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PubMed2001

Volume dependence of respiratory system resistance during artificial ventilation in rabbits.

The volume dependence of respiratory resistance (Rrs), usually observed during normal breathing, is expected to be accentuated during expiratory flow limitation (EFL). In order to quantify this dependence we studied the pressure, flow, and volume data obtained from eight New Zealand rabbits, artificially ventilated at different levels of applied expiratory pressure (0-10 hPa), before and during histamine i. v. infusion. EFL was provoked by lowering the expiratory pressure and was detected by the application of an additional negative expiratory pressure and by forced oscillations. The analysis of respiratory system mechanics was performed by multiple regression, using the classical linear first-order model and also a nonlinear model, accounting for volume dependence of Rrs. Both models satisfactorily fitted the data in the absence of EFL. The nonlinear model proved to be more appropriate in the presence of EFL. The coefficient expressing the volume dependence of Rrs (Rvd) was significantly more negative during EFL. Rvd values were highly correlated with the fraction of the tidal volume left to be expired at the onset of EFL. A threshold Rvd value of -1,000 (hPa x s x l(-2)) detected EFL with high sensitivity and specificity. We conclude that a strongly negative volume dependence of Rrs is a reliable and noninvasive index of EFL during artificial ventilation.

Animals↗

PubMed1979

[Penetration of solid particles in the respiratory system. Secondary immunity reactions to the inhalation of a dry aerosol (author's transl)].

Deposition in the respiratory system of an inhaled dry particle depends on many factors, particularly its aerodynamic diameter. The quantity deposited in each compartment of the respiratory tract can be approximately determined by mathematical laws, but ther are still controversies about large size particles. Thus pollens have been found by the authors beyond the larynx deep in the lung. The bronchopulmonary system is divided in two parts, anatomically and immunologically different. The local response, closely related to the antigen, depends also on the intimate contact between particles and the immunity defense system of the individual. Liberation and solubility of some antigenic fractions, perhaps enzymatic, would help their intra-epithelial penetration and contact with the secretory immunity system. The additional intervention of an extraepithelial response has been observed in bronchi after instillation of pollen in the rat. There is in the sensitized animal an intense cellular reaction amidst the mucous of bronchial lumen with macrophages adhering to pollen granules and forming rosettes.

Administration, Intranasal↗

PubMed1991

High frequency oscillatory ventilation near resonant frequency of the respiratory system in rabbits with normal and surfactant depleted lungs.

It has been suggested that high frequency oscillatory ventilation (HFV) might improve gas exchange and reduce the risk of pressure-related side-effects compared to conventional mechanical ventilation (CMV). Whereas most studies have used arbitrarily set frequencies for HFV, we evaluated the effects of HFV near resonant frequency (fr). Anaesthetised and tracheotomized adult rabbits (n = 10; 3.8-5.1 kg body weight) were ventilated by alternating periods of CMV and HFV near fr. Negative ventilator resistance was used for complete resistive unloading of the respiratory system before each HFV period. This enabled a continuous swinging at resonance thus allowing measurement of fr and selection of exactly that frequency for the HFV run. Intra-animal CMV-HFV comparisons (n = 4) were performed on each animal: with healthy lungs at a mean airway pressure (MAP) of 0.5 kPa and after saline lung lavage at MAPs of less than 1.5 kPa; 1.5-1.8 kPa; greater than 1.8 kPa. Surfactant removal caused total respiratory system compliance (Ctot) to decrease from 44 +/- 5 to 22 +/- 3 ml/kPa. Corresponding fr was 244 +/- 48 and 360 +/- 30 min-1, respectively. HFV produced effective pulmonary gas exchange but did not improve arterial oxygenation in comparison with CMV at matched MAPs both before and after surfactant depletion. Volume amplitudes of oscillation necessary to achieve normocapnia were slightly above the natural plus equipment (2 ml) dead space. Maximum intra-alveolar pressure (Pmax) was calculated for the HFV runs from MAP, Ctot, and the volume amplitude of oscillation. Pmax during CMV was nearly twice that during HFV at equivalent PaCO2 and equivalent MAPs throughout the experiments.

