Airway Management Mask Ventilation of the Breathing Patient

Home , Hyperpnea, Hyperventilation, Hypopnea, Shallow breathing

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

Airway Management Mask Ventilation of the Breathing Patient Riverside EMS Agency Daved van Stralen, MD, FAAP Shanna Kissel, MSN, RN References John West, MD, PhD Videos http://meded.ucsd.edu/ifp/jwest/resp_phys/ http://meded.ucsd.edu/ifp/jwest/pulm_path/index.html Books Respiratory Physiology: The Essentials, Ninth Edition Pulmonary Pathophysiology: The Essentials, Eighth Edition

Respiratory terms and definitions Assisted ventilation terms CPAP and PEEP- Continuous Positive Airway Pressure for continuous flow systems, Positive End- Expiratory Pressure for positive pressure ventilation (hand ventilation or mechanical ventilation). This back pressure can be good when it recruits alveoli that were collapsed or keeps them open when they take too long (long time constant). It is bad when it causes the lung to stay open and not ventilate or is a measure of trapped air that can lead to lung damage or pneumothorax and death.

Bagging the patient We don’t “bag” patients, we hand ventilate. “Bag” and “bagging” are slang terms.

Breathing terms

Minute ventilation (volume per minute to remove CO2 - Hyperventilation and hypoventilation refer to minute ventilation. Minute ventilation is the volume of air the person breathes in one minute- the depth (tidal volume) and how many breathes (respiratory rate). Hyperventilation is excessive minute ventilation to remove carbon dioxide, generally to correct acidosis, and hypoventilation is lower minute ventilation to retain carbon dioxide to correct metabolic alkalosis or, more commonly, from some pathology. Tachypnea and hyperventilation are not the same. One can hyperventilate with slow respiratory rates (Kuss Maul breathing from diabetic ketoacidosis).

Respiratory Rate- Tachypnea is high rate (often a high rate is mistakenly called hyperventilation but one can hypoventilate with fast respiratory rates when chest wall is constrained or poor lung compliance), bradypnea (slow reate), and apnea refer to the respiratory rate.

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

Tidal volume- Hyperpnea and hypopnea refer to tidal volume. Hyperpnea is deep breathing and hypopnea is shallow breathing.

Oxygenation Hypoxia and hypoxemia can be confused, with hypoxia commonly used to refer to arterial blood oxygen levels. . While hypoxia is commonly used in place of hypoxemia, we reserve hypoxia for absolute concentrations of oxygen in the environment or tissue and hypoxemia for the relative concentration of oxygen in the blood.

To avoid confusion, we will define the following terms, from the environment to the tissue:

Ambient or environmental hypoxia- this is found at high altitude, acutely at 10,000 feet or more or enclosed space where chemical reactions (oxidation reaction) consume the oxygen. The first is low partial pressure of oxygen and the latter is low fraction of inspired oxygen.

Alveolar hypoxia- this is the amount of oxygen in the alveolus which will be affected by oxygen levels in the environment and very high carbon dioxide levels in the blood that replace oxygen. It is important for treatment of pulmonary hypertension as low alveolar oxygen (alveolar hypoxia) causes constriction of the pulmonary arteries and possible failure of the right ventricle. This is the method of death from Obstructive Sleep Apnea or bronchopulmonary dysplasia (BPD) from prematurity.

Hypoxemia- Low arterial oxygen levels, usually below 90%.

Tissue hypoxia- Low oxygen levels in the tissue leading to anaerobic metabolism.

Resistance, Airway Laminar flow- Resistance is proportional to the fourth power of the radius (1/r4), small changes in radius disproportionally increase resistance, a great danger from bronchospasm, bronchoedema, or secretions (a significant problem in low humidity regions).

Turbulent flow- Resistance in turbulent flow is proportional to flow velocity, agitation, anxiety, fear, and pain increase respiratory causing increase in resistance (a significant problem and upper airway obstruction such as croup).

Sensation The feeling of suffocation comes from inadequate stimulation of stretch receptors in the lung, including the vagus nerve. Poor oxygenation or ventilation do not cause this sensation, hypoxemia causes fatigue or euphoria and hypercarbia causes sleepiness.

