CH 2 Neonatal Pulmonary Physiology and Pathophysiology Flashcards
A near term infant (34 - 36 weeks gestation) is at risk of presenting with what 4 pathologies?
- Hyaline membrane disease HMD
- Pulmonary Hypertension
- Sepsis
- Pneumonia
What are the most common newborn disorders treated with ECMO ?
- MAS
- CDH
- Sepsis
- Pneumonia
- Idiopathic Pulmonary Hypertension
Surfactant is composed of several phospholipids which lower surface tension of the alveolar walls.
Why is surfactant important during the initial opening of the alveolar walls?
What secretes surfactant ?
- Prevention of subsequent atelectasis
- Secreted by Type II alveolar cells in the lungs
How is HMD characterized ?
Hyaline membrane disease is characterized by:
- (lack of surfactant)
- Massive alveolar atelectasis > Hypoxia
What are 2 indicators of pulmonary maturity?
By G week 35:
- ) Lecithin : Sphingomyelin = 2 : 1
- ) Presence of Phosphatidyl glycerol (PG)
What is the major constituent of surfactant ?
Lecithin comprises 50 - 75% of all phospholipids
Control of fetal pulmonary circulation are modulated by several agents, what are the 2 most important VASODILATORS?
- Nitric Oxide
- Prostacyclin
Control of fetal pulmonary circulation are modulated by several agents, what are the 2 most important VASOCONSTRICTORS?
What are 2 secondary vasoconstrictors?
- Endothelium-1
- Platelet activating factor
Secondary Vasoconstrictors:
- Leukotrienes
- Thromboxane
A near term infant with HMD should be treated with what therapy before considering ECMO ?
- Surfactant
- HFV
- Inhaled Nitric Oxide
In term infants, what can turn off surfactant production ?
- Acidosis
- Hypoxia
Lung Compliance (CL) formula =
Volume / Pressure
Lung compliance is decreased in patients with HMD and therefore, an increase in pressure is needed for expansion of the lungs.
Lung Compliance Normal values range from ?
What values do we often see in HMD pts ?
1 - 4 cc/cmH2O/Kg
1/4 - 1/5 of the above + increase work of breathing.
What treatment should i use for a patient with HMD ?
Why ?
Continuous Positive Pressure Ventilation (CPAP)
- Opens the alveoli
- Decreases atelectasis
- Decreases the work of breathing
- Increases lung compliance
- Increases oxygenation
What are 7 predisposition factors for HMD ?
- Prematurity
- Perinatal asphyxia
- Maternal diabetes A,B,C
- Family HX of HMD
- 2nd twin
- C Section w/o labor
- Male
Risks for HMD can be decreased by doing the following:
- Glucocorticoid admin to the mother 24 - 48 before birth.
- Maternal toxemia
- Premature / Prolonged rupture of the membranes.
- Lecithin : Sphingomyelin > 2 : 1
- Presence of Phosphatidyl glycerol
How would a clinician determine if an infant is surfactant deficient and would benefit from artificial surfactant ?
Clinicians must use clinical findings.
- X-Rays
- Required intubation (ETT)
- FiO2 > 40 mmHg
Infants with HMD requiring FiO2 > .50 would benifit from recruiting collapsed alveoli. How can we achieve this ?
- Nasal CPAP
- High Flow Nasal Cannula
- Longer inspiratory times > .5 sec
- High Frequency Oscillatory Ventilation (HFOV)
Where should we keep blood gases for patients with HMD ?
pH 7.28
PaCO2 45-50 mmHg
PaO2 50 - 65
What plays a role in the development of bronchopulmonary dysplagia (BPD) ?
- Oxygen &
- Ventilator therapy
Therefore these patients should be aggressively weaned from these therapies.
How is bronchopulmonary dysplagia (BPD) characterized?
Thickening and eventual necrosis of:
- Alveolar walls
- Basement membranes
- Bronchiolar Epithelial lining layers
Atelectasis & fibrosis are present
Diffusion of Oxygen is impaired
5 - 30% pf patients with bronchopulmonary dysplagia (BPD die of what ?
- Infection
- Cor Pulmonale
Retinopathy of Prematurity (ROP) destroys the normal architecture of the eye which results in blindness. ROP is related to what?
- Hyperoxymia
- Large swings in oxygenation in the premature.
- Decrease gestational age
- Hypotension
- Acidosis
Meconium Aspiration Syndrome (MAS) is secondary to hypoxia or stress and results in respiratory distress.
