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Need & Concept

Rationale & Need

The Indian subcontinent and parts of Southeast Asia are currently facing a devastating second wave of the COVID-19 pandemic. Oxygen shortage is currently an acute issue in many major cities and towns where infections have spiked. At the time of writing (May 17, 2021), estimates based on WHO data put the current oxygen demand in India at 15.8 million cubic meters or 2.2 million oxygen cylinders per day.1 These numbers, which are based on testing data, are also likely underestimated. Challenges in both production and supply chain management and distribution mean that India is struggling to distribute these life-saving supplies where they are needed the most.2 The problem is only more severe as the disease further spreads in the rural areas, which have two third of India's population but have less infrastructure and are associated with more transportation delays. Worryingly, other countries in the Indian subcontinent, such as Nepal, have also started facing acute oxygen shortages mirroring the situation in India.3

Among symptomatic COVID-19 patients, while most only develop mild (40%) and moderate (40%) disease, around 15% develop severe disease requiring oxygen support, whereas 5% have critical disease with complications requiring intensive care.4 For those patients who require supplemental oxygen, in the course of their clinical management, delivery of oxygen usually starts and stops with nasal cannula at flow rates less than 6 L/min. Oxygen delivered during patient exhalation is mostly vented to the air and wasted, providing an opportunity for oxygen conservation by shutting the flow when the patient is exhaling. Towards this, some completely passive solutions have been developed, such as the Oxymizer device.5,6 However, due to the limited reservoir size and fluid dynamic parameters which these devices are designed for, the effect of oxygen saving decreases significantly as the flow rate is increased (3:1 at 0.5 L/min, 1.7:1 at 2 L/min, 1.4:1 at 4 L/min and 1.3:1 at 5 L/min)11, making these devices useful only in oxygen therapy for COPD. Other more effective oxygen conservation devices have been developed in the 1990's and early 2000's but now have very limited or no availability.

A device which conserves oxygen for oxygen therapy in COVID-19 patients will extend the life of cylinders and will help in this climate of extreme shortages.


In oxygen therapy, when a patient exhales out, the oxygen still leaks away - thus wasting up to approximately 2/3 or more of oxygen in the tank as inhalation only amounts to approximately 1/3 of the respiration cycle. If a sensor can sense inhalation-exhalation cycles, and oxygen flow can be stopped or diverted to a buffer storage during exhalation, then we could save this oxygen and thus increase the life of an oxygen tank by almost three times (and hence tripling the supply).

Time plot of flow over exhalation, inhalation, and exhalation, with useful and wasted oxygen.

Fig. 1: Typical respiratory flow cycle for continuous-flow supplemental oxygen.8

Plot of relationship between supplemental oxygen flow rate and end-tidal oxygen fraction, for pulsed-flow delivery and continuous-flow delivery.

Fig. 2: Pulsed oxygen flow allows the use of a considerably smaller average supplemental nasal oxygen flow rate to achieve the same end-tidal oxygen concentration. E.g., in data from 30 volunteers, to achieve an end-tidal (exhaled) oxygen concentration of 44%, continuous flow (CFO) needed 6 L/min, while pulsed flow (PFO) only needed about 2 L/min. The oxygen savings are disproportionately larger as the oxygen needs increase.9

Oxygen conservation devices already exist and can allow significant savings of oxygen8,9,10 - but their cost is in the $200 range, and they are not widely available.

The goal of the proposed device is to implement a simple yet safe version of a pulse-dose system that can be rapidly manufactured and deployed in the context of the current situation in the Indian subcontinent and Southeast Asia. Our goal is to work with industrial partners to bring this device to the market with quality and scale. The device is envisioned to be used in settings where patients with mild conditions are being treated; it is not intended for severe COVID-19 patients.


The main requirements of the pulse-dose oxygen conservation device are as follows:

  • The device should deliver oxygen to the patient during the inspiratory phase while conserving oxygen during the expiratory phase.
  • The device should deliver oxygen during the first part of the inspiratory phase after commencement of inhalation, to ensure most of the oxygen delivered is "useful oxygen" that reaches the alveoli.
  • The device should robustly detect inhalation by setting a suitable pressure trigger point
  • The device should trigger robustly under different user conditions, including movement and sleep.
  • The pneumatic system should have a fail-open design which provides continuous oxygen flow to minimize the impact of any device failures on patient safety. In a fail-open state, the flow rate should be controlled at the flow regulator attached to the oxygen cylinder.

Additional requirements for usability are as follows:

  • Robustness:
    • The device should be water-resistant/splash-proof.
    • The device should remain functional after being dropped.
  • Versatility:
    • The device should be portable.
    • It should be possible to power the device from a variety of power sources.
  • The device should be tamper-proof.
  • Requirement for COVID-19 patients: the device should have an alarm for high respiratory rate, which indicates distress and the need for increased flow rate or further escalated care.

  1. Market Dynamics. COVID-19 Oxygen Needs Tracker. PATH, 17 May, 2021.
  2. D Ghoshal. Why India is facing an oxygen crisis as COVID cases mount. Reuters, 23 April, 2021.
  3. R Bhandari, H Ellis-Petersen. 'A hopeless situation': oxygen shortage fuels Nepal's Covid crisis. The Guardian, 10 May, 2021.
  4. World Health Organization. COVID-19 Clinical management: living guidance. WHO, 25 January, 2021.
  5. BL Tiep, RE Phillips, BA Otsap. Oxygen delivery apparatus. USPTO US4535767A, 1982.
  6. E Abel. Oxygen delivery and conserving device. USPTO US5280780A, 1992.
  7. R McCoy. Oxygen-conserving techniques and devices. Respiratory Care 45, no. 1 (2000): 95-103.
  8. KM Burk, K Kuck, JA Orr. Evaluation and application of a method for estimating nasal end-tidal O2 fraction while administering supplemental O2. Journal of Clinical Monitoring and Computing vol. 33 (2019): 1071–1080
  9. C Fuhrman, C Chouaid, R Herigault, B Housset, S Adnot. (2004). Comparison of four demand oxygen delivery systems at rest and during exercise for chronic obstructive pulmonary disease. Respiratory medicine, 98(10) (2004): 938-944.

Prakash Lab