High-frequency ventilation-induced apnea: interaction of frequency, volume, FRC, and CO2

1989 ◽  
Vol 66 (5) ◽  
pp. 2462-2467 ◽  
Author(s):  
P. W. Davenport ◽  
D. J. Dalziel
Keyword(s):  
High Frequency ◽  
Blood Gas Analysis ◽  
Gas Analysis ◽  
High Frequency Ventilation ◽  
Emg Activity ◽  
Bipolar Electrodes ◽  
Residual Capacity ◽  
Frequency Ventilation ◽  
Anesthetized Dogs ◽  
End Tidal

Apnea is often observed during high-frequency oscillatory ventilation (HFOV). This study on anesthetized dogs varied the oscillator frequency (f) and determined the stroke volume (SV) at which apnea occurred. Relaxation functional residual capacity (FRC) and the eupneic breathing end-tidal CO2 level were held constant. Airway pressure and CO2 were measured from a side port of the tracheostomy cannula. An arterial cannula was inserted for blood gas analysis. Diaphragm electromyogram (EMG) was recorded with bipolar electrodes. Apnea was defined as the absence of phasic diaphragm EMG activity for a minimum of 60 s. During HFOV, SV was increased at each f (5–40 Hz) until apnea occurred. The apnea inducing SV decreased as f increased. SV was minimal at 25–30 Hz. Frequencies greater than 30 Hz required increased SV to produce apnea. The f-SV curve was defined as the apneic threshold. Increased FRC resulted in a downward shift (less SV at the same f) in the apneic threshold. Elevated CO2 caused an upward shift (more SV at the same f) in the apneic threshold. These results demonstrate that the apnea elicited by HFOV is dependent on the interaction of oscillator f and SV, the FRC, and CO2.

Pulmonary afferent activity during high-frequency ventilation at constant mean lung volume

1986 ◽  
Vol 61 (1) ◽  
pp. 192-197 ◽  
Author(s):  
G. M. Barnas ◽  
R. B. Banzett ◽  
M. B. Reid ◽  
J. Lehr
Keyword(s):  
Lung Volume ◽  
High Frequency ◽  
High Frequency Ventilation ◽  
Afferent Activity ◽  
Stretch Receptors ◽  
Pulmonary Stretch Receptors ◽  
Normal Frequency ◽  
Residual Capacity ◽  
Frequency Ventilation ◽  
End Tidal

We recorded the responses of 21 slowly adapting pulmonary stretch receptors (PSRs) and 8 rapidly adapting pulmonary stretch receptors (RARs) from the vagi of anesthetized open-chest dogs to high-frequency ventilation (HFV) at 15 Hz, at constant mean end-expiratory lung volume, and constant end-tidal PCO2. HFV applied in this way has been shown to prolong expiration. The responses of pulmonary afferents during HFV at constant mean volume have not been described. In the present experiments, receptor discharge during HFV was compared with that during the end-expiratory pause of normal-frequency ventilation. Average PSR discharge increased when HFV was applied, although not all PSRs exhibited increases. RARs were generally silent during normal and high-frequency ventilation at functional residual capacity and above. However, at low lung volumes, RAR discharge increased greatly when HFV was applied. We conclude that PSR discharge is increased during HFV in the absence of increased lung volume and that increases in PSR discharge during HFV are sufficient to explain the reflex that prolongs expiration in dogs.

High-frequency ventilation lengthens expiration in the anesthetized dog

1983 ◽  
Vol 55 (2) ◽  
pp. 329-334 ◽  
Author(s):  
R. Banzett ◽  
J. Lehr ◽  
B. Geffroy
Keyword(s):  
Lung Volume ◽  
High Frequency ◽  
Blood Gases ◽  
Abdominal Muscle ◽  
High Frequency Ventilation ◽  
Maximal Response ◽  
Variable Effect ◽  
Frequency Ventilation ◽  
Anesthetized Dogs ◽  
Arterial Po2

We tested the response of nine barbiturate-anesthetized dogs to high-frequency ventilation (HFV) (40-55 ml tidal volumes at 15 Hz) while measuring and controlling lung volume and blood gases. When lung volume and PCO2 were held constant, six of the nine responded to HFV by lengthening expiration. In each of these six dogs the maximal response was apnea. The response was immediate. In submaximal responses only expiration was changed; inspiratory time and peak diaphragmatic electrical activity were unaffected. There was a variable effect on abdominal muscle activity. If mean expiratory lung volume was allowed to increase at the onset of HFV, the Hering-Breuer inflation reflex added to the response. The strength of the response depended on level of anesthesia and arterial PO2. Vagotomy abolished the response in all cases. We conclude that oscillation of the respiratory system reflexly prolongs expiration via mechanoreceptors, perhaps those in the lungs.

