Ultrasonographic assessment of diaphragm function to predict need for mechanical ventilation and its liberation in patients with neuromuscular disorders: an observational, cohort, pilot study

Abstract

Objective: Evaluate diaphragmatic function using ultrasound to predict ventilatory need and weaning in neuromuscular patients. Design: Prospective, observational, pilot study. Setting: Neurology ward, high- dependency and intensive care unit. Patients: Adult neuromuscular patients needing inpatient treatment Interventions: Ultrasonographic assessment of diaphragmatic excursion (DE) and diaphragmatic thickness fraction (DTF) every 48 hours (ventilated patients) to 72 hours (non-ventilated patients) till weaned from ventilator or discharge. Measurements: Parameters measured: Primary- Need for mechanical ventilation. Secondary- Days on ventilator, number of ICU days Statistical assessment: Qualitative data- as % and quantitative data as mean +/- standard deviation. Continuous variables- compared using unpaired T tests and categorical variables with Chi-square tests. Contingency table analysis-for computing relative risks to compare baseline DE and DTF with serial changes. Main Results: DE reduced bilaterally over 48 hours of admission before needing mechanical ventilation. DTF failed to show any pattern of change. In non-ventilated patients, improvement in bilateral DE and DTF from first to third reading was observed. Mean values for serial DE readings, bilaterally, was significantly lower in ventilated patients compared to non-ventilated patients (p value – 0.05 & 0.01). Baseline left DE < 1cm showed 2.5 times relative risk for needing ventilation with a confidence interval of 0.62-0.99 (p value – 0.19). A decrease in right DE > 50% within 72 hours of admission had a relative risk of 3.3 for need of ventilation with a confidence interval of 1.29-8.59 (p value – 0.01). A positive change in bilateral serial DE readings implied higher ventilator free days. Conclusion: Serial DE measurements with a reducing trend in the first 2 days, a baseline left DE <1cm and a decrease in Rt DE of >50%are associated with need for mechanical ventilation in neuromuscular patients. This can help triage sicker patients earlier. Increased DE in ventilated patients is associated with increased ventilator free days and can predict early weaning.