CURRENT TRENDS IN NON-INVASIVE VENTILATION. Disclosures. Why not invasive ventilation? Objectives. Currently available modes

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1 CURRENT TRENDS IN NON-INVASIVE VENTILATION Karen Drinkard, RRT-NPS Neonatal Respiratory Clinical Specialist University of Washington Medical Center Disclosures This speaker has no financial or other conflicts of interest to report. Objectives Why not invasive ventilation? Currently available modes of CPAP and NIV Bubble CPAP why it s back NIV NAVA completely synchronous noninvasive ventilation Potentially responsible for increasing odds of chronic lung disease (VON) Bypasses natural heat/humidity system Bypasses natural infection defenses, allowing bacteria a super-highway to lungs (VAP) Why non-invasive ventilation? Currently available modes Able to assist or meet infant s inspiratory demand without placement of an artificial airway, if patient is spontaneously breathing CPAP Airlife (or equivalent) stand-alone ncpap device CPAP via ventilator Bubble CPAP 1

2 Airlife (or similar) stand-alone CPAP Currently available modes Non-invasive SiPAP (or equivalent) stand-alone NPPV via ventilator NIV NAVA Generates necessary flow to achieve set (desired) CPAP Some devices can sense baby s expiratory effort and adjust flow to allow for adequate exhalation Airlife at end-of-life Limited alarms, mostly disconnect CPAP via ventilator Set desired CPAP level Depending on brand of ventilator, may vary flow or use set flow to achieve CPAP Full alarm package available (high/low CPAP, disconnect, apnea) Bubble CPAP Developed in the 80s, fell out of favor and is now enjoying renaissance. For years (decades?), hospitals using Bubble CPAP created their own Bubble CPAP systems Several brands of BCPAP systems now available, enabling hospitals to ensure consistency between patients Because BCPAP can be made cheaply by hospitals, it is ideal for use in third world countries for premature babies Bubble CPAP Maintains set CPAP with constant flow, but heavily reliant on adequate seal of nares Bubbling from expiratory chamber thought to add CO 2 clearance capabilities from oscillations on chest wall If bubbling is not sufficient, or is absent, patient does not have adequate seal, and thus does not have correct CPAP No alarms, must rely on physiologic monitoring Bubble CPAP Single patient use Compatible with nasal prongs, nasal masks, and (sometimes) cannulas May use chinstraps or nasal protective/sealing products to assist with maintenance of positive pressure If water accumulates in chamber, above max fill level, CPAP will be higher than set If water drops below minimum fill level, CPAP will be lower than set 2

3 SiPAP or other stand-alone device NPPV via ventilator Delivers CPAP with additional, higher positive pressure at a rate chosen by practitioner Flow is set Unable to synchronize with patient effort Less expensive device when compared to ventilators with full invasive/non-invasive modes Represents psychological step-down for parents/families when ventilator is removed and SiPAP is brought in Uses proprietary nasal masks or prongs Like SiPAP, ventilators deliver a set PEEP with a higher pressure (PIP) delivered at a rate chosen by practitioner Does not synchronize with patient effort (inability to trigger) Still seemingly effective, whether due to positive pressure aiding with CO 2 clearance or providing noxious stimulation to baby Many hospitals use effectively NPPV via ventilator Can be delivered using most common infant ventilators without purchasing extra devices Full alarm package, including high/low PEEP, high/low PIP, disconnect May not allow for restful sleep due to dissynchrony with patient effort Potentially ties up expensive medical equipment that could be used for other intubated patients What is NAVA? NAVA stands for : Neurally Adjusted Ventilatory Assist To simplify, NAVA is smart pressure support ventilation with a sensitive, synchronized trigger mechanism. Important NAVA Terminology Edi: Electrical Activity of the Diaphragm; measured in microvolts Edi Peak: Maximum contraction of the diaphragm (maximum electrical activity) The Respiratory Drive Edi Min: Minimum contraction of diaphragm/diaphragm at rest; helps maintain recruitment (residual capacity in lungs) and stent open airways Edi waveform/signal: The graphical representation of the Edi Peak and Edi Min activity; will look like a sine wave; as important to assess as the numbers themselves. 3

