cpap basics


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CPAP BASICS. GRANT COUNTY APRIL 2014. OBJECTIVES. Establish a protocol for Continuous Positive Airway Pressure usage for pre-hospital respiratory distress Discuss the basic principles of Continuous Positive Airway Pressure and its application Review the physiological effects of CPAP - PowerPoint PPT Presentation



GRANT COUNTYAPRIL 2014CPAP BASICSEstablish a protocol for Continuous Positive Airway Pressure usage for pre-hospital respiratory distressDiscuss the basic principles of Continuous Positive Airway Pressure and its applicationReview the physiological effects of CPAPDiscuss the indications and contraindications of CPAP usageOBJECTIVESLearn the LingoNIPPV: Non-Invasive Positive Airway PressureIncludes BiPAP, CPAP, Bag valve maskContinuous Positive Airway Pressure (CPAP)What we will be usingBi-Level Positive Airway Pressure (Bi-PAP)Often used in the hospital once the patient arrivesPEEP: Positive End Expiratory PressureA value we can measure on ventilated patients (ie, closed circuit)Both BiPAP and CPAP provide a small amount of PEEP

DefinitionsBiPAPContinuous PressurePressures are different between inhalation and exhalation (ie, 12/8 cm/H20)Not commonly used in the field or at home due to the complexity of delivery/devicesNeeds monitoring of delivered pressuresExpensive

CPAPContinuous PressureSame pressure during exhalation and inhalationUsed in the field and at homeLess complicated devices for deliveryNeeds little monitoringSet it and its goodCheaperBIPAP vs CPAPContinuous positive pressure delivery systemProvides more airway pressure than a non-rebreather mask but less than BVMSimilar to sticking your head out of a window while traveling at highway speeds CPAPNon-invasiveEasily AppliedEasily RemovedUseful for many types of respiratory distressCHF, COPD, Asthma, Pneumonia, Near drowningsAble to give nebs and other medications in-line or while it is appliedCan serve as a bridge to give patients extra respiratory support as the other medications and treatments have time to take effect (ie. Nitro/lasix, duonebs, steroids, etc)Can help avoid intubations for patients that are likely to rapidly improve with adjunct treatmentsCPAP Usage AdvantagesAlternative to ETT IntubationSome patients are not great candidates for intubations or are frail and likely to have a difficult extubationProspective randomized trials have shown 50-70% of patients with a severe COPD exacerbation who receive non-invasive ventilation can avoid intubationPrehospital use of CPAP for moderate-severe respiratory failure has been proven effectiveReduction in intubation rate of 30%Absolute Reduction in mortality of 21% In appropriately selected patients who received CPAP instead of usual care (intubation)COPD patients who are intubated typically are ventilator dependent for longer periods (difficult to extubate), causes increased morbidity with pneumonia risk and risk for spontaneous pneumothoraxCPAP AdvantagesPositive Pressure!Redistributes lung fields (inflates)Reduces work of breathingCounteracts intrinsic PEEPPursed lip breathingImproves Lung ComplianceReverses AtelectasisCollapsed alveoliDecreases Preload/AfterloadBeneficial esp for CHF patientsDecreased V/Q mismatch (ventilation/perfusion)Improves Gas ExchangeWhy cpap?Ventilation and perfusion mismatchCauses:Pulmonary EdemaPneumoniaIncreased dead space (collapsed or atelectatic lung)Pulmonary embolismShuntV/Q MismatchUpper LungsV>PMid LungsV=PLower LungsVPHigh v/q RatioEnough Perfusion, not enough ventilationAtelectasisIncreased secretionsMucus pluggingBronchial intubationshuntLow V/Q ratioHypothetical pressure of a gas in the atmosphere were it to occupy the same volume of space as the mixture it is inAir at sea level has a pressure of 1 atmosphere, or 760 mmHgAir is 21% oxygen at sea levelThe partial pressure of room air 02 is 760 x 0.21 = 159 mmHgPartial Pressure of gasThe difference in pressure between a higher concentration of gas and a lower concentration of gas is called a pressure gradientGas has a tendency to move from a higher partial pressure to a lower partial pressure until equilibrium is establishedThis pressure gradient is what causes oxygen to enter the blood and CO2 to leave the blood (gas exchange)Happens at the alveolar levelExpired air has oxygen content of about 16%, so the parital pressure is 760 mmHg x 0.16 = 121 mmHgThe pressure gradient of oxygen between room air (159mmHg) and blood oxygen (121mmHg) creates a gradient to allow oxygen exchangePressure GradientsCPAP changes the pressure gradientCPAP is measured by cmH2O1 cm H2O = 0.725 mmHgTypically CPAP is applied at either 5 or 10 cmH2OThis increases the partial pressure by 2.25%Increased partial pressure of oxygen delivered results in greater differential and improved oxygen exchangeThe clinical effects can be impressive with even this small changeCPAP and Pressure GradientsIncreased airway pressure with CPAPStent open airways that are at risk of collapse due to excess fluid or edemaInflates alveoli and prevents collapse during expirationCreates greater surface area= better exchange of gasesDecreases the work of breathing by preventing continual collapse of the airwaysPatient senses easier breathing, less work esp on inspirationMaintains gas exchange over a longer period of timeMechanical effectsIncreased oxygen levelsReduced work of breathingReduced V/Q mismatchPhysiological effects of cpapIndications: moderate to severe respiratory distress from the following:Pulmonary edema/CHF (including from near drownings)Acute Asthma exacerbation not responding quickly to usual treatmentsCOPD exacerbation failing conventional treatmentsPneumoniaGrant county protocolDO NOT USE CPAP IF:The patient is unconscious or alteredGCS