Efficacy of high-frequency ventilation in presence of extensive ventilation-perfusion mismatch

1985 ◽  
Vol 58 (3) ◽  
pp. 996-1004 ◽  
Author(s):  
K. G. Kaiser ◽  
N. J. Davies ◽  
R. Rodriguez-Roisin ◽  
H. Z. Bencowitz ◽  
P. D. Wagner
Keyword(s):  
High Frequency ◽  
Canine Model ◽  
Conventional Mechanical Ventilation ◽  
Inert Gas ◽  
High Frequency Ventilation ◽  
Gas Transfer ◽  
Arterial Pco2 ◽  
Pulmonary Hemodynamic ◽  
Frequency Ventilation ◽  
Normal Mean

Ten anesthetized normal dogs were each given two methacholine inhalational challenges to produce large amounts of low ventilation-perfusion (VA/Q) regions but little shunt. After one challenge, high-frequency ventilation (HFV) was applied, whereas after the other conventional mechanical ventilation (MV) was used, the order being randomized. Levels of both ventilatory modes were selected prior to challenge so as to result in similar and normal mean airway pressures and arterial PCO2 levels during control conditions. Gas exchange was assessed by both respiratory and multiple inert-gas transfer. Comparing the effect of HFV and MV, no statistically significant differences were found for lung resistance, pulmonary hemodynamic indices, arterial and mixed venous PO2, expired-arterial PO2 differences, or inert-gas data expressed as retention-excretion differences. The only variables that were different were mean airway pressure (2 cm higher during HFV, P less than 0.04) and arterial PCO2 (10 Torr higher during HFV, P less than 0.002). These results suggest that in this canine model of lung disease characterized by large amounts of low VA/Q regions, HFV is no more effective in delivering fresh gas to such regions than is MV.

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.

Pulmonary Mechanics in Preterm Neonates With Respiratory Failure Treated With High-Frequency Oscillatory Ventilation Compared With Conventional Mechanical Ventilation

PEDIATRICS ◽  
1991 ◽  
Vol 87 (4) ◽  
pp. 487-493
Author(s):  
Soraya Abbasi ◽  
Vinod K. Bhutani ◽  
Alan R. Spitzer ◽  
William W. Fox
Keyword(s):  
Mechanical Ventilation ◽  
Bronchopulmonary Dysplasia ◽  
High Frequency ◽  
Conventional Mechanical Ventilation ◽  
High Frequency Oscillatory Ventilation ◽  
Preterm Neonates ◽  
High Frequency Ventilation ◽  
Pulmonary Mechanics ◽  
Frequency Ventilation ◽  
High Frequency Oscillatory

Pulmonary mechanics were measured in 43 preterm neonates (mean ± SD values of birth weight 1.2 ± 0.3 kg, gestational age 30 ± 2 weeks) with respiratory failure who were concurrently randomly assigned to receive conventional mechanical ventilation (n = 22) or high-frequency ventilation (n = 21). The incidence of bronchopulmonary dysplasia was comparable in the two groups (high-frequency ventilation 57%, conventional ventilation 50%). Pulmonary functions were determined at 0.5, 1.0, 2.0, and 4.0 weeks postnatal ages. Data were collected while subjects were in a nonsedated state during spontaneous breathing. These sequential data show similar patterns of change in pulmonary mechanics during high-frequency ventilation and conventional mechanical ventilation irrespective of gestational age, birth weight stratification, or bronchopulmonary dysplasia. There was no significant difference in the pulmonary functions with either mode of ventilation during the acute phase (≤4 weeks) of respiratory disease. When evaluated by the clinical diagnosis of bronchopulmonary dysplasia, the pulmonary data suggested a less severe dysfunction in the high-frequency oscillatory ventilation-treated bronchopulmonary dysplasia group compared with the conventional mechanical ventilation-treated group. These results indicate that high-frequency oscillatory ventilation in preterm neonates does not reduce the risk of acute lung injury; however, the magnitude of the pulmonary dysfunction in the first 2 weeks of life merits a reevaluation.

Respiratory and inert gas exchange during high-frequency ventilation

1982 ◽  
Vol 52 (3) ◽  
pp. 683-689 ◽  
Author(s):  
H. T. Robertson ◽  
R. L. Coffey ◽  
T. A. Standaert ◽  
W. E. Truog
Keyword(s):  
Gas Exchange ◽  
High Frequency ◽  
Gas Flow ◽  
Inert Gases ◽  
Inert Gas ◽  
High Frequency Ventilation ◽  
Physiological Dead Space ◽  
Volume Ventilation ◽  
Frequency Ventilation ◽  
Carrier Gases

Pulmonary gas exchange during high-frequency low-tidal volume ventilation (HFV) (10 Hz, 4.8 ml/kg) was compared with conventional ventilation (CV) and an identical inspired fresh gas flow in pentobarbital-anesthetized dogs. Comparing respiratory and infused inert gas exchange (Wagner et al., J. Appl. Physiol. 36: 585--599, 1974) during HFV and CV, the efficiency of oxygenation was not different, but the Bohr physiological dead space ratio was greater on HFV (61.5 +/- 2.2% vs. 50.6 +/- 1.4%). However, the elimination of the most soluble inert gas (acetone) was markedly enhanced by HFV. The increased elimination of the soluble infused inert gases during HFV compared with CV may be related to the extensive intraregional gas mixing that allows the conducting airways to serve as a capacitance for the soluble inert gases. Comparing as exchange during HFV with three different density carrier gases (He, N2, and Ar), the efficiency of elimination of Co2 or the intravenously infused inert gases was greatest with He-O2. However, the alveolar-arterial partial pressure difference for O2 on He-O2 exceeded that on N2-O2 by 5.4 Torr during HFV. The finding agrees with similar observations during CV, suggesting that this aspect of gas exchange is not substantially altered by HFV.

