RCP 214 Study Guide Exam 1 Vocabulary Flashcards

Pediatric Airway Anatomy & Respiratory Mechanics

• Smallest Portion of a Child's Airway:

  • The narrowest anatomical region of the pediatric airway is the cricoid ring (cricoid cartilage).
  • Unlike the adult airway, where the glottis (vocal cords) represents the narrowest point, the pediatric airway is funnel-shaped, tapering down to the subglottic cricoid cartilage until approximately 8 to 10 years of age.

• Optimal Airway Positioning:

  • The best position to maintain an open, unobstructed airway in both children and adults is the "sniffing position."
  • Infants and Young Children: Requires a neutral neck position without hyperextension or hyperflexion, as overextending the head can cause airway collapse due to a highly compliant, flexible trachea. Placing a small shoulder roll under the upper torso helps maintain this neutral positioning.
  • Older Children and Adults: Requires slight cervical spine flexion with atlanto-occipital extension to align the oral, pharyngeal, and laryngeal axes.

• Interalveolar and Bronchiolar Connections:

  • Pores of Kohn: Microscopic openings in the alveolar septa that allow direct gas passage and collateral ventilation between adjacent alveoli.
  • Canals of Lambert: Tubular communications between terminal bronchioles and adjacent alveoli that provide collateral gas flow.
  • Channels of Martin: Direct interbronchiolar channels connecting adjacent respiratory bronchioles.

• Mechanisms of Reduced Pulmonary Reserve in Infants:

  • Fewer Alveoli: Infants are born with approximately $20 \times 10^6$ to $150 \times 10^6$ alveoli, compared to the adult count of $300 \times 10^6$ to $500 \times 10^6$.
  • High Metabolic Demand: Infants possess an oxygen consumption rate of $6\text{--}8\text{ mL }kg^{-1}\text{ min}^{-1}$, which is double the adult rate of $3\text{--}4\text{ mL }kg^{-1}\text{ min}^{-1}$.
  • Highly Compliant Chest Wall: Cartilaginous ribs afford little structural stability, causing chest wall collapsing during inspiratory efforts.
  • Reduced Functional Residual Capacity (FRC): Low baseline lung volume combined with rapid oxygen utilization leads to rapid desaturation during apnea.
  • Increased Airway Resistance: Airway resistance is inversely proportional to the fourth power of the radius ($R \times \frac{1}{r^4}$); smaller airway diameters substantially elevate work of breathing.
  • Diaphragmatic Muscle Composition: The infant diaphragm contains only about $25\text{--}30\text{\%}$ fatigue-resistant Type I (slow-twitch) muscle fibers, compared to $50\text{--}60\text{\%}$ in adults, predisposing infants to respiratory muscle fatigue.

Fetal Lung Development & Embryology

• Phases of Fetal Lung Development:

  • Embryonic Phase (Weeks 2 to 7):
  • Primary lung buds (right and left bronchial buds) arise from the ventral wall of the foregut endoderm at approximately Day 26 to 28.
  • Initial branching creates major lobar and segmental bronchi (approximately 4 generations of branching formed by weeks 6 to 7).
  • Development of the pulmonary artery and vein network begins.
  • Pseudoglandular Phase (Weeks 7 to 17):
  • Progressive branching of the bronchial tree occurs, forming terminal bronchioles (16 to 25 generations of branching).
  • Ciliated epithelial cells, goblet cells, and cartilage appear.
  • Canalicular Phase (Weeks 17 to 26):
  • Formation of respiratory bronchioles, alveolar ducts, and primitive terminal sacs.
  • Capillaries proliferate and juxtapose with the alveolar epithelium to form the air-blood barrier.
  • Type I and Type II pneumocytes begin differentiation; early surfactant synthesis begins.
  • Saccular Phase (Weeks 26 to 36):
  • Smooth-walled terminal sacs (saccules) form.
  • Mature surfactant production increases significantly; Phosphatidylglycerol (PG) first appears in measurable quantities around 35 to 36 weeks of gestation.
  • Alveolar Phase (Week 36 to Postnatal Age 8 Years):
  • True alveoli develop through septation of saccules, expanding total gas-exchange surface area.

• Early Cardiac Development:

  • By Week 4 of embryonic development (approximately Day 21 to 22), a single-chambered tubular heart begins rhythmic contractions and efficiently pumps blood throughout the embryo by Day 28.

