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The European Respiratory Journal Mar 2001The measurement of airway resistance by the interrupter technique (Rint) needs standardization. Should measurements be made be during the expiratory or inspiratory phase... (Comparative Study)
Comparative Study
The measurement of airway resistance by the interrupter technique (Rint) needs standardization. Should measurements be made be during the expiratory or inspiratory phase of tidal breathing? In reported studies, the measurement of Rint has been calculated as the median or mean of a small number of values, is there an important difference? Subjects were 2.5-5.0 yrs (median 4.0 yrs) who had previous respiratory symptoms. The Rint in expiration (RintE) and inspiration (RintI) pre and postsalbutamol, the coefficient of variation (CV) of values contributing to measurements, and bronchodilator responsiveness(BDR) in both phases were compared. Measurements using median and mean were compared. RintE was higher than RintI by 4% (p < 0.01). The CV of values making up RintE and RintI, and BDR measured in expiration and inspiration were similar. The median difference between means and medians of values making up measurements was 0.6% (range -6-11%). RintE has been shown to be consistently greater then RintI but the difference in this study is small. It is suggested that one or the other is chosen as the standard. In the present data the mean of a set of values contributing to a measurement was not significantly different from the median. However, the use of the median has been recommended since it is less affected by possible outlying values such as might be included by fully automated equipment.
Topics: Airway Resistance; Child, Preschool; Humans; Respiratory Function Tests
PubMed: 11405531
DOI: 10.1183/09031936.01.17304950 -
Pediatric Pulmonology 1991The purpose of this study was to assess the effectiveness of nebulized salbutamol in infants with a history of wheezing. Eighty-eight children aged 3-24 months with a... (Clinical Trial)
Clinical Trial Randomized Controlled Trial
The purpose of this study was to assess the effectiveness of nebulized salbutamol in infants with a history of wheezing. Eighty-eight children aged 3-24 months with a history of wheezing were studied, in seven groups: I (n = 15) and I/A (n = 17) with elevated specific airway resistance (SRaw); II (n = 17) with normal SRaw; III (n = 23), III/A (n = 17), and IV (n = 18) with normal SRaw exposed to carbachol bronchial challenge (CBC); and V (n = 13) serving as control. Infants for groups I/A and III/A were selected to match by age and by baseline and post-carbachol SRaw values, respectively. Baseline airway resistance and thoracic gas volume (TGV) were measured plethysmographically. Specific airway resistance was selected as an index of bronchial function. Thereafter every child in groups I, I/A and II inhaled 200 micrograms of salbutamol by tidal breathing, and the children in groups III, III/A, and IV were exposed to CBC. Following positive reaction to carbachol, children of groups III and III/A inhaled salbutamol (200 micrograms, tidal breathing), and those of group IV received no drug. Controls from group V with normal SRaw received placebo (phosphate-buffered saline). Plethysmography was repeated in all children at 5 minute intervals. Following salbutamol SRaw was reduced in children with elevated and normal SRaw. In contrast, children not receiving salbutamol had unchanged SRaw value. The response to salbutamol measured by SRaw, Raw, and TGV was not significantly different in the spontaneously obstructed infants compared to those who received carbachol. In conclusion, infants with a history of wheezing do respond to inhaled salbutamol.
Topics: Airway Resistance; Albuterol; Carbachol; Child, Preschool; Humans; Infant; Nebulizers and Vaporizers; Plethysmography; Respiratory Sounds
PubMed: 1852517
DOI: 10.1002/ppul.1950100310 -
Journal of Applied Physiology... Dec 1997At the onset of non-rapid-eye-movement (NREM) sleep there is a fall in ventilation and an increase in upper airway resistance (UAR). In healthy men there is a... (Clinical Trial)
Clinical Trial Comparative Study
At the onset of non-rapid-eye-movement (NREM) sleep there is a fall in ventilation and an increase in upper airway resistance (UAR). In healthy men there is a progressive increase in UAR as NREM sleep deepens. This study compared the pattern of change in UAR and ventilation in 14 men and 14 women (aged 18-25 yr) both during sleep onset and over the NREM phase of a sleep cycle (from wakefulness to slow-wave sleep). During sleep onset, fluctuations between electroencephalographic alpha and theta activity were associated with mean alterations in inspiratory minute ventilation and UAR of between 1 and 4.5 l/min and between 0.70 and 5.0 cmH2O . l-1 . s, respectively, with no significant effect of gender on either change (P > 0.05). During NREM sleep, however, the increment in UAR was larger in men than in women (P < 0.01), such that the mean levels of UAR at peak flow reached during slow-wave sleep were approximately 25 and 10 cmH2O . l-1 . s in men and women, respectively. We speculate that the greater increase in UAR in healthy young men may represent a gender-related susceptibility to sleep-disordered breathing that, in conjunction with other predisposing factors, may contribute to the development of obstructive sleep apnea.
