management of persistent hypoxemic respiratory failure in the icu garpestad
TRANSCRIPT
Management of Persistent Hypoxemic Respiratory Failure
in the ICU
Erik Garpestad, M.D.
Director, MICU
Tufts Medical Center
Case Presentation
• 73 yo male underwent elective laporscopic surgery for lyses of abdominal adhesions.
• Surgery went well, pt extubated post-op without difficulty.
• POD# 1 pt developed abdominal pain, fever, hypotension requiring reoperation for peritonitis related to bowel perforation
Case: persistent hypoxia
• For septic shock, pt started on EGDT, 3 pressor agents, VC ventilation with 6 ml/kg of IBW, PEEP 10 cm H20, FiO2 of 100%
• ABG 7.10/46/53
• RR increase, PEEP increased 15-18 cm H20 but ABG with minimal improvement
Persistent Hypoxemia
• What are your options?
• How do you balance need to improve oxygen exchange and optimize oxygen delivery vs lung protective strategy
• These goals are not mutually exclusive
Persistent Hypoxemia
• Increase FiO2, increase PEEP• Recruitment maneuvers• Prone positioning• NO• Ventilator strategies: Lung protective and Open
lung approach• APRV• HFOV
Benefits of Mechanical Ventilation
• Improved oxygenation
• Decreased work of breathing
Risks of Mechanical Ventilation
• Barotrauma
• Biotrauma
• Baby lung
• Cyclic atelectasis
Minimizing MV Risks
• What pressures to measure?
• What modality to use?
• Is there a safe PIP?
• Is there a safe plateau pressure?
• How do you set optimal PEEP?
Ventilator Strategy
• Low tidal volume strategy
• Open lung strategy
Other Ventilator Strategies
• APRV
• HFOV
• TGI
• ECMO
Discussion
• What do you do to decrease risks?
Ware, L. B. et al. N Engl J Med 2000;342:1334-1349
Radiographic and Computed Tomographic (CT) Findings in the Acute, or Exudative, Phase (Panels A and C) and the Fibrosing-Alveolitis Phase (Panels B and D) of Acute Lung Injury
and the Acute Respiratory Distress Syndrome
ARDS: Mechanical Ventilation
• Traditional approach:– Normalize blood gases– High minute ventilation– High tidal volumes– High inflation pressures
ARDS: Mechanical Ventilation
• Maintain adequate oxygenation (PaO2 of 55-80 mmHg or SaO2 of 88-95%
• Avoid oxygen toxicity
• Employ PEEP
• Prevent ventilator induce lung injury
• Minimize barotrauma and volutrauma
Ventilator Induced Lung Injury
• Volutrauma:– Overdistention, physical injury– Biotrauma
• Atelectrauma:– Repetitive opening/closing– Shear forces at open/collapse lung interface
Barotrauma
Tobin, M. J. N Engl J Med 2001;344:1986-1996
Lung Injury Caused by Mechanical Ventilation in a 31-Year-Old Woman with the Acute Respiratory Distress Syndrome Due to Amniotic-Fluid Embolism
Tobin, M. J. N Engl J Med 2001;344:1986-1996
Respiratory Pressure-Volume Curve and the Effects of Traditional as Compared with Protective Ventilation in a 70-kg Patient with the Acute Respiratory Distress Syndrome
ARDS: ARDS Network Trial
• Largest randomized trial to date
• Compared traditional mechanical ventilation (15 ml/kg, plateau < 50 cm H2O) to lower tidal volume (6 ml/kg, plateau < 30 cm H20)
• Trial stopped after 861 pts because mortality was lower in low Vt pts, 31% vs 39.8%, p=0.007 (NEJM 2000;342:1301)
The Acute Respiratory Distress Syndrome Network, N Engl J Med 2000;342:1301-1308
Summary of Ventilator Procedures
The Acute Respiratory Distress Syndrome Network, N Engl J Med 2000;342:1301-1308
Main Outcome Variables
The Acute Respiratory Distress Syndrome Network, N Engl J Med 2000;342:1301-1308
Probability of Survival and of Being Discharged Home and Breathing without Assistance during the First 180 Days after Randomization in Patients with Acute Lung Injury and the
Acute Respiratory Distress Syndrome
ARDS: Mechanical Ventilation
• What mode of ventilation to use?– Either volume cycled ventilation or pressure
cycled ventilation can be used– Choosing appropriate goals for mechanical
