Respiratory Assessment and The Mechanics of Ventilation

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Respiratory Assessment and The Mechanics of
Ventilation

• Gena Costello RN
• Pediatric Critical Care Series
• Connecticut Childrens Medical Center
• Hartford, CT

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Objectives

• The participant will be able to define components
  of lung mechanics and ventilation.
• The participant will be able to list five
  examples of anatomic differences in the pediatric
  airway.
• The participant will be able to describe how
  edema affects the pediatric airway.
• The participant will be able to list five signs
  of increased work of breathing.
• Review differences among respiratory distress,
  respiratory failure, and respiratory arrest.

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Apology

• IF, THROUGH OMISSION OR COMMISSION, I
  INADVERTENLY DISPLAY ANY SEXIST, RACIST,
  CULTURALIST, NATIONALIST, REGIONALIST, AGEIST,
  LOOKIST, SIZEIST, INTELLECTUALIST, ETHNOCENTRIT,
  SOCIOECONOMICIST, EDIST, OR OTHER TYPES OF BIAS
  AS YET UNDISCOVERED, I APOLOGIZE AND ENCOURAGE
  YOUR SUGGESTIONS FOR RECTIFICATION.

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Lung Mechanics

• Breathing, the physical act of moving air in and
  out of the lungs.
• Ventilation happens through inspiration and
  expiration. The actual gas exchange! Goal is too
  deliver adequate volume utilizing lowest
  pressures!
• These are affected by the mechanical properties
  of the
• Lung
• Chest wall
• And the inspired air

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Lung and Chest Wall

• Lung tissue composed of elastic tissue
• No innate resting volume
• Volume increases proportionately to distending
  pressure

• Chest wall also contains elastic tissue
• Fixed rib cage determines volume
• Tendency of chest wall to expand is balanced by
  tendency of lung to collapse
• Creates negative pressure in pleural space

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Functional Residual Capacity(FRC)

• Lung volume that exists at the end of expiration
• Point at which elastic recoil of lungs and chest
  wall balance out
• This volume of air allows continual O2 uptake
  and CO2 elimination even when there are no active
  breaths
• Equal to 30ml/kg

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Airway Resistance

• Friction develops as gas molecules pass over each
  other and the airway walls
• Resistance inversely related to the radius of the
  airway
• Resistance also related to secretions and anatomy

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Tidal Volume and Physiologic Dead Space (VD)

• Amount of air exchanged with each breath
• Equal to spontaneous 3 to 5 ml/kg- ventilator
  breaths 5 to 7ml/kg
• Variable portion of each breath that is not
  involved in gas exchange

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Respiratory Assessment

• Introduction
• Background
• Anatomy
• Physiology
• Assessing Respiratory Function
• The 3 Rs

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Pediatric Cardiopulmonary Arrests
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10
80

• Almost all pediatric codes are of respiratory
  origin

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Age distribution of arrests
Arrests
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14
13
12
11
10
9
8
7
6
5
4
3
2
1
lt7 mos
7-12 mos
Age (years)
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The Pediatric Airway
Children are very different than adults !!!
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Those ABs

• Assess airway patency
• Breathing effectiveness rise and fall of
  chest,respiratory rate, depth/equality of
  breathing, rhythm of respirations, signs of
  increased work of breathing, and breath sounds

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Focused Assessment

• The history can be obtained while you are
  performing your physical exam.
• The initial recognition of respiratory distress
  is more important than determining the cause!
• While assessing
• Let the child remain with the parent/caregiver
  and maintain a position of comfort if at all
  possible!
• Approach as gently as possible-anxiety increases
  O2 requirements.
• Start with the least invasive assessments first.

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Assessment continued

• Note WOB-location and depth of retractions, nasal
  flaring, grunting, and use of accessory muscles.
• Presence of inspiratory or expiratory wheezes or
  inspiratory stridor
• Quality of breath sounds diminished or absent.
• Changes in skin color pallor, mottling, or
  cyanosis.
• Changes in mental status confusion or inability
  to recognize caregiver.
• Restlessness or fatigue.

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Anatomy Nose

• Nose is responsible for 50 of total airway
  resistance at all ages
• Infants are obligate nose breathers
• Infant blockage of nose respiratory distress
• Look for any FB

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Airway Anatomy Mouth/Throat/Pharynx

• Tongue relatively larger to the oropharynx, and
  is frequent cause of upper airway obstruction
• Loss of tone with sleep, sedation, CNS
  dysfunction
• Inspect for injury or swelling
• Note the color of the mucus membranes
• Any fluids ie vomitus, sputum, blood?
• Are there broken teeth?

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Airway Anatomy Larynx

• High position
• Infant C 1
• 6 months C 3
• Adult C 5-6
• Anterior position
• Listen for any hoarseness, inability to talk

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Airway Anatomy Larynx

• Narrowest point cricoid cartilage in the child

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Anatomy Epiglottis

• Relatively large size in children
• Flaplike structure-overhangs/covers the entrance
  to the trachea
• Floppy not much cartilage
• Narrow and long

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Chest

• Inspect WOB, symmetry of movement, use of
  accessory muscles, retractions note abnormal
  breathing patterns
• Auscultate equality of breath sounds,
  adventitious breath sounds(crackles, wheezes)
• Palpate for chest wall tenderness, symmetry of
  chest wall expansion, subcutaneous emphysema

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Airway Anatomy Children Are Different
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Airway Anatomy
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Summary Anatomic Differences

• smaller airway diameters / shorter in length
• -more likely to be affected by obstruction
• cartilage chest wall muscles less developed
• unable to increase Tv as effectively as adults
• narrowest point differs
• implications for subglottic stenosis
• epiglottis larger floppier
• significant implications when infected

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How Edema Effects Pediatric Airway

• One mm of concentric edema in a newborn trachea
  (radius approximately 2 mm) increases resistance
  about 16 times!!
• One mm increase in edema can reduce the airway
  lumen by 75 causing life-threatening airway
  obstruction.

