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57 Cards in this Set
- Front
- Back
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What parts of the lung are developing during weeks 6-17? |
Conducting zones (1-17) -entire air collecting bronchial tree -terminal bronchioles -(pseudoglandular period) |
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What parts of the lung are developing during weeks 17-24? |
Respiratory zone (17-23) -respiratory bronchioles -capillaries adjacent to respiratory bronchioles -lung becomes more vascular -(canalicular period) |
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At _____ weeks, _____ pneumocytes begin to produce surfactant. |
24 weeks Type II pneumocytesproduce surfactant |
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What occurs during the period from 24 weeks to term? |
Alveoli form -type II pneumocytes produce surfactant -rapid proliferation of capillaries around alveoli -alveoli develop from sacules (week 32-36) -alveolar (terminal sac) period |
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During the post-natal period alveoli increase in number until _____ years of age Alveoli grow in size until when? |
Alveoli increase in number until 8 years of age Alveoli increase in size until chest wall growth ceases (adolescence) |
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Full term newborns have _______ alveoli Adults have _________ alveoli |
Newborns = 25 million alveoli Adults = 300 million alveoli |
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How do airways (bronchioles and bronchi) grow during childhood. |
Increase in length and diameter |
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How much do fluid do fetal lungs produce?
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50-150 mL/kg/day Ultrafiltrate |
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What is the purpose of the alveolar fluid? |
Expands airways and helps stimulate lung growth. Expelled from lungs making up 1/3 of amniotic fluid |
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At any given time the fetal lung contains how much fluid? |
30 mL/kg (up to 2/3 expelled during birthing process) |
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What triggers initial neonatal breaths? |
-touch, temperature, environment -respiratory/metabolic acidosis |
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How is fluid expelled from lungs |
-2/3 expelled during vaginal birth -initial breaths generate negative pressures (-40 to -60 cm H2O) -overcomes high surface tension -air fills lungs/fluid expelled from upper airways -residual fluid absorbed by pulmonary lymphatics |
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Delayed removal of residual fluid in lungs can lead to ________- |
transient tachypnea of the newborn (24-72 hours) |
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_______________ initiates rhythmic breathing |
clamping of umbilical cord |
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____________ during air breathing augments continual rhythmic breathing? What is the consequences of this? |
Relative "hyperoxia" maintains breathing. Therefore, hypoxia depresses/abolishes continual breathing |
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How does neonatal CO2 compare to that of older children/adults? |
Lower - usually around 28 mmHg. -Due to poor buffering capacity in neonates -Compensates for metabolic acidosis at birth |
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An adequate amount of _________ is necessary for smooth transition to air breathing |
Surfactant |
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What is the consequence of inadequate surfactant levels? |
-collapse of alveoli -maldistribution of ventilation -impaired gas exchange -poor lung compliance -increased work of breathing -Infant Respiratry Distress Syndrome (IRDS) |
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The infant chest wall is highly ____________ Why? What are the consequences of this? |
Highly Compliant -ribs extend horizontally/provide minimal assistance in chest wall expansion -floppy chest wall Consequences -limited ability to increase tidal volumes -collapse inward during inspiration (paridoxical breathing) |
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When is paridoxical breathing seen in? -Premature neonates -Term neonates -Infants/children |
Preemies = always Term = during REM sleep Infants/children = during exertion |
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What role do the intercostal muscles play in neonatal respiration? |
Play an active role due to highly compliant chest wall. |
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Describe the composition in neonatal and infant intercostal muscles |
Deficient in TYPE I muscle fibers -until 2 months of age -prone to ventilatory failure during inc. WOB -intercostal muscles depressed under GA (leads to paradoxical breathing) |
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________________ is the primary ventilatory muscle during infancy |
The diaphragm |
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Compare the neonatal diaphragm to the adult diaphragm |
Sits high in thorax Deficient in TYPE I muscle fiber -prone to fatigue |
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Where are the central chemoreceptors located? |
Ventrolateral medulla |
