Gas exchange during high-frequency ventilation of the chicken

1982 ◽  
Vol 53 (6) ◽  
pp. 1418-1422 ◽  
Author(s):  
R. B. Banzett ◽  
J. L. Lehr
Keyword(s):  
Gas Exchange ◽  
Tidal Volume ◽  
Dead Space ◽  
High Frequency ◽  
Conventional Mechanical Ventilation ◽  
High Frequency Ventilation ◽  
Tracheal Cannula ◽  
Bias Flow ◽  
Frequency Ventilation ◽  
Co2 Elimination

Recent studies have shown that high-frequency ventilation (HFV) at 1–30 Hz is capable of maintaining adequate gas exchange in humans and dogs even when tidal volumes are substantially less than dead space. We evaluated the effectiveness of HFV in roosters by comparing CO2 elimination during various frequencies and tidal volumes of HFV with CO2 elimination during conventional mechanical ventilation. Sinusoidal oscillations were applied at the tracheal cannula. A bias flow provided fresh gas at the top of the tracheal cannula. Three conclusions emerge from the data. 1) HFV enhances gas transport in the chicken as it does in mammals. 2) At low oscillatory flows (amplitude X frequency) CO2 elimination depends on both frequency and tidal volume, whereas at higher flows CO2 elimination depends more strongly on tidal volume. The flow at which this transition occurs is relatively lower than in humans and much lower than in dogs. 3) HFV at volumes below dead space is usually not capable of maintaining adequate gas exchange in the chicken in contrast to results in dogs and humans.

Physiological dead space during high-frequency ventilation in dogs

1984 ◽  
Vol 57 (3) ◽  
pp. 881-887 ◽  
Author(s):  
G. G. Weinmann ◽  
W. Mitzner ◽  
S. Permutt
Keyword(s):  
Gas Exchange ◽  
Tidal Volume ◽  
Dead Space ◽  
High Frequency ◽  
Minute Ventilation ◽  
Alveolar Ventilation ◽  
High Frequency Ventilation ◽  
Physiological Dead Space ◽  
Frequency Ventilation ◽  
Normal Ventilation

Tidal volumes used in high-frequency ventilation (HFV) may be smaller than anatomic dead space, but since gas exchange does take place, physiological dead space (VD) must be smaller than tidal volume (VT). We quantified changes in VD in three dogs at constant alveolar ventilation using the Bohr equation as VT was varied from 3 to 15 ml/kg and frequency (f) from 0.2 to 8 Hz, ranges that include normal as well as HFV. We found that VD was relatively constant at tidal volumes associated with normal ventilation (7–15 ml/kg) but fell sharply as VT was reduced further to tidal volumes associated with HFV (less than 7 ml/kg). The frequency required to maintain constant alveolar ventilation increased slowly as tidal volume was decreased from 15 to 7 ml/kg but rose sharply with attendant rapid increases in minute ventilation as tidal volumes were decreased to less than 7 ml/kg. At tidal volumes less than 7 ml/kg, the data deviated substantially from the conventional alveolar ventilation equation [f(VT - VD) = constant] but fit well a model derived previously for HFV. This model predicts that gas exchange with volumes smaller than dead space should vary approximately as the product of f and VT2.

Pulmonary gas exchange during high-frequency ventilation

1982 ◽  
Vol 52 (5) ◽  
pp. 1278-1287 ◽  
Author(s):  
R. D. McEvoy ◽  
N. J. Davies ◽  
F. L. Mannino ◽  
R. J. Prutow ◽  
P. T. Schumacker ◽  
...  
Keyword(s):  
Gas Exchange ◽  
High Frequency ◽  
Flow Distribution ◽  
Conventional Mechanical Ventilation ◽  
Inert Gas ◽  
High Frequency Ventilation ◽  
Concentration Difference ◽  
Perfused Lung ◽  
Frequency Ventilation ◽  
The Difference

Gas exchange was investigated in normal anesthetized dogs during high-frequency, low-tidal volume ventilation (HFV) using the multiple inert gas elimination method. The pattern of inert gas elimination was initially normal during conventional mechanical ventilation. During HFV there was an increase in the difference between the excretion values of acetone and its less soluble neighboring gases, enflurane and ether, but elimination was independent of molecular weight. This pattern was consistent with a major degree of parallel ventilation-perfusion inequality with 49.4 +/- 1.7% of alveolar ventilation being distributed to lung units with VA/Q ratios greater than 20. Additional experiments, however, showed insufficient change in pulmonary blood flow distribution during HFV to account for these apparently poorly perfused lung units. Instead, it was found that the flux from the lung of the most soluble gas, acetone, per unit concentration difference along the airways was approximately twice that for other gases. Experiments using a simple airway model suggested that this enhanced transport of high-solubility gases during HFV is dependent on the wet luminal surface of conducting airways. A reciprocating exchange of gas between the lumen and airway lining layer is proposed as the most likely explanation for these results.

