The vulnerable small airway

PEDIATRICS ◽  
1977 ◽  
Vol 59 (5) ◽  
pp. 783-785
Author(s):  
V. Chernick
Keyword(s):  
Flow Resistance ◽  
Gas Flow ◽  
Airway Resistance ◽  
Clear Understanding ◽  
Small Airways ◽  
Peripheral Airways ◽  
Pulmonary Flow ◽  
Peripheral Airway ◽  
First Time

Fundamental physiological work in the late 1960s provided for the first time a clear understanding of (1) the role of the small airways (< 2 mm in diameter) in determining overall airway resistance to gas flow and (2) the relationship between central and peripheral airway resistance and lung growth.1,2 Involvement of the small airways early in the course of cystic fibrosis has been previously commented upon and documented in Pediatrics.3-5 After the age of about 5 years, the flow resistance of peripheral airways constitutes only about 10% to 20% of total pulmonary flow resistance,2 a fraction so small that conventional measurement of total resistance cannot detect small changes in the peripheral component.

Deposition of aerosol particles and flow resistance in mathematical and experimental airway models

1983 ◽  
Vol 55 (1) ◽  
pp. 154-163 ◽  
Author(s):  
C. S. Kim ◽  
L. K. Brown ◽  
G. G. Lewars ◽  
M. A. Sackner
Keyword(s):  
Flow Resistance ◽  
Airway Resistance ◽  
Flow Distribution ◽  
Aerosol Deposition ◽  
Lung Model ◽  
Straight Tube ◽  
Small Airways ◽  
Two Phase ◽  
Gas Liquid Flow ◽  
Airway Walls

Aerosol deposition and flow resistance in obstructed airways were determined from five mathematical and experimental airway models. The first three models were theoretical and based upon Weibel's symmetrical lung model with 1) uniform reduction of airway diameter in various groups of airway generations; 2) obstruction of a few major airways such that a severe uneven flow distribution occurs in the lung; 3) focal constriction of selected large airways. In model 3, an empirical formula was utilized to assess deposition and resistance in the constricted airways. The remaining two models were tested experimentally; 4) oscillation of a compliant wall in a straight tube and 5) two-phase gas-liquid flow utilizing human sputum in a rigid branching tube. In models 1, 2, and 3, airway resistance increased to a greater extent than did the increase of aerosol deposition except when small airways were obstructed in model 1. Here, the increase of aerosol deposition was slightly higher than the rise in airway resistance. A sharp increase of aerosol deposition with a minimal increase of flow resistance was demonstrated in models 4 and 5. These data indicate that aerosol deposition may be a more sensitive indicator of airway abnormalities than overall airway resistance in small airways obstruction, during oscillation of large and medium airway walls, and when excessive secretions within the airways move with a wave or slug motion.

Flow Resistance in Tracheotomy Tubes

1973 ◽  
Vol 82 (6) ◽  
pp. 827-830 ◽  
Author(s):  
John Cavo ◽  
Joseph H. Ogura ◽  
Donald G. Sessions ◽  
J. Roger Nelson
Keyword(s):  
Laminar Flow ◽  
Respiratory System ◽  
Flow Resistance ◽  
Airway Resistance ◽  
Upper Airway ◽  
Plastic Tube ◽  
Flow Rates ◽  
Pressure Drops ◽  
Adult Human

The role of the upper airway (the breathing passage above the trachea) in maintaining the normal junction of the respiratory system has been suggested by previous investigators. During a tracheotomy the upper airway is by-passed by a prosthetic metal or plastic tube which is placed into the trachea through the neck. In order to determine which, among the most commonly used tracheotomy tubes, most closely simulate the flow resistance of the adult human upper airway, a series of varying flow rates were passed through different sized tubes. Pressure drops were recorded and resistance values were thereby determined. Our data was compared with previously determined values for flow resistance of the adult human upper airway. Resistance related to turbulent and laminar flow was considered. On the basis of our data we have suggested that large caliber tracheotomy tubes be used in adult patients in whom the prolonged need for a tracheotomy is anticipated.

