Effects of hypercapnia on Breuer-Hering threshold for inspiratory termination

1984 ◽  
Vol 57 (4) ◽  
pp. 1211-1221 ◽  
Author(s):  
T. L. Clanton ◽  
W. T. Lipscomb
Keyword(s):  
Tidal Volume ◽  
Lung Volume ◽  
Neural Mechanism ◽  
Co2 Concentration ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Fractional Concentration ◽  
Residual Capacity ◽  
Upward Direction ◽  
Breath Cycle

The effects of CO2 concentration on the timing of inspiratory duration (TI) and expiratory duration (TE) and the responses to lung inflation were studied in decerebrate paralyzed cats. With lung volume held at functional residual capacity during the breath cycle, hypercapnia (fractional concentration of inspired CO2 = 0.04) caused variable changes in TI and significant increases in TE. To obtain the Breuer-Hering threshold relationship [tidal volume (VT) vs. TI] and the timing relationship between TE and the preceding TI (TE vs. TI), ramp inflations of various sizes were used to terminate inspiration at different times in the breath cycle. Hypercapnia caused the VT vs. TI curves to shift in an upward direction so that at higher lung volumes TI was lengthened. Also, the slope of the TE vs. TI relationship was increased. The results suggest that hypercapnia diminished the sensitivity of the Breuer-Hering reflex to the lung volume, thus allowing volume to increase with little effect on TI. In addition, TE appears to become more sensitive to changes in the preceding TI. A model is presented which provides a possible neural mechanism for these responses.

scholarly journals Assessment of the influence of lung inflation state on the quantitative parameters derived from hyperpolarized gas lung ventilation MRI in healthy volunteers

2019 ◽  
Vol 126 (1) ◽  
pp. 183-192 ◽  
Author(s):  
Paul J. C. Hughes ◽  
Laurie Smith ◽  
Ho-Fung Chan ◽  
Bilal A. Tahir ◽  
Graham Norquay ◽  
...  
Keyword(s):  
Healthy Volunteers ◽  
Lung Volume ◽  
Lung Ventilation ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Longitudinal Measurements ◽  
Anatomical Images ◽  
Lower Lung ◽  
Ventilation Heterogeneity ◽  
Residual Capacity

In this study, the effect of lung volume on quantitative measures of lung ventilation was investigated using MRI with hyperpolarized 3He and 129Xe. Six volunteers were imaged with hyperpolarized 3He at five different lung volumes [residual volume (RV), RV + 1 liter (1L), functional residual capacity (FRC), FRC + 1L, and total lung capacity (TLC)], and three were also imaged with hyperpolarized 129Xe. Imaging at each of the lung volumes was repeated twice on the same day with corresponding 1H lung anatomical images. Percent lung ventilated volume (%VV) and variation of signal intensity [heterogeneity score (Hscore)] were evaluated. Increased ventilation heterogeneity, quantified by reduced %VV and increased Hscore, was observed at lower lung volumes with the least ventilation heterogeneity observed at TLC. For 3He MRI data, the coefficient of variation of %VV was <1.5% and <5.5% for Hscore at all lung volumes, while for 129Xe data the values were 4 and 10%, respectively. Generally, %VV generated from 129Xe images was lower than that seen from 3He images. The good repeatability of 3He %VV found here supports prior publications showing that percent lung-ventilated volume is a robust method for assessing global lung ventilation. The greater ventilation heterogeneity observed at lower lung volumes indicates that there may be partial airway closure in healthy lungs and that lung volume should be carefully considered for reliable longitudinal measurements of %VV and Hscore. The results suggest that imaging patients at different lung volumes may help to elucidate obstructive disease pathophysiology and progression. NEW & NOTEWORTHY We present repeatability data of quantitative metrics of lung function derived from hyperpolarized helium-3, xenon-129, and proton anatomical images acquired at five lung volumes in volunteers. Increased regional ventilation heterogeneity at lower lung inflation levels was observed in the lungs of healthy volunteers.

