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At least 19 recordsLinked to original sources
PubMed1976

Endotracheal tube as a factor in measurement of respiratory mechanics.

The measurement of respiratory mechanics is frequently performed on intubated patients. This study shows the effect which the turbulent and inertial characteristics of an endotracheal tube have on the accuracy of the measurement. Two techniques are examined utilizing a mechanical model: the least-squares and the phasor technique. It is concluded that both techniques will give erroneous results if the characteristics of the tube are not accounted for. The error is markedly reduced if the turbulent and inertial terms are accounted for in the analysis.

Air Movements↗
PubMed1979

Detection of respiratory mechanical dysfunction by forced random noise impedance parameters.

Respiratory mechanical parameters were computed from forced random noise impedance data in normal adults (group 1), asymptomatic smokers (group 2), and patients with obstructive pulmonary disease (group 3). Mean values for all derived parameters were significantly different (p less than 0.025) for group 3. Mean values of resonant frequency, the ratio of low-frequency (5 to 9 Hz) resistance to high-frequency resistance (15 to 19 Hz), and conductance normalized by height, were significantly different (p less than 0.05) between groups 1 and 2. This approach appears to yield respiratory mechanical parameters that are sensitive to mechanical alterations induced by early pulmonary disease. The rapid, noninvasive, and effort-independent nature of this approach make it especially useful for epidemiologic studies and for studies of "noncooperative" subjects.

Forced Expiratory Volume↗
PubMed1976

Effect of feeding on ventilation and respiratory mechanics in newborn infants.

Measurements of ventilation and respiratory mechanics were made before and after tube feeding in 24 infants. In 12 infants with the respiratory distresssyndrome tidal volume tended to fall after feeding; as the respiratory rate increased after feeding; as the respiratory rate increased after feeding, minute ventilation remained unchanged. Hypoventilation is therefore unlikely to be the cause of hypoxaemia after feeding. Compliance, resistance, and the work of breathing showed no changes after feeding. In 12 healthy infants feeding had no effects on pulmonary function. There was a slight rise in compliance and a tendency for work of breathing to fall after feeding. Respiratory rate, tidal volume, and minute ventilation remained unchanged. There was therefore no evidence of adverse effects of feeding on any of the factors measured. It is suggested that hypoxaemia without hypoventilation after feeding in infants with pre-existing respiratory distress syndrome might be attributable to a reduction in functional residual capacity associated with a greater extent of airways closure than before feeding.

Enteral Nutrition↗
PubMed1979

[An unhomogeneous model of the respiratory mechanics (author's transl)].

Mechanics of the respiratory system was simulated on analogue computer by a two-compartmental model. Each compartment expresses a functionally (not anatomicall) different part of the lungs, corresponding to some unhomogeneity within the system. The influence of this unhomogeneity on characteristics parameters of the lung (resistance, compliance) was analysed in simulated experiments. This seems to show the way how to express the degree of the lung function disturbance by some quantitative relations.

Airway Resistance↗
PubMed1979

Anaphylaxis in the monkey: respiratory mechanics, acid-base status and blood gases.

Aggregate anaphylaxis was induced by intravenous injection of the specific antigen in eight ovalbumin-sensitized monkeys. Changes in respiratory mechanics, acid-base status and blood gases were studied during the following half hour. Within 1 minute after challenge, a short period of respiratory depression, probably reflex-mediated, was observed. This was followed by hyperventilation, and arterial PCO2 decreased. There was a rapid increase in pulmonary resistance (Rpulm) and a concomitant decrease in pulmonary dynamic compliance (Cdyn), suggesting constriction of smooth muscles in the lung. Rpulm returned to the control value but Cdyn remained depressed, as a result of constriction of small airways and pulmonary congestion. Oxygen saturation in arterial blood decreased slightly due to a marked desaturation of mixed venous blood and increased venous admixture. Progressive metabolic acidosis developed, indicating poor tissue oxygenation and perfusion. The changes observed in this study were not severe enough to cause any major disturbance of the gas exchange in the lungs, despite a severe anaphylactic shock.