Use of collateral airways to assess airway reactivity

1991 ◽  
Vol 70 (1) ◽  
pp. 349-356 ◽  
Author(s):  
D. H. Corddry ◽  
R. A. Sauder ◽  
G. G. Weinmann ◽  
C. A. Hirshman ◽  
W. Mitzner
Keyword(s):  
Dose Response ◽  
Gas Flow ◽  
Response Curves ◽  
Airway Reactivity ◽  
Resistance Response ◽  
Peripheral Airways ◽  
Lung Segment ◽  
Peripheral Airway ◽  
The Mean ◽  
Dose Response Curves

We investigated the correlation between collateral airway reactivity and other indexes of lung reactivity in response to aerosol and intravenous (iv) challenges. In four anesthetized mongrel dogs, we measured the peripheral airway resistance (Rp) to gas flow out of a wedged lung segment in different lobes on multiple occasions. We obtained dose-response curves of peripheral airways challenged with iv histamine or aerosols through the bronchoscope. During the same iv bolus challenge, whole lung airway pressure (Paw) responses to histamine were also measured. On separate occasions, changes in lung resistance (RL) were measured after the whole lung was challenged with a histamine aerosol. Reactivity was assessed from the dose-response curves for Rp and RL as the PD50 (dose required to produce a 50% increase); for changes in Paw we calculated the PD15 (dose required to produce a 15% increase over baseline). Results for Rp showed considerably more variability among different lobes in a given animal with the aerosol challenge through the bronchoscope than with the iv challenge. With aerosol challenge there were no significant differences in the mean PD50 for Rp among any of the animals. However, with the iv challenge two of the dogs showed significant differences from the others in reactivity assessed with Rp (P less than 0.01). Moreover, the differences found in the peripheral airways with iv challenge reflected differences found in whole lung reactivity assessed with either iv challenge (Paw vs. Rp, r2 = 0.96) or whole lung aerosol challenge (RL vs. Rp, r2 = 0.84). We conclude that the measurement of the collateral resistance response to iv challenge may provide a sensitive method for assessing airway reactivity.

Eicosanoids modulate hyperpnea-induced bronchoconstriction in canine peripheral airways

1996 ◽  
Vol 81 (3) ◽  
pp. 1255-1263 ◽  
Author(s):  
C. Omori ◽  
P. Tagari ◽  
A. N. Freed
Keyword(s):  
Bronchoalveolar Lavage ◽  
Wall Temperature ◽  
Airway Resistance ◽  
Bronchoalveolar Lavage Fluid ◽  
Lavage Fluid ◽  
Airway Wall ◽  
Airway Reactivity ◽  
Dry Air ◽  
Peripheral Airways ◽  
Peripheral Airway

We examined the role of leukotrienes (LTs) in the development of dry air-induced bronchoconstriction (AIB) in canine peripheral airways. Airway reactivity to exogenous LTs was first tested by using an LTD4 aerosol challenge: peripheral airway resistance increased approximately 130 +/- 51% (n = 4) above baseline when compared with its vehicle control. AIB was then assessed by measuring peripheral airway resistance after, and airway wall temperature during, a dry air challenge (DAC). Treatment with a peptidoleukotriene biosynthesis inhibitor (MK-0591) attenuated AIB by approximately 65% without altering airway wall temperature. The fact that MK-0591 did not alter airway reactivity to aerosolized acetylcholine and completely inhibited Ca2+ ionophore-induced LTB4 generation in canine whole blood attests to the specificity of the drug. Treatment with MK-0591 did not affect the increased number of epithelial cells recovered in bronchoalveolar lavage fluid 5 min after DAC. Concentrations of LTs and other eicosanoids in bronchoalveolar lavage fluid from vehicle-treated DAC airways were increased above baseline values; only LTs were reduced by MK-0591. Before MK-0591, AIB was significantly correlated with the dry air-induced generation of LTC4, LTD4, and LTE4. After treatment with MK-0591, AIB was correlated with thromboxane B2, prostaglandin (PG) F2 alpha, and PGE2. We conclude that hyperpnea with dry air stimulates local production and release of LTs in canine bronchi and, alone with the generation of bronchoconstricting and bronchodilating PGs, plays a central role in the modulation of AIB.