Methacholine-induced bronchoconstriction in dogs: effects of lung volume and O3 exposure

1988 ◽  
Vol 65 (6) ◽  
pp. 2679-2686 ◽  
Author(s):  
S. T. Kariya ◽  
S. A. Shore ◽  
W. A. Skornik ◽  
K. Anderson ◽  
R. H. Ingram ◽  
...  
Keyword(s):  
Lung Volume ◽  
Maximal Response ◽  
Maximal Effect ◽  
Response Curves ◽  
Lung Volumes ◽  
Before And After ◽  
Residual Capacity ◽  
Induced Changes ◽  
Conducting Airways ◽  
Concentration Response Curve

The maximal effect induced by methacholine (MCh) aerosols on pulmonary resistance (RL), and the effects of altering lung volume and O3 exposure on these induced changes in RL, was studied in five anesthetized and paralyzed dogs. RL was measured at functional residual capacity (FRC), and lung volumes above and below FRC, after exposure to MCh aerosols generated from solutions of 0.1-300 mg MCh/ml. The relative site of response was examined by magnifying parenchymal [RL with large tidal volume (VT) at fast frequency (RLLS)] or airway effects [RL with small VT at fast frequency (RLSF)]. Measurements were performed on dogs before and after 2 h of exposure to 3 ppm O3. MCh concentration-response curves for both RLLS and RLSF were sigmoid shaped. Alterations in mean lung volume did not alter RLLS; however, RLSF was larger below FRC than at higher lung volumes. Although O3 exposure resulted in small leftward shifts of the concentration-response curve for RLLS, the airway dominated index of RL (RLSF) was not altered by O3 exposure, nor was the maximal response using either index of RL. These data suggest O3 exposure does not affect MCh responses in conducting airways; rather, it affects responses of peripheral contractile elements to MCh, without changing their maximal response.

Relationship of end-expiratory pressure, lung volume, and 99mTc-DTPA clearance

1987 ◽  
Vol 63 (4) ◽  
pp. 1586-1590 ◽  
Author(s):  
J. A. Cooper ◽  
H. van der Zee ◽  
B. R. Line ◽  
A. B. Malik
Keyword(s):  
Lung Volume ◽  
Clearance Rate ◽  
Base Line ◽  
Lung Inflation ◽  
Alveolar Epithelial ◽  
Pulmonary Clearance ◽  
Residual Capacity ◽  
Dose Response Effect ◽  
Relationship Of ◽  
Line P

We investigated the dose-response effect of positive end-expiratory pressure (PEEP) and increased lung volume on the pulmonary clearance rate of aerosolized technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA). Clearance of lung radioactivity was expressed as percent decrease per minute. Base-line clearance was measured while anesthetized sheep (n = 20) were ventilated with 0 cmH2O end-expiratory pressure. Clearance was remeasured during ventilation at 2.5, 5, 10, 15, or 20 cmH2O PEEP. Further studies showed stepwise increases in functional residual capacity (FRC) (P less than 0.05) measured at 0, 2.5, 5, 10, 15, and 20 cmH2O PEEP. At 2.5 cmH2O PEEP, the clearance rate was not different from that at base line (P less than 0.05), although FRC was increased from base line. Clearance rate increased progressively with increasing PEEP at 5, 10, and 15 cmH2O (P less than 0.05). Between 15 and 20 cmH2O PEEP, clearance rate was again unchanged, despite an increase in FRC. The pulmonary clearance of aerosolized 99mTc-DTPA shows a sigmoidal response to increasing FRC and PEEP, having both threshold and maximal effects. This relationship is most consistent with the hypothesis that alveolar epithelial permeability is increased by lung inflation.

