A respiratory function jacket for measuring tidal volume and changes in FRC

1983 ◽  
Vol 55 (1) ◽  
pp. 263-266 ◽  
Author(s):  
D. W. Cartwright ◽  
G. A. Gregory ◽  
M. M. Willis
Keyword(s):  
Tidal Volume ◽  
Functional Residual Capacity ◽  
Strain Gauge ◽  
Respiratory Function ◽  
Base Line ◽  
Simple Application ◽  
Mechanically Ventilated ◽  
Residual Capacity

We describe a simple application of a mercury-in-rubber strain gauge in a jacket used to measure tidal volume in paralyzed, mechanically ventilated rabbits. The jacket produces a record with a straight base line. Shifts of this base line can be used to assess changes in functional residual capacity (FRC).

Dynamic mechanisms determine functional residual capacity in mice, Mus musculus

1979 ◽  
Vol 46 (5) ◽  
pp. 867-871 ◽  
Author(s):  
A. Vinegar ◽  
E. E. Sinnett ◽  
D. E. Leith
Keyword(s):  
Tidal Volume ◽  
Functional Residual Capacity ◽  
Flow Volume ◽  
Linear Portion ◽  
Volume Curve ◽  
Flow Volume Curve ◽  
Residual Capacity ◽  
Expiratory Flow ◽  
The Difference ◽  
Pentobarbital Sodium Anesthesia

Awake mice (22.6--32.6 g) were anesthetized intravenously during head-out body plethysmography. One minute after pentobarbital sodium anesthesia, tidal volume had fallen from 0.28 +/- 0.04 to 0.14 +/- 0.02 ml and frequency from 181 +/- 20 to 142 +/- 8. Functional residual capacity (FRC) decreased by 0.10 +/- 0.02 ml. Expiratory flow-volume curves were linear, highly repeatable, and submaximal over substantial portions of expiration in awake and anesthetized mice; and expiration was interrupted at substantial flows that abruptly fell to and crossed zero as inspiration interrupted relaxed expiration. FRC is maintained at a higher level in awake mice due to a higher tidal volume and frequency coupled with expiratory braking (persistent inspiratory muscle activity or increased glottal resistance). In anesthetized mice, the absence of braking, coupled with reductions in tidal volume and frequency and a prolonged expiratory period, leads to FRCs that approach relaxation volume (Vr). An equation in derived to express the difference between FRC and Vr in terms of the portion of tidal volume expired without braking, the slope of the linear portion of the expiratory flow-volume curve expressed as V/V, the time fraction of one respiratory cycle spent in unbraked expiration, and respiratory frequency.

Estimation of pulmonary ventilation with nitrogen and helium, using the mass spectrometer

1959 ◽  
Vol 14 (4) ◽  
pp. 499-506 ◽  
Author(s):  
K. Tokuyasu ◽  
A. Coblentz ◽  
H. R. Bierman
Keyword(s):  
Tidal Volume ◽  
Mass Spectrometer ◽  
Functional Residual Capacity ◽  
Pulmonary Ventilation ◽  
Normal Subjects ◽  
Alveolar Ventilation ◽  
Pulmonary Lesions ◽  
Normal Subject ◽  
Residual Capacity ◽  
Uneven Ventilation

Estimation of pulmonary ventilation was attempted by measuring the elimination of nitrogen and helium with the mass spectrometer. Exhalatory concentrations of nitrogen and helium were continuously recorded in each of 12 normal subjects and 10 patients with pulmonary enphysema or space-occupying pulmonary lesions. Uniform values for both slow and rapid uneven ventilation were found in all normal subjects but always less than in emphysematous states. Ratios of effective tidal volume (Vt) and alveolar ventilation volume (f·Vt) to functional residual capacity P = Vt/Vr and Q = f·Vt/Vr were one half or less than those in the normal subject. Smaller values of uneven ventilation were found for helium than nitrogen. Data computed by the theory of 'periodic' ventilation gave greater values for uneven ventilation (Q) and more accurately represented the physiologic conditions than derived by ‘continuous’ ventilation. Submitted on August 7, 1958

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.

Pulmonary mechanics during rapid mechanical ventilation in rabbits with saline-lavaged lungs

1986 ◽  
Vol 61 (4) ◽  
pp. 1431-1437 ◽  
Author(s):  
J. J. Perez Fontan ◽  
B. S. Turner ◽  
G. P. Heldt ◽  
G. A. Gregory
Keyword(s):  
Tidal Volume ◽  
Gas Flow ◽  
Transpulmonary Pressure ◽  
Inspiratory Flow ◽  
Pulmonary Mechanics ◽  
Mechanically Ventilated ◽  
Ventilatory Rate ◽  
Residual Capacity ◽  
Pressure Volume Relationship ◽  
Linear Ramp

