Modification of pulmonary gas mixing by postural changes

1986 ◽  
Vol 61 (1) ◽  
pp. 75-80 ◽  
Author(s):  
H. A. Jones ◽  
E. E. Davies ◽  
J. M. Hughes
Keyword(s):  
Lung Volume ◽  
Sulfur Hexafluoride ◽  
Normal Subjects ◽  
Gas Mixing ◽  
Supine Posture ◽  
Dependent Change ◽  
Postural Changes ◽  
Residual Capacity ◽  
Lateral Decubitus ◽  
The Mean

Mixing for two gases of markedly different gaseous diffusivity, helium (He) (mol wt = 4) and sulfur hexafluoride (SF6) (mol wt = 146) has been studied by a rebreathing method in different postures. In nine normal subjects duplicate measurements were made in the erect (seated), supine, and lateral decubitus posture, at a constant tidal volume (700 ml) and frequency (1 Hz) starting from functional residual capacity (FRC). Additional measurements were made on four of the subjects, rebreathing seated erect at a volume similar to the relaxed FRC supine and supine at a volume similar to the relaxed FRC seated. In the supine posture the mean breath number to reach 99% equilibrium (n99), was not significantly different for the two gases, 8.9 for He and 9.8 for SF6. There was a difference (P less than 0.01) when erect; n99 (He) = 8.2 and n99 (SF6) = 10.9. The greatest He-SF6 difference (P less than 0.001) was in the lateral decubitus position n99 (He) = 10.1 and n99 (SF6) = 15.9. The mean relaxed FRC as percent of seated was 71% supine and 75% in lateral decubitus posture. Rebreathing seated at a lower volume did not abolish the He-SF6 mixing difference nor did rebreathing at a higher volume when supine induce a He-SF6 mixing difference. Thus the effect of posture on gas mixing cannot be due solely to lung volume and must represent a convective and diffusive dependent change in the distribution of ventilation per unit lung volume.

Influence of body position on dynamic compliance in young subjects

1977 ◽  
Vol 42 (5) ◽  
pp. 706-710 ◽  
Author(s):  
H. Sasaki ◽  
W. Hida ◽  
T. Takishima
Keyword(s):  
Frequency Dependence ◽  
Lung Volume ◽  
Body Position ◽  
Pulmonary Ventilation ◽  
Dynamic Compliance ◽  
Normal Subjects ◽  
Supine Posture ◽  
Significant Difference ◽  
Residual Capacity ◽  
Young Subjects

We studied the effect of a postural change from the erect to the supine position on the unevenness of pulmonary ventilation in six normal subjects. Static pressure-volume curves had a similar shape in both positions but the supine curves were shifted such that all transpulmonary pressures were 5–8 cmH2O lower. Dynamic compliance (Cdyn) was measured in seated and supine postures at functional residual capacity (FRC) and also while the seated subjects maintained end-expiratory lung volume at the level of supine FRC. Frequency dependence of Cdyn increased relative to that measured in the seated position at FRC when the subject remained seated but decreased his lung volume, or when he assumed the supine posture. There was no significant difference between Cdyn measured in the supine posture and in the seated at supine FRC. We conclude that the increased frequency dependence seen in the supine posture is largely attributed to the associated decrease of lung volume rather than to position per se.

Inspiratory muscles during exercise: a problem of supply and demand

1988 ◽  
Vol 64 (6) ◽  
pp. 2482-2489 ◽  
Author(s):  
P. Leblanc ◽  
E. Summers ◽  
M. D. Inman ◽  
N. L. Jones ◽  
E. J. Campbell ◽  
...  
Keyword(s):  
Lung Volume ◽  
Static Pressure ◽  
Total Lung Capacity ◽  
Supply And Demand ◽  
Normal Subjects ◽  
Esophageal Pressure ◽  
Maximum Exercise ◽  
Lung Capacity ◽  
Inspiratory Muscles ◽  
Residual Capacity