STUDIES OF RESPIRATORY PHYSIOLOGY IN CHILDREN

PEDIATRICS ◽  
1959 ◽  
Vol 24 (2) ◽  
pp. 181-193
Author(s):  
C. D. Cook ◽  
P. J. Helliesen ◽  
L. Kulczycki ◽  
H. Barrie ◽  
L. Friedlander ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Respiratory Rate ◽  
Vital Capacity ◽  
Total Lung Capacity ◽  
Lung Compliance ◽  
Respiratory Physiology ◽  
Residual Volume ◽  
Lung Volumes ◽  
Lung Capacity ◽  
Residual Capacity

Tidal volume, respiratory rate and lung volumes have been measured in 64 patients with cystic fibrosis of the pancreas while lung compliance and resistance were measured in 42 of these. Serial studies of lung volumes were done in 43. Tidal volume was reduced and the respiratory rate increased only in the most severely ill patients. Excluding the three patients with lobectomies, residual volume and functional residual capacity were found to be significantly increased in 46 and 21%, respectively. These changes correlated well with the roentgenographic evaluation of emphysema. Vital capacity was significantly reduced in 34% while total lung capacity was, on the average, relatively unchanged. Seventy per cent of the 61 patients had a signficantly elevated RV/TLC ratio. Lung compliance was significantly reduced in only the most severely ill patients but resistance was significantly increased in 35% of the patients studied. The serial studies of lung volumes showed no consistent trends among the groups of patients in the period between studies. However, 10% of the surviving patients showed evidence of significant improvement while 15% deteriorated. [See Fig. 8. in Source Pdf.] Although there were individual discrepancies, there was a definite correlation between the clinical evaluation and tests of respiratory function, especially the changes in residual volume, the vital capacity, RV/ TLC ratio and the lung compliance and resistance.

Expiratory muscle contribution to tidal volume in head-up dogs

1989 ◽  
Vol 67 (4) ◽  
pp. 1438-1442 ◽  
Author(s):  
G. A. Farkas ◽  
M. Estenne ◽  
A. De Troyer
Keyword(s):  
Tidal Volume ◽  
Lung Volume ◽  
Muscle Relaxation ◽  
Rib Cage ◽  
Expiratory Muscle ◽  
Residual Capacity ◽  
Anesthetized Dogs ◽  
Expiratory Muscles ◽  
S Period ◽  
Average Contribution

A change from the supine to the head-up posture in anesthetized dogs elicits increased phasic expiratory activation of the rib cage and abdominal expiratory muscles. However, when this postural change is produced over a 4- to 5-s period, there is an initial apnea during which all the muscles are silent. In the present studies, we have taken advantage of this initial silence to determine functional residual capacity (FRC) and measure the subsequent change in end-expiratory lung volume. Eight animals were studied, and in all of them end-expiratory lung volume in the head-up posture decreased relative to FRC [329 +/- 70 (SE) ml]. Because this decrease also represents the increase in lung volume as a result of expiratory muscle relaxation at the end of the expiratory pause, it can be used to determine the expiratory muscle contribution to tidal volume (VT). The average contribution was 62 +/- 6% VT. After denervation of the rib cage expiratory muscles, the reduction in end-expiratory lung volume still amounted to 273 +/- 84 ml (49 +/- 10% VT). Thus, in head-up dogs, about two-thirds of VT result from the action of the expiratory muscles, and most of it (83%) is due to the action of the abdominal rather than the rib cage expiratory muscles.

High lung volume increases stress failure in pulmonary capillaries

1992 ◽  
Vol 73 (1) ◽  
pp. 123-133 ◽  
Author(s):  
Z. Fu ◽  
M. L. Costello ◽  
K. Tsukimoto ◽  
R. Prediletto ◽  
A. R. Elliott ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Lung Volume ◽  
Autologous Blood ◽  
Physiological Mechanism ◽  
Transpulmonary Pressure ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Pulmonary Capillaries ◽  
Scanning Electron