Expiratory flow limitation and dynamic pulmonary hyperinflation during high-frequency ventilation

1986 ◽  
Vol 60 (6) ◽  
pp. 2071-2078 ◽  
Author(s):  
J. Solway ◽  
T. H. Rossing ◽  
A. F. Saari ◽  
J. M. Drazen
Keyword(s):  
High Frequency ◽  
Progressive Increase ◽  
High Frequency Ventilation ◽  
Dynamic Hyperinflation ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Pulmonary Hyperinflation ◽  
Residual Capacity ◽  
Frequency Ventilation ◽  
Expiratory Flow

Dynamic hyperinflation of the lungs occurs during high-frequency oscillatory ventilation (HFOV) and has been attributed to asymmetry of inspiratory and expiratory impedances. To identify the nature of this asymmetry, we compared changes in lung volume (VL) observed during HFOV in ventilator-dependent patients with predictions of VL changes from electrical analogs of three potential modes of impedance asymmetry. In the patients, when a fixed oscillatory tidal volume was applied at a low mean airway opening pressure (Pao), which resulted in little increase in functional residual capacity, progressively greater dynamic hyperinflation was observed as HFOV frequency, (f) was increased. When mean Pao was raised so that resting VL increased, VL remained at this level during HFOV as f was increased until a critical f was reached; above this value, VL increased further with f in a fashion nearly parallel to that observed when low mean Pao was used. Three modes of asymmetric inspiratory and expiratory impedance were modeled as electrical circuits: 1) fixed asymmetric resistance [Rexp greater than Rinsp]; 2) variable asymmetric resistance [Rexp(VL) greater than Rinsp, with Rexp(VL) decreasing as VL increased]; and 3) equal Rinsp and Rexp, but with superimposed expiratory flow limitation, the latter simulated using a bipolar transistor as a descriptive model of this phenomenon. The fixed and the variable asymmetric resistance models displayed a progressive increase of mean VL with f at either low or high mean Pao. Only the expiratory flow limitation model displayed a dependence of dynamic hyperinflation on mean Pao and f similar to that observed in our patients. We conclude that expiratory flow limitation can account for dynamic pulmonary hyperinflation during HFOV.

Costal and crural diaphragm function during panting in awake canines

1994 ◽  
Vol 77 (4) ◽  
pp. 1983-1990 ◽  
Author(s):  
P. A. Easton ◽  
T. Abe ◽  
R. N. Young ◽  
J. Smith ◽  
A. Guerraty ◽  
...  
Keyword(s):  
High Frequency ◽  
Minute Ventilation ◽  
Respiratory Muscles ◽  
Thermal Regulation ◽  
High Frequency Ventilation ◽  
Emg Activity ◽  
Dry Heat ◽  
Frequency Ventilation ◽  
Crural Diaphragm ◽  
Segmental Function

During natural panting for thermal regulation, the pattern of activation of the major respiratory muscles, including costal and crural diaphragm segments, is not known. We measured diaphragm segmental length, shortening, and electromyographic (EMG) activity in five chronically implanted canines awake and breathing spontaneously at rest and during a mild dry heat stress. During panting, minute ventilation increased fourfold from 5.07 l/min and respiratory rate increased from 16.9 to 192.8 breaths/min or 3.2 Hz. During panting, end-expiratory length of both costal and crural segments decreased, concurrent with significant increases in end-expiratory EMG. With the onset of panting, tidal costal shortening decreased significantly from 6.29% of end-expiratory length to 3.54%, whereas crural shortening decreased from 6.04 to 2.46%. Meanwhile, segmental EMG tended to increase during panting. During panting, intrabreath costal and crural segmental function revealed differential activation; the costal segment shortened in concert with inspiratory flow, whereas peak crural shortening occurred in expiration, almost 180 degrees out of phase with costal. The divergence in segmental shortening during panting was accompanied by a lesser shift in timing of segmental EMG. In the awake spontaneously panting canine, asynchronous costal and crural shortening may enhance gas mixing in a manner analogous to high-frequency ventilation.

Ventilation-perfusion relationship during high-frequency ventilation

1984 ◽  
Vol 56 (2) ◽  
pp. 454-458 ◽  
Author(s):  
V. Brusasco ◽  
T. J. Knopp ◽  
E. R. Schmid ◽  
K. Rehder
Keyword(s):  
Mechanical Ventilation ◽  
High Frequency ◽  
Conventional Mechanical Ventilation ◽  
Regional Perfusion ◽  
High Frequency Ventilation ◽  
Regional Ventilation ◽  
Frequency Ventilation ◽  
Anesthetized Dogs

The efficiency of oxygenation and the uniformity of the distribution of regional ventilation (Vr) to regional perfusion (Qr) along the vertical and horizontal axes was compared in anesthetized dogs between conventional mechanical ventilation (CMV) and high-frequency ventilation (HFV) at 5.8, 15.0, and 29.8 Hz. Both CMV and HFV were adjusted to result in similar arterial CO2 tensions. The distribution of Vr/Qr during HFV at 5.8 Hz tended to be more uniform than during HFV at 15.0 or 29.8 Hz or during CMV. Consistent with this observation, arterial O2 tension (PaO2) tended to be higher during HFV at 5.8 Hz (means +/- SD, 90 +/- 9 Torr) than during HFV at 15.0 Hz (83 +/- 9 Torr) or 29.8 Hz (78 +/- 10 Torr); PaO2 was significantly higher during HFV at 5.8 Hz than during CMV (83 +/- 7 Torr).

