This paper documents the development of an oxygen (O2) tank carrier for adults dependent on medical oxygen, addressing the users need for comfort and safety while promoting active lifestyle choices. O2 Moba integrates two ergonomic functions: a comfortable backpack for a d-type cylinder and an adjustable rolling system ensuring improved mobility and product longevity. Usability trials were conducted with four participants; they were asked to perform in scenarios designed to simulate critical tasks. The scenarios included placing the oxygen tank into the main compartment, threading the nasal cannula, placing O2 Moba on as a backpack and adjusting for comfort, converting the backpack into the rolling system and pushing and pulling O2 Moba in a trial course. Three measures were taken: force exerted on shoulders and hips, a mixed questionnaire, and timed performance. The purpose of the study was to identify how effective O2 Moba was at meeting its design objectives and to recommend further improvements.


Statistics from the The Lung Association™ British Columbia report that chronic obstructive pulmonary disease (COPD) affects 4.8 % of women and 3.9% of men. Studies show that pulmonary rehabilitation in the form of exercise improves breathing muscle strength which is key to managing COPD symptoms. Active adults can participate in light to moderate cardiovascular exercise on a regular basis to strengthen pulmonary muscles despite their reliance on medical oxygen.

Market research shows that cylinder bags and carts available today are geared towards the elderly or for use in emergency health services. Mobile oxygen users seek comfortable product alternatives to shoulder carriers and oxygen carts. This user group includes active adults affected by respiratory disease within the age range of 30 to 70, and their mobility is paramount to their sense of independence and self-esteem.

O2 Moba (Fig. 2 and Fig. 3) is a system designed to promote active well being for users with this profile. O2 Moba integrates two ergonomic functions; a comfortable backpack for a d-type cylinder and a lightweight adjustable rolling system to address the user’s need for improved mobility and product longevity. Moreover, O2 Moba addressed the stigmas associated with respiratory disease and the burden of lugging around industrial medical equipment by incorporating an athletic aesthetic.

Figure 1. Working Prototype of O2 Moba
Figure 1. Working Prototype of O2 Moba

O2 Moba was designed by Diane Espiritu, as her final undergraduate project for the Industrial Design program at Emily Carr University of Art + Design (ECUAD). Along with Claire Kim (ECUAD) and Jason Leong (Simon Fraser University), the team of students conducted user trials to test the proposed objectives of the design under the supervision of their instructor Anne-Kristina Arnold in her three dimensional concentration: Human Fit course.

User Trial Objectives

The purpose of the study was to find out how effective O2 Moba was at meeting its design objectives, to identify areas of the design that need improvement, and to recommend further ergonomic design criteria.

The team wanted to investigate the following questions: does O2 Moba improve the users’ daily experience carrying an oxygen tank so the user can spend more time outdoors? Is it easy to use and easy to learn? Does it make daily activities more efficient and comfortable by reducing the time it takes to complete critical tasks such as loading the cylinder into the carrier? Does wearing O2 MOBA aid in reducing the strain and fatigue associated with carrying an oxygen tank by distributing the weight evenly onto the shoulders and hips? Are there any potential pinch points that have been created in the harness or any other potential injury risks?


Our ergonomic design approach included the following methods: an ethical review process, co-creation to gain insight into the concerns of the users, research and consultation with professionals in the field of respiratory health, soft product design prototyping, ergonomics, and user trials. Empathy exercises were conducted to understand the physical demands of the users carrying oxygen equipment. Market research established the percentage of the population to be accommodated and their corresponding critical dimensions to identify the needs and physical constraints of primary users. Identification and analysis of critical tasks performed by users informed both the design of the prototype and usability trial design. Vigorous prototyping occurred early in the design process to arrive at a functional prototype.

Product description

O2 Moba is categorized as a soft product, medical assistive device that functions as a backpack and a rolling push and pull carrier for a d-type oxygen cylinder. The backpack is constructed with water resistant nylon for its outer shell and lined with cork upholstery to provide lightweight insulation between the tank and the user’s body. The O2 cylinder fits into an aluminum chassis that is secured at the base of the backpack; this is also where the shock absorbent 80mm wheels, brakes and telescoping handle are secured. The harness consists of two shoulder straps connected by a sternum strap and a hip belt to aid in distributing the weight evenly over the shoulders and the hips. There are two small stash pockets accessible on the exterior of the bag. Two alternative openings allow for the nasal cannula to be threaded. The opening on the side panel is to be used when the bag is worn on the back allowing the user to thread the cannula over either shoulder; the opening on the front top center is used when O2 Moba is converted into the rolling system. Openings can be used interchangeably depending on the user’s preference. Releasing and pulling up the handle from the side of the backpack converts it into the rolling system.

Percentage of Population to be Accommodated

O2 Moba aims to accommodate 90% of the population of men and women from the 5th percentile woman to the 95th percentile woman in need of ergonomic oxygen mobility backpacks; this involved integrating a range adjustment for design features. These percentiles contained the smallest and largest critical dimensions of interest.


Four participants were recruited for the usability trials. Participants one and two were oxygen dependent females; participant one was within the age range of 50 to 59, participant two was in the age range of 60 to 69. Participants three and four are non-oxygen dependent males, participant three was within the age range of 20 to 29 and participant four was within the age range of 30 to 39. To test the range of body types that O2 Moba fit comfortably, the oxygen users in the study represented the “outliers” of our target group falling into the 5th and 95th percentiles of our normal population. Each of the two female subjects had maximum and minimum critical dimensions and strength limitations according to the average North American anthropometric tables.

