Gas compression in lungs decreases peak expiratory flow depending on resistance of peak flowmeter

1997 ◽  
Vol 83 (5) ◽  
pp. 1517-1521 ◽  
Author(s):  
O. F. Pedersen ◽  
T. F. Pedersen ◽  
M. R. Miller
Keyword(s):  
Peak Expiratory Flow ◽  
Wave Speed ◽  
Vital Capacity ◽  
Added Resistance ◽  
Alveolar Pressure ◽  
Healthy Men ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
Expiratory Flow ◽  
Gas Volume

Pedersen, O. F., T. F. Pedersen, and M. R. Miller. Gas compression in lungs decreases peak expiratory flow depending on resistance of peak flowmeter. J. Appl. Physiol. 83(5): 1517–1521, 1997.—It has recently been shown (O. F. Pedersen T. R. Rasmussen, Ø. Omland, T. Sigsgaard, P. H. Quanjer, and M. R. Miller. Eur. Respir. J. 9: 828–833, 1996) that the added resistance of a mini-Wright peak flowmeter decreases peak expiratory flow (PEF) by ∼8% compared with PEF measured by a pneumotachograph. To explore the reason for this, 10 healthy men (mean age 43 yr, range 33–58 yr) were examined in a body plethysmograph with facilities to measure mouth flow vs. expired volume as well as the change in thoracic gas volume (Vb) and alveolar pressure (Pa). The subjects performed forced vital capacity maneuvers through orifices of different sizes and also a mini-Wright peak flowmeter. PEF with the meter and other added resistances were achieved when flow reached the perimeter of the flow-Vb curves. The mini-Wright PEF meter decreased PEF from 11.4 ± 1.5 to 10.3 ± 1.4 (SD) l/s ( P < 0.001), Pa increased from 6.7 ± 1.9 to 9.3 ± 2.7 kPa ( P < 0.001), an increase equal to the pressure drop across the meter, and caused Vb at PEF to decrease by 0.24 ± 0.09 liter ( P < 0.001). We conclude that PEF obtained with an added resistance like a mini-Wright PEF meter is a wave-speed-determined maximal flow, but the added resistance causes gas compression because of increased Pa at PEF. Therefore, Vb at PEF and, accordingly, PEF decrease.

Peak flowmeter resistance decreases peak expiratory flow in subjects with COPD

2000 ◽  
Vol 89 (1) ◽  
pp. 283-290 ◽  
Author(s):  
Martin R. Miller ◽  
Ole F. Pedersen
Keyword(s):  
Peak Expiratory Flow ◽  
Healthy Subjects ◽  
Normal Subjects ◽  
Chronic Obstructive ◽  
Flow Limitation ◽  
Added Resistance ◽  
Elastic Recoil ◽  
Obstructive Pulmonary Disease ◽  
Thoracic Gas Volume ◽  
Expiratory Flow

Previous studies have shown that the added resistance of a mini-Wright peak expiratory flow (PEF) meter reduced PEF by ∼8% in normal subjects because of gas compression reducing thoracic gas volume at PEF and thus driving elastic recoil pressure. We undertook a body plethysmographic study in 15 patients with chronic obstructive pulmonary disease (COPD), age 65.9 ± 6.3 yr (mean ± SD, range 53–75 yr), to examine whether their recorded PEF was also limited by the added resistance of a PEF meter. The PEF meter increased alveolar pressure at PEF (Ppeak) from 3.7 ± 1.4 to 4.7 ± 1.5 kPa ( P = 0.01), and PEF was reduced from 3.6 ± 1.3 l/s to 3.2 ± 0.9 l/s ( P = 0.01). The influence of flow limitation on PEF and Ppeak was evaluated by a simple four-parameter model based on the wave-speed concept. We conclude that added external resistance in patients with COPD reduced PEF by the same mechanisms as in healthy subjects. Furthermore, the much lower Ppeak in COPD patients is a consequence of more severe flow limitation than in healthy subjects and not of deficient muscle strength.

