How is diaphragmatic dysfunction managed in the Cardiovascular Intensive Care Unit (CVICU)?

Management of Diaphragmatic Dysfunction in the CVICU

Diaphragmatic dysfunction in the CVICU should be managed through a combination of proper assessment techniques and targeted interventions, with diaphragmatic ultrasound being the cornerstone of diagnosis and monitoring.

Diagnostic Assessment

• Diaphragmatic ultrasound is recommended as a useful and feasible bedside tool to assess diaphragmatic function, particularly in patients being weaned from mechanical ventilation 1, 2
• Estimation of diaphragmatic excursion should be considered a basic skill for intensivists to assess diaphragmatic function 1
• Transdiaphragmatic pressure measurement, which requires simultaneous recordings of esophageal and gastric pressures, can be used to assess the diaphragm's contribution to breathing 2
• A negative gastric pressure to transdiaphragmatic pressure ratio indicates severe diaphragmatic dysfunction or paralysis 2

Management Strategies

Ventilation Strategies

• Initiate non-invasive ventilation promptly in patients with diaphragmatic dysfunction showing signs of respiratory distress or hypercapnia 3
• Implement diaphragm-protective ventilation by maintaining proper levels of diaphragm contraction to prevent both disuse atrophy and excessive load-induced injury 4, 5
• Consider controlled ventilation modes when patient triggering is ineffective, but avoid prolonged controlled mechanical ventilation which can worsen diaphragmatic dysfunction 5, 6
• Target oxygen saturation of 88-92% in adults and avoid excessive oxygen administration which can worsen hypercapnia 3

Monitoring During Mechanical Ventilation

• Monitor diaphragmatic function regularly using ultrasound to detect atrophy in patients undergoing mechanical ventilation 7
• Use diaphragmatic thickening measurements as an accurate index of respiratory muscle workload during assisted mechanical ventilation 7
• Maintain synchronization between the patient and ventilator to prevent additional diaphragmatic injury 5

Weaning Considerations

• Before initiating weaning, ensure the precipitating cause of respiratory failure is treated and pH is normalized 3
• Use diaphragmatic ultrasound parameters to predict extubation success or failure:
  • Optimal cutoffs range from 10 to 14 mm for excursion 7
  • Thickening fraction of 30-36% suggests successful extubation 7
• Provide physiotherapy treatment before and after extubation to reduce weaning duration and risk of extubation failure 3
• Consider prophylactic non-invasive ventilation after extubation for patients at high risk of reintubation 3

Special Considerations for CVICU Patients

• Diaphragmatic dysfunction may be particularly relevant in CVICU patients due to:
  • Postoperative phrenic nerve injury 8
  • Hemodynamic instability affecting respiratory function 1
  • Potential for respiratory muscle fatigue during weaning 2
• In patients with severe hemodynamic compromise, carefully manage fluid balance as both hypovolemia and volume overload can adversely affect respiratory function, particularly in patients on ECMO 1
• For patients with single-organ respiratory failure due to diaphragmatic dysfunction, the prospects of recovery are generally good with appropriate support 3

Pitfalls and Caveats

• Incorrect placement of the gastric balloon in the lower esophagus can mimic severe diaphragmatic dysfunction when measuring transdiaphragmatic pressure 2
• Recruitment of abdominal muscles during expiration followed by sudden relaxation at inspiration can also mimic diaphragmatic dysfunction 2
• Diaphragmatic thickening fraction measurement is more technically challenging than excursion measurement and may not be considered a basic skill for all practitioners 1

By implementing these evidence-based strategies for diagnosing and managing diaphragmatic dysfunction in the CVICU, clinicians can improve patient outcomes and facilitate successful liberation from mechanical ventilation.