Abstract

Objective: The study aimed to assess diaphragmatic thickness measurement by B-mode ultrasound for prediction of extubation and proper timing of weaning from mechanical ventilation in cancer patients admitted to the intensive care unit after major surgery.
Design: A prospective longitudinal study
Patients: Fifty patients were recruited during the immediate postoperative period after major elective cancer surgery who needed mechanical ventilation (MV).
Setting: Surgical ICU, National Cancer Institute, Cairo University
Intervention: Patients were enrolled when judged to be eligible for a test of weaning from MV according to clinical and arterial blood gases (ABG) criteria. The patient was assessed for weaning according rapid shallow breathing index (RSBI) and ultrasound measurements of diaphragmatic thickness (tdi) during inspiration and expiration. The percent change in tdi between end-expiration and end-inspiration (Δtdi%) was calculated.
Outcome measures: The primary outcome measure was diagnostic accuracy of tdi and Δtdi% to predict weaning compared to ABG (the gold standard for weaning).
Results: After 48 hours, 13 patients were weaned according to ABG criteria. Kappa value (agreement) between RSBI and ABG was 0.974. Kappa between both tdi and Δtdi% and the ABG criteria was 0.891. The values differ slightly in patients tested after 72 hours. Sensitivity of a cut off level of tdi 2 mm was 84.6% and 83.3% after 48 and 72 hours of MV, respectively. Sensitivity of ∆tdi% of 20% was clearly higher after 72 hours (95.8%). Using ROC curves, ∆tdi% of > 29.5% was also more sensitive after 72 hours.
Conclusion: Ultrasound estimation of diaphragm function is a promising tool to help clinicians to judge weaning readiness in patients on mechanical ventilation following major cancer surgery. Diaphragm thickness and its change between end-expiration and end-inspiration showed high degree of agreement with arterial blood gases for predicting weaning readiness.

Key words: Extubation; diaphragm dysfunction; diaphragm thickness; rapid shallow breathing index; mechanical ventilation