Table 5.

Virtual reality breathing studies: virtual environments.

Study	Virtual environments
Abushakra et al [7], 2014	Tissue layers and cells are presented to the participant. Through different types of breathing, the participant diminishes the cancerous lung cells.
Betka et al [49], 2022	A room with a matched-gender virtual body lying on a couch. The virtual body is illuminated synchronously or asynchronously according to the patient’s chest movements.
Blum et al [25], 2019	The natural environment of a beach scenery at sunset with palms, rocks, several light sources, and a campfire.
Blum et al [10], 2020	Natural environment with a landscape having hills, flowers, parts of trees, and rocks that change their color according to breathing.
Brammer et al [41], 2021	The trainees must shoot hostile zombies while they leave the benign zombies unharmed.
Charoensook et al [31], 2019	There were 4 games: (1) Beat Saber, (2) Space Pirate Trainer, (3) Gorn, and (4) Final Approach.
van Delden et al [5], 2020	There were 3 games: (1) Popping balloons, (2) Car, and (3) Diving.
Feinberg et al [47], 2022	A dedicated space for meditation with peers and a virtual instructor with an hourglass to track time. There is a bonsai tree that grows to signify progress. The environment changes every few sessions, including weather (sunset or rainstorm).
Gummidela et al [45], 2022	A square arena in which a ball bounces with a randomly initialized direction and location.
Heng et al [43], 2020	There were 8 mini-games: (1) Bubble Gum, (2) Candle Blower, (3) Windmill, (4) Pest Control, (5) Wind Arrow, (6) Table Cleaner, (7) Winter Window, and (8) Steak Gourmet.
Hu et al [35], 2021	There were 2 games: (1) pond scene and (2) ocean scene.
Jung et al [27], 2020	Not reported
Kluge et al [36], 2021	There were 8 discrete modules: (1) emotions, thoughts, and actions; (2) controlled breathing; (3) progressive muscle relaxation; (4) grounding; (5) values and realities; (6) stress reappraisal; (7) managing thoughts/cognitive defusion; and (8) acceptance and avoidance.
Ladakis et al [37], 2021	Fantasy Forest Environment: the participant walks in nature and relaxation sceneries that facilitate recovery from job stress.
Mevlevioğlu et al [38], 2021	There were 2 scenes: (1) nature scene with trees, grass, and flowers moving based on the user’s breathing; and (2) elevator scene with a glass elevator outside of a large building in a city, with a height of 6 levels.
Michela et al [44], 2022	A parking garage with friendly and hostile human targets to shoot or not.
Patibanda et al [34], 2017	Life Tree: a tree starts growing through inhalation and exhalation.
Prpa et al [26], 2018	Pulse Breath Water: ocean waves that change their movement according to breathing pace.
Quintero et al [32], 2019	Calm Place: climate sequence that goes from dusk to noon with the appearance of a blue object in the middle of the virtual scene to guide the breathing exercise.
Rockstroh et al [39], 2021	Two types of virtual environments of nature, with elements such as trees, grass, flowers, and rocks.
Rodrigues et al [50], 2022	A relaxed environment.
van Rooij et al [40], 2016	An underwater world in which children can move around freely and explore at their leisure.
Rutkowski et al [42], 2021	Virtual therapeutic garden.
Shih et al [24], 2019	A sailing boat moving backward and forward with the participant’s breathing.
Soyka et al [28], 2016	A jellyfish moving up and down in an underwater environment.
Desnoyers-Stewart et al [33], 2019	An underwater world with 2 jellyfish and a growing glass sponge.
Tabor et al [8], 2020	There were 2 games: (1) Bubble Float and (2) Bubble Paint.
Tao et al [46], 2020	A music studio scene, where the participant was asked to practice a virtual reality harmonica instrument.
Tatzgern et al [48], 2022	There were 6 scenarios: (1) blowing all candles on a cake, (2) blowing projectiles through a blow tube, (3) shooting a toy gun, (4) blowing ships, (5) inflating balloons, and (6) playing the harmonica.
Tinga et al [29], 2018	A white cloud moving toward and away in the direction of the participant’s mouth.
Tu et al [6], 2020	There were 2 games: (1) Balloon, where the participant could control the movement of a balloon through respiration and (2) Pilot, where the participant’s breathing could control a flight’s course.
Zafar et al [30], 2018	There were 3 video games: (1) Chill Out, (2) Dodging Stress, and (3) Pacman Zen.