Evidence-Based Approach to Mechanical Ventilation of the Patient with Hypoxemic Respiratory Failure

Educational Objectives

The goal of this program is to improve the management of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS). After hearing and assimilating this program, the clinician will be better able to:

1. Optimize tidal volumes in patients with ARDS.

2. Set appropriate levels of positive end-expiratory pressure in patients with ARDS.

3. Treat refractory hypoxemia in patients with ARDS.

Summary

Noninvasive respiratory support: necessary to exercise care in use of noninvasive ventilation for patients in acute hypoxemic respiratory failure; high-flow nasal cannula probably has role; Bellani et al (2017) investigated probability of survival for patients with ratio of Pao2 to Fio2 (PF ratio) <150 who received noninvasive or invasive ventilation; survival significantly lower in patients receiving noninvasive ventilation; no difference in survival for patients with PF ratio ≥150; Frat et al (2015) showed that high-flow nasal cannula associated with higher survival compared to standard oxygen therapy or noninvasive ventilation in patients with acute hypoxemic respiratory failure caused by pneumonia; survival lower with noninvasive ventilation than with standard therapy

Assessment: necessary to carefully assess patient’s response to therapy over first few hours after initiation of noninvasive ventilation or high-flow nasal cannula; escalate therapy as needed if patient fails to respond

Selection of tidal volume: Acute Respiratory Distress Syndrome Network et al (2000) compared tidal volumes of 12 mL/kg to 6 mL/kg in >800 patients; study stopped early for benefit; lower tidal volume arm targeted plateau pressure ≤30 cm H2O; small tidal volume arm had 25% reduction in mortality; tidal volume based on ideal body weight (IBW) or predicted body weight (PBW), not actual body weight; Needham et al (2012) showed 18% relative increase in mortality for each 1 mL/kg IBW increase in tidal volume; speaker states beneficial to use ≤6 mL/kg as target for tidal volume in patients with acute respiratory distress syndrome (ARDS)

Bellani et al (2016): evaluated management of patients with ARDS in 50 countries; fewer than two-thirds of patients with ARDS received tidal volume ≤8 mL/kg IBW or PBW; plateau pressures measured in only 40% of patients

Tidal volume in patients without ARDS: accumulating evidence suggests small tidal volumes also beneficial for patients without ARDS; Neto et al (2015) conducted systematic review and individual patient analysis; higher tidal volumes associated with higher percentage of pulmonary complications; increase in tidal volume associated with nonsignificant increase in in-hospital mortality; accumulating evidence suggests tidal volume 6 mL/kg beneficial for all intubated and mechanically ventilated patients, with or without ARDS; normal tidal volume in healthy people 6 or 7 mL/kg of IBW

Pressure-based ventilation with spontaneous breathing: patient on pressure-based mode of ventilation (eg, pressure support, pressure control) is making vigorous inspiratory effort as ventilator delivers breath; negative intrapleural pressure from inspiratory effort combined with positive pressure from ventilator creates large alveolar stretch (difference between pressure inside and outside lungs); stretch and injury to lungs potentially larger than applied pressure might suggest; Brochard et al (2017) stated importance of ascertaining whether spontaneously breathing patient has high respiratory drive and has adopted ventilatory pattern that may lead to injury to lungs; researchers coined term “patient self-inflicted lung injury”

Setting positive end-expiratory pressure (PEEP): consider amount of potential recruitment of lungs; Gattinoni et al (2006) showed percentage of recruitable lung variable in patients with ARDS; some patients in intensive care unit have harmful response to PEEP, and some have beneficial response; 3 randomized controlled trials found no difference in outcomes with higher or lower levels of PEEP in patients with ARDS; increasing PEEP in nonrecruitable lungs can cause overdistention of alveoli and lead to high plateau pressures; risk of injury outweighs benefit of higher PEEP; increasing PEEP with compliant lungs can lead to recruitment of alveoli and cause only small increase in plateau pressure; in this case, benefit exceeds potential for injury

Studies: Walkey et al (2017) published meta-analysis comparing high and low PEEP in patients with ARDS; suggestion of lower mortality with higher PEEP did not reach statistical significance overall; Briel et al (2010) performed individual patient meta-analysis; showed higher survival with higher PEEP in patients with moderate to severe ARDS (PF ratio <200) and higher survival with lower PEEP in patients with mild ARDS (PF ratio between 200 and 300); potential for recruitment greater with more severe ARDS

How to set PEEP: no compelling evidence for superiority of any single approach; Gattinoni et al (2015) suggest “best” PEEP does not exist; “better” PEEP involves compromise among oxygenation, hemodynamics, and intratidal opening and closing of alveoli; suggest PEEP between 15 and 20 cm H2O for patients with severe ARDS, between 10 and 15 cm H2O for moderate, and between 5 and 10 cm H2O for mild ARDS

Writing Group for the Alveolar Recruitment for Acute Respiratory Distress Syndrome Trial Investigators et al (2017): compared aggressive recruitment maneuvers and higher levels of PEEP with lower PEEP; patients who received higher PEEP had worse outcomes; authors concluded strategy of recruitment and titrated PEEP increased 28-day all-cause mortality in patients with moderate to severe ARDS

Driving pressure: difference between plateau pressure and PEEP; Amato et al (2015) showed decreasing mortality with decreasing driving pressure; speaker suggests targeting driving pressure <15 cm H2O