The capacity of inspiratory muscles to generate esophageal pressure at several lung volumes from functional residual capacity (FRC) to total lung capacity (TLC) and several flow rates from zero to maximal flow was measured in five normal subjects. Static capacity was 126 +/- 14.6 cmH2O at FRC, remained unchanged between 30 and 55% TLC, and decreased to 40 +/- 6.8 cmH2O at TLC. Dynamic capacity declined by a further 5.0 +/- 0.35% from the static pressure at any given lung volume for every liter per second increase in inspiratory flow. The subjects underwent progressive incremental exercise to maximum power and achieved 1,800 +/- 45 kpm/min and maximum O2 uptake of 3,518 +/- 222 ml/min. During exercise peak esophageal pressure increased from 9.4 +/- 1.81 to 38.2 +/- 5.70 cmH2O and end-inspiratory esophageal pressure increased from 7.8 +/- 0.52 to 22.5 +/- 2.03 cmH2O from rest to maximum exercise. Because the estimated capacity available to meet these demands is critically dependent on end-inspiratory lung volume, the changes in lung volume during exercise were measured in three of the subjects using He dilution. End-expiratory volume was 52.3 +/- 2.42% TLC at rest and 38.5 +/- 0.79% TLC at maximum exercise.

Mode shift of an inhaled aerosol bolus is correlated with flow sequencing in the human lung

2002 ◽  
Vol 92 (3) ◽  
pp. 1232-1238 ◽  
Author(s):  
Christopher N. Mills ◽  
Chantal Darquenne ◽  
G. Kim Prisk
Keyword(s):  
Vital Capacity ◽  
Normal Subjects ◽  
Phase Iii ◽  
Mode Shift ◽  
Nitrogen Washout ◽  
Single Breath ◽  
Posture Change ◽  
Supine Posture ◽  
Residual Capacity ◽  
Phase Iii Slope

We studied the effects on aerosol bolus inhalations of small changes in convective inhomogeneity induced by posture change from upright to supine in nine normal subjects. Vital capacity single-breath nitrogen washout tests were used to determine ventilatory inhomogeneity change between postures. Relative to upright, supine phase III slope was increased 33 ± 11% (mean ± SE, P < 0.05) and phase IV height increased 25 ± 11% ( P < 0.05), consistent with an increase in convective inhomogeneity likely due to increases in flow sequencing. Subjects also performed 0.5-μm-particle bolus inhalations to penetration volumes (Vp) between 150 and 1,200 ml during a standardized inhalation from residual volume to 1 liter above upright functional residual capacity. Mode shift (MS) in supine posture was more mouthward than upright at all Vp, changing by 11.6 ml at Vp = 150 ml ( P < 0.05) and 38.4 ml at Vp = 1,200 ml ( P < 0.05). MS and phase III slope changes correlated positively at deeper Vp. Deposition did not change at any Vp, suggesting that deposition did not cause the MS change. We propose that the MS change results from increased sequencing in supine vs. upright posture.

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.

Respiratory movements of the vocal cords

1983 ◽  
Vol 54 (5) ◽  
pp. 1269-1276 ◽  
Author(s):  
T. Brancatisano ◽  
P. W. Collett ◽  
L. A. Engel
Keyword(s):  
Lung Volume ◽  
Respiratory Control ◽  
Respiratory Muscles ◽  
Normal Subjects ◽  
Tight Coupling ◽  
Tidal Breathing ◽  
Vocal Cords ◽  
Residual Capacity ◽  
The Relationship ◽  
Respiratory Movements

We examined the movements of the vocal cords during tidal breathing, panting, and large changes in lung volume in 12 normal subjects. The glottis was observed with a fiber-optic bronchoscope, and the glottic image was recorded together with flow, volume, and a time marker onto videotape. Phasic respiratory swings in glottic width (dg) and glottic area (Ag) were reproducible in all subjects but differed substantially between subjects. In the group as a whole dg and Ag increased during inspiration to 10.1 +/- 5.6 mm and 126 +/- 8 mm2 (mean +/- SE), respectively, whereas during expiration the lowest values were 5.7 +/- 0.5 mm and 70 +/- 7 mm2, respectively. These extreme dimensions corresponded closely to the midtidal volume points in the respiratory cycle. Glottic width during vital capacity (VC) expirations was nearly 30% greater at a flow of 1.2 l/s than at 0.5 l/s, but the relationship between dg and lung volume differed between subjects. When swings in dg were minimized by panting, there was no difference in dg between functional residual capacity (FRC) and a volume corresponding to midinspiratory capacity. However, tidal breathing at this lung volume was associated with a 20% decrease in dg compared with breathing at FRC. Our observations indicate a tight coupling between the pattern of glottic movement and the respiratory volume cycle. The results suggest that during voluntary respiratory maneuvers both intrinsic laryngeal and respiratory muscles are recruited, participating as effector organs in ventilatory and respiratory control.

