Tracking variations in airway caliber by using total respiratory vs. airway resistance in healthy and asthmatic subjects

2003 ◽  
Vol 95 (2) ◽  
pp. 511-518 ◽  
Author(s):  
L. D. Black ◽  
R. Dellacà ◽  
K. Jung ◽  
H. Atileh ◽  
E. Israel ◽  
...  
Keyword(s):  
Chest Wall ◽  
Airway Resistance ◽  
Total Lung Capacity ◽  
Recursive Least Squares ◽  
Effective Diameter ◽  
Tidal Breathing ◽  
Lung Capacity ◽  
Airway Caliber ◽  
Esophageal Balloon ◽  
Airway Opening

An index of airway caliber can be tracked in near-real time by measuring airway resistance (Raw) as indicated by lung resistance at 8 Hz. These measurements require the placing of an esophageal balloon. The objective of this study was to establish whether total respiratory system resistance (Rrs) could be used rather than Raw to track airway caliber, thereby not requiring an esophageal balloon. Rrs includes the resistance of the chest wall (Rcw). We used a recursive least squares approach to track Raw and Rrs at 8 Hz in seven healthy and seven asthmatic subjects during tidal breathing and a deep inspiration (DI). In both subject groups, Rrs was significantly higher than Raw during tidal breathing at baseline and postchallenge. However, at total lung capacity, Raw and Rrs became equivalent. Measured with this approach, Rcw appears volume dependent, having a magnitude of 0.5–1.0 cmH2O · l-1 · s during tidal breathing and decreasing to zero at total lung capacity. When resistances are converted to an effective diameter, Rrs data overestimate the increase in diameter during a DI. Simulation studies suggest that the decrease in apparent Rcw during a DI is a consequence of airway opening flow underestimating chest wall flow at increased lung volume. We conclude that the volume dependence of Rcw can bias the presumed net change in airway caliber during tidal breathing and a DI but would not distort assessment of maximum airway dilation.

Abdominal distension alters regional pleural pressures and chest wall mechanics in pigs in vivo

1991 ◽  
Vol 70 (6) ◽  
pp. 2611-2618 ◽  
Author(s):  
T. Mutoh ◽  
W. J. Lamm ◽  
L. J. Embree ◽  
J. Hildebrandt ◽  
R. K. Albert
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Functional Residual Capacity ◽  
Total Lung Capacity ◽  
Abdominal Cavity ◽  
Abdominal Distension ◽  
Abdominal Pressure ◽  
Lung Capacity ◽  
Lung Expansion ◽  
Residual Capacity

Abdominal distension (AD) occurs in pregnancy and is also commonly seen in patients with ascites from various causes. Because the abdomen forms part of the "chest wall," the purpose of this study was to clarify the effects of AD on ventilatory mechanics. Airway pressure, four (vertical) regional pleural pressures, and abdominal pressure were measured in five anesthetized, paralyzed, and ventilated upright pigs. The effects of AD on the lung and chest wall were studied by inflating a liquid-filled balloon placed in the abdominal cavity. Respiratory system, chest wall, and lung pressure-volume (PV) relationships were measured on deflation from total lung capacity to residual volume, as well as in the tidal breathing range, before and 15 min after abdominal pressure was raised. Increasing abdominal pressure from 3 to 15 cmH2O decreased total lung capacity and functional residual capacity by approximately 40% and shifted the respiratory system and chest wall PV curves downward and to the right. Much smaller downward shifts in lung deflation curves were seen, with no change in the transdiaphragmatic PV relationship. All regional pleural pressures increased (became less negative) and, in the dependent region, approached 0 cmH2O at functional residual capacity. Tidal compliances of the respiratory system, chest wall, and lung were decreased 43, 42, and 48%, respectively. AD markedly alters respiratory system mechanics primarily by "stiffening" the diaphragm/abdomen part of the chest wall and secondarily by restricting lung expansion, thus shifting the lung PV curve as seen after chest strapping. The less negative pleural pressures in the dependent lung regions suggest that nonuniformities of ventilation could also be accentuated and gas exchange impaired by AD.