We previously showed that when pulmonary capillaries in anesthetized rabbits are exposed to a transmural pressure (Ptm) of approximately 40 mmHg, stress failure of the walls occurs with disruption of the capillary endothelium, alveolar epithelium, or sometimes all layers. The present study was designed to test whether stress failure occurred more frequently at high than at low lung volumes for the same Ptm. Lungs of anesthetized rabbits were inflated to a transpulmonary pressure of 20 cmH2O, perfused with autologous blood at 32.5 or 2.5 cmH2O Ptm, and fixed by intravascular perfusion. Samples were examined by both transmission and scanning electron microscopy. The results were compared with those of a previous study in which the lung was inflated to a transpulmonary pressure of 5 cmH2O. There was a large increase in the frequency of stress failure of the capillary walls at the higher lung volume. For example, at 32.5 cmH2O Ptm, the number of endothelial breaks per millimeter cell lining was 7.1 +/- 2.2 at the high lung volume compared with 0.7 +/- 0.4 at the low lung volume. The corresponding values for epithelium were 8.5 +/- 1.6 and 0.9 +/- 0.6. Both differences were significant (P less than 0.05). At 52.5 cmH2O Ptm, the results for endothelium were 20.7 +/- 7.6 (high volume) and 7.1 +/- 2.1 (low volume), and the corresponding results for epithelium were 32.8 +/- 11.9 and 11.4 +/- 3.7. At 32.5 cmH2O Ptm, the thickness of the blood-gas barrier was greater at the higher lung volume, consistent with the development of more interstitial edema. Ballooning of the epithelium caused by accumulation of edema fluid between the epithelial cell and its basement membrane was seen at 32.5 and 52.5 cmH2O Ptm. At high lung volume, the breaks tended to be narrower and fewer were oriented perpendicular to the axis of the pulmonary capillaries than at low lung volumes. Transmission and scanning electron microscopy measurements agreed well. Our findings provide a physiological mechanism for other studies showing increased capillary permeability at high states of lung inflation.

scholarly journals Lung elastic recoil during breathing at increased lung volume

1999 ◽  
Vol 87 (4) ◽  
pp. 1491-1495 ◽  
Author(s):  
Joseph R. Rodarte ◽  
Gassan Noredin ◽  
Charles Miller ◽  
Vito Brusasco ◽  
Riccardo Pellegrino ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Tidal Volume ◽  
Lung Volume ◽  
Normal Subjects ◽  
Dynamic Hyperinflation ◽  
Airway Closure ◽  
Elastic Recoil ◽  
Volume Increase ◽  
Before And After ◽  
Residual Capacity

During dynamic hyperinflation with induced bronchoconstriction, there is a reduction in lung elastic recoil at constant lung volume (R. Pellegrino, O. Wilson, G. Jenouri, and J. R. Rodarte. J. Appl. Physiol. 81: 964–975, 1996). In the present study, lung elastic recoil at control end inspiration was measured in normal subjects in a volume displacement plethysmograph before and after voluntary increases in mean lung volume, which were achieved by one tidal volume increase in functional residual capacity (FRC) with constant tidal volume and by doubling tidal volume with constant FRC. Lung elastic recoil at control end inspiration was significantly decreased by ∼10% within four breaths of increasing FRC. When tidal volume was doubled, the decrease in computed lung recoil at control end inspiration was not significant. Because voluntary increases of lung volume should not produce airway closure, we conclude that stress relaxation was responsible for the decrease in lung recoil.

Gravity effects on upper airway area and lung volumes during parabolic flight

1998 ◽  
Vol 84 (5) ◽  
pp. 1639-1645 ◽  
Author(s):  
Maurice Beaumont ◽  
Redouane Fodil ◽  
Daniel Isabey ◽  
Frédéric Lofaso ◽  
Dominique Touchard ◽  
...  
Keyword(s):  
Lung Volume ◽  
Parabolic Flight ◽  
Upper Airway ◽  
Normal Subjects ◽  
Lung Volumes ◽  
Acoustic Reflection ◽  
Volume Functional ◽  
Airway Caliber ◽  
Gravity Effects ◽  
Residual Capacity

We measured upper airway caliber and lung volumes in six normal subjects in the sitting and supine positions during 20-s periods in normogravity, hypergravity [1.8 + head-to-foot acceleration (Gz)], and microgravity (∼0 Gz) induced by parabolic flights. Airway caliber and lung volumes were inferred by the acoustic reflection method and inductance plethysmography, respectively. In subjects in the sitting position, an increase in gravity from 0 to 1.8 +Gz was associated with increases in the calibers of the retrobasitongue and palatopharyngeal regions (+20 and +30%, respectively) and with a concomitant 0.5-liter increase in end-expiratory lung volume (functional residual capacity, FRC). In subjects in the supine position, no changes in the areas of these regions were observed, despite significant decreases in FRC from microgravity to normogravity (−0.6 liter) and from microgravity to hypergravity (−0.5 liter). Laryngeal narrowing also occurred in both positions (about −15%) when gravity increased from 0 to 1.8 +Gz. We concluded that variation in lung volume is insufficient to explain all upper airway caliber variation but that direct gravity effects on tissues surrounding the upper airway should be taken into account.

