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Tailoring the ventilator settings• To improve oxygenation: options include c F iO 2, c PEEPFirst, c F iO 2. If 0.6 and oxygenation remains suboptimal, then try c PEEP:If c P aO 2/F iO 2 and P plat stable, suggests recruitable lung (ie, atelectasis). Continue toc PEEP until either can T F iO 2 to 0.6 or P plat 30 cm H 2O. If PEEP 20 & F iO 2 1.0and oxygenation remains suboptimal, consider rescue/expt strategies (see ARDS).If c PEEP S ∅ or T P aO 2/F iO 2 or c P aCO 2, suggests additional lung not recruitableand instead overdistending lung Scshunt & dead space; ∴ T PEEP• To improve ventilation: c V T or inspiratory pressure, c RR (may need to T I time). Nb,tolerate c P aCO 2 (permissive hypercapnia) in ALI/ARDS (qv) as long as pH 7.15.Acute ventilatory deterioration (usually c PIP)• Response to c PIP: disconnect Pt from vent., bag, auscultate, suction, ✓ CXR & ABGFigure 2-7 Approach to acute ventilatory deteriorationair leak↓ airway resistancedecreasedPIPincreased (eg, >40)Pnormalnormal increased (eg, >30)PEextrathoracic processMECH VENT 2-21↑ airway resistance = PIP – P [nl 60]asynch breathingauto-PEEPP -PEEPpneumothorax, R-mainstem intubatelectasis, PNA, pulmonary edemaPEVT(Adapted from Marino PL. The ICU Book, 3rd ed., Philadelphia: Lippincott Williams & Wilkins, 2007:467)Weaning from the ventilator• Weaning strategy: spontaneous breathing trial (SBT) for Pts who meet screeningcriteria (qv) better than gradual weaning of PSV or SIMV (NEJM 1995;332:345). Dailyawakening (d/c all sedation; pass if open eyes & w/o: agitation, RR 35, S aO 288%, resp distress or arrhythmias) followed by SBT better than SBT alone(Lancet 2008;371:126).• Identify Pts who can breathe spontaneously (NEJM 1991;324:1445 & 1996;335:1864)screening criteria: sedation reversed, VS stable, minimal secretions, adequate cough,cause of respiratory failure or previously failed SBT reversedvent parameters: P aO 2/F iO 2 200, PEEP 5, f/V T 105, V E 12 L/min, VC 10 mL/kgrapid shallow breathing index (f/V T) 105 predicts failure; NPV 0.95 (NEJM 1991;324:1445)• SBT CPAP or T piece 30–120 min (AJRCCM 1999;159:512)failure if: deteriorating ABGs, c RR, c or T HR, c or T BP, diaphoresis, anxiety• Tolerate SBT S extubation. Fail SBT S ? cause S work to correct S retry SBT qdComplications• Barotrauma and volutrauma (eg, PTX, pneumomediastinum)high PIPs usually safe unless c P plat (30 cm H 2O, but lower better) S alveolar damage• Oxygen toxicity (theoretical); proportional to duration degree of c oxygen (F iO 2 0.6)• Alterations in cardiac output (eg, PEEP can T preload S hypotension)• Ventilator-associated pneumonia (1%/day, mortality rate 30%)typical pathogens: MRSA, Pseudomonas, Acinetobacter, and Enterobacter speciespreventive strategies (AJRCCM 2005;171:388): wash hands, semirecumbent position,non-nasal intub, enteral nutrition rather than TPN, routine suction of subglotticsecretions, avoid unnecessary abx & transfusions, routine oral antiseptic,stress-ulcer prophylaxis w/ ? sucralfate (T VAP, c GIB) vs. H 2RA/PPI, ? silver-coatedtubes (JAMA 2008;300:805)• Laryngealedema: for Pts vent 36 h; ? predicted by cuff leak test. Methylprednisolone 20 mg IVq4h starting 12 h pre-extub STTedema and 50% T in reintubation (Lancet 2007;369:1003)ulceration: consider tracheostomy for patients in whom expect 14 d of mech. vent ST duration mech. vent, T # ICU days (BMJ 2005;330:1243); no benefit to performing at1 wk vs. waiting until 2 wk (JAMA 2010;303:1483)