Topics: Adolescent; Adult; Airway Resistance; Electroencephalography; Female; Humans; Male; Respiratory Mechanics; Sex Characteristics; Sleep
PubMed: 9390972
DOI: 10.1152/jappl.1997.83.6.1986 -
Journal of Applied Physiology... Dec 1988We studied the relationship between bronchoconstriction and the degree of trapping in saline-filled lungs isolated from guinea pigs postmortem after rapid...
We studied the relationship between bronchoconstriction and the degree of trapping in saline-filled lungs isolated from guinea pigs postmortem after rapid exsanguination. Airway resistance was measured in nine lungs, and in five lungs the site of airway narrowing was located radiographically. Animals were anesthetized with pentobarbital sodium, degassed by O2 absorption, then rapidly exsanguinated when O2 absorption was almost complete. Liquid trapping was assessed from the pressure-volume behaviour measured in saline-filled lungs. During a slow deflation from maximum volume, alveolar liquid pressure (Palv) was measured by the micropipette-servonulling method, airway opening pressure (Pao) by a strain gauge, and flow rate (Q) by weighing a reservoir connected to the airway. Airway resistance (Raw) was calculated at different lung volumes from the relationship: Raw = (Palv-Pao)/Q. In untreated lungs, Raw and fluid trapping were relatively high, and severe bronchoconstriction occurred at the level of the main stem and lobar bronchi. Nifedipine infusion reduced Raw 40-fold and decreased trapping. Raw was further reduced 10-fold and fluid trapping was minimal in lungs pretreated with nifedipine before exsanguination. Results suggest a close association between bronchoconstriction and fluid trapping in guinea pig lungs.
Topics: Airway Resistance; Animals; Bronchi; Guinea Pigs; Lung Volume Measurements; Male; Nifedipine; Pressure; Pulmonary Alveoli; Punctures
PubMed: 3215844
DOI: 10.1152/jappl.1988.65.6.2446 -
American Journal of Physiology. Lung... May 2022Lung resistance () and elastance () can be measured during positive or negative pressure ventilation. Whether the different modes of ventilation produce different and...
Lung resistance () and elastance () can be measured during positive or negative pressure ventilation. Whether the different modes of ventilation produce different and is still being debated. Although negative pressure ventilation (NPV) is more physiological, positive pressure ventilation (PPV) is more commonly used for treating respiratory failure. In the present study, we measured lung volume, airway diameter, and airway volume, as well as and with PPV and NPV in explanted sheep lungs. We found that lung volume under a static pressure, either positive or negative, was not different. However, and were significantly higher in NPV at high inflation pressures. Interestingly, diameters of smaller airways (diameters <3.5 mm) and total airway volume were significantly greater at high negative inflation pressures compared with those at high positive inflation pressures. This suggests that NPV is more effective in distending the peripheral airways, likely due to the fact that negative pressure is applied through the pleural membrane and reaches the central airways via the peripheral airways, whereas positive pressure is applied in the opposite direction. More distension of lung periphery could explain why is higher in NPV (vs. PPV), because the peripheral parenchyma is a major source of tissue resistance, which is a part of the that increases with pressure. This explanation is consistent with the finding that during high frequency ventilation (>1 Hz, where reflects airway resistance more than tissue resistance), the difference in between NPV and PPV disappeared.
Topics: Airway Resistance; Animals; Lung; Positive-Pressure Respiration; Respiratory Function Tests; Respiratory Mechanics; Respiratory Physiological Phenomena; Sheep
PubMed: 35272489
DOI: 10.1152/ajplung.00464.2021 -
Paediatric Respiratory Reviews Mar 2000Insight into the physiology of a forced expiration is the most important prerequisite for understanding and correctly interpreting the most common pulmonary function... (Review)
Review
Insight into the physiology of a forced expiration is the most important prerequisite for understanding and correctly interpreting the most common pulmonary function tests like spirometry and recording of a maximum expiratory flow-volume curve. Along the airway, intraluminal pressure falls progressively from alveolar pressure in the periphery to atmospheric pressure at the airway opening. Downstream of the equal pressure point, where intraluminal equals transthoracic pressure, the airway is dynamically compressed. Once the forced expiration is flow limited, more transthoracic pressure will rather effect more compression than a further increase in flow. It follows that the achieved maximum expiratory flow rates are then exclusively defined by the resistance of the intrathoracic airways and no longer by muscular effort. The end of a forced expiration is determined by the elastic resistance of the thoracic cage and by airway closure.