T model partition of lung and respiratory system impedances

1995 ◽  
Vol 78 (3) ◽  
pp. 938-947 ◽  
Author(s):  
M. Rotger ◽  
R. Farre ◽  
R. Peslin ◽  
D. Navajas
Keyword(s):  
Respiratory System ◽  
Frequency Range ◽  
Tissue Impedance ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
The Mean ◽  
Gas Volume ◽  
Mean Compliance ◽  
Gas Compressibility ◽  
Shunt Impedance

The aim of this work was to demonstrate that the three compartments of the lung T network and the chest wall impedance (Zcw) can be identified from input and transfer impedances of the respiratory system if the pleural pressure is recorded during the measurements. The method was tested in six healthy volunteers in the range of 8–32 Hz. The impedances resulting from the decomposition confirm the adequacy of the monoalveolar structure commonly used in healthy subjects. Indeed, the T shunt impedance is well modeled by a purely compliant element, the mean compliance [0.038 +/- 0.081 (SD) l/kPa], which coincides within 9.5 +/- 6.3% of the alveolar gas compressibility derived from thoracic gas volume (0.036 +/- 0.011 l/kPa). The results obtained provide experimental evidence that the alveolar gas compression is predominantly isothermal and that lung tissue impedance is negligible throughout the whole frequency range. The shape of Zcw is consistent with a low compliance-low inertance pathway in parallel with a high compliance-high inertance pathway. We conclude that the proposed method is able to reliably identify the T network featuring the lung and Zcw.

Partitioning of airway and respiratory tissue mechanical impedances by body plethysmography

1998 ◽  
Vol 84 (2) ◽  
pp. 553-561 ◽  
Author(s):  
R. Peslin ◽  
C. Duvivier
Keyword(s):  
Body Plethysmography ◽  
Tissue Resistance ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
Airway Opening ◽  
Elastic Loading ◽  
Gas Volume ◽  
The Relationship ◽  
Respiratory Tissue ◽  
Good Agreement

Peslin, R., and C. Duvivier. Partitioning of airway and respiratory tissue mechanical impedances by body plethysmography. J. Appl. Physiol. 84(2): 553–561, 1998.—We have tested the feasibility of separating the airway (Zaw) and tissue (Zti) components of total respiratory input impedance (Zrs,in) in healthy subjects by measuring alveolar gas compression by body plethysmography (Vpl) during pressure oscillations at the airway opening. The forced oscillation setup was placed inside a body plethysmograph, and the subjects rebreathedbtps gas. Zrs,in and the relationship between Vpl and airway flow (Hpl) were measured from 4 to 29 Hz. Zaw and Zti were computed from Zrs,in and Hpl by using the monoalveolar T-network model and alveolar gas compliance derived from thoracic gas volume. The data were in good agreement with previous observations: airway and tissue resistance exhibited some positive and negative frequency dependences, respectively; airway reactance was consistent with an inertance of 0.015 ± 0.003 hPa ⋅ s2 ⋅ l−1and tissue reactance with an elastance of 36 ± 8 hPa/l. The changes seen with varying lung volume, during elastic loading of the chest and during bronchoconstriction, were mostly in agreement with the expected effects. The data, as well as computer simulation, suggest that the partitioning is unaffected by mechanical inhomogeneity and only moderately affected by airway wall shunting.

