Comparison of Diaphragm Thickness Measurements Among Postures Via Ultrasound Imaging.

BACKGROUND: Assessment of diaphragm contraction may be useful for identifying impairments in patients with movement dysfunction involving trunk stabilization, respiration, or both. Real-time ultrasound imaging is a readily available technology that can be used to quickly assess this aspect of diaphragm activity. Although previous studies have examined diaphragm contraction in the supine posture, a comparison of measurements between supine and upright postures has not been made. OBJECTIVE: To examine whether diaphragm thickness measurements differ among 3 different body postures in healthy subjects. DESIGN: Descriptive repeated measures. SETTING: Clinical laboratory. PATIENTS (OR PARTICIPANTS): Twenty-four healthy subjects (12 male and 12 female) aged 22-35 years old were recruited and completed the study. METHOD: Diaphragm thickness was assessed in via B-mode ultrasound imaging in supine, seated, and standing postures. Measurements of diaphragm thickness were taken in the zone of apposition during maximal inspiration to total lung capacity (TLC) and end-tidal expiratory lung volume (EELV). A thickness ratio (inspiration thickness/expiration thickness) was calculated to compare relative diaphragm contraction during each condition. MAIN OUTCOME MEASUREMENTS: The primary dependent variable was diaphragm thickness (mm). RESULTS: Average diaphragm thickness at EELV and maximum TLC were more than 20% greater in the seated and standing postures than in supine (P < .05). Moreover, the diaphragm was approximately 205% thicker at TLC than at EELV (P < .05). Relative inspiratory to expiratory thickness ratios (TLC/EELV) did not differ among postures (P = .24). CONCLUSIONS: The diaphragm is thicker when the body is in more upright postures (standing and sitting versus supine) perhaps due to greater vertical gravitational load on the muscle and associated change in the resting length of the muscle fibers. Thus it appears that ultrasound imaging may be a sensitive tool to examine changes in diaphragm contraction during varying postural tasks. LEVEL OF EVIDENCE: IV.

Respiratory Muscle Activity During Simultaneous Stationary Cycling and Inspiratory Muscle Training.

Inspiratory muscle training (IMT) strengthens the muscles of respiration, improves breathing efficiency, and increases fitness. The IMT is generally performed independently of aerobic exercise; however, it is not clear whether there is added benefit of performing the IMT while simultaneously performing aerobic exercise in terms of activating and strengthening inspiratory muscles. The purpose of our study was to determine the effect of IMT on respiratory muscle electromyography (EMG) activity during stationary cycling in the upright and drops postures as compared with that when the IMT was performed alone. Diaphragm and sternocleidomastoid EMG activity was measured under different resting and cycling postures, with and without the use of the IMT at 40% maximal inspiratory pressure (n = 10; mean age 37). Cycling in an upright posture while simultaneously performing the IMT resulted in a significantly greater diaphragm EMG activity than while performing the IMT at rest in upright or drops postures (p ≤ 0.05). Cycling in drops postures while performing the IMT had a significantly greater diaphragm EMG activity than when performing the IMT at rest in either upright or drops postures (p ≤ 0.05). Sternocleidomastoid muscle activity increased with both cycling and IMT, although posture had little effect. These results support our hypothesis in that the IMT while cycling increases respiratory EMG activity to a significantly greater extent than when performing the IMT solely at rest, suggesting that the combination of IMT and cycling may provide an additive training effect.

Long-term effect of a short interprofessional education interaction between medical and physical therapy students.