Topics: Airway Resistance; Exhalation; Forced Expiratory Flow Rates; Humans
PubMed: 16263442
DOI: 10.1053/prrv.2000.0010 -
Journal of Applied Physiology... May 1996Recent studies have suggested that part of the measured increase in lung tissue resistance after bronchoconstriction is an artifact due to increased airway...
Recent studies have suggested that part of the measured increase in lung tissue resistance after bronchoconstriction is an artifact due to increased airway inhomogeneities. To resolve this issue, we measured lung impedance (ZL) in seven open-chest rats with the lungs equilibrated on room air and then on a mixture of neon and oxygen (NeOx). The rats were placed in a body box with the tracheal tube leading through the box wall. A broadband flow signal was delivered to the box. The signal contained seven oscillation frequencies in the 0.234- to 12.07-Hz range, which were combined to produce tidal ventilation. The ZL was measured before and after bronchoconstriction caused by infusion of methacholine (MCh). Partitioning of airway and tissue properties was achieved by fitting ZL with a model including airway resistance (Raw), airway inertance, tissue damping (G), and tissue elastance (H). We hypothesized that if the inhomogeneities were not significant, the apparent tissue properties would be independent of the resident gas, whereas Raw would scale as the ratio of viscosities. Indeed, during control conditions, the NeOx-to-air ratios for G and H were both 1.03 +/- 0.04. Also, there was a small increase in lung elastance (EL) between 0.234 and 4 Hz that was similar on air and NeOx. During MCh infusion, Raw and G increased markedly (45-65%), but the increase in H was relatively small ( < 13%). The NeOx-to-air Raw and H ratios remained the same. However, the NeOx-to-air G ratio increased to 1.19 +/- 0.07 (P < 0.01) and the increase in EL with frequency was now marked and dependent on the resident gas. These results provide direct evidence that for a healthy rat lung airway inhomogeneities do not significantly influence the lung resistance or EL vs. frequency data. However, during MCh-induced constriction, a large portion of the increase in tissue resistance and the altered frequency dependence of EL are virtual and a consequence of the augmented airway inhomogeneities.
Topics: Airway Resistance; Animals; Bronchoconstriction; Lung; Male; Models, Biological; Rats; Rats, Wistar; Respiratory Physiological Phenomena
PubMed: 8727575
DOI: 10.1152/jappl.1996.80.5.1841 -
Journal of Applied Physiology... Sep 1994Elastic recoil has been reported to decrease with increasing age in human subjects. In the current study, we hypothesized that aging influences mechanical... (Comparative Study)
Comparative Study
Elastic recoil has been reported to decrease with increasing age in human subjects. In the current study, we hypothesized that aging influences mechanical interdependence, which affects the magnitude of agonist-induced airway constriction. To examine this hypothesis, we compared the effects of changing lung volume on airway resistance (Raw) under baseline conditions and during methacholine-induced constriction in adult (14 mo old, 624 +/- 14 g; n = 11) and aged (29 mo old, 629 +/- 9 g; n = 11) Sprague-Dawley rats. With use of alveolar capsules, Raw was directly measured under baseline conditions at different levels of end-expiratory transpulmonary pressure (PL; 3-11 cmH2O). Then aerosolized methacholine was delivered (125 mg/ml), and measurements were performed at different levels of PL (3 and 11 cmH2O). From measured tracheal flow and tracheal and alveolar pressures in open-chest animals during mechanical ventilation (6 ml/kg tidal volume, 1 Hz frequency), we calculated dynamic lung elastance and resistance of lung, tissue, and airway. In the baseline conditions, we found that increasing lung volume decreased Raw similarly in both groups but that lung elastance was reduced in the aged group at PL > or = 7 cmH2O. The shape constant obtained from the pressure-volume curve in the aged rats was significantly greater than that in the adult rats. During induced constriction, higher lung volume significantly lowered Raw in the adult group, whereas Raw was not significantly reduced by increasing PL in the aged group. These observations suggest that increasing age may affect the mechanical properties of the airway and/or airway-parenchymal interdependence.
