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PubMed2002

Determinants of respiratory system input impedance and bronchodilator response in healthy Finnish preschool children.

In order to study the determinants of respiratory system impedance and bronchodilator response in preschool children, a sample (n = 109) of healthy children (age 2.1-7.0 years) attending kindergarten was measured by using the impulse oscillometry. Their selection was based on a standardized questionnaire, negative skin prick test results and clinical examination, and sufficient cooperation. Triple measurements of respiratory resistance (Rrs) and reactance (Xrs) at 5, 10, 15 and 20 Hz, total respiratory impedance (Zrs), the resonance frequency (Fr) and the frequency dependence of resistance (dRrs/df) were performed, to determine individual mean values. Measurements were repeated after inhalation of 300 microg salbutamol (n = 89) or placebo (n = 19). At the baseline, Zrs and Rrs5-20 showed negative, and Xrs5-20, Fr and dRrs/df positive correlations with age, height and weight. However, logarithmic transformed height was the best independent variable for the regression equations of all the oscillometric variables. After inhalation of placebo, none of the oscillometric variables changed significantly. In the salbutamol group, the mean (SD) change in Rrs5 was -0.187 (0.124) kPa l(-1) s(-1) and -19.2 (10.2)%, corresponding to a lower reference limit of -36.9%. Both the within-test and between-test repeatabilities for the measurement of respiratory resistance were acceptable, for Rrs5 the coefficients of variation being 6.2 and 6.1%, respectively. As the overall success rate in our sample was high (89%), the forced oscillation technique seems to be a useful method in assessing respiratory function and bronchial lability in preschool children.

Administration, Inhalation↗
PubMed1997

The elephant's respiratory system: adaptations to gravitational stress.

Elephants have had to adapt to gravitational stresses imposed on their very large respiratory structures. We describe some unusual features of the elephant's respiratory system and speculate on their functional significance. A distensible network of collagen fibers fills the pleural space, loosely connects lung to chest wall but appears not to constrain lung-chest wall movements. Myriad spaces within the network and its rich supply of capillaries suggest effective local sources and sinks for pleural fluid that may replace the gravity-dependent flows of smaller mammals. The lung is partitioned into approximately equal to 1 cm3 parenchymal units by a system of thick, elastic septa that ramify throughout the lung from origins on the lung's elastic external capsule. Parenchymal units suspended upon the elastic septal system protect dependent alveoli from compression, thereby reducing the usual gravitational gradient of lung expansion. Intra-pulmonary airways are devoid of cartilage, instead they appear to derive resistance to collapse from tethering forces of the attached septa.

Adaptation, Physiological↗
PubMed2000

[Effects of environmental tobacco smoke on lower respiratory system of children under 5 years of age].

OBJECTIVE: To determine the effects of second-hand smoke in the respiratory system of children under 5 years old. METHODS: A cross sectional study of a total of 1,104 children under 5 years old. Information about respiratory symptoms and illness, family history of respiratory diseases, smoking habits of household members and housing conditions were assessed by home interviews with the children's parents. RESULTS: We studied 546 boys and 558 girls. Among 611 children exposed to second-hand smoke, 82% had respiratory problems (odds ratio = 1.64; 95% confidence interval: 1.21-2.20). Children whose parents were smokers at the time of the survey were more likely to experience wheezing than children of nonsmoking parents (odds ratio = 1.66; 95% confidence interval: 1.21-2.27), shortness of breath (odds ratio = 1.91; 95% confidence interval: 1. 36-2.67), morning and day time or night coughs (odds ratio = 1.58; 95% confidence interval: 1.09-2.28). The odds ratio for asthma, bronchitis and pneumonia was greater for children exposed to second-hand smoke (odds ratio = 1.60; 95% confidence interval: 1. 11-2.31). CONCLUSIONS: Maternal smoking, paternal smoking, family history of respiratory diseases, and housing conditions are considered risk factors for respiratory diseases in children.

Age Distribution↗
PubMed1988

Comparison between dynamic lung compliance and static compliance of the respiratory system in sick newborn infants.

We compared dynamic lung compliance (Cldyn) determined by the oesophageal balloon technique with static compliance of the respiratory system (Crs) determined by an airway occlusion technique in 10 newborn infants with various cardio-respiratory diseases. The correlation between the two variables was linear and statistically significant (r = 0.911, p less than 0.0003; Cldyn = 1.51.Crs-0.48). Crs varied significantly less than Cldyn (mean coefficient of variation 3.9 for Crs vs. 9.3 for Cldyn; t = 6.06, p less than 0.0002). Since Crs is closely related to lung compliance but a more reliable parameter and technically easier to assess, we recommend the assessment of Crs instead of Cldyn in clinical practice.

