Quasielastic 3He(e,e'p)2H reaction at Q2 = 1.5 GeV2 for recoil momenta up to 1 GeV/c

We have studied the quasielastic 3He(e,e(')p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e(')p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.

Measurement of the 3He(e,e'p)pn reaction at high missing energies and momenta

Results of the Jefferson Lab Hall A quasielastic 3He(e,e'p)pn measurements are presented. These measurements were performed at fixed transferred momentum and energy, q=1502 MeV/c and omega=840 MeV, respectively, for missing momenta p(m) up to 1 GeV/c and missing energies in the continuum region, up to pion threshold; this kinematic coverage is much more extensive than that of any previous experiment. The cross section data are presented along with the effective momentum density distribution and compared to theoretical models.

Respiratory muscle length and strength in patients with chronic abdominal distension

Starling's law (the energy of muscle contraction is proportional to the initial fiber length) has been applied to contraction of inspiratory muscles. Its application to the expiratory muscles is difficult because both maximal length and maximal pressure development occur at total lung capacity (TLC). We hypothesize that decrease of both inspiratory (Pimax) and expiratory (Pemax) muscle strength in chronic ascites (CA) will reflect generalized muscle weakness and stretching of both the diaphragm and abdominal wall as well. To test this hypothesis, we evaluated Pimax and diaphragm length (at functional residual capacity) in 22 patients. Pemax, external oblique and transversus abdominus muscle lengths, and anterior abdominal wall muscle thickness were measured at TLC. We found Pimax (78 +/- 19% predicted), Pemax (61 +/- 17%), and--as an index of general muscle strength--handgrip strength (75 +/- 22%) all to be minimally reduced. Respiratory muscle strength did not correlate with any measurement of inspiratory/expiratory muscle length or thickness. With fluid removal, abdominal muscles shortened; diaphragmatic curvature decreased although diaphragm length was unchanged. Nevertheless, neither Pimax nor Pemax increased. Respiratory muscle strength depends upon generalized muscle strength more so than upon muscle length in CA patients.

Respiratory function in multiple sclerosis. Utility of clinical assessment of respiratory muscle function

PURPOSE

The aim of this study was to assess the utility of clinical assessment of respiratory muscle weakness in MS.

PATIENTS AND METHODS

We studied 40 MS patients who performed pulmonary function tests using standard procedures and measures of respiratory muscle strength. Descriptive clinical indices included a history of detailed neurologic findings, including upper and lower extremity weakness, cerebellar signs, and evidence of cerebral lesions and other clinical signs including dependence in activities of daily living, shortness of breath, weak voice, dysarthria and dysphagia. We devised an index comprised of four clinical signs: the patient's report of difficulty in clearing pulmonary secretions and his report of a weakened cough, the examiner's observation of the patient's cough, and ability to count on a single exhalation.

RESULTS

Mean values of TLC (95 percent +/- 14) VC (91 percent +/- 19), and RV (106 percent +/- 34) were normal. By contrast, MVV (68 percent +/- 20), PImax (74 percent +/- 27) and PEmax (51 percent +/- 22) were decreased. Stepwise multiple regression indicated that the best single predictor of expiratory muscle weakness was the index score; the combination of index score, upper extremity weakness, and maximal voluntary ventilation accounted for 60 percent of the variance in PEmax.

CONCLUSION

We conclude that clinical assessment is a better predictor of respiratory muscle weakness than spirometry and that a systematic clinical assessment supplemented by respiratory muscle assessment and MVV can uncover subtle respiratory muscle weakness in patients with MS.

The arterial wall response to intimal injury in an experimental model

Repair of occult arterial injuries is advocated to prevent thrombosis, arteriovenous fistula, and pseudoaneurysm formation. However, recent clinical series describe the healing of arterial intimal injuries and recommend nonoperative therapy. To investigate the arterial wall response to intimal injury, we created intimal flaps in 46 canine femoral arteries. The intimal flaps were imaged by arteriography, angioscopy, and intravascular ultrasound acutely, and at one and three weeks and five months post-injury. Lumen area was measured using caliper techniques (arteriography) and computerized video planimetry (angioscopy, intravascular ultrasound). Intimal and medial thickness were measured by intravascular ultrasound prior to harvest for histologic evaluation by light microscopy. Analysis of 32 patent arteries was performed after exclusion of 14 thrombosed arteries. Residual lumen area (mm2) correlated closely among the imaging modalities at one week (8.7 +/- 1.1, 7.3 +/- 2.0, 6.9 +/- 1.8), three weeks (4.2 +/- 0.9, 2.9 +/- 1.0, 2.7 +/- 0.8), and five months (5.3 +/- 0.9, 5.0 +/- 0.5, 5.0 +/- 0.9). Maximal intimal and medial thickness occurred three weeks post-injury, coincident with the maximal reduction in lumen area. Although intimal injuries can cause acute and delayed arterial thromboses, observation may be appropriate in selected cases. The evaluation of those patients chosen for nonoperative therapy should extend beyond three weeks, as this is the time of maximal arterial wall response with a continued potential for adverse clinical events.

A prospective evaluation of arterial intimal injuries in an experimental model

The management of arterial intimal defects remains controversial because of uncertainty concerning their natural history. We developed an experimental canine model to prospectively evaluate posterior wall intimal flaps in the superficial femoral artery. Arterial intimal flaps were constructed in 20 anesthetized dogs (40 arteries) and evaluated by arteriography, and angioscopy, and intravascular ultrasound. Postoperative patency rates at 1 (n = 20) and 3 weeks (n = 20) were compared with a control group of ten animals (n = 20, arteriotomy without intimal flap). Acute thromboses occurred in five experimental arteries with thromboses of eight additional experimental arteries at followup. Control patency was 100%, while experimental group patencies were 75% (p less than 0.05) at 1 week and 60% (p less than 0.009) at 3 weeks. All thrombosed arteries had intimal flaps with greater than 75% luminal stenosis. We conclude that intimal injuries cause arterial thromboses acutely and during subsequent followup. Intimal flaps with stenosis greater than 75% as determined arteriographically are at greatest risk for thrombosis. Angioscopy and intravascular ultrasound characterize arterial intimal defects and may delineate injuries requiring surgical or endovascular repair.

Ascites: its effect upon static inflation of the respiratory system

This report presents a simple clinical method to quantify the pressure generated within ascites fluid and thus to examine the effect of that fluid upon lung volume. The intra-abdominal hydrostatic pressure (Pih) given in cm H2O is the height of the meniscus of a column of water above the anterior abdominal wall measured with the patient supine. Pih thus may be thought of as a pressure in excess of the height of the anterior abdominal wall. In 23 study subjects, Pih measured 7.0 +/- 4.8 cm H2O; Pih correlated inversely with all static volumes. Furthermore, abdominal compliance (measured as the ratio of 100 ml ascites fluid removed divided by the difference between Pih before and after fluid removal) correlated directly with functional residual capacity. We conclude that the effect of ascites upon respiratory function varies among patients; the variation may be explained in part by Pih.