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Biomedical subjects

N Zamel

Publications and source records attributed to N Zamel.

At least 145 records · Page 8Linked to original sources
PubMed1980

Tonic inspiratory muscle activity as a cause of hyperinflation in histamine-induced asthma.

We studied the change in tonic activity of the inspiratory muscles during acute hyperinflation. Hyperinflation was provoked in two asthmatic and three normal subjects by progressively doubling doses of histamine. Changes in lung volume were determined with magnetometers and with a body plethysmograph. Intercostal muscle activity was recorded with surface electrodes and diaphragmatic activity with esophageal electrodes. Tonic activity was defined as electrical activity in the electromyogram present at end expiration. After histamine the maximal observed increase in plethysmographic thoracic gas volume in the five subjects was 29.8 +/- 6.4% of control (mean +/- SE). Hyperinflation was accompanied by a significant increase in tonic activity of the intercostal muscles (P < 0.01) and the diaphragm (P < 0.01). There was a significant correlation between the increase in thoracic gas volume and the increase in tonic intercostal (r = 0.82, P = 0.003) and diaphragmatic (r = 0.89, P = 0.003) activity. We conclude that histamine-induced hyperinflation is accompanied by persistent inspiratory muscle activity throughout expiration.

Adult↗
PubMed1980

The respiratory effects of regular cigarette smoking in women. A five-year prospective study.

Over a five-year period a consistent habit of smoking or nonsmoking was maintained by 302 women (aged 25 to 54 years at the beginning of the study). There were 130 nonsmokers, 40 ex-smokers, and 15 light, 46 moderate, and 71 heavy smokers. Smokers without serious disability who had stopped smoking had a very low prevalence of respiratory symptoms and showed worsening of pulmonary function over the years similar to life-long non-smokers. Although there is a dose-related response to cigarettes, individual susceptibility also plays an important role in determining the respiratory effect of smoking. A range for change in ventilatory function over a five-year period in apparently healthy nonsmoking women is provided. Using this range, it is possible to identify susceptible smokers who show deterioration in ventilatory function that is more rapid than normal. Repeated spirometric studies may be useful in selecting a group at greatest risk of developing later disabling chronic obstructive pulmonary disease.

Adult↗
PubMed1979

Absence of effects of hypoxia on small airway function in humans.

We measured the effects of sustained isocapnic hypoxia (PAO2 = 40--50 Torr; PACO2 = 38--42 Torr) on tests sensitive to small airway function in healthy human subjects. Maximum expiratory flow-volume curves on air, nitrogen-hypoxic, helium-normoxic, and helium-hypoxic mixtures as well as closing volumes while subjects breathed air and a hypoxic mixture were obtained. We then measured total lung capacity (TLC), both plethysmographically and by inert gas dilution, and used the nonplethysmographic method to measure the effects of hypoxia on TLC. In none of these tests were there any statistically significant changes when values obtained during hypoxia were compared with those during normoxia. It is suggested that previous reports that indicated that TLC was increased by hypoxia might have arisen from a plethysmographic artifact.

Adult↗
PubMed1979

Volume-displacement body plethysmograph using a large flowmeter without pressure compensation.

A modification of the conventional volume-displacement whole-body plethysmograph was done using a low-resistance flow element and integrating the plethysmographic pressure signal. A flow element with a resistance of 0.036 cmH2O/(l/s), linear to 75 l/s was fitted to a 440-liter plethysmograph, resulting in an instrument with a volume-amplitude-frequency response flat to 15 Hz and in phase with mouth flow and esophageal catheter-balloon to at least 15 Hz without pressure compensation.

Humans↗
PubMed1979

Regulation of airway smooth muscle tone in sleeping dogs.