4 Respiratory Cycle 1. CNS 2. Phrenic nerve 3. Diaphragm excitation Drive to Breathe What causes us to take our next breath? How does our body choose what rate and volume we need? 4. Diaphragm contraction 5. Negative pressure in chest cavity causes movement of air into the chest (flow/pressure change) Drive to Breathe CO 2!! If CO 2 is rising: We hyperventilate ( RR) We yawn ( volume) If CO 2 is falling: We slow our breathing down We breathe more shallowly Our bodies have a sophisticated blood gas machine built-in, and we regulate our CO 2 breath-to-breath Triggering Breaths Conventional Vent CNS Phrenic nerve Diaphragm excitation Diaphragm contraction Negative Pressure in chest trigger Pressure and Flow changes at airway Triggering Breaths Conventional Vent Leaks in the ventilator system, even small ones, can affect how well the ventilator is able to sense the pressure or flow change generated by the patient. Even if no leaks are present, the patient still needs to be able to generate a sufficient pressure or flow change to tell the ventilator they want a breath, which can be difficult when the patient is sick. If patient cannot trigger vent successfully, ventilator cannot synchronize. Secretions or water in the tubing can cause false triggers Triggering Breaths Conventional Vent Even if we can achieve perfect synchrony, and the ventilator doesn t miss a single patient effort, there are still two important comfort issues 4

5 Triggering Breaths Conventional Vent Even if we can achieve perfect synchrony, and the ventilator doesn t miss a single patient effort, there are still two important comfort issues The rate the patient is choosing to breathe is still subject to the volume or pressure that the practitioner sets! Triggering Breaths Conventional Vent Even if we can achieve perfect synchrony, and the ventilator doesn t miss a single patient effort, there are still two important comfort issues Unless we re in Pressure Support, the ventilator will give a breath even if the patient doesn t want one! How NAVA Works How NAVA Works Sensitive, synchronized Trigger mechanism Triggering Breaths NAVA Triggering Breaths NAVA CNS Phrenic Nerve Diaphragm Excitation Ventilator Responds Because the ventilator is directly triggered by the patient s diaphragm, leaks in the system don t affect the patient s ability to trigger The ventilator can be triggered regardless of whether the patient has an ETT or nasal mask/prongs Even the smallest, wimpiest efforts can be supported Auto-triggering is eliminated 5

6 How is Electrical Activity Detected? - The Tip of the catheter should rest in the stomach, no further - Can Feed, Flush, Aspirate, Medicate - Secure and manage like any other NG / OG Optimal Placement 1 reference electrode (closer to heart) 4 electrodes above diaphragm 1 electrode at diaphragm 4 electrodes below diaphragm Edi Catheter (NAVA Catheter) 3 catheter sizes 6 Fr / 49 cm ( 1500g) 6 Fr / 50 cm (1500g 2500g) 8 Fr / 100 cm ( 2500g) Verifying Correct Placement How NAVA Works Sensitive, synchronized Trigger mechanism Variable Pressure Support, entirely dictated by baby s drive to breathe Access this screen by selecting the Neural Access Key, then choosing Edi Catheter Positioning. Variable Pressure Support Conventional Ventilation: Practitioner sets pressure or volume Practitioner sets minimum respiratory rate Practitioner sets I-time Variable Pressure Support The pressure provided to the baby will vary breath to breath, based on the size of the baby s effort. Instead of selecting a set pressure (or volume) that the baby gets with every single breath, we dial in a NAVA level. The NAVA level is a multiplier, or a proportionality constant. NAVA Ventilation: Variable pressure support (we proportionally assist) Variable rate Baby chooses, unless apneic Variable I-time Baby chooses 6

7 Proportional Support Variable Pressure Support The pressure provided to the baby will vary breath to breath, based on the size of the baby s effort. Instead of selecting a set pressure (or volume) that the baby gets with every single breath, we dial in a NAVA level. The NAVA level is a multiplier, or a proportionality constant. The NAVA level determines how much pressure (in cmh 2 O) the ventilator gives the patient per mcv of electrical activity. Since the electrical activity generated by the baby s diaphragm differs from breath to breath, so does the pressure delivered. NAVA level x (Edi Peak Edi Min) = Pressure Support given Variable Pressure Support Another way to say this is the amount of work the diaphragm does (Δ Edi) multiplied by the set NAVA level equals the amount of assistance the baby is getting above PEEP. This means, if the baby works harder (generates larger electrical signals), NAVA will respond with larger pressures. If the baby is breathing peacefully, NAVA responds with smaller pressures. Example of Variable Pressure Edi Peak = 10 mcv Edi Min = 2 mcv NAVA level = 2.0 cmh 2 O / mcv (10 2) x 2.0 = 16 cmh 2 O (Pressure Support above PEEP) If PEEP = 5, then P peak = 21 cmh 2 O (16 + 5) Or, when we increase the NAVA level, the vent is doing more work and the baby is doing less. When we decrease the NAVA level, the baby is doing more work and the vent is doing less. Example of Variable Pressure Edi Peak = 10 mcv Edi Min = 2 mcv NAVA level = 2.0 cmh 2 O / mcv (10 2) x 2.0 = 16 cmh 2 O (Pressure Support above PEEP) If PEEP = 5, then P peak = 21 cmh 2 O (16 + 5) Edi Peak = 5 mcv Edi Min = 2 mcv NAVA level = 2.0 cmh 2 O / mcv (5 2) x 2.0 = 6 cmh 2 O (Pressure Support above PEEP) If PEEP = 5, then P peak = 11 cmh 2 O ( ) x 1.5 = 9.6 cmh 2 O (Pressure Support above PEEP) PEEP = 6, so P peak = 16 cmh 2 O ( ) 7

