ARDS --------------------------------------------------------------------------------------------------------------------- Ventilator Management Nimesh Mehta, MD Pulmonary and Critical Care Salem Pulmonary Associates AECC vs Berlin ARDS Berlin Definition Ventilator induced lung injury (VILI) in ARDS The goal of ventilatory support in ARDS: Buy time and Protect lungs
The injured lung is more susceptible to iatrogenic injury as a result of mechanical ventilation Barotrauma - result of excess intrathoracic pressure (pneumothorax, subcut. emphysema, pneumomediastium) Volutrauma - Over-inflation as a result of excess volume Atelectotrauma repetitive alveolar collapse and recruitment Biotruama stimulation of inflammatory response resulting from mechanic lung injury giving rise to further cytokine-mediated lung and other organ injury Oxygen toxicity * ATS International consensus conference in intensive care medicine: Ventilator
associated lung injury in ARDS. Am J Respir Crit Care Med 1999; 160(18): 2118- Slutsky AS, Lung injury caused by Mechanical Ventilaton. Chest 1999; 116 (Suppl_1):9S-15S. ARDS Areated Recruitab le Non- recruitable Open Lung Ventilation Strategy First described by
Amato* Use of PEEP to over come lower inflation point and allowing ventilation at more favorable part of volume pressure relationship Use of low tidal volumes to prevent overdistension of air-spaces and to avoid high-end inspiratory pressures or volumes * Amato MBP, et al. Beneficial effects
of the open lung approach in ARDS: a prospective randomized study. ARMA Trial Low tidal Volume Strategy 861 patients randomized to Vt 10-12 mg/kg ideal body weight and plateau pressure 50cmH2O vs Vt 6-8 mg/kg IBW and plateau pressure 30cm H2O ARMA Trial
Low tidal Volume Strategy Decreased mortality by 22% NEJM 2000;342:1301-8. LTVV More evidence Eisner MD, et al. AJRCCM 2001; 164: 231-236 LTVV Adherence to protocol Needham et al. BMJ 2012; 344:2124
When adherence to LTVV fell from 100% to 50% or 0%; two year mortality increased by 4% and 8%; respectively Needham et al. AJRCCM 2015; 191:177 Initial TV of 7 mL/kg PBW was associated with 23% increase in ICU mortality when compared to those receiving tidal volume of 6 mL/kg PBW. Later increases in tidal volume by 1 mL/ kg PBW also resulted in a 15% increase in mortality. Optimal PEEP
Positive end-expiratory pressure should be high enough to shift the endexpiratory pressure above the lower inflection point by 2-3 cm H2O Allows maximal alveolar recruitment Decreases injury by repeated opening and closing of small airways Low PEEP vs High PEEP In hospital Mortality 28 days Mortality Ventilator free days Barotrauma Rescue or adjuvant therapy
ALVEOLI NEJM 2004 LOV JAMA 2008 EXPRESS JAMA 2008 27.5 vs 25.1 (p=0.47) 40.4 vs 36.4 (p=0.19) 35.4 vs 39.0 (p=0.30) ---
32.3 vs 28.4 (p=0.33) 35.4 vs 31.2 (p=0.31) 14.5 vs 13.8 (p=0.50) --- 7 vs 3 (p=0.04) 10 vs 11 (p=0.51) 9.1 vs 11.2 (p=0.33)
6.8 vs 5.8 (p=0.57) --- 12 vs 7.8 (p=0.05) 18.7 vs 34.5 (p < 0.01) PEEP Trials Incremental PEEP Strategy Vs Deremental PEEP Strategy
Combination of PEEP and FiO2 level in incremental or decremental fashion with close monitoring of Mechanics: Compliance, Plateau pressure Gas exchange: SpO2, PaO2, PaCo2, P/F ratio Hemodynamics: HR, BP, CO Optimal PEEP by Tidal Compliance
C = VT / (Pplat PEEP) If using fix VT, then titrate PEEP to lowest Pplat PEEP Stress Index A tool to monitor tidal recruitment and overdistension. During inspiration with constant flow (with volume cycle mode) Resistance is constent
All change in pressure-time curve depends on change in compliance during tidal breath. Pre-requisite Patient sedated and preferably paralysed Constant flow condition Low Vt volume cycle mode Concave downward Potential for recruitment (Increase PEEP) Stress Index Concave upward
Overdistention (Decrease PEEP) PV curve PV curve - Limitations Requires sedation/paralysis No easily available No good correlation between different methods Difficult to identify inflection points Unable to differentiate chest wall and lung compliance