Effect of intrathoracic pressure on pressure-volume characteristics of the lung in man

1975 ◽  
Vol 38 (3) ◽  
pp. 411-417 ◽  
Author(s):  
H. S. Goldberg ◽  
W. Mitzner ◽  
K. Adams ◽  
H. Menkes ◽  
S. Lichtenstein ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Total Lung Capacity ◽  
Human Subjects ◽  
Ambient Pressure ◽  
Intrathoracic Pressure ◽  
Dynamic Compliance ◽  
Positive Pressure ◽  
Lung Capacity ◽  
Airway Opening ◽  
Volume Characteristics

Quasi-static pressure-volume (P-V) curves in normal seated human subjects were determined with pressure at the airway opening (Pa0) set below (negative pressure), above (positive pressure), or equal to ambient pressure. Dynamic compliance (Cdyn) during controlled continuous negative pressure breathing (CNPB) was also studied. Quasi-static P-V curves at negative pressure were decreased in slope, reflected a decrease in total lung capacity, and intersected the P-V curve obtained at ambient Pa0. At positive pressure the P-V curves showed an increase in slope and an increase in total lung capacity. During CNPB a fall in Cdyn was found. The fall in Cdyn was rapid and persisted for the duration of CNPB. Cdyn promptly returned to control levels when Pa0 was adjusted to ambient pressure.

Interaction of inhaled LTC4 with histamine and PGD2 on airway caliber in asthma

1989 ◽  
Vol 66 (1) ◽  
pp. 304-312 ◽  
Author(s):  
G. D. Phillips ◽  
S. T. Holgate
Keyword(s):  
Time Course ◽  
Vital Capacity ◽  
Total Lung Capacity ◽  
Forced Expiratory Volume ◽  
Maximal Flow ◽  
Lung Capacity ◽  
Airway Caliber ◽  
Relevant Interaction

To investigate possible mediator interaction in asthma, the effect of inhaled leukotriene (LT) C4 on bronchoconstriction provoked by histamine and prostaglandin (PG) D2 was studied in nine asthmatic subjects. The provocation doses of histamine, PGD2, and LTC4 required to produce a 12.5% decrease in baseline forced expiratory volume in 1 s (FEV1, PD12.5) and to further this fall to 25% (PD25–12.5) were determined. On three subsequent occasions, subjects inhaled either the PD12.5 LTC4 plus vehicle or vehicle plus the PD25–12.5 of either histamine or PGD2, and FEV1 and maximal flow at 70% of vital capacity below total lung capacity after a forced partial expiratory maneuver (Vp30) followed for 45 min. From these results, predicted time-course curves for LTC4 with histamine and LTC4 with PGD2 were calculated. On two final occasions, airway caliber was followed for 45 min after inhalation of the PD12.5 LTC4 followed by the PD25–12.5 of either histamine or PGD2. During the first 9 min after LTC4-histamine and LTC4-PGD2, the decreases in airway caliber were greater than the calculated predicted response. This interaction, although small, was significant with LTC4-PGD2 for both FEV1 (P = 0.01) and Vp30 (P less than 0.05) and with LTC4-histamine for Vp30 (P less than 0.05) but not for FEV1 (P less than 0.05). We conclude that inhaled LTC4 interacts synergistically with histamine and PGD2 and that this effect, although small, may be a relevant interaction in asthma.

Selected Contribution: Airway caliber in healthy and asthmatic subjects: effects of bronchial challenge and deep inspirations

2001 ◽  
Vol 91 (1) ◽  
pp. 506-515 ◽  
Author(s):  
Andrew Jensen ◽  
Haytham Atileh ◽  
Bela Suki ◽  
Edward P. Ingenito ◽  
Kenneth R. Lutchen
Keyword(s):  
Smooth Muscle ◽  
Healthy Subjects ◽  
Tidal Breathing ◽  
Bronchial Challenge ◽  
Lung Capacity ◽  
Single Breath ◽  
Airway Caliber ◽  
Lung Resistance ◽  
Before And After ◽  
Biological State

In 9 healthy and 14 asthmatic subjects before and after a standard bronchial challenge and a modified [deep inspiration (DI), inhibited] bronchial challenge and after albuterol, we tracked airway caliber by synthesizing a method to measure airway resistance (Raw; i.e., lung resistance at 8 Hz) in real time. We determined the minimum Raw achievable during a DI to total lung capacity and the subsequent dynamics of Raw after exhalation and resumption of tidal breathing. Results showed that even after a bronchial challenge healthy subjects can dilate airways maximally, and the dilation caused by a single DI takes several breaths to return to baseline. In contrast, at baseline, asthmatic subjects cannot maximally dilate their airways, and this worsens considerably postconstriction. Moreover, after a DI, the dilation that does occur in airway caliber in asthmatic subjects constricts back to baseline much faster (often after a single breath). After albuterol, asthmatic subjects could dilate airways much closer to levels of those of healthy subjects. These data suggest that the asthmatic smooth muscle resides in a stiffer biological state compared with the stimulated healthy smooth muscle, and inhibiting a DI in healthy subjects cannot mimic this.