8 Knowing the Correct NAVA Level Knowing the Correct NAVA Level Normal Edi Peak = 5 15 mcv The higher the Edi Peak, the more the diaphragm is working. To normalize an Edi Peak that s out of range, adjust the NAVA Level. Normal Neonatal Edi Min = 0 4 mcv The higher the Edi Min, the more the baby is using their diaphragm to keep their lungs inflated between breaths. To normalize an Edi Min that s out of range, adjust the PEEP. Babies typically have a higher average Edi Min than adults because their accessory musculature usually isn t developed enough to keep their lungs expanded without additional effort from the diaphragm. We also factor in: 1.What the baby looks like! (Is the baby comfortable or working hard to breathe?) 2.The Saturation and the FiO 2 3.The BP and the Heart Rate 4.Blood gases may not need as many blood gases, since Edi Peak and Min values will give immediate indications of effectiveness of ventilation 5.Tidal Volumes (if intubated) 6.Trend values * Backup Ventilation Backup Ventilation If the baby doesn t breathe for longer than the set apnea time, the ventilator will kick in with pressure supported breaths at the pressure, rate, and I-time we set. It will continue providing breaths until the baby s own diaphragm kicks back in (an Edi signal returns). At that time, it seamlessly switches back to NAVA ventilation. NAVA(Backup) will also begin if the catheter becomes malpositioned. It will continue in backup, with an Edi Catheter alarm, until the catheter is back in position. Anything that affects the Edi signal will trigger NAVA(Backup) support. As the baby becomes more stable, we can wean the apnea time (stretch it out) and challenge them. Managing NAVA Managing NAVA To affect ventilation: NAVA level For Avg Edi Peak > 15mcV NAVA level For high CO 2 Consider NAVA level For Avg Edi Peak < 5mcV NAVA level (?) For low CO 2 Consider NAVA level To affect oxygenation: PEEP and FiO 2 For Avg Edi Min > 4mcV PEEP For Avg Edi Min < 2mcV consider weaning PEEP or do nothing 8

9 Managing NAVA Typical ranges for NAVA settings: FiO 2 : PEEP: 4 10 cmh 2 O NAVA level: cmh 2 O/mcV (Invasive) cmh 2 O/mcV (NIV NAVA) Backup Rate: bpm Backup I-time: seconds Backup PC above PEEP (ΔP): set so PC + PEEP equals avg. PIP delivered when patient is in NAVA Apnea Time: 2 15 seconds Limitations / Indications Limitations Not all patients can successfully use NAVA Patients requiring sedation Septic patients Patients with under-developed or affected drive to breathe Works well for some premature infants, not others Works well for some full-term infants, not others Ties up expensive ventilator Difficult to create protocol for weaning/increasing settings Indications Who does NAVA work well for? Patients who can manage their CO2 / Drive to Breathe Patients weaning from the ventilator Patients who may be difficult to extubate due to structural airway issues, who otherwise could breathe on their own Patients who need non-invasive support, greater than CPAP New study shows NAVA may be beneficial for BPD patients: Theoretical Benefits of NAVA Summary 1. Synchrony: Ventilator does not mandate breaths unless the baby becomes apneic. This is true both invasively and non-invasively. 2. Seamless transitions between NAVA and Backup (full support) when baby is apneic: Can fully support them and potentially prevent some of their bradycardias and desaturations. 3. Improved comfort/rest: Because the breaths are synchronized to the baby s effort, the baby doesn t have to fight the vent. The baby may sleep more comfortably and/or require less sedation. 4. Less air in the belly: Because breaths are only delivered when the baby is asking for them, the glottis will be open. More air can enter the trachea and less air may be forced into the stomach. 5. Weight gain: The baby is expending fewer calories to initiate breaths, so they are potentially better able to gain weight. Conventional ventilation still has an important place in the care of critically ill infants (as does High- Frequency ventilation, CPAP, and High Flow Oxygen ) Any CPAP or NIV device can provide patient with beneficial, non-invasive support that assists in the pursuit of decreasing CLD Learn what devices your institution has, and how to best manipulate the settings for patient comfort and CO 2 clearance 9

10 Questions? Karen Drinkard, RRT-NPS 10