Fetal Circulation & Neonatal Transition

• Path of Normal Fetal Blood Flow:

  • Oxygenated blood (SpO_2 \n\n approx 80\% \n) travels from the placenta via the single Umbilical Vein.
  • Approximately $50\%$ of blood bypasses the liver through the Ductus Venosus into the Inferior Vena Cava (IVC).
  • Mixed blood enters the Right Atrium; the majority is shunted through the Foramen Ovale into the Left Atrium.
  • Blood flows into the Left Ventricle and is pumped into the Ascending Aorta to supply the brain, heart, and upper extremities.
  • Deoxygenated blood returning from the head and upper body enters the Superior Vena Cava (SVC) \n\n rightarrow \n Right Atrium \n\n rightarrow \n Right Ventricle \n\n rightarrow \n Pulmonary Artery.
  • High Pulmonary Vascular Resistance (PVR) shunts approximately $90\%$ of pulmonary arterial blood across the Ductus Arteriosus directly into the Descending Aorta.
  • Deoxygenated blood returns to the placenta for reoxygenation through the two Umbilical Arteries.

• Circulatory Changes at Birth:

  • Umbilical Cord Clamping: Removes the low-resistance placental circuit, causing an immediate, significant rise in Systemic Vascular Resistance (SVR).
  • First Breath & Lung Expansion: Aeration of lungs and elevation of $PaO_2$ trigger marked pulmonary vasodilation, dropping PVR drastically and increasing pulmonary blood flow.
  • Foramen Ovale Closure: Increased pulmonary venous return increases Left Atrial pressure; as Left Atrial pressure exceeds Right Atrial pressure, the tissue flap of the Foramen Ovale functionally closes.
  • Ductus Arteriosus Closure: Elevation in blood $PaO_2$ along with a drop in circulating maternal prostaglandins ($PGE_2$) causes smooth muscle contraction in the Ductus Arteriosus wall, leading to functional closure within 10 to 15 hours and complete anatomical fibrosis within 2 to 3 weeks.
  • Ductus Venosus Closure: Cessation of umbilical venous blood flow leads to collapse and eventual ligamentous transformation (ligamentum venosum).

Perinatal Risk Assessment & Diagnostic Metrics

• Due Date Estimation:

  • Transvaginal or transabdominal ultrasound measuring Crown-Rump Length (CRL) during the first trimester (up to $13\frac{6}{7}$ weeks) is the most accurate method for establishing gestational age ($\pm 3\text{--}5$ days).

• Amniotic Fluid Surfactant Tests:

  • L/S Ratio (Lecithin/Sphingomyelin Ratio):
  • $L/S < 1.5$: High risk of Respiratory Distress Syndrome (RDS) ($73\text{--}90\%$ incidence).
  • $L/S = 1.5\text{--}1.9$: Intermediate risk ($50\%$ incidence).
  • L/S \n\n ge 2.0 \n: Indicates mature surfactant activity; minimal risk of RDS ($< 2\text{--}5\%$).
  • Phosphatidylglycerol (PG): Appears around 35 to 36 weeks gestation. Its presence confirms full lung maturity, particularly in pregnancies complicated by maternal diabetes where L/S ratio accuracy may be impaired.

• Apnea Categories & Clinical Interventions:

  • Primary Apnea:
  • Definition: Sudden breathing cessation following initial hypoxemia; accompanied by mild bradycardia, but blood pressure is maintained.
  • Intervention: Responds promptly to tactile stimulation (e.g., flicking the soles of feet, rubbing the back) and supplemental oxygen.
  • Secondary Apnea:
  • Definition: Follows uncorrected primary apnea; characteristically marked by complete absence of respiratory effort, profound bradycardia, hypotension, and generalized flaccidity.
  • Intervention: Unresponsive to tactile stimulation. Requires immediate Positive Pressure Ventilation (PPV) via bag-valve mask or T-piece resuscitator.

• FLACC Pain Scale:

  • Acronym for Face, Legs, Activity, Cry, Consolability.
  • A validated observational scoring tool used for non-verbal pediatric patients (aged 2 months to 7 years) where each of the 5 categories is scored from 0 to 2, yielding an aggregate score ranging from 0 to 10.

• APGAR Score:

  • Evaluated systematically at 1 minute and 5 minutes post-delivery (and every 5 minutes thereafter up to 20 minutes if the 5-minute score is lower than 7).
  • Appearance (Color): 0 = Pale/blue, 1 = Pink body/blue extremities (acrocyanosis), 2 = Completely pink.
  • Pulse (Heart Rate): 0 = Absent, 1 = $< 100\text{ beats min}^{-1}$, 2 = \n\n ge 100 ext{ beats min}^{-1} \n
  • Grimace (Reflex Irritability): 0 = No response, 1 = Grimace, 2 = Cry, sneeze, or cough.
  • Activity (Muscle Tone): 0 = Limp/flaccid, 1 = Some flexion, 2 = Active motion.
  • Respiration (Respiratory Effort): 0 = Absent, 1 = Slow/irregular/weak cry, 2 = Good, strong cry.
  • Interpretation: 7 to 10 = Normal transition; 4 to 6 = Moderately depressed; 0 to 3 = Severely depressed.