We examined the influence of sleep state on airway smooth muscle tone in 4 unanesthetized dogs that were trained to sleep in the laboratory. The dogs had been prepared with a permanent side-hole tracheostomy and bilateral cervical vagal loops. During the studies, the dogs breathed through a cuffed endotracheal tube inserted through the tracheostomy. To monitor changes in tracheal smooth muscle tone, we measured the pressure in the water-filled cuff of the endotracheal tube. The technique was validated by examining changes in cuff pressure after administration to the dogs of a series of chemical agents and physiologic stimuli known to constrict or relax tracheobronchial smooth muscle. Sleep state of the dogs was determined by behavioral, electroencephalographic, and electromyographic criteria. During quiet wakefulness, tracheal smooth muscle tone was stable. With the onset and progression of sleep through the nonrapid-eye movement stages, airway smooth muscle tone relaxed (decrease in cuff pressure of 20 to 40 cm H2O), reaching a new steady level during slow-wave sleep. In contrast, during rapid-eye-movement sleep, tracheal smooth muscle tone fluctuated markedly and erratically, as reflected by changes in cuff pressure as large as 90 cm H2O. Partial blockade of the vagus nerves, by cooling the exteriorized cervical vagal loops, decreased or abolished the fluctuations in tracheal smooth muscle tone during rapid-eye-movement sleep at temperatures that did not abolish resting tone, demonstrating that the changes in tone during rapid-eye-movement sleep were related to variability in neural control of airway smooth muscle.

Animals↗
PubMed1979

Decrease in lung recoil pressure after cessation of smoking.

Tests of lung mechanics and single-breath carbon monoxide diffusing capacity (DLCO) were done in 26 apparently healthy cigarette smokers before and 2 months after cessation of smoking. There was a significant increase in vital capacity and 1-sec forced expiratory volume as well as improvement in frequency dependence of lung dynamic compliance. Slope and phase III and density dependence of maximal expiratory flow showed a borderline improvement DLCO did not change. Static lung pressure-volume curves showed a small but significant (P less than 0.01) shift toward lower pressures. We concluded that the previously reported decrease in lung recoil pressure observed in smokers is even more accentuated after cessation of smoking.

Adult↗
PubMed1979

Pulmonary function in identical twins: comparison of nonsmokers and smokers.

Forty-five apparently normal pairs of identical twins were given pulmonary function tests to determine the role of genetics in bronchial susceptibility to cigarette smoke. Maximal expiratory flow at 60 per cent of total lung capacity (Vmax60) was the best discriminator of smokers from nonsmokers among pairs in which one member smoked and the other did not. The intrapair difference of Vmax60 values in pairs in which both members smoked was the same as in pairs in which both members did not smoke. These data support the view that genetic factors are important in determining the vulnerability of the airways to cigarette smoke.

Adult↗
PubMed1979

Evaluation of the single-breath diffusing capacity in asthma and cystic fibrosis.

To explain why the single-breath carbon monoxide diffusing capacity (Dsb) was, on the average, elevated in 163 asthmatic subjects and 175 patients with cystic fibrosis, we simulated this elevation in ten normal subjects by having them perform the test for Dsb through an inspiratory obstruction. This resulted in an 18 percent increase in Dsb corrected for pulmonary volume. Inhalation of a bronchodilator drug was associated with relief of obstruction and a fall in the corrected Dsb in 31 asthmatic subjects but did not change either the obstruction or the corrected Dsb in 17 patients with cystic fibrosis. We suggest that elevated Dsb in asthma and cystic fibrosis is partly due to maximal inspiration against obstructed airways. This requires abnormally negative intrathoracic pressures, increasing the pulmonary capillary blood volume, and, thereby, increasing the Dsb.

Adolescent↗
PubMed1978

Abnormalities in pulmonary function after brief exposure to toxic metal fumes.

A 26-year-old welder became ill after exposure to zinc and cadmium fumes at work. His initial clinical course was consistent with that of metal fume fever, but persistence of symptoms and signs beyond the usual duration in this condition led to suspicion of a toxic pulmonary reaction to cadmium. The finding of high percentages of both metals in the urine confirmed this diagnosis. Pulmonary function tests showed restriction of lung volumes, with increased elastic recoil and reduced diffusion, but no evidence of airways obstruction. Chest roentgenograms indicated central pulmonary edema, which cleared in 6 days. Follow-up assessment 2 years later showed incomplete improvement of the restrictive ventilatory defect.

Adult↗
PubMed1978

Effect of body position on carbon monoxide diffusing capacity in asymptomatic smokers and nonsmokers.

