Acute Respiratory Distress Syndrome (ARDS): What You Need to Know - - PowerPoint PPT Presentation

John Gallagher DNP, RN, CCNS, RRT Andrew Rice MSN,CRNA, ACNP-BC

Acute Respiratory Distress Syndrome (ARDS): What You Need to Know Today

Learning Objectives

• Identify current trends in the clinical management of

ARDS during the COVID-19 Pandemic

• Make recommendations for caring for patients with

ARDS during the COVID-19 Pandemic

Coronavirus (COVID-19)

• Novel bat-origin Coronavirus originating in Wuhan,

Hubei, China

– SARS-CoV-2 aka COVID-19

• Patients present with flu-like symptoms

– Sore throat – Cough – Fever – Shortness of breath

COVID-19 Illness Severity

• 81% Mild (no or mild pneumonia)
• 14% Severe disease

– Dyspnea, hypoxia, >50% lung involvement

• 5% critical disease

– Respiratory failure, shock, or multiorgan dysfunction – Uncommon: only 13% need vasoactive agents

COVID-19 Related ARDS

• 3% – 17% COVID-19 develop ARDS
• Late onset dyspnea (6.5 days)
• ARDS develops ~2.5 days after dyspnea
• Risk Factors: age, smoking, comorbidities, fever > 39*C

– Cardiac disease, DM, HTN, lung disease, CKD, cancer, obesity

Lab Findings with Worse Outcomes

• Lymphopenia
• Elevated liver enzymes
• Elevated lactate dehydrogenase (LDH)
• Elevated inflammatory markers (eg, C-reactive protein [CRP], ferritin)
• Elevated D-dimer (>1 mcg/mL)
• Elevated prothrombin time (PT)
• Elevated troponin
• Elevated creatine phosphokinase (CPK)
• Normal procalcitonin with pneumonia, but elevated with ICU admission
• Acute kidney injury

Patient Presentation

• Hypoxemia manifested by low oxygen saturation

worsening with activity (hypoxic vasoconstriction?)

– SpO2 < 90%

• High negative inspiratory effort in spontaneously

breathing patients

• Improvement in oxygenation with invasive positive

pressure ventilation

– Lung compliance may be normal!!

Patient Presentation

• Worsening hypoxemia and lung compliance
• Hypoxic pulmonary vasoconstriction/microemboli

– Elevated D-dimer

• Cardiomyopathy/Myocarditis

– Viral cause – Right ventricular failure related to ARDS and PPV?

ARDS Criteria

PaO2/FiO2 Ratio

Mild* Moderate* Severe* 200 – 300 100 - 200 < 100

• Acute onset (within 7 days)
• Bilateral opacities (CXR or CT)
• Alveolar edema is not related to cardiac failure or fluid overload

– Does not require normal PCWP – Does not require absence of LA hypertension * on CPAP/PEEP > 5 cm H2O

• JAMA. 2012;307(23):2526-2533. doi:10.1001/jama.2012.5669

Radiologic Changes

• Ground glass opacities peripherally and basilar
• Interlobular septal thickening
• Radiologic changed may be seen early in some cases before positive COVID screening

results

• Not recommended: CXR or CT for screening/progression (staff/equipt contamination)

Lung Ultrasound

• Thickened/Irregular pleural line
• Multiple B-Lines
• Subpleural consolidations
• Air bronchograms
• Localized pleural effusion possible

Copetti, R Cardiovasc Ultrasound 2008 B-Lines

COVID-19 Supportive Management

• Prone ventilation (prolonged, avoid early return to supine)
• Conservative fluid therapy (except with sepsis)
• Glucocorticoids?
• Avoid aerosolization procedures (bronchoscopy, nebulizers)
• Critical Care Management: nutritional support, VTE prophylaxis, stress

ulcer prophylaxis, fever management, etc.

