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At least 307 records · Page 17Linked to original sources
PubMed2006

Autonomic nervous system control of the cardiovascular and respiratory systems in asthma.

Patients with asthma have exaggerated bronchoconstriction of their airways in response to certain indirect (e.g. cold air, allergens, dust, exercise) or direct (e.g. inhaled methacholine) stimuli. This 'hyper-reactivity' usually co-exists with airway inflammation, although the pathophysiological mechanisms underlying these changes are not fully understood. It is likely that this hyper-reactivity is associated with abnormal autonomic nervous system (ANS) control. In particular, the parasympathetic (vagal) component of the ANS appears to be implicated in the pathogenesis of asthma. In addition, several studies have suggested the existence of differential alteration in ANS function following exercise in asthmatics compared with non-asthmatic individuals. Several early studies suggested that the altered autonomic control of airway calibre in asthma might be reflected by a parallel change in heart rate. Cardiac vagal reactivity does indeed appear to be increased in asthma, as demonstrated by the cardiac response to various autonomic functions tests. However, other studies have reported a lack of association between bronchial and cardiac vagal tone, and this is in accord with the concept of system-independent ANS control. This review provides a discussion of cardiovascular-autonomic changes associated with either the pathophysiology of asthma per se or with asthma pharmacotherapy treatment. Previous investigations are summarised suggesting an apparent association between altered autonomic-cardiovascular control and bronchial asthma. The full extent of autonomic dysfunction, and its clinical implications, has yet to be fully determined and should be the subject of future investigation.

Adrenergic beta-Agonists↗
PubMed1978

Inhalation toxicity studies on cigarette smoke. V. Deposition of smoke particles in the respiratory system of rats under various exposure conditions.

This paper describes a dosimetry experiment on rats which was designed to make a contribution towards the optimisation of exposure conditions for inhalation toxicology studies with smoke aerosols. The main conclusions drawn from the work are: (i) Under continuous exposure conditions the deposition of total particulate matter (TPM) in the respiratory system and carboxyhaemoglobin (COHb) levels in blood were linearly dependent on the concentration of smoke in the exposure chamber. (ii) Intermittent exposure gave relatively lower TPM deposition compared to continuous exposure, even after allowing for differences in actual exposure times. (iii) For arithmetically equivalent exposure levels, short exposure to high concentration gave greater TPM deposition than long exposures to low smoke concentrations. (iv) There was a good correlation between lower respiratory system (LRS) and lung deposition of TPM and blood COHb level for both continuous and intermittent exposure conditions. These findings are discussed in relation to the conduct of inhalation studies with tobacco smoke.

Animals↗
PubMed2001

Determination of equivalent dose rates and committed effective doses in the respiratory system from the inhalation of radon decay products by using SSNTD and a dosimetric compartmental model.

Alpha activities per unit volume, due to radon (222Rn), thoron (220Rn) and their progenies, were evaluated inside different dwelling rooms by using CR-39 and LR-115 II solid state nuclear track detectors (SSNTD) and calculating their mean critical angles of etching. The influence of the ventilation rate and nature of the building material has been investigated. Equivalent dose rates and annual committed effective doses due to the inhalation of radon decay products have been determined in the respiratory system by using a dosimetric compartmental model. The influence of the deposition fraction, residual time and activity absorbed fraction of the respiratory system compartments for the radon daughters has been studied.

Air Pollution, Indoor↗
PubMed2001

Assessment of respiratory system mechanics by artificial neural networks: an exploratory study.

We evaluated 1) the performance of an artificial neural network (ANN)-based technology in assessing the respiratory system resistance (Rrs) and compliance (Crs) in a porcine model of acute lung injury and 2) the possibility of using, for ANN training, signals coming from an electrical analog (EA) of the lung. Two differently experienced ANNs were compared. One ANN (ANN(BIO)) was trained on tracings recorded at different time points after the administration of oleic acid in 10 anesthetized and paralyzed pigs during constant-flow mechanical ventilation. A second ANN (ANN(MOD)) was trained on EA simulations. Both ANNs were evaluated prospectively on data coming from four different pigs. Linear regression between ANN output and manually computed mechanics showed a regression coefficient (R) of 0.98 for both ANNs in assessing Crs. On Rrs, ANN(BIO) showed a performance expressed by R = 0.40 and ANN(MOD) by R = 0.61. These results suggest that ANNs can learn to assess the respiratory system mechanics during mechanical ventilation but that the assessment of resistance and compliance by ANNs may require different approaches.

Animals↗
PubMed1971

A mathematical model of the controlled plant of the respiratory system.