Permissive hypercapnia: Nin et al (2017) showed odds of mortality increased when Paco2 decreased below normal or increased above normal in patients with moderate or severe ARDS; odds of dying with Paco2 >70 mm Hg higher compared with Paco2 <30 mm Hg; speaker would still allow Paco2 to increase if necessary to avoid injurious tidal volumes; data suggest benefit for maintenance of normal Paco2 when possible

Refractory hypoxemia: evidence supports neuromuscular blockade and prone positioning; weak evidence for extracorporeal membrane oxygenation (ECMO) and airway pressure release ventilation (APRV); evidence does not support inhaled pulmonary vasodilators (eg, nitric oxide, aerosolized prostacyclin) or high-frequency oscillatory ventilation; Narendra et al (2017) published algorithm for consideration of various therapies for patients with PF ratio <150

Fan et al (2017): published clinical practice guideline for mechanical ventilation in adult patients with ARDS; strong recommendation for mechanical ventilation using tidal volumes between 4 and 8 mL/kg PBW or IBW and plateau pressure <30 cm H2O, and for prone positioning for >12 hr/day in severe ARDS; conditional recommendation for higher PEEP and recruitment maneuvers in patients with moderate or severe ARDS (these need to be reconsidered in light of recent data); recommendation against routine use of high-frequency oscillatory ventilation in patients with moderate or severe ARDS; no recommendation related to ECMO

Questions and answers: use of inhalational agents for pulmonary hypertension possibly has role in cardiac setting, but not well studied; no studies support superiority of APRV to prone positioning

Readings

Amato MB et al: Driving pressure and survival in the acute respiratory distress syndrome. N Engl J Med 2015 Feb 19;372(8):747-55; Bellani G et al: Epidemiology, patterns of care, and mortality for patients with acute respiratory distress syndrome in intensive care units in 50 countries. JAMA 2016 Feb 23;315(8):788-800; Bellani G et al: Noninvasive ventilation of patients with acute respiratory distress syndrome. insights from the LUNG SAFE study. Am J Respir Crit Care Med 2017 Jan 1;195(1):67-77; Briel M et al: Higher vs lower positive end-expiratory pressure in patients with acute lung injury and acute respiratory distress syndrome: systematic review and meta-analysis. JAMA 2010 Mar 3;303(9):865-73; Brochard L et al: Mechanical ventilation to minimize progression of lung injury in acute respiratory failure. Am J Respir Crit Care Med 2017 Feb 15;195(4):438-42; Brower RG et al: Higher versus lower positive end-expiratory pressures in patients with the acute respiratory distress syndrome. N Engl J Med 2004 Jul 22;351(4):327-36; Fan E et al: An official American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline: mechanical ventilation in adult patients with acute respiratory distress syndrome. Am J Respir Crit Care Med 2017 May 1;195(9):1253-63; Frat JP et al: High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. N Engl J Med 2015 Jun 4;372(23):2185-96; Gattinoni L et al: Selecting the ‘right’ positive end-expiratory pressure level. Curr Opin Crit Care 2015 Feb;21(1):50-7; Mercat A et al: Positive end-expiratory pressure setting in adults with acute lung injury and acute respiratory distress syndrome: a randomized controlled trial. JAMA 2008 Feb 13;299(6):646-55; Narendra DK et al: Update in management of severe hypoxemic respiratory failure. Chest 2017 Oct;152(4):867-79; Needham DM et al: Lung protective mechanical ventilation and two year survival in patients with acute lung injury: prospective cohort study. BMJ 2012 Apr 5;344:e2124; Neto AS et al: Lung-protective ventilation with low tidal volumes and the occurrence of pulmonary complications in patients without acute respiratory distress syndrome: a systematic review and individual patient data analysis. Crit Care Med 2015 Oct;43(10):2155-63; Nin N et al: Severe hypercapnia and outcome of mechanically ventilated patients with moderate or severe acute respiratory distress syndrome. Intensive Care Med 2017 Feb;43(2):200-8; Walkey AJ et al: Higher PEEP versus lower PEEP strategies for patients with acute respiratory distress syndrome. a systematic review and meta-analysis. Ann Am Thorac Soc 2017 Oct;14(Supplement_4):S297-S303; Writing Group for the Alveolar Recruitment for Acute Respiratory Distress Syndrome Trial Investigators et al: Effect of lung recruitment and titrated positive end-expiratory pressure (PEEP) vs low PEEP on mortality in patients with acute respiratory distress syndrome: a randomized clinical trial. JAMA 2017 Oct 10;318(14):1335-45.

Disclosures

For this program, the following has been disclosed: Dr. Hess is a consultant for Philips Respironics and Ventec Life Systems. The planning committee reported nothing to disclose. In his lecture, Dr. Rountree presents information related to the off-label or investigational use of a therapy, product, or device.

Acknowledgements

Dr. Hess was recorded at the 8th Annual State of the Science Symposium: Critical Care Best Practices, held December 9, 2017, in Miami, FL, and presented by Baptist Health South Florida. For information about upcoming CME opportunities from Baptist Health South Florida, please visit baptisthealth.net/en/physicians/pages/continuing-medical-education.aspx. The Audio Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

AN603102

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.