ventilation is more important than mode– Target Vt of 6 ml/kg and plateau pressure less
than 30 cm H2O
ARDS: Mechanical Ventilation
• After starting at Vt of 6 ml/kg and keeping plateau pressures < 30 cm H2O:– adjust PEEP. Can use ARDSNet protocol– if FiO2 > 0.6, lengthen inspiratory time or
consider IRV– adequate sedation if permissive hypercapnea is
a consequence of ventilatory strategy
ARDS: Mechanical Ventilation
• ARDSnet established the benefit of small tidal volumes (4-8 ml/kg predicted ideal body weight) ventilation on ALI/ARDS mortality
• Active debate continues over level of PEEP and the use of recruitment maneuvers
ARDS: PEEP
• Improves oxygenation
• Recruits atelectatic lung and prevents alveolar collapse
• Increases FRC
• Improves lung compliance
• Assists in minimizing VILI
Pressure Volume Curve in ARDS
LIP
Volume
Pressure
UIP
1
2
3
1 2 3
1
2
3
1
2
3
Too much VT
Too littlePEEP
PEEP 5
PEEP 10 PEEP 15PEEP 5
By keeping intrathoracic pressure positive throughoutthe respiratory cycle atelectatic lung can be re-expandedor recruited. Shunt decreases and PaO2 increases.
PaO2 = 60 PaO2 = 100 PaO2 = 220
ARDS: What is optimal level of PEEP?
• Amato et al (NEJM 1998) used an “open-lung” strategy. PEEP (1st 36 hrs) in conventional ventilation was 8.7 and in protective ventilation was 16.4 cm H2O.
• Mortality difference 72% vs 38%
• However, patients who received higher PEEP levels also received lower Vt.
Amato M et al. N Engl J Med 1998;338:347-354
Actuarial 28-Day Survival among 53 Patients with the Acute Respiratory Distress Syndrome Assigned to Protective or Conventional Mechanical Ventilation
ARDS: What is optimal level of PEEP?
• NIH ARDS Clinical Trials Network looked at Higher vs Lower PEEP in ARDS patients
• 549 pts with ALI or ARDS randomly assigned to low PEEP (mean on day 1-4 was 8.3 + 3.2 cm H2O) vs high PEEP (mean 13.2 + 3.5 cm H2O)
• No significant difference in mortality, vent free days, ICU-free days or Organ failure.
The National Heart, Lung, and Blood Institute ARDS Clinical Trials Network. N Engl J Med 2004;351:327-336
Summary of Ventilator Procedures in the Lower- and Higher-PEEP Groups
The National Heart, Lung, and Blood Institute ARDS Clinical Trials Network. N Engl J Med 2004;351:327-336
Probabilities of Survival and of Discharge Home While Breathing without Assistance, from the Day of Randomization (Day 0) to Day 60 among Patients with Acute Lung Injury and ARDS,
According to Whether Patients Received Lower or Higher Levels of PEEP
The National Heart, Lung, and Blood Institute ARDS Clinical Trials Network. N Engl J Med 2004;351:327-336
Main Outcome Variables
ARDSnet High/Low PEEP trial
Potential Concerns:
• Plateau pressures in both groups not dangerously high and importance of PEEP is likely to depend on plateau pressure
• Baseline imbalances in age at randomization
• Recruitment maneuvers not used
ARDS: Recruitment maneuvers
• Strategy of using a sustained, high pressure breath to recruit or open atelectatic lung
• No standard method. For example: Sustain single inflation at CPAP of 35 cm H2O for 60 seconds. Monitor SaO2 and BP
• Need to use higher PEEP after maneuver: go to 20 cm H2O and then decrease sequentially by 2.5 cm until dec SaO2
Borges J et al. N Engl J Med 2006;355:319-322
Computed Tomographic Images Obtained at the End-Expiratory Pause in a Patient with Pneumocystosis and the Acute Respiratory Distress Syndrome
Gattinoni L et al. N Engl J Med 2006;354:1775-1786
Enrollment and Study Protocol
Gattinoni L et al. N Engl J Med 2006;354:1775-1786
Frequency Distribution of Patients According to the Percentage of Potentially Recruitable Lung (Panel A) and CT Images at Airway Pressures of 5 and 45 cm of Water from Patients with a Lower
Percentage of Potentially Recruitable Lung (Panel B) and Those with a Higher Percentage of Potentially Recruitable Lung (Panel C)
