How To Set Up A Ven.lator: Standard Versus High Pressure Dean R. Hess PhD RRT Assistant Director of Respiratory Care MassachuseBs General Hospital Associate Professor of Anesthesia Harvard Medical School Editor in Chief RESPIRATORY CARE
Standard Versus High Pressure COPD: correct gas exchange abnormality Neuromuscular disease: prevent gas exchange abnormality (ALS)
Noninvasive Ven.la.on Hill NS, Braman S. 1999. Noninvasive ven.la.on in neuromuscular disease. In: Cherniack NS, Altose MD, Homma I, eds. Rehabilita/on of the Pa/ent with Respiratory Disease. New York, NY: McGraw- Hill.
Lungs Normal Bendi<, Respir Care 2006;51:829
Indica.ons for NIV Symptoms (fa.gue, dyspnea, morning headache, orthopnea, abdominal paradox, accessory muscle use) and one of: PaCO 2 45 mm Hg Nocturnal SpO 2 88% for 5 consecu.ve min For progressive neuromuscular disease, PImax > - 60 cm H 2 O or VC < 50% predicted Supine VC lower than upright VC with diaphragm paralysis Chest 1999;116:521
No mention of settings Neurology 2009;73:1218
Muscle Nerve 46;2012:313 It is reasonable to begin with 8 cm H 2 O IPAP and 4 cm H 2 O EPAP. Increase IPAP to alleviate symptoms, or select ini.al pressure based on improvement in day.me ABG and oximetry together with pa.ent comfort. Pressures should be.trated to comfort or day.me ABG. Increases in IPAP of 2 cm H 2 O are reasonable for each adjustment. Increased NIV requirements are likely with.me; breathing comfort should be assessed serially.
Lancet Neurol 2006;5:140 NIV was ini.ated in hospital with pressure support in spontaneous/.med mode. Inspiratory and expiratory airway pressures were adjusted for op.mum nocturnal oximetry breathing room air, day.me arterial blood gases, and mean dura.on of NIV use per 24 h. The mean IPAP and EPAP reached was 15 cm H 2 O and 4 cm H 2 O, respec.vely, and the maximum was 24 cm H 2 O and 5 cm H 2 O, respec.vely.
Equation of Motion normal respiratory mechanics. P + P = V/C + R V MUS AW 0.5 L/(0.1 L/cm H 2 O). P + P = V/C + R V = PS 6 cm H MUS AW 2 O 2 cm H 2 O/L/s x 0.5 L/s EPAP 4 cm H 2 O, IPAP 8-10 cm H 2 O
How to Choose NIV Settings Empiric Short-term symptoms: comfort, accessory muscle use Long-term symptoms: less morning headache, daytime fatigue, and daytime sleepiness Physiologic: tidal volume, gas exchange SpO 2, PETCO 2, PTCCO 2 Polysomnography Long wait time Sleep labs less familiar with NMD than OSA Overnight oximetry Does not assess sleep quality
NIV Sefngs for ALS Back- up rate (periodic breathing with REM) Trigger, cycle, rise.me per pa.ent comfort EPAP: 4 cm H 2 O (low as possible unless OSA) IPAP: 8 15 cm H 2 O as tolerated; may need higher sefngs with acute illness, or as disease progresses Ramp off Unclear role for newer modes like AVAPS
NIV Sefngs for ALS FIO 2 : room air unless acute illness Humidity: rou.ne Inhaled bronchodilators and steroids not necessary Nasal symptoms: mouth leak, humidity, OTC remedies, nasal steroids, and an.cholinergics
Issues With Higher Pressure Poorer tolerance Greater leak Asynchrony Periodic breathing
The Ven.lator for NIV Bilevel PSV/PCV Passive circuit Intermediate PS, PC, VC Ac.ve or passive circuit Cri.cal care Dual limb circuit Many modes
Humidifica.on Necessary for comfort and to avoid drying of upper airway secre.ons Ar.ficial nose (HME)? Less effec.ve Requires bidirec.onal flow Decreased effec.veness with leak Branson and Gentile, Respir Care 2010;55:209
Sancho, Amyotroph Lateral Scler Frontotemporal Degener 2014;15:55
Sancho, Amyotroph Lateral Scler Frontotemporal Degener 2014;15:55
Eur Neurol 2008;59:164
Average Volume Assured Pressure Support (AVAPS) IPAP Pressure.. Volume Desired Volume IPAP Pressure.. Volume Desired Volume
Equation of Motion Adaptive Pressure Modes decreased pressure. P + P = V/C + R V MUS AW increased effort tidal volume and flow constant
The effect of adding an HME exchanger to augment circuit dead space was assessed with a same fixed level of PSV and APC. PTPdi, cm H 2 O x s 18 16 14 12 10 8 6 4 2 Dead space off Dead space on Work of Breathing (J/min) 18 16 14 12 10 8 6 4 2 Dead space off Dead space on 0 Pressure Support Ven.la.on Adap.ve Pressure Control 0 Thorax 2012;67:663 Pressure Adap.ve Support Pressure Ven.la.on Control Jaber, Anesthesiology 2009;110:620
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Summary Evidence support the use of NIV for neuromuscular respiratory failure. Goal is to support respiratory func.on and prevent gas exchange abnormality. Modest pressures are usually sufficient to accomplish this goal.