In “Black Flies” the full-frontal reality of two nighttime paramedics grabs you at the throat and doesn’t let go. The new Jean-Stéphane Sauvaire film is an infernal ride of double-shifts and bullying and death into the belly of the beast, the film pops, hits hard, the image is jumpy, the screams are loud, it’s a pressure-cooker, I came out of there traumatized and a little shaken. This is not the New York City I know. Had an inkling.

Jean-Stéphane Sauvaire is a French-Belgian filmmaker who’s lived in New York City for decades. He presented “Johnny Mad Dog” in 2008 in Cannes but the film that put Sauvaire on the map, however, was 2017’s “A prayer before dawn,” in which a young British boxer and heroin addict ends up in Thailand’s prisons where he has to fend for himself. The violence is sensual, it’s deconstructed, “Prayer” was a descent into hell that caused your blood pressure to rise. Sauvaire could be accused of sensationalism with his whizzbang editing, there’s a lot of bells and whistles here, the shaky image, the light flickering, it’s not a movie it’s an escape game! Sauvaire’s cinema is immersive and it leaves you with a strong impression.

In 2008 Shannon Burke, an author, published the book that this film is based on. A paramedic, Burke wrote about his on-the-job experiences during the crack epidemic, going from disaster to mayhem during his night shift, saving lives and trying to keep the mental intact. Sauvaire adapted the book to the screen, with Shannon contributing writing duties on the film’s screenplay.

The basic plot of the film: two paramedics on an ambulance ride around Brooklyn, responding to calls. They stop and get Chinese. They visit an ex-wife. Rutkovsky (Sean Penn) is the old dog he has a daughter, he doesn’t let the job get to him and the two eyes buried in his craggy face say melancolia as much as amusement. The rookie is Ollie Cross, played by Tye Sheridan (“Ready, Player, One”), he’s studying for the MCAT and hangs on with dear life as the ambulance takes them on a merry-go-round of human horror. He’s the archetypal beginner, an innocent look on his face, ready to save lives, and follow procedure which isn’t always to Rutkovsky’s taste. Off-the-job Cross wears a jacket with wings on the back of it, being a paramedic is like being an angel. At first this detail is tacky, but now I can’t imagine the character without this jacket. It just works.

Rut and Ollie sit in their ambulance eating or talking, a new call comes in. They go barreling down the streets of Brooklyn sirens blazing, the victims’ descriptions lighting up their screen monitor. A Russian woman badly beaten by her husband, a victim of a gang shootout, a slaughterhouse asthmatic, a young boy about to go into a seizure while the father, unfazed, sitting next to him, tells Ollie and Rut, “god will take care of him,” but one incident in particular is central to the storytelling, it was a badly-executed rescue of a newborn and it will result in both men being taken off duty.

Besides being fascinating to watch, one of the takeaways from “Black flies” is, and in case you didn’t know it already, paramedics have a difficult job, they’re cronfronted with the worst that humanity has on offer, misery, addiction, violence and resentment. In one scene from the film, one paramedic consoles Tye Sheridan’s character, “we’re surrounded by the darkness, but don’t let the darkness inside you.” Something to ponder for the rest of us, for paramedics it’s part of the daily grind and respecting this good precept, not letting in to impulse and anger, must take its toll. Which encourages us non-paramedics to commit our utmost respect to them, even more.

This film is competing for the Palme D’Or