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Biomedical subjects

R Zinman

Publications and source records attributed to R Zinman.

34 records · Page 2Linked to original sources
PubMed1986

Maximal static pressures and lung volumes in a child with Guillain-Barré syndrome ventilated by a cuirass respirator.

Serial maximal static pressure and lung volume measurements were made in a child with Guillain-Barré syndrome and respiratory failure. The patient received successfully ventilatory support for seven weeks with the use of a cycled negative-pressure cuirass-type respirator obviating prolonged intubation and tracheostomy. The fall in VC preceded the loss of respiratory muscle strength (RMS) and lagged behind RMS in the return towards normal values. There was a disproportionate loss of lung volume (lowest VC, 220 to 250 ml, 11 to 12 percent of normal) as compared to maximal static pressures (lowest PImax, 60 cm H2O, lowest PEmax, 47 cm H2O). The disproportion was greater than that previously reported in adults. The greater loss in lung volume may be due to greater chest wall compliance in the child, resulting in less outward recoil of the chest wall and subsequently more microatelectasis with denervation of the chest wall musculature. Loss of lung volume resulted in a smaller surface area over which the respiratory muscles exerted their force. Thus, pressure being equal to force divided by surface area, could be relatively maintained and not reflect the extent of the loss of muscle force.

Child↗
PubMed1986

Effects of nutritional status on exercise performance in advanced cystic fibrosis.

Initial evaluation of 22 patients with cystic fibrosis (CF) on entry into a trial of home oxygen therapy was used to elucidate the possible effects of poor nutritional status on exercise performance in CF. The patients had advanced lung disease (mean FEV1, 36 percent predicted) and all had a stable resting PaO2 less than or equal to 65 mm Hg. Nutritional status was determined by calculating weight as a percentage of ideal for height (Wt/Ht) for each subject. Exercise testing consisted of a progressive exercise test on a cycle ergometer to measure maximum work capacity (Wmax), and a steady state test at 50 percent of baseline Wmax. During the steady state test, cardiac output (Q) and stroke volume (SV) were computed by the indirect Fick (CO2) method. Wmax, SV, Q and lung function results are expressed as percent predicted. Mean (+/- SD) Wmax was 58 +/- 15 percent predicted. Wmax correlated with both FEV1 and Wt/Ht, but FEV1 and Wt/Ht were not related. During steady state exercise, 12 of 22 patients had a SV less than 80 percent predicted. SV correlated with Wt/Ht, but not with lung function. Thirteen of the 22 patients had a Wt/Ht less than or equal to 90 percent and were considered malnourished. When compared with the well-nourished patients (Wt/Ht greater than 90%), these malnourished subjects had significantly lower mean values for Wmax%, SV% and Q% predicted, but not for lung function parameters. We conclude that: in patients with CF and advanced lung disease, nutritional status plays a significant role in determining exercise capacity; lower exercise tolerance of malnourished patients is an independent effect, as nutritional status and lung function were not related; and malnourished patients with CF have an altered cardiac performance on exercise testing which is due to a reduced SV rather than an impaired heart rate response.

Adolescent↗
PubMed1984

Abdominothoracic configuration and maximal static pressures in children.

The relationship of abdominothoracic configuration (AT config) to maximal static inspiratory and expiratory mouth pressure (Pimax, Pemax) was studied in 9 children. Pmax manoeuvres were performed from the relaxed end-expiratory position (FRC relax) and after contracting the abdomen (Abd) and expanding the rib cage (RC), (FRC isovol). Anteroposterior diameters (AP) of RC and Abd during Pmax were measured with magnetometers and compared to AT config at FRC relax. During both Pimax and Pemax from FRC relax the RC AP increased and Abd AP decreased. The pressures generated did not correlate with the change in either diameter. Moving to FRC isovol prior to the onset of pressure generation had no effect on AT config obtained for Pemax, but for Pimax resulted in further increase in RC AP and decrease in Abd AP as compared to FRC relax. Despite these differences in AT config, Pimax was not significantly affected. This suggests that changes in AT config expected to place the diaphragm at a mechanical advantage were countered by an opposite effect on the other inspiratory muscles. Because the AT config for Pemax was fixed, there appears to be a unique balance of forces between the expiratory muscles acting on the rib cage and the abdomen during a maximal static expiratory effort.

Abdomen↗
PubMed1984

Diphasic ventilatory response to hypoxia in newborn lambs.

