Mechanical Ventilation

Lung-protective settings, alarms, and preventing VAP

Respiratory

Tidal volume 6–8 mL/kg of predicted (ideal) body weight, calculated from height. ~6 mL/kg in ARDS. Old fixed volumes like "500–800 mL" over-stretch the lungs.
Plateau pressure ≤30 cmH₂O.
PEEP keeps alveoli open; can ↓ BP (less venous return).
Lowest FiO₂ that meets the SpO₂ target.
Modes: assist-control (full support), SIMV, pressure support (weaning).

Confirm placement: waveform capnography (most reliable) + bilateral breath sounds and chest rise + chest X-ray.
Note the cm mark at the teeth or lips each shift.
Cuff pressure 20–30 cmH₂O.
Secure the tube; restraints only if needed and ordered.

Alarm	Common causes	Action
High pressure	Secretions, coughing, biting the tube, kinked tubing, water in tubing, bronchospasm, pneumothorax	Suction, bite block, straighten or drain tubing, assess breath sounds, notify
Low pressure / low volume	Disconnection (most common), cuff leak, tube displaced, circuit leak	Check connections from patient to vent; check cuff and tube position
Apnea	Patient not triggering breaths (over-sedation)	Assess; check mode and sedation

If you can't find and fix the cause right away: disconnect and ventilate with a bag-valve device on 100% O₂, and call for help.

HOB 30–45° unless contraindicated.
Daily sedation interruption + spontaneous breathing trial.
Oral care with toothbrushing. Updated Routine chlorhexidine mouthwash is no longer recommended (SHEA 2022).
Subglottic suction tubes for longer ventilation; drain tubing condensate away from the patient.
Early mobility; DVT and stress-ulcer prophylaxis as indicated.

VAP; barotrauma or pneumothorax (sudden high pressures, absent breath sounds, ↓ SpO₂).
Hypotension from positive pressure.
Stress ulcers, DVT, muscle weakness, pressure injury at lips.
Delirium: screen daily.

High Fowler's, oxygen, cough and deep breathe; watch for stridor (airway edema: report now); swallow assessment before eating.

Memory hook: sudden deterioration on the ventilator = DOPE Displaced tube · Obstructed tube (secretions, kink) · Pneumothorax · Equipment failure.