The Role of CPAP in Covid 19

In order to promote the opening of the upper airways, Continuous Positive Pressure Ventilation (CPAP) has often been related to its role as an air splint in obstructive sleep apnea (OSA). This phenomenon helps minimize breathing disturbances related to sleep which in turn, provides better sleep and increases the Apnea Hypopnea Index. Therefore, this is quite good at sleep apnea treatment.

Extraordinary times require exceptional steps

But we are in an exceptional situation today, where the number of patients requiring intensive care admission clearly outnumbers the type of ICU beds usually required by any country. Around 5% of COVID-19 infected patients will require ICU admission, as several studies indicate, which is overwhelming given the large number of cases that build up in a short period of time, due to the high rate of nCOV infection. It is just not feasible to ventilate such a large number of patients with our current number of mechanical ventilators. Added to this the worldwide industrial supply chain has been broken, leading to more suffering.

To the occasion, regulatory bodies rise

Published information suggests that 5% of COVID-19 patients need ventilation, with numbers increasing to 89% for those in the intensive care unit (ICU). Of China's clinical studies also noted that 47.2% received invasive ventilation and 41.7% received non-invasive ventilation (NIV).

The U.S. National Academy of Medicine suggested on 5 March 2020 that the use of non-invasive ventilation therapy, such as Continuous Positive Airway Pressure (CPAP) or Bilevel Positive Airway Pressure (Bi-level), may be a means of avoiding the need for intubation and minimizing ventilator days.

In ventilators, the FDA has continued to provide emergency clearance for the use of sleep apnea devices to treat patients with respiratory failure, provided that sufficient design mitigation is in place to mitigate aerosolization. MHRA UK, in a similar vein, acknowledged the role that CPAP plays in the initial treatment of patients needing respiratory support, and NHS England continued to integrate CPAP into the COVID-19 escalation protocol as a modality of respiratory support.

CPAP Use Advice

NHS England (National Health Services) explains CPAP ventilation escalation when the patient has a respiratory rate (RR)>20/min with SpO2<94 on FiO2>40%. Trial recommendation CPAP requires a well-fitted full face mask with an initial pressure setting of FiO2 0.6 at about 10cmH2O.

CPAP with 60-100 percent oxygen may be raised to 12-15 cm H2O as per patient response. However during the CPAP trial, it is also mandatory to monitor the patient thoroughly, as most CPAP devices will lack sufficient alarms, which is a characteristic of intrusive mechanical ventilators.

In the use of CPAP, the mask and circuit also play a significant role. As recommended by the British Thoracic Society (BTS), a well-fitted non-vented full face mask with an anti-viral/bacterial filter between the mask and the exhalation port is required for CPAP/NIV use to prevent any contamination of droplets. Every 24 hours, the anti-viral/bacterial filter has to be modified.

COVID-19 Phenotype - CPAP

Two distinct phenotypes of COVID-19 patients have emerged, notably the L and H forms, as defined in Dr Gattioni's break review paper. Type L, characterized by high elastance, high right-to-left shunt, high lung weight and high recruitability, has been defined as low elastance (i.e. high compliance), low ventilation to perfusion ratio, low lung weight and low recruitability, and type H. Type-L and type-H are in fact two ends of the same continuum of illnesses.

Latest understanding indicates that noninvasive solutions such as continuous positive airway pressure or noninvasive ventilation with the lowest possible PEEP should be considered in Type L patients with dyspnea.

CPAP and Aerosolization

Recent data indicates that instead of aerosols, NIV/CPAP produces large droplets (>10μm) and this is largely limited to 1 metre spread. This phenomenon suggests that due to a respiratory disease, the risk of droplet distribution is equivalent to someone coughing. If the patient has a well-fitted, non-vented full face mask or helmet with an anti-viral/bacterial filter in a single limb circuit between the mask and the exhalation outlet, this problem can be minimized further.

So as we scramble against time, we may need to use all the ammunition available in our inventory to launch an effective reaction against COVID-19. Currently, CPAP is one such alternative and it is very optimistic that more scientific evidence and guidelines will soon improve our deterrence against COVID-19.

For sleep apnea treatment CPAP is more than only effective. For any related queries, visit us in OKC.

**Disclaimer: The information on this page is not intended to be a doctor's advice, nor does it create any form of patient-doctor relationship.