Frequency dependence of plethysmographic measurement of thoracic gas volume

1984 ◽  
Vol 57 (6) ◽  
pp. 1865-1871 ◽  
Author(s):  
R. Brown ◽  
A. S. Slutsky
Keyword(s):  
Frequency Dependence ◽  
Normal Subjects ◽  
Lung Capacity ◽  
Airways Obstruction ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
Mouth Pressure ◽  
Extrathoracic Airway ◽  
Shunt Capacitor ◽  
Gas Volume

With airways obstruction, panting frequency affects plethysmographically determined thoracic gas volume (Vtg) because the extrathoracic airway acts as a shunt capacitor. Stanescu et al. (19) suggested that in the calculation of Vtg, use of esophageal (delta Pes) rather than mouth pressure (delta Pm) swings might eliminate the problem. We measured total lung capacity (TLC) plethysmographically in 10 subjects with chronic airways obstruction (CAO) and in four normal subjects. TLC (using delta Pm) was derived from Vtg obtained from slow-(approximately 1 Hz) and fast- (approximately 4 Hz) panting frequencies. In the normal subjects and four subjects with CAO, TLC was also obtained using delta Pes. In these subjects abdominal gas compression and decompression did not contribute significantly to the frequency dependence of TLC. In CAO, TLC was frequency dependent in direct proportion to the severity of obstruction. Although the frequency dependence was greater using delta Pm to calculate Vtg, it also occurred using delta Pes. Thus it could not be explained entirely by the shunt capacitor effect of the extrathoracic airways. The residual and significant overestimations of TLC (reflected by frequency dependency of TLC derived from Vtg calculated from delta Pes) may be explained by interregional nonhomogeneities during the panting maneuver.

Influence of abdominal gas on the Boyle's law determination of thoracic gas volume

1978 ◽  
Vol 44 (3) ◽  
pp. 469-473 ◽  
Author(s):  
R. Brown ◽  
F. G. Hoppin ◽  
R. H. Ingram ◽  
N. A. Saunders ◽  
E. R. McFadden
Keyword(s):  
Vital Capacity ◽  
Relative Magnitude ◽  
Lung Capacity ◽  
Thoracic Gas Volume ◽  
Residual Capacity ◽  
Almost All ◽  
Gas Volume ◽  
Boyle’S Law ◽  
Different Levels

In a body plethysmograph we have demonstrated differences in total lung capacity (TLC) derived from panting maneuvers performed at different levels in the vital capacity. In almost all cases, the discrepancies were due to the magnitude of the abdominal gas volume (AGV) and the relative magnitude of abdominal and thoracic pressure swings during the panting mandeuver. When panting was performed at functional residual capacity (FRC), the effect of AGV compression on the determination of thoracid gas volume (TGV) was small. Of 11 individuals studied 2 were known to have mild asthma. Compression and decompression of AGV appeared to be an insufficient explanation for discrepancies in derived TLC's in these two, suggesting that other as yet unidentified factors may influence the plethysmographic determination of TGV.

In-brace alterations of pulmonary functions in adolescents wearing a brace for idiopathic scoliosis

2019 ◽  
Vol 43 (4) ◽  
pp. 434-439 ◽  
Author(s):  
Gozde Yagci ◽  
Gokhan Demirkiran ◽  
Yavuz Yakut
Keyword(s):  
Idiopathic Scoliosis ◽  
Pulmonary Function ◽  
Peak Expiratory Flow ◽  
Forced Vital Capacity ◽  
Respiratory Muscle ◽  
Vital Capacity ◽  
Forced Expiratory Volume ◽  
Pulmonary Functions ◽  
Significant Difference ◽  
Expiratory Flow

