Biomedical subjects

S F Man

Publications and source records attributed to S F Man.

69 records · Page 4Linked to original sources

PubMed1983

Effects of high-frequency oscillatory ventilation on vagal and phrenic nerve activities.

This study was undertaken to define the mechanism for the respiratory inhibition observed during high-frequency oscillatory ventilation (HFOV). The effects of HFOV on the activities of single units in the vagus (Vna) and phrenic nerves (Pna) were examined in pentobarbital-anesthetized dogs. The animals were either ventilated by intermittent positive-pressure ventilation (IPPV) with and without positive end-expiratory pressure (PEEP), or by HFOV at a frequency of 25 Hz and pump displacement volume of 3 ml/kg. In 13 vagal units the Vna was much higher during HFOV than during IPPV or airway occlusion at a matched airway pressure. Ten units in the phrenic nerves were examined, and Pna (expressed as bursts/min) was attenuated by HFOV in all of them. In four of them, the effect of cooling the vagi to 8-10 degrees C on Pna was examined, and it was found that HFOV failed to alter the Pna. We conclude that 1) HFOV stimulates the pulmonary vagal afferent fibers continuously and to a degree greater than that due to static lung inflation and increased airway pressure and 2) the increased vagal activity during HFOV probably causes phrenic nerve activity inhibition.

Action Potentials↗

PubMed1983

Regional ionic and albumin content of fluid in the tracheobronchial tree in dogs.

We have devised a technique for collecting airway fluid from the bronchi in order to investigate the biochemical indices of airway fluid in normal dogs and the changes produced in them by pharmacological interventions. We collected airway fluid from the trachea by a screen technique and by means of filter paper cylinders inserted through a fiberoptic bronchoscope (the new method) and from main and segmental bronchi by the new method only. When bronchial fluid was compared with plasma, the concn of albumin was found to be much lower, Na+ lower, and Cl- either higher or similar. The Na+:Cl- ratio was lowest in fluid from the trachea (1.04) and highest in fluid from segmental bronchi (1.14), but was significantly lower at all levels than in plasma (1.32). Subcutaneous administration of methacholine chloride significantly increased the weight of airway fluid collections. Infusion of 5% hypertonic saline induced changes in the concns of electrolytes (but not of albumin) that correlated with changes in the plasma. The major differences in electrolyte and albumin concns in airway fluid and plasma likely reflect a bidirectional transepithelial flux of these ions. The regional differences in electrolyte concns and ratios may be due to differences in anatomic structure and in the functioning of ionic pumps along the tracheobronchial tree.

Albumins↗

PubMed1982

Diffusion barriers to passive lipid uptake of canine posterior tracheal epithelium.

In studies of passive uptake of canine posterior tracheal epithelium in vitro, we examined the effective resistance of the unstirred water layer (UWL) when the bulk phase of the preparation was stirred and unstirred. Rates of uptake of fatty acids were corrected for unstirred layer effects. The incremental change in free energy, derived from the linear relationship between uptake and chain length of lipids, was -271 cal/mol. Measurement of the effective thickness (d) and surface area (SW) of the UWL showed that d fell and SW rose as the rate of stirring increased. SW was less than 15% of the tracheal epithelial cell membrane's surface area. It is concluded that 1) lipid membrane of the tracheal epithelium and the overlying UWL represent the major diffusion barriers for lipid uptake across the tracheal epithelium; 2) failure to correct for the UWL resistance leads to serious errors in the estimates of permeability properties of the epithelium to lipids; and 3) the unstirred layer severely limits the proportion of cell membrane available for transport in vitro.

Animals↗

PubMed1981

Nonelectrolyte permeability of canine tracheal epithelium.

