Respiratory Volume Changes Research Articles

Subtyping emphysematous COPD by respiratory volume change distributions on CT

BackgroundThere is considerable heterogeneity among patients with emphysematous chronic obstructive pulmonary disease (COPD). We hypothesised that in addition to emphysema severity, ventilation distribution in emphysematous regions would be associated with...

Assessing vowel effects on voice quality, and voice quality effects on the respiratory system.

This study assesses (a) effects of vowel height and tense-lax status on the laryngeal closed quotient (CQ) and (b) whether respiratory volume changes vary with differences in CQ. German speakers produced words containing eight different vowels in normal and loud conditions. The only significant vowel effect was found for the /a:-a/ pair, with lower CQ in /a/ at normal intensity. There was an insignificant trend for lower CQ to be associated with more negative thoracic slopes. The CQ difference for the /a:-a/ contrast, which relies more on duration than other tense-lax pairs in German, requires further study.

A Hilbert-based method for processing respiratory timeseries

In this technical note, we introduce a new method for estimating changes in respiratory volume per unit time (RVT) from respiratory bellows recordings. By using techniques from the electrophysiological literature, in particular the Hilbert transform, we show how we can better characterise breathing rhythms, with the goal of improving physiological noise correction in functional magnetic resonance imaging (fMRI). Specifically, our approach leads to a representation with higher time resolution and better captures atypical breathing events than current peak-based RVT estimators. Finally, we demonstrate that this leads to an increase in the amount of respiration-related variance removed from fMRI data when used as part of a typical preprocessing pipeline.Our implementation is publicly available as part of the PhysIO package, which is distributed as part of the open-source TAPAS toolbox (https://translationalneuromodeling.org/tapas).

Exploring the source of short-term variations in respiratory data.

This study explores short-term respiratory volume changes in German oral and nasal stops and discusses to what extent these changes may be explained by laryngeal-oral coordination. It is expected that respiratory volumes decrease more rapidly when the glottis and the vocal tract are open after the release of voiceless aspirated stops. Two experiments were performed using Inductance Plethysmography and acoustics, varying consonantal properties, loudness, and prosodic focus. Results show consistent differences in respiratory slopes between voiceless vs voiced and nasal stops, which are more extreme in a loud or focused position. Thus, respiratory changes can even occur at a local level.

Breathing simulator of workers for respirator performance test.

Breathing machines are widely used to evaluate respirator performance but they are capable of generating only limited air flow patterns, such as, sine, triangular and square waves. In order to evaluate the respirator performance in practical use, it is desirable to test the respirator using the actual breathing patterns of wearers. However, it has been a difficult task for a breathing machine to generate such complicated flow patterns, since the human respiratory volume changes depending on the human activities and workload. In this study, we have developed an electromechanical breathing simulator and a respiration sampling device to record and reproduce worker’s respiration. It is capable of generating various flow patterns by inputting breathing pattern signals recorded by a computer, as well as the fixed air flow patterns. The device is equipped with a self-control program to compensate the difference in inhalation and exhalation volume and the measurement errors on the breathing flow rate. The system was successfully applied to record the breathing patterns of workers engaging in welding and reproduced the breathing patterns.

Use of thoracic impedance sensors to screen for sleep-disordered breathing in patients with cardiovascular disease

Screening patients for the possibility of sleep apnoea, one of the most common forms of sleep-disordered breathing, requires measurement of respiration. We propose a simple method to estimate the amplitude modulation of a respiratory tidal volume, using a semi-quantitative measure of respiration based on thoracic impedance (TI). Because respiratory volume changes may be accommodated by varying displacements of the rib cage (RC) and abdomen (AB), the latter produced by outward motion of the diaphragm, it is necessary for any useful measure of respiration to be closely related to both RC and AB displacements. Because the relative contributions of RC and AB displacements to respiratory tidal volume vary in different body positions, the present measurements were recorded from subjects in supine, and right and left lateral decubitus postures. We observed a clear linear relationship between TI and both RC and AB signals in all three body positions. There were no statistically significant differences between observed relationships between TI and AB and between TI and RC, and these relationships were independent of the body position. TI sensors appear to be a useful candidate for a simple method of screening for sleep apnoea, especially in a cardiology clinical setting. Further investigation is warranted for the refinement of algorithms to detect changes in amplitude modulation occurring with apnoeas and to remove artefacts due to gross body movements.

