Stage "A" of the M.A.R.C.H. algorithm addresses patient airway support. The goal of this stage is to ensure optimal respiratory function and access to an adequate level of oxygen for the body. At this stage, it is crucial to quickly and effectively respond to any threat of contamination or obstruction of the patient's airway.

Medical personnel assess the airways and ensure their patency. They may employ methods of artificial ventilation, such as using a mask with a reservoir for oxygen delivery or employing a mechanical ventilator (ventilator). In some cases, intubation may be necessary, involving the insertion of a special tube into the patient's airway to deliver oxygen directly to the lungs.

Airway support is critically important in the "A" stage, as sufficient access to oxygen and proper ventilation are crucial for the functioning of the organs and systems of the body. This stage requires prompt response, skills, and close observation by medical personnel to ensure optimal respiratory function for the patient and prevent potential complications.