Ultrasound-guided assessment of diaphragmatic thickness as an indicator of successful extubation in mechanically ventilated cancer patients

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.Methodology: A prospective, longitudinal study conducted at Surgical ICU, National Cancer Institute, Cairo University, Cairo. Fifty patients were recruited during the immediate postoperative period after major elective cancer surgery who needed mechanical ventilation (MV). 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 to rapid shallow breathing index (RSBI) and ultrasound guided measurements of diaphragmatic thickness (tdi) during inspiration and expiration. The percent change in tdi between end-expiration and end-inspiration (Δtdi%) was calculated. The primary outcome measure was diagnostic accuracy of tdi and Δtdi% to predict weaning compared to ABG analysis (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 differed slightly in patients tested after 72 hours. Sensitivity of a cut off level of tdi of 2 mm was 84.6% and 83.3% after 48 and 72 hours of MV, respectively. Sensitivity of Δtdi% of 20% was clearly higher after 72 hours (95.8%). Using ROC curves, Δtdi% 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.Abbreviations: RSBI: Rapid shallow breathing index, MV: mechanical ventilation, tdi: diaphragm thickness, Δtdi%: percent change in tdi between end-expiration and end-inspiration, PPV: positive predictive value, NPV: negative predictive value, kappa: measure of agreement, NCI: National Cancer Institute, VIDD: ventilator-induced diaphragmatic dysfunctionCitation: Soliman AM, Samy MA, Heikal AM, El Ramely MA, Kotb TA. Ultrasoundguidedassessment of diaphragmatic thickness as an indicator of successful extubation. Anaesth pain & intensive care 2019;23(2):178-185