Validation of the thoracic impedance derived respiratory signal using multilevel analysis

The purpose of the current study was to validate the change in thoracic impedance (dZ) derived respiratory signal obtained from four spot electrodes against incidental spirometry. Additionally, a similar validation was performed for a dual respiratory belts signal to compare the relative merit of both methods. Participants were 38 healthy adult subjects (half male, half female). Cross-method comparisons were performed at three (paced) respiration frequencies in sitting, supine and standing postures. Multilevel regression was used to examine the within- and between-subjects structure of the relationship between spirometric volume and the respiratory amplitude signals obtained from either dZ or respiratory belts. Both dZ derived respiratory rate and dual belts derived respiratory rate accurately reflected the pacing frequencies. For both methods, fixed factors indicated acceptable but posture-specific regression on spirometric volume. However, random factors indicated large individual differences, which was supported by variability of gain analyses. It was concluded that both the dZ and dual belts methods can be used for measurement of respiratory rate and within-subjects, posture-specific, changes in respiratory volume. The need for frequent subject-specific and posture-specific calibration combined with relatively large measurement errors may strongly limit the usefulness of both methods to assess absolute tidal volume and minute ventilation in ambulatory designs.

Changes of Respiratory Mechanics in Pregnant Woman under General Anesthesia for Cesarean Section

Background: In pregnant woman, the respiratory system is influenced by the hormonal environment and an enlarged gravid uterus. After delivery of the fetus, and contraction of the uterus, changes in the respiratory system produced by the mechanical effect of the gravid uterus may decrease or be reversed. We designed this study to observe changes in the respiratory mechanics in pregnant woman under general anesthesia for cesarean section. Methods: 15 pregnant women at term, ASA 1 were studied. Induction was performed with thiopental/succinylcholine and maintained with , and enflurane until delivery. Just before delivery, enflurane was discontinued. Vecuronium was given at 0.1 mg/kg iv 4 min after induction, and after delivery, 1 mg was given as needed. Inspired tidal volume, expired tidal volume, inspired minute ventilation, expired minute ventilation, airway peak pressure, plateau pressure, expired volume during the first 1 second/expired tidal volume (V1.0), dynamic compliance and end-tidal were continuously measured just after induction, at delivery and 5, 10, 15, 20, 25, 30, 40 and 50 min after delivery. Blood pressure, heart rate and oxygen saturation were also measured. Results: Compared to the value after induction, values after delivery showed no significant changes in inspired tidal volume or minute volume, but significantly increased in expired tidal volume and minute volume and dynamic compliance, and a significant decrease in airway peak pressure, plateau pressure, V1.0 and end-tidal . Blood pressure and heart rate increased significantly after induction, compared to before induction. Oxygen saturation was maintained at 99-100%. Conclusions: After delivery, the effects of the gravid uterus on the respiratory system rapidly disappeared, in particular changes of pressure in the airway preceded the respiratory volume changes.

A simple and reliable method to calibrate respiratory magnetometers and Respitrace.

We present a simple and reliable method to calibrate respiratory magnetometers and Respitrace to infer respiratory volume changes. As in earlier methods, we assume two degrees of freedom in the chest wall and that volume displacement depends linearly on surface motion at the rib cage and abdomen. Because the area of the rib cage is larger, a given motion of its surface produces a greater lung volume change; therefore, the rib cage motion signal is given a larger gain before the two signals are added to estimate volume. In contrast to earlier methods, we use a "standard ratio" to weight relative gains of the rib cage and abdominal signals for all subjects rather than determining a gain ratio for each individual subject. Our procedure does not require subjects to perform the sometimes difficult isovolume maneuvers used in the calibration method of Konno and Mead (J. Appl. Physiol. 22: 407-422, 1967), does not require statistical computation used in the multiple-breath linear regression method, and does not produce the occasional substantial errors in gain ratio that may occur with the other methods. When magnetometers are used, the standard ratio is 4:1 (rib cage-to-abdomen); when Respitrace is used, the standard ratio is 2:1. In 11 subjects, calibration with standard ratios was as accurate as the isovolume and linear regression techniques. Accuracy during normal breathing was nearly always within 10% (median 2%), but occasional large errors occurred with both instruments.

