Rightward shift of optimal fascicle length with decreasing voluntary activity level in the soleus and lateral gastrocnemius muscles.

Much of our understanding of in vivo skeletal muscle properties is based on studies performed under maximal activation, which is problematic because muscles are rarely activated maximally during movements such as walking. Currently, force-length properties of the human triceps surae at submaximal voluntary muscle activity levels are not characterized. We therefore evaluated plantar flexor torque- and force-ankle angle, and torque- and force-fascicle length properties of the soleus and lateral gastrocnemius muscles during voluntary contractions at three activity levels: 100, 30 and 22% of maximal voluntary contraction. Soleus activity levels were controlled by participants via real-time electromyography feedback and contractions were performed at ankle angles ranging from 10 deg plantar flexion to 35 deg dorsiflexion. Using dynamometry and ultrasound imaging, torque-fascicle length curves of the soleus and lateral gastrocnemius muscles were constructed. The results indicate that small muscle activity reductions shift the torque- and force-angle, and torque- and force-fascicle length curves of these muscles to more dorsiflexed ankle angles and longer fascicle lengths (from 3 to 20% optimal fascicle length, depending on ankle angle). The shift in the torque- and force-fascicle length curves during submaximal voluntary contraction have potential implications for human locomotion (e.g. walking) as the operating range of fascicles shifts to the ascending limb, where muscle force capacity is reduced by at least 15%. These data demonstrate the need to match activity levels during construction of the torque- and force-fascicle length curves to activity levels achieved during movement to better characterize the lengths that muscles operate at relative to their optimum during a specific task.

Evaluation and comparison of parental needs, stressors, and coping strategies in a pediatric intensive care unit.

OBJECTIVE: To evaluate and compare the needs, stressors, and coping strategies of mothers and fathers in a pediatric intensive care unit, and to advance the development of the COMPASS questionnaire for examining parent experiences. DESIGN: Prospective cohort study using a modified version of a pilot questionnaire, incorporating a series of 58 questions based on a visual analog scale in three categories of needs, stressors, and coping strategies. SETTING: Tertiary pediatric intensive care unit, Southampton University Hospitals, Southampton, UK. SUBJECTS: A total of 182 parents (91 mothers and 91 fathers) of children admitted to the pediatric intensive care unit. INTERVENTIONS: Collection and analysis of needs, stressors, and coping strategies scores. MEASUREMENTS AND MAIN RESULTS: Both parents identified the need for honest, open, timely, and understandable information, with access to their child as paramount. Parents found feelings of uncertainty and helplessness to be particularly stressful. The main coping strategies employed by parents were related to trust, assurance, and believing in positive outcomes. The particular needs and stressors of mothers and fathers were found to be similar. There were, however, some statistically significant differences in stressors: mothers had higher stress scores regarding how their child looked, not being able to care for them, witnessing procedures, and on leaving their child as compared with fathers. There were no statistically significant differences in coping mechanisms between the sexes. CONCLUSIONS: Acute parental experiences can be documented using the COMPASS questionnaire. This study highlights the principal needs, stressors, and coping strategies of parents of children in the pediatric intensive care unit. The experiences of mothers and fathers are similar, but we identify some differences in stressors between the sexes.

Surfactant phospholipids, surfactant proteins, and inflammatory markers during acute lung injury in children.

OBJECTIVE: To explore the pathophysiology of acute lung injury in children. DESIGN: Prospective cohort study. SETTING: Regional University Hospital, pediatric intensive care unit. PATIENTS: Children without a preexisting lung injury who developed acute lung injury and were intubated were eligible for the study. Children without lung injury and intubated for minor surgical procedures acted as controls. INTERVENTIONS: Bronchoalveolar lavage fluid and blood were collected on days 1 to 4, weekly, and immediately before extubation during acute lung injury. Molecular species compositions of phosphatidylcholine were determined by electrospray ionization mass spectrometry of lipid extracts of bronchoalveolar lavage fluid supernatants. Surfactant proteins A, B, and D and interleukin-8 were measured in bronchoalveolar lavage fluid and plasma by enzyme-linked immunosorbent assay and Western blotting. MEASUREMENTS AND MAIN RESULTS: Eighteen children with acute lung injury were enrolled in the study and compared with eight controls. In children with acute lung injury, there were significant changes in the bronchoalveolar lavage fluid phosphatidylcholine species. Bronchoalveolar lavage fluid dipalmitoyl phosphatidylcholine (PC 16:0/16:0) and palmitoyl-myristoyl phosphatidylcholine (PC 16:0/14:0) significantly deceased during acute lung injury (p < .001 and p < .001, respectively), whereas oleoyl-linoleoyl PC (18:1/18:2), palmitoyl-linoleoyl PC (16:0/18:2) and stearoyl-linoleoyl PC (18:0/18:2) characteristic of plasma PC were significantly increased (p < .05, p < .02, and p < .05 respectively), as well as palmitoyl-oleoyl PC (16:0/18:1), and stearoyl-arachidonoyl PC (18:0/20:4) which are characteristic of cell membranes (p < .02, and p < .02, respectively). There were no significant changes to bronchoalveolar lavage fluid, surfactant protein A or B levels compared with controls during acute lung injury, whereas bronchoalveolar lavage fluid, surfactant protein D, and interleukin-8 levels significantly increased (p < .05 and p < .02, respectively). In plasma during acute lung injury, there were significant increases in surfactant proteins A, B, and D, and interleukin-8 (p < .001, p < .001, p < .05, and p < .001, respectively). CONCLUSION: Changes to the phosphatidylcholine profile, surfactant proteins, and inflammatory markers of bronchoalveolar lavage fluid and plasma in children with acute lung injury are consistent with an alveolar/blood leakage and inflammatory cell membrane degradation products. These changes are due to alveolar capillary membrane damage and cellular infiltration.