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

Time constant Resistance X Compliance; this is the time in seconds for 63% of the lung to empty or fill; determined by airway resistance and lung/chest wall compliance; important to note that increased pressure on ventilator bag DOES NOT change flow rate.

Ventilation The pulmonary removal of carbon dioxide from the blood by minute ventilation (the kidneys can also remove carbon dioxide though this can take a few days to come on line). This is separate and distinct from oxygenation though the element of hypoventilation as a shared cause.

Visual Respiratory Evaluation- CRAWL This exam is a visual exam useful as you approach a patient, monitoring a patient from a distance or multiple patients, in presence of high ambient noise, response to treatment, and patient description.

Color- Hypoxemia Cyanosis occurs when there is 4-5 gm/dL of deoxygenated hemoglobin present while hypoxemia is defined as abnormally low arterial oxygen levels. An anemic person will be cyanotic at much lower oxygen levels than someone with normal hemoglobin levels, and tissue with slow blood flow may be cyanotic when other tissues are not. (Think of blue lips in a cold child who won’t get out of the swimming pool.) This is why we differentiate central cyanosis (arterialized blood in mucus membranes like the gums and tongue) from peripheral cyanosis (lips in a cold child or the digits of a patient with compromised peripheral blood vessels.) Saturation levels less than 90% are generally considered hypoxemia but a healthy person may show few symptoms other than impaired judgment at 80% saturation while a patient with pulmonary hypertension may have cardiac strain at levels less than 95%.

Descriptors- Cyanosis describes an absolute amount of de-oxygenated hemoglobin, pulse oximetry describes the ratio of oxygenated red cells; ALWAYS give supplemental oxygen with the pulse oximetry value for effective interpretation.

Respiratory rate and rhythm The adult diaphragm has slow twitch muscle fibers resistant to fatigue, meaning they cannot increase their respiratory rate significantly but may “tolerate” tachypnea for a period before someone calls 911. Children have fast twitch muscle fibers that are not resistant to fatigue, meaning they can breathe much faster than expected (infants can reach over 100 breathes per minute) but will fatigue precipitously. Because respiratory muscle fatigue is a major factor in respiratory distress, it is important to note that an increasing respiratory rate may indicate greater respiratory reserve while a decreasing respiratory rate is ominous, indicating imminent

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

respiratory failure. A “normal” respiratory rate may actually be the number you observe during this deterioration.

Respiratory rhythm can help determine non-pulmonary tachypnea or, in children, failure of the diaphragm. Infants use the abdomen as an accessory respiratory muscle when the diaphragm fails. The intercostal muscles, respiratory muscles in the adult but not for infants, will contract to make the chest wall firm during abdominal breathing. You will see this “see saw” breathing pattern as the child rests the diaphragm. Apnea can occur slowly or suddenly. When it occurs suddenly in the infant and responds to stimulation of the child it is more likely to be RSV bronchiolitis.

Non-pulmonary causes of tachypnea are important to note or you will pursue respiratory treatments and miss metabolic acidosis from diabetic ketoacidosis, hypovolemia, or certain drugs. Pain, agitation, and psychogenic tachypnea are also causes of non-pulmonary tachypnea.

Descriptors- respiratory rate (as a value, use of “normal” or “WNL” as in “We Never Looked” cannot be used to evaluate change or trajectory of the patient’s course); apnea, Kuss-Maul, in infants there is sudden apnea (think of RSV bronchiolitis, gastroesophageal reflux, or ALTE), abdominal breathing or see saw breathing in infants.

Air entry This is chest expansion. For normal quiet breathing it is surprisingly small, look around you to observe how much expansion you need for a normal patient when you hand ventilate. If they are expanding their chest to a great degree there is something going on. If they are working hard to breath and their chest is not expanding well, there is something serious going on.

The second thing to observe for air entry is prolongation of inhalation or exhalation (Inspiratory- Expiratory, or I:E, Ratio) . Normal ratio is 1:2, whether a large or small breath. Prolonged inspiration indicates upper airway obstruction while prolonged expiration indicates lower airway obstruction.

For upper airway obstructions it is useful to identify the level of lesion, above or below the vocal cords. Drooling, leaning forward for excessive secretions, or gagging is associated with supraglottic lesions, above the vocal cords. Coughing, “barky” cough, or hoarseness is associated with subglottic lesions, below the vocal cords.

