Confirmation
CPAP Refresher
September 20, 2019
Hosts:
Gord Minaker, Primary Care Paramedic and Medical Student with the UBC Medical Program
Kaela Richardson, Respiratory Therapist and Medical Student with the UBC Medical Program
Episode Description:
What IS CPAP? Gord Minaker hosts fellow medical student and current respiratory therapist Kaela Richardson for a brief episode on CPAP in the prehospital setting. Together they review the physiological mechanisms of CPAP and how this applies to certain patient populations and their associated pathologies. Other topics include nebulizer use, indications, contraindications and settings for CPAP, as well as a brief discussion on BiPAP.
What is CPAP?
- Positive pressure delivered non-invasively via a face mask
- Used to improve oxygenation and support a patient's breathing
Equipment Needed
- Mask
- CPAP device
- Oxygen tubing
- Oxygen tank
Physiology of CPAP
Positive pressure within the airways and alveoli improves respiratory function:
- Minimizes alveolar collapse
- Increases lung compliance
- Decreases work of breathing
- Reduces ventilation-perfusion mismatch
What is Ventilation-Perfusion Mismatching?
Ventilation-perfusion mismatching, aka V/Q mismatching, refers to an abnormal ratio of ventilation to perfusion in the lung. It can be caused by a number of different pathologies, depending on which aspect is reduced. In this episode we mention shunting, which refers to a V/Q mismatch involving adequate perfusion but poor ventilation. This occurs when air is not reaching the alveoli, and blood flowing by these areas are not participating in gas exchange. Without gas exchange, the blood remains deoxygenated and hypercarbic, which can be observed as a low SpO2 and/or a high respiratory rate in a clinical presentation.
Classic Patient Populations
- Congestive heart failure
- Chronic obstructive pulmonary disease
Indications for CPAP include patients in respiratory distress
- Nasal flaring
- SpO2 < 94%
- High respiratory rate (RR>24)
- Accessory muscle use
- Shoulders heaving
- Head bobbing (seen more in children)
- Indrawing at collarbones or bottom of neck
Contraindications
- Decreased LOC
- Hypoventilation or Respiratory arrest
- Vomiting
- Unable to fit mask
- Traumatic cause of shortness of breath
- Pneumothorax
- Systolic BP < 90 mmHg
- Tracheostomy tube with inflated cuff
Setup of CPAP with Nebulizer
Points to Remember:
- CPAP delivers a constant positive pressure throughout inspiration and expiration
- Apply to spontaneously breathing patients that are able to protect their airway
- Indications include RR > 24 breaths/minute, SpO2 < 94% and accessory muscle use
- CPAP functions to reduce work of breathing and improve oxygenation
- Classic patient populations include COPD and CHF patients
References:
BCEHS Handbook: Treatment Guidelines for CPAP - PCP
NCBI - Continuous Positive Airway Pressure
https://www.ncbi.nlm.nih.gov/books/NBK482178/
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Email: podcast@bcehs.ca