Our Goal in the Field using CPAP The Physiological Effects Delivery Systems Indications/Contraindications
“Learn the Lingo” – NIPPV – Non-Invasive Positive Pressure Ventilation Includes CPAP, BiPAP and BVM – CPAP – Continuous Positive Airway Pressure What we are going to be using – PEEP – Positive End Expiratory Pressure Used on Ventilators with Intubated PT’s – BiPAP – Bi-Level Positive Airway Pressure
CPAP Continuous Pressure Same pressure during exhalation and inhalation Used in field Uses simple device or complicated Needs little monitoring – Set it and forget it Cheaper than BiPAP BiPAP Continuous pressure Pressures are different between inhalation and exhalation – 5cmH20 Exhal; 15cmH20 Inhal Not commonly used in field No simple devices Needs monitoring of delivered pressures Expensive
Pressurized air that is continuously delivered throughout the entire respiratory cycle – Both inhalation and exhalation – Similar when you stick your head out of a moving car window at constant Speed
Non-Invasive Easily Applied Easily Discontinued Used on CHF, COPD, Asthma, Near Drownings, and Pneumonia Still able to use with other medications Is a bridge to keep patient going until medications begin having effect
“Alternative” to ETT Intubation – “Prospective randomized trials demonstrated 50%- 70% of patients with severe exacerbation of COPD and who receive non-invasive ventilation can avoid being intubated” 1 – “Paramedics can be trained to use CPAP for patients in severe respiratory failure. There was an absolute reduction in tracheal intubation rate of 30% and an absolute reduction in mortality of 21% in appropriately selected out-of-hospital patients who received CPAP instead of usual care.” 2 – COPD patients who do get intubated often are ventilator dependent for long periods 1 Consensus Conference. Noninvasive positive pressure ventilation. Respiratory Care 1997; 42:364- 369 2 Out-of-hospital continuous positive airway pressure ventilation versus usual care in acute respiratory failure: a randomized controlled trial. Thompson J, Petrie DA, Ackroyd-Stolarz S, Bardua DJ. Ann Emerg Med. 2008 Sep;52(3):232-41, 241.e1. doi: 0.1016/j.annemergmed.2008.01.006. Epub 2008 Apr 3.
Redistributes lung fluids Reduces work of breathing Counteracts intrinsic PEEP – (Pursed lip breathing) Improved lung compliance Reverses areas of Atelecatsis – Collapsed aveoli Decreases Preload/Afterload – Good for CHF Patients Decreased V/Q Mismatch Improves Gas exchange
When ventilation and perfusion do not match Causes: – Pulmonary Edema – Pulmonary Embolism – Pneumonia – Dead space increase
Caused by enough ventilation, but not enough perfusion – Pulmonary Embolism – Cardiac Arrest – Hypovolemia Normal in dead space – Ventilation, but no capillaries
Caused by enough perfusion, but not enough ventilation – Atelectasis – Increased secretions – Mucus plugging – Bronchial intubation Also called shunt perfusion
Hypothetical pressure of a gas were it to occupy the same volume of space as the mixture it is in. – Air at sea level has a pressure of 1 atmosphere, or 760mmHg. – Air is 21% O2 – The partial pressure of room air O2 is 760 x 0.21 = 159mmHg
The differences in pressure between a higher concentration of gas and a lower concentration of gas is called a pressure gradient – Gasses of a higher partial pressure have a tendency to move towards areas of lower pressure, until equilibrium is reached. – This pressure gradient is what causes O2 to enter the blood, and CO2 to leave it.
Since expired air is 16% O2, expired air O2 has a partial pressure of 760mmHg x 0.16 = 121mmHg – (Room air was 139mmHg) This difference between the partial pressure of expired air and inspired air causes O2 from room air to enter the blood where the partial pressure is lower, moving towards equilibrium.
So, how does this apply to CPAP? – CPAP changes the pressure gradient! – We measure CPAP pressures with cmH20 – 1 cmH20 = 0.735mmHg – On a typical patient, a CPAP of 10cmH20 will increase the partial pressure of O2 by ~2.25% – This increase in pressure “forces” more oxygen into the blood! – Even though it might seem small, the clinical significance can be all that is needed
Increased Pressure in Airways – Stenting open of airways that are at risk of collapsing due to excess fluid – Extends aveoli to prevent collapse during expiration Causes greater surface area = more exchange – Easier for the patient to breathe air in – Maintains gas exchange
Increased oxygen Levels Reduced work of breathing Reduced V/Q mismatch
Indications – Severe respiratory distress from the following: – Pulmonary Edema (including from near drownings) – Asthma exacerbations not responding to normal treatments – COPD failing conventional treatments – Pneumonia
Don’t use CPAP when patient is – Unconscious – Unable to cooperate or maintain their own airway – Hypotensive (<90mmHG) – Vomiting – Suspected Pneumothorax – Trauma – Facial abnormalities – Unable to maintain mask seal – Extreme caution in pulmonary fibrosis
Every CPAP system will be different 1.Overall goal is to increase airway pressure and gas exchange 2.Verbally coach patient, explain the procedure 3.Apply waveform capnography (ETCO2) 4.Apply CPAP with pressure of 5-10 cmH20 5.Coach and reassure the patient Watch for resistance and apprehension Check for leaks around mask/face seal 6.Reassess lung sounds and vitals q 5 mins. at least
7.In line nebulizers can be administered at same time as CPAP 8.Nitroglycerin may be administered by momentarily lifting facemask 9.If patient continues to worsen consider advanced airway measures
CPAP may cause a drop in blood pressure due to increased intrathoracic pressure Watch for GI distention, which may lead to vomiting Patient may become claustrophobic or unwilling to tolerate mask – Can be overcome with coaching
Proceed to advanced airway for patients with worsening respiratory distress or decreasing level of consciousness. Not for use in children <12 Y/O Advise receiving hospital of CPAP so they can prepare
Pulmonary Edema patients will improve within minutes of administration – “CPAP to Pulmonary Edema is like D50 to Hypoglycemia” Visual inspection of chest wall movement should demonstrate improved respiratory excursion – Bilateral chest wall movement, retractions, etc. – The look and feel of “Look, listen, and feel”
When to do what: Respiratory Distress – increased effort and frequency of breathing in maintaining normal O2 and CO2 in blood Respiratory Failure – inability to maintain normal amounts of O2 and CO2 in blood
Signs of Respiratory Distress: – Tachypnea – Tachycardia – Accessory Muscle Use – Decreased Tidal Volume – Paradoxical Abdominal Motion CPAP can generally be used on these patients
Declining tidal volume Irregular/Gasping Breaths Decline in LOC CO2 levels will climb, reducing LOC High CO2 lowers pH, causing acidosis
CPAP can provide a patient adjunct to allow medications to take effect – B2 agonists, Steroids, etc. CPAP Reverses CHF induced pulmonary edema Is less invasive than ET Intubation Helps COPD patients avoid ventilator dependency Fixes V/Q mismatch, opens airways, increases O2 pressure gradient, etc.