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Biomedical subjects

M H Lavietes

Publications and source records attributed to M H Lavietes.

At least 19 recordsLinked to original sources
PubMed2001

The perception of dyspnea in patients with mild asthma.

BACKGROUND: Airway function, as assessed by standard spirometry, and the intensity of dyspnea reported by asthmatic patients correlate poorly. OBJECTIVE: This study tests the following two hypotheses: (1) that measures of the tendency of a patient to somatize will reduce the variation in the report of dyspnea not explained by airway function; and (2) that plethysmography is a better tool with which to estimate the degree of dyspnea associated with asthma. DESIGN: A prospective laboratory study carried out over one study session. PARTICIPANTS: Forty asthmatic subjects who had withheld bronchodilator (BD) therapy overnight. INTERVENTIONS: We performed spirometry, plethysmography, and an assessment of dyspnea (ie, modified Borg scale) on all subjects before and after they received BD therapy. Standard questionnaires pertaining to psychological state and trait were administered as well. RESULTS: The change in specific airway conductance with BD therapy correlated with a decline in the Borg score (r = 0.47; p = 0.007). By contrast, neither spirographic measures nor measures of static lung volumes correlated. Correlation with the Borg scale score was not improved by adding indexes of either somatization or psychological state or trait. CONCLUSION: The relief of dyspnea reported by patients with mild asthma after BD therapy is related to dilatation of the central airways.

Adult↗
PubMed2000

Psychological profile and ventilatory response to inspiratory resistive loading.

The purpose of this study was to explore the contribution of psychological state to both the ventilatory response and the intensity of dyspnea experienced after the addition of small inspiratory loads to breathing. We hypothesized that patients with either a specific psychiatric diagnosis or a specific psychological trait will associate a greater degree of dyspnea with a loaded breathing task than will control subjects. To insure the inclusion of persons with relevant psychological profiles, we recruited both subjects enrolled in the Chronic Fatigue Center and normal control subjects. In all, 52 subjects inspired first through a small (1.34 cm H(2)O/L/s) and second through a moderate (3.54 cm H(2)O/L/s) inspiratory resistive load (IRL). Ventilation was monitored throughout the 5-min sessions. Dyspnea was quantified with the Borg scale at specified times during the protocol. Standard psychological tests were administered. We found that subjects could be divided into two groups. One, the "responders," reported Borg scores higher than those of the second, or "nonresponder" group, at all times during the protocol. By contrast, there was no difference between groups with respect to ventilation. Responders had higher scores on tests of depression (the Center for Epidemiological Study depression scale) than did nonresponders. We conclude that the variability observed in subjective responses to IRL is explained, in part, by differences in psychological state.

Adult↗
PubMed1999

Changes in immune parameters seen in Gulf War veterans but not in civilians with chronic fatigue syndrome.

The purpose of this study was to evaluate immune function through the assessment of lymphocyte subpopulations (total T cells, major histocompatibility complex [MHC] I- and II-restricted T cells, B cells, NK cells, MHC II-restricted T-cell-derived naive and memory cells, and several MHC I-restricted T-cell activation markers) and the measurement of cytokine gene expression (interleukin 2 [IL-2], IL-4, IL-6, IL-10, IL-12, gamma interferon [IFN-gamma], and tumor necrosis factor alpha [TNF-alpha]) from peripheral blood lymphocytes. Subjects included two groups of patients meeting published case definitions for chronic fatigue syndrome (CFS)-a group of veterans who developed their illness following their return home from participating in the Gulf War and a group of nonveterans who developed the illness sporadically. Case control comparison groups were comprised of healthy Gulf War veterans and nonveterans, respectively. We found no significant difference for any of the immune variables in the nonveteran population. In contrast, veterans with CFS had significantly more total T cells and MHC II+ T cells and a significantly higher percentage of these lymphocyte subpopulations, as well as a significantly lower percentage of NK cells, than the respective controls. In addition, veterans with CFS had significantly higher levels of IL-2, IL-10, IFN-gamma, and TNF-alpha than the controls. These data do not support the hypothesis of immune dysfunction in the genesis of CFS for sporadic cases of CFS but do suggest that service in the Persian Gulf is associated with an altered immune status in veterans who returned with severe fatiguing illness.

Adult↗
PubMed1999

Reliability of maximal respiratory pressures in multiple sclerosis.

OBJECTIVE: To assess the reliability of maximal inspiratory pressure (P(I)max) and maximal expiratory pressure (P(E)max) in subjects with multiple sclerosis (MS) and healthy control subjects by identifying the number of testing sessions and the number of measurements needed in a single testing session to obtain consistent, reproducible results. DESIGN: A descriptive, comparative design with repeated measures was used. SETTING: Four sets of 10 P(I)max and 10 P(E)max measurements were obtained over a 4-week period from MS subjects in their homes. The same measurements were obtained from healthy control subjects in a private setting. SUBJECTS: Seventy-two MS patients and 61 healthy control subjects participated in the study. MEASUREMENT: P(I)max and P(E)max values were obtained by using previously published methods. RESULTS: Mean P(E)max and P(I)max values for MS patients differed over the first three of the four testing sessions. By contrast, mean P(E)max and P(I)max values for healthy control subjects differed only when the first session values were compared with values from the last three sessions. For MS patients, P(E)max and P(I)max increased between the first and 10th trial during the first testing session, but not during the subsequent three sessions. CONCLUSIONS: The results of this study suggest that several practice sessions should be provided in order to obtain reliable P(E)max and P(I)max values in persons with MS. At least one practice session should be provided for healthy control subjects before identifying a baseline.