Resuscitation & Emergency Care (NRP Guidelines)

• Preterm Birth Statistics:

  • Approximately $50\%$ of all preterm births are spontaneous and unexplained.

• Steps in Resuscitation Team Efforts:

  1. Preparation: Review clinical risk factors, conduct team briefing, perform mandatory 4-question equipment check (Warm, Clear, Dry, Ventilate).
  2. Initial Rapid Assessment: Determine if the baby is term, has good muscle tone, and is breathing or crying.
  3. Initial Steps (completed within 30 seconds): Provide warmth under radiant warmer, position head in sniffing position, clear secretions if necessary (suction mouth then nose), dry thoroughly, and apply tactile stimulation.
  4. Assessment of HR and Breathing: Evaluate heart rate and spontaneous respirations.
  5. Initiation of PPV: If apneic, gasping, or heart rate is $< 100\text{ beats min}^{-1}$, begin Positive Pressure Ventilation (PPV) at a rate of 40 to 60 breaths per minute.
  6. Corrective Action (MR. SOPA): If heart rate does not improve or chest rise is inadequate, execute MR. SOPA:
  • Mask adjustment
  • Reposition head
  • Suction mouth and nose
  • Open mouth
  • Pressure increase (in increments of $5\text{ cmH}_2\text{O}$ up to max $40\text{ cmH}_2\text{O}$)
  • Alternative airway (Endotracheal tube or Laryngeal Mask Airway)
  1. Chest Compressions: If heart rate remains $< 60\text{ beats min}^{-1}$ despite 30 seconds of effective PPV through an alternative airway, start high-quality chest compressions synchronized with ventilation.
  2. Medications: Administer epinephrine if heart rate remains $< 60\text{ beats min}^{-1}$ despite effective ventilation and chest compressions.

• CPR Ratio in Neonatal Resuscitation Program (NRP):

  • Compression-to-ventilation ratio is 3:1 (3 compressions to 1 ventilation).
  • Target rate: 90 compressions and 30 ventilations per minute (totaling 120 events per minute).

• Epinephrine Administration Routes:

  • Intravenous (IV) or Intraosseous (IO): Preferred, most effective route; administered rapidly through an umbilical venous catheter (UVC).
  • Endotracheal (ET): Alternative temporary route while IV/IO access is established; requires a higher concentration/dose due to inconsistent lung absorption.

• Withholding and Discontinuing Resuscitation:

  • Withholding: Appropriate in cases of extreme prematurity (gestational age $< 22$ weeks, birth weight $< 400\text{ g}$) or lethal congenital anomalies (e.g., anencephaly, Trisomy 13 or 18).
  • Discontinuing: Indicated if heart rate remains absent ($0\text{ beats min}^{-1}$) after 20 minutes of continuous, high-quality resuscitative efforts following NRP protocols.

• Resuscitation Equipment Comparison:

  • Self-Inflating Bag:
  • Automatically refills without gas source.
  • Cannot deliver continuous positive airway pressure (CPAP) or blow-by oxygen without specialized external valves.
  • Requires a pressure-relief (pop-off) valve set at $35\text{--}40\text{ cmH}_2\text{O}$ to avoid barotrauma.
  • Requires an attached oxygen reservoir to deliver high $FiO_2$ ($90\text{--}100\%$).
  • Flow-Inflating Bag:
  • Requires a continuous gas flow source to inflate.
  • Capable of delivering free-flow blow-by oxygen and CPAP.
  • Allows dynamic hand-control over Peak Inspiratory Pressure (PIP) and Positive End-Expiratory Pressure (PEEP) using an adjustable flow-control valve.
  • Deflates completely if face mask seal is broken.

• Non-Viability Threshold:

  • A gestational age of $< 22$ weeks combined with a birth weight of $< 400\text{ g}$ indicates severe non-viability where survival is extraordinarily unlikely.

Neonatal Respiratory Pathophysiology & Complications

• Saccular Phase & Surfactant Maturation:

  • Functional, mature surfactant begins appearing consistently at 34 to 35 weeks of gestational age.

• Mechanism of Deadspace Ventilation in RDS:

  • Lack of surfactant increases surface tension, producing widespread micro-atelectasis and lung unit collapse.
  • Hypoxia and hypercapnia trigger severe pulmonary vasoconstriction, shunting blood flow away from non-ventilated alveoli.
  • Overdistension of remaining functional alveoli during positive pressure ventilation compresses capillary beds, preventing regional perfusion while ventilation continues, creating alveolar deadspace ($V/Q > 1$).

