What care and management strategies are used for a patient on a mechanical ventilator?

Management of Patients on Mechanical Ventilation

Patients on mechanical ventilation require lung-protective ventilation strategies with low tidal volumes (4-8 ml/kg predicted body weight), plateau pressures <30 cmH2O, appropriate PEEP (starting at 5 cmH2O), and continuous monitoring of oxygenation, ventilation, and patient-ventilator synchrony, combined with daily sedation protocols and spontaneous breathing trials to facilitate early liberation from the ventilator. 1

Initial Ventilator Settings

Tidal Volume and Pressure Targets

• Set tidal volumes at 4-8 ml/kg predicted body weight (PBW), calculated as: Males = 50 + 0.91[height (cm) - 152.4] kg; Females = 45.5 + 0.91[height (cm) - 152.4] kg 1
• Maintain plateau pressure <30 cmH2O to prevent ventilator-induced lung injury 2, 1
• For patients with ARDS, use the lower end of this range (6 ml/kg PBW) 2, 1
• Monitor driving pressure (plateau pressure minus PEEP) as it may better predict outcomes than tidal volume or plateau pressure alone 1

PEEP and Oxygenation

• Start with PEEP of 5 cmH2O; zero PEEP is not recommended 1
• For moderate-severe ARDS (PaO2/FiO2 <200 mmHg), consider higher PEEP strategy (>12 cmH2O) 1
• Set initial FiO2 to 0.4 after intubation, then titrate to the lowest concentration achieving SpO2 88-95% 1
• The main goal is to reduce harmful effects of mechanical ventilation while ensuring adequate gas exchange 2

Ventilation Parameters

• Titrate respiratory rate to maintain PaCO2 between 35-45 mmHg or PETCO2 35-40 mmHg 1
• Use standard inspiratory-to-expiratory (I:E) ratio of 1:2 for most patients 1
• Inspiratory time should be 30-40% of the total respiratory cycle 1

Continuous Monitoring Requirements

Essential Monitoring

• Pulse oximetry and capnography to ensure appropriate oxygenation and ventilation 3
• Plateau pressure, driving pressure, and transpulmonary pressure assessments to ensure adequate PEEP and minimize excess distending pressure 3
• Patient-ventilator synchrony to minimize work of breathing 1, 4
• Arterial blood gases 10-15 minutes after establishing initial settings, then correlate with capnographic end-tidal CO2 2
• Airway cuff pressures frequently adjusted to minimize airway injury and ventilator-associated pneumonia 3

Hemodynamic Monitoring

• Monitor heart rate, blood pressure, and urine output at frequent intervals until stable 2
• Positive-pressure ventilation can cause hypotension due to loss of sympathetic tone, atelectasis, and vagal stimulation 2
• 12-lead ECG may help establish the cause if cardiac arrest occurred 2

Sedation and Analgesia Management

Sedation Strategy

• Use analgesia-first sedation (analgosedation) rather than sedative-hypnotic-based sedation 2
• This approach is associated with longer ventilator-free time and shorter ICU length of stay 2
• Implement daily sedation interruption or protocols to maintain light sedation 2
• Daily spontaneous breathing trials (SBT) should be the central component of weaning protocols 2

Sedation Administration

• For ICU sedation with propofol, initiate at 5 mcg/kg/min (0.3 mg/kg/h), increasing by increments of 5-10 mcg/kg/min every 5 minutes until desired sedation achieved 5
• Most adult ICU patients require maintenance rates of 5-50 mcg/kg/min (0.3-3 mg/kg/h) 5
• Do not exceed 4 mg/kg/hour unless benefits outweigh risks due to risk of Propofol Infusion Syndrome 5
• Avoid abrupt discontinuation as this causes rapid awakening with anxiety, agitation, and resistance to mechanical ventilation 5

Analgesia

• Control pain with analgesics (fentanyl or morphine) and sedatives (lorazepam or midazolam) 2
• Adequate analgesia may reduce propofol requirements 5
• Short-acting, easily titratable analgesics facilitate frequent neurologic evaluations 2