Regional Lung Function in Bilateral Diaphragmatic Paralysis

1980 ◽  
Vol 59 (6) ◽  
pp. 485-492 ◽  
Author(s):  
T. C. Amis ◽  
G. Ciofetta ◽  
J. M. B. Hughes ◽  
L. Loh
Keyword(s):  
Normal Subjects ◽  
Diaphragmatic Paralysis ◽  
Upright Posture ◽  
Alveolar Volume ◽  
Supine Posture ◽  
Regional Lung Function ◽  
Lower Lung ◽  
Lateral Decubitus ◽  
The Right ◽  
The Vertical Distribution

1. The distribution of regional function in the lungs of six patients with bilateral diaphragmatic paralysis was investigated by continuous inhalation and infusion of the radioactive gases 81mKr and 85mKr during tidal breathing. 2. In the supine and right lateral decubitus postures the vertical distribution of ventilation per unit alveolar volume was less in the dependent zones, the reverse of that found in normal subjects. In the upright posture ventilation was slightly decreased at the lung base. Perfusion per unit alveolar volume was more uniformly distributed than normally in the upright posture, and decreased from superior to inferior in the supine posture. In the lateral decubitus posture, perfusion of the lower lung was greater than that of the upper. Ventilation/perfusion ratios were more uniformly distributed in the patients than in normal subjects, except in the right lateral decubitus posture. 3. Alterations in the distribution of ventilation may be explained in terms of the altered mechanical interaction of chest wall, mediastinal and abdominal contents, with selective use of intercostal and accessory muscles. The effects on the distribution of blood flow are probably related to the low end-expiratory lung volume.

Lung volume, closing volume, and gas exchange

1982 ◽  
Vol 52 (6) ◽  
pp. 1453-1457 ◽  
Author(s):  
S. C. Morrison ◽  
D. G. Stubbing ◽  
P. V. Zimmerman ◽  
E. J. Campbell
Keyword(s):  
Gas Exchange ◽  
Lung Volume ◽  
Normal Subjects ◽  
Close Correlation ◽  
Closing Volume ◽  
Tidal Breathing ◽  
Co2 Partial Pressure ◽  
Residual Capacity ◽  
End Tidal ◽  
Arterial O2 Saturation

The effect of a voluntary reduction in lung volume on arterial O2 saturation (SaO2) was studied in 10 normal subjects aged 19–63 yr. SaO2 was measured by ear oximetry first during tidal breathing at functional residual capacity, and then during tidal breathing at 380 ml above residual volume. Tidal volume and breathing frequency were kept constant, and end-tidal CO2 partial pressure remained stable or fell in 9 out of 10 subjects. When lung volume was reduced, SaO2 fell by a mean of 1.5% (range 0–3%). Closing volume (CV) was measured by the N2-washout method (mean 0.89 liter, range 0.41–1.44). There was a close correlation between CV and the fall in SaO2 (r = 0.867, P = 0.001). Arterial and mixed venous CO2 were measured in one subject; the results indicated some fall in cardiac output following the lung volume change, but this accounted for less than half of the fall in SaO2. The relationship between CV and the lung volume at which tidal breathing occurs is an important determinant of pulmonary gas exchange through its effect on the matching of ventilation to perfusion.

