Lung Anatomy & Gas Exchange Airway anatomy Nose to pharynx to larynx to trachea to carina (bifurcation) to main bronchi to bronchioles to alveoli. - Right main bronchus is shorter, wider, more vertical to aspiration usually goes right. - Alveoli are surrounded by pulmonary capillaries; gas exchange is by diffusion across a very thin membrane.
Ventilation vs perfusion - V (ventilation) — air moving in and out of alveoli. - Q (perfusion) — blood flow through pulmonary capillaries. - V/Q mismatch = cause of most hypoxia. - Low V (pneumonia, atelectasis) to shunt. - Low Q (PE) to dead space.
ABG basics | Value | Normal | | pH | 7.35–7.45 | | PaCO₂ | 35–45 | | HCO₃⁻ | 22–26 | | PaO₂ | 80–100 | | SaO₂ | ≥ 95 % | ROME: Respiratory Opposite (pH & CO₂ move opposite) · Metabolic Equal (pH & HCO₃ move together).
Nursing red flags - SpO₂ < 90 % to apply O₂, reposition, notify. - Diminished breath sounds on one side after intubation to suspect right-mainstem intubation. - Late signs of hypoxia: cyanosis, bradycardia, hypotension.
Apply the lesson: original practice questions 1. Aspirated food most often lodges in which structure? A. Left main bronchus B. Right main bronchus C. Trachea D. Left lower bronchiole
2. ABG: pH 7.30, PaCO₂ 52, HCO₃⁻ 24. This represents: A. Respiratory acidosis, uncompensated B. Metabolic acidosis, uncompensated C. Respiratory alkalosis, uncompensated D. Metabolic alkalosis, compensated
3. Which are LATE signs of hypoxia? Select all that apply. A. Restlessness B. Cyanosis C. Bradycardia D. Hypotension E. Tachycardia
4. After endotracheal intubation, breath sounds are diminished on the left. The nurse's priority is to: A. Reposition the client to the left side. B. Notify the provider that the tube may be in the right mainstem. C. Suction the endotracheal tube. D. Administer albuterol.
5. Which SpO₂ value requires the nurse's immediate intervention? A. 98 % B. 95 % C. 92 % D. 88 %
Answers and rationales 1. B. The right main bronchus is shorter, wider, and more vertical, so aspiration typically follows gravity into the right side. 2. A. pH ↓ and CO₂ ↑ with normal HCO₃ = uncompensated respiratory acidosis (ROME — pH and CO₂ move opposite). 3. B, C, D. Early hypoxia: restless, tachycardic, tachypneic. Late: cyanosis, bradycardia, hypotension. 4. B. Right mainstem intubation is common; the tube must be pulled back and reconfirmed with x-ray. 5. D. SpO₂ < 90 % is hypoxemia. Apply O₂, reposition, and reassess. Source: original Nurseclex lesson, nurseclex.app/topics or nurseclex.app/nurseclex-guides.
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