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At least 613 records · Page 34Linked to original sources
PubMed1991

Glycine receptor-mediated fast synaptic inhibition in the brainstem respiratory system.

The involvement of glycinergic neurotransmission in the central regulation of respiration was investigated by administration of specific receptor agonists and antagonists into the 4th cerebral ventricle of the rabbit. Central respiratory activity was assessed by cycle-triggered averaging of phrenic nerve activity (PNA). Glycine reduced the peak amplitude of PNA and increased the duration of the respiratory phases. Conversely, strychnine decreased the duration of both phases, being more effective in expiration. Strychnine converted inspiratory ramp activity to a decrescendo type of pattern, with the highest discharge activity present at the onset of the inspiratory phase. Strychnine induced tonic PNA lasting throughout expiration with a decrescendo type of activity. In many cases strychnine induce apneusis with tonic PNA being at a level of about 2/3 of its maximum value during control. We conclude that glycinergic neurotransmission is important for the maintenance of the respiratory rhythm as well as the generation of normal respiratory pattern. Glycine could be involved in phasic as well as tonic inhibitory neurotransmission within the central respiratory system.

Animals↗
PubMed1986

Respiratory system impedance in patients with acute left ventricular failure: pathophysiology and clinical interest.

To investigate the relationship between alterations in lung mechanics and acute pulmonary vascular congestion, repeated measurements of the respiratory system impedance (Zrs) were performed in 11 patients with and in seven without acute left ventricular failure. Indexes of Zrs were obtained by calculating the average and slope of the resistance and reactance in low (10 to 20 Hz) and high (20 to 50 Hz) frequency intervals. Zrs indexes in patients with ventricular failure differ significantly from those in patients without failure. Pulmonary vascular congestion is regularly associated with an abnormal frequency dependence of resistance at low frequencies and with an increased resonant frequency. Discriminant analysis of Zrs indexes allows 92% correct classification of pulmonary capillary wedge pressures lower than and those equal to or higher than 18 mm Hg. Zrs differences between patients with and without left ventricular failure are consistent with the presence of a small airways obstruction even in patients with mild left ventricular failure. Furthermore, use of Zrs indexes permits moderate and severe pulmonary vascular congestion to be distinguished from one another and this is probably due to a significant narrowing of the large airways during severe left ventricular failure.

Adult↗
PubMed1995

Respiratory system mechanics in mice measured by end-inflation occlusion.

Characterization of pulmonary function parameters in mice will facilitate the dissection of genetic mechanisms underlying airway hyperresponsiveness. We evaluated acetylcholine (ACh)-induced respiratory system resistance (Rrs) and elastance (Ers) in A/J and C3H/HeJ mice and compared these results with the previously used airway pressure-time index (APTI). A low-dead-space ventilatory system was designed to ventilate anesthetized mice with constant inspiratory flow. The end-inflation occlusion method was used to measure Rrs and Ers at baseline and after intravenous ACh (12.5-75.0 micrograms/kg) challenge. ACh induced a dose-dependent rise in Rrs and Ers in A/J mice, whereas minimal changes were observed in C3H/HeJ mice. A/J mice had a higher baseline Rrs, yet the response to ACh was independent of baseline Rrs. Additionally, sequential ACh challenges led to augmented responses. Rrs, Ers, and APTI were strongly correlated, and each was useful to detect differences in interstrain cholinergic-induced airway responsiveness. The Rrs detected the smallest differences between the strains of mice studied.

Acetylcholine↗
PubMed2000

Diurnal variations of respiratory system resistance and compliance derived from input impedance in asthmatic children.

The forced oscillation technique is more and more often used in the evaluation of the results of bronchomotor tests and in assessing respiratory mechanics in children. There is little information available concerning diurnal variability of indices of respiratory mechanics derived from input impedance (Z(rsin)). In 29 asthmatic children, aged 8-13 years we have studied diurnal changes of respiratory system resistance (R(rs)) and compliance (C(rs)) by measuring input impedance with the head generator every hour from 08:00 to 21:00 h. Diurnal coefficient of variation for zero frequency resistance (R(0)), mean resistance in the range 4-32 Hz (R(avg)) and C(rs) were 10.6+/-4.9, 11.2+/-4.5 and 8.9+/-3.3%, respectively. Significant circadian rhythm on R(0) was detected in 11 children, on R(avg) in nine children and on C(rs) in seven children. Only three children had all the three rhythms significant. We conclude, that diurnal variability of input impedance derived indices of respiratory mechanics is rather small, and circadian variability is present in about one third of the examined children. Diurnal variations of respiratory mechanics in children with significant circadian rhythm do not exceed 20%.

Adolescent↗
PubMed1985

Second cancer following cancer of the respiratory system in Denmark, 1943-80.