Relationship of central and peripheral airway resistance to lung volume in dogs

1978 ◽  
Vol 44 (5) ◽  
pp. 728-737 ◽  
Author(s):  
F. G. Hoppin ◽  
M. Green ◽  
M. S. Morgan
Keyword(s):  
Lung Volume ◽  
Peripheral Resistance ◽  
Small Airways ◽  
Peripheral Airways ◽  
Tissue Resistance ◽  
Peripheral Airway ◽  
Phase Lags ◽  
A New Technique ◽  
Isotropic Expansion ◽  
Relationship Of

We could not reconcile reported relationships between lung resistance measurements and lung volume with bronchographic and anatomic studies showing that airway diameters change monotonically with lung volume and that small airways change diameter proportionately at least as much as large ones. Accordingly we measured central and peripheral airways resistances with a new technique. The relevant pressures were measured with a tracheal cannula, a wedged retrograde catheter, and two parenchymal needles in seven open-chested dogs while pleural pressure was oscillated at 1 Hz. In contrast to previous studies, the volume dependency of peripheral resistance was at least as great as that of central resistance with vagi intact, the volume dependencies of central and peripheral resistances were not abolished by vagotomy, and neither resistance increased systematically at high volumes. Volume dependency of central resistance resembled predictions for isotropic expansion of airways with vagi cut but increased with bronchomotor tone. These results fit generally with bronchographic data. Previous studies may have been affected by volume dependency due to “tissue resistance” and catheter phase lags.

Lemakalim attenuates hypocapnia- and dry air-induced bronchoconstriction in canine peripheral airways

1993 ◽  
Vol 75 (1) ◽  
pp. 86-92 ◽  
Author(s):  
K. S. Lindeman ◽  
A. N. Freed
Keyword(s):  
Airway Resistance ◽  
Channel Blocker ◽  
K Channel ◽  
Dry Air ◽  
Peripheral Airways ◽  
Airway Constriction ◽  
Before And After ◽  
Peripheral Airway ◽  
Anesthetized Dogs ◽  
K Channel Opener

To determine the effect of changes in potassium (K+) flux on airway constriction, we studied effects of lemakalim, a K+ channel opener, and glibenclamide, an ATP-sensitive K+ channel blocker. A wedged bronchoscope technique was used to measure peripheral airway resistance (Rp) in anesthetized dogs. Rp was measured before and after constriction of the airways by hypocapnic challenge, acetylcholine aerosol, or dry air hyperpnea. Lemakalim (5 micrograms/kg i.v.) was administered, and the challenge was repeated. Lemakalim attenuated responses to hypocapnia by 72 +/- 7% (n = 6, P = 0.0007) and to dry air challenge by 37 +/- 8% (n = 6, P = 0.005) but not to acetylcholine. On separate days, sublobar segments were pretreated with aerosolized glibenclamide (2 mg/ml), and responses to hypocapnic challenge were measured before and after lemakalim (5 micrograms/kg i.v.), nifedipine (20 micrograms/kg i.v.), or albuterol (1 microgram/kg i.v.). In the presence of glibenclamide, lemakalim had no significant effect on responses to hypocapnia; however, both nifedipine (n = 6, P = 0.0003) and albuterol (n = 6, P = 0.0001) attenuated responses to hypocapnic challenge. These findings suggest that lemakalim attenuated hypocapnic bronchoconstriction by promoting K+ efflux through ATP-sensitive K+ channels.

Histamine-induced constriction of canine peripheral lung: an airway or tissue response?

1991 ◽  
Vol 71 (1) ◽  
pp. 287-293 ◽  
Author(s):  
M. S. Ludwig ◽  
F. M. Robatto ◽  
P. D. Sly ◽  
M. Browman ◽  
J. H. Bates ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Airway Resistance ◽  
Linear Motor ◽  
Tissue Response ◽  
Alveolar Region ◽  
Peripheral Airways ◽  
Peripheral Lung ◽  
Peripheral Airway ◽  
Baseline Conditions ◽  
Measured Pressure