What are the two forms of lung pathology that can form ?
- ) Emphysema from ball-valving or partial obstruction
2. ) Atelectatis from total obstruction
What is the major component of the pathophysiology of Meconium Aspiration Syndrome (MAS)?
1.) PPHTN
Air leaks are common
Maternal factors causing risk for MAS ?
- ) Toxemia
- ) HTN
- ) Heavy Smoker
- ) Chronic Respiratory or Cardiac disease
- ) Poor Nutrition
- ) > 42 week gestation
Mechanical Obstruction combined with Chemical Inflammation as in the case of Meconium Aspiration Syndrome (MAS) results in what ?
- ↑ PVR
- Opening of Fetal shunts
= PPHN
What neonatal population is the largest treated with ECMO ?
Meconium Aspiration Syndrome (MAS)
In regards to Meconium Aspiration Syndrome (MAS), what has been shown to turn off surfactant production ?
- Meconium &
- High Ventilation
Meconium Aspiration Syndrome (MAS) ultimately leads to PPHN, what is a common treatment for PPHN ?
- Gentle ventilation with lower peak pressures
- iNO
What should NOT be used after meeting ECMO criteria?
- Surfactant
Causes of PPHN ?
- Hypertrophy of muscular layers in pulmonary arterioles.
- Failure of the PA to relax
- Vasospasm & Constriction due to hypoxia & acidosis
- Polycythemia, Hypocalcemia, hypoglycemia
PPHN is characterized by ?
- R > L shunts
- Mixing in the Ao & LA
No difference noted in pre/post ductal blood gases would be indicative of what?
Shunt only at the PFO
A difference of 15 torr noted in pre/post ductal blood gases would be indicative of what?
Shunt at the PDA level
PPHN is diagnosed by ?
- Doppler ultrasound will reveal the PDA & PFO
- Pre/Post ductal blood gas differences
- Infant who responds to hyperventilation-hyperoxia test
- “Flip-Flop phenomenom” drop in PaO2 with small changes in ventilation
Treatment of PPHN ?
- Prevent Hypoxemia (PaO2 > 100 mmHg)
- Correct acidosis
- Partial exchange transfusion
- Correct hypocalcemia
- Gentle ventilation
- Sedation, avoid paralysis
- iNO
- Conventional ventilator & HFOV, 1 parameter changed at a time.
Congenital Diaphragmatic Hernia (CDH) involves what organs ?
- Large intestines
- Thoracic entry of the stomach
- Liver
- Spleen
What are the clinical symptoms of Congenital Diaphragmatic Hernia (CDH) ?
- Severe respiratory distress
- Cyanosis
- Dyspnea with scaphoid abdomen
- Bowel sounds heard over effected area
Congenital Diaphragmatic Hernia (CDH) diagnosed with what ?
X-Ray
Treatment of a patient with a Congenital Diaphragmatic Hernia (CDH) ?
- Address the respiratory distress
- Gastric decompression
- Infant positioned with head and thorax higher than the ABD to facilitate downward displacement of the hernia contents.
- Correct acid/base, consider ECMO
- Ventilator management as with PPHN
Treatment of a patient with a Congenital Diaphragmatic Hernia (CDH) and a PaO2
- Stabilize
- ECMO
What are the 2 approaches in repairing CDH ?
- ) Repair on ECMO once pt has demonstrated to be able to wean off ECMO by idling 8 hrs at 10% flows with adequate PaO2s & PaCO2s.
- ) Wean the pt off ECMO and repair the pt within 24 - 48hrs after weaning from ECMO.
PPHN
Persistence of the fetal circulation after birth
HMD
Surfactant deficiency
MAS
Ball-valve obstruction in lung passages
Bronchopulmonary Dysplasia (BPD)
long term complication of oxygen and ventilator therapy
CDH
Abdominal organs invade the thorax through a hole in the diaphragm
True or False
Identification of clot formation in the arterial side of the ECMO circuit, diffuse fibrin deposition throughout the circuit or circuit age greater than 10 days may be justification for a complete circuit change out.
True
The mechanism of injury for MAS neonates includes
- Mechanical Obstruction
- Chemical Inflammation
True or False:
It would not be unusual for a neonate with meconium aspiration to require a chest tube to relieve pneumothorax
True
True or False:
Intrauterine asphyxia may stop the production of surfactant, leaving the neonate with a very stiff lung
False