We examined the nonelectrolyte permeability characteristics of canine tracheal epithelium in vitro and confirmed that the transepithelial potential difference was 26.3 +/- 2.2 mV, lumen negative. Exposure of the epithelium to a sucrose osmotic load resulted in a streaming potential (SP); a linear relationship was noted between osmotic load and SP. The presence of an osmotic load did not change the short-circuit current and the SP disappeared after removal of the osmotic load. The SP developed with urea, thiourea, D-xylose, and l-glycine were similar to the SP developed for equimolar concentrations of sucrose. The urea and insulin spaces were similar magnitude. When the bulk phase was stirred at 600 rpm, the effective thickness of the unstirred water layer (UWL) external to the epithelial surface was 144 +/- 12 micron. These results support the suggestion that the Staverman reflection coefficients (sigma) of these probe molecules are similar, the estimates of sigma are valid despite the presence of an UWL, and the tracheobronchial epithelium has a pore size smaller than the hydrodynamic radius of urea.

Animals↗

PubMed1980

Effects of sighs and different tidal volumes on compliance, functional residual capacity and arterial oxygen tension in normal and hypoxemic dogs.

In order to assess the usefulness of sighs in preventing deterioration of arterial PO2 (PaO2), functional residual capacity (FRC), and compliance in hypoxemic patients, the authors studied 20 anesthetized and paralyzed dogs. The dogs were ventilated with either normal (11.5 ml/kg) or large (23 ml/kg) tidal volumes and their lungs were either normal or made edematous with oleic acid injection. Sighs (46 ml/kg) were administered periodically and PaO2, FRC, and compliance were measured at intervals between sighs. In dogs with normal lungs, regardless of tidal volume, sighs produced a transient increase in compliance and FRC but PaO2 was not significantly affected. In dogs with pulmonary edema, sighs produced inconsistent effects on FRC and compliance and, interestingly, PaO2 decreased after the sighs may be unnecessary in patients with pulmonary edema, especially when they are already receiving large tidal volumes.

Animals↗

PubMed1980

Simultaneous comparison of canine tracheal transport of anion exchange resin particles to albumin macroaggregates and sulfur colloid. Effects of subcutaneous methacholine chloride and intravenous hypertonic saline.

We compared simultaneously measured canine tracheal transport rates of Dowex anion exchange particles with macroaggregates of albumin, and with sulfur colloid. We found that sulfur colloid moved significantly faster than large Dowex particles (diameter 180 micrometer), which had transport rates similar to macroaggregates of albumin, and small Dowex particles diameter 3 micrometer). We examined the alteration of airway fluid caused by intravenous 5% saline or subcutaneous methacholine chloride. We then studied the effects of the altered airway fluid on the transport rates of large Dowex particles and sulfur colloid. We found that sulfur colloid continued to be transported faster than Dowex particles. Although we do not have an explanation for the faster transport of sulfur colloid, we believe that the physiochemical properties of the marker may influence its rate of tracheal transport.

Albumins↗

PubMed1979

Lung function in diaphragm pacing.

Electric stimulation of the diaphragm via the phrenic nerve to induce ventilation has recently been used for the long-term management of chronic ventilatory insufficiency. Since 1973 three patients with inadequate alveolar ventilation have been treated with diaphragm pacing at the Toronto Western Hospital. Two, who had quadriplegia due to lesions of the spinal cord in the upper cervical region and a severe restrictive ventilatory defect, were treated with continuous diaphragm pacing. The third patient required assisted nocturnal ventilation because of primary alveolar hypoventilation. All three patients tolerated the diaphragm pacing well, and pulmonary function tests showed satisfactory gas exchange with the patients breathing room air. This form of therapy seems to be a practical clinical method of managing chronic ventilatory failure in patients with lesions of the upper cervical cord or primary alveolar hypoventilation.

Adolescent↗

PubMed1979

Diphenylhydantoin and pulmonary function.

Thirty-nine epileptic patients underwent pulmonary function testing. Twenty-one of these patients, ranging in age from 16 to 44 years, had taken diphenylhydantoin (DPH) for 2 to 17 years. Eighteen patients, who had taken other anticonvulsants for similar time periods served as controls. Five patients in the DPH group had lung volume abnormalities, four had abnormal airway function, and five had abnormalities of alveolar gas mixing. One patient in the control group had lung volume abnormalities, two had abnormal airway function, and five had abnormalities of alveolar gas mixing. Statistical analysis revealed no significant differences between the groups, or between either group and predicted values.

Adolescent↗

PubMed1979

Effects of temperature, relative humidity, and mode of breathing on canine airway secretions.

