Structural, morphological and functional changes of diaphragm in patients with chronic heart failure

Background. Mechanical respiratory support is recommended for acute decompensation of chronic heart failure (CHF). Patients with CHF can develop morphological and functional changes of diaphragm not associated with respiratory support. Extrapolation of diaphragm-protective mechanical ventilation principles seems reasonable in these patients. Objective. To assess morphological and functional changes of diaphragm in patients with decompensated CHF. Material and methods. A two-stage study included 28 patients: stage 1 — clinical (10 patients), stage 2 (morphological) — 18 deceased patients. Stage 1 implied comparison of two groups: group 1 (improvement) — patients discharged from ICU (n=7), group 2 (deterioration) — extracorporeal membrane oxygenation (ECMO) as a bridge to heart transplantation (n=3). We performed ultrasound assessment of structural (thickness) and functional (thickening fraction and excursion) state of diaphragm under calm and deep inhalation/exhalation. External respiration was assessed using spirometry function of ventilator. Stage 2 is presented by comparative morphological assessment of muscular part of diaphragm in 11 patients who died from CHF and 7 patients who died from other reasons. Results. Diaphragm thickness (cm) decreased at discharge from ICU in group 1: on the right — calm inhalation 0.31 (0.3; 0.39)/0.22 (0.2; 0.27) (p=0.027), calm exhalation 0.26 (0.2; 0.36)/0.19 (0.1; 0.2) (p=0.04) (admission date/ discharge date). In group 2, diaphragm thickening (cm) was observed by the date of ECMO onset: on the right — calm inhalation 0.27±0.05/0.43±0.18, calm exhalation 0.21±0.03/0.25±0.03. There was deterioration of spirometry indicators: NIF (Mbar) — 30.0±15.2/13.3±3.0, deep inhalation volume (ml) 1696.6±603.6/1283.3±256.5 (admission/ECMO onset). In deceased patients, histological analysis revealed diaphragm thickening (2.5 (2.0; 3.1)/1.6 (1.4; 1.8) mm, p=0.006) due to edema (2.0 (1.5; 2.5)/0.9 (0.2; 1.5 points, p=0.011) and hypertrophy of muscle fibers (transverse diameter of muscle fiber 42.0 (37.6; 46.4)/34.9 (32.5; 35.9) µm, p=0.015) compared to patients died from other reasons. Conclusion. Intermuscular edema and hypertrophy of muscle fibers cause thickening and dysfunction of diaphragm in patients with CHF. This justifies extrapolation of diaphragm-protective respiratory support strategy to these patients. Ultrasound dynamic assessment of diaphragm state is useful in patients with decompensated CHF for analysis of therapeutic efficiency and prediction of outcomes.