A 10% increased risk of developing a second cancer was observed among approximately 36,000 persons reported to the Danish Cancer Registry with a cancer of the respiratory system during 1943-80. This estimate is markedly influenced by a striking tendency by physicians not to report or the Cancer Registry not to accept a report of a second lung cancer following a primary lung cancer (14 observed vs. 99 expected). A significant 30% excess of all second cancer was seen after laryngeal cancer (368 vs. 282), whereas the 22% excess following cancer of the nasal cavities and paranasal sinuses did not quite reach the level of statistical significance (95% CI = 0.9-1.6). For cancers of the lung and larynx, second cancers arose mainly in the buccal cavity, bladder, kidney (after lung cancer only) and lung (after laryngeal cancer only). These second cancers may be due to common carcinogenic factors, most likely tobacco. Elevated risks of second cancers of the breast, cervix uteri, and other female genital organs were found consistently. Radiotherapy may have contributed to the increased risk of breast cancer, but the excess risk of cancer of the female genital organs other than the cervix was unexpected. Although not significant, the risk of esophageal cancer following cancer of the larynx was below expectation (1 vs. 4.1), which was surprising because alcohol consumption and smoking are thought to be common risk factors for these 2 sites. Significant excesses of pancreatic cancer were observed following cancers of the lung, larynx, and nasal cavities, which might be due to more careful medical surveillance of these patients or to common risk factors such as cigarette smoking. Finally, the risk of a patient developing liver cancer after lung cancer was significantly elevated (22 vs. 11.6). This increase is unlikely to be due to misdiagnosed metastases from the lung, inasmuch as the risk was generally elevated throughout the observation period.

Denmark↗
PubMed1980

[Chemotherapy of tuberculosis and the immunomechanisms of the macroorganism. I. Inhibition of migration of leucocytes and the concentration of serum-immunoglobulin A in the phase of prime therapy of tuberculosis of the respiratory system (author's transl)].

The inhibition of migration of leucocytes (stimulated by PPD) and the concentration of serum-immunoglobulin A had been controlled in 50 patients with bacteriologically verified tuberculosis of the respiratory system. All patients showed a clear hypersensitivity of delayed type with inhibition of migration of leucocytes and high concentrations of serum IgA before the therapy run. In patients with effective therapy there resulted a decline of hypersensitivity of delayed type and of the concentration of IgA. All patients, who still had mycobacterium tuberculosae in the sputa in spite of a correct therapy for 3 months no changes of controlled parameters could be recognized. These results will be interpreted that the effect of an antimycobacterial therapy is accompanied by a clear decline of hypersensitivity of delayed type and parallel decline of protective immunity at least of humoral character, likely not very favourable for the patients.

Antitubercular Agents↗
PubMed1982

Self-instruction and assessment in techniques of intensive care using a computer model of the respiratory system.

There are considerable logistical difficulties involved in providing an adequate training programme for each new doctor when starting intensive care. One solution is to use an interactive computer terminal and provide programmes for self-instruction and assessment. Using a computer model of the respiratory system linked to a computer-assisted instructional driver we have developed instructional exercises on the management of artificial ventilation and the treatment of respiratory failure. Each teaching session contains explanatory text, multiple choice questions and model simulations. The student can interact with the simulations, appropriate assistance being provided when required, while his answers are marked and assessed with further explanation when necessary. The use of computer models adds a new dimension to computer-assisted learning techniques and is particularly applicable to intensive care medicine.

Computer-Assisted Instruction↗
PubMed1995

T model partition of lung and respiratory system impedances.

The aim of this work was to demonstrate that the three compartments of the lung T network and the chest wall impedance (Zcw) can be identified from input and transfer impedances of the respiratory system if the pleural pressure is recorded during the measurements. The method was tested in six healthy volunteers in the range of 8-32 Hz. The impedances resulting from the decomposition confirm the adequacy of the monoalveolar structure commonly used in healthy subjects. Indeed, the T shunt impedance is well modeled by a purely compliant element, the mean compliance [0.038 +/- 0.081 (SD) l/kPa], which coincides within 9.5 +/- 6.3% of the alveolar gas compressibility derived from thoracic gas volume (0.036 +/- 0.011 l/kPa). The results obtained provide experimental evidence that the alveolar gas compression is predominantly isothermal and that lung tissue impedance is negligible throughout the whole frequency range. The shape of Zcw is consistent with a low compliance-low inertance pathway in parallel with a high compliance-high inertance pathway. We conclude that the proposed method is able to reliably identify the T network featuring the lung and Zcw.

Adult↗
PubMed1992

The valves, baffles and sphincters of the respiratory system.

'Starting with the integument we see many organs are contractile sacs or multiples thereof which tubes or bags constitute the major part of the entire body' (1). The lungs are a collection of these universal contractile chambers connected in chains and bunches. Such containers typically have muscular walls which stretch and contract to fill and empty also valves or sphincters to regulate the flow between neighbouring chambers. The heart, stomach and uterus are familiar examples. In some systems (e.g. the digestive, renal and respiratory tracts) traffic is also between the milieu exterior and the milieu interior through the organ's wall which is part of the integument. These movements from organ to organ or milieu to milieu involve pressure variations generated by the concerted actions of the mural and valvular muscles. A muscle usually has a doppel-gänger so they are arranged in reciprocating pairs, supinators with pronators, flexors with extensors, chamber walls with sphincters etc.

Bronchi↗