management of persistent hypoxemic respiratory failure in the icu garpestad

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