“Closing volume” during high-frequency ventilation in anesthetized dogs

1988 ◽  
Vol 32 (2) ◽  
pp. 140-146 ◽  
Author(s):  
T. Haghenberg ◽  
M. Wendt ◽  
J. Meyer ◽  
K. Wrenger ◽  
P. Lawin
Keyword(s):  
High Frequency ◽  
High Frequency Ventilation ◽  
Closing Volume ◽  
Frequency Ventilation ◽  
Anesthetized Dogs

Resonant amplification of delivered volume during high-frequency ventilation

1986 ◽  
Vol 60 (3) ◽  
pp. 885-892 ◽  
Author(s):  
V. Brusasco ◽  
K. C. Beck ◽  
M. Crawford ◽  
K. Rehder
Keyword(s):  
Stroke Volume ◽  
Endotracheal Tube ◽  
High Frequency ◽  
Gas Flow ◽  
High Frequency Ventilation ◽  
Frequency Ventilation ◽  
Anesthetized Dogs ◽  
Gas Volume

The volume of gas delivered from a high-frequency ventilation (HFV) circuit was measured with an ultrasonic flowmeter. The measurements were done in vitro (20-liter air-filled glass bottle) and in vivo (9 anesthetized dogs lying supine) at oscillation frequencies ranging from 4 to 23 Hz and stroke volumes of the pump ranging from 36 to 150 ml. We varied the length and diameter of the tube connecting the pump with the endotracheal tube, the length and diameter of the bias outflow tube, the diameter of the endotracheal tube, and the stroke volume of the pump. Both in vitro and in vivo, there was resonant amplification of the delivered gas volume; i.e., the delivered gas volume exceeded the stroke volume at certain frequencies. Altering the dimensions of connecting tube, endotracheal tube, bias outflow tube, or stroke volume, i.e., changing the resistance to gas flow, gas compliance, and/or gas inertance in these elements, altered the ratio of gas delivered to stroke volume that could be predicted by an electric analog. These data indicate that the delivered gas volume during HFV depends critically on the configuration of the HFV circuit, the size of the endotracheal tube, the oscillation frequency, and the pump stroke volume. Knowledge of the delivered gas volume during HFV and appreciation of the phenomenon of resonant amplification of the delivered gas volume will permit a more accurate description of factors contributing to gas transport during HFV.

Relationship for gas transport during high-frequency ventilation in dogs

1985 ◽  
Vol 59 (5) ◽  
pp. 1539-1547 ◽  
Author(s):  
J. G. Venegas ◽  
J. Custer ◽  
R. D. Kamm ◽  
C. A. Hales
Keyword(s):  
Body Weight ◽  
Functional Residual Capacity ◽  
Lung Volume ◽  
High Frequency ◽  
Alveolar Ventilation ◽  
High Frequency Ventilation ◽  
Arterial Pco2 ◽  
Expiration Time ◽  
Residual Capacity ◽  
Frequency Ventilation

Alveolar ventilation during high-frequency ventilation (HFV) was estimated from the washout of the positron-emitting isotope (nitrogen-13-labeled N2) from the lungs of anesthetized paralyzed supine dogs by use of a positron camera. HFV was delivered at a mean lung volume (VL) equal to the resting functional residual capacity with a ventilator that generated tidal volumes (VT) between 30 and 120 ml, independent of the animal's lung impedance, at frequencies (f) from 2 to 25 Hz, with constant inspiratory and expiratory flows and an inspiration-to-expiration time ratio of unity. Specific ventilation (SPV), which is equivalent to ventilation per unit of compartment volume, was found to follow closely the relation: SPV = 1.9(VT/VL)2.1 X f. From this relation and from arterial PCO2 measurements we found an expression for the normocapnic settings of VT and f, given VL and body weight (W). We found that the VL was an important normalizing parameter in the sense that VT/VL yielded a better correlation (r = 0.91) with SPV/f than VT/W (r = 0.62) or VT alone (r = 0.8).

Pneumothorax and pulmonary intersticial emphysema: treatment with selective bronchial occlusion and high frequency ventilation

1998 ◽  
Vol 74 (5) ◽  
pp. 411-5 ◽  
Author(s):  
Marcus A.J. Oliveira ◽  
Antônio C. P. Ferreira ◽  
João S. Oliveira ◽  
José S. Oliveira ◽  
Yara G. Silva
Keyword(s):  
High Frequency ◽  
High Frequency Ventilation ◽  
Frequency Ventilation
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