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PubMed1976

Measurement of 'closing volume' initiated from functional residual capacity.

Comparison of the nitrogen method closing volume (CV) test, with oxygen inspiration initiated at residual volume (RV method) and functional residual capacity (FRC method), was made in 91 seated normal subjects. For RV and FRC methods, respectively CV%VC (mean+/-SD) was 14.4% (+/-6.2) and 17.5%(+/-7.5) (P=0.005); slope of Phase III of CV trace was 0.99% N2/1 (+/-0.76) and 1.66% N2/1(+/-1.07) (P=0.005); size of cardiogenic oscillations was 1.05% N2(+/-0.42) and 1.21% N2(+/-0.40) (P=0.001). These data confirm earlier predictions, based on a calculated increased lung top to bottom N2 gradient in the FRC method. Support for this mechanism was obtained in 5 additional normal subjects in whom the increased CV%VC, slope of Phase III and size of cardiogenic oscillations with the FRC method were eliminated when the top-to-bottom N2 gradient was reduced by breathing a reduced FIN2. Measurements made using the classical RV method cannot be directly compared to those using the FRC method.

Adult↗
PubMed1975

"Closing volume" changes in alloxan-induced pulmonary edema in anesthetized dogs.

"Closing volume" (CV) was measured by the single-breath oxygen (SBO2) test in six dogs (alloxan group) before and after alloxan 100-200 mg/kg iv) was injected. CV increased significantly (P less than 0.05) from 32 +/- 3.2% (base line) to 45 +/- 3.5 % in period 1 (0-30 min after alloxan), but vital capacity (VC), respiratory system pressure volume (PV) curves, and alveolar plateau slopes did not change. No radiologic evidence of pulmonary edema was demonstrated in two dogs studied in period 1. CV decreased to 20 +/- 3.9% during period 2 (30-80 min after alloxan) and was associated with tracheal frothing, decreased VC, changes in the PV curve, and alveolar plateau slope, as well as histologic evidence of severe pulmonary edema. CV was 29 +/- 3.0%, and there were no changes in VC, PV curves, or alveolar plateau slopes in 6 other dogs studied for 2 h (control group). CV increased during period 1 before pulmonary edema could be demonstrated by changes in VC, PV curves, or radiography, but in period 2 lung function was so altered that CV by the SBO2 technique gave no useful information.

Alloxan↗
PubMed1989

Single and multiple breath nitrogen wash-out--closing volume and volume of trapped gas for detection of early airway obstruction.

Thirty-eight patients with varying degrees of peripheral airway involvement were studied by flow-volume curves and two nitrogen wash-out techniques in an on-site study. Closing capacity (CC), closing volume in percentage of vital capacity (CV%), slope of the alveolar plateau (phase III), volume of trapped gas (VTG), and maximum expiratory flow at 50 and 75% of vital capacity (MEF50, MEF25) were determined and correlation analyses were performed. A biphasic or exponential correlation was noted between the degree of airway closure and VTG with rapidly increasing VTG at high CC. Although there were correlations between spirometry and the two nitrogen wash-out techniques, a large scatter precluded the use of the flow-volume variables to predict CC, CV% and VTG. The coefficient of variation was lower for the measurements of CV% than for the recording of VTG. Since the single breath nitrogen wash-out technique is also technically simpler it is recommended prior to the multiple breath technique.

Adult↗
PubMed1975

A simplified method for measuring helium closing volume.

A simple method for delivering a constant volume of helium for the measurement of airway closing volume is described. Using a standard fiveway valve and PVC plastic irrigation pipe, a device was constructed which permits the delivery of a uniform volume of helium and avoids the troublesome valve change during inspiration. Results obtained when using this device were comparable to those with the use of conventional bag to contain the helium.

Helium↗
PubMed1992

Single-breath, room-air method for measuring closing volume (phase 4) in the normal human lung.

