A 76 year old man is brought to the surgical floor after surgery on his hip. He had been doing well until about 30 minutes ago when he suddenly became hypoxic as per the nurse. She increased the FIO2 to 35% but did not achieve good oxygenation. At that point she called the surgical Intern who in turn called you - the medical resident on call.

The patient has a heart rate of 132 and a respiratory rate of 34. You call the anesthesia resident to intubate the patient. He gets intubated by the anesthesia resident who had to struggle with a stiff neck and an inflamed larynx in order to get him intubated. During intubation, he also noticed a lot of fluid in the throat and the patient was difficult to awaken.

Once intubated, you re-assess the patient about half an hour later.

Which of the following parameters goes against the diagnosis of ARDS:

Hypoxia
Increased plateau pressure
Need for higher FiO2
Need for PEEP
None of the above

Answer is 5. All the above support a diagnosis of ARDS.

ARDS (Adult respiratory distress syndrome) is a condition where one faces heavy, leaky lungs.

The lung gets full of exudates and is difficult to ventilate. In order to get oxygen across the now thickened layers of the lung, extra pressure in the form of PEEP is to be used.

Criteria to diagnose it are 

Hypoxia
increased plateau pressure
Need for higher FiO2
Need for PEEP
Increased A-a gradient

CO2 may not be a problem as it diffuses easily and tachypnea is present - which is the earliest sign - even before dyspnea.

There are many causes for ARDS: Typically occurs due to severe systemic stress/infection. Other important causes are pancreatitis, aspiration, heroin and DIC.