• Low intubation threshold

Management of Hypoxemia

• Supplemental low-flow oxygen

– Lowest FiO2 necessary maintain SpO2 90% – 96%

• High-flow nasal Cannula?
• Non-invasive positive pressure ventilation (NIPPV) ?
• Intubation/Invasive PP ventilation

Non-Invasive Strategies

• HFNC

– Aerosol virus

• Mask over the face
• NIPPV

– Aerosol virus

• Filtration of the circuit

Non-Invasive Strategies –CPAP Hood

– High Flow Set Up – Venturi

Decision to Intubate

• Delayed intubation  ↑ risk to patient and HCW
• Low Intubation threshold

– Rapid ARDS progression (hours) – Lack of improvement on >40 L/minute of high flow oxygen and a fraction of inspired oxygen (FiO2) >0.6 – Worsening hypercapnia – Hemodynamic instability or multiorgan failure

Intubation-Preparation

• PPE- Full barrier precautions

– PAPR (powered air purifying respirator) or N-95 mask/faceshield

• Avoid awake intubation (cough aerosolization)
• Most experienced operator/Limit those in the room (Neg press)
• Video laryngoscope (distance and first pass success)
• Novel barrier approaches

https://www.apsf.org/wp-content/uploads/news-updates/2020/apsf-coronavirus-airway-management-infographic.pdf

https://www.nejm.org/doi/full/10.1056/NEJMc20075 89?query=featured_coronavirus Barrier enclosure during endotracheal intubation April 3rd 2020

Intubation

• Goals: Protect staff, successful first attempt, limit aerosolization
• Pre-oxygenate 5 min (passive low-flow ie. nasal cannula)
• RSI intubation – Do Not Mask Ventilate
• Heat Moisture Exchanging Filter (HMEF) between airway and

BVM/Ventilator

• Direct placement on the ventilator

https://www.apsf.org/wp-content/uploads/news-updates/2020/apsf-coronavirus-airway-management-infographic.pdf

ARDS Criteria

PaO2/FiO2 Ratio

Mild* Moderate* Severe* 200 – 300 100 - 200 < 100

• Acute onset (within 7 days)
• Bilateral opacities (CXR or CT)
• Alveolar edema is not related to cardiac failure or fluid overload

– Does not require normal PCWP – Does not require absence of LA hypertension * on CPAP/PEEP > 5 cm H2O

• JAMA. 2012;307(23):2526-2533. doi:10.1001/jama.2012.5669

Zone of ↑ Risk

PLATEAU Driving Pressure PEEP

Alveolar Overdistension

Collapsed Alveoli

Inspiratory phase Expiratory phase

฀ Repeated Alveolar Close and Expansion (RACE)

฀“Milking” of surfactant from alveoli with repeat closure

Lung Protection

Marini, J. (2019) Critical Care, 23 (suppl 1):114

Lung Protective Ventilation Strategy

• Maintain Alveolar Pressure (plateau pressure) < 30 cm H2O

– Low tidal volume ventilation 6 ml/kg of PBW (range 4-8 ml/kg PBW)

• PEEP to prevent end-tidal collapse/recruit

– PEEP start lower (8-10 cm H2O) and titrate up

ARDSNet Protocol

• Low tidal volume
• Prone ventilation

http://www.ardsnet.org/files/ventilator_protocol_2008-07.pdf

Evolution of Mechanical Ventilators

Volume Control Pressure Control

PEEP

A/C SIMV A/C SIMV Support

Dual Control

Ventilation Strategies

• LTVV + PEEP
• Pressure Control Inverse Ratio (PC-IRV) + PEEP
• Volume Targeted Pressure Modes
• Biphasic Ventilation- spontaneous breathing mode

– BiPhasic/BiLevel – Airway Pressure Release Ventilation ( exp time < 1.0 sec)

Volume Targeted (Control)Ventilation (VCV)

• Guaranteed tidal volume with each breath
• Constant flowrate
• Pressure varies based on resistance and compliance of

the lung and chest wall Pressure Flow

Pressure Targeted (Control) Ventilation (PCV)

Fixed inspiratory pressure but Volume is variable

• Inspiratory pressure & inspiratory time
• Airway resistance, lung and chest wall compliance

Pressure Flow

Pressure Control Inverse Ratio (PC-IRV)

50 25 5 I-Time E-Time I-Time

Time Pressure

Auto-PEEP

50 25 5 I-Time E-Time I-Time

Time Pressure

8

Set PEEP Auto- PEEP

P F

• Exp. Flow

50 - 80% of Peak PCV PC-IRV

Auto PEEP Measurement Actual PEEP

Volume Assured Pressure Modes

Pressure Limited + Minimum Volume Guarantee

• aka…

– Adaptive Pressure Control Modes – “Dual Control” Modes

Machine adjusts to changing lung mechanics to provide tidal volume within pressure limit

Volume Assured Pressure Modes

PCV + Volume Target

• Pressure Regulated Volume Control (PRVC)
• Volume Support
• Volume Control Plus (VC+)
• Volume Support
• Pressure Control Volume Guarantee (PCVG)
• Volume Targeted Pressure Control (VTPC)
• Adaptive Pressure Ventilation
• Adaptive Support Ventilation
• Pressure Augmentation

Pressure Flow

Pressure Regulated Volume Control

Points to Remember

• Guaranteed minimum tidal volume but not a constant

tidal volume!!