Ability to predict the dynamic response of oxygen, carbon dioxide tensions, and pH in blood and tissues to abrupt changes in ventilation is important in the mathematical modeling of the respiratory system. In this study, the controlled plant (the amount and distribution of O(2) and CO(2)) of the respiratory system is modeled. Although the body tissues are divided into a finite number of "compartments" (three tissue groups), in contrast to earlier models, the blood and tissue gas tensions within each compartment are considered to be continuously distributed in time and in one spatial coordinate. The mass conservation equations for oxygen and carbon dioxide involved in the blood-tissue gas exchange are described by a set of partial differential equations which take into account convection of O(2) and CO(2) caused by the flow of blood as well as diffusion due to local tension gradients. Nonlinear algebraic equations for the dissociation curves, which take into account the Haldane and Bohr effects in blood, are used to obtain the relationships between concentrations and partial pressures. Time-variable delays caused by the arterial and venous transport of the respiratory gases are also included. The model so constructed successfully reproduced actual O(2) and CO(2) tensions in arterial blood, and in muscle venous and mixed venous blood when ventilation was abruptly changed.

Animals↗
PubMed1985

Second cancer following cancer of the respiratory system in Connecticut, 1935-1982.

The risk of a person developing a second primary cancer was evaluated in approximately 30,000 persons who developed cancer of the respiratory system in Connecticut between 1935 and 1982. A significant 44% excess of all second cancers was observed following cancer of the lung (614 observed vs. 426 expected). The excess of second tumors was 72% following cancer of the larynx (541 vs. 314) and 34% following cancer of the nasal cavities and sinuses (43 vs. 32). For cancers of the lung and larynx, second cancers arose mainly along the respiratory tract or other sites associated with cigarette smoking (oral cavity, bladder, kidney). A threefold excess of esophageal cancer followed cancer of the larynx, which was indicative of risk factors in common (alcohol and tobacco) and possibly an effect of radiotherapy. Radiotherapy may have contributed also to the increased risk of second lung and breast cancers. A slight excess risk of leukemia after lung cancer points to a possible effect of chemotherapy given for certain histologic types. An unexpected finding was a significant 50% increased risk of colon cancer following cancer of the larynx. Significant excesses of prostate cancer are probably artifacts associated with increased medical surveillance and higher autopsy rates among cancer patients than in the general population. No deficits of any second cancers were observed. The risk of a second cancer developing did not appear to vary by sex or time since initial diagnosis, except that the risks following cancer of the nasal cavities and sinuses returned to normal levels among long-term survivors. Among persons observed for 10 or more years after their initial diagnosis of cancers of the lung or larynx, the risk of developing a second cancer remained high, i.e., on the order of 50% above expectation. Further analytic studies should clarify the role of smoking, alcohol, other life-style and host factors, and various forms of therapy on the risk of second cancers following cancer of the respiratory system.

Connecticut↗
PubMed1993

Endothelin and the respiratory system.

Pharmacological research involving the endothelin peptides has emphasized their activities in vascular systems, from both physiological and pathophysiological perspectives. However, the endothelins are known also to be synthesized and released from respiratory epithelial cells and to have potent effects in nonvascular components of the respiratory tract. Douglas Hay, Peter Henry and Roy Goldie summarize present understanding of the pharmacology of the endothelins in the respiratory system and assess the potential pathophysiological role in asthma.

Asthma↗
PubMed2001

[Circulatory and respiratory systems in children after surgical correction of atrial septal defect type II (ASD II)].

The main objective of the study was to evaluate the conditions of circulatory and respiratory system 1-5 years after surgical correction of atrial septal defect (ASD II) in 112 children who had been operated at Silesian Medical Centre in Katowice in 1989-1993. Obtained results were compared with these ones found in the group of 60 healthy children. Mean age of study group was 7.78 +/- 4.46 years at the time of examination and 5.34 +/- 3.98 at the time of the operation. Twenty older children in the mean age 11 +/- 4.5 years (necessity for cooperation) were selected from the study group to perform the respiratory system tests. These tests were performed 7 days prior to operation and repeated 8 to 12 months afterwards. The following indices were determined: FVC--forced volume capacity, FRC--functional residual capacity, RV--residual volume, TLC--total lung capacity, FEV1--forced first second expiratory volume, PEF--peak expiratory flow, MEF 75-50-25% FVC--maximum expiratory flow at 75-50-25% of forced volume capacity, ITGV--intrathoracic gas volume, Raw-respiratory tract resistance, CL, st--static compliance of lung, DL, CO[SB]--lung diffusion capacity for carbon monoxide and D/VA--Krogh transfer coefficient. Circulatory system tests included: medical interview, physical examination, routine and 24-hour ambulatory ECG, echocardiography. There was found that children after ASD II closure have efficient circulatory system and most of them have normal ECHO results. Almost 40% of the children within 1 to 5 years following ASD operations have cardiac arrhythmias found in 24-hour ECG, but significant arrhythmias are seen only in 17.8% of the subjects. Most of the rhythm disturbances were mild. Significant arrhythmias and sinus node dysfunction were observed more frequently among the children who underwent surgical correction than in the healthy control group. Statistically significant deterioration of lung diffusion capacity for carbon monoxide (DL,CO[SB]) and Krogh coefficient (D/VA) has been found after the surgery. Thus, it is concluded that some pulmonary abnormalities may persist or even increase after successful ASD operation.