Acid-Base Equilibrium↗
PubMed1978

Respiratory mechanics in conscious sheep: response to methacholine.

Most currently used animal models of allergic airway diseases differ from human asthma in that induced bronchospasm in the former is not accompanied by pulmonary hyperinflation. In the present investigation, we chose unsedated, restrained sheep to determine the effect of cholinergic bronchial provocation on respiratory mechanics, functional residual capacity (FRC), and arterial blood gases. Seven animals had been actively sensitized by intramuscular injections of Ascaris suum extract, and four untreated animals served as controls. After inhalation of nebulized 1% methacholine solution, mean pulmonary resistance increased significantly in the sensitized sheep from a base line of 2.4 +/- 0.7 (SD) cmH2O/(l/s) to a peak value after 5 min of 7.9 +/- 4.0 cmH2O/(l/s). This was accompanied by a significant increase of mean FRC from 0.99 +/- 0.14 liters to 1.31 +/- 0.24 liters. The observed changes were transient, and after 60 min, pulmonary resistance and FRC had returned to base-line values. No significant changes occurred in static lung compliance, PaO2, PaCO2, and pH. In the control animals, methacholine provocation did not produce changes in pulmonary function. These results indicate that, in sensitized conscious sheep, induced bronchospasm is associated with pulmonary hyperinflation.

Animals↗
PubMed1976

Respiratory mechanics with constant flow inspiration. A comparison of two measurement techniques.

Resperatory compliance and resistance were measured during positive pressure ventilation in anaesthtized, paralysed dogs. Airway pressures measured during constant-flow inspiration allowed the calculation of pulmonary and chest-wall resistances, and static and non-static compliances. Contiguous studies of dynamic compliance and resistance allowed comparison of the two techniques, and the level of agreement was reasonalble. Cconstant-flow inflation of the lungs allows a simple means of measuring respiratory mechanics, and should be valid for the observation of short-term changes in the apnoeic patient.

Airway Resistance↗
PubMed1976

Dynamic surface tension properties of mixed lecithin-cholesterol films related to the respiratory mechanics.

A bubble method was used to record dynamic area/surface tension diagrams of mixed lecithin-cholesterol films prepared at different weight ratios. The lecithin/cholesterol weight ratios were: 1:2, 1:1, 4:1, 6:1, 8:1 and 12:1. The minimum surface tension is about 20 dyn/cm for all weight ratios at amplitudes of 75, 25, 12.5, 6 and 3% area oscillation. The maximum surface tension depends on both the amplitude of area oscillation and the lecithin/cholesterol weight ratio. The maximum surface tension increases with increasing amplitude. At the amplitudes 25, 12.5, 6 and 3% the maximum surface tension is significant higher at the weight ratios 1:2 and 1:1 compared to the other ratios. In addition, equilibrium surface tensions during interruptions of the oscillation at maximum and minimum area were recorded. The equilibrium surface tension increases with increasing amplitude up to 25% area oscillation. A static hysteresis seems to remain. Some consequences regarding the pulmonary respiratory mechanics are discussed.

Cholesterol↗
PubMed1979

Respiratory mechanics in normal bonnet and rhesus monkeys.

We measured lung volumes and quasi-static volume-pressure relationships in 22 normal upright bonnet (Macaca radiata) and 12 rhesus (M. mulatta) monkeys. In comparison with interspecies pulmonary function/body weight regressions our monkeys' lung volumes are larger and their lungs are considerably more compliant, but their chest wall compliance is similar to a wide range of mammalian species. However, chest wall compliance of our monkeys was found to be considerably less than that of other more commonly used experimental mammals such as dogs, cats, and rodents. The monkey chest walls were found to be about four times as stiff (3.3 +/- 0.1 (ml/cmH2O)/kg), whereas their lungs were nearly twice as compliant (9.2 +/- 0.7 (ml/cmH2O)/kg) compared to those of supine beagle dogs. Thus, their stiff chest wall sets their functional residual capacity (64.1 +/- 1.2% TLC30) at a much larger percentage of total lung capacity (TLC30) than that of the supine beagle dog (33.8% TLC30). Residual volume (13.2 +/- 1.9% TLC30) equaled the trapped gas volume after bilateral thoracotomy and was set by airway closure. We found more hysteresis area in the chest wall than in the lungs. Our measurements indicate that the static mechanical behavior of the respiratory system of the monkey compares well to man and that the monkey has considerable merit as an animal model for human respiratory function and disease research.

