CPAP for NYS EMTs is coming

                                                                  CPAP FOR EMS

Continuous Positive Airway Pressure (CPAP) devices will be coming to NYS EMT's shortly.  Here is a short guide to CPAP.  Since we do not know yet how the NYS BLS Protocols will permit EMTs to use CPAP we will keep it very general for now. It will obviously be used in Acute Pulmonary Edema, but it is unclear if it will be allowed in other emergency situation.

Before we start just remember that CPAP cannot be used in any patient with any of the following conditions EVEN if they are in respiratory distress:

1. Decreased Mental Status / Inability to sit up / Altered Mental Status
2. Respiratory arrest / Apnea /  Respiratory failure / poor inspiratory effort
3. Pneumothorax / Trauma to the thorax / Subcutaneous Emphysema
4. Any form of Shock / Hypotension
5. Nausea / Vomiting / any risk of aspiration
6. Facial Trauma / Abnormalities

How CPAP Works:

Continuous Positive Airway Pressure, (CPAP), is the maintenance of positive pressure throughout the complete respiratory cycle, (inspiration and expiration), when breathing spontaneously. CPAP is not the same as Positive End Expiratory Pressure or PEEP. PEEP only provides pressure on the expiratory side by offering resistance to exhalation using a spring-loaded valve or air flow.

 

1. During the inspiratory phase, patients in distress will have to create a higher flow rate of air to meet their needs, this will present as an increase in work-of-breathing (WOB). Patients in respiratory distress may need to achieve inspiratory flow rates greater than 65 liters per min (LPM). With the inspiratory support of CPAP, the patient does not have to work as hard to inhale and overcoming the auto PEEP in the lung. Auto-PEEP represents the abnormal, and usually undetected, residual pressure above atmospheric remaining in the alveoli at end-exhalation due to air trapping.  The auto PEEP has to be overcome each time a person inhales, for a healthy person the work is minimal and goes unnoticed. However, those patients with stiff lungs, (CHF and Pulmonary Fibrosis), have to work extremely hard to overcome the increased auto PEEP on every breath.

 

2. The increased inspiratory pressure also increases the size, therefore the surface area of the

alveoli, providing a greater opportunity for gas exchange or respiration. The process increases the

Functional Residual Capacity (FRC) of the lung. The FRC is the area where gas exchange takes place.

 

3. Since a greater oxygen percentage is able to reach the alveoli during CPAP, the partial pressure

of the oxygen molecule will be greater. The higher partial pressure will allow more oxygen to

diffuse into the blood stream improving oxygenation.

 

4. Fluid in the alveolar space cannot only make the lung stiff, (increasing inspiratory

work-of-breathing), it also creates a barrier that can reduce gas exchange. The pressure from CPAP

can reduce the fluid by forcing fluid out of the alveolar space back into the interstitium.

 

5. During the expiratory phase, the patient will breathe against a threshold of resistance that

works as a pneumatic splint to hold the airways open. Patients with chronic lung disease have

weakened airways that have a tendency to collapse on expiration, causing air trapping. Having the

airways stinted open during exhalation will make inspiration on the next breath less difficult.

 

6. The resistance during exhalation can open non-ventilated areas of the lung recruiting alveoli

that have collapsed due to atelectasis, (a collapse of lung tissue affecting part, or all, of one

lung effecting gas exchange).

 7. CPAP decreases pre-load and after-load on the heart reducing the heart’s workload. However, a reduction in pre-load and after-load will have an effect on the patient’s blood pressure. Patients

should have a systolic blood pressure of at least 100 mmHg before starting CPAP.

 

What Types of Patients Are NOT Candidates for CPAP?