Child↗
PubMed1994

Evaluation of respiratory system resistance in mechanically ventilated patients: the role of the endotracheal tube.

OBJECTIVE: To investigate the role played by the endotracheal tube (ETT) in the correct evaluation of respiratory system mechanics with the end inflation occlusion method during constant flow controlled mechanical ventilation. SETTING: General ICU, university of Rome "La Sapienza". PATIENTS: 12 consecutive patients undergoing controlled mechanical ventilation. METHODS: We compared the values of minimal resistance of the respiratory system (i.e. airway resistance) (RRS min) obtained: i) subtracting the theoretical value of ETT resistance from the difference between P max and P1, measured on airway pressure tracings obtained from the distal end of the ETT; ii) directly measuring airway pressure 2 cm below the ETT, thus automatically excluding ETT resistance from the data. RESULTS. The values of RRS min obtained by measuring airway pressure below the ETT were significantly lower than those obtained by measuring airway pressure at the distal end of the ETT and subtracting the theoretical ETT resistance (4.5 +/- 2.8 versus 2.5 +/- 1.6 cm H2O/l/s, p < 0.01). CONCLUSION: When precise measurements of ohmic resistances are required in mechanically ventilated patients, the measurements must be obtained from airways pressure data obtained at tracheal level. The "in vivo" positioning of ETT significantly increases the airflow resistance of the ETT.

Acute Disease↗
PubMed1996

New aspects of pulmonary mechanics: "slowly" distensible compartments of the respiratory system, identified by a PEEP step maneuver.

OBJECTIVE: The aims of the present study were 1) to evaluate a method for identification of "slowly" distensible compartments of the respiratory system (rs), which are characterized by long mechanical time constants (RC) and 2) to identify "slowly" distensible rs-compartments in mechanically ventilated patients. DESIGN: Prospective study on a physical lung model. SETTING: Intensive Care Unit, University Hospital, Tübingen. PATIENTS AND PARTICIPANTS: 19 patients with severe lung injury (acute respiratory distress syndrome, ARDS) and on 10 patients with mild lung injury. MEASUREMENTS AND RESULTS: Positive end-expiratory pressure (PEEP)-increasing and -decreasing steps of about 5 cmH2O were applied and the breath-by-breath differences of inspiratory and expiratory volumes (delta V) were measured. The sequence of delta Vs were analyzed in terms of volume change in the "fast" compartment (Vfast), the "slow" compartment (Vslow), total change in lung volume (delta VL) and mechanical time constant of the slow compartment (RCslow). Thirty-eight measurements in a lung model revealed a good correlation between the preset Vslow/delta VL and Vslow/delta VL measured: r2 = 0.91. The Vslow/delta VL measured amounted to 0.94 +/- 0.15 of Vslow/delta VL in the lung model. RCslow measured was 0.92 +/- 0.43 of the RCslow reference. Starting from a PEEP level of 11 cmH2O PEEP-increasing and PEEP-decreasing steps were applied to the mechanically ventilated patients. Three out of ten patients with mild lung injury (30%) and 7/19 patients with ARDS (36.8%) revealed "slowly" distensible rs-compartments in a PEEP-increasing step, whereas 15/19 ARDS patients and 1/10 patients with mild lung injury showed "slowly" distensible rs-compartments in a PEEP-decreasing step (78.9% vs 10%, P < 0.002, chi-square test). CONCLUSIONS: The gas distribution properties of the respiratory system can be easily studied by a PEEP-step maneuver. The relative contribution of the "slow" units to the total increase of lung volume following a PEEP step could be adequately assessed. "Slowly" distensible rs-compartments could be detected in patients with severe and mild lung injury, however significantly more ARDS patients revealed "slow" rs-compartments in PEEP-decreasing steps. The influence of "slowly" distensible rs-compartments on pulmonary gas exchange is unknown and has yet to be studied.