Neuromuscular Blockade

• Consider neuromuscular blocking agents (vecuronium or pancuronium) with analgesia/sedation for patient-ventilator dyssynchrony or severely compromised pulmonary function 2
• For moderate-severe ARDS (PaO2/FiO2 <150), use deep sedation and muscle relaxation within first 48 hours of mechanical ventilation 2
• Caution: neuromuscular blockers mask seizures and impede neurologic examinations 2

Disease-Specific Adjustments

ARDS Management

• For moderate-severe ARDS (PaO2/FiO2 <150), apply prone positioning for >12 hours per day 2
• Consider higher PEEP levels 2
• Targets of oxygenation, PEEP, and adjuvant therapies should be individualized 2
• For severe refractory hypoxemia with lung injury score >3 or pH <7.2, consider ECMO in centers with expertise 2

Obstructive Airway Disease (Asthma/COPD)

• Use tidal volumes 6-8 ml/kg PBW with respiratory frequency 10-15 breaths/minute to allow adequate exhalation time 1
• Use shorter inspiratory time with I:E ratio 1:2 or 1:3 1
• Avoid hyperventilation as it causes auto-PEEP and hemodynamic compromise 2, 1
• If auto-PEEP develops, disconnect from ventilator to allow passive exhalation; assist exhalation by pressing on chest wall 2
• Continue inhaled albuterol through endotracheal tube 2

Cardiogenic Shock

• Balance intubation decision with potentially undesirable hemodynamic effects of transitioning from negative to positive-pressure ventilation 2
• Ensure adequate ventilatory settings, patient-ventilator synchrony, and patient comfort 2
• Acknowledge patient wishes regarding mechanical ventilation before initiation, especially in older patients 2

Weaning and Liberation

Daily Assessment

• Perform daily spontaneous breathing trial (SBT) as this consistently reduces duration of mechanical ventilation 2
• Use T-piece, CPAP, or low-level pressure support for SBT 2
• Screen for weanability through weaning predictor tests 4
• T-tube trials circumvent the impossibility of estimating patient work of breathing during pressure support 4

Extubation Strategy

• For high-risk patients, use non-invasive ventilation (NIV) after extubation to reduce ICU length of stay and mortality 2
• For patients at high risk of lung collapse (morbid obesity, post-cardiac surgery), consider direct extubation from CPAP ≥10 cmH2O 2
• Before extubation, patients must demonstrate ability to breathe successfully without pressure support and PEEP 4
• Avoid abrupt discontinuation; maintain minimal sedation throughout weaning 5

Critical Pitfalls to Avoid

Ventilator-Related Complications

• Avoid hyperventilation with hypocapnia as it causes cerebral vasoconstriction and worsens global brain ischemia 1
• Avoid excessive PEEP in hemodynamically unstable patients as it impedes venous return and exacerbates hypotension 1
• Recognize auto-PEEP early in obstructive disease to prevent breath stacking, barotrauma, and hypotension 2, 1
• Avoid high tidal volumes and plateau pressures to prevent ventilator-induced lung injury 2

Acute Deterioration

• Use DOPE mnemonic for acute deterioration: tube Displacement, tube Obstruction, Pneumothorax, Equipment failure 2
• In asthmatic patients, also consider auto-PEEP as a cause 2
• Monitor for signs of Propofol Infusion Syndrome: severe metabolic acidosis, hyperkalemia, rhabdomyolysis, hepatomegaly, renal failure, cardiac failure 5

Infection Control

• Use strict aseptic technique when handling propofol as contamination has been associated with fever, infection, sepsis, and death 5
• Never access propofol vials more than once or use on multiple persons to prevent transmission of bloodborne pathogens 5
• Monitor and adjust airway cuff pressures to minimize ventilator-associated pneumonia 3

Safety Considerations

• Mechanical ventilation should only be administered by persons trained in general anesthesia and airway management 5
• Facilities for maintaining patent airway, artificial ventilation, supplemental oxygen, and cardiovascular resuscitation must be immediately available 5
• Continuously monitor for hypotension, apnea, airway obstruction, and oxygen desaturation 5