Initiation and Modification of Respiratory Care
What to know cold
Initiation is about matching mode and settings to physiology and to a stated goal. Know volume control, pressure control, SIMV, PRVC, and APRV at a conceptual level, and know that lung-protective ventilation means 6 mL/kg predicted body weight, plateau 30 cmH2O or less, driving pressure 15 or less, and FiO2/PEEP titrated to a target saturation. Obstructive disease calls for lower respiratory rate, higher inspiratory flow, longer expiratory time, and tolerance of permissive hypercapnia. ARDS management includes PEEP tables, prone positioning for at least 16 hours daily in moderate-severe disease, and early ECMO referral when indicated. Know NIV and HFNC indications and contraindications, daily spontaneous breathing trials with low pressure support, extubation criteria, cuff-leak assessment, and post-extubation support. Reassess with an ABG and clinical exam roughly 20-30 minutes after any significant change.
Traps
- Tidal volume must be based on predicted, not actual, body weight.
- A high peak with a normal plateau is resistive; do not reflexively drop tidal volume.
- NIV is inappropriate with inability to protect the airway, facial trauma or surgery, severe agitation, or massive upper GI bleeding.
- Do not delay intubation when NIV is failing after a short trial.
- High auto-PEEP in asthma is worsened by high respiratory rate and short expiratory time.
Worked example
Predicted body weight, male: 50 + 2.3 x (height in inches - 60). For 70 inches: 73 kg. Lung-protective tidal volume at 6 mL/kg is about 440 mL; at 8 mL/kg it is about 584 mL. A reasonable start is VT 440 mL, rate 16, PEEP 5-8, FiO2 to keep SpO2 88-95%, then titrate on the ABG and mechanics.