Comparison of the reliability of two respiratory valves during maximal exercise testing

The change in respiratory volume during exercise because of the use of different types of respiratory apparatus has previously been reported in the literature. However, to our knowledge, there has been no report of the reliability of measurement for commonly used apparatuses. The purpose of this study was to compare the reliability of the Hans Rudolph 2700 NRB valve with the Vacumed Speak‐Easy Mask II during maximal exercise testing. Eight moderately trained college‐aged women performed two maximal graded exercise tests using each apparatus. Breath‐by‐breath measurements of pulmonary variables were collected and a moving point average displayed, every 15 seconds. A MANOVA (valve × trial × subject) revealed no significant difference (p > 0.05) in oxygen consumption, respiratory exchange ratio, rating of perceived exercise, minute ventilation (VE), tidal volume (Vt), or breathing frequency (fB) between the two pieces of equipment. Intraclass reliability of breath‐by‐breath measurements of VE, Vt, and fB was...

Response of roosters to resistive loads at constant chemical drive to breathe

This study investigated the role of mechanoreceptors in the respiratory responses to resistive loading in roosters. Adult roosters were unidirectionally ventilated (maintaining a constant chemical drive to breathe). Electrical circuits assessed the respiratory muscle pressure (Pmus) and controlled the relationship between Pmus and the respiratory volume changes. Respiratory volume changes similar to those achieved by flow-resistive unloading or loading were produced by the circuits, imposing a ‘virtual’ resistance (R v). When R v was doubled (decreased rate of volume change, n=6, tidal volume (V t, measured by whole body plethysmography) decreased significantly (28%), while thoracic volume (V rip, measured by respiratory inductance plethysmography) did not change. When R v was quadrupled ( n=4) V t and V rip decreased significantly (53% and 24%, respectively). Changing R v to one half the normal value ( n=5) did not affect these parameters. Inspiratory time and Pmus were not significantly altered at any R v. It is concluded that, at constant chemical drive, mechanoreceptors play a minimal role in maintaining tidal volume during impeded breathing in roosters. Comparative differences which may explain these results are discussed.

Effect of artificial respiratory volume on the cardiovascular responses to an alpha 1- and an alpha 2-adrenoceptor agonist in the air-ventilated pithed rat.

1. The effect of varying artificial respiratory volume (at a fixed rate of 54 min-1) on cardiac output, its distribution and tissue blood flows were determined with tracer microspheres in control pithed rats or during pressor responses to either the alpha 1-adrenoceptor agonist phenylephrine or the alpha 2-agonist xylazine. Phenylephrine was investigated in the presence of propranolol (3 mg kg-1). The rats were pithed under halothane anaesthesia. 2. A respiratory volume of 15 ml kg-1 produced modest hypercapnia (PaCO2 = 47 mmHg), hypoxia (PaO2 = 60 mmHg) and acidosis (pH = 7.35) relative to control animals respired at 20 ml kg-1 (PaCO2 = 32 mmHg; PaO2 = 77 mmHg; pH = 7.47). In rats respired at 15 ml kg-1, total peripheral resistance was lower, and cardiac output greater (due to increased stroke volume), than in the controls. Lowering respiratory volume reduced distribution of cardiac output to the kidneys, increased it to the large intestine and also increased blood flow through the gastrointestinal tract, skin and spleen. A respiratory volume of 30 ml kg-1 gave mild hypocapnia (PaCO2 = 19 mmHg), hyperoxia (PaO2 = 101 mmHg) and alkalosis (pH = 7.59) compared to 20 ml kg-1 but had no effect on cardiac output distribution or organ blood flow although heart rate was 29% greater at 30 ml kg-1. 3. Xylazine (500 micrograms bolus followed by 100 micrograms min-1 infusion) at all three respiratory volumes gave well-sustained mean pressor responses of 62-64 mmHg by increasing both total peripheral resistance and cardiac output (resulting from increased stroke volume). It increased the proportion of cardiac output passing to the liver, reduced that going to the spleen and gastrointestinal tract and increased cardiac, renal and hepatosplanchnic blood flows. 4. The secondary, relatively sustained, pressor effect of phenylephrine (5 micrograms bolus followed by 0.4 micrograms min-1 infusion, i.v.) varied at the 3 respiratory volumes with mean values from 32 to 53 mmHg. This response was due to both increased total peripheral resistance and cardiac output (resulting from greater stroke volumes and/or heart rates). Phenylephrine increased the proportion of cardiac output passing to the gastrointestinal tract, heart, kidneys and hepatosplanchnic bed and increased cardiac, hepatosplanchnic, renal and gastrointestinal blood flows. 5. Respiratory volume had no effect on the cardiovascular effects of xylazine. However, respiratory volume modified the effects of phenylephrine on heart rate and changed the relative contributions of stroke volume and heart rate to the increased cardiac output. It also influenced the effects of phenylephrine on cardiac output distribution to the liver, epididimides and hepatosplanchnic bed and on blood flow through skeletal muscle and the large intestine. 6. Changes in respiratory volume of air ventilated pithed rats thus influence cardiac output, its distribution and regional blood flows. Such changes can also differently influence the responses of various vascular beds to phenylephrine whilst having no effect on their responses to xylazine.