Animals↗
PubMed1979

Catecholaminergic depressant effects on bulbar respiratory mechanisms.

On the basis of histochemical and pharmacological studies, catecholamines have been implicated in central mechanisms controlling respiration. This hypothesis was tested in iontophoretic studies on neurones located in bulbar respiratory centres. Adrenaline and noradrenaline had a predominantly depressant effect on respiratory as well as on closely situated non-respiratory units. These depressions were mimicked by the application of isoproterenol and clonidine; acetylcholine and serotonin had inconsistent effects on these neurones. In control experiments, microinjections, using a Hamilton syringe, were made in the area of bulbar respiratory centres: noradrenaline, but not serotonin, depressed the central respiratory activity reflected in the phrenic nerve discharge. These results suggest that specific adrenergic and noradrenergic depressant mechanisms could affect both respiratory and other physiological centres at the bulbar level.

Acetylcholine↗
PubMedDate not supplied

[Respiratory mechanics during speech at the time of a static physical load].

In 12 healthy male test subjects, aged 18--35, respiratory characteristics during talking at rest and when doing static exercises were studied by simultaneous recording of their pneumotachograms, integrated spirograms and transpulmonary intrathoracic pressures. By building pressure-volume curves for lungs and correcting them for transpulmonary pressure, variations in the pressure under the vocal cords when saying a standardized phrase were determined as related to the exercise level. The relationship between the rate and volume parameters of pulmonary ventilation and airway resistance during talking, on the one hand, and the level of exercises, on the other, was established.

Adolescent↗
PubMed1977

The respiratory mechanism of aerosol inhalation in the treatment of partial airway obstruction.

There is a sensory system within the mucosa of the nose and supraglottic larynx that appears to be both mechanosensitive and chemosensitive. Our data suggest that the respiratory modification produced by microaerosol inhalation represents a mechanoreceptor rather than chemoreceptor response. Furthermore, the sensitivity of this reflex system appears aged-dependent, the data indicating a more active response early in life. From a clinical perspective, it is postulated that aerosol inhalation reflex alters the pattern of breathing, resulting in improved respiratory flow rates during partial upper airway obstruction. The mechanism of a favorable clinical response to mist inhalation has not been previously appreciated in this context.

Aerosols↗
PubMed1978

Respiratory mechanics in the anesthetized rat.

Functional residual capacity (FRC) and pressure-volume (PV) curves of the lung, chest wall, and total respiratory system were studied in 15 anesthetized rats, weighing 307 +/- 10 (SE) g. Pleural pressure was estimated from the esophageal pressure measured with a water-filled catheter. The FRC determined by body plethysmograph was slightly and significantly larger than FRC determined from saline displacement of excised lungs. The difference may be accounted for by O2 uptake by lung tissue, escape of CO2 through the pleura, and abdominal gas. Paralysis in the prone position did not affect FRC, and abdominal gas content contributed only slightly to the FRC measured by body plethysmograph. Values of various pulmonary parameters (mean +/- SE) were as follows: residual volume, 1.26 +/- 0.13 ml; FRC, 2.51 +/- 0.20 ml; total lung capacity, 12.23 +/- 0.55 ml; compliance of the lung, 0.90 +/- 0.06 ml/cmH2O; chest wall compliance, 1.50 +/- 0.11 ml/cmH2O; and respiratory system compliance, 0.57 +/- 0.03 ml/cmH2O. The lung PV curve did not show a consistent change after the chest was opened.

Anesthesia↗