Medicine is increasingly focused on team-based practice as interprofessional cooperation leads to better patient care. Thus, it is necessary to teach teamwork and collaboration with other health care professionals in undergraduate medical education to ensure that trainees entering the workforce are prepared to work in teams. Gross anatomy provides an opportunity to expose students to interprofessional education (IPE) early in their training. The purpose of this study is to describe an IPE experience and report if the experience has lasting influence on the participating students. The Readiness for Interprofessional Learning Scale (RIPLS) questionnaire was administered to first year medical (MD) and physical therapy (PT) students at Mayo Medical School and Mayo School of Health Sciences. Results demonstrated an openness on the part of the students to IPE. Interprofessional education experiences were incorporated into gross anatomy courses in both medical and PT curricula. The IPE experiences included a social event, peer-teaching, and collaborative clinical problem-solving sessions. These sessions enhanced gross anatomy education by reinforcing previous material and providing the opportunity to work on clinical cases from the perspective of two healthcare disciplines. After course completion, students again completed the RIPLS. Finally, one year after course completion, students were asked to provide feedback on their experience. The post-curricular RIPLS, similar to the pre-curricular RIPLS, illustrated openness to IPE from both MD and PT students. There were however, significant differences in MD and PT perceptions of roles and responsibilities. One-year follow-up indicated long-term retention of lessons learned during IPE.

Variability in diaphragm motion during normal breathing, assessed with B-mode ultrasound.

STUDY DESIGN: Clinical measurement, cross-sectional. OBJECTIVES: To establish a set of normal values for diaphragm thickening with tidal breathing in healthy subjects. BACKGROUND: Normal values for diaphragm contractility, as imaged sonographically, have not been described, despite the known role of the diaphragm in contributing to spinal stability. If the normal range of diaphragm contractility can be defined in a reliable manner, ultrasound has the potential to be used clinically and in research as a biofeedback tool to enhance diaphragm activation/contractility. METHODS: B-mode ultrasound was performed on 150 healthy subjects to visualize and measure hemi-diaphragm thickness on each side at resting inspiration and expiration. Primary outcome measures were hemi-diaphragm thickness and thickening ratio, stratified for age, gender, and body mass index. Interrater and intrarater reliability were also measured. RESULTS: Normal thickness of the diaphragm at rest ranged from 0.12 to 1.18 cm, with slightly greater thickness in men but no effect of age. Average ± SD change in thickness from resting expiration to resting inspiration was 20.0% ± 15.5% on the right and 23.5% ± 24.4% on the left; however, almost one third of healthy subjects had no to minimal diaphragm thickening with tidal breathing. CONCLUSION: There is wide variability in the degree of diaphragm contractility during quiet breathing. B-mode ultrasound appears to be a reliable means of determining the contractility of the diaphragm, an important muscle in spinal stability. Further studies are needed to validate this imaging modality as a clinical tool in the neuromuscular re-education of the diaphragm to improve spinal stability in both healthy subjects and in patients with low back pain.

Use of individual feedback during human gross anatomy course for enhancing professional behaviors in doctor of physical therapy students.

Medical professionals and public consumers expect that new physical therapy graduates possess cognitive, technical, and behavioral skills required to provide safe and high-quality care to patients. The purpose of this study was to determine if a repertoire of ten professional behaviors assessed at the beginning of doctorate of physical therapy education and before the first significant clinical internship could be enhanced in a semester course in gross human anatomy using individual formative feedback. During the human anatomy course, 28 first-year physical therapy students completed six biweekly, anonymous self- and peer assessment surveys that targeted ten professional behaviors important to physical therapists. All professional behaviors were assessed using a five-point Likert scale. Feedback reports occurred at week eight (mid-semester) and week 16 (end-of-semester) and comprised the direct intervention components of this study. At the midpoint of the semester, professional behavior scores and narrative comments from weeks two, four, and six were compiled and shared with each student by one of three faculty members in a feedback session. Students then submitted biweekly self-and peer professional behavior assessments (weeks 10, 12, and 14) for the remainder of the human anatomy course. Differences between preintervention and postintervention scores for each of the ten professional behaviors were compared using the Wilcoxon signed-ranks test. Upon receiving mid-semester individual feedback, students demonstrated significant improvement in each of the ten professional behaviors. Results from this study indicated a gross anatomy laboratory dissection experience during the first academic semester provided an effective opportunity for teaching and assessing professional behaviors of doctoral students in physical therapy.

Reduced ribosomal protein s6 phosphorylation after progressive resistance exercise in growing adolescent rats.

