What are the complications associated with mechanical ventilation?

Complications of Mechanical Ventilation

Mechanical ventilation causes direct lung injury through ventilator-associated lung injury (VALI), hemodynamic compromise from positive pressure effects, and infectious complications including ventilator-associated pneumonia, with mortality strongly linked to the development of these complications during ICU management. 1

Direct Pulmonary Complications

Ventilator-Associated Lung Injury (VALI)

The primary mechanism of ventilator-induced damage involves regional heterogeneity causing simultaneous overdistension in compliant areas and cyclic collapse/recruitment in diseased regions. 1

• Barotrauma occurs when plateau pressures exceed 30 cmH₂O, necessitating continuous pressure monitoring via waveform analysis 2
• Volutrauma results from excessive tidal volumes; protective ventilation requires 6-8 mL/kg predicted body weight in ARDS 2
• Atelectrauma develops from cyclic alveolar collapse and reopening, particularly in dependent lung regions with heterogeneous disease 1
• Regional lung heterogeneities in ARDS, COPD, and other conditions amplify these injury patterns through uneven pressure transmission 1

Pneumothorax and Air Leak Syndromes

• Pneumothorax represents a critical adverse event requiring immediate detection and intervention 1
• Risk increases with high airway pressures, pre-existing bullous disease, and aggressive ventilation strategies 3

Atelectasis and Derecruitment

• Alveolar derecruitment occurs during intubation transition from negative to positive pressure ventilation 1
• Post-suctioning derecruitment is a recognized complication requiring monitoring 1
• Gravity-dependent atelectasis develops in supine positioning, particularly in patients with obesity 1

Hemodynamic Complications

The transition from spontaneous negative-pressure to positive-pressure ventilation causes immediate hemodynamic instability through multiple mechanisms. 1

Intubation-Related Hypotension

• Loss of sympathetic tone with anesthetic induction precipitates acute blood pressure drops 1
• Deleterious vagal stimulation during laryngoscopy compounds hypotension 1
• Positive pressure reduces venous return and cardiac preload 1

Ongoing Hemodynamic Effects

• Increased intrathoracic pressure impedes venous return throughout mechanical ventilation 1
• Right ventricular afterload increases with elevated airway pressures 4
• Patients with cardiogenic shock are particularly vulnerable to hemodynamic deterioration 1

Infectious Complications

Ventilator-Associated Pneumonia (VAP)

VAP contributes independently to mortality and develops through multiple pathways including nosocomial sinusitis. 1

• Orotracheal intubation is preferred over nasotracheal to reduce sinusitis rates 1
• Nosocomial sinusitis serves as a reservoir for VAP development 1
• Endotracheal tube cuff pressure management is critical for prevention 5

Aspiration

• Aspiration injury may necessitate mechanical ventilation and complicates existing respiratory failure 1
• Inadequate airway protection from decreased consciousness increases aspiration risk 1

Airway Complications

Upper Airway Injury

• Endotracheal tube trauma causes mucosal injury and potential stenosis 5
• Cuff pressure monitoring prevents tracheal ischemia and injury 5
• Blood from the endotracheal tube signals significant airway trauma requiring investigation 3

Postextubation Stridor

• High-risk patients should undergo cuff leak testing before extubation 1
• Systemic steroids administered ≥4 hours pre-extubation reduce stridor in failed cuff leak tests 1

Patient-Ventilator Dyssynchrony

Dyssynchrony increases work of breathing, patient discomfort, and ventilator days through multiple mechanisms. 2

Auto-PEEP (Intrinsic PEEP)

• Creates inspiratory threshold load requiring patient effort to overcome before triggering 2
• Causes ineffective triggering, increased work of breathing, and potential hemodynamic compromise 2
• Management requires setting external PEEP at 80-85% of measured auto-PEEP without exceeding it 2

Flow Starvation

• Inadequate inspiratory flow (peak flow <80-100 L/min in adults) fails to meet patient demand 2
• Switching from constant to decelerating flow patterns reduces work of breathing 2

Trigger Asynchrony

• Suboptimal trigger sensitivity (-1 to -2 cmH₂O is optimal) increases triggering effort 2
• Waveform analysis identifies pressure deflections before breath delivery 2

Metabolic and Systemic Complications

Respiratory Acidosis/Alkalosis

• Inadequate ventilation causes CO₂ retention and respiratory acidosis 1, 5
• Excessive ventilation induces respiratory alkalosis 5
• Capnography monitoring ensures appropriate ventilation targets 5

Multiorgan Dysfunction

• Age strongly associates with mortality in mechanically ventilated patients 1
• Survival depends on both initial factors and development of complications during ICU management 1
• Renal failure requiring continuous renal replacement therapy carries higher mortality 1

Complications in Special Populations

Patients with Obesity and Diabetes

Obesity creates specific ventilatory failure risks through altered respiratory mechanics, reduced lung volumes in supine position, and impaired immune response. 1

• Body mass index determines lung volume and respiratory mechanics during mechanical ventilation 1
• Physical inactivity and insulin resistance further impair immune response 1
• Young patients with obesity and COVID-19 demonstrate particular vulnerability 1

Older Adults

• Mortality risk increases with age in mechanically ventilated patients 1
• Advance care planning regarding prolonged mechanical ventilation must be addressed before intubation 1
• Concomitant renal or hepatic dysfunction potentiates medication effects 1

Monitoring to Prevent Complications

Essential Monitoring Parameters

• Pulse oximetry and capnography ensure adequate oxygenation and ventilation 5
• Driving pressure and transpulmonary pressure assessments minimize excess distending pressure 5
• Pressure-volume loop analysis ensures adequate PEEP application 5
• Airway cuff pressure monitoring prevents airway injury and VAP 5

Waveform Analysis

• Flow waveforms reaching zero before next inspiration confirm adequate expiratory time 2
• Pressure waveforms ensure plateau pressures ≤30 cmH₂O to prevent barotrauma 2
• Successful interventions show decreased peak-to-plateau pressure gradient 2

Critical Pitfalls to Avoid

• Never apply external PEEP exceeding auto-PEEP levels—this causes additional hyperinflation and hemodynamic compromise 2
• Avoid prophylactic hyperventilation—no evidence supports benefit and may cause harm 1
• Recognize that global measures of oxygenation or respiratory mechanics may mislead by averaging opposite pathological phenomena in different lung regions 1
• Do not delay appropriate respiratory interventions while attempting noninvasive ventilation 1
• Minimize imposed work of breathing through largest possible endotracheal tube, circuit maintenance, and aggressive bronchodilator therapy 2