Although we think of this as wheeze vs. stridor the limitation of sound is in the need for sufficient respiratory effort to produce sound, the ambient noise on scene or in the ambulance, and the benefits of a visual exam as you approach the patient or observe the patient from a distance.

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

Descriptors- Good-fair-poor air entry Inspiratory:Expiratory ratio (I:E ratio) as 1:2 (normal), 1:4 (lower airway obstruction), 4:1 (upper airway obstruction)

Work of Breathing The earliest sign of increased effort is nasal flaring. Though more pronounced in infants, it also occurs early in adults. You can feel the difference when you compare the sensation of resistance with rapid nasal breathing followed by pushing the tip of your nose upward.

We can evaluate this from actual work and from retractions. Increased work of breathing is associated with high heart rate, diaphoresis, and anxiety. This may help discriminate between pulmonary and non-pulmonary tachypnea as the latter has less work of breathing associated with it.

Retractions start at the most compliant part of the chest, subcostal and lower ribcage, moving upward to the subclavicular and even supraclavicular chest. This is a useful observation for deterioration or improvement in response to the therapy you administer.

Descriptors: Heart rate, diaphoresis, retractions- subcostal intercostal, subclavicular, supraclavicular, increasing superior on chest or decreasing inferior on chest,

Level of consciousness Although the most sensitive indicator for level of distress and degree of oxygenation and saturation, it is also the least specific as numerous other conditions share this finding. It can guide response to therapy if the decreased in consciousness is from respiratory system dysfunction. You can also see how easily you may “over-treat” a patient with chronic central nervous system disease, decreased blood flow to the brain, or acute CNS injury. And that is OK.

Descriptors- infant regards parents, awake and alert, apprehensive, non-responsive

Interpretation of CRAWL Exam Impending Respiratory Failure- Increased work of breathing with poor air entry Upper Airway Obstruction- prolonged inspiratory phase (4:1) Supraglottic lesion- hyper-reflexic gag, drooling, leaning forward, sitting upright, resistance being placed prone Subglottic lesion- cough, especially “barky” cough from inflamed vocal cords, hoarse voice Lower Airway Obstruction- prolonged expiratory phase (1:4)

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

Pathophysiology We can divide respiratory function into three parts: Oxygenation, Ventilation, and Sensation

Oxygenation- the enrichment of blood with oxygen, a rapid process as the combination of an oxygen molecule to hemoglobin contorts the molecule for another oxygen molecule to bind even faster. The rate of binding is faster for each oxygen molecule from number 1 through 4, meaning that an individual hemoglobin molecule is either 100% saturated or has no oxygen bound to it.

Ventilation- the removal by the lungs of carbon dioxide to maintain pH balance in the body, a feature shared with the kidneys, though at a slower rate than the lungs.

Sensation- the feeling of suffocation, dyspnea, air hunger, fighting/bucking the ventilator from stretch receptors in the lung, contributed in large part by the sensory function of the vagus nerve.

You can feel this change in sensation by taking a deep breath. Watching a rookie concentrate on an activity and you may see shallow breathing, telling the rookie to “Breathe” can reduce the anxiety they feel, which is partly from this breathing pattern. You can also feel the sensation of suffocation by breathing shallow and rapidly, something you can do for a spell. Then, take a large breath and, without letting the air out, pant. The sensation is uncomfortable despite the same minute ventilation and without changing your blood gas levels.

This is relieved with assisted ventilation by using faster inspiratory times and larger tidal volumes for the “stretch” sensation and a bit higher respiratory rate because of anxiety and pain.

Oxygenation- 5 causes, 2 treatments

Problem Treatment Low FiO2 (altitude, enclosed space) Supplemental oxygen Hypoventilation Positive pressure breathing Cardiac shunt No field treatment Pulmonary shunt, V/Q mismatch Supplemental oxygen Positive pressure breathing Diffusion abnormality No field treatment

Lateral positions- sometimes low oxygen saturation is from a local lung lesion (pneumonia or a stab wound). Laying the patient with the good side down increases the blood flow, this increases oxygen saturation. You can also lay your patient on each side to identify if the oxygen saturation changes

Oxygen therapy Minimal Titratable Oxygen- if we titrate supplemental oxygen to maintain oxygen saturation of 95% we can identify the severity of the lesion and response to therapy. If we can wean supplemental oxygen we identify response to therapy, if we are increasing it we can help

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

identify the trajectory of deterioration (rate and degree) to help prepare the hospital for intervention. ALL patients must be titrated to 95% oxygen saturation unless indicated for different level; when oxygen therapy is titrated time line is produced giving valuable information such as trajectory and response to therapy.