The ventilatory response of newborn lambs to hypoxemia was evaluated in two groups of seven awake lambs studied at 2 and 7 days of life. Minute ventilation (VE) and airway occlusion pressure (P0.1) were monitored as the animals were exposed in sequence to room air, 12% O2 (15 min), 7% O2 (15 min), and room air. On 12 and 7% O2, 2-day-old lambs experienced a brisk hyperventilation followed by a VE depression, previously described in newborns of other species (diphasic response). The 7-day-old lambs had a clear diphasic VE response only on 7% O2 breathing. In the 2-day-old lambs, at the time of the relative VE depression to 12% O2, the respiratory centers showed a persisting responsiveness to further hypoxia; switching to 7% O2 caused a brisk increase in VE and P0.1 of 70 and 130%, respectively, which was followed again by a VE depression. The magnitude of the immediate VE response to hypoxia, taken as an index of the chemoreceptor strength, was inversely related to the magnitude of the VE depression (R = 0.81, P less than 0.001). It was concluded that 1) lambs as well as other neonates have an age-related diphasic VE response to hypoxia; 2) at the time of the VE depression, the respiratory centers maintain their responsiveness to further acute hypoxia; and 3) the weakness of the chemoreceptors in the newborn is a major determinant of the diphasic response.

Animals↗
PubMed1984

Cough versus chest physiotherapy. A comparison of the acute effects on pulmonary function in patients with cystic fibrosis.

Vigorous cough was compared with complete chest physiotherapy by functional evaluation in 9 patients with cystic fibrosis who had moderate airways obstruction. Pulmonary function tests were performed before and 1 h after treatment on consecutive mornings. The time spent coughing and in sputum production were equivalent for both treatments. There were no significant differences in functional response to either treatment. Static lung volumes and flows at high lung volumes were not affected. The increases in maximal expiratory flows at 50 and 25% of the vital capacity were 14 +/- 10 SEM% and 22 +/- 11 SEM%, respectively, after cough and 18 +/- 8% and 25 +/- 13% after chest physiotherapy. These responses did not correlate with the volume of sputum produced. Because there was no clear-cut benefit of chest physiotherapy over cough alone, and the latter is easier to perform, cough is an attractive alternate method of treatment.

Adolescent↗
PubMed1984

Importance of physician identification of airflow limitation in stable asthmatics.

The physician's ability to recognize airflow limitation was assessed in 92 stable asthmatics between seven and 12 years of age. A parental symptom score was obtained. The physician assigned a physical sign score and a clinical impression score based on the severity and lability of symptoms. Airflow limitation was considered significant if the forced expiratory flow between 25 and 75% of the vital capacity (FEF25-75) was less than 50% predicted. The FEF25-75 did not correlate with any of the scores and was less than 50% predicted in 27 of 92. There was no clinical suspicion of abnormality in 12 of 27. The FEF25-75 increased significantly after salbutamol inhalation in 22 of 23 but was persistently abnormal on follow-up in 9 of 21. We conclude that without pulmonary function tests the physician may fail to identify significant reversible airflow limitation in 13% of stable asthmatic children.

Adolescent↗
PubMed1983

Maximal static pressures in healthy children.

Maximal static pressures (Pmax) were measured at the mouth in 119 Caucasian school children aged 7-13 years. Lung volumes were determined by body plethysmography. Pressures were generated near RV, at FRC and near TLC. As in adults, inspiratory Pmax decreased with increasing lung volume, whereas expiratory Pmax increased. At all lung volumes expiratory and inspiratory Pmax increased with age and were greater in males than females. Net respiratory muscle force was derived from the product of pressure and surface area (SA) over which pressure was applied. SA was estimated at different lung volumes on the basis of chest wall measurements. The dimensions obtained were utilized to calculate the SA of a truncated cone. This model was shown to be appropriate at TLC and FRC, but not RV. Since both SA and Pmax increased with age, the derived forces, as compared with pressures, proportionally increased more with age. Thus changes in Pmax underestimated changes in force during growth.

Adolescent↗
PubMed1983

Effect of caffeine on control of breathing in infantile apnea.

Abnormalities in control of breathing have been associated with near-miss sudden infant death syndrome. Because caffeine is a respiratory stimulant, its effect on breathing pattern was evaluated in 12 infants with infantile apnea. Caffeine induced a significant increase in ventilation, tidal volume, and mean inspiratory flow. In contrast, no changes were noted in inspiratory time, expiratory time, or total cycle duration. These effects were observed with plasma concentrations of caffeine ranging from 8 to 20 mg/L. Caffeine increases ventilation mainly by increasing central inspiratory drive, and not be effective timing (T1/TTOT). This drug may be of value in near-miss SIDS.

Apnea↗
PubMed1981

Effects of airway occlusion at functional residual capacity in pentobarbital-anesthetized kittens.