• Chest Wall Characteristics & RDS Susceptibility:

  • Neonates possess a hyper-compliant, cartilaginous rib cage that offers minimal opposing inward wall recoil.
  • When non-compliant, stiff lungs (due to RDS) demand high negative inspiratory pressures, the highly flexible chest wall collapses inward (sternal and intercostal retractions) rather than expanding the pulmonary parenchyma.
  • This decreases Functional Residual Capacity (FRC) below critical closing volume, triggering repetitive end-expiratory alveolar collapse.

• Post-Delivery Complications in Preterm Neonates:

  • Respiratory Distress Syndrome (RDS) secondary to surfactant deficiency.
  • Hypothermia due to high body surface area-to-mass ratio and absence of subcutaneous brown fat.
  • Intraventricular Hemorrhage (IVH) caused by fragility of the germinal matrix.
  • Necrotizing Enterocolitis (NEC) due to intestinal wall ischemia and bacterial colonization.
  • Retinopathy of Prematurity (ROP) triggered by exposure to fluctuating oxygen concentrations.
  • Patent Ductus Arteriosus (PDA) causing left-to-right shunting and pulmonary congestion.
  • Neonatal Sepsis related to immature cellular and humoral immunity.

• Indications for Nasal CPAP (nCPAP):

  • Signs of respiratory distress (tachypnea, grunting, intercostal retractions, nasal flaring).
  • Treatment of early RDS / surfactant insufficiency.
  • Prevention of post-extubation atelectasis and re-intubation failure.
  • Treatment of Apnea of Prematurity (AOP).
  • Dynamic upper airway instability (e.g., tracheomalacia).

• Pathophysiology of Cerebral Palsy:

  • Caused by systemic fluctuations in blood pressure, severe arterial hypotension, hypoxemia, or hyper/hypocapnia.
  • Impaired cerebral blood flow combined with immature cerebral autoregulation leads to ischemic damage of vulnerable periventricular white matter (Periventricular Leukomalacia - PVL) or Hypoxic-Ischemic Encephalopathy (HIE).

• Dangers of Excessive Supplemental Oxygen:

  • Retinopathy of Prematurity (ROP): Oxygen hyperoxia causes vaso-obliteration of developing retinal vessels followed by chaotic neovascularization, retinal detachment, and potential blindness.
  • Bronchopulmonary Dysplasia (BPD): Generation of Reactive Oxygen Species (ROS) damages alveolar and capillary structures, inducing lung inflammation and chronic tissue fibrotic alterations.
  • Cerebral Vasoconstriction: High arterial oxygen levels reduce cerebral perfusion, worsening central nervous system ischemic injury.

• Characteristics of the Germinal Matrix:

  • A temporary, highly vascularized subependymal structure located adjacent to the lateral ventricles in the developing fetal brain.
  • Contains thin-walled, fragile capillaries lacking basement membrane support, elastic fibers, or structural tissue.
  • Highly vulnerable to rupture when subjected to systemic arterial pressure surges, hypoxia, hypercapnia, or rapid volume expansions.
  • Major site of origin for Intraventricular Hemorrhage (IVH) in infants born prior to 32 weeks gestation or weighing $< 1500\text{ g}$.
  • Involutes and disappears naturally by 36 weeks of gestational age.

• Obstetric Strategies to Delay Premature Delivery:

  • Tocolytic Pharmacotherapy: Administration of medications such as Terbutaline (beta-2 adrenergic agonist), Indomethacin (NSAID/prostaglandin inhibitor), Nifedipine (calcium channel blocker), or Magnesium Sulfate to arrest uterine contractions.
  • Antenatal Corticosteroids: Intramuscular administration of Betamethasone or Dexamethasone to the mother between 24 and 34 weeks of gestation to accelerate fetal surfactant synthesis and reduce IVH incidence.
  • Cervical Cerclage: Surgical placement of a purse-string suture around an incompetent cervix to prevent premature opening.
  • Progesterone Supplementation: Weekly injections or vaginal administration of 17-alpha hydroxyprogesterone caproate to maintain uterine quiescence.
  • Treatment of Maternal Infections: Targeted antibiotic therapy to eradicate asymptomatic bacteriuria, bacterial vaginosis, or chorioamnionitis following Premature Rupture of Membranes (PROM).

Practice Research & Evidence-Based Medicine

• Evidence-Based Medicine (EBM):
  • Definition: The explicit, conscientious, and judicious integration of current best research evidence with clinical expertise and patient/family values to guide healthcare decisions.
  • Importance in Respiratory Care: Eliminates outdated or harmful empirical practices, standardizes clinical care protocols, optimizes resource utilization, reduces complication rates, and improves clinical outcomes across neonatal and pediatric populations.