Animals↗

PubMed1995

Increased respiratory system resistance and bronchial smooth muscle hypertrophy in children with acute postoperative pulmonary hypertension.

Following surgery for congenital heart disease, there is often an increased reactivity of the pulmonary vasculature to stimuli, resulting in rapid increases in pulmonary artery pressure and a clinical impression of stiff lungs. Lung mechanics were measured in 30 children, mean age 6.7 +/- 4.1 mo, who were ventilated and had pulmonary artery pressure monitoring following surgery for congenital heart disease. A group of 15 patients developed postoperative pulmonary hypertension. In these patients, respiratory system resistance was 43% higher (p = 0.001) and compliance 11% lower (p = 0.004) during acute pulmonary hypertension compared with baseline pulmonary artery pressure. No changes in resistance or compliance were seen in the 15 patients who did not develop pulmonary hypertension. The changes in lung mechanics interfered with mechanical ventilation, resulting in a 9.4% rise in PaCO2 during pulmonary hypertension. The bronchial smooth muscle was found to be increased by 68%, and the vascular smooth muscle was more than twice normal in lung biopsies from 9 pulmonary hypertension patients compared with 6 age-matched postmortem controls patients who had no cardiac or pulmonary disease. The bombesin-immunoreactive pulmonary neuroendocrine cells (PNEC) were also increased in the pulmonary hypertension patients. These findings suggest a coconstriction and cohypertrophy of bronchial and vascular smooth muscle during pulmonary hypertension. Mediators, such as bombesin, endothelin-1, and serotonin, are known to be produced by PNEC and may be involved in the observed vasoconstriction, increased respiratory system resistance, and smooth muscle hypertrophy.

Acute Disease↗

PubMed1993

[Growth rate of Candida albicans (Robin, 1853)and Candida stellatoidea (Martin et Jones, 1938) isolated from the human respiratory system].

The study comprises an analysis of the growth rate of C. albicans and C. stellatoidea strains isolated from the respiratory system and incubated on Nickerson's and Sabouraud's agar in the dark and by light. The property to form hyphae and pseudohyphae by both species was used to evaluate the growth rate. The increase in their growth allowed to isolate the stages characteristic for growth and development of most fungi. Disturbances appeared with the fungi exposed to light which is the factor definitely setting back the growth. Faster growth and development was observed with C. stellatoidea.

Candida↗

PubMed1988

Chest wall and respiratory system mechanics in cats: effects of flow and volume.

The effects of inspiratory flow rate and inflation volume on the resistive properties of the chest wall were investigated in six anesthetized paralyzed cats by use of the technique of rapid airway occlusion during constant flow inflation. This allowed measurement of the intrinsic resistance (Rw,min) and overall dynamic inspiratory impedance (Rw,max), which includes the additional pressure losses due to time constant inequalities within the chest wall tissues and/or stress adaptation. These results, together with our previous data pertaining to the lung (Kochi et al., J. Appl. Physiol. 64: 441-450, 1988), allowed us to determine Rmin and Rmax of the total respiratory system (rs). We observed that 1) Rw,max and Rrs,max exhibited marked frequency dependence; 2) Rw,min was independent of flow (V) and inspired volume (delta V), whereas Rrs,min increased linearly with V and decreased with increasing delta V; 3) Rw,max decreased with increasing V, whereas Rrs,max exhibited a minimum value at a flow rate substantially higher than the resting range of V; 4) both Rw,max and Rrs,max increased with increasing delta V. We conclude that during resting breathing, flow resistance of the chest wall and total respiratory system, as conventionally measured, includes a significant component reflecting time constant inequalities and/or stress adaptation phenomena.

Animals↗

PubMedDate not supplied

Reduction of respiratory system resistance of rabbits with surfactant deficiency using a novel ultra thin walled endotracheal tube.

