acute respirtaory distress syndrome

ACUTE RESPIRTAORY DISTRESS SYNDROME

ACUTE RESPIRATORY DISTRESS SYNDROME

• Define ARDS (Primary & Secondary)• Stages of ARDS• Lung Protective Ventilation• Prone Position / ECMO


Acute Respiratory Distress Syndrome (ARDS) is defined as a:

“syndrome of acute and persistent lung inflammation with increased vascular permeability” (Hansen-Fletcher et al)


Clinically, ARDS is characterized by:

• acute onset (< 48 hours)• bilateral infiltrates• PaO2/FiO2 ratio

<300mmHg• No evidence of cardiac

causes


ARDS can be caused by direct injury to the lungs (primary) or indirect injury (secondary)


PneumoniaPulmonary ContusionsAspirationInhalation Injuries


SepsisBurnsOverdosesBlood TransfusionsFat Embolisms


Lung injury creates an immune & inflammatory response. The alveolus fill with protein-rich edema, WBC, RBC while the hyaline membrane thickens.

This causes:

• ↓PaO2• ↓Compliance• ↑PaCO2• Respiratory Failure


ARDS Mild ARDS

Moderate ARDS

Severe ARDS

ARDS can be mild (200-

300mmHg), moderate

(<200mmHg), or se

vere

(<100mmHg)


• Slow restoration of lung function

Recovery Stage

• 7—21 days• Alteration of lung

tissue• Poor Compliance• Decreased Edema

Proliferative Stage

• 0-7 days• Edema (peaks

048hrs)• Inflammation

Exudative Stage

Furthermore, ARDS has three stages:


Unfortunately, some patient can develop with pulmonary fibrosis.


ARDS

Direct ARDS

Indirect ARDS

Mild ARDS

Moderate ARDS

Severe ARDS

Lets review:

ARDS is classified by its cause: direct or indirect lung injury.

Its severity: mild, moderate and severe.

Its stages: exudative, proliferative and recovery.


ARDS

Mechanical Ventilation

Ventilator Associated Lung Injury

Immune & Inflammatory

Response

Worsening ARDS

Cycle of Injury: Mechanical ventilation can worsen ARDS and cause long-term disability (ie: pulmonary fibrosis)

ARDS patient frequently require mechanical ventilation.

How can this be a problem?


How can mechanical ventilation worsen ARDS?

Barotrauma: too much pressure (>35mmHg)

Atelectotrauma: collapse and expansion of the alveoli

Volutrauma: too much tidal volume


Lung Protective Ventilation

Small Tidal Volumes (VT)

High Respiratory

Rate

Minimize Airway Pressures (PIP &

PLT)

Adequate PEEP

Lung protective ventilation attempts to prevent volutrauma, barotrauma and atelectotrauma with:


Small tidal volume & high respiratory rate

Adequate PEEP

PEAK Pressure <35-40


PaO2<60mmHg PaCO2>80mmHgPH <7.1 Peak >45cmH20

What if lung protective ventilation fails?


Lung Protective Ventilation

Prone Positio

n

ECMO

Rescue Therapy: • Prone Position• VV-ECMO


The Prone Position:

• Improves perfusion to the lungs → Better V:Q matching• The diaphragm drops and the heart shift forward → Improved compliance• Improved lung recruitment • Lung Protective• Indicated:

• Moderate to Severe ARDS• Early (<48hours)• Duration: 12 – 16 hours


VV-ECMO:

• Provides oxygenation and removal of CO2• Allows the lung to rest (breaking the cycle of lung injury)• Blood movement is facilitated by an external pump• Indicated:

• Early (<7days)• Severe ARDS


In review:

• The prone position may be beneficial early (<48hours) in moderate to severe ARDS

• VV-ECMO may be indicated in severe ARDS when conventional therapy has failed.


(1) Hansen-Flaschen, J., Siegel, M. (2009). Acute respiratory distress syndrome: definition; epidemiology; diagnosis; and etiology. Up to Date

(2) NIH-NHLBI ARDS Network (www.ards.net)

(3) Fessler, H., Talmor, D. (2010). Should prone position be routinely used for lung protective during mechanical ventilation?. Respiratory Care. 55(1); 89-98

(4) Capital District Health Authority, Prone Positioning/Proning. #CC45-075

(5) Guerin, C., Reignier, J., Richard, JC., Beuret, P., Gacouin, A., Boulain, T., Mercier, E., Badet, M., Mercat, A., Budin, O., Clavel, M., Chatellier, D., Jbar, S., Rosselli, S., Mancebo, J., Sirodot, M., Hilbert, G., Bengler, C., Richecoeur, J., Gainner, M., Bayle, F., Boudin, G., Laery, V., Girard, R., Baboi, L., Ayzac, L.(2016). Prone position in severe acute respiratory distress syndrome. New England Journal of Medicine, 368, 2159-2168

http://www.ards.net/

Extras:Acute Respiratory Distress Syndrome:https://www.youtube.com/watch?v=cVCvYxVxSt4

Lung Protective Ventilation:https://www.youtube.com/watch?v=5hdpBRMdZ9M

https://www.youtube.com/watch?v=cVCvYxVxSt4



https://www.youtube.com/watch?v=5hdpBRMdZ9M



acute respirtaory distress syndrome

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