Being able to assess and determine who is, and who is not, a candidate for CPAP has a great impact on whether CPAP will be effective or not. CPAP can be a very effective treatment for patients in respiratory distress but is not indicated for patients in respiratory failure. Respiratory distress patients are still compensating even though they may be working hard. It is not uncommon for respiratory distress patients to have oxygen saturations (SpO2 ) and carbon dioxide, (CO2), levels within normal range. Key determinants include; is the patient alert, (even though they are working hard), and can they follow directions. Patients that have gone into respiratory failure may exhibit a decrease in work-of-breathing, CO2 levels climbing, oxygen saturations falling, and their level of consciousness declining, (most likely from CO2 narcosis). CPAP is not indicated for respiratory failure patients.

 

CPAP and Congestive Heart Failure (CHF):

The treatment of Congestive Heart Failure, (CHF), by EMS has changed significantly in the last couple of years. The mainstays of CHF treatment (ALS) in the pre-hospital setting are CPAP and nitroglycerin. The efficacy of Lasix and Morphine is under scrutiny and has been removed from many EMS ALS protocols. Many systems that adopt CPAP start with CHF. The effects of CPAP are well suited for the physiologic issues associated with this disease. Pulmonary edema, associated with CHF, makes the lungs stiff and it is difficult for the patient to inhale; and can be observed as difficulty breathing during the inspiratory phase of ventilation or inspiratory shortness-of-breath. Since CHF is primarily a heart problem, CPAP addresses the side effects of a failing heart and its impact on the lungs.  CHF is a process that will continue to spiral down the cardiogenic shock pathway until the cycle is broken. As the patient’s heart fails, more fluid ends up in the lungs. With more fluid in the lungs, less oxygen makes it to the heart muscle, so the heart fails even more. The first step in stopping the cycle is the early use of CPAP. If the patient does not have lung disease then the airways should function normally and not collapse on exhalation. In this case, the inspiratory pressure will force the fluid out of the lungs, expand the alveoli which, in turn, will increase gas exchange (respirations) improving oxygenation.In addition, with the airways being held open by the expiratory resistance, the patient does not have to overcome

the auto PEEP at the beginning of each breath. With the improvement of gas exchange and reduced impact of auto PEEP, the patient’s work-of-breathing will be reduced. With the reduced work, there will be less stress on the heart. A key factor in the initiation of CPAP is the patient’s blood pressure. It is recommended that the systolic blood pressure be at least 100 mmHg before starting CPAP due to the reduction in pre-load and after-load.

 

More to come after the protocols are released.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Recent question from an EMT student

Mottled arm

Mottled newborn

Hypoperfusion Question and Answer

Question: Good morning, just want to make sure I got it right, most emergencies have Hypoperfusion involve? (at least potentially) in other words, a dead person is in shock, so every life threatening situation is a shock situation, so all emergencies need to be treated for shock? (CHF, MI, CVA and even appendicitis can lead to shock) so, shock treatment is only needed if signs and symptoms of shock are present?

Answer: Not exactly.  Not every emergency results in hypoperfusion.  As an example. A person having an asthma attack is only having a respiratory emergency unless the hypoxia gets so severe it interferes with the ability of the heart to beat.   

A quick review of shock:

Hypovolemia is one for the four categories of shock.  This type of shock is caused by low volume of either blood (Hemorrhagic shock) or other fluid (Metabolic Shock).  Metabolic shock is caused by a loss of intracellular (inside the cells) or extracellular (outside the cells but not in the blood vessels) fluid.  Metabolic shock is usually caused by excessive vomiting, diarrhea, urination in Diabetic Ketoacidosis (DKA) and renal failure. It can rarely be caused by excessive sweating. Some books list plasma lost from burns as hemorrhagic shock and other list is as metabolic.  Usually it is considered metabolic shock.  Treatment of hemorrhagic shock involves the controlling of external bleeding, leg elevation, O2, and temperature control (keeping the patient warm).  Transport should be immediate and to a trauma center. Treatment of metabolic shock involves leg elevation, O2, and temperature control (keeping the patient warm).  Transport can be to any hospital, but if involves a pediatric patient it should be to a pediatric capable hospital. Hypovolemic shocks are the only shock that result on fluid being lost from the body. 