We compared the histamine responsiveness of peripheral airways (less than 6.0 mm diam) and parenchymal tissues in eight anesthetized paralyzed open-chest mongrel dogs. We measured pressure in a peripheral bronchus by using an antegrade wedged catheter and pressure in the alveolar region subtended by the wedged bronchus by using an alveolar capsule. Sinusoidal volume oscillations at a frequency of 0.5 Hz were delivered by a linear motor pump into the segment through the wedged catheter. We calculated the resistance of the segment (Rseg) and partitioned Rseg into tissue viscance (i.e., proportional to the resistive pressure drop between the alveolus and the pleura) and peripheral airway resistance. Measurements were taken under baseline conditions and after delivery of increasing concentrations of aerosolized histamine (0.1 micrograms/ml to 100.0 mg/ml) into the segment. We found that the histamine responsiveness of the peripheral airways and lung tissues varied markedly within a given dog. In four of eight dogs the airways were more responsive to histamine, in three of eight the tissues were more responsive, and in one of eight the response was equivalent at the two sites. We conclude that in a given animal, there is marked heterogeneity in the histamine responsiveness of the peripheral airways and parenchymal tissues and that either may dominate responsiveness in the peripheral lung.

A beta 2-adrenergic agonist inhibits dry air-induced injury in canine peripheral airways

1995 ◽  
Vol 78 (6) ◽  
pp. 2169-2179 ◽  
Author(s):  
C. Omori ◽  
B. H. Schofield ◽  
W. Mitzner ◽  
A. N. Freed
Keyword(s):  
Airway Resistance ◽  
Ciliated Cell ◽  
Mucosal Damage ◽  
Mast Cell Degranulation ◽  
Adrenergic Agonist ◽  
Dry Air ◽  
Peripheral Airways ◽  
Peripheral Airway ◽  
Anesthetized Dogs ◽  
Beta 2

We examined the effects of a beta 2-agonist on dry air-induced injury in canine peripheral airways. Dry air-induced bronchoconstriction (AIB) was assessed by measuring peripheral airway resistance in anesthetized dogs. Salbutamol reduced AIB by approximately 75% compared with control values. Colloidal carbon was used to detect bronchovascular leakage in contralateral sublobar segments that were pretreated with saline or salbutamol. About 87% of the perimeter of bronchi was damaged after dry air challenge in saline-treated segments. Salbutamol reduced mucosal damage by approximately 30% (P < 0.05). The mucosa of bronchioles was not injured. The average goblet-to-ciliated cell ratio (which reflects mucosal perturbation) in bronchi decreased from 0.38 in control bronchi to 0.15 in challenged bronchi, and this effect was also evident in bronchioles. Salbutamol did not affect this decrement. Dry air challenge also caused degranulation of mast cells located below damaged mucosa, dilation of bronchial vessels, and leakage from capillaries and venules located below normal ciliated and damaged mucosa of bronchi. Thus, we conclude that salbutamol attenuates epithelial damage and AIB but fails to inhibit mast cell degranulation and vascular hyperpermeability.

Control of bronchomotor tone during perinatal development in sheep

1993 ◽  
Vol 75 (4) ◽  
pp. 1486-1496 ◽  
Author(s):  
J. J. Perez Fontan ◽  
L. P. Kinloch
Keyword(s):  
Airway Resistance ◽  
Vagal Stimulation ◽  
Peripheral Resistance ◽  
Term Newborn ◽  
Peripheral Airways ◽  
Pleural Surface ◽  
Peripheral Airway ◽  
Cervical Vagotomy ◽  
Central Airway ◽  
Bronchomotor Tone

To characterize the perinatal maturation of the cholinergic control of the airways, we compared the effects of bilateral cervical vagotomy and supramaximal vagal stimulation on the airway resistances of 7 premature (130–133 days of gestation), 11 term newborn, and 9 9-wk-old lambs anesthetized with pentobarbital. Resistances were partitioned between central and peripheral airways with catheters placed retrogradely into peripheral bronchi and capsules attached to the pleural surface in communication with subpleural air spaces. The central and peripheral airway resistances of premature and term newborn lambs and the peripheral resistance of 9-wk-old lambs decreased after vagotomy but only when the lungs were ventilated with small tidal volumes at mean transpulmonary pressures < or = 7.5 cmH2O. Vagotomy caused smaller absolute changes in central airway resistance than vagal stimulation. In contrast, both vagotomy and vagal stimulation produced similar absolute changes in peripheral airway resistance, indicating that resting cholinergic outflow is preferentially distributed to the peripheral airways even at the earlier ages. The effects of vagal stimulation on airway resistance were prevented by atropine. Our results prove that a resting bronchomotor tone can be present in both central and peripheral airways before the term of gestation in sheep. This tone depends on the activity of cholinergic fibers in the vagus and can be regionally controlled.

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