Airway secretions were collected from the upper trachea of eight healthy nosebreathing mongrel dogs under general anesthesia, and the electrolytes and osmolality of these secretions were determined. Compared to plasma, secretions contained 15% higher Na+ and 33% higher Cl-, were 18% higher in osmolality, but had a lower Na+/Cl- throughout the 6-h experiments. When six nose-breathing dogs were exposed to air at 28.5 degrees C and 95% relative humidity, secretion osmolality became lower, but Na+/Cl- remained unchanged. In four other dogs, secretions approached the osmolality of plasma when inspired air was at 36.4 degrees C and 100% relative humidity. These secretions contained 22% higher Cl- and a lower Na+/Cl- than plasma. The differences between airway secretions and interstitial fluid suggest that secretions are formed by active Cl- transport. In another four dogs, secretion osmolality was higher with mouth breathing than breathing through the nose. Inasmuch as humidified and warmed air lowered and mouth breathing raised the osmolality of airway secretions, we postulate that the hyperosmolality of secretions results from water loss from the airway surface during conditioning of inspired air.

Animals↗

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↗

PubMed1978

Nasal mucociliary clearance in man.

Nasal mucociliary clearance was measured in healthy young human subjects and tracheal clearance in the experimental animal under a wide variety of conditions. There is a broad range of clearance rates whether at standard ambient conditions (23 degrees C, 50% relative humidity) or in the face of a number of environmental variables. The degree to which those differences are attributable to the effectiveness of ciliary beating or the character of airway secretions is not known. Studies of tracheobronchial secretions simultaneous with clearance measurement in the anaesthetized dog have not yet provided a definite answer. Variations in upper respiratory defence mechanisms may bear some relationship to the aetiology of small airway disease in the lungs.

Adult↗

PubMed1978

Simultaneous canine tracheal transport of different particles.

We describe a method to study simultaneously the transport of 2 different markers in the canine trachea. In our studies, we found that choice of radioisotopic label and variation in marker size from 3 to 180 micrometer did not affect the transport rate of basic anion exchange resin particles. Furthermore, anion exchange and acidic cation exchange particles of the same size had similar tracheal transport rates. This method may help to determine the influence of the physicochemical properties of markers on mucous transport.

Animals↗

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↗

PubMedDate not supplied

Canine tracheal mucus transport of particulate pollutants: comparison of radiolabeled corn pollen, ragweed pollen, asbestos, silica, and talc to Dowex anion exchange particles.

Canine tracheal mucous transport rates of each of two organic (corn and ragweed pollen), and three inorganic (chrysotile asbestos fibers, silica, and talc), 99mTc labeled pollutants were simultaneously measured against those of 125I labeled Dowex anion exchange resin particles in healthy animals. The method of labeling of the pollutants with 99mTc is described. With the exception of ragweed pollen, which moved 15% faster than the reference marker (P <.02), we found no difference in the transport rates of these particulate pollutants and the reference marker. We conclude that the particulate pollutants studied are handled by the mucociliary system in a similar fashion, and that the transport rates of Dowex particles represent valid measurements of the transport rates of these pollutants.

Animals↗

PubMedDate not supplied

Do area-based markers of poverty accurately measure personal poverty?

Area-based markers of deprivation (e.g., postal codes) are commonly used to identify groups of people with low socioeconomic status (SES); the validity of this approach, however, remains unknown. In this study, we determined the accuracy of using income quintile groups calculated on the basis of the median family income of each forward sortation area (1996 Canadian census) to identify those living in poverty (i.e., annual family income of < $12,620). The sensitivity and specificity of using the lowest income quintile to capture those in poverty were 26% and 83%, respectively (likelihood ratio (LR) of 1.49; 99% CI, 1.49 to 1.50). Among those in non-metropolitan and metropolitan areas, the LRs were 1.26 (99% CI, 1.26 to 1.27) and 2.01 (99% CI, 2.01 to 2.02), respectively. The use of postal codes as the only marker to identify people with low SES may result in substantial misclassification of personal poverty, particularly in non-metropolitan areas.

Adolescent↗