Crural diaphragm activation during dynamic contractions at various inspiratory flow rates

1998 ◽  
Vol 85 (2) ◽  
pp. 451-458 ◽  
Author(s):  
Jennifer Beck ◽  
Christer Sinderby ◽  
Lars Lindström ◽  
Alex Grassino
Keyword(s):  
Chest Wall ◽  
Functional Residual Capacity ◽  
Healthy Subjects ◽  
Total Lung Capacity ◽  
Inspiratory Flow ◽  
Transdiaphragmatic Pressure ◽  
Flow Rates ◽  
Lung Capacity ◽  
Dynamic Contractions ◽  
Residual Capacity

The purpose of this study was to evaluate the influence of velocity of shortening on the relationship between diaphragm activation and pressure generation in humans. This was achieved by relating the root mean square (RMS) of the diaphragm electromyogram to the transdiaphragmatic pressure (Pdi) generated during dynamic contractions at different inspiratory flow rates. Five healthy subjects inspired from functional residual capacity to total lung capacity at different flow rates while reproducing identical Pdi and chest wall configuration profiles. To change the inspiratory flow rate, subjects performed the inspirations while breathing across two different inspiratory resistances (10 and 100 cmH2O ⋅ l−1 ⋅ s), at mouth pressure targets of −10, −20, −40, and −60 cmH2O. The diaphragm electromyogram was recorded and analyzed with control of signal contamination and electrode positioning. RMS values obtained for inspirations with identical Pdi and chest wall configuration profiles were compared at the same percentage of inspiratory duration. At inspiratory flows ranging between 0.1 and 1.4 l/s, there was no difference in the RMS for the inspirations from functional residual capacity to total lung capacity when Pdi and chest wall configuration profiles were reproduced ( n = 4). At higher inspiratory flow rates, subjects were not able to reproduce their chest wall displacements and adopted different recruitment patterns. In conclusion, there was no evidence for increased demand of diaphragm activation when healthy subjects breathe with similar chest wall configuration and Pdi profiles, at increasing flow rates up to 1.4 l/s.

Respiratory mechanics of a small carnivore: the ferret

1982 ◽  
Vol 52 (4) ◽  
pp. 832-837 ◽  
Author(s):  
A. Vinegar ◽  
E. E. Sinnett ◽  
P. C. Kosch
Keyword(s):  
Total Lung Capacity ◽  
Lung Compliance ◽  
Pulmonary Resistance ◽  
Mustela Putorius ◽  
Tidal Breathing ◽  
Lung Capacity ◽  
Maximum Expiratory Flow ◽  
Residual Capacity ◽  
Dynamic Lung Compliance

The ferret, Mustela putorius furo, is a small relatively inexpensive carnivore with minimal housing requirements. Measurements were made from anesthetized tracheotomized supine males. Values obtained during tidal breathing for six animals (576 +/- 12 g) were as follows: tidal volume, 6.06 +/- 0.30 ml; respiratory frequency, 26.7 +/- 3.9 breaths min-1; dynamic lung compliance, 2.48 +/- 0.21 ml cmH2O-1; pulmonary resistance, 22.56 +/- 1.61 cmH2O . l–1 . s. Pressure-volume curves from nine ferrets revealed almost infinitely compliant chest walls so that lung and total respiratory system curves were essentially the same. Total lung capacity (TLC, 89 +/- 5 ml) and functional residual capacity (17.8 +/- 2.0 ml) were determined by gas freeing the lungs in vivo. The TLC of these ferrets is about the same as in 2.5-kg rabbits. Maximum expiratory flow-volume curves showed peak flows of 10.1 vital capacities (VC) . s-1 at 75% VC and flows of 8.4 and 5.4 VC . s-1 at 50 and 25% VC.

Chest wall configuration assessed at total lung capacity during acute asthma and after recovery

Lung ◽  
1993 ◽  
Vol 171 (5) ◽  
pp. 53-57
Author(s):  
Sung S. Park ◽  
Lawrence Stein ◽  
Melvin N. Zelefsky
Keyword(s):  
Chest Wall ◽  
Total Lung Capacity ◽  
Acute Asthma ◽  
Lung Capacity

Effects of chest wall on volume and strain patterns in canine lungs

1985 ◽  
Vol 58 (4) ◽  
pp. 1055-1060
Author(s):  
W. S. Krell ◽  
J. R. Rodarte
Keyword(s):  
Chest Wall ◽  
Total Lung Capacity ◽  
Shape Change ◽  
Lower Lobe ◽  
Volume Distribution ◽  
Lung Capacity ◽  
Residual Capacity ◽  
Anesthetized Dogs ◽  
Cartesian Coordinate ◽  
Wall Interactions