• Tidal volume may not be achieve if lung compliance

becomes low or pressure limit is set too low

• Excessive tidal volume if the patient generates excessive

inspiratory efforts

Spontaneous Breaths

P

T PEEPHI PEEPLO Spontaneous Breaths PEEPHI

P

PEEPLO

T * * * * * * *

†

†

† Synchronized Transition

†

Spontaneous Breaths

*

APRV BiPhasic

Spontaneous Breaths

P

T PEEPHI PEEPLO

Biphasic Ventilation

Spontaneous Breaths

• Inspiratory Pressure Limit (PEEPHI)
• PEEP (PEEPLOW)
• Inspiratory time (Ti)
• Rate (fx)
• Pressure Support
• Biphasic
• Bi-level
• Bi-Vent
• BIPAP
• Duo PAP

APRV Characteristics

• High CPAP level with a short expiratory releases at set intervals (rate)
• APRV always implies an inverse I:E ratio
• All spontaneous breathing is done at upper pressure level

PEEPHI

P

PEEPLO

T * * * * * * *

†

†

† Synchronized Transition

†

Spontaneous Breaths

*

Alveolar Volumetric Changes in APRV

Insp. Exp. Conventional APRV

• Insp. Exp.

~ ~

Prone Positioning

Zone of Perfusion Zone of Ventilation

Prone for 12-16 hours In moderate to severe ARDS

Pulmonary Vasodilators

• Preferential distribution to ventilated alveoli
• Improvement in perfusion to ventilated areas
• Reduce Pulmonary Vascular Resistance (PVR)
• Reduce afterload of the RV

Nitric Oxide

Injection of gas into the distal ventilator circuit (minimize interaction with O2 )

– initial 20-40 ppm – maintain 2-10 ppm Adverse effects – methemaglobinemia – oxidant formation – vasoconstriction/hypoxemia (withdrawal) – possibly renal failure

Cardiovascular Effects of COVID-19

• Chest pain/palpitation
• Dysrhythmias

– Atrial fibrillation – Tachydysrhythmias

• Heart failure
• Cardiomyopathy
• Troponin elevations
• Cardiac Arrest

Chloroquine/Hydroxychloroquine

• Prolonged QT
• Torsades

Lopinavir/Ritonavir

• Prolonged QT and PR interval
• Coadministration with lovastatin
• r simvastatin may result in

rhabdomyolysis

Positive Pressure & RV Afterload

• Myocardial O2 demand
• Reduced Coronary Artery BF (chamber dilation)

PPV/PEEP Alveolar distention

Increased RV afterload

Hypoxic Vasoconstriction Capillary compression

Alveolar collapse

Ventilator Availability

• Critical care vents (fully functional)/BiPap machines
• Use of emergency stockpile and industry production
• Use of Anesthesia machines
• Multiple patients on one machine-significant limitations

Goals of Ventilation

• Familiarity/experience with the chosen mode
• Application/limitations across disease states
• Goals of the chosen strategy
• Lung protection/recruitment/liberation
• Endpoints of success (failure)
• Improved oxygenation/ventilation/compliance

• Patience…..
• Recruitment and improvements may take hours
• Rapidly changing from one mode to another rarely

helpful

• Especially if the team is unfamiliar with it

Goals of Ventilation

Parting Thoughts

• Identify overall patient ventilation goals
• Ensure team familiarity with the chosen mode/strategy
• Lung protection and recruitment early rather than Rescue
• Patience.. Improvement may be gradual
• Anticipate and prepare for associated complications
• Monitoring change in patient parameters is everyone’s

responsibility

Resources

• AANA

– https://www.aana.com/aana-covid-19-resources

• APSF

– https://www.apsf.org/novel-coronavirus-covid-19-resource-center/

• SCCM

– https://www.sccm.org/disaster

• Center for Disease Control (CDC)

– https://www.cdc.gov/

• https://online-learning.harvard.edu/course/mechanical-ventilation-

covid-19