Chemical and mechanical determinants of apnea during high-frequency ventilation

1988 ◽  
Vol 65 (1) ◽  
pp. 179-186 ◽  
Author(s):  
S. L. Thompson-Gorman ◽  
R. S. Fitzgerald ◽  
W. Mitzner
Keyword(s):  
High Frequency ◽  
Important Determinant ◽  
Multiple Logistic Regression Analysis ◽  
High Frequency Ventilation ◽  
Multiple Logistic Regression ◽  
Mean Airway Pressure ◽  
Arterial Pco2 ◽  
Frequency Ventilation ◽  
Respiratory Centers ◽  
Respiratory Variables

The factors responsible for the apnea observed during high-frequency ventilation (HFV) were evaluated in 14 pentobarbital sodium-anesthetized cats. A multiple logistic regression analysis provided an estimate of the probability of apnea during HFV as a function of four respiratory variables: mean airway pressure (Paw), tidal volume (VT), frequency, and arterial PCO2 (PaCO2). When mean Paw was 2 cmH2O, PaCO2, VT, and their interaction contributed significantly to the probability of apnea during HFV. At a low value of PaCO2 (25 Torr), the probability of apnea had a minimum value of 0.19 and gradually increased toward 1.0 as VT increased from 0.5 to 7 ml/kg. At higher levels of PaCO2 (30 and 35 Torr) the probability of apnea was zero in the low range of VT but sharply approached 1.0 above a VT of approximately 2.0 ml/kg. However, when Paw was increased to 6 cmH2O, only PaCO2 was an important determinant of apnea. In this case, the probability of apnea was 0.51 when PaCO2 was 25 Torr but decreased to 0.22 when PaCO2 was raised to 25 Torr. At neither Paw was the probability of apnea dependent on frequency. These results suggest that chemoreceptor inputs, in addition to both static and dynamic lung mechanoreceptor afferents, are responsible for determining the output of the central respiratory centers during HFV.

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).

High-Frequency Ventilation and Tracheal Injuries

PEDIATRICS ◽  
1986 ◽  
Vol 77 (4) ◽  
pp. 608-613
Author(s):  
Mark C. Mammel ◽  
Janice P. Ophoven ◽  
Patrick K. Lewallen ◽  
Margaret J. Gordon ◽  
Marylyn C. Sutton ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
High Frequency ◽  
Conventional Mechanical Ventilation ◽  
High Frequency Ventilation ◽  
Jet Ventilation ◽  
Standard Frequency ◽  
High Frequency Jet Ventilation ◽  
Frequency Ventilation ◽  
Tissue Changes ◽  
Adult Cats

Recent reports linking serious tracheal injuries to various forms of high-frequency ventilation prompted this study. We compared the tracheal histopathology seen following standard-frequency, conventional mechanical ventilation with that seen following high-frequency, conventional mechanical ventilation, and two different forms of high-frequency jet ventilation. Twenty-six adult cats were examined. Each was mechanically ventilated for 16 hours. Seven received standard-frequency, conventional mechanical ventilation at 20 breaths per minute. Seven received high-frequency, conventional mechanical ventilation at 150 breaths per minute. Six received high-frequency jet ventilation at 250 breaths per minute via the Instrument Development Corporation VS600 jet ventilator (IDC). Six received high-frequency jet ventilation at 400 breaths per minute via the Bunnell Life Pulse jet ventilator (BLP). A semiquantitative histopathologic scoring system graded tracheal tissue changes. All forms of high-frequency ventilation produced significant inflammation (erosion, necrosis, and polymorphonuclear leukocyte infiltration) in the trachea in the region of the endotracheal tube tip. Conventional mechanical ventilation produced less histopathology than any form of high-frequency ventilation. Of all of the ventilators examined, the BLP, the ventilator operating at the fastest rate, produced the greatest loss of surface cilia and depletion of intracellular mucus. IDC high-frequency jet ventilation and high-frequency, conventional mechanical ventilation produced nearly identical histologic injuries. In this study, significant tracheal damage occurred with all forms of high-frequency ventilation. The tracheal damage seen with high-frequency, conventional mechanical ventilation suggests that ventilator frequency, not delivery system, may be responsible for the injuries.

Neuromuscular blockade enhances phrenic nerve activity during high-frequency ventilation

1984 ◽  
Vol 56 (1) ◽  
pp. 31-34 ◽  
Author(s):  
S. J. England ◽  
A. Onayemi ◽  
A. C. Bryan
Keyword(s):  
Neuromuscular Blockade ◽  
Phrenic Nerve ◽  
High Frequency ◽  
Intact Animal ◽  
Rhythmic Activity ◽  
High Frequency Ventilation ◽  
Nerve Activity ◽  
Arterial Pco2 ◽  
Phrenic Nerve Activity ◽  
Frequency Ventilation

Phrenic nerve activity was monitored in anesthetized cats during high-frequency ventilation (HFV). Rhythmic phrenic discharge disappeared during HFV in all animals at normal arterial PCO2 levels. Rhythmic activity returned after neuromuscular blockade in the vagally intact animal. Although vagotomy alone also restored phrenic discharge, this activity was further enhanced by subsequent neuromuscular blockade. Therefore we suggest that apnea during HFV results from inspiratory inhibition mediated by both chest wall and vagal afferent mechanisms.

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