Adult↗
PubMed1998

Airway dynamics, oesophageal pressure and cough.

This study hypothesizes that: peak supramaximal airflow during cough reflects expiratory muscle effort, and that expiratory muscle function during cough might be assessed from the airflow signal alone. We monitored airflow and oesophageal pressure (Poes) in normal subjects during cough generated under two conditions: 1) voluntarily from functional residual capacity (FRC); and 2) involuntarily after inhalation of citric acid (CA). Maximal expiratory cough flow was quantified as the quotient of maximal flow during a given cough divided by maximal flow at the matched volume of thoracic gas (Vtg) as identified on the maximal expiratory flow-volume curve. We found: flow ratios correlated poorly with Poes; the variance of flow ratios associated with a series of voluntary coughs was poorly explained by Poes. During CA inhalation, when the Vtg compressed during cough could not be controlled, correlation of Poes with flow ratio remained poor. We conclude that to study the motor limb of the cough reflex, measurements of both airflow and oesophageal pressure are required.

Administration, Inhalation↗
PubMed1997

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.

Abdominal Muscles↗
PubMed1996

Expiratory training in multiple sclerosis.

OBJECTIVE: To compare the effects of expiratory muscle training and sham training on respiratory muscle strength in patients with multiple sclerosis (MS). DESIGN: A randomized control trial; subjects were randomly assigned to either expiratory muscle training or sham training. SETTING: Training and measurement of respiratory muscle pressures were conducted in patients' homes. Weekly home visits were conducted to assure compliance with the training protocols and to obtain measurements. PATIENTS: Twenty subjects with clinically definite MS and decreased expiratory muscle strength entered the study; 10 subjects completed 3 months of expiratory training using a threshold training device and 5 subjects completed 3 months of sham training using the same device but without an expiratory training threshold load. MEASUREMENT: Respiratory muscle strength was assessed at baseline and after 1, 2, and 3 months of training; maximal inspiratory and expiratory pressures were used as measures of respiratory muscle strength. RESULTS: There was a significant increase in expiratory muscle strength after 3 months of training when the expiratory training group was compared to the sham group (p = .003); no significant change in inspiratory muscle strength was observed. CONCLUSIONS: The results of this pilot study suggest that the strength of the expiratory muscles of persons with MS can be increased through respiratory muscle training targeted to the expiratory muscles. Further research is indicated to determine if increasing the strength of the expiratory muscles in MS has an effect on clinical outcomes in this patient population.

Adolescent↗
PubMed1992

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.

Adult↗
PubMed1990

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.

Abdominal Muscles↗
PubMed1988

Rib cage and abdominal volume displacements during breathing in pregnancy.

To examine the effect of abdominal distension upon the actions of both rib cage and abdomen, we made serial determinations of tidal volume with a chest wall volume-displacement method in 8 pregnant women. Enhancement of tidal volume, long recognized in pregnancy, was achieved usually by augmentation of rib cage volume displacement. By contrast, abdominal volume displacement during quiet breathing is not altered in a predictable fashion by the gravid state. Given these findings, we hypothesize that the increased diaphragmatic contraction of pregnancy is accompanied by the transmission of that force to the lower rib cage via the area of apposition and that diaphragmatic contraction accounts for enhancement of the tidal breath. Diminished abdominal compliance might contribute to the augmentation of rib cage volume displacement as well. Konno-Mead diagrams suggest that this hypothesis is true in some, but not all, subjects.

Abdomen↗
PubMed1988

Inspiratory muscle strength in asthma.

Augmentation of inspiratory muscle strength (Pimax) represents an adaptive response to airway obstruction. We explore the possibility that respiratory muscle weakness may herald hospital admission during acute bronchospasm. The Pimax measured 81 +/- 25 percent of a predicted value in 20 patients with acute bronchospasm (forced expiratory volume in one second, 36 +/- 17 percent predicted). Pimax was related to both hyperinflation (functional residual capacity, as percent predicted) and body weight (subjects were 122 +/- 29 percent ideal body weight), but not to the degree of airway obstruction per se. Furthermore, measurements of axial (craniocaudal) motion of the rib cage and asynchrony of rib cage and abdominal motions during tidal breathing did not correlate with either the degree of air flow obstruction or Pimax. We conclude that little if any respiratory muscle weakness occurs with bronchospasm. Furthermore, Pimax does not correlate with the degree of airway obstruction and does not explain abnormalities of rib cage and abdominal motion associated with asthma.

Abdominal Muscles↗
PubMed1986

Energy requirements of the respiratory musculature in asthma.

Oxygen consumption and carbon dioxide production were measured in 29 asthmatic subjects. Minute ventilation was measured by a rib cage and abdomen-diaphragm displacement method. Expired gases were collected via a tight-fitting mask. Minute ventilation, oxygen consumption, and carbon dioxide production all increased when subjects inspired room air via a mouthpiece (when compared with a tight-fitting mask). By contrast, minute ventilation and carbon dioxide production both decreased when supplementary oxygen replaced room air via the tight-fitting mask (p less than 0.001). No consistent changes in either inspiratory work (estimated from measurement of pleural pressure during quiet breathing), airway resistance, or physiologic dead space could be seen to accompany changes in minute ventilation. It is concluded that the oxygen cost of breathing in asthma is substantial.

Airway Resistance↗