Determination of functional residual capacity (FRC) by multibreath nitrogen washout in a lung model and in mechanically ventilated patients

1998 ◽  
Vol 24 (5) ◽  
pp. 487-493 ◽  
Author(s):  
H. Wrigge ◽  
M. Sydow ◽  
J. Zinserling ◽  
P. Neumann ◽  
J. Hinz ◽  
...  
Keyword(s):  
Functional Residual Capacity ◽  
Lung Model ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Nitrogen Washout ◽  
Residual Capacity ◽  
Ventilated Patients

Respiratory mechanics in mechanically ventilated patients with respiratory failure

1985 ◽  
Vol 58 (6) ◽  
pp. 1849-1858 ◽  
Author(s):  
A. Rossi ◽  
S. B. Gottfried ◽  
B. D. Higgs ◽  
L. Zocchi ◽  
A. Grassino ◽  
...  
Keyword(s):  
Time Constant ◽  
Inflation Rate ◽  
Respiratory Mechanics ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Airway Occlusion ◽  
The Relationship ◽  
Resistance Value ◽  
Ventilated Patients

In 11 mechanically ventilated patients, respiratory mechanics were measured 1) during constant flow inflation and 2) following end-inflation airway occlusion, as proposed in model analysis (J. Appl. Physiol. 58: 1840–1848, 1985. During the latter part of inflation, the relationship between driving pressure and lung volume change was linear, allowing determination of static respiratory elastance (Ers) and resistance (RT). The latter represents in each patient the maximum resistance value that can obtain with the prevailing time constant inhomogeneity. Following occlusion, Ers and RT were also obtained along with RT (min) which represents a minimum, i.e., resistance value that would obtain in the absence of time constant inhomogeneity. A discrepancy between inflation and occlusion Ers and RT was found only in the three patients without positive end-expiratory pressure, and could be attributed to recruitment of lung units during inflation. In all instances Ers and RT were higher than normal. RT(min) was lower in all patients than the corresponding values of RT, indicating that resistance was frequency dependent due to time constant inequalities. Changes in inflation rate did not affect Ers, while RT increased with increasing flow.

scholarly journals In vitro and in vivo functional residual capacity comparisons between multiple-breath nitrogen washout devices

2017 ◽  
Vol 3 (4) ◽  
pp. 00011-2017 ◽  
Author(s):  
Katrina O. Tonga ◽  
Paul D. Robinson ◽  
Claude S. Farah ◽  
Greg G. King ◽  
Cindy Thamrin
Keyword(s):  
Functional Residual Capacity ◽  
Measurement Accuracy ◽  
Lung Model ◽  
Nitrogen Washout ◽  
Device Validation ◽  
Residual Capacity

Functional residual capacity (FRC) accuracy is essential for deriving multiple-breath nitrogen washout (MBNW) indices, and is the basis for device validation. Few studies have compared existing MBNW devices. We evaluated in vitro and in vivo FRC using two commercial MBNW devices, the Exhalyzer D (EM) and the EasyOne Pro LAB (ndd), and an in-house device (Woolcock in-house device, WIMR).FRC measurements were performed using a novel syringe-based lung model and in adults (20 healthy and nine with asthma), followed by plethysmography (FRCpleth). The data were analysed using device-specific software. Following the results seen with ndd, we also compared its standard clinical software (ndd v.2.00) with a recent upgrade (ndd v.2.01).WIMR and EM fulfilled formal in vitro FRC validation recommendations (>95% of FRC within 5% of known volume). Ndd v.2.00 underestimated in vitro FRC by >20%. Reanalysis using ndd v.2.01 reduced this to 11%, with 36% of measurements ≤5%. In vivo differences from FRCpleth (mean±sd) were 4.4±13.1%, 3.3±11.8%, −20.6±11% (p<0.0001) and −10.5±10.9% (p=0.005) using WIMR, EM, ndd v.2.00 and ndd v.2.01, respectively.Direct device comparison highlighted important differences in measurement accuracy. FRC discrepancies between devices were larger in vivo, compared to in vitro results; however, the pattern of difference was similar. These results represent progress in ongoing standardisation efforts.

Functional residual capacity and ventilation homogeneity in mechanically ventilated small neonates

1992 ◽  
Vol 73 (1) ◽  
pp. 276-283 ◽  
Author(s):  
C. T. Vilstrup ◽  
L. J. Bjorklund ◽  
A. Larsson ◽  
B. Lachmann ◽  
O. Werner
Keyword(s):  
Functional Residual Capacity ◽  
Very Low Birth Weight ◽  
Lung Model ◽  
Tracer Gas ◽  
Low Birth Weight Infants ◽  
Mechanically Ventilated ◽  
O2 Concentration ◽  
Residual Capacity ◽  
Requirement Change ◽  
Washout Curves

A modification of a computerized tracer gas (SF6) washout method was designed for serial measurements of functional residual capacity (FRC) and ventilation homogeneity in mechanically ventilated very-low-birth-weight infants with tidal volumes down to 4 ml. The method, which can be used regardless of the inspired O2 concentration, gave accurate and reproducible results in a lung model and good agreement compared with He dilution in rabbits. FRC was measured during 2–4 cmH2O of positive end-expiratory pressure (PEEP) in 15 neonates (700–1,950 g), most of them with mild-to-moderate respiratory distress syndrome. FRC increased with body weight and decreased (P less than 0.05) with increasing O2 requirement. Change to zero end-expiratory pressure caused an immediate decrease in FRC by 29% (P less than 0.01) and gave FRC (ml) = -1.4 + 17 x weight (kg) (r = 0.83). Five minutes after PEEP was discontinued (n = 12), FRC had decreased by a further 16% (P less than 0.01). The washout curves indicated a near-normal ventilation homogeneity not related to changes in PEEP. This was interpreted as evidence against the presence of large volumes of trapped alveolar gas.

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