This document discusses ventilation strategies for a patient with acute respiratory distress syndrome (ARDS). It provides details of the patient's initial presentation and management, including mechanical ventilation settings. It describes the rationale for using low tidal volume ventilation to minimize ventilator-induced lung injury. The patient required aggressive management for sepsis and hypoxemia including recruitment maneuvers and increasing PEEP and mean airway pressures. Despite these efforts, the patient could not be weaned from high FiO2 and developed multi-organ failure and died. The document recommends using low tidal volumes, limiting end-inspiratory pressures, adequate PEEP, and considering recruitment maneuvers to optimize ventilation in ARDS.

1. Ventilation Strategies in ARDS MICU-ER Joint Conference Dr. Rachmale, Dr. Prasankumar 12/3/08

2. Initial ICU Management EGDT implemented, CVP- Subclavian line placed, Initial CVP= 8 , Lactic Acid- 5.5 CVP aim > 12, Map > 65  IV fluids 3L, Urine output >0.5ml/kg/hr Antibiotics- zosyn/ ciprofloxacin within one hour Initial ABG: pH: 7.19 Po2: 60 Pco2: 48, sat 84% At this time Ventilator setting: AC/TV-400/RR-28/FiO2 100%/PAP-36/PLP-30/ peep- 7 Pao2/Fi02:60

3. ARDS- Definition 1. PaO2/FiO2 ≤ 200 2. Bilateral (patchy, diffuse, or homogeneous) infiltrates consistent with pulmonary edema 3. No clinical evidence of left atrial hypertension ( PCWP<18)

4. NIH-NHLBI ARDS Network Cause of Lung Injury NHLBI ARDS Clinical Trials Network. N Engl J Med. 2004.

5. Mortality from ARDS ARDS mortality rates - 31% to 74% The main causes of death are non-respiratory causes (i.e., die with, rather than of, ARDS). Early deaths (within 72 hours) are caused by the underlying illness or injury, whereas late deaths are caused by sepsis or multi-organ dysfunction

6. Stages of ARDS

7. RATIONALE FOR LOW STRETCH VENTILATION Lung injury from: Over-distension/shear - > physical injury Mechanotransduction - > “biotrauma” Repetitive opening/ closing Shear at open/ collapsed lung interface “ atelectrauma” “ volutrauma”

8. ARDSNET- Initial Ventilator Strategies Low Tidal Volume (6ml/kg) Calculate predicted body weight (PBW) Males = 50 + 2.3 [height (inches) – Females = 45.5 + 2.3 [height (inches) -60 ] Plateau Pressure < 30 cms

9. Minimizing VILI- Plateau pressure goals If Pplat > 30 cm H2O : decrease VT by 1ml/kg steps (minimum = 4 ml/kg) If Pplat < 25 cm H2O and VT< 6 ml/kg , increase VT by 1 ml/kg until Pplat > 25 cm H2O or VT = 6 ml/kg

10. Mortality: low vs. traditional tidal volume Low tidal volume Traditional tidal volume RRR=22 % ARR=8.8 % NNT=12 p=0.007 ARDSNet. NEJM 2000;342:1301.

11. PEEP in ARDS Protective effect by avoiding alveolar collapse and reopening Prevent surfactant loss in the airways  avoid surface film collapse Use of PEEP avoids end-expiratory collapse, thus Recruitment is obtained at end-inspiration Lower PEEP/Higher FiO2 FiO2 .3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0 PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 18-24

12. Recruitment Maneuvers Improve hypoxia Recruitment of nonaerated lung units (collapsed alveoli)- caudal and dependent lung regions in patients lying supine Maneuvers – short-lasting increases in intrathoracic pressures Intermittent increase of PEEP On AC mode or through ambu bag with PEEP valve Continuous positive airway pressure (CPAP) Cahnge back up rate and apnea alarm Increasing the ventilatory pressures ~ 50 cm H 2 O for 1-2 minutes Intermittent sighs or Extended sighs Can cause Hypotension, pneumothorax, Needs Experience

13. Management of Our patient Initial ABG: pH: 7.19 Po2: 60 Pco2: 48, sat 84% At this time Ventilator setting: AC/ TV-400/ RR-28 /FiO2 100%/PAP-36/PLP-30/ peep – 10 sat 84% Initial changes made: AC/ TV-400/ RR-35 /FiO2 100%/PAP-36/PLP-30/ peep- 17 sat 94% Recruitment Needed

14. Management continued After transfer to MICU, episodes of hypoxia despite maximal mechanical ventilation Improved with recruitment maneuvers Next 48 hours : Vt decreased to 370 then 320, PEEP increased to 20 then 22 , plateau pressures 34-37 on 100% FiO2 Even such Low Vt, unable to maintain plateau pressures below 30 Permissive Hypercapnia

17. Management continued Severe sepsis  septic shock, apache 38 Aggressive hydration, Vasopressor (Levophed) to maintain MAP>65, fixed dose vasopressin, hydrocortisone and xigris ( Activated Protein C) given Lactate remained high, SvO2: 70-77% BC – Strep pneumonia-

18. Hospital Course During entire 25 day course Fio2 requirements could not be lowered to less than 80%, the least PEEP was 14 Peak and plateau pressure remained high Septic shock  MSOF  death

19. Alternative strategies Prone Positioning- recruitment of posterior lung fields High frequency oscillatory ventilation (HFOV)- low tial volumes at high frequences Nitric oxide- selective vasodilator of vessels that perfuse well ventilated lung zones Extracorporeal membrane oxygenation (ECMO )-Veno-arterial bypass which supports gas exchange and oxygenation

20. Limited VT 6 mL/kg PBW to avoid alveolar distension End-inspiratory plateau pressure < 30 cm H 2 O Adequate end expiratory lung volumes utilizing PEEP and higher mean airway pressures to minimize atelectrauma and improve oxygenation Consider recruitment maneuvers Summary of Recommendations