Foundations: Oxygenation & Perfusion – High-Yield Review

Oxygenation Concept

• Goal: supply cells with O_2 and remove CO_2 via lungs + circulation.
• Three inseparable processes:
  • Ventilation = movement of air in/out (inspiration = active, creates negative pressure; expiration = passive).
  • Respiration = alveolar gas exchange (O_2 ↔ CO_2 across alveoli–capillary membrane).
  • Perfusion = blood flow that transports gases to / from tissues.

Respiratory Anatomy & Function

• Upper airway: mouth, nose, pharynx, larynx.
• Lower airway: trachea → bronchi → bronchioles → alveoli ("tree trunk → branches → leaves").
• Alveoli: clustered sacs; stay open with deep breaths; collapse → ↓ gas exchange → atelectasis.

Factors Affecting Oxygenation

• Level of health: obesity, musculoskeletal weakness, MI, chronic illnesses.
• Age: ↓ tissue & lung elasticity with aging.
• Medications: opioids ↓ RR; bronchodilators ↑ airway diameter; beta-blockers may ↓ HR/contractility.
• Lifestyle: smoking/vaping, sedentary habits.
• Social determinants: occupational exposures (asbestos, dust, pesticides), air pollution, housing safety, language/health literacy, finance.
• Psychological: anxiety → tachypnea / hyperventilation.

Respiratory Assessment: Key Findings

• Rate & pattern: \text{bradypnea} (slow), \text{tachypnea} (fast), \text{apnea} (none), \text{dyspnea} (difficulty).
• Effort indicators:
  • Accessory-muscle use (neck, chest).
  • Nasal flaring, mouth breathing.
  • Retractions: intercostal or supraclavicular in inspiration.
  • Tripod/orthopneic positioning.
  • Grunting, audible wheeze.
• Breath sounds: clear, wheezes, crackles, diminished/absent.
• Color: central/peripheral cyanosis.
• SpO_2: know patient baseline; normal goal \ge 94\% (COPD often acceptable 88–92\%).
• Vital trends: ↑RR, ↑HR, ↑BP with distress; fever ↑ O_2 demand.

Common Oxygenation Disorders

• Pneumonia: alveoli fill with fluid.
• COPD (chronic obstructive pulmonary disease): chronic airway obstruction, barrel chest.
• Asthma: reactive airway narrowing; reversible with bronchodilator.

Nursing Interventions for Oxygenation

• FIRST: Position – elevate HOB, tripod as tolerated.
• Encourage deep-breathing, cough, incentive spirometry (10×/hr WA).
• Assess–intervene–reassess loop; document response.
• Consult Respiratory Therapy (RT) for treatments (e.g., nebulized albuterol).
• Manage anxiety; provide rest periods; cluster care.

Oxygen Therapy Essentials

• Oxygen = medication; needs order with target SpO_2.
• Delivery devices (fundamentals level):
  • Nasal cannula 1–6\;L\,min^{-1} (each L ↑ FiO_2 ≈ 4\%; 1\;L ≈ 24\% FiO_2; 6\;L ≈ 44\%).
  • Simple mask 6–10\;L\,min^{-1} (FiO_2 35–60\%); useful for mouth breathers or when NC ineffective.
• Humidify NC flows \ge 4\;L\,min^{-1} (attach sterile-water bottle).
• Check equipment: flowmeter, green "Christmas tree" adapter; verify port is oxygen (green) not medical air (yellow).

Oxygen Safety Reminders

• NO smoking/open flames near O_2.
• Store cylinders secured/upright; keep out of direct sunlight/heat.
• Use cotton bedding/clothing to reduce static.

Perfusion Concept

• Perfusion = movement of oxygenated blood through vessels to tissues.
• Requires intact pump (heart), pipes (vessels), and volume (blood).

