Dyspnea and surface inspiratory electromyograms in mechanically ventilated patients

• Published in: Intensive care medicine 2013-08, Vol.39 (8), p.1368-1376
• Main Authors: Schmidt, Matthieu, Kindler, Félix, Gottfried, Stewart B., Raux, Mathieu, Hug, Francois, Similowski, Thomas, Demoule, Alexandre
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aged, 80 and over; Analysis; Anesthesiology; Artificial respiration; Biological markers; Care and treatment; Chronic obstructive pulmonary disease; Critical care; Critical Care Medicine; Diagnosis; Dyspnea; Dyspnea - physiopathology; Electromyography; Electromyography - methods; Emergency Medicine; Female; Humans; Inhalation; Intensive; Life Sciences; Male; Medicine; Medicine & Public Health; Methods; Middle Aged; Original; Pain Medicine; Patient outcomes; Pediatrics; Pneumology/Respiratory System; Prospective Studies; Respiration, Artificial - methods; Shortness of breath; Ventilators
• ISSN: 0342-4642; 1432-1238
• DOI: 10.1007/s00134-013-2910-3

Context Pressure support ventilation (PSV) must be tailored to the load capacity balance of the respiratory system. While "over assistance" generated hyperinflation and ineffective efforts, "under assistance" increased respiratory drive and causes dyspnea. Surface electromyograms (sEMGs) of extradiaphragmatic inspiratory muscles were responsive to respiratory loading/unloading. Objectives To determine if sEMGs of extradiaphragmatic inspiratory muscles vary with PSV settings and relate to the degree of discomfort and the intensity of dyspnea in acutely ill patients. Design Pathophysiological study, prospective inclusions of 12 intubated adult patients. Interventions Two PSV levels (high and low) and two expiratory trigger (ET) levels (high and low). Measurements Surface electromyograms of the scalene, parasternal, and Alae Nasi muscles (peak, EMG max ; area under the curve, EMG AUC ); dyspnea visual analogue scale (VAS); prevalence of ineffective triggering efforts. Main results For the three recorded muscles, EMG max and EMG AUC were significantly greater with low PS than high PS. The influence of ET was less important. A strong correlation was found between dyspnea and EMG max . A significant inverse correlation was found between the prevalence of ineffective efforts and both dyspnea-VAS and EMG min . Conclusions Surface electromyograms of extradiaphragmatic inspiratory muscles provides a simple, reliable and non-invasive indicator of respiratory muscle loading/unloading in mechanically ventilated patients. Because this EMG activity is strongly correlated to the intensity of dyspnea, it could be used as a surrogate of respiratory sensations in mechanically ventilated patients, and might, therefore, provide a monitoring tool in patients in whom detection and quantification of dyspnea is complex if not impossible.