Cardiogenic shock is caused by one of four issues.  1.  Severe damage to the ventricles.  This can be caused by an AMI (heart attack), infection in the myocardium (heart muscle), or rarely trauma to the myocardium.  2.  Heart valves not working correctly and allowing blood flow to go backwards. 3.  A heat rate that is to slow (bradycardia) or a heart rate that is to fast (tachycardia).  When the heat rate is to slow the Cardiac Output (heat rate x stroke volume) drops because the number of time the ventricles are pumping is to slow.  In a tachycardia the problem is that the time between contractions (diastole) is so short the ventricles do not fill completely so stroke volume drops.  This is called decreased ventricular filling time.   EMT treatment involves O2 (sometimes the patient’s mental status will be so decreased that you can use the BVM), warmth, and rapid transport.

Distributive shock involves the smaller more peripheral blood vessels in the body.  The cause of hypoperfusion is the sudden vasodilation (widening) of these blood vessels. There is no blood loss; the blood is re-distributed from the vital organs to the skin and other non-vital area.  The result is that there is less blood going to vital organs.  Distributive shock is considered the most difficult shock to determine.  The reason why is as follows.  In all other shocks the skin is usually cool, pale, and diaphoretic.  Peripheral pulses are usually weak.  In distributive shock, the warm core blood is sent to the extremities and surface blood vessels.  Initially, the skin will be warm, pink (in light skinned patients), and dry.  The peripheral pulse will be strong. This will change if the shock is not treated. There are four types of distributive shock:

1.       Anaphylactic shock.  Caused by the body’s immune system overreacting to some foreign substance.  (Bee venom, peanuts, milk, medications etc.) Substances are released by the immune system that causes vasodilation and bronchoconstriction.  The is also an increase in the ability for plasma to leak out of the capillaries (increased capillary permeability) which results in hives (urticaria) on the skin and possible narrowing of the airways.  Treatment involves the use of the EPI-Pen, O2, and transport.

2.       Septic shock is caused by vasodilation which is caused by a severe body wide infection. Usually in the blood stream and major organs. There can also be an increase in capillary permeability like in anaphylaxis.  Treatment involves warmth, O2, leg elevation and transport.

3.       Neurogenic shock is the rarest form of shock.  It is also called spinal shock.  The usual cause is damage to the spinal cord.  This results in interruption of the sympathetic nervous system (Fight or flight). The sympathetic nervous system usually results in vasoconstriction and tachycardia.  If it is interrupted the parasympathetic nervous system will dominate causing vasodilation and bradycardia.  Neurogenic shock is the most difficult of all of the Distributives shocks to diagnosis.  This is because in addition to the other tricky presentations (warm, flushed skin and strong radial pulses) there is also a slow to normal pulse rate.  In the other shocks we expect there to be a tachycardia to compensate for the low perfusion. .  Treatment involves warmth, O2, Leg elevation and transport.  Since there may be paralysis of the muscles of the airway and breathings from the spinal cord injury you may need to maintain the airway (airway adjuncts) and ventilate the patient.

 4.       Psychogenic shock (simple fainting, syncope) results from the vagus nerve being stimulated.  The vagus (10th cranial nerve) is the messenger nerve of the parasympathetic nervous system. When activated it causes a slowing of the pulse and vasodilation resulting in a drop in blood pressure.  This results in less blood to the brain which causes syncope (fainting); the patient becomes unconscious and usually falls supine or prone.  It is now easier for blood to reach the brain then when the patient was standing.  The patient gradually wakes up as the heart rate increases back to normal and the blood vessels go back to normal diameter.  This usually causes the cerebral (brain) hypoperfusion to end. The patient usually has no long-term issues, unless they hurt themselves when they fainted.  EMS can cause Psychogenic Shock to happen by suctioning and /or inserted an OPA too roughly and by pressing to hard when checking a carotid pulse.  Patients can cause this to happen by straining when they go to the bathroom.  Sometimes this happens as a result of stress, bad news, and even the sight of blood. Treatment involves checking the patient for injury, leg elevation, O2, and warmth.  They should be brought to hospital to determine the cause of their syncope.