The purpose of this study was to evaluate a new method to measure closing volume (CV). This new method does not require oxygen or inert gases to be inhaled to obtain the onset of phase 4. Because there are regional differences in the concentrations of the resident alveolar gases (O2, CO2, and N2), there should be an abrupt change in the concentration of these gases at the terminal portion of a prolonged expired vital capacity (VC) that marks the onset of phase 4. Nine normal healthy subjects, 30 to 65 years of age, inspired room air from residual volume (to mimic the maneuver of the standard single breath N2 (SBN2) washout test) to total lung capacity. During the expiration (flow constant at 250 ml.s-1) following a 10-s breath hold at total lung capacity, the exhaled gas was analyzed with a mass spectrometer for fractions of O2, CO2, and N2. Although the onset of phase 4 can be shown as the change in concentration of any of the three alveolar resident gases, oxygen was selected because (1) it demonstrates a greater apex to base concentration gradient than that found with CO2 and N2, and (2) a clear identification of the onset of phase 4 (minimum value of O2 fraction). With this method, the mean +/- SEM of CV was 16.8 +/- 1.52 percent (CV x 100/VC). No significant difference was found among the room air method, SBN2 method, and the helium bolus technique.

Adult↗
PubMed1977

[Effect of beta-adrenergic stimulation on the closing volume in normal subjects (author's transl].

In 12 normal subjets we studies the effects of beta-adrenergic stimulation (Salbutamol, 500 microgram inhaled) on the closing volume (CV) and the closing capacity and on the ratios of these indexes to the vital capacity (VC) and the total lung capacity, respectively. CV and CV/VC % increased in ten subjects wereas it decreased in two subjects. On an average, the changes were small but significant (p less than 0.01) and could be duplicated in four subjects. Similar studies have yielded variable results. The reasons for those variation could be attributed either to technical or/and individual differences in the resulting effect of beta stimulation on respiratory mechanics.

Adrenergic beta-Agonists↗
PubMed1998

Ventilation above closing volume reduces pulmonary vascular resistance hysteresis.

The aim of this study was to determine the relationship of pulmonary vascular resistance (PVR) hysteresis and lung volume, with special attention to the effects of ventilation around closing volume (CV). Isolated, blood-perfused canine left lower lung lobes (LLL) were incrementally inflated and deflated. Airway and pulmonary artery pressures (PAP) were recorded after each stepwise volume change. Constant blood flow was provided (600 ml/min) and the pulmonary vein pressure (PVP) was held constant at 5 cm H2O. PAP changes, therefore, were a direct index of PVR changes. Group 1 lobes underwent a full inflation from complete collapse to total lobe capacity (TLC) followed by a full deflation. Group 2 lobes underwent two deflation/inflation cycles, after an initial full inflation. These cycles, both beginning at TLC, had deflation end above and below CV, respectively. Significant PVR hysteresis was noted when the first inflation and deflation were compared. The maximum difference in PAP on deflation was 3.3 cm H2O or 11%. The mean decrease was 2.7 cm H2O for 18 lobes (p < 0.0001). The PAPs on all subsequent inflations or deflations that began above CV remained 9% lower than the initial inflation (n = 9, p < 0.0001), but were not different from each other. However, the final inflation which began from below CV resulted in a 30% return of PVR hysteresis (mean increase in PAP of 0.8 cm H2O, n = 7, p < 0.004). We conclude that there is hysteresis in the PVR response during ventilation, with decreased PVR during deflation relative to the initial inflation, that this hysteresis is absent when lung volume is maintained greater than CV, and that hysteresis returns when inflation occurs after deflation below CV.

Air Pressure↗
PubMed1994

Effects of age on closing volume during head-out water immersion.