The ultra thin walled, two-stage endotracheal tube (UTW-TS-ETT) is very flexible, nonkinking, and has a widened extralaryngeal portion. The UTW-TS-ETT has a greater ID/OD (internal diameter/outer diameter) ratio than a comparable standard endotracheal tube (ST-ETT) because of its thinner wall: 0.2-0.25 mm in UTW-TS-ETT, compared to 0.55-0.8 mm in ST-ETT. The authors hypothesized that in an animal model of lung disease, significant reductions in respiratory system resistance (Rrs) of 30-40% would be achieved using the UTW-TS-ETT, compared to Rrs achieved with the comparable ST-ETT. This study compared the pulmonary mechanics of rabbits (N = 17, body weight 3.4-4.7 kg) before and after induction of surfactant deficiency, using either ST-ETT (OD 4.9 mm, ID 3.5 mm) or UTW-TS-ETT (OD 5.0 mm, ID 4.6 mm). Animals were sedated, paralyzed, and ventilated by an ETT placed through a tracheotomy incision. Surfactant deficiency was induced by lavaging the lungs with normal saline (10 ml/kg). Pulmonary mechanics were measured on identical ventilator settings for each ETT used at baseline and at 45 min after lavage. Compared to ST-ETT, UTW-TS-ETT reduced Rrs by 50.6 +/- 8.7% in normal lungs (significantly more than 40%; p < 0.01), and by 41.47 +/- 16.2% in surfactant deficient lungs (significantly more than 30%; p < 0.05). Tidal volume increased with UTW-TS-ETT in all animals but did not achieve statistical significance. The UTW-TS-ETT did not induce significant changes in respiratory system compliance, PaO2, PaCO2, or pH. It is concluded that UTW-TS-ETT significantly reduces Rrs in rabbits with either normal lungs or with surfactant deficient lungs. This novel ETT may be beneficial for ventilated patients with increased Rrs, by effecting a decrease in Rrs and thus reducing the work of breathing and improving ventilation efficiency.

Animals↗

PubMed1998

Total respiratory system compliance after thoracoplasty.

Recent attention has been directed towards the deleterious effects of the sequelae of pulmonary tuberculosis on respiratory function. Thus, a study was undertaken to find out to what extent the deformity of thorax after thoracoplasty increases the mechanical work of breathing. Compliance of the total respiratory system (Crs) was measured with a pressure-type body plethysmograph in nine post-thoracoplasty tuberculosis patients, 15 patients with pulmonary tuberculosis and three patients with pleural diseases. Mean Crs in nine post-thoracoplasty tuberculosis patients was 0.0861 cmH2O-1, and that in six patients with moderately advanced pulmonary tuberculosis was 0.0841 cmH2O-1. Mean Crs (0.1301 cmH2O-1) in nine patients with a minimum lesion of tuberculosis was not different from the reference Crs values reported to date by several authors. Crs was significantly correlated with vital capacity, but not with functional residual capacity. There was no difference in specific Crs between post-thoracoplasty tuberculosis patients and patients with moderately advanced pulmonary tuberculosis. Crs of patients with a pleural disease was smaller than Crs of patients with a minimal lesion of pulmonary tuberculosis. The deformity of thorax after thoracoplasty caused a decrease of Crs. However, ventilation is not as severely impaired as anticipated from the degree of thorax deformity on chest X-ray film, providing that movement of the diaphragm is unrestricted.

Adult↗

PubMed1983

Comparative biology of small granule cells and neuroepithelial bodies in the respiratory system. Short review.

Small granule epithelial cells and clusters of these cells termed neuroepithelial bodies are widely distributed in the respiratory systems of vertebrates, according to observations made in 24 species. The cells are thinly scattered along extrapulmonary and intrapulmonary airways from the larynx to the entrances of the alveoli. As a rule they escape notice unless demonstrated by special light microscopic methods including silver impregnation, PAS-lead hematoxylin staining, or immunocytochemical localization of a marker enzyme, neuron-specific enolase, all of which reveal small granule cells as a class. They are also recognizable in electron micrographs by their characteristic 1,000 to 3,000 A dense-core granules. These can differ in appearance from cell to cell within the same or different species, and small granule cells also can differ in their anatomical relationships or in their content of pharmacological agents like serotonin and peptide hormones bombesin, calcitonin, or leu-enkephalin. Current evidence thus clearly points out the heterogeneity of the class, although it is inadequate to characterize the presumptive endocrine or paracrine function of any of its members specifically. This brief review gives an idea of the range of animals surveyed for small granule cells as well as similarities and differences among cells from different species. It concludes with comments on practical methods for revealing these cells and guidance to sources of detailed information about them.