Female↗
PubMed1984

Epidemiological-environmental study of lead acid battery workers. III. Chronic effects of sulfuric acid on the respiratory system and teeth.

The effects of long-term exposure to sulfuric acid mist on the teeth and respiratory system were studied in 248 workers in five plants manufacturing lead acid batteries. The prevalence of cough, phlegm, dyspnea, and wheezing as determined by questionnaire were not associated with estimates of cumulative acid exposure. There was only one case of irregular opacities seen on the chest radiographs. There was no statistically significant association of reduced FEV1, peak flow, FEF50, and FEF75 with acid exposure although the higher exposed group had lower mean values. FVC in the high exposure group showed a statistically significant reduction compared to the low exposure group, but there was no significant association when exposure was analyzed as a continuous variable. The ratio of observed to expected prevalence of teeth etching and erosion was about four times greater in the high acid-exposure group. The earliest case of etching occurred after 4 months exposure to an estimated average exposure of 0.23 mg/m3 sulfuric acid.

Adult↗
PubMed1994

Hering-Breuer reflex and respiratory system compliance in the first year of life: a longitudinal study.

The airway occlusion technique for measuring passive respiratory mechanics in infants relies on an ability to evoke the Hering-Breuer lung inflation reflex (HBR). However, there is conflicting evidence regarding the persistence of the HBR beyond the early newborn period. This study was designed to assess maturational changes in HBR activity and passive total respiratory system compliance (Crs) in healthy infants during the 1st yr of life. The strength of the HBR was assessed from the relative change in expiratory time (TE) after brief end-inspiratory airway occlusions compared with resting TE during spontaneous breathing. Crs was measured using the multiple-occlusion technique. Paired measurements of HBR activity and Crs were obtained during sedated sleep in 30 infants at 4-8 wk and at 1 yr of age. Significant HBR activity during tidal breathing persisted throughout the 1st yr of life, with TE increasing during occlusion by at least 26% in every infant. However, the relative strength of the reflex response decreased from a mean of 88.3% (range, 34-160%) at approximately 6 wk to 50.3% (range, 26-125%) by 1 yr of age (P < 0.001). All infants showed an increase in Crs with age, with mean Crs increasing from 60.1 +/- 8.9 (SD) to 149.0 +/- 20.6 ml/kPa between 6 wk and 1 yr. However, there was no apparent relationship between the magnitude of decline in HBR response and the age-related changes in Crs.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed2005

The effect of volatile anesthetics on respiratory system resistance in patients with chronic obstructive pulmonary disease.

We examined the effect of isoflurane and sevoflurane on respiratory system resistance (Rmin,rs) in patients with chronic obstructive pulmonary disease (COPD). The diagnosis of COPD rests on the presence of airway obstruction, which is only partially reversible after bronchodilator treatment. Ninety-six consecutive patients undergoing thoracic surgery for peripheral lung cancer were enrolled. They were divided into two groups: preoperative forced expiratory volume in 1 s/forced vital capacity ratio <70% or >70%. Rmin,rs was measured after 5 and 10 min of maintenance anesthesia by using the constant flow/rapid occlusion method. Maintenance of anesthesia was randomized to thiopental 0.30 mg . kg(-1) . min(-1) or 1.1 minimum alveolar anesthetic concentration end-tidal isoflurane or sevoflurane. Eleven patients were excluded: two because anesthesia was erroneously induced with propofol and nine because of an incorrect tube position. Maintenance with thiopental failed to decrease Rmin,rs, whereas both volatile anesthetics were able to decrease Rmin,rs in patients with COPD. The percentage of patients who did not respond to volatile anesthetics was larger in those with COPD as well. In conclusion, we have demonstrated that isoflurane and sevoflurane produce bronchodilation in patients with COPD.

Aged↗
PubMed2001

Continuous on-line measurements of respiratory system, lung and chest wall mechanics during mechanic ventilation.

