Anatomy and physiology | |
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Anatomy Muscle No consensus was achieved on continuity of diaphragm thickness in the zone of apposition The significance of echogenicity is unknown but should be investigated Changes in thickness ≥ 10% decrease from baseline thickness is regarded as cut-off for clinically relevant atrophy No consensus was achieved regarding cut-off for increased thickness due to confounding with inflammation and oedema Limitations for measurements Obesity and large tidal volume can complicate measurements Physiology Maximum effort measurements offer important information but are hard to obtain and compare due to subjectivity of a maximum effort Dysfunction Diaphragm excursion < 2 cm is indicative of dysfunction during quiet breathing No consensus was achieved on cut-off for dysfunction based on thickening fraction | |
Ventilator impact | |
Excursion Positive pressure ventilation augments amplitude with greater lung inflation PEEP lowers diaphragm resting position and reduces excursion Thickness Positive pressure ventilation reduces patient effort and as such thickness at end inspiration PEEP lowers the diaphragm resting position with higher thickness at end expiration due to shortening of the muscle Thickening Positive pressure ventilation reduces patient effort and as such diaphragmatic thickening PEEP lowers the diaphragm resting position with higher thickness at end expiration due to shortening of the muscle and as such its percentual thickening |