David Orlikowski

In cardiac surgery, patients are at risk of phrenic nerve injury, which leads to diaphragm dysfunction and acute respiratory failure. Diaphragm dysfunction (DD) is relatively frequent in cardiac surgery and particularly affects patients after coronary artery bypass graft. The onset of DD affects patients’ prognosis in term of weaning from mechanical ventilation and hospital length of stay. The authors present a narrative review about diaphragm physiology, techniques used to assess diaphragm function, and the clinical application of diaphragm ultrasound in patients undergoing cardiac surgery.

Respiratory muscle strength is a proven predictor of long-term outcome of neuromuscular disease (NMD), including amyotrophic lateral sclerosis, Duchenne muscular dystrophy, and spinal muscular atrophy. Maximal inspiratory pressure (MIP), a sensitive measure of respiratory muscle strength, one of several useful tests of respiratory muscle strength, is gaining interest as a therapeutic clinical trial endpoint for NMD. In this comprehensive review we investigate the use of MIP as a measure of respiratory muscle strength in clinical trials of therapeutics targeting respiratory muscle, examine the correlation of MIP with survival, quality of life, and other measures of pulmonary function, and outline the role of MIP as a clinically significantly meaningful outcome measure. Our analysis supports the utility of MIP for the early evaluation of respiratory muscle strength, especially of the diaphragm, in patients with NMD and as a surrogate endpoint in clinical trials of therapies for NMD.

Background: Bulbar weakness and respiratory impairment have been associated with increased morbidity in retrospective studies of Guillain‐Barré syndrome (GBS) patients. The aim of this study was to prospectively explore the relationship between subclinical swallowing impairment, respiratory function parameters, the necessity to intubate patients and the development of early postintubation pneumonia in patients with GBS in the intensive care unit (ICU).Methods: Respiratory, swallowing, and tongue strength parameters were measured in 30 consecutive adults (51.7 ± 18.1 years old), hospitalized for GBS in the ICU of a teaching hospital. Twenty healthy volunteers were recruited as a control group. The primary outcomes were intubation and pneumonia during the ICU stay.Results: Nineteen patients (65.5%) had piecemeal swallowing, and 19 (65.5%) had impaired breathing‐swallowing interaction, of which, respectively, 47.4% and 52.6% had a clinically apparent swallowing impairment. Swallowing impairment was associated with lower values of respiratory function, but not with peripheral motor weakness. Tongue protrusion strength was correlated with respiratory parameters and swallowing impairment. Ten patients were intubated and six developed pneumonia. Age, BMI, severe axial involvement, respiratory parameters (vital capacity and respiratory muscle strength), tongue protrusion strength, and clinical swallowing impairment were predictors of intubation.Conclusions: Swallowing impairment was present early after ICU admission in over 80% of patients and was an important predictor of intubation. A systematic clinical evaluation of swallowing should be carried out, eventually combined with an evaluation of tongue protrusion strength, along with the usual assessment of neurological and respiratory function, to determine the severity of the GBS.