ASRD DSA Flashcards
What measures can be taken to prevent the progression of ARDS and prevent morbidity and mortality?
- Transferring to high level of care (ICU) sooner
- ID predisposing syndromes
- Initiate ICU measures.
Acute respiratory distress syndrome can be distinguished from other causes of respiratory distress by a(n) __________
Inciting event
The Berlin Definition of Acute Respiratory Distress Syndromes (ARDS)
- Timing
- Chest imaging
- Oxygenation
- Mild
- Moderate
- Secere
Timing: within 7 days of precipitating cause or onset of new/worsening respiratory symptoms
Chest imaging: Bilateral diffuse airway infiltrates that cannot be explained by anything else (cardiac failure or volume overload). If predisposing cause is not present, run echo to exclude hydrostatic edema
Oxygenation:
- Mild: PaO2 (less than or equal to 300) with PEEP or CPAP greater than or equal to 5cm H20
- Moderate: PaO2 (less than or equal to 200) with PEEP greater than or equal to 5cm H20
- Severe: PaO2 (less than or equal to 100) with PEEP greater than or equal to 5cm H20
The hypoxia that occurs in the acute respiratory distress syndrome (ARDS) is a result of
Ventilation-perfusion mismatch
What are the most common causes of ARDS?
Pulmonary and nonpulmonary sepsis
How do we differentiate ARDS from other causes of respiratory diseases that cause hypoexemia?
ID inciting event.
How long does it take from for the inciting event to cause ARDS?
3-5 days
What can patients with ARDS experience that is EXTREMLY worrisome and if noticed, needs medical attention.
- Hypercapnia (high CO2) in the face of tachypnea.
What are common predispoing causes of ARDS that involve DIRECT injury to the lungs?
- 1. Pneumonia
- 2. Gastric aspiration
- 3. Chest trauma/lung contusion
- 4. Inhalation injury
- 5. Near drowning
What are common predispoing causes of ARDS that involve INDIRECT injury to the lungs?
- Nonpulmonary sepsis
- Acute pancreatitis
- Severe nonchest trauma
- Blood transfusions
- Surface burns
In ARDS, as hypoxemia requires higher amounts of inspired supplimental O2, what does this suggest?
Evolving acute lung injury with worsening ventilation-perfusion (V/Q) mismatching and worsening shunt physiology.
When should we give a patient with ARDS endotracheal intubation?
- Altered mental status
- Hypercapnia
As ARDS worsens, what changes do we see on chest radiography?
Patchy infiltrates become more confluent
In general, how does ARDS cause acute respiratory failure?
- Increase in permeability d/t direct injury or inflammation
- Decrease lung compliance that fucks up gas exchange.
If we think the patient has coexistant or predomina,nt HF what tests should we run to rule other causes and confirm diagnosis of ARDS?
- 1. Echo
- 2. CT
- 3. Pulmonary artery catherization
The pathophysiology of ARDS involves 2 stages: exudative stage and proliferative stage. Describe the exudative stage.
-
Exudative stage: Predisposing injury damages the aveolar-capillary barrier, causing it to loose its ability to limit fluid, proteins and debris from vascular space,
- Type 1 pneumocytes support alveoli and fluid/solute transport through aquaporin 5 protein.
- Type 2 pneumocytes can differentiate into type 1 and make surfactant
- Injury to type 1 disrupts barrier in acute exudative phase.
- Injury to type 2 => atelectasis and worse compliance.
- Forms a proteinaceous edema by moving fluid from plasma space => institial sub-compartment.
- Worsening V/Q mismatch
- Physiologic shunt
In the early phase of ARDS, what dominates the clinical picture?
- 1. Shunting
- 2. Hypoxemia
How does atelectasis affect the lungs in ARDS?
Requires higher pressures to maintain alveoli so that we can breathe.
What worsens dead space ventilation?
- Increase in pulmonary arterial pressure d/t hypoexmia causing pulmonary a vasoconstriction
- Decrease in pulmonary circulation d/t microthrombi
- Both worsen dead space ventilation and cause increase work of breathing.
The pathophysiology of ARDS involves 2 stages: exudative stage and proliferative stage. Describe the proliferative stage.
- Proliferative stage: Type 2 pneumocytes regnerate surfactant and type 1 rebuild epithelium.
- If repair goes well: recover from ARDS in 7-21 days.
- If procollagen 3 is depostited in interstitial space + fibrosis => increase risk for morbidity and mortality => pt needs prolonged mechanical ventiliation.
- -As vascular changes that occur in phase 1 becomes irreversible => pulmonary HTN occurs.
How do we diagnose ARDS?
Based on clinical criteria and exlusion of other diseases.
What can our differentials be for a patient that presents with ARDS?
Acute infectious pneumonias. like:
- Pneumocytis jivoveci pneumonia
- Community acquired bacterial pneumonia
Similar CXR and refractory hyoxemia, but without cellular toxicity.
These can also cause ARDS
Patients with ARDS have to work harder to breathe and ventilate.
How do we often fix hypoxemia?
- Invasive mechanical ventilation.
- Non-invase methods only fix the problem temporarily.
How does mechanical ventilation work?
- Makes it easier to breath by easing resp muscles and improving effective minute ventilation.
- CO2 decreases and acid-base levels are restored.