The purpose of this study was to investigate moderate intensity progressive resistance exercise (PRE) in growing adolescent rats and its effect on muscle hypertrophy (defined as an increase in fiber cross-sectional area [CSA]). We hypothesized that in adolescent animals moderate intensity PRE would increase (a) fiber CSA; (b) myosin heavy chain (MyHC) content; and (c) expression and phosphorylation of cell signaling molecules involved in translational regulation, compared with that in age-matched sedentary (SED) controls. In the PRE group, 3-week-old male rats were trained to climb a vertical ladder as a mode of PRE training such that by 10 weeks all animals in the PRE group had progressed to carry an additional 80% of their body weight per climb. In agreement with our hypotheses, we observed that 10 weeks of moderate PRE in adolescent animals was sufficient to increase the CSA of muscle fibers and increase MyHC content. The average muscle fiber CSA increased by >10%, and the total MyHC content increased by 35% (p < 0.05) in the PRE group compared with that in the SED animals. Concurrently, we investigated sustained changes in the expression and phosphorylation of key signaling molecules that are previously identified regulators of hypertrophy in adult animal models. Contrary to our hypotheses, expression and phosphorylation of the translational regulators mammalian target of rapamycin and Akt were not increased in the PRE group. In addition, we observed that the ratio of phosphorylated-to-unphosphorylated ribosomal protein S6 (rpS6) was reduced over sixfold in PRE animals (p < 0.05) and that total rpS6 protein levels were unchanged between PRE and SED animals (p > 0.05). We conclude that moderate intensity PRE is sufficient to induce muscle hypertrophy in adolescent animals, whereas the signaling mechanisms associated with muscle hypertrophy may differ between growing adolescents and adults.

A functional model of the digital extensor mechanism: demonstrating biomechanics with hair bands.

The action of muscles about joints can be explained through analysis of their spatial relationship. A functional model of these relationships can be valuable in learning and understanding the muscular action about a joint. A model can be particularly helpful when examining complex actions across multiple joints such as in the digital extensor mechanism of the hand. A functional model using two hair bands representing the components of the digital extensor mechanism is described. Through superimposition of the model over one's digit, the combined actions of metacarpophalangeal joint flexion and interphalangeal joint extension are clearly demonstrated. The model provides a conceptual demonstration to enhance understanding of this unique combination of muscle actions about multiple joints.

The effect of denervation on protein synthesis and degradation in adult rat diaphragm muscle.

Previous studies showed that unilateral denervation (DNV) of the rat diaphragm muscle (DIAm) results in loss of myosin heavy chain protein by 1 day after DNV. We hypothesize that DNV decreases net protein balance as a result of activation of the ubiquitin-proteasome pathway. In DIAm strips, protein synthesis was measured by incorporation of 3H-Tyr, and protein degradation was measured by Tyr release at 1, 3, 5, 7, and 14 days after DNV. Total protein ubiquitination, caspase-3 expression/activity, and actin fragmentation were analyzed by Western analysis. We found that, at 3 days after DNV, protein synthesis increased by 77% relative to sham controls. Protein synthesis remained elevated at 5 (85%), 7 (53%), and 14 days (123%) after DNV. At 5 days after DNV, protein degradation increased by 43% relative to sham controls and remained elevated at 7 (49%) and 14 days (74%) after DNV. Thus, by 5 days after DNV, net protein balance decreased by 43% compared with sham controls and was decreased compared with sham at 7 (49%) and 14 days (72%) after DNV. Protein ubiquitination increased at 5 days after DNV and remained elevated. DNV had no effect on caspase-3 activity or actin fragmentation, suggesting that the ubiquitin-proteasome pathway rather than caspase-3 activation is important in the DIAm response to DNV. Early loss of contractile proteins, such as myosin heavy chain, is likely the result of selective protein degradation rather than generalized protein breakdown. Future studies should evaluate this selective effect of DNV.

Interprofessional education in gross anatomy: experience with first-year medical and physical therapy students at Mayo Clinic.

