CONTINUOUS POSITIVE AIRWAY PRESSURE

CPAP

Objectives

• Define CPAP• Understand pathophysiology• EMS applications• Protocol implementation

What is CPAP???• CPAP increases pressure in the lungs and holds

open collapsed alveoli, pushes more oxygen across the alveolar membrane, and forces interstitial fluid back into the pulmonary vasculature.

• This improves oxygenation, ventilation and ease of breathing.

• The increased intrathoracic pressure decreases venous return to the heart and reduces the overwhelming preload (pressure in the ventricles at the end of diastole).

• This lowers the pressure that the heart must pump against (afterload), both of which improve left ventricular function.

So why does oxygen pass into the blood?

Pressure GradientDeoxygenated blood has a lower partial pressure of oxygen than alveolar air so oxygen transfers from the air into the blood.

CPAP alters the pressure gradient!

7.5cm H20 CPAP

1cm H2O is equal to 0.735mm Hg.

7.5cm H2O CPAP increases the partial 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.

Perfusion

• Refers to the process of circulating blood through the pulmonary capillary bed

• In order for perfusion to occur, the following must be intact:– A properly functioning heart (pump) – Proper vascular “size”– Adequate blood volume / hemoglobin

The Requirements Of CPAP

The real requirement is for Continuous CONSTANT Positive Airway Pressure

A stable airway pressure as prescribed in order to reduce work of breathing (WOB)

CPAP is oxygen therapy in its most efficient form.

Simple Masks

Venturi Masks

Humidifiers

CPAP

Important Aim Of CPAP Is To Increase Functional Residual

Capacity (FRC)

Volume of gas remaining in lungs at end-expiration

CPAP distends alveoli preventing collapse on expiration

Greater surface area improves gas exchange

Physiological Effects Of CPAP

Increases PSO2

Increases FRC

Reduces work of breathing

Indications for Use

• Treatment of severe respiratory distress CHF/COPD/Asthma

• RR>25 bpm• Retractions, accessory

muscle use or fatigue• SAO2 < 94% at any time• Near drowning• Pt must be able to maintain

own airway and be able to follow commands.

Exclusion Criteria

• BP <90 mmHg• Unconscious• Inadequate

respiratory rate• Cardiac arrest

• Unable to obtain adequate seal

• Pnuemothorax• Active emesis

CPAP And Pulmonary Edema

Severe pulmonary edema is a frequent cause of respiratory failure

CPAP increases functional residual capacity CPAP increases transpulmonary pressure CPAP improves lung compliance CPAP improves arterial blood oxygenation CPAP redistributes extravascular lung water

(Rasanen 1985)

Redistribution Of Extravascular Lung Water

With CPAP

Benefits/Advantages of CPAP• CPAP reduces work of breathing by

keeping the “wet” alveoli open• If the alveoli are open at the end of

expiration, energy is not consumed on the next inhalation

• Work of breathing is reduced relieving respiratory muscle fatigue

Benefits/Advantages of CPAP• A higher alveoli pressure will result in

a stoppage of fluid movement into the alveoli

• Increase in airway pressure results in improved gas exchange

CPAP And Acute Respiratory Failure

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)

WHAT ABOUT THE EMPHYSEMA PATIENT?

Important Point

• Emphysema patients do not respond predictably to CPAP

As a general rule…• The larger the “barrel chest” and the

more pronounced the accessory muscles, the more caution we should use with CPAP

What is needed for CPAP application.

• Oxygen source capable of producing 50 psi.

• Flow regulator which delivers either a fixed oxygen concentration at 30% or an adjustable flow regulator.

– Venturi– Micro channels

• Tight fitting mask to which the oxygen/air mixture output of the generator is attached and applied to the patient.

• Positive End-Expiratory Pressure (PEEP) valve connected to the exhalation port which maintains a constant pressure in the circuit.

• What are some signs and symptoms of respiratory distress??

What is needed for CPAP application.

• Oxygen source capable of producing 50 psi.

• Flow regulator which delivers either a fixed oxygen concentration at 30% or an adjustable flow regulator.

– Venturi– Micro channels

• Tight fitting mask to which the oxygen/air mixture output of the generator is attached and applied to the patient.

• Positive End-Expiratory Pressure (PEEP) valve connected to the exhalation port which maintains a constant pressure in the circuit.

• What are some signs and symptoms of respiratory distress??