Ventilation- 4 mechanisms Secretions (bronchrrhea) Spasm (bronchospasm) Edema (bronchoedema) Anatomic (foreign body, airway structure, other body structure impinging on airway)

Secretions- thick secretions can severely occlude the airway in, particularly in infants and children, can create a plug that completely blocks the airway. They respond to enteric fluids in a few minutes. Use of saline to lavage the airway helps but will not make the secretions already present any thinner.

Spasm- responds to bronchodilators.

Edema- from immune response will respond to aerosol steroids in about an hour (stops the capillary leak around the airway) and oral or IV steroids in four hours (suppression of bone marrow and white cell production that infiltrates the airway).

Anatomic or foreign body- will have sudden onset and generally be unilateral. No field treatment is available as these must be treated using rigid bronchoscopy by a surgeon.

Asthma is an inflammatory process with secretions, spasm, and edema, generally in that order over hours. Secretions seem to have the greatest effect in early summer at the end of a hot, dry day when the patient did not keep hydrated. You will see poor response to a bronchodilator. Drinking water can help loosen secretions. For asthma symptoms lasting longer than 12 hours you may also see poor response to a bronchodilator as the patient may have developed bronchoedema.

Dynamic hyperinflation During status asthmaticus both respiratory rate and airway resistance increase. This can lead to higher airway resistance from the faster air flow, shifting resistance from laminar (based on radius) to turbulent (based on flow velocity). There are a few other factors but basically this lead to trapped air because of air flow and respiratory rate (dynamic resistance changes). Air is trapped in the lung, hyperexpanding it, causing what is called “inadvertent PEEP’ (PEEP is Positive End-Expiratory Pressure, like CPAP but while breathing whereas CPAP is constant flow).

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

One treatment is to give back pressure at low amounts of 6-10 cm H2O. The danger is that you will increase inadvertent PEEP and possibly cause a pneumothorax. The way you identify if your back pressure is working is immediate change in I:E ratio from 1:4 to 1:2 and a decrease in end-

tidal CO2. If the I:E ratio increases toward 1:5 or higher or the end-tidal CO2 increases, you must immediately stop as you are making things worse. This is a risky treatment to be used only by

paramedics who understand this dynamic and in patients with high CO2 and low oxygen saturation.

[Helium works to treat asthma by its viscosity; it is dynamic (kinematic viscosity) and the faster it flows the more viscous it becomes. Think of Silly Putty, pull it slowly and it stretches, pull it fast and it breaks.]

Pulsus paradoxus In severe upper or lower airway obstruction the inspiratory pressures can become very negative,

-35 cm H2O or greater. The left ventricle is within the chest cavity and experiences this negative pressure while pumping against the normal Mean Arterial Pressure. The pressure difference, because of the greater negative pressure, is high- this is an increase in afterload. This increased afterload lowers cardiac output during each inspiration, lowering the blood pressure with inspiration.

Time constant This is a value that tells you how long 63% of the lung empties or fills. For those with electronics background, it is the same as in capacitance- how the defibrillator holds its charge before shocking the patient. The time constant is found by multiplying the resistance of the airways by

the compliance of the lung TC = R X C.

You can see that pressure is not a part of this equation. If the upper airway is obstructed then pressing the ventilator bag harder does not make it flow faster, the air simply goes into the stomach. If the lower airways are obstructed, then it takes longer for air to evacuate the lung. Breathing faster simply stacks more air in the lung, causing higher inadvertent PEEP and

increased CO2.

For upper airway obstruction, hold gentle pressure and wait for the lung to fill. For lower airway obstruction, wait for the breath to finish exhaling before you provide the next breath.