Gas transport and pulmonary perfusion during high-frequency ventilation in humans

1984 ◽  
Vol 57 (4) ◽  
pp. 1231-1237 ◽  
Author(s):  
K. Rehder ◽  
E. P. Didier
Keyword(s):  
Gas Exchange ◽  
High Frequency ◽  
Regional Distribution ◽  
Vertical Gradient ◽  
Conventional Mechanical Ventilation ◽  
Pulmonary Gas Exchange ◽  
High Frequency Ventilation ◽  
Pulmonary Perfusion ◽  
Volume Ventilation ◽  
Frequency Ventilation

Regional pulmonary 133Xe clearances, regional 133Xe washins, regional distribution of pulmonary blood flow, and pulmonary gas exchange were determined during high-frequency small-volume ventilation (HFV, oscillation frequencies 12 or 18 Hz, stroke volumes 1.2–0.8 ml/kg) in six healthy anesthetized-paralyzed volunteers lying supine. Adequate pulmonary gas exchange was maintained by HFV; the efficiency of oxygenation during HFV did not differ significantly from that during conventional mechanical ventilation at similar mean lung volumes. During HFV regional pulmonary clearances and washins of tracer gas were different among regions. Apical nondependent lung regions cleared faster and had greater regional longitudinal gas conductances than did basal nondependent or dependent regions. The vertical gradient for pulmonary perfusion was preserved during HFV. Apparently the rate of interregional gas mixing is small during HFV at 12 and 18 Hz in anesthetized-paralyzed humans.

Effect of tracheal bias flow on gas exchange during high-frequency chest percussion

1987 ◽  
Vol 63 (1) ◽  
pp. 302-308 ◽  
Author(s):  
N. Gavriely ◽  
Y. Shabtai
Keyword(s):  
Gas Exchange ◽  
High Frequency ◽  
Gas Flow ◽  
High Frequency Ventilation ◽  
Control Group ◽  
Atmospheric Conditions ◽  
Bias Flow ◽  
Frequency Ventilation ◽  
Total Body ◽  
Tracheal Carina

High-frequency chest percussion (HFP) with constant fresh gas flow (VBF) at the tracheal carina is a variant of high-frequency ventilation (HFV) previously shown to be effective with extremely low tracheal oscillatory volumes (approximately 0.1 ml/kg). We studied the effects of VBF on gas exchange during HFP. In eight anesthetized and paralyzed dogs we measured arterial and alveolar partial pressures of CO2 (PaCO2) and O2 (PaO2) during total body vibration at a frequency of 30 Hz, amplitude of 0.17 +/- 0.019 cm, and tidal volume of 1.56 +/- 0.58 ml. VBF was incrementally varied from 0.1 to 1.2 l.kg-1.min-1. At low flows (0.1–0.4 l.kg-1.min-1), gas exchange was strongly dependent on flow rate but became essentially flow independent with higher VBF (i.e., hyperbolic pattern). At VBF greater than 0.4 l.kg-1.min-1, hyperventilatory blood gas levels were consistently sustained (i.e., PaCO2 less than 20 Torr, PaO2 greater than 90 Torr). The resistance to CO2 transport of the airways was 1.785 +/- 0.657 l-1.kg.min and was independent of VBF. The alveolar-arterial difference of O2 was also independent of the flow. In four of five additional dogs studied as a control group, where constant flow of O2 was used without oscillations, the pattern of PaCO2 vs. VBF was also hyperbolic but at substantially higher levels of PaCO2. It is concluded that, in the range of VBF used, intraairway gas exchange was limited by the 30-Hz vibration. The fresh gas flow was important only to maintain near atmospheric conditions at the tracheal carina.

CO2 elimination by high-frequency oscillations in dogs--effects of histamine infusion

1982 ◽  
Vol 53 (5) ◽  
pp. 1256-1262 ◽  
Author(s):  
T. H. Rossing ◽  
A. S. Slutsky ◽  
R. H. Ingram ◽  
R. D. Kamm ◽  
A. H. Shapiro ◽  
...  
Keyword(s):  
Gas Exchange ◽  
High Frequency ◽  
High Frequency Ventilation ◽  
Small Airways ◽  
Airway Constriction ◽  
High Frequency Oscillations ◽  
Frequency Ventilation ◽  
Control Study ◽  
Normal Lungs ◽  
Co2 Elimination