The effects or airway occlusion at the end of inspiration on timing parameters and the "integrated" phrenic activity were studied in 1- to 21-day-old kittens at two levels of pentobarbital anesthesia before and after bilateral vagotomy. In intact kittens during the first 2 wk of life, instead of the classical effects of airway occlusion at functional residual capacity (FRC), shortening of both inspiration and expiration, a decrease in amplitude and rate of rise of the integrated phrenic activity, or augmented breaths were recorded. These effects were not altered by an additional dose of pentobarbital sodium. In kittens of all ages, airway occlusion performed after bilateral vagotomy had no significant effects on either timing and phrenic activity. Therefore, vagally mediated reflexes are probably responsible for the paradoxical effects of airway occlusion at FRC. However, a possible contribution of the chest wall receptors cannot be excluded.

Airway Obstruction↗
PubMed1980

Caffeine effect on breathing pattern and vagal reflexes in newborn rabbits.

Ventilation, breathing pattern and vagal reflexes were studied in anaesthetized (pentobarbital) newborn rabbits aged 2-7 days before and after injection of 10 mg/kg of caffeine. With caffeine, tidal volume decreased and respiratory frequency increased but minute ventilation remained unchanged. Mean inspiratory flow increased only in the older rabbits. The breath-to-breath variability in tidal volume, mean inspiratory flow, inspiratory and expiratory times observed under control conditions was diminished in several animals following caffeine injection. Vagal pulmonary afferentation was not affected by caffeine. A facilitatory effect of caffeine on the central mechanisms controlling the breathing pattern was indicated by: (1) an enhanced Hering-Breuer expiratory-promoting reflex; (2) lack of effect on the Hering-Breuer deflation reflex; and (3) qualitatively similar effects of caffeine postvagotomy as prevagotomy.

Animals↗
PubMed1979

Maturation of caffeine elimination in infancy.

The developmental changes in caffeine elimination were studied in 7 infants aged between 2 1/2 weeks and 6 months. Adult plasma clearance rate of caffeine was achieved at 3 to 4 1/2 months of age. Plasma half-life and elimination rate reached adult levels after 3 to 4 1/2 months and seemed to exceed adult capacity thereafter. No significant changes in apparent volume of distribution were noted. Our data provide some indication of the age in infancy when the low rates of caffeine elimination in the neonate increase to the adult rate.

Adult↗
PubMedDate not supplied

Home oxygen delivery system for infants.

Home oxygen programs have evolved to facilitate the discharge of children who have bronchopulmonary dysplasia from neonatal intensive care units. This report describes a method of oxygen delivery for nighttime that is well suited to the home environment. It consists of an "inverted tent" that lines the walls and floor of the crib into which oxygen is flowed via an air entrainment device. This permits rapid equilibration of oxygen up to an FIO2 of 0.40 with a low flow oxygen source from a concentrator. The system is simple, safe, convenient, and economical.

Bronchopulmonary Dysplasia↗
PubMedDate not supplied

Maximal static pressures and lung volumes in young female swimmers: one year follow-up.

The relationship between the growth of lung volumes and the development of maximal static pressures was examined in a 1 year follow-up study of 17 female swimmers, initially less than 12 years of age. Lung volumes were measured by body plethysmography, and maximal static inspiratory and expiratory pressures were generated near residual volume, at functional residual capacity and near total lung capacity (TLC). The results were compared to the regressions obtained from cross-sectional data generated on 59 girls randomly selected from a local school. Height was similar in swimmers and controls. Vital capacity and total lung capacity increased during the year to exceed normal limits in 11 of 17 swimmers. The only significant increase of maximal static pressures during 1 year occurred in expiration near TLC in those swimmers initially less than 10 years of age, and all pressures fell within normal limits. We conclude that large lung volumes in swimmers cannot be accounted for by an increased ability to inflate and deflate the lung by the respiratory muscles.

Age Factors↗
PubMedDate not supplied

Pancreatic function testing in meconium disease in CF: two case reports.

We report two infants with cystic fibrosis (CF), presenting with meconium ileus and meconium plug, who had no clinical or biochemical evidence of pancreatic insufficiency during infancy. They underwent pancreatic secretory function testing at 11 and 9 months of age, respectively. Both patients had sufficient lipase and colipase secretion to maintain normal digestion of fat, confirming that meconium disease in CF does not necessarily imply pancreatic insufficiency and the need for enzyme supplementation in infancy. Nonetheless, we documented markedly reduced enzyme secretion in both patients, implying a potential role for the pancreas in the pathogenesis of meconium disease, even when clinical pancreatic insufficiency is absent. In addition, our patient with meconium ileus had a severely limited fluid secretory capacity (10.3% of mean normal values). In contrast, the patient with the milder presentation of meconium plug had a far greater ability to secrete fluid (75% of mean normal), but had poorer pancreatic proteolytic activity. We suggest that impaired fluid secretion may be a very significant factor in the pathogenesis of meconium ileus, and we speculate that an inability to maintain sufficient intraluminal fluid relative to the degree of pancreatic proteolytic deficiency may more adequately explain the risk of occurrence and the severity of intestinal obstruction in CF than either factor alone.

Age Factors↗