The contribution of each hemidiaphragm to the overall inspiratory strength in healthy subjects and unilateral diaphragmatic paralysis

Introduction: Total diaphragmatic strength is the result of the contribution of each hemidiaphragm. However, it is unclear if this is similar for both diaphragms or there is a disparity. Moreover, this compartmental behavior has not been investigated in patients with hemidiaphragm paralysis (HDP). Objectives: Evaluate the total diaphragmatic strength and its hemi compartments (right and left) during phrenic twitch stimulation (Tw) in controls and HDP patients. Methods: 9 patients with left diaphragm paralyis (LDP) (7male, 55.7±11.6 y) and 16 healthy volunteers (6 female, 46.9±5.5 y) underwent diaphragm muscle strength assessment by transdiaphragmatic pressure (Pdi)= Gastric Pressure (Pgas) - esophageal Pressure (Pes), through gastric and esophageal balloons during phrenic Tw bilaterally, then right and left. Results: The healthy volunteers present homogeneous Pdi distribution between Pes and Pgas. Unlike, HDP group does not generate Pgas enough to increase the Pdi not only on left side, but also in the diaphragm not paralyzed. CONCLUSION: In healthy people, both hemidiaphragms have similar contribution to the resulting strength. In patients with LDP, Pdi is reduced in both hemidiaphragms. This reflects the incapacity of preserved hemidiaphragm to generate adequate Pgas in face to a lifting mechanism of paralyzed hemidiaphragm.