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Describe how the central chemoreceptors function. |
Indirect response to CO2 -respond to increase H+ in CSF -increase Vt and RR -response directly related to age |
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Describe how the peripheral chemoreceptors in infants function. |
React rapidly to changes in PaO2 and pH
-most responsive to PaO2 < 60 mmHg -will lead to significant increase in ventilation |
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Where are the peripheral chemoreceptors located? |
Carotid bodies and aortic arch |
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Describe the neonatal response to hypoxia |
Transient increase in ventilation (short) -Quickly causes sustained ventillatory depression *automatic ventilatory depression in response to hypoxia for premature infants |
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Describe the effects of hypothermia, acidosis, and hypercarbia on the response of a premature infant to hypoxia. |
Immediate and profound respiratory depression |
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Describe the Hering-Breuer reflex in neonates |
A protective reflex that induces apnea in response to significant lung inflation. -stretch receptors on bronchial smooth muscle -reflex inhibition of respiration -Strong/physiologically relevant in neonates |
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What is periodic breathing? |
Recurrent pauses (apneic spells) lasting 5-10 seconds (without desaturation/cyanosis) |
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What is the incidence of periodic breathing in infants? |
93% of premature neonates 78% of full-term neonates |
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What is central (clinical) apnea of infancy? |
Unexplained apnea lasting > 15 seconds -or- Any apnea with -bradycardia (HR < 100) -cyanosis -pallor -loss of muscle tone |
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What is the incidence of central clincal apnea? |
Rare in term neonates Up to 55% of premies |
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Treatment for central clinical apnea of infancy |
Terminated by tactile stimulation/BVM -Theophylline -Caffiene -PEEP |
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Major risk factors for post-operative apnea |
Prematurity (< 55 weeks post-conception) Previous history of central clinical apnea |
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Patients at risk for post-operative apnea should be monitored for __________ hours |
24 hours
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Neonates are obligate ________ breathers |
Nasal (until 3-5 months) |
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Describe five features of the neonatal airway |
Large tongue (obstructs) Stiff/U shaped epiglottis Laryx = cephalad, anterior Large arytenoids Slanted vocal cords |
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What is the distance from cords to carina for: -neonates -1 year old |
3-5 cm 5-9 cm |
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The narrowest portion of the airway is ________________ |
The cricoid ring |
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Diameter of newborn trachea |
4 cm |
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Compare neonatal and adult alveolar ventilation |
Neonate = 130 mL/kg/min Adult = 60 mL/kg/min |
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Compare neonatal and adult respiratory rate |
Neonate = 35/min Adult = 15/min |
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Compare neonatal and adult tidal volume |
The same (about 6 mL/kg/min) |
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Compare oxygen consumption for: -premies -infants -adults |
9 mL/kg/min 6 mL/kg/min 3 mL/kg/mg |
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What is the clinical implication of neonates consuming TWICE as much oxygen/kg/min as an adult? |
Rapid desaturation during periods of apnea |
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Neonates increase alveolar ventilation by increasing ____________ |
respiratory rate |
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Respiratory rates -neonate -infant -toddler -preschooler -school age -adolescent |
Neonate = 30-50 Infant = 20-40 Toddler = 20-35 Preschooler = 20-30 School age = 16-25 Adolescent = 14-20 |
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Functional Residual Capacity (Adults vs Infant) * what are the consequences of this? |
Infant = 30 mL/kg Adult = 34 mL/kg *More rapid inhalation induction/emergence ** more rapid de-saturation |
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Compare TLC (Adults vs infant) |
Infant - 63 mL/kg Adult - 82 mL/kg *diaphragm & inspiratory muscles under-developed |
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Closing volumes infants vs. adults |
Infants = falls within normal tidal volume
-neonates prone to atelectasis/hypoxia |
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P50 for HbF |
17 mmHg (HbA = 26 mmHg) |
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HbF releases O2 less readily at the tissues. What adaptations does a neonate have that allow for adequate oxygenation? |
Hbg = 17-18 mg/dL at birth |
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Fetal hemoglobin is shifted ________ |
left |
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What is the Hb composition at birth? |
80% HbF 20% HbA |