Animals↗

PubMed1995

-Structure of the respiratory system of the Ulodera Hynobius neblosus tokyoensis Tago, with special reference to the distribution of serotonin-immunoreactive cells in its respiratory tract epithelium.

The respiratory tract epithelium in many vertebrate species has a neuroepithelial endocrine (NEE) system. This system is composed of solitary NEE cells or organoid cell groups called neuroepithelial bodies (NEBs). In response to chemical and physical stimuli, NEE cells may release bioactive substances. Serotonin, one of the biogenic amines, well-known as a constricter of smooth muscle, can be found in NEE cells, serotonin-immunoreactive cells can be used as a marker for these cells. Comparative histological studies of lower vertebrates can improve our understanding of mammalian respiratory systems. The Tokyo salamander (Hynobius neblosus tokyoensis Tago), classified as Ulodera, is particularly useful for comparative studies of respiration. In this study, the serial sections of respiratory tract of the Tokyo salamander were stained by a commonly used staining method and by an immunocytochemical method for serotonin, and the distribution of serotonin-immunoreactive cells in the respiratory tract was examined. The respiratory tract was found to be connected to the alimentary tract via an aditus laryngis, which opens on the medio-ventral side of the esophagus. The laryngotrachea was slit-like or elliptically shaped with a total length of about 3.5 mm, joining the aditus laryngis. The laryngotrachea was supported by a pair of lateral cartilages, and a fibromuscular layer was seen between the cartilages and the epithelium. In the cranial region, a laryngeal sphincter was seen around the laryngotrachea. The laryngotrachea branches into a pair of tube-like lungs, that are about 17-20 mm in length. Two apposed primary trabeclae run along the entire length of the lung wall, perpendicular to the axis, and containing the pulmonary arteries and veins. The lungs were divided into two portions: 1) an airway portion (trabeclae, septa) in which smooth muscles surrounding the large vessels were well developed, and 2) a respiratory portion which was give that name because it has well developed capillary networks that were assumed to be involved in gas exchange. The lumen of the laryngotrachea and the pulmonary airway portion contained pseudostratified cilio-mucous epithelium. In the caudaldorsal region of the laryngotrachea adjacent to the lungs, the non-ciliated respiratory epithelium was seen lining the capillaries. In cilio-mucous epithelium of the laryngotrachea, all serotonin-immunoreactive cells were solitary. They apposed to be columnar, cuboidal, triangular, oval, and flask- or spindle-shaped. Solitary serotonin-immunoreactive cells were classified "open type cell" with appical process reaching to the luminal surface and "closed type cell" insulated from the lumen by an epithelial lining. In the pulmonary airway portion, serotonin-immunoreactive cells were solitary cells and in clusters. Serotonin-immunoreactive cells were widely distributed throughout the respiratory tract, but they tended to be found mainly in the cranial portion. The density was highest in the area with the laryngeal sphincter, and decreased caudally in the laryngotrachea and lung. No serotonin-immunoreactive cells were found in the respiratory portion of the dorsal-caudal area of the laryngotrachea or in the part of the lung with non-ciliated cells. So the structure and distribution of serotonin-immunoreactive cells in the respiratory tract of the Tokyo salamander are similar to those of NEE cells and NEBs in mammalian respiratory systems. The density of serotonin-immunoreactive cells appears to be related to the distribution of smooth muscles in the fibromuscular layer and airway portion. The cells may be involved in regulation of the respiratory system. Serotonin is released in response to stimulation, which could result in constriction of the fibromuscular layer and shrinkage of the laryngotracheal cavity, and may regulate pulmonary volume by constricting smooth muscles

Animals↗

PubMed1957