Neonatal rhinorrhea, heart rate variability, and childhood exercise-induced wheeze

Background: There is increasing evidence linking infant rhinorrhea to school-age exercise-induced wheeze (EIW) via a parasympathetic nervous system pathway. The ratio of the root mean square of successive differences in heart beats (RMSSD) measured in quiet sleep versus active sleep (RMSSDQS:AS) is a novel biomarker in asthma. Objective: We tested the hypotheses that (1) neonatal rhinorrhea predicts childhood EIW independent of other neonatal respiratory symptoms, (2) neonatal RMSSDQS:AS predicts childhood EIW, and (3) RMSSDQS:AS mediates the association between neonatal rhinorrhea and childhood EIW. Methods: Participants from the Safe Passage/Environmental Influences on Child Health Outcomes (PASS/ECHO) prospective birth cohort had heart rate variability extracted from electrocardiogram traces acquired in the first month of life. Parents reported on rhinorrhea in their child at age 1 month and on EIW in their child at ages 4 to 11 years. Results: In models (N = 831) adjusted for potential confounders and covariates, including neonatal wheeze, cough and fever, neonatal rhinorrhea–predicted childhood EIW (relative risk [RR] = 2.22; P = .040), specifically, among females (RR = 3.38; P = .018) but not males (RR = 1.39; P = .61). Among participants contributing data in both active and quiet sleep (n = 231), RMSSDQS:AS predicted EIW (RR = 2.36; P = .003) and mediated the effect estimate of neonatal rhinorrhea predicting EIW among females. Half of the females with a higher RMSSDQS:AS and neonatal rhinorrhea (n = 5 of 10) developed EIW as compared with 1.8% of the other females (n = 2 of 109) (P < .001). Conclusions: Our findings support dysregulation of the parasympathetic nervous system in infancy as one of the possible underlying mechanisms for the development of EIW later in childhood among females, which could aid in the development of future interventions

Osteoarthritis Classification Scales: Interobserver Reliability and Arthroscopic Correlation

The MARS Group* Background: Osteoarthritis of the knee is commonly diagnosed and monitored with radiography. However, the reliability of radiographic classification systems for osteoarthritis and the correlation of these classifications with the actual degree of confirmed degeneration of the articular cartilage of the tibiofemoral joint have not been adequately studied. Methods: As the Multicenter ACL (anterior cruciate ligament) Revision Study (MARS) Group, we conducted a multicenter, prospective longitudinal cohort study of patients undergoing revision surgery after anterior cruciate ligament reconstruction. We followed 632 patients who underwent radiographic evaluation of the knee (an anteroposterior weight-bearing radiograph, a posteroanterior weight-bearing radiograph made with the knee in 45°of flexion [Rosenberg radiograph], or both) and arthroscopic evaluation of the articular surfaces. Three blinded examiners independently graded radiographic findings according to six commonly used systems-the Kellgren-Lawrence, International Knee Documentation Committee, Fairbank, Brandt et al., Ahlbäck, and Jäger-Wirth classifications. Interobserver reliability was assessed with use of the intraclass correlation coefficient. The association between radiographic classification and arthroscopic findings of tibiofemoral chondral disease was assessed with use of the Spearman correlation coefficient. Results: Overall, 45°posteroanterior flexion weight-bearing radiographs had higher interobserver reliability (intraclass correlation coefficient = 0.63; 95% confidence interval, 0.61 to 0.65) compared with anteroposterior radiographs (intraclass continue

EMG Decomposition of Vastus Medialis and Vastus Lateralis in Normal Subjects and Patellofemoral Patients: A New Way of Assessing the Balance of Muscle Function?

INTRODUCTION: Much has been published on the electromyographic (EMG) differences between vastus medialis (VM) and vastus lateralis (VL); this work has mainly focused on the timing differences in the on¬set of muscle activation using surface EMG.1 However, little has been re¬ported on the frequency of the EMG signals, which can indicate differ¬ences in motor unit firing patterns. METHODS: This study used surface EMG signal decomposition technology to explore the properties of numerous simultaneously active motor units. EMG decomposition was conducted on VM and VL during a weight-bearing closed-kinetic-chain isometric “squat” task in pathology-free in-dividuals and case studies of patients with patellofemoral pain. EMG sig¬nals were collected with 2 five-pin surface array sensors, each providing 4 channels of data, which were placed over the belly of VM and VL. Each channel was then sampled at 20 KHz using a modified 16-channel Ba¬gnoli EMG system (Delsys Inc, Boston, MA). The signals were then de¬composed into the constituent action potentials. The mean firing rate for each motor unit action potential train, the number of peaks per second (PPS), was then calculated. RESULTS: The results from the normal subjects support previous findings of VM and VL EMG decomposition with approximately equal firing rates of VM and VL (FIGURE 1). However, the results in the patellofemoral pa¬tients show clear differences between the firing rates in VM and VL, with VM having significantly greater firing rates than any previously pub¬lished data from normal subjects2 (FIGURE 2). DISCUSSION: The ability to conduct surface EMG signal decomposition is a recent technological development. The elevated firing rate measured in the VM in this study could be explained in a number of ways. For ex¬ample, it could be an indicator of localized muscle fatigue in the VM or it could indicate a change in recruitment pattern of the motoneuron pool; either of these explanations could contribute to patellar maltracking. Al¬though exploratory at this time, these differences in motor unit recruit¬ment patterns between healthy subjects and patients with patellofemoral pain syndrome could represent an important future outcome measure of knee control when treating patellofemoral pain. Certainly this is an area worthy of further study. ACKNOWLEDGEMENTS: Delsys Inc for the loan of the EMG decomposition equipment