Respiratory Care and Mechanical Ventilation
Matching support to need
Nasal cannula and high-flow nasal cannula suit mild-to-moderate distress; CPAP recruits lung in neonates, bronchiolitis, and post-extubation; intubation is indicated for apnea, exhaustion, ineffective ventilation, or failure of noninvasive support. In neonates use a T-piece resuscitator with an oxygen blender so FiO2, PIP, and PEEP are controlled and consistent during transport.
Ventilator fundamentals
Know pressure-limited versus volume-targeted modes and set tidal volumes near 4–6 mL/kg to limit volutrauma; PEEP preserves functional residual capacity. Uncuffed tube size = (age in years ÷ 4) + 4; cuffed = (age ÷ 4) + 3.5. Insertion depth at the lip in cm ≈ 3 × tube internal diameter. Confirm position with waveform capnography, bilateral breath sounds, and radiograph. For preterm infants, SpO2 targets around 90–95% reduce retinopathy risk while avoiding hypoxemia.
Blood gases
Read pH first, then PaCO2 and base excess. Low pH with high PaCO2 is respiratory acidosis - increase minute ventilation. Low pH with normal/low PaCO2 and negative base excess is metabolic - treat perfusion and the underlying cause.
Traps
Candidates lose points by forgetting to downsize when choosing a cuffed tube, by measuring depth at the teeth rather than the lip, and by hyperventilating patients with head injury or pulmonary hypertension. An unplanned extubation en route is managed with bag-mask ventilation first, not blind re-intubation attempts.
Rule of thumb
A 4-year-old takes a 5.0 uncuffed (4 ÷ 4 + 4) or 4.5 cuffed tube, inserted to roughly 15 cm.