Definition Pressurized method of noninvasive ventilation with or without mechanical assistance.
Goals Reduce pre-hospital intubations Increase functional residual capacity (FRC) Provide a stable airway pressure Decrease work of breathing (WOB)
Lung and Aveoli
Functional Residual Capacity (FRC) Definition: Volume of gas remaining in lungs after expiration CPAP prevents alveolar collapse on expiration Greater surface area improves gas exchange
Partial Pressure The pressure of a gas mixture is equal to the sum of the partial pressures of its constituents. This allows oxygen into the blood during inspiration and CO2 out during expiration. Example : Air at sea level has a pressure of 1000cm H 2 0. Air is 21% oxygen and 79% nitrogen and other gasses. partial pressure of oxygen is 1000 X 21% = 210cm H 2 0
So why does oxygen pass into the blood? Pressure Gradient Deoxygenated blood has a lower partial pressure of oxygen than alveolar air so oxygen transfers from the air into the blood.
CPAP and Patient Airway Pressure The application of positive airway pressure throughout the whole respiratory cycle to spontaneously breathing patients.
7.5cm H 2 0 CPAP Atmospheric pressure can be expressed as 1000cm H 2 O 7.5cm H 2 O CPAP increases the pressure of the alveolar air by approximately 1%. This increase in partial pressure forces more oxygen into the blood. Even this comparatively small change is enough to make a clinical difference as CPAP alters the pressure gradient
ARDS CPAP overcomes inspiratory work imposed by auto-peep CPAP prevents airway collapse during exhalation CPAP improves arterial blood gas values CPAP may avoid intubation and mechanical ventilation (Miro 1993)
X-ray ARDS 13
Reducing fluid in the lungs CPAP decreases intra-alveolar fluid volume Facilitates movement of water Move from less to more compliant Improves oxygenation, compliance
Redistribution of extravascular pulmonary fluid
Congestive Heart Failure (CHF) Definition: Interstitial fluid interferes with gas exchange = pulmonary edema Increased myocardial workload Higher O2 demands Over age of /1000 patient Average length of stay (LOS) = 6.7 days Those intubated extend LOS Intubated pts have 4x mortality
COPD and Asthma Both with increased WOB Hypercapnia Higher mortality with intubation Difficulity to wean once intubated
Acute Respiratory Distress Syndrome (ARDS) Characteristics Hypoxemia Reduced compliance Large intrapulmonary shunt CPAP in early stages may Correct hypoxemia Improve compliance Reduce intrapulmonary shunt (Schmidt 1975)
Essential Components Of A CPAP System 1. Flow generator 2. CPAP valve
Whisperflow Flow Generators
Caradyne Isobaric CPAP Valve
Patient Connections - Face Mask
The High Flow System In Operation Air Supply In Total Flow 60 L/min
Application of CPAP
Clinical Applications of CPAP ConditionArea for Treatment ARDSEmergency CHF/Pulmonary edemaEmergency Acute Respiratory FailureEmergency COPD/AsthmaEmergency AnesthesiaPre Operative AtelectasisICU/General Ward Alternative to Mechanical VentilationICU/General Ward Weaning from Mechanical VentilationICU/General Ward Sleep ApneaHome
Contraindications Relative Claustrophobia Nasal Congestion Mouth breathing Absolute Cardiac/resp arrest Hypotension Need for emergent airway Pneumothorax Facial or neurological injuries, deformities Upper airway obstruction High risk of aspiration Unconscious
Common Complications With CPAP Irritation to skin and eyes Nasal congestion Dry nose, epistaxis Sore throat Barotrauma Gastric distention Reduced cardiac output Hypoventilation
CPAP Training Flow Sheet 2 or more of the following Respiratory Distress Inclusion Criteria -Retractions of accessory muscles -Brochospasm or Rales on Exam -Respiratory Rate > 25/min. -O2 Sat. < 92% on high flow O2 Administer CPAP using Max FIO2 -Continue CPAP -Continue COPD/Asthma/Pulmonary Edema Protocol -Contact Medical Control with a Report -Contact Medical Control with report -Discontinue CPAP unless advised by Medical Control -Continue Asthma/COPD/Pulmonary Edema Protocols Stable or Improving Reassess Patient Deteriorating No Exclusion Criteria Present -Respiratory/Cardiac Arrest -Pt.unable to follow commands -Unable tp maintain patent airway independently -Major Trauma -Suspicion of a Pneumothorax -Vomiting or Active GI Bleed -Obvious signs/Symptoms of Pulmonary infection,
Supporting Literature JAMA December 28, 2005 Noninvasive Ventilation in Acute Cardiogenic Edema, Massip et. al. Meta-analysis with good to excellent data 45% reduction in mortality 60% reduction in need to intubate Kosowsky JM, et al. EMS transports for difficulty breathing: is there potential role for CPAP in prehospital setting?. Acad Emerg Med Oct; 7(10) Strict criteria but demonstrated small number of pts benefit
Contd Literature Reviews in Cardiovascular Medicine, vol. 3 supl , Role of Noninvasive Ventilation in the Management of Acutely Decompensated Heart Failure Though BLPAP has theoretical advantages over CPAP, there are questions regarding its safety in a setting of CHF. The Key to success in using NIV to treat severe CHF is proper patient selection, close patient monitoring, proper application of the technology, and objective therapeutic goals. When used appropriately, NIV can be a useful adjunct in the treatment of a subset of patients with acute CHF at risk for endotracheal intubation.