This Pandemic has created positive outcomes. Leadership has been acquiesced by the unlikeliest of heroes. Heroism has bred collective altruism. Altruistic hearts have become dominant driving forces for critical minds. Critical minds of thought and question have led to innovation. Innovation through collaboration realises solutions.
All South Africans must be the Solution.
I was part of the problem. I advocated for more oxygen devices. I applied more oxygen devices. I used more oxygen. I wasted oxygen. My patients needed oxygen. I had no other choice.
I left you previously with what may influence choice. My influences were often effectiveness, limitation and emotion. No regard for cost or efficiency.
Emotion was a dominant factor during the early days. Save a life – regardless. Yet the disease process proved superior to my knowledge, skills, experience and resources. The loss of life surmounted. The loss of emotion surmounted. Emotionless I stood beside the deceased. But I am sure most of us felt like this, one way or another….
I felt limited as a professional. The environment was limited. Oxygen devices were limited. The fraction of inspired oxygen that could be offered was limited. The amount of therapeutic intervention was limited.
Could change be brought to these limitations?
Could a higher fraction of inspired oxygen be offered to the greatest number of people?
I felt ineffective as a professional. The environment was ineffective. Oxygen devices were ineffective. The amount of therapeutic intervention was ineffective.
Could change be brought to ineffectiveness?
Could oxygen devices with effective therapies be offered to the greatest number of people?
Could I change my profession? Could I change the environment?
This rumination clouded my emotionless being. But I am sure most of us felt like this, one way or another….
Change had to come in the form of myself, the environment and for the patients. But as an individual, I could not achieve this alone. It was a team who was effective, efficient and so surpassed the limits.
The limitation of oxygen devices lay in their offering of inspired oxygen percentage. Nasal prongs, face masks and those with reservoir bags have their known thresholds of oxygen percentage. The absence of an air-tight seal allows room air to be entrained if the patient’s inspiratory demands are not met. This is especially true if oxygen flow meters cannot deliver a flow higher than 15l/min. And also true if the device only operates below that flow rate. The end result is that the true fraction of inspired oxygen delivered to the patient is less than assumed . And so, the environment is limited by what the device can offer – in both oxygen percentage and therapy.
Is oxygen effective? For most disease processes, it corrects hypoxia. Yet it does not address the underlying cause of hypoxia. Thus, is it merely supportive? A well established and effective form of therapy is Positive End Expiratory Pressure (PEEP). PEEP is made available through the use of flow (High Flow Nasal Cannula (HFNC), CPAP devices, mechanical ventilators) or with valves (mechanical or virtual) [1, 2]. An important iteration – CPAP is one method to deliver PEEP. Through publication, H and L phenotypes were identified and which of those respond to PEEP [3, 4]. Yet the concept is binary. But the perspective is that patients often fall along a continuum. Could PEEP be made more available to patients and perhaps at an earlier stage? However, the oxygen devices that are cheap and readily available in large quantities (nasal prongs, face masks and those with reservoir bags) do not offer anything beyond oxygen. And so, the environment is as effective as the therapy which the device offers. But should effectiveness come at the cost of efficiency?
Open system devices (nasal prongs, face masks, partial/non-rebreather masks, HFNC and certain CPAP devices) allow oxygen to escape. And with high flow devices that are open systems, the intended therapy offered besides oxygen support is at the expense of increased oxygen use. The graphs I left with you previously highlight this well . The two encircled columns represent the extremes. A total patient flow rate of 15l/min requires the oxygen flow rate to be 14l/min to obtain inspired oxygen of 95% (Device B). In comparison, to achieve the same percentage, a total patient flow rate of 60l/min requires the oxygen flow rate to be 56l/min (Device A). Is the increase of oxygen flow by 42l/min justified to achieve the clinically significant therapy offered by CPAP and by the obtained level of PEEP? Remember, CPAP is one method to deliver PEEP. And one should ask if the oxygen flow needs to meet the entire inspiratory demand and how much oxygen is wasted when using the device . Closed system devices (certain CPAP devices, mechanical ventilators) need to meet that demand but are efficient in oxygen delivery and use for patients in respiratory failure .
I had no regard for efficiency or cost. I was wrong. Efficiency decreases cost. Decreased cost improves availability. Availability achieves Utilitarianism. Let me show you:
DIFFERENTIAL OXYGEN CONSUMPTION CALCULATION
Oxygen flow (Device A): 56l/min
Oxygen flow (Device B): 14l/min
Oxygen consumption difference: 42l/min
(Assumed to be at 298K and atmospheric pressure at patient)
Calculation Method (first principles)
Ideal Gas Law: 1 mole of gas occupies 22.414 litres at NTP (293K and 1atm)
1 mole of oxygen has a mass of 31.999 g per mole
Density of oxygen is 31.999/22.414 g/l = 1.428 g/l
Oxygen consumption difference
Oxygen costs to public hospitals is R12.85/kg (incl VAT) or R11.17 (excl VAT)
Oxygen consumption difference
86.40kg/day x R11.17
Thus a team took it upon themselves to conceive a solution which offered a higher fraction of inspired oxygen and therapy. Along with improved oxygen efficiency, cost and availability.
Can we change our profession?
We can change the way we think and how we practice oxygen use.
Can we change the environment?
We can make oxygen less limited, more effective, efficient and available to others.
Is this the dawn of an Oxygen Era?
These ruminations should cloud our being. But I am sure most of us feel like this, one way or another….
Until next time, remain safe.
- Wagstaff, A., Glover, C., & Soni, N. (2012). Continuous Positive Airway Pressure in Acute Respiratory Failure: The Importance of the Valve. Journal of the Intensive Care Society, 13(1), 17–24. https://doi.org/10.1177/175114371201300107
- Pinto, V. L., & Sharma, S. (2020). Continuous Positive Airway Pressure. In StatPearls. StatPearls Publishing.
- Gattinoni, L., Chiumello, D., Caironi, P., Busana, M., Romitti, F., Brazzi, L., & Camporota, L. (2020). COVID-19 pneumonia: different respiratory treatments for different phenotypes?. Intensive care medicine, 46(6), 1099–1102. https://doi.org/10.1007/s00134-020-06033-2
- Marini, J., & Gattinoni, L. (2020). Management of COVID-19 Respiratory Distress. JAMA, 323(22), 2329–2330. doi:10.1001/jama.2020.6825
- Toy, B. (2021, January 05). The Oxygen Problem. Retrieved January 11, 2021, from UMOYA | Innovation in the air: https://umoya.org.za/