ARDS
Acute Respiratory Distress Syndrome
The presence of acute, severe arterial hypoxemia and bilateral pulmonary infiltrates not attributable exclusively to cardiogenic or hydrostatic causes.
Acute Respiratory Distress Syndrome
_______ causes diffuse inflammation process affecting both lungs and arises secondary to another condition.
ARDS
What can cause ARDS to occur?
Injury or infection that has allowed fluid to leak into the interstitium and alveoli.
- Sepsis. The most common cause of ARDS is sepsis, a serious and widespread infection of the bloodstream.
- Inhalation of harmful substances. Breathing high concentrations of smoke or chemical fumes can result in ARDS, as can inhaling (aspirating) vomit.
- Severe pneumonia. Severe cases of pneumonia usually affect all five lobes of the lungs.
- Head or chest injury. Accidents, such as falls or car crashes, can directly damage the lungs or the portion of the brain that controls breathing.
An excess of fluid can cause:
- Impaired gas exchange
- Pulmonary HTN
- Decreased Lung Compliance
What is released in response to lung damage?
Proinflammatory cytokines
What do proinflammatory cytokines do?
Recruit neutrophils
The recruitment of neutrophils and proinflammatory cytokines cause
Pulmonary edema to occur
When there is a loss of functional surfactant, what can happen?
Alveolar collapse
Where there is an intrapulmonary shunting of blood….
There is NO ventilation and therefore severe hypoxemia will occur.
Would 100% O2 help improve health when there is an intrapulmonary shunt?
No
Where there is an impairment of blood flow to the lung, what will happen?
An increase in Alveolar Dead Space due to a lack of healthy vasculature
A decrease in pulmonary compliance would lead to
A decreased inspiratory capacity.
Signs and Symptoms of ARDS
- Progressive Hypoxemia (PaO2/FiO2 < 200)
- Dyspnea
- Tachypnea
- Tachycardia
- Cyanosis
- Rapid Onset 6-48 hours
** Remember in ARDS, no benefit to giving O2
What tests would you do for suspected ARDS?
- CXR
- ABG
- Pulmonary Artery Catheter
- Bronchoscopy
- CT Scan
What are you looking for on a CXR for ARDS?
Bilateral diffuse “fluffy” lung infiltrates
What are you looking for on an ABG for ARDS?
Despite hypoxemia, the ventilation rate remains normal or even increased (bigger respiratory effort from the patient) This actually results in decreased CO2. This effect does not typically last, as patients cannot maintain the increased effort which ultimately results in an increased CO2 (respiratory acidosis)__________________________________________
- Hypoxemia: PaCO2 < 60
- Respiratory Alkalosis initially (PaCO2 < 40), followed by acidosis (later on)
What are you looking for in a Pulmonary capillary wedge?
PCWP < 18 mm Hg would indicated ARDS
What are you looking for in a Bronchoscopy?
- Fluid collection
2. Looking for BAL results!!
What are the BAL results going to show in a bronchoscopy?
- Neutrophils = ARDS
- Eosinophils = Eosinphilic pneumonia
- Lymphocytes = Hypersensitivity pneumonia or COP
Which is the most useful test in distinguishing ARDS from cardiogenic pulmonary edema/CHF?
Pulmonary Capillary Wedge Pressure (PCWP)
DDx for ARDS
- CHF
- Acute Presenting ILD
- Pulmonary Vasculitis
- Acute Hypersensitivity Pneumonia
- Acute Eosinophilic Pneumonia
- AOP
How do you manage/treat a patient that is presenting with Respiratory Distress?
- Treat the underlying cause!
- Get O2 sats > 90%
- Ventilation may be needed to protect the lungs (PEEP). Try to get TV to 6 mL/kg
- Fluid Management
- Supportive Measure
- Alternative Recruitment Management
What will open collapsed alveoli that could cause decreased atelectasis and improve O2 in the body?
PEEP (Positive End-Expiratory Pressure)
