PANCE Blueprint Pulmonary (10%)

Acute respiratory distress syndrome (Lecture)

Patient will present as → a patient brought to the emergency room with acute onset of dyspnea and tachypnea. He has a long history of alcoholism and was involved in a motor vehicle accident two days ago. He is hypoxic with crackles auscultated bilaterally and frothy pink sputum. Chest radiography reveals diffuse bilateral infiltrates which spare the costophrenic angle and air bronchograms, there is no cardiomegaly or pleural effusion noted. Oxygen saturation is 70%

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Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by fluid collecting in the lungs depriving organs of oxygen

  • The underlying abnormality in ARDS is ⇑ permeability of alveolar-capillary membranes ⇒ development of protein-rich pulmonary edema (non-cardiogenic pulmonary edema)
  • ARDS can occur in those who are critically ill or who have significant injuries

Three clinical settings account for 75% of ARDS cases:

  • Sepsis syndrome (most common cause)
  • Severe multiple trauma
  • Aspiration of gastric contents (alcoholics), toxic inhalation, near-drowning

People with ARDS have severe shortness of breath and often are unable to breathe on their own without support from a ventilator

  • Rapid onset of profound dyspnea occurring 12-24 hours after the precipitating event
  • Tachypnea, pink frothy sputum, crackles

Acute respiratory distress syndrome (ARDS) vs. Hyaline membrane disease/newborn respiratory distress syndrome (RDS) 

  • Hyaline membrane disease/respiratory distress syndrome in preterm infants (RDS) is often due to young gestational age, immature type II alveolar cells, and lack of alveolar surfactant, resulting in inadequate alveolar surface tension during expansion, which results in atelectasis, reduced gas exchange, severe hypoxia, and acidosis.
    • Hyaline membrane disease and RDS are two names for the same thing!
  • Acute respiratory distress syndrome (ARDS) in newborns and children is distinct from RDS/Hyaline membrane disease and involves diagnostic criteria (Montreux standard). Unlike RDS, ARDS of newborns and children is not based on a lack of alveolar surfactant.
  • These diagnostic criteria for ARDS of newborns and children include:
    • Acute exacerbation (within 1 week) after clinical or possible injury
    • Not caused by RDS, transient tachypnea of the newborn (TTN), congenital malformations, atelectasis, local effusions
    • Congenital heart disease that can be explained by pulmonary edema
    • Oxygenation index (OI) value ≥4
The diagnosis of ARDS requires symptoms developing within 1 week, bilateral diffuse infiltrates on chest x-ray, symptoms not being explained by congestive heart failure, and a ratio of PaO2 to FiO2 of less than 300.
  • Chest radiograph shows air bronchograms and bilaterally fluffy infiltrate
  • Normal BNP, pulmonary wedge pressure, left ventricle function, and echocardiogram
An air bronchogram appears when an infiltrate surrounds a peripheral bronchi, and is thus important in establishing lung consolidation.

An air bronchogram appears when an infiltrate surrounds a peripheral bronchus and is thus important in establishing lung consolidation.

Treatment involves identifying and managing underlying precipitation and secondary conditions

  • Tracheal intubation with the lowest level PEEP to maintain PaO2 > 60 mmHg or SaO2 > 90
  • ARDS is often fatal, the risk increases with age and severity of illness

osmosis Osmosis
Acute Respiratory Distress Syndrome (ARDS) Assessment


ARDS is a sudden and progressive failure of the respiratory system in which the alveolar-capillary membrane becomes damaged. Damage to this membrane makes it more permeable to fluid, which can lead to difficulty breathing, atelectasis, and hypoxemia that is unresponsive to oxygen therapy. Patients who develop ARDS are typically afflicted by another illness or injury such as COPD, pneumonia, tuberculosis, aspiration, sepsis, shock, or fluid overload. Patients with this condition may also develop pulmonary hypertension, which is a late indicator of decreased lung compliance.

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Acute Respiratory Distress Syndrome (ARDS) Interventions

Patients with ARDS are at an increased risk for developing renal failure and stress ulcers. Close monitoring of patients for these conditions is essential. Hemodynamic monitoring should also be an important component of care, as these patients may experience hypotension, hypoxemia, and hypercapnia, which can cause negative consequences if left untreated.

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Neonatal respiratory distress syndrome (NRDS)


Neonatal respiratory distress syndrome (NRDS) is a condition related to fetal lung immaturity in premature infants (<37 weeks gestational age) and a lack of surfactant. Infants with NRDS will exhibit signs of respiratory distress including tachypnea, nasal flaring, intercostal/substernal retractions, and audible grunting upon expiration. Interventions used to treat NRDS include administration of exogenous surfactant, oxygen therapy, and mechanical ventilation. It is important to note that infants with NRDS should not receive bottle or gavage feedings, as these may increase their respiratory rate and risk of aspiration. Instead, total parenteral nutrition (TPN) is used to provide the infant with adequate nutrients.

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Question 1
A 32-week preterm infant has an APGAR score of 9 at 5 minutes. Thirty minutes after delivery, tachypnea, retractions, and expiratory grunting are noted. Cyanosis and dyspnea appear with little response to oxygen. Physical examination reveals poor air movement bilaterally. A chest x-ray reveals air bronchograms and a fine reticular granular pattern. Which of the following conditions should be suspected?
Small areas of atelectasis usually are asymptomatic. While larger areas may present with similar clinical findings, the chest x-ray findings are not consistent with atelectasis.
Diaphragmatic hernia
Chest x-ray in a patient with a diaphragmatic hernia would not show a fine reticular granular pattern.
Respiratory distress syndrome
Chest x-ray in a patient with a pneumothorax would not show a fine reticular granular pattern.
Question 1 Explanation: 
Clinical findings of increasing cyanosis unresponsive to oxygen therapy and the characteristic x-ray findings are most consistent with respiratory distress syndrome.
Question 2
A 36-year-old male who is hospitalized because of severe injuries from a motor vehicle accident develops rapid onset of profound dyspnea. Initial chest x-ray shows a normal heart size with diffuse bilateral infiltrates. Follow-up chest xray shows confluent bilateral infiltrates that spare the costophrenic angles. Which of the following is the best clinical intervention for this patient?
Tracheal intubation
Bilateral chest tube insertion
Chest tube insertion is not indicated in a patient with ARDS.
Type-specific packed cells
Fluids are the preferred treatment initially for hypovolemia. Type-specific packed cells are given when the patient's blood type is identified. Until then O negative packed cells are administered.
Colloid solutions
Use of crystalloid solutions are preferred to avoid pulmonary edema.
Provide supplemental oxygen
Marked hypoxemia is refractory to treatment with supplemental oxygen in ARDS.
Question 2 Explanation: 
Tracheal intubation with lowest level of PEEP is required to maintain the PaO2 above 60 mmHg or SaO2 above 90% in a patient with ARDS.
There are 2 questions to complete.
Shaded items are complete.

References: Merck Manual · UpToDate

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