LUNG DENSITY AS MEASURED BY COMPUTERIZED TOMOGRAPHY

Accurate dose calculations for radiotherapy planning require a detailed knowledge of the internal anatomy of the patient both in terms of geometry and density. Computed tomography (CT) is presently the best means of providing these data. Fifty-eight patients who had scans of the thorax for radiotherapy planning were studied. The CT numbers were converted to relative electron densities and average lung densities were obtained for every patient. A linear correlation of lung density with age was found with the mean lung density of 0.35 at an age 5 years and 0.19 at an age of 80. The effect of scanning the patient under full inspiration, full expiration or normal shallow breathing conditions was analyzed. At the age of 5 years the expiration and inspiration average lung densities were 0.36 and 0.20, while at the age of 80 years they were 0.22 and 0.16, respectively. Respiratory volume changes were linearly correlated with changes in relative electron density. Differences in lung density between expiration and inspiration scans were found to demonstrate a similar trend with age as the relationship between vital capacity and age. The dosimetric and the possible clinical implications of lung density measurements for radiotherapy are considered. In particular, dose calculations were performed using scans taken under a number of different respiratory conditions. Doses calculated for a single cobalt-60 beam can differ by more than 25% when comparing a full inspiration scan to a normal breathing scan. A similar comparison for a parallel pair distribution on the lung yields a difference of about 3% while a typical three field technique for treating cancer of the esophagus shows a difference of nearly 10%.

Lung density as measured by computerized tomography: implications for radiotherapy

Accurate dose calculations for radiotherapy planning require a detailed knowledge of the internal anatomy of the patient both in terms of geometry and density. Computed tomography (CT) is presently the best means of providing these data. Fifty-eight patients who had scans of the thorax for radiotherapy planning were studied. The CT numbers were converted to relative electron densities and average lung densities were obtained for every patient. A linear correlation of lung density with age was found with the mean lung density of 0.35 at an age 5 years and 0.19 at an age of 80. The effect of scanning the patient under full inspiration, full expiration or normal shallow breathing conditions was analyzed. At the age of 5 years the expiration and inspiration average lung densities were 0.36 and 0.20, while at the age of 80 years they were 0.22 and 0.16, respectively. Respiratory volume changes were linearly correlated with changes in relative electron density. Differences in lung density between expiration and inspiration scans were found to demonstrate a similar trend with age as the relationship between vital capacity and age. The dosimetric and the possible clinical implications of lung density measurements for radiotherapy are considered. In particular, dose calculations were performed using scans taken under a number of different respiratory conditions. Doses calculated for a single cobalt-60 beam can differ by more than 25% when comparing a full inspiration scan to a normal breathing scan. A similar comparison for a parallel pair distribution on the lung yields a difference of about 3 % while a typical three field technique for treating cancer of the esophagus shows a difference of nearly 10%.

Efficacy of pattern feedback for the dissociation of heart rate and respiration rate

The present study assessed the efficacy of pattern feedback for producing integrative and dissociative patterns of heart rate (HR) and respiration rate (RR). 60 uninformed subjects were assigned to six groups in which beat-by-beat feedback was contingent upon production of a specific pattern of increased (↑), decreased (↓), or unchanged (=) HR and RR during 11 feedback trials. Concomitant changes in respiratory volume and general activity (GA) were also recorded. Groups given feedback for HR and RR changes in the same directions (HR↑RR↑ and HR↓RR↓) and for changes in opposite directions (HR↑RR↓ and HR↓RR↑) were generally unable to produce the respective patterns, indicating that pattern feedback does not enable subjects to produce a wide range of HR-RR patterns. However, evidence of dissociation of HR and RR was obtained in the HR↑RR= and HR↓RR= groups in which HR changed significantly in the appropriate directions without significant changes in RR. These results are not consistent with the view that RR changes are necessary for HR control, although significant concomitant changes in respiratory volume and GA indicated that HR control was non-specific relative to these variables.