We measured carbon monoxide diffusion capacity (DLCO) in the sitting and supine position in 73 apparently normal subjects (41 nonsmokers and 32 smokers). The coefficient of DLCO standardized for alveolar volume (KCO) was less in the smokers than in the nonsmokers (P less than 0.05) in the sitting position, but the separation was wider in the supine posture (P less than 0.01). The per cent changes between supine and sitting KCO (deltaKCO) were shown to be age dependent in both nonsmokers and smokers, but this age dependence was more accentuated in the latter group. Only 3 smokers were below the 95 per cent confidence limit of nonsmokers for KCO in the sitting position, but there were 7 smokers below that limit for deltaKCO. An attempt was made, using intravenous injection of xenon-133, to study the mechanism of this impairment. Persons who failed to increase KCO in the supine posture showed an ability to increase apical blood flow in that position. The mechanisms of impairment in deltaKCO remain to be explained and may be due either to a predominant apical defect or to a widespread abnormality of the pulmonary capillary bed.

Adult↗
PubMed1978

Changes in pulmonary mechanics and gas exchange following thoracocentesis.

In nine patients with large pleural effusions, we studied the changes in pulmonary mechanics and gas exchange that occurred in the first three hours following removal of 600 to 1,800 ml of fluid by thoracocentesis. There was a small but significant increase in the functional residual capacity and total lung capacity but no change in residual volume and vital capacity. Calculated pulmonary shunt fraction did not change. We could not relate the subjective improvements noted by patients after thoracocentesis to the changes in pulmonary volumes or blood gas levels.

Adult↗
PubMed1977

Volume dependence of instantaneous time constants derived from the maximal expiratory flow-volume curve. A new approach to the analysis of forced expiration.

A simple expansion of the information in the maximal expiratory flow-volume curve was used to measure the convexity to the volume axis of maximal expiratory flow-volume curves produced by 11 asymptomatic smokers and 11 asymptomatic nonsmokers. The ratio of remaining volume to maximal flow was equal to the product of upstream resistance and chord compliance. This "instantaneous time constant" increased more near residual volume in the smokers. Using this method, plethysmographically obtained maximal expiratory flow-volume curves were more sensitive than spirometrically obtained maximal expiratory flow-volume curves. This method compared favorably with moment analysis and helium response of maximal expiratory flow as a separator of asymptomatic smokers and nonsmokers.

Adult↗
PubMed1976

Effect of ketosis on respiratory sensitivity to carbon dioxide in obesity.

We investigated whether the respiratory defect in the obesity-hypoventilation syndrome might respond to dietary manipulation. The effects of hypocaloric ketogenic regimens on the ventilatory response to carbon dioxide were studied in a manner excluding changes in weight or thoracic mechanics as factors. Six obese subjects with hyporesponse (less than 1.1 1/min/mm Hg) and 12 with normal response were fasted or given a diet containing 400 kcal per day of protein. During ketosis carbon dioxide response more than doubled in those with hyporesponse (0.8 +/- 0.1 to 1.8 +/- 1/min/mm Hg, P less than 0.05) but was unchanged in those with normal response. This improvement could not be accounted for by changes in weight, pulmonary function, pH or degree of ketosis between the two groups. However, a significant positive (r = 0.70; P less than 0.001) correlation between ketone-body concentrations and carbon dioxide response was observed in subjects with hyporesponse. These results indicate that depressed sensitivity to carbon dioxide in obese patients can be increased by dietary manipulation.

Acidosis↗
PubMed1976

Genetic influence on normal variability of maximum expiratory flow-volume curves.

To determine the importance of genetic influence on the variability of maximum expiratory flow-volume (MEFV) curves in normal individuals, MEFV curves breathing air and a mixture of 80% helium and 20% oxygen (He-O2), lung volumes, specific airway conductance, and closing capacity (CC) were obtained in 10 pairs of identical and 6 pairs of nonidentical twins, all nonsmokers and asymptomatic. For a given pair of identical twins, MEFV curves on air were more similar than those of a pair of nonidentical twins (P less than 0.02). The intrapair differences of identical twins were smaller than nonidentical twins of maximum expiratory flow (Vmax) at 60% of total lung capacity (TLC) on air (P less than 0.001) and on He-O2 (P less than 0.01). However, intrapair differences of Vmax at 40% TLC and CC were not significantly different in the two groups. Since Vmax at 60% TLC on air and He-O2 are dependent on the geometry of large airways these findings are suggestive that the geometry of large airways may be related to genetic factors. The relationship of the geometry of the peripheral airways and genetic factors has not been defined.

Adolescent↗