Measurement of high lung volumes by nitrogen washout method

1994 ◽  
Vol 77 (3) ◽  
pp. 1562-1564 ◽  
Author(s):  
Y. Sivan ◽  
J. Hammer ◽  
C. J. Newth
Keyword(s):  
Lung Volume ◽  
Human Infants ◽  
Lung Volumes ◽  
Nitrogen Washout ◽  
Thoracic Gas Volume ◽  
Residual Capacity ◽  
The Difference ◽  
Gas Dilution ◽  
Spontaneously Breathing ◽  
Gas Volume

Studies on human infants suggested that thoracic gas volume (TGV) measured at end exhalation may not depict the true TGV and may differ from TGV measured from a series of higher lung volumes and corrected for the volume added. This was explained by gas trapping. If true, we should expect the discrepancy to be more pronounced when functional residual capacity (FRC) and higher lung volumes are measured by gas dilution techniques. We studied lung volumes above FRC by the nitrogen washout technique in 12 spontaneously breathing rhesus monkeys (5.0–11.3 kg wt; 42 compared measurements). Lung volumes directly measured were compared with preset lung volumes achieved by artificial inflation of the lungs above FRC with known volumes of air (100–260 ml). Measured lung volume strongly correlated with and was not significantly different from present lung volume (P = 0.05; r = 0.996). The difference between measured and preset lung volume was 0–5% in 41 of 42 cases [1 +/- 0.4% (SE)]. The direction of the difference was unpredictable; in 22 of 42 cases the measured volume was larger than the preset volume, but in 17 of 42 cases it was smaller. The difference was not affected by the volume of gas artificially inflated into the lungs. We conclude that, overall, lung volumes above FRC can be reliably measured by the nitrogen washout technique and that FRC measurements by this method reasonably reflect true FRC.

Effect of lung volume on forced expiratory flows during rapid thoracoabdominal compression in infants

1995 ◽  
Vol 78 (5) ◽  
pp. 1993-1997 ◽  
Author(s):  
J. Hammer ◽  
C. J. Newth
Keyword(s):  
Lung Volume ◽  
Vital Capacity ◽  
Forced Expiration ◽  
Flow Volume ◽  
Older Children ◽  
Lung Volumes ◽  
Volume Segment ◽  
Forced Expiratory Flow ◽  
Residual Capacity ◽  
End Tidal

The rapid thoracoabdominal compression (RTC) technique is commonly used in pulmonary function laboratories to assess flow-volume relationships in infants unable to produce a voluntary forced expiration maneuver. This technique produces forced expiratory flows over only a small lung volume segment (i.e., tidal volume). It has been argued that the RTC technique should be modified to measure flow-volume relationships over a larger portion of the vital capacity range to imitate the voluntary maximal forced expiratory maneuver obtained in older children and adults. We examined the effect of volume history on forced expiratory flows by generating forced expiratory flow-volume curves by RTC from well-defined inspiratory volumes delineated by inspiratory pressures of 10, 20, 30, and 40 cmH2O down to residual volume (i.e., the reference volume) in seven intubated and anesthetized infants with normal lungs [age 8.0 +/- 2.0 (SE) mo, weight 6.7 +/- 0.6 kg]. We compared maximal expiratory flows at isovolume points (25 and 10% of forced vital capacity) and found no significant differences in maximal isovolume flow rates measured from the different lung volumes. We conclude that there is no obvious need to initiate RTC from higher lung volumes if the technique is used for flow comparisons. However, compared with measurements of maximal flows at functional residual capacity by RTC from end-tidal inspiration, the initiation of RTC from a defined and reproducible inspiratory level appears to decrease the intrasubject variability of the maximal expiratory flows at low lung volumes.

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