Stages of Acute Respiratory Distress Syndrome (ARDS)

Nurse with patient going over ARDS stages with an elder senior woman patient in bed

Jump to Stages


  1. Early Stage
  2. Late Stage
  3. Third Stage
  4. Fourth Stage

Acute respiratory distress syndrome (ARDS) is a severe lung condition that can occur as a result of various underlying medical conditions or injuries. ARDS is a progressive condition that can have several stages.

It’s important to note that not all patients with ARDS will progress through all stages, and the severity of the condition can vary widely between individuals. Treatment of ARDS typically involves supportive measures such as oxygen therapy, mechanical ventilation, and treatment of any underlying conditions that may be contributing to the condition.

ARDS Stages

Nurses need to be familiar with the stages of ARDS so they can monitor patients for signs of worsening respiratory function, adjust treatments, and provide supportive care as needed. This can include oxygen therapy, mechanical ventilation, and monitoring for complications such as sepsis or organ failure. 

By understanding the progression of ARDS, you can help ensure that patients receive timely and appropriate interventions to improve their outcomes.

1. The Early Stage

In the early stages of acute respiratory distress syndrome, fluid accumulates interstitially within the pulmonary spaces. What does this mean? Interstitially means that the fluid, blood, pus, and white blood cells are not yet inside the lungs but are surrounding the lungs. This is termed as fluid in interstitial spaces.

            Fluid in interstitial spaces = fluid outside and around the lungs

2. The Late Stage

The second through the fourth phase of acute respiratory distress syndrome is called the late stage.

In this stage, interstitial fluid shifts into the alveoli. This means that the alveoli are now wet, and crackles are apparent. Crackles in the lungs are one of the primary manifestations of late-stage ARDS.

            Late stage = crackles of the lungs

patients who suffer from ARDS will not manifest crackles during the early stages but instead have clear lungs with just decreased breath sounds. The crackles become prominent two days later as the alveoli become wet and damaged.

3. The Third Stage – (Next Ten Days)

Within this time, fluid has already occupied the lungs, and pulmonary fibrosis occurs.

Pulmonary fibrosis is just a fancy term for burned lungs. Unfortunately, when something gets burned, it’s impossible to get it unburned. Therefore, patients progressing to the third and fourth stages of ARDS will continuously and chronically have burned lungs that could lead to systemic inflammatory response syndrome (SIRS).

Acute respiratory distress syndrome is technically just alveoli inflammation; however, if untreated and progressed, it can lead to systemic inflammatory response syndrome. SIRS is the inflammation of the entire respiratory tract that causes shifting of the fluid into the lungs, creating a breakdown.

Aside from total respiratory tract inflammation, this could also lead to multiple organ dysfunction syndrome (MODS).

            Ten Days = pulmonary fibrosis = progression can cause SIRS and MODS

4. The Fourth Stage

Oxygen is compromised at this stage. The patient is hypoxic (PaO2 is less than 60) and is acidic (less than 7.30 pH level). PaO2’s normal level is around 18 to 20.

How does a patient become acidic?

When oxygen has been distributed to the various parts of the body, carbon dioxide (CO2) waste is transported back to the lungs to be breathed out. However, since they have impaired, charred lungs, CO2 cannot be adequately exhaled, resulting in increased CO2 or carbon di-acid in your body, especially the lungs. 

Carbon dioxide will most likely be greater than 50, and the pH is also expected to go high. Both lead to an impaired exchange of oxygen.

            Fourth stage = hypoxic and acidic = no production line of exchanging oxygen

Patient Care

A mechanical ventilator is used for patients with severe ARDS. Your patients are expected to be hooked to a vent for the rest of their lives so they can breathe minimally. What is the importance of catching pulmonary fibrosis before it progresses?

  • Reverse side effects
  • Give treatment to decrease alveoli inflammation within the respiratory tract

Read more about nursing interventions for acute respiratory distress syndrome here.

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