Evolution of Diaphragm Thickness During Mechanical Ventilation: Impact of Inspiratory Effort (ATS Journals)

http://www.atsjournals.org/doi/abs/10.1164/rccm.201503-0620OC#.VaVrTmCcL1s http://www.atsjournals.org/doi/abs/10.1164/rccm.201503-0620OC#.VaVrTmCcL1s

Evolution of Diaphragm Thickness During Mechanical Ventilation: Impact of Inspiratory Effort

Ewan C Goligher, Eddy Fan, Margaret S Herridge, Alistair Murray, Stefannie Vorona, Debbie Brace, Nuttapol Rittayamai, Ashley Lanys, George Tomlinson, Jeffrey M. Singh, Steffen-Sebastian Bolz, Gordon D. Rubenfeld, Brian P Kavanagh, Laurent J Brochard, and Niall D Ferguson + <>Author Information. Corresponding Author: Niall D Ferguson, Email: niall.ferguson@uhn.ca Rationale Diaphragm atrophy and dysfunction have been reported in humans during mechanical ventilation, but the prevalence, causes, and functional impact of changes in diaphragm thickness during routine mechanical ventilation for critically ill patients are unknown. Objectives To describe the evolution of diaphragm thickness over time during mechanical ventilation, its impact on diaphragm function, and the influence of inspiratory effort on this phenomenon. Methods In 3 academic intensive care units, 107 patients were enrolled shortly after initiating ventilation along with 10 non-ventilated ICU patients (controls). Diaphragm thickness and contractile activity (quantified by the inspiratory thickening fraction) were measured daily by ultrasound. Measurements and Main Results Over the first week of ventilation, diaphragm thickness decreased by more than 10% in 47 (44%), was unchanged in 47 (44%), and increased by more than 10% in 13 (12%). Thickness did not vary over time following extubation or in non-ventilated patients. Low diaphragm contractile activity was associated with rapid decreases in diaphragm thickness while high contractile activity was associated with increases in diaphragm thickness (p=0.002). Contractile activity decreased with increasing ventilator driving pressure (p=0.01) and controlled ventilator modes (p=0.02). Maximal thickening fraction (a measure of diaphragm function) was lower in patients with decreased or increased diaphragm thickness (n=10) compared to patients with unchanged thickness (n=10, p=0.05 for comparison). Conclusions Changes in diaphragm thickness are common during mechanical ventilation and may be associated with diaphragmatic weakness. Titrating ventilatory support to maintain normal levels of inspiratory effort may prevent changes in diaphragm configuration associated with mechanical ventilation.

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