Adult↗
PubMed1991

Analysis of behavior of the respiratory system in ARDS patients: effects of flow, volume, and time.

The effects of inspiratory flow (V) and inflation volume (delta V) on the mechanical properties of the respiratory system in eight ARDS patients were investigated using the technique of rapid airway occlusion during constant-flow inflation. We measured interrupter resistance (Rint,rs), which in humans represents airway resistance, the additional resistance (delta Rrs) due to viscoelastic pressure dissipations and time constant inequalities, and static (Est,rs) and dynamic (Edyn,rs) elastance. The results were compared with a previous study on 16 normal anesthetized paralyzed humans (D'Angelo et al. J. Appl. Physiol. 67: 2556-2564, 1989). We observed that 1) resistance and elastance were higher in ARDS patients; 2) with increasing V, Rint,rs and Est,rs did not change, delta Rrs decreased progressively, and Edyn,rs increased progressively; 3) with increasing delta V, Rint,rs decreased slightly, delta Rrs increased progressively, and Est,rs and Edyn,rs showed an initial decrease followed by a secondary increase noted only in the ARDS patients. The above findings could be explained in terms of a model incorporating a standard resistance in parallel with a standard elastance and a series spring-and-dashpot body that represents the stress adaptation units within the tissues of the respiratory system.

Aged↗
PubMedDate not supplied

[Effect of starvation on animals with varying reactivity of the respiratory system].

Experiments were conducted on rats with high and low reactivity of the respiratory system to study the effect of starvation in tests with a hypoxic gas mixture containing 11% O2. Rats with high reactivity were more sensitive to starvation. Animals with low reactivity were marked by a more resistant regulation of energy metabolism, which was evidence of the significant role of individual reactivity of rats to reduced oxygen partial pressure in the inhaled gas mixture. The higher level of O2 tension in the muscle in unaltered oxygen consumption in rats with low reactivity after fasting for 3 days and breathing air may be the results of growth of the oxygen diffusion coefficient.

Animals↗
PubMedDate not supplied

The effect of environmental pollution on the respiratory system of lignite miners: a diachronic study.

BACKGROUND: It is not known whether working in surface lignite mines can cause x-ray lesions or disorders of respiratory function. OBJECTIVES: The aim of the study was to investigate the diachronic impact of environmental pollution on the respiratory system of lignite miners at mines in Eordea, Greece. METHODS: Cases of 199 workers (Group A) residing permanently in the Eordea valley and 151 (Group B) living outside the Eordea valley were studied during Phase I and then re-examined after three years (Phase II). These cases were compared to those of 71 office workers living in Eordea valley (Group C) and to 96 living in Grevena, a region without pollution (Group D). The study included the completion of the MRC questionnaire for the detection of respiratory diseases, pulmonary function tests, measurement of diffusion capacity, otorhinolaryngologic examination, rhinomanonetry as well as chest and paranasal cavity X-rays. RESULTS: Chronic bronchitis was reported by 26.8%, 24.8%, 17.9% and 10.6% respectively of the subjects of groups A, B, C and D according to the answers of the questionnaire (p<0.001). The spirometry and diffusion capacity findings presented no considerable differences either in the 4 groups or between phases I and II of the study. The main problems were detected in the upper airways. A very high prevalence of severe nasal obstruction (73%, 71.2%, 55.7% and 19.3% in Groups A, B, C and D respectively) was detected. Furthermore, a high percentage of atrophic rhinitis (14%) was detected both among workers (Groups A and B) and subjects living in the Eordea valley who participated as controls (Group C). From the X-rays, hypertrophy of nasal turbinates-cartilage and polyposis was observed as follows: Group A: 53.9%, Group B: 48.1%, Group C: 46.5% and Group D: 20.3% (p<0.001). The findings related to the upper respiratory system may be due to excessive pollution by airborne particles (fly ash) pollution in the region and particularly to chromium, nickel, cobalt and lead found at high concentration levels in airborne dust. A marked association between the total air-flow in the nose and the mid-expiratory flow (p<0.01) was detected. CONCLUSIONS: We conclude that subjects working in lignite mines under conditions of excessive pollution by airborne contaminants have a high prevalence of atrophic rhinitis and, in addition to other standard examinations, should undergo rhinomanometry testing and X-ray imaging of the paranasal cavities.

Adult↗