Ventilation Strategies in Newborn Modes of Noninvasive Ventilation

Ventilation Strategies in Newborn

Modes of Non-invasive Ventilation NCO 2 NCPAP Si. PAP NIPPV

Nasal Cannula Oxygen Indications – Initial therapy for infants ≥ 34 weeks with TTNB or pneumonia who have minimal respiratory distress – Resolving BPD – Mild AOP despite caffeine – Post-extubation for infants who are unlikely to tolerate NCPAP (>37 weeks) – Infants who are weaning from NCPAP, but still have O 2 requirement Mechanism: provides degree of CPAP depending on flow rate

NCPAP Indications: – – Initial therapy for infants with RDS, TTNB or pneumonia. Post extubation to maintain FRC. BPD or evolving BPD. Infants with moderate to severe AOP despite caffeine. Mechanism: – Increases FRC by preventing alveolar collapse at end expiration – Stents open the upper airway Guidelines: – Use pressures +4 -8 cm. H 2 O. – Alternate nasal prongs and nasal mask in patients requiring more than 1 week of therapy to change pressure points and avoid cutaneous and mucosal breakdown.

Si. PAP Indications: – Initial therapy in infants with RDS, or infants who have failed NCPAP. – Post-extubation for infants < 28 weeks. – Evolving or established BPD with Fi. O 2 requirement ≥ 50% or significant respiratory acidosis*. – Infants with moderate to severe AOP despite NCPAP.

Si. PAP Mechanism: – Provides bi-level CPAP – Increases FRC by providing periods of high expiratory resistance. – CO 2 removal occurs during the transition from high to low PEEP, proportional to the P difference.

Si. PAP Guidelines: – Provides bilevel CPAP and is asynchronous. – Set CPAP to 4 -6+ based on lung inflation, and PIP +4 above CPAP. – Set rate at 20 -40 bpm – Set Ti at 0. 5 to 1. 0 second – Typical starting settings: Pressures 10/6 x 30 x Ti 1. 0 – Use invasive heated humidification settings

NIPPV Indications: – Initial therapy in VLBW infants with RDS or pneumonia. – Post-extubation for infants < 28 weeks. – BPD or evolving BPD with Fi. O 2 > 50% or significant respiratory acidosis* despite NCPAP. – Infants with moderate to severe AOP despite NCPAP.

NIPPV Mechanism: – Increases FRC by delivery of tidal volume breaths (similar to SIMV). – NIPPV settings are adjusted as on SIMV.

NIPPV Guidelines: – Provides collateral ventilation – Set PEEP to 4 -6+ and PIP at 16 Or 2 greater than PIP on SIMV (max 30) – Set rate 20 -60 bpm. Higher rates are used to mimic PSV. – Set Ti at 0. 4 -0. 5 depending on rate and leak. – Set flow at 6 -10 LPM (lowest flow capable of achieving desired pressures) – Typical starting settings: Pressures 16/6 x v 30 x Ti 0. 5 – Use invasive heated humdification settings

Invasive Ventilation Indications for Mechanical Ventilation: CO 2 retention (PCO 2 > 65 mm. Hg with acidosis). Poor oxygenation – FIO 2 > 60% to maintain sats 85 -94%. Persistent apnea or poor respiratory effort. Significant respiratory distress.

Pressure Control/Pressure Support Most common conventional mode used at CHRCO. Infant receives a fixed number of TCPL SIMV breaths. Additional breaths are supported with pressure support ventilation (PSV). PC and PS levels can be varied independently. Pressure support may be used to overcome the increased work of breathing created by the narrow lumen of the ETT. Since PS breaths terminate at the end of the infant’s inspiration, there is a lower risk of air trapping due to insufficient expiratory time during periods of tachypnea.

PC/PS Initial PC/PS settings – Positive end expiratory pressure (PEEP) 5 -7 cm H 20 – Ti 0. 25 -0. 4 seconds – PC rate 20 -30 (or well below the patient’s spontaneous rate). – PC adequate to give an exhaled Vt 4 -6 m. L/kg. Remember that the PC level ordered = PIP– PEEP. – PS adequate to give an exhaled Vt 4 -6 m. L/kg. Remember that the PS level ordered = PIP– PEEP. – Example: When PC/PS 15 is ordered in a patient receiving a PEEP of 6, the PIP generated is 21 for both the PC and PS breath.

Pressure Support (Automode) Infant triggers a pressure support breath with every spontaneous breath and therefore sets the respiratory rate of the ventilator. A physiologic back up rate (generally 30 -40 bpm) is set to provide a minimum rate should the infant become apneic. This mode is generally used in combination with VG. On PSV, the Ti as well as the rate is determined by the infant. If the infant’s spontaneous rate falls below the set rate, the infant will receive a ventilator breath with a set Ti. PS/VG allows for autoweaning since the level of PS is adjusted as the infant’s lung compliance improves and the infant’s respiratory drive adjusts the rate. It is rare that PS/VG settings need to be changed. Adjustments are generally limited to optimizing PEEP if the infant is spontaneously breathing.

