The reason why CPAP should no longer be utilized is that, it aerosolizes the virus and places you at undue risk. Since CPAP is not a closed system it can aerosolize the virus. This puts not only yourself as the treating paramedics at increased risk, but other healthcare workers as well as patients in the ED when you come through with a patient on CPAP.
The evidence from China published in a preprinted release in the Medical Journal of Australia showed failure rates of non-invasive ventilation in Wuhan of up to 85% and recommends against all forms of non-invasive ventilation. During SARS, there were reports of significant transmission secondary to non-invasive ventilation.
The World Health Organization published their Clinical management of severe acute respiratory infection (SARI) when COVID-19 disease is suspected, interim guidance document on March 13 where it recommended caution with non-invasive ventilation and to be used only in tightly controlled settings, noting a high failure rate.
Although SWORBHP medical council believes that CPAP is a prehospital treatment that can improve morbidity and mortality, not all have the same interpretation of the literature. As such, CPAP is not a prehospital treatment that is used province-wide. Furthermore, the prehospital COVID-19 screening tool is not a perfect tool and as such, those with asymptomatic COVID-19 or an atypical presentation may pass the COVID-19 screen. Given the potential risk of COVID-19 aerosolization and the impact this may have on you as a treating paramedic, on other healthcare workers and the public, it was decided that the benefit did not outweigh the unintended risks and harms. Given this, the provincial MAC decided to restrict the use of CPAP in all patients in respiratory distress patients.
The expectation is that you provide other potential treatments based on the cause for the respiratory distress: Oxygen, nitro in CHF, MDI salbutamol if there is bronchoconstriction and rapid transport to the ED.
Here are two websites where you can find an extensive collection of research around COVID-19. Keep in mind the majority of this research is observational studies.