region of England it was found that briefly intubating, giving surfactant, then starting NCPAP (INSURE) is common in infants with severe respiratory distress syndrome and in very preterm infants. This is despite scant evidence to date that the practice decreases chronic lung disease or need for mechanical ventilation.

• Sandri et al performed a RCT in 230 premature infants (28-31wk) comparing prophylactic NCPAP (within 30min of birth) to rescue NCPAP (once the infants required an FiO2>40% to maintain SpO2 levels). • There were no significant differences between groups with regard to need for exogenous surfactant or mechanical ventilation. • Conclusions: In newborns of 28–31 weeks gestation, there is no greater benefit in giving prophylactic NCPAP than in starting NCPAP when the oxygen requirement increases to a FIO2 > 0.4.

Other applications of CPAP in neonates • • • • • • • •

MAS. Post-op respiratory management. Pulmonary edema. CHF. Laryngomalacia, tracheomalacia. PPHN. Pulmonary hemorrhage. Use of CPAP in delivery room.

CPAP in delivery room • If CPAP is chosen for use right after delivery, there are several methods by which it can be administered, including via face mask or nasal prongs, and with the use of a bag or T- piece resuscitator. • The use of a T-piece resuscitator allows the exact pressure to be easily set and maintained at a desired CPAP level, as long as the delivery device (prongs or mask) is properly set-up. • CPAP cannot be administered with a selfinflating bag.

Success with NCPAP NCPAP is successful when meticulous attention is paid to both the infant and to the NCPAP Delivery System. This involves vigilance in: • Monitoring the infant’s condition • Maintaining an optimal airway • Maintaining a patent CPAP delivery circuit • Prevention of complications which may arise from NCPAP

Complications • Malpositioned or displaced prongs. • Obstruction by secretions. • Local irritation and damage to nares and septum. (good oral hygiene e.g. with lemon glycerine swabs or saline should be considered to prevent drying) • Air trapping. • Air leaks. • Hypotension. • Increased ICP • Bowel distension (CPAP Belly)

CPAP belly

Severe nasal snubbing

Columella necrosis (A) Progressing to absent Collumella at 3 months(B)

Progressive flaring of nostrils, circular distortion of nares and flattening of alar ridges after prolonged flow driver continuous positive airway pressure at three months.

DOES NASAL CPAP INCREASE THE RISK OF AIR LEAK? • A randomised trial of early prophylactic CPAP versus oxygen alone showed no difference in the incidence of air leak. • No results on the incidence of air leak are yet available from randomised controlled trials comparing early CPAP with mechanical ventilation.

Contraindications •

• • •

Infants who have progressive respiratory failure and are unable to maintain oxygenation, PCO2<60, pH>7.25. Certain cong. malformations (diaphragmatic hernia, choanal atresia) Severe cardiovascular instability. Poor or unstable respiratory drive that is not improved by CPAP.

Determining optimal levels of CPAP • No simple and reliable method of finding the optimal level has been found. • If the infant has stiff lungs or low lung volumes, increasing the distending pressure improves oxygenation up to about 8 cm H2O. • Increasing pressure increases carbon dioxide retention, although often by not very much, so there is a trade off between improving the oxygenation and a rise in the carbon dioxide concentration.

• The Cochrane review of nasal CPAP at extubation suggested a level of 5 cm H2O or more was more effective than lower levels.

To determine the CPAP or PEEP pressure: • Look at the chest X-ray picture. Do the lungs look collapsed or oedematous, or well expanded? High or low pressures may be required depending on the problem. • If oxygenation is the main problem increase the distending pressure. • If carbon dioxide retention is the main problem reduce the distending pressure. • Start at 4–5 cm H2O and gradually increase up to 10 cm H2O to stabilise the oxygenation while maintaining a pH > 7.25 and PaCO2 < 8.0 kPa.

Weaning from CPAP • The optimal method remains unanswered. • Infants who require an FiO2>0.4 or are clinically unstable are unlikely to be successfully weaned off. • Although some units try abrupt discontinuation of NCPAP, most wean by gradually decreasing either time spent on CPAP or the CPAP pressure.

What new things do we know about nasal CPAP for neonates? • Short double prongs are more effective than single prongs for delivering nasal CPAP. • Nasal CPAP is effective for the post-extubation support of preterm infants. • NIPPV is a useful method for augmenting nasal CPAP. • NCPAP can be used as primary treatment for RDS.

What questions remain? • Does early nasal CPAP for RDS reduce mortality and morbidity when compared with intubation for very preterm neonates? • Can more effective and less traumatic nasal CPAP devices and methods of fixation be developed? • What is the most effective source of pressure for CPAP? • What is the optimal pressure level and how can this be judged? • How should babies be weaned from CPAP?