Underlying Principles of Mechanical Ventilation: An Evidence-Based Approach Ira M. Cheifetz, MD, FCCM, FAARC Professor of Pediatrics and Anesthesiology Chief Medical Officer, Children s Services Associate CMO, Duke University Hospital Chief, Pediatric Critical Care Medicine Duke Children s Hospital Ira.Cheifetz@duke.edu
Learning Objectives To review the data supporting lung protective ventilation for pediatric patients. To discuss the PALICC recommendations for invasive mechanical ventilation. To explore opportunities for future research in the area of pediatric mechanical ventilation.
Preventing Overdistention and Collapse Injury Lung Protective Ventilation V O L U M E Add PEEP Limit VT Limit Distending Pressure Transpulmonary Pressure Courtesy of Neil MacIntyre
Pediatr Crit Care Med, 2015
PALICC: The Experts and Topics Section 1. Definition, incidence, and epidemiology Simon Erickson, Roby Khemani, Lincoln Smith Section 2. Pathophysiology, co-morbidities and severity Mary Dahmer, Heidi Flori, Mike Quasney, Anil Sapru Section 3. Ventilatory support Ira Cheifetz, Peter Rimensberger Section 4. Pulmonary specific ancillary treatment Martin Kneyber, Gerhard Wolf, Bob Tamburro Section 5. Non-pulmonary treatment Martha Curley, Vinay Nadkarni, Stacey Valentine
PALICC: The Experts and Topics Section 6. Monitoring Kit Newth, Guillame Emerlaud Section 7. Noninvasive ventilation Chris Carroll, Sandrine Essouri Section 8. Extracorporeal support Heidi Dalton, Duncan Macrae Section 9. Morbidity and long-term outcomes Scott Watson, Miriam Santschi, Yolanda Lopez
Pediatr Crit Care Med, 20015.
Disclosures: Lack of Pediatric Data In general, there is a low level of evidence for most of the PALICC mechanical ventilation recommendations. Specific recommendations are largely based on the experience with adult ARDS plus consensusbased modification for pediatrics.
Mech Ventilation: Basic Principles Avoid overdistension ( volutrauma ) Avoid / minimize stretch injury (cyclic opening and closing of alveoli; atelectrauma ) Ventilatory strategies that limit tidal stretch of alveoli (e.g., low Vt ventilation, HFV, permissive hypercapnia, etc.) However, definitive data in pediatrics are lacking.
Does the Mode Matter? No outcome data on the influence of mode (control or assisted) during conventional mechanical ventilation. Therefore, no recommendation can be made on the ventilator mode to be used in patients with PARDS. strong agreement (100%; 25/25 experts)
Tidal Volume: Definitive Data?
Tidal Volume: What about Peds? Erickson S, Pediatr Crit Care Med, 2007.
Tidal Volume: What about Peds? Khemani R, Intensive Care Med, 2009.
Relationship Between LIS and Vt Khemani R, Intensive Care Med, 2009.
Relationship Between VFD and Vt Zhu YF, Chin Med J, 2012.
Relationship Between Vt and Survival? Predominant mode: pressure control higher Vt likely related to better lung compliance Lower Vt strategy may have been preferentially applied to those considered to have more severe lung injury Lack of control for uncuffed ETTs and/or volume lost due to distensibility of the circuit (greater for severe lung disease) Observational studies associations only; not cause and effect
What about normal lungs? Gajic O, Crit Care Med, 2004.
PALICC Recommandations: Tidal Volume According to lung pathology and respiratory system compliance, in any mechanically ventilated pediatric patient in controlled ventilation, use tidal volumes in or below the range of physiologic tidal volumes for age/body weight (i.e., 5 8 ml/kg IBW). weak agreement (88%; 22/25 experts) Important note: Ideal Body Weight!
PALICC Recommandations: Tidal Volume Use patient-specific tidal volumes according to disease severity / pathophysiology. Tidal volumes should be 3 6 ml/kg IBW for patients with poor resp system compliance and closer to the physiologic range (5 8 ml/kg IBW) for patients with better preserved resp system compliance. weak agreement (84%; 21/25 experts)
Tidal Volume: Unanswered Questions Should (could) we study optimal tidal volumes for PARDS? If so, what Vt groups? 6 vs. 10? 4 vs. 8? 3 vs. 6? Something else? Primary outcome variable?
Injury is from physical stretch induced by the pressure -- not the pressure itself Ann Int Care, 2011.
Plateau Pressure Erickson S, Pediatr Crit Care Med, 2007.
Plateau Pressure Khemani R, Intensive Care Med, 2009.
Pplat Limitations In the absence of transpulmonary pressure measurements, recommend Pplat 28 cm H2O allowing for slightly higher Pplat (29 32 cm H2O) for pts with increased chest wall elastance (i.e., reduced chest wall compliance). weak agreement (72%; 18/25 experts) Should (could) we study Pplat in pediatrics?
14/0 45/10 45/0 Webb and Tierney, Am Rev Respir Dis 1974.
Overdistension Injury Is Regional
PEEP: Composite Data (Note: is better.) Briel, JAMA, 2010.
PEEP: Composite Data (Note: is better.) Briel, JAMA, 2010.
Airway Pressure (cm H 2 O) Benefit of Higher PEEP Offset by Higher Pplat 30 20 10 6 ml/kg 6 ml/kg Nonrecruitable Injury > Benefit 6 ml/kg Recruitable Benefit > Injury 0 Low PEEP High PEEP High PEEP
PEEP Recommendations Moderately elevated levels of PEEP (10 15 cm H2O) titrated to observed oxygenation and hemodynamic response for severe PARDS. weak agreement (88%; 22/25 experts) PEEP levels greater than 15 cm H2O may be needed for severe PARDS, although attention should be paid to limiting Pplat. strong agreement Should (could) we study optimal PEEP? PEEP values? Primary outcome?
Optimal PEEP? Sutter, New Engl J Med, 1975.
Amato MB, N Engl J Med, 2015.
Amato MB, N Engl J Med, 2015.
Amato MB, N Engl J Med, 2015.
OSCILLATE Trial
OSCILLATE Trial Ferguson Ferguson ND, NEJM, ND, NEJM, 2013. 2013.
HFOV HFOV should be considered for moderate to severe ARDS in whom Pplat > 28 cm H2O in absence of clinical evidence of reduced chest wall compliance. weak agreement (92%; 23/25 experts)
RESTORE HFOV
HFOV per se vs. Current Use of HFOV Am J Resp Crit Care Med, 2015, epub.
Preventing Overdistention and Collapse Injury Lung Protective Ventilation <30 cm H2O nl lung V O L U M E Add PEEP Limit VT Limit Distending Pressure (generally) 5-8 ml/kg IBW Transpulmonary Pressure Courtesy of Neil MacIntyre