OBJECTIVE: We present a concept of on-line, manoeuvre-free monitoring of respiratory mechanics during dynamic conditions, displaying calculated alveolar pressure/volume curves continuously and separating lung and chest wall mechanics. DESIGN: Prospective observational study. SETTING: Intensive care unit of a university hospital. PATIENTS: Ten ventilator-treated patients with acute lung injury. INTERVENTIONS: Different positive end-expiratory pressure (PEEP) and tidal volumes, low flow inflation. MEASUREMENTS AND RESULTS: Previously validated methods were used to present a single-value dynostatic compliance for the whole breath and a dynostatic volume-dependent initial, middle and final compliance within the breath. A high individual variation of respiratory mechanics was observed. Reproducibility of repeated measurements was satisfactory (coefficients of variations for dynostatic volume-dependent compliance: < or =9.2% for total respiratory system, < or =18% for lung). Volume-dependent compliance showed a statistically significant pattern of successively decreasing compliance from the initial segment through the middle and final parts within each breath at all respiratory settings. This pattern became more prominent with increasing PEEP and tidal volume, indicating a greater distension of alveoli. No lower inflection point (LIP) was seen in patients with respiratory rate 20/min and PEEP at 4 cmH2O. A trial with low flow inflation in four of the patients showed formation of a LIP in three of them and an upper inflection in one. CONCLUSIONS: The monitoring concept revealed a constant pattern of successively decreasing compliance within each breath, which became more prominent with increasing PEEP and tidal volume. The monitoring concept offers a simple and reliable method of monitoring respiratory mechanics during ongoing ventilator treatment.

Adult↗
PubMed1989

Response localization of the pharmacological agents histamine and salbutamol along the respiratory system by forced oscillations in asthmatic subjects.

The bronchodilating effect of 1 mg and 0.4 mg salbutamol on the impedance of the respiratory system was studied in 25 asthmatic subjects after histamine-induced bronchoconstriction. Histamine caused an increase of respiratory resistance (Rrs) at lower frequencies and a frequency dependence of Rrs. Respiratory reactance (Xrs) decreased at all frequencies after histamine challenge. These changes can be explained by peripheral airway obstruction. Impedance measurements performed 5 min after inhalation of 1 mg and 0.4 mg salbutamol showed a decrease of Rrs values at lower frequencies, a disappearance of the frequency dependence of Rrs, and a significant increase of Xrs values. No significant differences in absolute changes of Rrs and Xrs are observed between the salbutamol regimens. These changes after inhalation of salbutamol can be explained by supposing a predominant action on the peripheral airways.

Adult↗
PubMedDate not supplied

[Effects of histamine on the pressure-volume curve of the respiratory system in the guinea pig].

Intravenous infusion of histamine has been shown to constrict smooth muscle of alveolar ducts. In this study, we have assessed the effects of a prolonged infusion of histamine to obtain a steady state response on quasistatic pressure-volume curves (P-V curves) together with the changes in dynamic compliance (Cdyn) and conductance (G) of the respiratory system. Increasing doses of histamine were given in order to obtain the dose-response characteristics of the changes in Cdyn, G and P-V curves. In nine anesthetized guinea-pigs under mechanical ventilation, administration of histamine resulted in a fall in Cdyn and G with a decrease of 50% of initial value approximately for 150 ng X kg-1 X s-1 of histamine. Modifications of the P-V curves were characterized by a decrease in the maximal volume, and an increase in the hysteresis of the P-V loop due to the downward displacement of the inflation limb. With infusion of histamine, there was a large decrease of quasi-static compliance which appeared to account for most of the decrease in dynamic compliance. Such changes in P-V curves can be related both to a closure of alveolar ducts and to an alteration of lung distensibility. Comparison of the dose-response curves for the different parameters indicated that Cdyn and G reflect, at least in part, events occurring in the periphery of the lung.

Animals↗
PubMed1994

Relationship between expired capnogram and respiratory system resistance in critically ill patients during total ventilatory support.

To examine the relationship of expired capnograms and respiratory system resistance (Rrs) in intubated critically ill patients, we consecutively studied 41 mechanically ventilated patients to (1) analyze the association between expired CO2 slope and auto-positive end-expiratory pressure (auto-PEEP), between Rrs and auto-PEEP, between Rrs and expired CO2 slope, and between Rrs and arterial minus end-tidal PCO2 gradient (PaCO2-PETCO2 gradient) and (2) to investigate the capacity of the expired CO2 slope and PaCO2-PETCO2 gradient to predict Rrs during mechanical ventilation. Regression analysis found a close correlation between Rrs and expired CO2 slope (r = 0.86; p < 0.001), between Rrs and auto-PEEP (r = 0.75; p < 0.001), and between auto-PEEP and expired CO2 slope (r = 0.74; p < 0.001). Weak correlation was found between Rrs and PaCO2-PETCO2 gradient (r = 0.48; p < 0.01). Prediction interval limits at 95 percent confidence level for Rrs are approximately +/- 7.39 cm H2O/L/s from the predicted value obtained by the regression equation, where Rrs = 11.42 + 2.28 expired CO2 slope. These observations suggest that CO2 elimination in critically ill patients is strongly modulated by lung, airway, endotracheal tube, and ventilator equipment resistances. Although continuous capnogram waveform monitoring at the bedside might be useful to assess Rrs, very accurate predictions could be done only in determinate patients.

Adult↗