Infants with respiratory failure are frequently mechanically ventilated at rates exceeding 60 breaths/min. We analyzed the effect of ventilatory rates of 30, 60, and 90 breaths/min (inspiratory times of 0.6, 0.3, and 0.2 s, respectively) on the pressure-flow relationships of the lungs of anesthetized paralyzed rabbits after saline lavage. Tidal volume and functional residual capacity were maintained constant. We computed effective inspiratory and expiratory resistance and compliance of the lungs by dividing changes in transpulmonary pressure into resistive and elastic components with a multiple linear regression. We found that mean pulmonary resistance was lower at higher ventilatory rates, while pulmonary compliance was independent of ventilatory rate. The transpulmonary pressure developed by the ventilator during inspiration approximated a linear ramp. Gas flow became constant and the pressure-volume relationship linear during the last portion of inspiration. Even at a ventilatory rate of 90 breaths/min, 28–56% of the tidal volume was delivered with a constant inspiratory flow. Our findings are consistent with the model of Bates et al. (J. Appl. Physiol. 58: 1840–1848, 1985), wherein the distribution of gas flow within the lungs depends predominantly on resistive factors while inspiratory flow is increasing, and on elastic factors while inspiratory flow is constant. This dynamic behavior of the surfactant-depleted lungs suggests that, even with very short inspiratory times, distribution of gas flow within the lungs is in large part determined by elastic factors. Unless the inspiratory time is further shortened, gas flow may be directed to areas of increased resistance, resulting in hyperinflation and barotrauma.

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.

Ventilatory compensation for changes in functional residual capacity during sleep

1987 ◽  
Vol 62 (3) ◽  
pp. 1299-1306 ◽  
Author(s):  
R. L. Begle ◽  
J. B. Skatrud ◽  
J. A. Dempsey
Keyword(s):  
Tidal Volume ◽  
Functional Residual Capacity ◽  
Minute Ventilation ◽  
Muscle Length ◽  
Normal Subjects ◽  
Conscious State ◽  
Inspiratory Muscle ◽  
Compensatory Response ◽  
Inspiratory Muscles ◽  
Residual Capacity

The role of conscious factors in the ventilatory compensation for shortened inspiratory muscle length and the potency of this compensatory response were studied in five normal subjects during non-rapid-eye-movement sleep. To shorten inspiratory muscles, functional residual capacity (FRC) was increased and maintained for 2–3 min at a constant level (range of increase 160–1,880 ml) by creating negative pressure within a tank respirator in which the subjects slept. Minute ventilation was maintained in all subjects over the entire range of increased FRC (mean change +/- SE = -3 +/- 1%) through preservation of tidal volume (-2 +/- 2%) despite slightly decreased breathing frequency (-6 +/- 2%). The decrease in frequency (-13 +/- 2%) was due to a prolongation in expiratory time. Inspiratory time shortened (-10 +/- 1%). Mean inspiratory flow increased 15 +/- 3% coincident with an increase in the slope of the moving time average of the integrated surface diaphragmatic electromyogram (67 +/- 21%). End-tidal CO2 did not rise. In two subjects, control tidal volume was increased 35–50% with CO2 breathing. This augmented tidal volume was still preserved when FRC was increased. We concluded that the compensatory response to inspiratory muscle shortening did not require factors associated with the conscious state. In addition, the potency of this response was demonstrated by preservation of tidal volume despite extreme shortening of the inspiratory muscles and increase in control tidal volumes caused by CO2 breathing. Finally, the timing changes we observed may be due to reflexes following shortening of inspiratory muscle length, increase in abdominal muscle length, or cardiovascular changes.

Diaphragmatic function during immersion

1977 ◽  
Vol 43 (2) ◽  
pp. 297-301 ◽  
Author(s):  
V. D. Minh ◽  
G. F. Dolan ◽  
P. G. Linaweaver ◽  
P. J. Friedman ◽  
R. G. Konopka ◽  
...  
Keyword(s):  
Respiratory System ◽  
Functional Residual Capacity ◽  
Lung Volume ◽  
Intrathoracic Pressure ◽  
Fold Increase ◽  
Hydrostatic Compression ◽  
Base Line ◽  
Factors Affecting ◽  
Diaphragmatic Function ◽  
Residual Capacity

Diaphragmatic function during immersion to midneck level was studied in upright mongrel dogs, using constant electrophrenic stimulation. Effectiveness of diaphragmatic contraction was analyzed in terms of inspired volume (VT) (with airways open), and change in intrathoracic pressure (Pmus) (with the respiratory system occluded). Hydrostatic compression of the immersed body decreased functional residual capacity (FRC) to 55% base-line value (FRCO), resulting in a 2.8-fold increase in Pmus. In spite of this Pmus increase, VT often decreased during immersion, averaging only 83% VTO (base-line value in air). Hence, immersion was associated with a marked stiffening of the respiratory system. The Pmus increase during immersion persisted after restoration of FRC to FRCO, and was related to diaphragmatic length being greater in water than in air under condition of iso-lung volume. In all, there were three factors affecting diaphragmatic function during immersion: FRC reduction, change in thoracic configuration, and stiffening of the respiratory system.

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