Background:Despite the common use of braces to prevent curve progression in idiopathic scoliosis, their functional effects on respiratory mechanics have not been widely studied.Objective:The objective was to determine the effects of bracing on pulmonary function in idiopathic scoliosis.Methods:A total of 27 adolescents with a mean age of 14.5 ± 1.5 years and idiopathic scoliosis were included in the study. Pulmonary function evaluation included vital capacity, forced expiratory volume, forced vital capacity, maximum ventilator volume, peak expiratory flow, and respiratory muscle strengths, measured with a spirometer, and patient-reported degree of dyspnea. The tests were performed once prior to bracing and at 1 month after bracing (while the patients wore the brace).Results:Compared with the unbraced condition, vital capacity, forced expiratory volume, forced vital capacity, maximum ventilator volume, and peak expiratory flow values decreased and dyspnea increased in the braced condition. Respiratory muscle strength was under the norm in both unbraced and braced conditions, while no significant difference was found for these parameters between the two conditions.Conclusion:The spinal brace for idiopathic scoliosis tended to reduce pulmonary functions and increase dyspnea symptoms (when wearing a brace) in this study. Special attention should be paid in-brace effects on pulmonary functions in idiopathic scoliosis.Clinical relevanceBracing seems to mimic restrictive pulmonary disease, although there is no actual disease when the brace is removed. This study suggests that bracing may result in a deterioration of pulmonary function when adolescents with idiopathic scoliosis are wearing a brace.

Airway anesthesia effects on hypercapnic breathing pattern in humans

1983 ◽  
Vol 55 (2) ◽  
pp. 368-376 ◽  
Author(s):  
T. Y. Sullivan ◽  
P. L. Yu
Keyword(s):  
Airway Resistance ◽  
Vital Capacity ◽  
Breathing Pattern ◽  
Minute Ventilation ◽  
Normal Subjects ◽  
Inspiratory Time ◽  
Abrupt Increase ◽  
Thoracic Gas Volume ◽  
Before And After ◽  
Gas Volume

Minute ventilation (VE) and breathing pattern during an abrupt increase in fractional CO2 were compared in 10 normal subjects before and after airway anesthesia. Subjects breathed 7% CO2-93% O2 for 5 min before and after inhaling aerosolized lidocaine. As a result of airway anesthesia, VE and tidal volume (VT) were greater during hypercapnia, but there was no effect on inspiratory time (TI). Therefore, airway anesthesia produced an increase in mean inspiratory flow (VT/TI) during hypercapnia. The increase in VT/TI was compatible with an increase in neuromuscular output. There was no effect of airway anesthesia on the inspiratory timing ratio or the shape and position of the curve relating VT and TI. We also compared airway resistance (Raw), thoracic gas volume, forced vital capacity, forced expired volume at 1s, and maximum midexpiratory flow rate before and after airway anesthesia. A small (0.18 cmH2O X l-1 X s) decrease in Raw occurred after airway anesthesia that did not correlate with the effect of airway anesthesia on VT/TI. We conclude that airway receptors accessible to airway anesthesia play a role in hypercapnic VE.

The Time-Course of Response to Prednisolone in Chronic Bronchial Asthma

1974 ◽  
Vol 47 (2) ◽  
pp. 105-117 ◽  
Author(s):  
R. Ellul-Micallef ◽  
R. C. Borthwick ◽  
G. J. R. McHardy
Keyword(s):  
Bronchial Asthma ◽  
Flow Rate ◽  
Time Course ◽  
Specific Conductance ◽  
Repeated Measurements ◽  
Maximum Effect ◽  
Thoracic Gas Volume ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow ◽  
Gas Volume

1. In six patients with stable chronic bronchial asthma, the effect of a single oral dose of 0.11 mmol (40 mg) of prednisolone was studied by carrying out repeated measurements of dynamic and static lung volumes, thoracic gas volume and airway resistance and maximum expiratory flow-volume curves. 2. No significant diurnal variation in the measurements performed was demonstrated on the 2 days before prednisolone was given. The administration of placebo tablets produced no significant change. 3. A statistically significant improvement was detectable 3 h after administration of the drug in the group of patients studied. The maximum effect was reached within 9–12 h, after which there was a return towards pretreatment values. 4. The improvement in specific conductance and maximum expiratory flow rate as well as in mid-expiratory flow rate suggests that the relief in airway obstruction occurred in both the large and the smaller airways. 5. The peak expiratory flow rate as measured by a Wright's peak flow meter proved to be as sensitive an index of change as any of the other tests employed.

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