Cardiovascular Anatomy & Physiology (Basics)

• Chambers: R atrium → R ventricle → lungs → L atrium → L ventricle → body.
• Valves: tricuspid, pulmonic, mitral, aortic.
• Electrical pathway: SA node → AV node → Bundle of His → Purkinje fibers (like relay race).
• Arteries: carry blood Away from heart, high pressure.
• Veins: carry blood toward heart, low pressure.
• Cardiac cycle:
  • Systole = ventricular contraction (S1 "lub").
  • Diastole = ventricular relaxation/filling (S2 "dub").
• Cardiac output (CO) = HR × Stroke Volume; normal \approx 4–8\;L\,min^{-1}.

Factors Affecting Perfusion

• Atherosclerosis: plaque narrows arteries (most common cause of ↓ flow).
• Age: valve stiffening, ↓ elasticity.
• Medications: beta-blockers ↓ HR/CO; vasodilators ↓ afterload; opioids ↓ BP/HR.
• Lifestyle & SDOH: diet, inactivity, smoking, air pollution, food deserts, health literacy.
• Psychologic stress/anxiety → tachycardia, ↑ BP.

Ischemia & Angina

• Ischemia = insufficient blood/O_2 supply to tissue (supply < demand).
• Angina = chest pain/discomfort resulting from myocardial ischemia.
• Progression: stable plaque → rupture → clot → complete occlusion → myocardial infarction (MI) or stroke.
• "Time is tissue" – rapid reperfusion critical.

Perfusion Assessment: Key Findings

• Subjective: chest pain (OLDCART), claudication, dizziness, fatigue, new SOB, sudden weight gain (fluid).
• Objective:
  • Skin: color, temperature, cap refill < 2\,s, edema.
  • Pulses: compare bilaterally, strength 0–3+; absent/weak may indicate obstruction.
  • Heart sounds: S1/S2 clarity; extra sounds or murmurs.
  • Vital signs: BP, HR rhythm/rate, SpO_2.
  • Neuro: LOC changes, facial droop, unilateral weakness (possible stroke).
• Diagnostics you may see ordered: ECG, labs (troponin, BNP, cholesterol), CXR, ultrasound, CT, stress test.

Nursing Interventions for Perfusion

• Reposition (semi-Fowlers) to ease work of heart & lungs.
• Frequent VS & focused assessments; compare to baseline.
• Administer O_2 for chest pain or SpO_2 < goal per order.
• Promote rest, limit exertion during acute episodes.
• Educate: smoking cessation, diet (low Na/low sat-fat), activity as tolerated, medication adherence.
• Collaborate: obtain 12-lead ECG, draw STAT labs, start IV access, prep for rapid interventions.

When to Notify the Provider / Rapid Response

• New or worsening chest pain unrelieved by rest/NTG.
• SpO_2 persistently < 90\% despite O_2.
• RR > 30\,min^{-1}, HR > 130\,min^{-1} or < 40\,min^{-1}.
• SBP < 90\,mmHg or > 180\,mmHg with symptoms.
• Acute mental status change, seizure, new unilateral weakness, slurred speech.
• Airway compromise, stridor, or absent breath sounds.

Quick Reference Values

• SpO_2 goal: \ge 94\% (unless COPD: 88–92\%).
• Normal RR: 12–20\,min^{-1}.
• Normal HR: 60–100\,min^{-1}.
• Normal BP: < 120/80\,mmHg.
• Nasal cannula: 1–6\,L\,min^{-1} → 24–44\% FiO_2 (add 4\% per L).
• Simple mask: 6–10\,L\,min^{-1} → 35–60\% FiO_2.
• Incentive spirometer: slow deep inhalation to set goal ×10 per hr.

Exam Tips

• Always start with least-invasive intervention (elevate HOB, encourage deep breaths) before escalating.
• Know early signs of hypoxia: restlessness, anxiety, tachycardia, tachypnea.
• Recognize accessory-muscle use & retractions as RED FLAGS.
• Understand that oxygen & perfusion concepts overlap; many factors/assessments/interventions apply to both.
• Practice reading flowmeters, setting NC flow, identifying correct wall outlet (green O_2 vs yellow air).