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.

scholarly journals Accurate Measurement of Functional Residual Capacity and Oxygen Consumption of Patients on Mechanical Ventilation

1983 ◽  
Vol 11 (2) ◽  
pp. 151-157 ◽  
Author(s):  
Kevin R. Cooper ◽  
Peter A. Boswell
Keyword(s):  
Intensive Care Unit ◽  
Mechanical Ventilation ◽  
Intensive Care ◽  
Oxygen Consumption ◽  
Functional Residual Capacity ◽  
Lung Model ◽  
Capacity Measurement ◽  
Icu Patients ◽  
Residual Capacity

We developed an apparatus and technique for the simultaneous measurement of functional residual capacity and oxygen uptake (V̇O2) for use in intensive care unit (ICU) patients. The accuracy of the functional residual capacity measurement was proven using an in vitro lung model and the reproducibility of this measurement was established by use in ICU patients. We tested the accuracy of the V̇O2 measurement in comparison with two other methods in common use among ICU patients and our method proved accurate. We conclude that this technique for measurement of functional residual capacity and V̇O2 is highly accurate and easily applied to patients on any mode of mechanical ventilation.

Positive end-expiratory pressure enhances development of a functional residual capacity in preterm rabbits ventilated from birth

2009 ◽  
Vol 106 (5) ◽  
pp. 1487-1493 ◽  
Author(s):  
Melissa L. Siew ◽  
Arjan B. te Pas ◽  
Megan J. Wallace ◽  
Marcus J. Kitchen ◽  
Robert A. Lewis ◽  
...  
Keyword(s):  
Functional Residual Capacity ◽  
Positive End Expiratory Pressure ◽  
Mechanically Ventilated ◽  
Very Preterm ◽  
Lung Aeration ◽  
X Ray Imaging ◽  
Airway Collapse ◽  
Distal Airway ◽  
Dead Space Volume ◽  
Residual Capacity

The factors regulating lung aeration and the initiation of pulmonary gas exchange at birth are largely unknown, particularly in infants born very preterm. As hydrostatic pressure gradients may play a role, we have examined the effect of a positive end-expiratory pressure (PEEP) on the spatial and temporal pattern of lung aeration in preterm rabbit pups mechanically ventilated from birth using simultaneous phase-contrast X-ray imaging and plethysmography. Preterm rabbit pups were delivered by caesarean section at 28 days of gestational age, anesthetized, intubated, and placed within a water-filled plethysmograph (head out). Pups were imaged as they were mechanically ventilated from birth with a PEEP of either 0 cmH2O or 5 cmH2O. The peak inflation pressure was held constant at 35 cmH2O. Without PEEP, gas only entered into the distal airways during inflation. The distal airways collapsed during expiration, and, as a result, the functional residual capacity (FRC) did not increase above the lung's anatomic dead space volume (2.5 ± 0.8 ml/kg). In contrast, ventilation with 5-cmH2O PEEP gradually increased aeration of the distal airways, which did not collapse at end expiration. The FRC achieved in pups ventilated with PEEP (19.9 ± 3.2 ml/kg) was significantly greater than in pups ventilated without PEEP (−2.3 ± 3.5 ml/kg). PEEP greatly facilitates aeration of the distal airways and the accumulation of FRC and prevents distal airway collapse at end expiration in very preterm rabbit pups mechanically ventilated from birth.

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.

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