Lobar functional residual capacity-to-total lung capacity ratios (FRC/TLC) and strains in five supine anesthetized dogs were determined from volumes and side lengths of tetrahedra formed by multiple intraparenchymal markers whose positions were determined roentgenographically. Strain is related to fractional changes in length of elements in a Cartesian coordinate system and was used to describe parenchymal distortion. Volumes and strain patterns were compared in three states: intact dogs, after transection of forelimb structures to relieve traction on the chest wall, and in dogs' excised lungs. Removing traction (NT) decreased the plethysmographically determined FRC and the upper-to-lower lobe ratio (UL/LL) for FRC/TLC. The ratio in the NT state was more like the ratio in the excised lungs (UL/LL approximately equal to 1) than in the intact dog (UL/LL greater than 1). Strain patterns were similar between the intact and the NT states, indicating no lobar shape change at FRC between these two states. Strain in the excised lungs differed greatly from strains in the intact and NT states. We conclude that forelimb traction alters volume distribution between lobes and that lung-chest wall interactions are important in determining volume and strain patterns.

Airway distensibility in healthy and asthmatic subjects: effect of lung volume history

2000 ◽  
Vol 88 (4) ◽  
pp. 1413-1420 ◽  
Author(s):  
David Peter Johns ◽  
John Wilson ◽  
Richard Harding ◽  
E. Haydn Walters
Keyword(s):  
Lung Volume ◽  
Total Lung Capacity ◽  
Normal Subjects ◽  
Residual Volume ◽  
Tidal Breathing ◽  
Lung Capacity ◽  
Mild Asthmatic ◽  
The Relationship ◽  
Asthmatic Group ◽  
Volume History

Anatomic dead space (Vd) is known to increase with end-inspiratory lung volume (EILV), and the gradient of the relationship has been proposed as an index of airway distensibility (ΔVd). The aims of this study were to apply a rapid method for measuring ΔVd and to determine whether it was affected by lung volume history. Vd of 16 healthy and 16 mildly asthmatic subjects was measured at a number of known EILVs by using a tidal breathing, CO2-washout method. The effect of lung volume history was assessed by using three tidal breathing regimens: 1) three discrete EILVs (low/medium/high; LMH); 2) progressively decreasing EILVs from total lung capacity (TLC; TLC-RV); and 3) progressively increasing EILVs from residual volume (RV; RV-TLC). ΔVd was lower in the asthmatic group for the LMH (25.3 ± 2.24 vs. 21.2 ± 1.66 ml/l, means ± SE) and TLC-RV (24.3 ± 1.69 vs. 18.7 ± 1.16 ml/l) regimens. There was a trend for a lower ΔVd in the asthmatic group for the RV-TLC regimen (23.3 ± 2.19 vs. 18.8 ± 1.68 ml/l). There was no difference in ΔVd between groups. In conclusion, mild asthmatic subjects have stiffer airways than normal subjects, and this is not obviously affected by lung volume history.

Airway response to deep inspiration: role of inflation pressure

2001 ◽  
Vol 91 (6) ◽  
pp. 2574-2578 ◽  
Author(s):  
Robert H. Brown ◽  
Wayne Mitzner
Keyword(s):  
Healthy Subjects ◽  
Total Lung Capacity ◽  
Qualitative Change ◽  
Intrinsic Properties ◽  
High Resolution Computed Tomography ◽  
Lung Inflation ◽  
Lung Capacity ◽  
Airway Caliber ◽  
Airway Response

Deep inspirations (DIs) have been shown to have both bronchoprotective and bronchodilator effects in healthy subjects; however, the bronchodilator effects of a DI appear to be impaired in asthmatic compared with healthy subjects. Because the ability to generate high transpulmonary pressures at total lung capacity depends on both the lung properties and voluntary effort, we wondered how the response of airways to DI might be altered if the maneuver were done with less than maximal inflation. The present work was undertaken to examine the effects of varying the magnitude of lung inflation during the DI maneuver on subsequent airway caliber. In five anesthetized and ventilated dogs during methacholine infusion, changes in airway size after DIs of increasing magnitude were measured over the subsequent 5-min period using high-resolution computed tomography. Results show that the magnitude of lung inflation is extremely important, leading to a qualitative change in the airway response. A large DI (45 cmH2O airway pressure) caused subsequent airway dilation, whereas smaller DIs (≤35 cmH2O) caused bronchoconstriction. The precise mechanism underlying these observations is uncertain, but it seems to be related to an interaction between intrinsic properties of the contracted airway smooth muscle and the response to mild stretch.

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