Pearls for Non-Invasive Positive Pressure Ventilation
1. CPAP and BiPAP are useful tools for treating COVID19.
2. Oxygenating the patient is the end goal.
3. Ensure a viral filter is attached to the exhaust line of CPAP/BiPAP device.
Non-invasive Positive Pressure Ventilation (NIPPV)
Non-invasive ventilation is a category of treatments used to help restore a patient’s balance of oxygen supply and demand without the use of intubation. These treatments work to increase the positive pressure of ventilation and help the patient to return to a homeostatic level. Two important concepts for review:
FiO2
Fraction of inspired oxygen – The percentage of oxygen the patient is receiving. Typically, patients breathing room air are exposed to approximately 21% FiO2. If a patient has a problem with insufficient oxygenation, too little oxygen available/delivered to their cells, one way to fix this is to increase the Fi02 in order to meet their oxygen demands. The below chart lays out the often cited FiO2 levels from common oxygen delivery devices.
| Device | Fi02 Amount 2 |
| Room air | 21% |
| Nasal Cannula | 22-30% |
| Non-rebreather | 75-90% |
| High Flow Nasal Cannula | 40-50% |
| CPAP | up to 100% |
| BiPAP | up to 100% |
PEEP
Positive end expiratory pressure – The amount of pressure in the bronchi at the end of an expiration, typically measured in cmH20 1. Several tools used to aid patients with oxygenation problems increase PEEP in an effort to increase oxygenation. As PEEP is increased, the volume of surface area available for oxygenation increases so more oxygen can diffuse across the alveolar membrane.
PEEP in Action
NIPPV Tools of the Trade
HFNC – High flow nasal cannula
Main effect – Increase Fi02
Specially designed nasal cannulas used to increase the amount of FiO2 for a patient. The delivered oxygen is typically warmed and humidified and delivered via specialized nasal prongs that form a seal on the nostrils.
Benefits
- Often is tolerated better than CPAP or BiPAP by patients
Drawbacks
- Can’t provide as much ventilation support to the patient as CPAP/BiPAP
CPAP – Continuous positive airway pressure
Main effect – Increase Fi02 and PEEP
This tool delivers 1 level of pressure during both inspiration and expiration. The goal is to increase oxygenation for the patient. The intention is when the patient exhales against a pressure, the patient’s alveolar surface area increases and more area for diffusion is the result.
Benefits
- Increases alveolar recruitment to help combat atelectasis and hypoxia
Drawbacks
- Patient’s can feel anxious due to device mask, pressures on respiratory cycle, and other.
BiPAP – Bilevel positive pressure airway pressure
Main effect – Increase Fi02 and PEEP even further
This tool delivers 2 levels (biphasic) levels of pressure during the respiratory cycle. The inspiratory pressure is higher than the expiratory pressure with the intention of improved oxygenation3. The goal, just like CPAP, is to increase the surface area on expiration but also increased pressure on inspiration to support the volume of inspired air.
Two terms specific to BiPAP to understand:
IPAP (Inspiratory positive airway pressure) The amount of pressure on inspiration.
EPAP (Expiratory positive airway pressure) – Essentially the same thing as PEEP. The amount of pressure on expiration.
Benefits
- Increases alveolar recruitment to help combat atelectasis and hypoxia
- 2 level of pressures on inspiration and expiration further increase oxygenation
Drawbacks
- Patient’s can feel anxious due to device mask, pressures on respiratory cycle, and other.
Safe Set up of CPAP/BiPAP
Common Nursing Problems
Agitation
Possible solutions – Collaborating in care, educating the patient on the device, talking them through the equipment, and at times anxiolytic medications 4.
Aspiration
Potential solutions – Anti-emetic medications, education for the patient to remove the mask if they feel they might vomit, or not putting the patient on CPAP/BiPAP if the risk is too high 4.
Air leaks
Potential solutions – Adjust head straps, change to a different mask size, or make sure patient is not adjusting the mask themselves. This can be a hazard as shedding virus can be expelled 4.
References
1.Australian and New Zealand Intensive Care Society (ANZICS). “COVID19 Guidelines” Open Access. Version 1. 16 Mar. 2020. https://www.anzics.com.au/wp-content/uploads/2020/03/ANZICS-COVID-19-Guidelines-Version-1.pdf
2.Hardavella, Georgia et al. “Oxygen devices and delivery systems.” Breathe (Sheffield, England) vol. 15,3 (2019): e108-e116. doi:10.1183/20734735.0204-2019
3.Rose, Louise. “Management of critically ill patients receiving noninvasive and invasive mechanical ventilation in the emergency department.” Open access emergency medicine : OAEM vol. 4 5-15. 21 Mar. 2012, doi:10.2147/OAEM.S25048
4. Gavaghan, Susan, Jeffries, Marian. Your patient’s receiving noninvasive positive-pressure ventilation, Nursing2006: May 2006 – Volume 36 – Issue 5 – p 46-47 doi: 10.1097/01.NURSE.0000393383.70540.53