ABSTRACT
BACKGROUND: Personalizing mechanical ventilation requires the development of reliable bedside monitoring techniques. The multiple-breaths nitrogen washin-washout (MBNW) technique is currently available to measure end-expiratory lung volume (EELVMBNW), but the precision of the technique may be poor, with percentage errors ranging from 28 to 57%. The primary aim of the study was to evaluate the reliability of a novel MBNW bedside system using fast mainstream sensors to assess EELV in an experimental acute respiratory distress syndrome (ARDS) model, using computed tomography (CT) as the gold standard. The secondary aims of the study were: (1) to evaluate trending ability of the novel system to assess EELV; (2) to evaluate the reliability of estimated alveolar recruitment induced by positive end-expiratory pressure (PEEP) changes computed from EELVMBNW, using CT as the gold standard. RESULTS: Seven pigs were studied in 6 experimental conditions: at baseline, after experimental ARDS and during a decremental PEEP trial at PEEP 16, 12, 6 and 2 cmH2O. EELV was computed at each PEEP step by both the MBNW technique (EELVMBNW) and CT (EELVCT). Repeatability was assessed by performing replicate measurements. Alveolar recruitment between two consecutive PEEP levels after lung injury was measured with CT (VrecCT), and computed from EELV measurements (VrecMBNW) as ΔEELV minus the product of ΔPEEP by static compliance. EELVMBNW and EELVCT were significantly correlated (R2 = 0.97). An acceptable non-constant bias between methods was identified, slightly decreasing toward more negative values as EELV increased. The conversion equation between EELVMBNW and EELVCT was: EELVMBNW = 0.92 × EELVCT + 36. The 95% prediction interval of the bias amounted to ± 86 mL and the percentage error between both methods amounted to 13.7%. The median least significant change between repeated measurements amounted to 8% [CI95%: 4-10%]. EELVMBNW adequately tracked EELVCT changes over time (concordance rate amounting to 100% [CI95%: 87%-100%] and angular bias amounting to - 2° ± 10°). VrecMBNW and VrecCT were significantly correlated (R2 = 0.92). A non-constant bias between methods was identified, slightly increasing toward more positive values as Vrec increased. CONCLUSIONS: We report a new bedside MBNW technique that reliably assesses EELV in an experimental ARDS model with high precision and excellent trending ability.
ABSTRACT
Indoor cycling (IC) has recently been increasing in popularity and gaining recognition as an effective training activity. However, few studies have investigated the benefits of IC for sedentary participants, and the electrical activity of muscles during IC classes, in fitness clubs, has not been reported. The aim of this study was to compare muscle activity, heart rate (HR), and subjective effort between two groups (sedentary participants and trained teachers of the fitness club), over three IC classes. Thirty-eight volunteers were split into two groups according to their fitness status and weekly training load. Each participant completed three IC classes in a private gym over separate days. Variables were compared both between groups and within classes. Exercise intensity, assessed using the HR, was similar in both groups. The subjective perceived effort, assessed using the Borg Scale, was significantly higher in the sedentary group. However, the surface electromyographic (sEMG) data showed adaptive responses in this group after three classes. There was a trend for a gradual reduction in fatigue in sedentary participants, especially for the gluteus maximus and biceps femoris muscles, raising doubts regarding the inclusion of individuals with different training levels in the same class. The root mean square and median frequency of the sEMG data changed over the three IC classes, indicating adaptation to fatigue in the sedentary group, but not in trained participants. Thus, IC can be incorporated into protocols for sedentary individuals, but the short-term adaptation suggests that developing a specific class/ protocol for beginners might be appropriate. They could then be included in an advanced class after the third day of training (AU)
Ciclismo indoor (CI) está ganando reconocimiento y popularidad en los últimos años y pocos estudios han investigado los beneficios para los participantes sedentarios. No se han publicado estudios sobre la actividad eléctrica de los músculos que participan en las clases reales de CI. El objetivo de este estudio fue comparar el tiempo y el efecto del grupo en las variables de la actividad eléctrica muscular, frecuencia cardíaca (FC) y el esfuerzo subjetivo en ambos grupos (profesores sedentarios y entrenados en un gimnasio). Treinta y ocho voluntarios fueron divididos en dos grupos de acuerdo a su estado de entrenamiento semanal. Cada sujeto completó en días separados, tres clases CI en un gimnasio privado. Las variables se compararon entre los grupos y entre las clases. La intensidad del ejercicio que llegaron los sujetos, en términos de FC, fue similar en ambos grupos, aunque el esfuerzo subjetivo, medido por la escala de Borg, mostró diferencias signicativas en la percepción del esfuerzo entre los grupos, siendo mayor en el grupo sedentario. Sin embargo, los datos muestran respuestas sEMG adaptativas en este grupo después de tres clases. Hubo una tendencia de reducción gradual de la fatiga en sedentarios, especialmente para GM y BF, y hace cuestionable la inclusión de las personas con diferente nivel de entrenamiento en el mismo salón de clases. Los resultados mostraron que tres clases de CI llevaron a cambios de comportamiento en el RMS y en la FM, lo que indica la adaptación a la fatiga en el grupo sedentario, pero no en los entrenados. Por lo tanto, IC puede ser incorporado en los protocolos para sedentarios, pero esta adaptación a corto plazo a la fatiga sugiere la posibilidad de posibilidad de nuevos estudios, con clase / protocolo especí_co para los principiantes. Ellos podrían ser incluidos en la clase avanzada a partir del tercer día de entrenamiento (AU)