Non-pulmonary tachypnea Increase sympathetic tone is a common finding in many of the medical conditions encountered in EMS. This has led caregivers to misdiagnose pain, hypovolemia, and toxic ingestions among a number of misdiagnosis that can occur. Nonpulmonary causes of tachypnea include fever, pain, anxiety, metabolic acidosis, hypovolemia, and heart failure. These can be identified by >95%

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

oxygen saturation on room air, good chest expansion and air entry, I:E ratio of 1:2, and absence of retractions.

Psychogenic hyperventilation or anxiety This is commonly encountered in EMS. First, evaluate for respiratory signs and symptoms, the patient will have evidence described above of nonpulmonary tachypnea. Ask the patient to give his or her name and address, do not let others answer (you may tell them you are checking their mental status, which is true). If organic disease exists driving the respiratory rate the patient cannot answer well. In cases of psychogenic hyperventilation the patient will slow the respiratory rate.

* It is critical for EMS caregivers to recognize that psychogenic hyperventilation or false claims of asthma or other respiratory illness may be a method for the patient to escape a dangerous situation or domestic violence. In these cases the EMS professional must evaluate the social dynamics and err on the side of removing the patient from that environment.

CPAP/PEEP Recruiting alveoli The alveoli should be open without compressing blood vessels, which stops blood flow and forces the right ventricle to work harder. You will feel the right amount when you hand ventilate a breathing patient, the lung is surprisingly soft in your hand.

When alveoli have a long time constant they will not open during the time of inspiration, leaving them deflated and nonfunctional. The result is hypoxemia. A little backpressure will keep them open at the start of inspiration, basically recruiting alveoli, and improve oxygenation.

Overcoming dynamic hyperinflation Dynamic hyperinflation occurs in some cases of lower airway obstruction when expiration causes collapse of the airway, trapping air in distal alveoli and airways. CPAP or PEEP gives a back pressure that will stent the airway open allowing full expiration and removal of CO2. You can see this effect with the drop in end-tidal CO2 and faster expiratory phase- the I:E ratio almost immediately goes to 1:2.

Use of CPAP or PEEP in lower airway obstruction is both a dangerous and life-saving procedure. The danger comes from (1) sensation of suffocation causing the patient to resist and fight mask ventilation, (2) hyperexpansion of the lung with decreased minute ventilation, and (3) creation of regional differences in backpressure (increased inadvertent PEEP) that can rupture to cause tension pneumothorax and death.

The benefit comes from unloading the volume of the lung when the back pressure.

If CO2 rises IMMEDIATELY stop CPAP/PEEP. In presence of dynamic hyperinflation you will see I:E ration change from 1:4 to 1:2 in only a few breaths and CO2 will rapidly decrease.

Airway, Mask Ventilation Riverside (County) EMS Agency 26 October 2015

Mask ventilating a breathing patient

Purpose To learn mask ventilation of a breathing patient

To hand ventilate for improvement of oxygenation and ventilation while also relieving the sensation of suffocation. You can feel this quite easily with your hand.

Tidal volume is reached quite easily with one hand, 3-4 fingers depending on age of patient. Watch for the rise in the chest, do not overdo it.

Rate is based on time constant; allow the air to leave before the next breath.

CPAP or PEEP is tried if oxygen saturation does not improve. At some point you might try this with room air to see if it is a purely mechanical problem.

Procedure Rapid and shallow breathing, you will intervene at some point before the next breath

Slow and deep breathing, you will blow of CO2 and the patient will relax

DO NOT try to ventilate as the patient begins a breath or begins to breath, the response time from visual recognition to motor action is too long and you end up ventilating as the patient exhales creating ventilator-patient asynchrony.

When you feel this you realize how soft the lung is and sensitive your hand is to obstruction and CPAP/PEEP.

The role player will suddenly lose the drive to breathe and feel comfortable. Any deviation causes immediate discomfort and the role player will signal you with a “thumbs down.”

The breathing patient

- For oxygenation use back pressure (PEEP) - For ventilation use enough pressure to expand the chest - For sensation use faster inspiration, larger tidal volume, and maybe a higher rate if anxiety or pain is present. - For upper airway obstruction hold pressure on the bag, allowing the chest to fill. - For lower airway obstruction let all the air out of the chest. - If you find yourself ventilating at an uncomfortably slow rate increase the tidal volume to achieve good minute ventilation; let the end-tidal CO2 be your guide.

Report all cases of mask ventilation of breathing patient to REMSA for Lessons Learned.