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How Edema Effects Pediatric Airway

• Symptoms of laryngeal edema will include
• Croupy cough
• Hoarseness
• Stridor
• Increased restlessness
• Tachypnea
• Accessory muscle utilization with paradoxical
  movement of the chest and abdomen

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Adult Airway
Infant Airway
less smooth muscle
more smooth muscle
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Normal Airway
Airway with Edema and Bronchospasm
lumen
lumen surface area remains constant
smooth muscle
Airway with Edema
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Assessing Respiratory Function

• Respiratory Rate
• Oxygen Saturation
• Respiratory Effort
• Audible Airway Sounds

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Assessing Respiratory FunctionRespiratory Rate

• Tachypnea is the first sign of respiratory
  distress
• an attempt to normalize pH by increasing minute
  ventilation
• easily overlooked
• Bradypnea is an ominous sign.
• May be caused by fatique, hypothermia, or CNS
  system depression, among other things
• when need to increased minute ventilation, need
  to increase RR
• Slow or irregular breathing in an acutely ill
  child can also be an ominous sign
• Best evaluated before examining/touching child

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Assessing Respiratory FunctionOxygen Saturation

• Fifth vital sign?
• Measure of the amount of oxygen bound to Hb
• Measured by pulse oximeter
• Can be difficult to obtain in poorly perfused pts
• Questionable validity in patients with
• Sickle cell disease, severe anemia, CO poisoning,
  cyanide poisoning

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Respiratory Distress

• Defined as an increased work of breathing.
• Characterized by the presence of increased
  respiratory effort, rate, and work of breathing

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Signs of Respiratory Distress

• Tachypnea
• Tachycardia, mild
• Grunting
• Stridor
• Head bobbing
• Flaring
• Inability to lie down
• Irritability, restlessness, anxiousness

• Retractions
• Wheezing
• Sweating
• Prolonged expiration
• Pulsus paradoxus
• Apnea
• Cyanosis, resolves with O2 administration

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Signs of Respiratory Distress

• Retractions
• Occur during inspiratory phase
• Retractions accompanied by inspiratory stridor
  suggest upper airway obstruction
• Retractions accompanied by grunting suggest
  decreased lung compliance
• May be accompanied by head bobbing or abdominal
  breathing

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Signs of Respiratory Distress

• Grunting
• Produced by premature glottic closure accompanied
  by late expiratory contraction of the diaphragm
• Increases airway pressure and FRC
• A sign of small airway collapse, alveolar
  collapse or both

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Signs of Respiratory Distress

• Stridor
• High pitched sound during inspiration
• A sign of extra-thoracic airway obstruction
• Causes include malacia, infections (croup, etc),
  upper airway edema (allergic rxn) or aspiration
  of a foreign body

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Signs of Respiratory Distress

• Wheezing
• A sign of intra-thoracic airway obstruction
• When accompanied by prolonged exhalation, a
  further sign of small airway obstruction
• Causes include asthma bronchiolitis

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Signs of Respiratory Distress

• Nasal Flaring Head Bobbing
• Signs of significantly increased respiratory
  effort

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Respiratory Failure

• Defined as a clinical condition in which there is
  inadequate blood oxygenation and/or ventilation
  to meet the metabolic demands of body tissues.
  

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Signs of Respiratory Failure

• Cyanosis
• Decreased level of responsiveness
• Poor skeletal muscle tone
• Inadequate respiratory rate,effort, or chest
  expansion
• Apnea

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Disordered Control of Breathing

• Hypoventilation which may be due to
• Abnormal breathing pattern breathing funny
• Inadequate respiratory rate or effort despite
  increased need
• periods of increased effort followed by decreased
  effort

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Respiratory Arrest

• Defined as the absence of breathing

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Signs of Respiratory Arrest

• Mottling peripheral and central cyanosis
• Unresponsive to voice and touch
• Absent chest wall motion
• Absent respirations
• Weak to absent pulses
• Bradycardia or asystole
• Limp muscle tone

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Summary of Differences in Infants

• Infants are obligate nose breathers until 2-3
  months old
• Upper airway is relatively more sensitive to
  inhalation agents, more prone to collapse
• Have less oxygen reserve, so hypoxemia occurs
  relatively more rapidly
• Have metabolic rate twice as high as adult
• Lung compliance is higher than in adults
• Have less reserve in lung surface area

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Conclusions

• Most arrests in pediatrics are respiratory
• The pediatric airway has age-related anatomical
  features that will change how you evaluate and
  treat and the pediatric patient with respiratory
  distress
• Careful assessment is necessary to identify
  pediatric patients with impending respiratory
  failure
• Goal is to prevent further deterioration!

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