The effects of fentanyl and thiopental on breathing in man.

The effects of anesthetic agents on breathing in man are not well described. In part this reflects the difficulty in obtaining control measurements in awake man, without awareness of the subject that his breathing is being measured. In the present work we report a method for assessing respiratory volume changes in man by measuring body surface displacements. This method has the advantage that since measurements are not made at the mouth, subject awareness (and presumably behavioral alteration) of spontaneous breathing is minimized. An additional advantage of the present work is that continuous measurements of respiratory volume changes can be recorded prior to, during, and subsequent to the induction of general anesthesia. Because of the continuous nature of the measurement we hoped to be able to resolve the controversy concerning changes in functional residual capacity (FRC) and breathing pattern during anesthesia.KeywordsLung VolumeSpontaneous BreathingFunctional Residual CapacityBreathing PatternInspiratory CapacityThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Reflex effects on circulation and respiration from contracting skeletal muscle.

Isometric exercise induced by ventral root stimulation in the anesthetized cat caused heat rate (HR) to increase from 199 +/- 6 beats/min to 206 +/- 6 (P less than 0.001); mean arterial pressure (MAP) from 99 +/- 5.3 mmHg to 112 +/- 5.8 (P less than 0.001); and left ventricular dp/dt at developed pressure of 25 mmHg from 3,960 +/- 204 mmHg/s to 4,380 +/- 220 (P less than 0.001), while end-diastolic pressure remained unchanged. Respiratory volume (RV) increased from 755 +/- 71 ml/min to 1,160 +/- 123 (P less than 0.001). These changes were abolished by cutting the dorsal roots receiving afferents from the exercising muscle. Beta-adrenergic blockade with propranolol (1 mg/kg) abolished the changes in heart rate and contractile state; however, changes in MAP and RV still occurred. Induced isometric exercise causes a small rise in HR with a more marked increase in MAP, the contractile state of the left ventricle and RV. In this preparation the cardiovascular and respiratory changes reflexly originate from contracting skeletal muscle as proven by section of the corresponding dorsal roots, and the cardiovascular changes are mediated in part by activation of beta-adrenergic receptors in the heart.

Respiratory volume-pressure relationships during anaesthesia.

The effect of anaesthesia on respiratory system compliance is not settled. We have studied compliance in subjects awake and then anaesthetized with either halothane or neurolept anaesthesia, both with and without muscle paralysis. A new method of data analysis is also presented. The changes in respiratory volume and pressure are related logarithmically. On the basis of comparison of data in which lung volume is acutely changed during study, the slope of the volume-pressure line is interpreted to represent the elasticity of the system. We found no change in elasticity of the respiratory system resulting from induction of anaesthesia or muscle paralysis. From this we conclude that changes in respiratory compliance during anaesthesia are probably due to the changes in lung volume which are known to occur.

Volume changes and oxygen extraction efficiency in the holothurian, Stichopusmollis (Hutton)

1. 1. Measurements of oxygen consumption and respiratory volume changes were made on the holothurian, Stichopus mollis (Hutton). 2. 2. It is concluded that the external body surface and the respira tory-trees are equally important as sites of oxygen uptake. 3. 3. The oxygen extraction efficiency of the respiratory trees of S. Mollis is estimated at 54 per cent at a temperature of 9°C.

Respiratory Studies in Newborn Infants. II: Pulmonary Ventilation and Mechanics of Breathing in the First Minutes of Life, Including the Onset of Respiratio1

Summary1. Respiratory volume changes and intra‐esophageal pressure changes have been simultaneously recorded beginning before or during the first breaths in 18 infants.2. Respiratory adaptive changes for successful extra‐uterine existence occur rapidly. Some of the features are summarized below.3. The average air exchange in the first 20 seconds after the first breaths is 2–3 times the resting minute volume observed later in the neonatal period.4. A residual volume is established in some infants beginning with the first breath. In others this was not recorded and evidence is presented which suggests it may occur prior to the first breath.5. The total pressure change of the first breath ranged from 40–100 cm O. In succeeding breaths this decreased. Typical pressure‐volume diagrams (“respiratory loops”) are illustrated and their possible significance discussed.6. During the first few breaths the lung compliance was one‐fifth to one‐third and the pulmonary flow resistance 24 times that found in older neonates.