ARDS: Open Lung Approach
• To determine if the use of lung recruitment maneuvers and a decremental PEEP trial along with small Vt results in lower mortality in severe established ARDS than the original ARDSnet protocol
ARDS: Open Lung Approach
• Intubated, ventilated, ARDS criteria met
• Initial 12-36 hrs, pts will be ventilated per ARDSnet protocol
• Reassessment of oxygenation, PaO2/FiO2 still <200 for pt to be randomized
• Pts randomized to ARDSnet protocol and Open Lung Approach
ARDS: Open Lung Approach
• Lung recruitment procedure:– PEEP 25 cm H2O, PCV 15 cm H2O (Peak
airway pressure 40 cm H2O) for 5 breaths– PEEP 25, PCV 20 for 5 breaths– PEEP 30, PCV 20 for final 20 breaths
• Decremental PEEP procedure: decrease in 2 cm H2O steps until the maximum compliance is identified
ARDS: Permissive Hypercapnia
• Allowing respiratory acidosis improves our ability to use lower tidal volumes and airway pressures
• May require sedation, or even paralysis
• Contraindicated in pts with increased ICP
ARDS: Inverse Ratio Ventilation
• Increase I:E ratio from 1:3 to 1:1 or more
• Increasing inspiratory time improves oxygenation without increasing pressures
• Watch for dynamic hyperinflation or worsening hemodynamics
ARDS: Prone positioning
• Improves oxygenation but no change in mortality (NEJM 2001;345:568)
• Not routinely recommended
• Consider use early in course of ALI/ARDS in patients requiring high PEEP and FiO2.
• Try recruitment maneuvers first
Supine Prone
Dependent Atelectasis
ARDS: Supportive Care
• Fluid management– maintain intravascular volume at lowest level
that allows for adequate perfusion
• Nutrition– enteral feedings when possible
• Prophylaxis– for DVT and GI bleeding
The National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network. N Engl J Med 2006;354:2213-2224
Kaplan-Meier Estimates of the Probability of Survival and of Survival without the Need for Assisted Ventilation during the First 60 Days after Randomization
The National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network. N Engl J Med 2006;354:2564-2575
Probability of Survival to Hospital Discharge and of Breathing without Assistance during the First 60 Days after Randomization
ARDS: Pharmacological Therapy
• Antibiotics
• Neuromuscular blockade
ARDS: Pharmacological Therapy
• Corticosteroids– No benefit early in course of ALI/ARDS– Have been used in fibrosing-alveolitis phase of
ARDS– Consider short course in pts with severe disease
that have prolonged course and not improving (Meduri, JAMA 1998;280:159)
ARDS: Pharmacological Therapy
• Inhaled nitric oxide– may improve oxygenation and PVR, but only
transiently. No improvement in outcome
• Inhaled surfactant– no outcome improvement
ARDS
• Mechanical Ventilation of 6 ml/kg and maintain plateau < 30 cm H20
• Lowest FiO2 that maintains adequate oxygenation
• Titrate PEEP
• Supportive care
Alternative Methods of Ventilatory Support
• Airway pressure release ventilation
• High-Frequency Ventilation
Case presentation
• 73 yo male underwent elective laporscopic surgery for lysis of abdominal adhesions.
• Surgery went well, pt extubated post-op without difficulty.
• POD# 1 pt developed abdominal pain, fever, hypotension requiring reoperation for peritonitis related to bowel perforation
Case: persistent hypoxia
• For septic shock, pt started on EGDT, 3 pressor agents, VC ventilation with 6 ml/kg IBW, PEEP 10 cm H20, FiO2 of 100%
• ABG 7.10/46/53
• RR increase, PEEP increased 15-18 cm H20 but ABG with minimal improvement
Case: Persistent hypoxemia
• Inhaled NO was started
• APRV: Hi-PEEP 32, low-PEEP 15, FiO2 of 100%. ABG 7.24/32/63
• HFOV: Mean airway pressure 32, frequency 5 Hz, set oscillation pressure for “Movement of torso from clavicle to mid thigh”. ABG 7.23/31/65
What is APRV?