CPAP Contraindications

• CPAP may be contraindicated for patients with any of these conditions:– Unconscious– Apnea– Pneumothorax– Decreased cardiac output and gastric

distention– Severe facial injury– Hypotension secondary to hypovolemia– Uncontrolled vomiting

Explain the Procedure to your Patient

• Explain to your patient that in order to get the best possible results from a CPAP device. Ask them to inhale through the nose and exhale through the mouth against the pressure produced by the CPAP machine.

• If they do not know what to expect, it is similar to the air felt when sticking your head out of the car window when moving.

The Whisperflow• Here is a step by step review of the operation

of the Whisperflow CPAP device.      • Properly assess pt for baseline

Pulse Oximetry

   • Attach high pressure hose to portable tank

using short adapter hose. It may be best to load the patient first and start CPAP early in the transport: conserves portable tank for ER transfer.

  • Assemble mask and tubing, don't forget to

place thefilter on air intake of the CPAP device   

The Whisperflow

Prepare mask, strap rearrangement might be necessary

Explain the procedure to the patient. Turn the unit on (all the way) & turn the FLOW on (all the way)

Have the patient place the mask on his/her face tightly. Some

"coaching" will help the patient transition from holding the mask

near their face to creating a seal.  It's OK for the patient to hold the mask without using the straps if they're more comfortable that

way. When he is comfortable with the feeling of the mask

 you may secure it to his head tightly so that no leaks are

noticed.

Final Application StepsNext you'll need to fine-tune the unit by decreasing the FLOW until a slight outward flow is felt while the patient inhales.

After loading the patient to the unit  you'll need to transfer to the onboard oxygen.Do it quickly - turn on the main first!

You can easily add nebulized albuterol to the patient's treatment by cutting the tubing at a joint and inserting a 'T' and nebulizer with 6 liters oxygen attached.

By using the patient's pulse-ox level as a guide you may adjust the amount of oxygen up to achieve desired oxygen saturation, usually 90 -93%.

If the mask is not tolerated after coaching…

remove it!!!

A few things to remember...  

• When the flow valve is open all the way, with the oxygen valve closed,  you are giving the patient 28% oxygen and a portable tank will last quite some time!

• By increasing the oxygen flow, you'll use more liters per minute - as much as 140! Be careful, you'll run out!

• If you reach the point that air is blowing out of the air intake on the device your oxygen flow is too high.

• When swapping from portable to main oxygen tanks warn the patient that the flow will stop for a few seconds but they will still be able to breathe, then swap quickly!

Oxygen Tanks

At 28-30% FiO2 , a full tank should last approximately:

• D cylinder=28 minutes • E cylinder=40-50 minutes • M cylinder=about 4 hours

• FiO2 is fraction of inspired oxygen.

(at 100% FiO2 a D cylinder tank will last approximately 3-4 minutes. Use what you need, but be prepared with additional cylinders)

You are called to a 76-year old male who is complaining of dyspnea. Upon arrival, you find the patient sitting

on a chair leaning forward. He is diaphoretic, cyanotic and has a respiratory rate of 48. Upon auscultation

you hear fine crackles throughout both lung fields and he is hypertensive.

Case Study for CPAP

http://www.eresp.com/CPAPosSim.swf

Works Cited and Thank You

Thank you to EMS Personnel at Dallas Ambulance, ST Paul Fire, Salem Fire, Rural Metro, Washington Co EMS, MTCI, Albany Fire, Marion County, and

Mercy Flights for sharing information regarding CPAP. The following websites were also use as resources.

• http://www.dhfs.state.wi.us/ems/EMSsection/Protocols/CPAP/CPAP_Protocol.pdf

• http://www.ems1.com/columnists/dan-white/articles/390898-A-Look-at-CPAP-for-EMS

• http://caradyne.respironics.com/whisperflow.htm• http://phillydan.spaces.live.com/Blog/cns!B2AD15EED4F62B2B!236.entry• http://elearning.respironics.com/main_ProdTrainCourse_pr.asp• http://www.jcems.net/cgi-bin/news.cgi • http://www.eresp.com/CPAPosSim.swf• http://www.miamitwp.org/fireems/training/skill_sheet_ems.htm • http://www.emsresponder.com/features/article.jsp?

id=1738&siteSection=16• http://www.maconnc.org/ems/CPAP.html• http://www.merginet.com/index.cfm?pg=airway&fn=CPAPuser• http://emsstaff.buncombecounty.org/inhousetraining/cpap/

cpap_overview2.htm• http://www.doctorfowler.com/lecturepage.shtml

Questions and answers