Interprofessional education (IPE) in clinical practice is believed to improve outcomes in health care delivery. Integrating teaching and learning objectives through cross discipline student interaction in basic sciences has the potential to initiate interprofessional collaboration at the early stages of health care education. Student attitudes and effectiveness of IPE in the context of a combined gross anatomy course for first-year students in Doctor of Physical Therapy (DPT) and Doctor of Medicine (MD) degrees curricula were evaluated. Integrated teams of MD and DPT students participated in part of the gross anatomy dissection course at Mayo Medical School. A survey was administered to 42 MD and 28 DPT students that assessed their attitudes toward IPE and cooperation among health care professionals. Pre- and post-experience surveys were evaluated. Positive comments were related to opportunities for developing a better understanding of the nature and scope of each other's programs, encouraging teamwork and communication, mutual respect, and reducing the perceptual divide between disciplines. Ninety-two percent of the students agreed that interprofessional learning would help them in becoming a more effective member of the health care team. This initial experience with IPE in gross anatomy provides a basis for continued development of interdisciplinary educational strategies.

Retrospective analysis of the behavioral interview and other preadmission variables to predict licensure examination outcomes in physical therapy.

Evidence supporting the use of personal interviews in admissions decisions for health professions programs is conflicting. This retrospective study was intended to (1) quantify interrater reliability for assessing performance on a particular type of structured interview, the behavioral interview, and (2) examine the ability of multiple preadmission variables, including performance on the behavioral interview, to predict first-time performance on the national physical therapy licensing examination (NPTE). Data from 89 interviewees during the 2006-07 admissions cycle were used to examine inter-rater reliability. Data from 141 students who graduated from 2001 to 2005 were used to examine predictive validity of multiple preadmission variables on NPTE performance, including undergraduate cumulative grade point average (GPA), preprofessional science GPA, performance on the Graduate Record Examination (GRE) (including its analytical, quantitative, and verbal subscales), and performance on the behavioral interview. Inter-rater reliability for assessing interview performance was quantified with an intraclass correlation coefficient (ICC1,1). Receiver operating characteristic (ROC) curves and associated validity indices were used to analyze variables that distinguished graduates who did and did not pass the NPTE on their first attempt (alpha = 0.05). The ICC1,1 for assessing interview performance was 0.749. Performance on the verbal subscale of the GRE (ROC curve area = 0.734, p = 0.007) and behavioral interview (ROC curve area = 0.685, p = 0.034) were statistically significant predictors of NPTE performance. This study provides evidence supporting the contributions of the behavioral interview and verbal subscale of the GRE to predict NPTE performance and assist admissions decisions.

Neuregulin-dependent protein synthesis in C2C12 myotubes and rat diaphragm muscle.

The nerve-derived trophic factor neuregulin (NRG) is a prime candidate molecule for modulating muscle fiber growth. NRG regulates signal transduction in skeletal muscle through activation of ErbB receptors present at the neuromuscular junction. In this study, we hypothesize that NRG increases protein synthesis in maturing muscle via a phosphatidylinositol 3-kinase (PI3K)-dependent mechanism. NRG signal transduction and its ability to stimulate protein synthesis (measured by incorporation of [(3)H]phenylalanine into the protein pool) were investigated in differentiated C(2)C(12) myotubes and rat diaphragm muscle (DIAm). In C(2)C(12) myotubes, NRG dose dependently increased phosphorylation of ErbB3 and recruitment of the p85 subunit of PI3K. NRG also increased phosphorylation of Akt, a downstream effector of PI3K. NRG treatment increased total protein synthesis by 35% compared with untreated control myotubes. This NRG-induced increase in Akt phosphorylation and protein synthesis was completely blocked by wortmannin, an inhibitor of PI3K but was unaffected by PD-98059, an inhibitor of MEK. In DIAm obtained from 3-day-old rat pups, Akt phosphorylation increased approximately 30-fold with NRG treatment (vs. untreated DIAm). NRG treatment also significantly increased protein synthesis in the DIAm by 29% after 3 h of incubation with [(3)H]phenylalanine (vs. untreated DIAm). Pretreatment with wortmannin abolished the NRG-induced increase in protein synthesis, suggesting a critical role for PI3K in this response. The results of the present study support the hypothesis that nerve-derived NRG contributes to the regulation of skeletal muscle mass by increasing protein synthesis via activation of PI3K.