Considerations for Clinical Implementation
This page presents a number of the requirements and considerations regarding the implementation of the iSAVE. It is not comprehensive and is subject to revision. Clinicians should use this with their best judgement and under scenarios where standard of care is not feasible given emergency pandemic situations. It is important to recognize that the iSAVE has only been tested in pigs and is currently not approved for human use. The iSave team is currently engaging with third parties in order to proceed to apply for Emergency Use Authorization from the United States FDA in order for iSave to be used in healthcare settings to support patients during the COVID 19 pandemic.
Patient Matching Criteria
The iSAVE can handle differences in patient ventilatory needs. That said, some ventilatory parameters (RR, FiO2, I:E, PEEP) will remain shared amongst patients. Thus, patients should be matched as closely as possible in terms of degree of illness and ventilatory needs to optimize functioning as per the following criteria, where possible:
FiO2: Patients requiring FiO2 > 60% should be grouped separately from patients requiring FiO2 < 60% given common FiO2 settings and a desired threshold to lower FiO2 < 60% to avoid potential O2 toxicity.
Compliance: Patients with a C < 30 cmH20 should be grouped separately from patients with C > 30cc/cmH2O.
PEEP: should be within the range of 5-18 cmH20 and the difference between patients should be minimized to less than 5 cmH20.
Driving pressure (Plateau pressure - PEEP): should be within the range of 5-15 cmH20 and the difference between patients should be minimized to less than 6 cmH20.
Difference in height: should be minimized to 3-6 inches to ensure relatively similar tidal volume needs.
Comorbidities: Patients presenting with obstructive comorbid diseases (e.g., asthma, emphysema/COPD, bronchiectasis) vs. restrictive physiology (e.g., pulmonary fibrosis) should be grouped similarly to make circuit dynamics more uniform. Comorbidities that affect the individual patient I:E ratio (time constant) should be grouped together as ventilatory rate and I:E will be the same across patients with this technique.
Other considerations include hemodynamic stability, anticipated invasive ventilation time, co-infection and the logistics of space allocation for patients.
Components and system set up are described in the implementation tab.
Both patients should be deeply sedated and or have neuromuscular blockade to prevent independent ventilation. This will mitigate patient-triggering of the ventilator and reduce actions such as breathing, hiccup, or cough from interfering with system dynamics.
The ventilator should be set to minimize triggering by patient breathing efforts.
Limitations and Ethical Considerations
Our aim is to ensure that the iSAVE can be reliably implemented and utilized across intensive care clinical settings in cases of ventilator shortages. To this end, further steps must be taken to address current limitations:
- Due to differences in performance characteristics (mechanism of pressure/flow monitoring) of ICU ventilators, this approach must be tested across a range of ventilators in both volume and pressure control modes.
- The iSAVE must be evaluated in conditions reflecting the real-life variability of intensive care practice.
- The procurement and the sterilization process for non-standard components must be addressed.
- First-in-human trials must be performed to replicate the results from benchtop and animal investigations.
While this system mitigates several challenges associated with splitting ventilation, it has several drawbacks, unknown limitations and should be deployed with careful consideration. In a setting of severe life-threatening shortage of ventilators, ventilating two patients with the potential to save two lives may mitigate the need to triage which patients receive ventilatory support and which do not. If done safely, this may present greater overall societal value. Further ethical and policy-based discussions are necessary prior to and throughout implementation.