Effective gas exchange can be achieved in normal dogs by ventilation at frequencies of 4–20 Hz using stroke volumes (SV) smaller than the anatomic dead space. CO2 elimination is largely a function of tracheal SV-frequency product (Vosc) in anesthetized, paralyzed dogs with normal lungs. To determine the effect of constriction of small airways on gas exchange during such high-frequency ventilation (HFV), we ventilated five anesthetized, paralyzed, and vagotomized dogs via a tracheal cannula before and during intravenous histamine infusion. Vosc was varied by varying the frequency while keeping SV constant. For low Vosc, CO2 elimination (VCO2) increased directly with Vosc during control and histamine experiments. At high Vosc, VCO2 continued to increase directly with Vosc during the control study, but during histamine infusion VCO2 was lower than control values. Eucapnia could be maintained in each dog during HFV, even during airway constriction. During histamine infusion the frequency-dependent mechanical properties of the lung influence the delivery of the HFV SV to the respiratory zone, and this may explain the lower VCO2 observed.

Effect of high-frequency ventilation on lung mechanics at high transpulmonary pressure

1987 ◽  
Vol 63 (4) ◽  
pp. 1544-1550 ◽  
Author(s):  
G. G. Weinmann ◽  
Y. C. Huang ◽  
W. Mitzner
Keyword(s):  
Tidal Volume ◽  
High Frequency ◽  
Transpulmonary Pressure ◽  
Dynamic Compliance ◽  
Conventional Mechanical Ventilation ◽  
Lung Mechanics ◽  
High Frequency Ventilation ◽  
Group I ◽  
Frequency Ventilation ◽  
Group Ii

The different tidal volumes and frequencies of high-frequency ventilation (HFV) compared with conventional mechanical ventilation (CMV) may have different effects on lung mechanics. To test this hypothesis, we compared the effects of 3 h of HFV and CMV on total lung capacity (TLC), functional residual capacity (FRC), the shape of the pressure-volume (PV) curve (%V10), and dynamic compliance (Cdyn), as well as venous admixture and alveolar-arterial O2 gradient. We studied a total of 12 dogs at lung inflations equivalent to 15 cmH2O positive end-expiratory pressure (PEEP) (group I) and 8 dogs at lung inflations equivalent to 0 cmH2O PEEP (group II). For CMV, we used a standard-volume ventilator at a mean tidal volume of 13.8 ml/kg. For HFV, we used an oscillator-type ventilator at 15 Hz and an average tidal volume of 4.3 ml/kg. Our results showed that ventilation with 3 h of PEEP raised lung volume, and lung volumes on HFV were higher than those on CMV in both groups. Specifically, in group I, the volume during ventilation rose on both CMV (150 ml) and HFV (250 ml). These volume changes persisted beyond the ventilation period, such that TLC was unchanged on CMV but had risen 200 ml on HFV. FRC also rose 200 and 300 ml after HFV and CMV, respectively. In group II, the volume during ventilation fell 100 ml on CMV and rose slightly (40 ml) on HFV. TLC and FRC both tended to fall more on CMV.(ABSTRACT TRUNCATED AT 250 WORDS)

High-frequency ventilation of ducks and geese

1987 ◽  
Vol 63 (1) ◽  
pp. 413-417 ◽  
Author(s):  
R. H. Hastings ◽  
F. L. Powell
Keyword(s):  
Gas Exchange ◽  
High Frequency ◽  
Minute Ventilation ◽  
Control Ventilation ◽  
High Frequency Ventilation ◽  
Opening Pressure ◽  
Arterial Pco2 ◽  
Bias Flow ◽  
Airway Opening ◽  
Frequency Ventilation

We studied gas exchange in anesthetized ducks and geese artificially ventilated at normal tidal volumes (VT) and respiratory frequencies (fR) with a Harvard respirator (control ventilation, CV) or at low VT-high fR using an oscillating pump across a bias flow with mean airway opening pressure regulated at 0 cmH2O (high-frequency ventilation, HFV). VT was normalized to anatomic plus instrument dead space (VT/VD) for analysis. Arterial PCO2 was maintained at or below CV levels by HFV with VT/VD less than 0.5 and fR = 9 and 12 s-1 but not at fR = 6 s-1. For 0.4 less than or equal to VT/VD less than or equal to 0.85 and 3 s-1. less than or equal to fR less than or equal to 12 s-1, increased VT/VD was twice as effective as increased fR at decreasing arterial PCO2, consistent with oscillatory dispersion in a branching network being an important gas transport mechanism in birds on HFV. Ventilation of proximal exchange units with fresh gas due to laminar flow is not the necessary mechanism supporting gas exchange in HFV, since exchange could be maintained with VT/VD less than 0.5. Interclavicular and posterior thoracic air sac ventilation measured by helium washout did not change as much as expired minute ventilation during HFV. PCO2 was equal in both air sacs during HFV. These results could be explained by alterations in aerodynamic valving and flow patterns with HFV. Ventilation-perfusion distributions measured by the multiple inert gas elimination technique show increased inhomogeneity with HFV. Elimination of soluble gases was also enhanced in HFV as reported for mammals.(ABSTRACT TRUNCATED AT 250 WORDS)