Holzapfel et al, Crit Care Med 1983;11:561 Hickling, AJRCCM 2001;163:69 Pressure-volume curves of individual lung units not known Mergoni et al, AJRCCM 1997; 156:846 Ranieri et al, AJRCCM 1997; 156:1082 Deflation limb may be more useful than inflation limb
Harris et al, AJRCCM 2000; 161:432 Hickling, AJRCCM 1998;158:194 No evidence, other than retrospective case reports Esophageal balloon pressure monitoring Surrogate for pleural pressure Titrating applied PEEP to an endexpiratory transpulmonary pressure (TpPEEP) between 0 and 10 cm H2O
Maintaining an end-inspiratory transpulmonary pressure (Tp Plateau) 25 cm H2O To reduce cyclic alveolar collapse To reduce alveolar overdistension 61 patients assigned to Adjustment of the FiO2 and applied PEEP to achieve specific end-expiratory transpulmonary pressures Adjustment of the FiO2 and applied PEEP according to a tabl e similar to used in ARMA trial
NEJM 2008; 359: 2 Esophageal balloon pressure monitoring Limitations Is it true representation of pleural pressure Single trial to aim to look at only oxygenation
Supine position Weight of mediastinum Heterogeneity of lung pathology Focal rather than global pleural pressure Malpositioning and changing positions. Using merely high PEEP has already shown similar results Approximately trans-pulmonary endinspiratory pressure to 25 cm H2O No evidence base. Recruitment Maneuvers Hodgson C, et al. Recruitment manoeuvers in
ALI. Cochrane Database Sys Rev 2009 7 trials reviewed, total patients = 1170 Fan E, et al. Recruitment maneuvers for ALI: a systematic review. AJRCCM. 2008:178;1156 40 studies, total patients 1185 Recruitment Maneuvers ~ Evidence based ~
Did not differentiate between different RM strategies Improved oxygenation (did not persist) No change in ventilator parameter, except higher PEEP after RM No significant difference on 28th day mortality No statistical difference in risk of barotrauma No significant changes in hemodynamic parameters after an RM. Hypotension (12%) and desaturation (9%) were the most common adverse events Only 1% patients had their RMs terminated prematurely
due to adverse events. Current recommendation: to use after brief disconnection of patient from ventilator. APRV 1. 2. 3. Application of CPAP a relatively high level (Phigh) Time-cycled release phase to lower level of CPAP (Plow) Unrestricted spontaneous breathing is permitted in any phase of respiratory cycle. APRV- Evidence Based Study Study design
Groups Results Rasanen et al. 1991 Prospective Crossover trial 50 pts with ALI/ARDS APRV Vs CMV Lower Sydow et al. 1994
Randomize d controlled trial 18 pts with ALI APRV Vs VCIRV Lower Kaplan LF, et al. 2001 Prospective Crossover trial 12 pts with ALI
APRV Vs PCIRV Lower Putensen Randomize et al. d 2001 controlled trial 30 trauma pts with ALI/ARDS APRV Vs PCV High Varpula et al.
58 pts with ALI/ARDS No Randomize d peak airway pressure Similar oxygenation and hemodynamics peak airway pressure Better oxygenation Similar hemodynamics peak and mean airway pressure Better CO, CVP, Oxygen delivery Lower sedative and NMB CO Less sedative and NMB Less MV and ICU days
Required paralysis in control group for first 3 days diff. in term of gas exchange, sedation needs, ventilator free days and Prone Ventilation Prone Ventilation PROSEVA trial - NEJM 2014 466 patients with severe ARDS undergo prone-positioning sessions of at least 16 hours or to be left in the supine position.
Severe ARDS was defined as PF ratio < 150 with FiO2 > 0.6 with PEEP > 5. Supine Group (n = 229) Prone Group (n = 237) Mortality at 28 days 75 38 < 0.001 Mortality at 90 days
94 56 < 0.001 Vent free days at 28 days 10 14 < 0.001 Vent free days at 90 43 57
< 0.001 Summary Identify ARDS early Low tidal volume aim is 6 mL/kg (not 8 mL/kg) PEEP titration based on FiO2 Recruitable ARDS vs non
Aim to have plateau pressure minimum (not just < 30 cm H2O) with some degree of permissive hypercapnia Decremental PEEP titration PV curve Recruitment Maneuvers good only after any circuit disconnection Esophageal balloon know limitation Rescue therapies: APRV; Prone Ventilation ECMO Questio ns
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