Dr. Biplob Borthakur explains with the help of a patient case as to why severe ARDS presents with short apnoea time before desaturation, the protective pedulluft, and why and how to prevent desaturation/cardiac arrest at intubation.

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Clinical situation

A young female, 35 years, presented, symptomatic for SARS-COV2 and severely dyspnoeic, with respiratory rate 38/min, not able to talk properly, on high flow oxygen and maintaining oxygen saturation (SpO2) 80%, heart rate 138/min and sinus rhythm, and blood pressure 140/100 mm Hg. Her chest X-ray showed diffuse bilateral opacities in all zones. Decision was taken for tracheal intubation and mechanical ventilation. After standard induction of anaesthesia and successful tracheal intubation with 30-second apnoea time from laryngoscopy to restarting ventilation, oxygen saturation dropped to 50% which improved to 80% gradually, the PEEP requirement went up, and the patient become hypotensive.

This is a common situation in the emergency department and in the ICU. Why do patients with severe ARDS have such short apnoea time before desaturating? Why do they have hypotension? Why does the oxygen saturation not improve much after intubation? Why is a higher PEEP required to ventilate after intubation? What can be done to avoid/mitigate this situation?