TCPL In infants, PPV is usually pressure-limited and time-cycled. With each breath there is a peak inspiratory pressure (PIP), an endexpiratory pressure (PEEP), and a mean airway pressure (MAP). MAP is the average pressure over the inspiratory plus expiratory phase - “the area under the curve”. Increasing PEEP increases FRC and prevents atelectasis. Prolonging the inspiratory time (Ti) allows more time for expansion of the lungs and is useful to treat widespread atelectasis. High inspiratory flows may injure the lungs. Flows of 5 to 7 L/min are common. Tidal volume is generated by the difference between PIP and PEEP. Tidal volumes of 4 -6 ml/kg are optimal. Oxygenation is controlled by changing the FIO 2 and by increasing the MAP. Respiratory rate is altered by adjusting the inspiratory and expiratory times. Short expiratory times lead to gas trapping within the lung. The minimum expiratory time should not be < 0. 3 seconds. Inspiratory times are usually set at 0. 3 to 0. 4 sec. The expiratory time will then be related to the respiratory rate. For example, if Ti=0. 4 sec and respiratory rate is 60, each respiratory cycle then lasts 1. 0 sec, therefore, the Te will be 0. 6 sec.

Volume Guarantee This mode requires a flow sensor that can accurately detect inspiratory and expiratory volumes of 2 m. L or less. With each breath there is a peak inspiratory pressure (PIP), an endexpiratory pressure (PEEP) and a mean airway pressure (MAP). Unlike TCPL, the PIP can vary between breaths. Prolonging the Ti allows more time for expansion of the lungs and allowing the tidal volume to be delivered at lower pressures. High inspiratory flows may injure the lungs. If the flow is excessive on VG ventilation, the excess flow is diverted from the baby causing a loud humming noise. Flow rates 4 -6 L/min. Ventilation pressures should be monitored continuously. Changes in ventilation pressures occur with changes in lung compliance. Dropping ventilation pressures usually occur during lung recovery. Rising ventilation pressures suggest worsening lung disease, air leak or mechanical issues and require investigation.

Volume Guarantee Tidal volumes (Vt) of 4 -6 m. L/kg are optimal for infant’s > 1000 grams. Vt > 5 m. L/kg are associated with increased risk of air leak and BPD and suggests the need for high frequency ventilation. Oxygenation is controlled by changing the Fi. O 2 and by increasing MAP. On VG, the latter is accomplished by increasing the PEEP. Changes in Vt may or may not result in consistent changes in MAP since the PIP fluctuates from breath to breath. Respiratory rate is altered by adjusting the inspiratory and expiratory times. Short expiratory (Te) times lead to gas trapping within the lung. The minimum Te should not be < 0. 3 seconds. Inspiratory times are usually set at 0. 3 to 0. 4 sec. VG can not be used if the infant has a large (> 40%) leak around the ETT. In the presence of a large leak, the infant will need to be changed to TCPL or re-intubated with a larger tube.

Pressure-Volume Curve

Assist Control (AC) Infant triggers a ventilator breath with every spontaneous breath and therefore sets the respiratory rate of the ventilator. A physiologic back up rate (generally 30 -40 bpm) is set to provide a minimum rate should the infant become apneic. This mode is best used in combination with VG. Initial AC settings – – Positive end expiratory pressure (PEEP) 5 -7 cm H 20 Ti 0. 25 -0. 4 seconds Back up rate 30 -40 PIP adequate to give an exhaled Vt 4 -6 m. L/kg

High Frequency Ventilation There is considerable evidence that ventilation with high frequencies and volumes which are below normal tidal volume, causes less lung injury than does tidal ventilation. Many animal studies have demonstrated that in diseases characterized by atelectasis, such as respiratory distress syndrome, high frequency oscillatory ventilation (HFOV) produces better lung inflation and less alveolar and airway damage than does tidal ventilation. These studies show that HFOV improves gas exchange and reduces pulmonary injury by avoiding the large changes in intrapulmonary pressure and volume necessitated by tidal ventilation. The maximum benefit from non-tidal ventilation occurs when it is instituted before significant lung damage has been caused by tidal ventilation, (ie shortly after birth).

HFOV is the preferred mode for ELBW infants and for moderatesevere diseases which are relatively homogenous. Its role in older infants with non-homogenous disease is less clear. HFOV is indicated for patients with severe restrictive disease where high PIP on conventional ventilation would place the infant at risk for lung injury. HFOV is effective in ventilating patients with pulmonary hypoplasia. HFOV may be superior to conventional ventilation in VLBW infants at high risk of developing BPD on conventional ventilation. Optimizing HFOV settings: – Inspiratory time (Tinsp) 33% – Mean airway pressure (Paw) at least 20% greater than patient was receiving on conventional ventilation. – Frequency 6 -10 Hertz, depending on patient size – Amplitude (delta. P) adjusted based on physical examination (wiggle) and/or TCM for CO 2.

HFJV is indicated for management of patients with PIE or broncho-pleural fistula. The short Tinsp of HFJV minimizes air leak and promotes healing of PIE or BP fistula. HFJV can be used effectively for any restrictive disease (e. g. RDS, pneumonia). HFJV provides excellent ventilation in patients with pulmonary hypoplasia. HFJV may be superior to HFOV or conventional ventilation in some patients with chronic lung disease and air trapping. Initial HFJV settings: – HFJV inspiratory time ( Tinsp) 0. 02 sec – HFJV rate 240 -480 breaths/min (4 -8 Hz) – use lower frequency with PIE or hyperinflation – PEEP 6 -8. Maintaining adequate PEEP is important for success with HFJV – HFJV PIP set 1 -2 cm H 20 below monitored CV – Conventional rate 0 -5 breaths/min (rate 0 -3 if PIE or hyperinflation, 3 -5 if atelectasis is a problem) – Conventional inspiratory time (Tinsp) 0. 3 -0. 5 sec – Conventional PIP 2 -5 cm H 2 O less than HFJV PIP

Complications of Ventilation Vent failure Pulmonary over-expansion Pneumothorax Pneumomediastinum Right mainstem