TIDAL VOLUME DEAD-SPACE RELATIONSHIP DURING HIGH-FREQUENCY VENTILATION

The Lancet ◽  
1983 ◽  
Vol 322 (8363) ◽  
pp. 1360 ◽  
Author(s):  
J.G. Whitwam ◽  
M.K. Chakrabarti ◽  
G. Gordon
Keyword(s):  
Tidal Volume ◽  
Dead Space ◽  
High Frequency ◽  
High Frequency Ventilation ◽  
Frequency Ventilation

Quantitative evaluation of pulmonary stretch receptor activity during high-frequency ventilation

1992 ◽  
Vol 72 (3) ◽  
pp. 1101-1110 ◽  
Author(s):  
S. L. Thompson-Gorman ◽  
R. S. Fitzgerald ◽  
W. Mitzner
Keyword(s):  
Tidal Volume ◽  
High Frequency ◽  
Conventional Mechanical Ventilation ◽  
High Frequency Ventilation ◽  
Absolute Amount ◽  
Pulmonary Stretch Receptors ◽  
Frequency Ventilation ◽  
The Brain ◽  
Specific Contribution ◽  
Pulmonary Stretch Receptor

The purpose of this study was to determine the neural output of pulmonary stretch receptors (PSRs) in response to conditions that, in previous studies (J. Appl. Physiol. 65: 179–186, 1988 and Respir. Physiol. 80: 307–322, 1990), produced apnea in anesthetized cats. These conditions included changes in airway pressure (Paw; 2 or 6 cmH2O), stroke or tidal volume (1–4 ml/kg), frequency [conventional mechanical ventilation (CMV) vs. high-frequency ventilation (HFV) at 10, 15, and 20 Hz], and levels of inspired CO2 (0, 2, and 5%). These data were needed to assess properly the specific contribution of the PSRs to the apnea found with certain combinations of the above variables. Each PSR was subjected to HFV over a range of mechanical and chemical settings, and its activity was recorded. PSRs exhibited continuous activity associated with pump stroke in 11 of 12 fibers tested. PSRs fired more rapidly when mean Paw was 6 cmH2O [45.3 +/- 0.8 (SE) impulses/s] than when it was 2 cmH2O (31.7 +/- 0.9 impulses/s, P = 0.0001). At both pressures, PSR activity increased as the volume of inflation, or tidal volume, was increased from 1 to 4 ml/kg. At Paw of 2 cmH2O, the number of impulses per second for HFV was not different from that for CMV (averaged over the respiratory cycle), under conditions previously demonstrated as apneogenic for both modes of ventilation. Therefore the absolute amount of information being sent to the brain stem processing centers via PSRs during HFV did not differ from that during CMV. Thus any PSR contribution to HFV-induced apnea must have been the result of changes in the pattern of the signal or the central nervous system's processing of it rather than an increase in the amount of inhibitory afferent signal.

Model of gas transport during high-frequency ventilation

1985 ◽  
Vol 58 (6) ◽  
pp. 1956-1970 ◽  
Author(s):  
S. Permutt ◽  
W. Mitzner ◽  
G. Weinmann
Keyword(s):  
Standard Deviation ◽  
Gas Exchange ◽  
Dead Space ◽  
High Frequency ◽  
Mean Transit Time ◽  
High Frequency Ventilation ◽  
Transit Times ◽  
Frequency Ventilation ◽  
In Series ◽  
The Dead

We analyze gas exchange during high-frequency ventilation (HFV) by a stochastic model that divides the dead space into N compartments in series where each compartment has a volume equal to tidal volume (V). We then divide each of these compartments into alpha subcompartments in series, where each subcompartment receives a well-mixed concentration from one compartment and passes a well-mixed concentration to another in the direction of flow. The number of subcompartments is chosen on the basis that 1/alpha = (sigma t/-t)2, where -t is mean transit time across a compartment of volume, and sigma t is standard deviation of transit times. If (sigma t/-t)D applies to the transit times of the entire dead space, the magnitude of gas exchange is proportional to (sigma t/-t)D, frequency, and V raised to some power greater than unity in the range where V is close to VD. When V is very small in relation to VD, gas exchange is proportional to (sigma t/-t)2D, frequency, and V raised to a power equal to either one or two depending on whether the flow is turbulent or streamline, respectively. (sigma t/-t)D can be determined by the relation between the concentration of alveolar gas at the air outlet and volume expired as in a Fowler measurement of the volume of the dead space.

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