Topics: Aging; Airway Resistance; Animals; Elasticity; Lung; Lung Volume Measurements; Male; Methacholine Chloride; Pulmonary Alveoli; Rats; Rats, Sprague-Dawley; Respiratory Mechanics; Total Lung Capacity
PubMed: 7836119
DOI: 10.1152/jappl.1994.77.3.1172 -
American Journal of Respiratory and... Oct 2014Airway narrowing is maintained for a prolonged period after acute bronchoconstriction in humans in the absence of deep inspirations (DIs). (Randomized Controlled Trial)
Randomized Controlled Trial
RATIONALE
Airway narrowing is maintained for a prolonged period after acute bronchoconstriction in humans in the absence of deep inspirations (DIs).
OBJECTIVES
To determine whether maintenance of airway smooth muscle (ASM) shortening is responsible for the persistence of airway narrowing in healthy subjects following transient methacholine (MCh)-induced bronchoconstriction.
METHODS
On two separate visits, five healthy subjects underwent MCh challenges until respiratory system resistance (Rrs) had increased by approximately 1.5 cm H2O/L/s. Subjects took a DI either immediately after or 30 minutes after the last dose. The extent of renarrowing following the bronchodilator effect of DI was used to assess the continued action of MCh (calculated as percent change in Rrs from the pre-DI Rrs). We then used human bronchial rings to determine whether ASM can maintain shortening during a progressive decrease of carbachol concentration.
MEASUREMENTS AND MAIN RESULTS
The increased Rrs induced by MCh was maintained for 30 minutes despite waning of MCh concentration over that period, measured as attenuated renarrowing when the DI was taken 30 minutes after compared with immediately after the last dose (7 min post-DI, -36.2 ± 11.8 vs. 14.4 ± 13.2%; 12 min post-DI, -39.5 ± 9.8 vs. 15.2 ± 17.8%). Ex vivo, ASM shortening was largely maintained during a progressive decrease of carbachol concentration, even down to concentrations that would not be expected to induce shortening.
CONCLUSIONS
The maintenance of airway narrowing despite MCh clearance in humans is attributed to an intrinsic ability of ASM to maintain shortening during a progressive decrease of contractile stimulation.
Topics: Adult; Airway Resistance; Bronchi; Bronchial Provocation Tests; Bronchoconstriction; Bronchoconstrictor Agents; Healthy Volunteers; Humans; Inhalation; Male; Methacholine Chloride; Middle Aged; Muscle, Smooth
PubMed: 25191967
DOI: 10.1164/rccm.201403-0502OC -
Sleep Jan 2005To examine the utility of four methods used to detect increased upper airway resistance leading to arousal from sleep.
STUDY OBJECTIVES
To examine the utility of four methods used to detect increased upper airway resistance leading to arousal from sleep.
DESIGN
Ten overnight sleep studies were conducted on normal subjects who reported increased snoring and/or witnessed apneas following alcohol ingestion. Alcohol was used to increase upper airway resistance in these normal subjects before ovemight polysomnography. Four methods to detect the presence of increased upper airway resistance were used: esophageal pressure manometry; respiratory inductive plethysmography; a piezoelectrically treated stretch sensor adhered to the supraclavicular fossa; nasal flow measured with oxygen cannula and differential pressure transducer.
SETTING
Private Sleep Laboratory.
PARTICIPANTS
Ten normal, healthy volunteers (5 male, 5 female).
INTERVENTIONS
Alcohol ingestion as red wine (14% alcohol), 180-540 mL one to two hours before overnight polysomnography. Esophageal catheterisation.
MEASUREMENTS AND RESULTS
Two hundred twenty-seven electroencephalogram arousals were preceded by inspiratory flow limitation and/or increased respiratory effort. Flattening of the nasal flow profile preceded all 227 arousals. In contrast, only 40% of arousals were preceded by an increase in the size of the stretch sensor signal, 22% by more-negative deflection of the esophageal pressure signal and 21% by increase in the signal size of respiratory inductance plethysmography.
CONCLUSION
These findings indicate that the most reliable method of detecting increased upper airway resistance leading to arousal from sleep is the nasal cannula/pressure transducer method and suggest that many arousals induced by increased upper airway resistance may be caused by mechanoreceptor afferents.
Topics: Adult; Airway Resistance; Circadian Rhythm; Electroencephalography; Female; Humans; Male; Middle Aged; Polysomnography; Sleep, REM; Time Factors
PubMed: 15700724
DOI: 10.1093/sleep/28.1.85