• An “open” ventilator strategy
• Essentially = CPAP + Time Cycled Pressure Release
Habashi NM, crit care med 2005: 33(3S)
APRV Pressure/Flow Diagram
Theoretical Advantages
• Spontaneous Breathing Allows:– Improved Ventilation of Dependent Lung– Less Likely to have alveolar overdistention– Potentially less sedation
• Increased time at high pressures may improve recruitment
Theoretical Advantages
• Pressure Release– Improved TV for given ΔP, utilizes increased
elastic recoil, expiratory limb of PV curve– Less chance of over distension given not
“filling” lung but “emptying”.– Short release time does not allow significant
dercruitment
APRV Settings
• Phigh = CPAP
• Plow = Release Pressure
• Thigh = Time at Phigh
• Tlow = Time at Plow
• Can supplement spontaneous breathing with pressure support
APRV Settings
• Phigh
– Newly Intubated = Desired Pplat– From Conventional Vent = Current Pplat
• Plow
– Suggested setting: 0
• Thigh
– 4-6 secs
• Tlow
– 0.2-0.8 secs
Habashi NM, crit care med 2005: 33(3S)
APRV Settings
• Oxygenation– Decrease Tlow to ensure end-exhaled flow rate is
>50% PEFR and < 75% PEFR– Increase Phigh and/or Thigh
• Ventilation– Assess sedation– Increase Phigh and/or Thigh ( TV)– Decrease Thigh ( Ve)
Habashi NM, crit care med 2005: 33(3S)
APRV Pressure/Flow Diagram
High Frequency Ventilation Modes
From UptoDate, Ostenholzer and Hyzy
Physiology
• Oscillating pressure around a set mean airway pressure
• Higher Mean Pressures increase oxygenation
• Lower peak pressures and in theory small volumes result in no overdistension
From Quissell et al
Increased Mean Pressures = Improved oxygenation
From Mehta et al Critical Care 2001
Ventilation
• Occurs through multiple proposed mechanisms– Direct Conductive– Longitudinal dispersion from turbulence– Pendeluft flow due to varying time constants– Venturi Effect– Diffusion
From UptoDate, Ostenholzer and Hyzy
Gas Transport in HFOV
Case Presentation
• Pt is a 38 year-old man who presents with severe pneumonia and ARDS. The pt is started on conventional ventilation by ARDSnet protocol. Yet despite increasing PEEP to 18, the PaO2 is still 55 on an FiO2 of 1.0 – You are asked to initiate HFOV. What are your
initial settings?
Initial Settings
• Set Mean Pressure at Mean pressure of Conventional Ventilation
• Set Frequency 3-5 Hz
• Set oscillation pressure for “Movement of torso from clavicle to mid thigh”
Case Presentation
• The pt is sedated/paralyzed and placed on HFOV. Mean pressure: 25cmH2O,Frequency 3Hz and FiO2 = 1.0 Initial ABG: – pH = 7.22
– PaCO2 = 60
– PaO2 = 65
– What adjustments would you make to your settings?
Adjustments
• Oxygenation– Mean Pressure– FiO2
• Ventilation (CO2)– Frequency– Oscillation pressure amplitude– Intentional cuff leak
Case
• The frequency is increased to 5Hz and Mean pressure increased to 28cmH2O
ABG: pH = 7.30 PaCO2 = 50 PaO2 = 105
• What complications are associated with HFOV?
Complications
• Similar to conventional ventilation
• Higher Mean Airway Pressures may have more hemodynamic effects
• 90% + pts require paralysis – no rates of post-paralytic syndrome reported in clinical trials
Literature
• Neonates: associated with improved gas exchange and decreased barotrauma. No change in mortality
• Adults: Improved early oxygenation but no other outcome improved
• Can be combined with other modalities to improve oxygenation: Prone, NO
Randomized Trials
• Derdak et al, AJRCCM 2002: Primary outcome safety; No difference in safety c/w conventional ventilation– Mortality secondary outcome
• 37%(HFOV) vs 52% (conv) p=0.10
• Prior to ARDSnet protocol
• Bollen et al; Crit Care 2005: No mortality difference [28% vs 32%]
Demory et al Crit Care Med 2007
Preventing Derecruitment after Proning
Management of Hypoxic Respiratory Failure: Conclusions
Initially employ a lung protective strategy with low tidal volumes with adequate PEEP and monitoring of plateau pressures
Routine use of Open lung approach, high PEEP, recruitment maneuvers, APRV and HFOV continue to be investigated. Select these interventions on case by case basis