scholarly journals Mechanical advantage of the canine diaphragm

1998 ◽  
Vol 85 (6) ◽  
pp. 2284-2290 ◽  
Author(s):  
Theodore A. Wilson ◽  
Aladin M. Boriek ◽  
Joseph R. Rodarte
Keyword(s):  
Lung Volume ◽  
Three Dimensional ◽  
Mechanical Advantage ◽  
Supine Posture ◽  
Abdominal Compliance ◽  
Lower Lung ◽  
Residual Capacity ◽  
Radiopaque Markers ◽  
Crural Diaphragm ◽  
Prone Posture

The mechanical advantage (μ) of a respiratory muscle is defined as the respiratory pressure generated per unit muscle mass and per unit active stress. The value of μ can be obtained by measuring the change in the length of the muscle during inflation of the passive lung and chest wall. We report values of μ for the muscles of the canine diaphragm that were obtained by measuring the lengths of the muscles during a passive quasistatic vital capacity maneuver. Radiopaque markers were attached along six muscle bundles of the costal and two muscle bundles of the crural left hemidiaphragms of four bred-for-research beagle dogs. The three-dimensional locations of the markers were obtained from biplane video-fluoroscopic images taken at four volumes during a passive relaxation maneuver from total lung capacity to functional residual capacity in the prone and supine postures. Muscle lengths were determined as a function of lung volume, and from these data, values of μ were obtained. Values of μ are fairly uniform around the ventral midcostal and crural diaphragm but significantly lower at the dorsal end of the costal diaphragm. The average values of μ are −0.35 ± 0.18 and −0.27 ± 0.16 cmH2O ⋅ g−1 ⋅ kg−1 ⋅ cm−2in the prone and supine dog, respectively. These values are 1.5–2 times larger than the largest values of μ of the intercostal muscles in the supine dog. From these data we estimate that during spontaneous breathing the diaphragm contributes ∼40% of inspiratory pressure in the prone posture and ∼30% in the supine posture. Passive shortening, and hence μ, in the upper one-third of inspiratory capacity is less than one-half of that at lower lung volume. The lower μ is attributed primarily to a lower abdominal compliance at high lung volume.

Effects of lung volume on maximal methacholine-induced bronchoconstriction in normal humans

1987 ◽  
Vol 62 (3) ◽  
pp. 1324-1330 ◽  
Author(s):  
D. J. Ding ◽  
J. G. Martin ◽  
P. T. Macklem
Keyword(s):  
Dose Response ◽  
Lung Volume ◽  
Normal Subjects ◽  
Smooth Muscle Contraction ◽  
Base Line ◽  
Pulmonary Resistance ◽  
Response Curves ◽  
Maximum Value ◽  
Residual Capacity ◽  
Normal Humans

We examined the effects of lung volume on the bronchoconstriction induced by inhaled aerosolized methacholine (MCh) in seven normal subjects. We constructed dose-response curves to MCh, using measurements of inspiratory pulmonary resistance (RL) during tidal breathing at functional residual capacity (FRC) and after a change in end-expiratory lung volume (EEV) to either FRC -0.5 liter (n = 5) or FRC +0.5 liter (n = 2). Aerosols of MCh were generated using a nebulizer with an output of 0.12 ml/min and administered for 2 min in progressively doubling concentrations from 1 to 256 mg/ml. After MCh, RL rose from a base-line value of 2.1 +/- 0.3 cmH2O. 1–1 X s (mean +/- SE; n = 7) to a maximum of 13.9 +/- 1.8. In five of the seven subjects a plateau response to MCh was obtained at FRC. There was no correlation between the concentration of MCh required to double RL and the maximum value of RL. The dose-response relationship to MCh was markedly altered by changing lung volume. The bronchoconstrictor response was enhanced at FRC - 0.5 liter; RL reached a maximum of 39.0 +/- 4.0 cmH2O X 1–1 X s. Conversely, at FRC + 0.5 liter the maximum value of RL was reduced in both subjects from 8.2 and 16.6 to 6.0 and 7.7 cmH2O X 1–1 X s, respectively. We conclude that lung volume is a major determinant of the bronchoconstrictor response to MCh in normal subjects. We suggest that changes in lung volume act to alter the forces of interdependence between airways and parenchyma that oppose airway smooth muscle contraction.

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