Usability Trail Design

The following critical tasks were identified:

1.0 Placing a full O2 tank into the main compartment of O2 Moba

1.1 Threading the nasal cannula into a hole from the interior to the outside of the bag, through the loop on the shoulder strap and zipping the bag up (this is a personal safely issue)

1.2 Placing the bag on their back and adjusting the straps and hip belt to fit

2.0 Converting the bag into the rolling system (new task)

2.1.0 Pushing O2 Moba through the trial course simulating exterior obstacles (new task)

2.1.1 Pulling O2 Moba through the trial course simulating exterior obstacles

Before the initiation of the trial, evaluators determined how much pressure the subjects could withstand on their shoulders and hips. A live demonstration of the tasks was presented before the subjects were asked to perform them. Participants were asked to go through the tasks twice. The evaluators recorded the time of their first trial to completion as well as any misstep they may have encountered. The subjects were then asked to perform the task a second time and to “think aloud” to voice their thought processes, which were recorded by evaluators. The participants were also asked to fill out short questionnaires to obtain more specific information.


Objective Measure: Force on shoulders and hips

The team used an Almedic Aneroid Sphygmomanometer Blood Pressure Meter to measure the amount of pressure exerted onto the shoulders and hips of the participants. Evaluators placed pressure on the shoulders and then on the hips of each subject in increments of 10 mmHg while the subjects were continually asked if they would be able to withstand that amount of pressure for at least an hour. The final portion of the testing involved obtaining the actual value of pressure that O2 Moba created. This value was then compared to the subjective reports from participants.

Subjective measure: Questionnaire

People’s perceptions give a deeper understanding of design concerns. The questionnaire had a short introduction and asked relevant information about the tasks the subjects had performed, including Likert Scale ratings on their experience with the O2 Moba, forced questions pertaining to design features, and a rating of body part discomfort after the trial.

Performance measure: Timed Trials and Errors in Scenario

The trials were timed to completion and it was noted if the subject successfully completed the task, partially completed the task or failed to complete the task. Errors for tasks 1.0, 1.1, 1.2, 2.0 were recorded as either; fail (subject does not complete task), partial success (subject is able to complete task however they miss a step, must redo a step or completed the task in a different order). Errors for task 2.1.1 and 2.1.2

included pushing or pulling O2 Moba outside the delineated path. Talk-out-loud trials were not timed as the time to talk increased the length of the task. The video recording of all the trails were later observed and compared to the data recorded during real time. Recordings enabled the team to observe the subject’s posture and identify relevant information the users revealed about their experience.

figure 2. Uncomfortable shoulder carrier (left) vs Working prototype on user (right)



Recommended Improvements to the Design

Use of two zippers on the main compartment was recommended based on the participants’ difficulty zipping the O2 Moba up; participants often reached for a second zipper not included in the design. Shoulder straps needed to be shortened so that the adjustment was within reach; smaller subjects had difficulty adjusting shoulder straps to fit their body. Participant one suggested that the back panel cannula exit be located directly under the regulator to discourage kinks to the oxygen delivery line. Participants one and two noted that there could be a hook on the telescoping handle for the cannula when O2 Moba is being pushed or pulled. Side pocket zippers could be lengthened to accommodate larger hands. Boning should be moved from the zipper hood to the top panel where it attaches to the back panel to allow users better access to zipper while maintaining the shape of the bag. A colour code system with matching colour buckles could reduce confusion as to where they attach. Graphic instructions on the back panel could help users to see how to convert from backpack to roller. The padding should be designed in such a way as to communicate that there is only one correct way to connect it. The telescoping quick release mechanism should be reconsidered since users had some difficulty locking it.

The following are the team’s concluding remarks on the improvements that can be integrated into future usability trials. During the demonstration of the conversion of O2 Moba from the backpack to the roller, subjects should be shown how to adjust the handle so that it is high enough to reach the hand at a neutral position when the bag is tipped towards the user in the active position to push or pull. The simulated obstacle course tested the handling of O2 Moba in a supermarket environment and not the ability of the user to navigate the physical exterior environment; it would be beneficial to conduct a usability trial with a constructed exterior environment simulating a city block. Subjects stepped on the line of the obstacle course that was meant to represent a wall or physical object; the use of physical walls or boundaries would be beneficial. The team used an Almedic Aneroid Sphygmomanometer Blood Pressure Meter to measure pressure exerted onto the shoulders and hips; using actual force sensors would result in more accurate readings.

The designer should never lose sight of whom they are designing for. Usability trials allowed us to gather insight into a variety of critical elements, many of which were unanticipated and had not been accounted for in the design planning. O2 Moba was designed to be pushed, making it an ergonomic alternative to pulling a load. However, the team found that half of the subjects preferred pulling to pushing. The positive aspect of this contradiction is that O2 Moba can be pushed or pulled comfortably depending on the user’s preference.

CURRENT – An Interview with Diane Espiritu from The Design° on Vimeo.


  • 1) Haight, J.M., Hallbeck, M.S., & Jung, Myung-Chul. (2007). Biomechanical and Physiological Analyses of a Luggage-Pulling Task. Pennsylvania: Pennsylvania State University.
  • 2) Jan Dul, & Weerdmeester, Bernard. (2006). Ergonomics for Beginner: A Quick Reference Guide (3rd Edition). Boca Raton, FL: CRC Press
  • 3) Kroemer, Karl H.E. (2006). Extra-Ordinary Ergonomics: How to Accommodate Small and Big Persons, The Disabled and Elderly, Expectant Mothers, and Children. Boca Raton, FL: CRC Press
  • 4) Nemeth, Christopher P. (2004). Human Factors, Methods for Design: Making Systems Human-Centered. Boca Raton: CRC Press.
  • 5) Canadian Respiratory Health Professionals, Canadian Thoracic Society, & The Lung Association. (2006). Women and COPD: A National Report. British Columbia: The Lung Association.

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