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The newborn period is from birth through the 28th day of life
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Neonatal transition is the period of the first few hours of life where the newborn stabilizes respiratory and circulatory functions
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practice breathing movements in utero help :
- develop lung tissue
- strengthen respiratory muscles
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Fetal lung development in the first 20 weeks of gestation is limited to:
differentiation of pulmonary, vascular and lymphatic structures
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20- 24 weeks gestation the _____ _______ begin to appear followed by ______ ______ at 24 - 28 weeks
- Alveolar ducts
- primitive alveoli
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Type 1 cells in the lungs are necessary for ______ ______. Type 2 cells provide for synthesis and storage of ________.
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Surfactant is:
surface -active phospholipids that are required for alveolar expansion and stability
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35 weeks is when the lungs are structurally developed enough to maintain good lung expansion and adequate exchange of gases
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FBM = Fetal breathing movements are :
- begin around age 17-20 weeks gestation
- essential to develop chest wall muscles and diaphragm
- regulating lung fluid volume --> lung growth
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What 2 things MUST occur to initiate breathing and begin adequate lung function?
- Lung expansion and pulmonary ventilation
- increase in pulmonary circulation \
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FBM decreases appx 24 - 36 hours prior to birth
to prepare lungs
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80 - 100 ml of fluid remain in lungs at birth
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fetal chest compression during birth and reflexive recoil of chest at delivery create negative intrathoracic pressure ...expelling fluid out of lungs and creating passive inspiration to fill the space vacated by the fluid
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the first inspiration creates high intrathoracic pressure, which distributes the inspired air across the alveoli and begins the FRC (functional residual capacity)
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FRC
amount of air remaining in the lungs at the end of a normal expiration
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most lung fluid is reabsorbed within 2 hours after birth and should be completely absorbed within 12 - 24 hours
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a bulb syringe is often used in mouth , nose to clear any additional fluid
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Difficulty initiating respirations can be from:
- 1. underdeveloped lymphatics ( decreased removal)
- 2. inadequate compression of the chest wall in small infants ( overly compliant chest wall due to immature muscular development )
- 3. absence of chest wall compression with Csection
- 4. respiratory depression due to maternal analgesia
- 5. aspiration of amniotic fluid , blood or meconium
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Transitory asphyxia & inspiratory breath - result of CNS reaction to sudden pressure , temperature change and external stimuli
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first breath chemical result of :
1. hypercapnia ( elevation of PCO2)
2. Acidosis ( decrease in pH)
3. hypoxia ( decrease in PO2)
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Chemical stimuli for first breath:
- stresses of birth ( hypercapnia, transitory asphyxia, hypoxia, clamping of cord) trigger aortic and carotid chemoreceptors that trigger the respiratory center of medulla
- falling levels of prostglandins with clamping of cord
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Thermal stimuli to begin respiration :
sudden temp drop from 98.6 to 75 on moist newborn stimulates skin sensory receptors and respiration is the response
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Sensory stimuli :
1. light , sound , effects of gravity
2. painful stimuli of birth
3. joint movement proprioception
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What are the three stimuli types needed to begin respirations in the newborn?
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Name the 3 factors that oppose the first breath
- 1. Alveolar surface tension
- 2. viscosity of the lung fluid
- 3. lung compliance
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Alveolar surface tension :
contracting force between moist surfaces of the alveoli
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viscosity of lung fluid is influenced by surfactant
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lung compliance is
the ease with which the lung is able to fill with air
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Surfactant is necessary because it keeps the alveoli from collapsing after each expiration
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Cardiopulmonary adaptation:
PO2 levels increasing in alveoli triggers a decrease in pulmonary resistance, bringing additional bloodflow
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Oxygen transport is influenced by what 3 factors ?
- type of hemoglobin present
- oxygen carrying capacity of the RBC
- cardiac output
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the Cardiac output is relatively higher and contributes to rapid delivery of oxygenated blood to tissues with high metabolic demands
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The ability of the lung to maintain oxygenation and ventilation are influenced by:
- lung compliance
- airway resistance
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lung compliance in a newborn is influenced by 5 anatomical differences such as :
- 1. large heart and mediastinal structures that reduce lung space
- 2. weak intercostal muscles
- 3. rigid rib cage with horizontal ribs
- 4. high diaphragm that restricts expansion
- 5. large abdomen that restricts expansion
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Lung airway resistance in the newborn is increased in comparison to adults due to small size of radii, lenth and number of airways
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normal newborn resp rate is 30-60 BPM
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Periodic breathing : pauses in resp movement that last up to 20 sec , alternating with breathing .
rarely causes skin color/ heart changes
has no prognostic significance
occurs with REM sleep
can be very evident with motor activity, sucking and crying
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Apnea : cessation of breathing up to 20 seconds
may or may not be assoc. with skin color/heart changes
****always needs to be evaluated !!!!
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