Obstructive shock is cause by a blockage (obstruction) in a large blood vessel.  Again, there is no loss of blood but rather blood flow through the circulatory system is slowed and may even be stopped.  Common causes include Tension Pneumothorax, Pulmonary Embolism, 3rd trimester pregnant females lying supine, and Cardiac Tamponade.

1.   In a tension pneumothorax pressure builds up in the thoracic cavity outside of the lungs and decreases blood flow through the inferior and superior venae cava. This results in less blood getting back to the heart, which results in less cardiac output.   Usual causes are a puncture or hole to the lung.  This can be caused by penetrating trauma from a bullet, knife or even a broken rib.  Rarely a patient’s lung can burst without trauma; this is called a spontaneous pneumothorax. Signs and symptoms include diminished or absent lung sounds over the injured lung, tracheal deviation away from the injured lung (also called a mediastinal shift, this is usually an x-ray finding), difficulty breathing, tachycardia, and in severe cases hypoperfusion.  In there are any holes between the patient’s shoulders and umbilicus (belly button) they should be sealed with an occlusive (airtight) dressing on 3 sides.  This stops air from being inhaled though the hole on patient’s chest into their thoracic cavity when the patient inhales but allows pressure to vent from the thoracic cavity when the patient exhales. O2 should be administered and the patient should be brought to a trauma center.

2.   Pulmonary Embolisms result in a blockage somewhere in the pulmonary arterial circulation.  This results in lees deoxygenated blood in reaching the lungs.  Patients complain of a sharp pain to their chest and difficulty in breathing. There is no blockage in the airway.  The sensation of shortness of breath (SOB) comes from the restriction of blood flow to the lungs.  Common causes are recent fractures, being bed ridden (confined to a bed), deep vein thrombus (DVT) of the legs.  There is an increased risk in women who smoke and take birth control pills (oral contraceptives).  It could also happen in scuba divers from breathing compressed air while underwater and then coming to the surface too quickly. Management on a BLS level is limited to O2 and rapid transport.

3.   Supine Hypotensive Syndrome. In a third trimester pregnant women who lies supine the weight of the baby may compress the inferior vena cava causing less blood to get back to the heart.  This is usually not an emergency.  EMS can cause this to happen by placing the patient supine as in spinal immobilization.  Treatment is as simple as moving the patient onto their left side or tipping the long board on the left side slightly.

4.   Cardiac Tamponade is when the sac (pericardial sac) surrounding the heart has a buildup of fluid in it.  This fluid can be either blood from trauma or other fluids that build up from infection. It can rarely be caused by a rupture (burst) coronary artery. (This usually fatal) This fluid buildup does not allow the ventricle to fully expand and fill with blood.  This results in decreased cardiac output.  Signs and symptoms may include: In trauma – puncture wounds to chest, jugular vein distention (JVD), diminished or muffled heart sounds (JVD).  Depending on the amount of fluid in the pericardial sac there may be signs and symptoms of shock.  In an infectious (pericarditis) form of Cardiac Tamponade the patient will usually appear ill from an infection.  They will be complaining of pain on their chest, SOB.  There sign may be warm if they have fever or cold if they are in shock.  In severe medical forms of Cardiac Tamponade there can be muffled heart sounds and JVD. In trauma; treatment incudes sealing any holes on the chest (in case there is also a tension pneumothorax), 02, and rapid transport to a trauma center.  In medical; treatment includes O2 and transport.

Ok.  I guess it was not a quick review.

Thanks,

Frank