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Biomedical subjects

C Lisboa

Publications and source records attributed to C Lisboa.

At least 55 records · Page 3Linked to original sources
PubMed1985

Inspiratory muscle dysfunction and unexplained dyspnea in systemic lupus erythematosus.

The role of inspiratory muscle dysfunction in lung volume restriction and unexplained dyspnea was studied in 16 consecutive patients with systemic lupus erythematosus. Maximal mouth inspiratory pressure (PIM) and maximal transdiaphragmatic pressure (Pdi max) were measured. Pdi and its components were determined during quiet breathing. No significant association was found between the activity of the disease, several serologic markers, and the inspiratory muscle dysfunction. No specific anti-skeletal muscle antibody was found in these patients. Significant correlations were found between the degree of dyspnea and PIM (r = -0.69, P less than 0.01) and Pdi max (r = -0.75, P less than 0.001); however, dyspnea did not correlate with specific lung compliance. Vital capacity correlated significantly with the degree of dyspnea (r = -0.813, P less than 0.001) and with Pdi max (r = 0.544, P less than 0.05). No correlation was found between vital capacity and specific lung compliance. We conclude that inspiratory muscle dysfunction can be an important mechanism in the pathogenesis of the lung volume restriction and dyspnea in patients with systemic lupus erythematosus.

Adolescent↗
PubMed1985

Inspiratory muscle function in patients with severe kyphoscoliosis.

In 9 patients with severe kyphoscoliosis we studied inspiratory muscle function by measuring transdiaphragmatic pressure (Pdi) and its components: gastric (Pga) and esophageal (Pes) pressures during quiet breathing. Maximal Pdi and maximal inspiratory mouth pressure (Pimax) were also measured. The results showed that Pimax and Pdimax were significantly lower in patients than in normal subjects. During quiet breathing, all patients had positive swings in Pga, indicating an active contraction of the diaphragm, but Pes was significantly more negative, suggesting the recruitment of intercostal and accessory inspiratory muscles. We did not find significant correlations between Pimax, Pdimax, delta Pga/delta Pes, FVC, PaO2, or PaCO2 and the degree of spinal deformity. The FVC tended to correlate with Pimax (r = 0.63) and with Pdimax (r = 0.53). The Pdi correlated with PaO2 (r = 0.66) and with PaCO2 (r = -0.76; p less than 0.05). A significant correlation was also observed between Pimax and PaO2 (r = 0.785; p less than 0.05) and between Pimax and PaCO2 (r = -0.86; p less than 0.01). We conclude that impairment of inspiratory muscle function is related to the development of ventilatory failure in kyphoscoliosis.

Adult↗
PubMed1985

Acute effect of ketotifen on the dose-response curve of histamine and methacholine in asthma.

This study was designed to assess the acute effect of 1 mg of orally administered ketotifen on the dose-response curve to both histamine and methacholine, in 15 patients with bronchial asthma. From this curve we measured the concentration that produced a 20% fall in FEV1 (PC20) and reactivity, defined as the slope of the curve beyond the threshold dose. Results were analysed comparing the change in log PC20 and in reactivity before and after a double-blind administration of ketotifen and placebo. Ketotifen, compared to placebo, significantly increased the histamine PC20 (P less than 0.001) and reduced reactivity (P less than 0.001). After adjusting for starting FEV1 the difference of effect between ketotifen and placebo was still significant, although to a lesser degree (P less than 0.01). In contrast, ketotifen did not modify the methacholine dose-response curve. No significant changes were observed in FEV1 after ketotifen. The results suggest that acute administration of ketotifen has a selective action on histamine-activated pathways of bronchoconstriction.

Adolescent↗
PubMed1980

Relation between flow, curvilinearity, and density dependence of pulmonary pressure-flow curves.

In nine normal subjects we measured pulmonary pressure-flow curves by ensemble averaging over 20 breaths and solving the equation P = K'V alpha where P is flow-resistive pressure, K' is slope, 5 V is flow, and alpha is curvilinearity. The study was performed at four lung volumes from 37 to 73% of total lung capacity, with the subjects breathing air or HeO2. K' was lower at every lung volume during HeO2 breathing, whereas the exponent alpha was uninfluenced by either lung volume or HeO2 breathing. Although alpha increased with flow rate, comparison of air and HeO2 curves revealed that alpha was not uniquely related to Reynolds' number. Furthermore there was no correlation between curvilinearity and the density dependence of K'. These observations are inconsistent with the general equation P = KV alpha rho alpha-1 mu 2-alpha, where K is a constant related to airway geometry, rho is density and mu is viscosity. (Wood et al., J. Appl. Physiol. 41: 234-244, 1976). The reasons for this discrepancy are unclear, but do not appear to be related to effects of oscillatory flow because alpha was similar from 20 to 90 breaths/min in four subjects. We conclude that the curvilinearity of pulmonary pressure-flow curves is related to flow but independent of gas density and is not explicable solely on the basis of Reynolds' number.

Adult↗
PubMed1979

Pulmonary pressure-flow curves measured by a data-averaging circuit.

We measured pulmonary pressure-flow curves in nine normal nonsmoking subjects using a data-averaging circuit. With this method we obtained mean pressure flow curves of 20 consecutive breaths free of cardiac artifacts. Within-observer and within-subject-within-day reproducibility were good especially for the inspiratory limb of the curve. Within-subject-between-day variability in curvilinearity was substantial. In most subjects there was a continuous increase in resistance throughout the course of expiration even though the airways did not become dynamically compressed. This resulted in a mean value of expiratory resistance that was greater than during inspiration. Resistance early in expiration, however, was identical to that during inspiration. The data-averaging circuit allows for a more accurate assessment of the slope and the curvilinearity of pulmonary pressure-flow curves than other methods described before.

Airway Resistance↗