Previous studies during head-out immersion have shown closing volume (CV) to either increase or remain unchanged. We hypothesized that these inconclusive results might be related to differences in the ages of the subjects tested. To elucidate this we studied single-breath argon washout tests performed by a younger group (n = 8, age 23-26) and an older group (n = 8, age 40-54) of males every 5 min during 30 min of seated, thermoneutral head-out immersion. No temporal changes in CV during immersion were observed in either group, therefore values within each group during immersion were combined. In the younger group, CV increased 77% (dry, 0.26 +/- 0.11 L; wet, 0.46 +/- 0.10 L; delta = 0.20 L) (P < 0.001) but remained less than the tidal breathing range upper limit [expiratory reserve volume + tidal volume (ERV + VT)]. In the older group, CV increased 34% (dry, 0.83 +/- 0.29 L; wet, 1.11 +/- 0.19 L; delta = 0.28 L) (P < 0.05) and was not different from ERV + VT. The absolute increase in CV during immersion did not differ between the groups. ERV decreased during immersion in both groups and was lower in the older than younger group (P < 0.001). Alveolar plateau (phase III) slope became steeper in the younger (P < 0.001) but not in the older group. We conclude that during immersion: (1) The absolute increase in CV is independent of age, and (2) in subjects over 40, CV approaches the highest lung volumes reached during tidal breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1975

[Determination of the closing volume and its value in the early detection of chronic obstructive lung disease].

The determination of the closing volume appears as a good test for the early detection of obstructive lung diseases and of disorders in the ventilation distribution. Easy to perform, its use should become extensive. To make use of this investigation under the better possible conditions, it is strictly necessary to respect methodologic norms and an excellent technology and to be aware of some morphologic anomalies in the curves.

Age Factors↗
PubMed1988

"Closing volume" during high-frequency ventilation in anesthetized dogs.

Airway closure, mean airway pressure, gas exchange and different modes of artificial ventilation were investigated in anesthetized and paralyzed dogs with clinically healthy lungs. The animals were ventilated with either intermittent positive pressure ventilation (IPPV), continuous positive pressure ventilation (GPPV, positive end-expiratory pressure (PEEP) = 0.49 kPa) or high-frequency jet ventilation (HFJV, open system) of 2 and 30 Hz with an inspiratory to expiratory (I/E) - ratio of 30/70 and 60/40. Closing volume (CV) was determined by a modified technique, submitting the lung to constant subatmospheric pressure after an inspiratory vital capacity of oxygen. Two different tests for CV were used: the foreign gas bolus (FGB) with helium as nonresident gas and the single breath nitrogen dilution technique (SBO2). During conventional mechanical ventilation, CV decreased significantly (P less than 0.05) after establishing a PEEP of 0.49 kPa. During HFJV, CV increased significantly (P less than 0.01). This effect was predominantly dependent on I/E duration time ratio and to a lesser extent on ventilatory frequency. There were significant differences between CV obtained by the FGB-method (CV(helium] and CV derived from the SBO2-test (CV(SBO2], although both tests revealed the same proportional changes of CV during the different modes of ventilation. The elevated CV was associated with a decreasing Pao2 and increasing Aa-Do2 and Paco2, indicating substantial hypoventilation and mismatching of ventilation and perfusion. Mean airway pressure increased with both CPPV and HFJV, revealing a dissociation between airway pressure and regional FRC distribution during HFJV. It is concluded that certain modes of high-frequency ventilation lead to impaired distribution of inspired gas to dependent lung regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Intravenous↗
PubMed1979

[Closing volume].

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Closing Volume↗
PubMed1977

[Increased closing volume in asymptomatic respiratory sarcoidosis].

In 21 patients with asymptomatic respiratory sarcoidosis, 11 with hilar lymph node enlargement (stage I) and 10 with both hilar and lung involvement (stage II), pulmonary function tests revealed that the closing volume was increased as compared with control values obtained from healthy individuals of the same age and smoking habits. The difference was statistically significant but more pronounced in stage II patients than in stage I patients. Other function tests were normal (VC, FEV1, MMF, RV, TLC, DLCOSB).

Adult↗