Lung volume recruitment during high-frequency oscillation in atelectasis-prone rabbits

1988 ◽  
Vol 64 (4) ◽  
pp. 1607-1614 ◽  
Author(s):  
L. J. Byford ◽  
J. H. Finkler ◽  
A. B. Froese
Keyword(s):  
Lung Volume ◽  
High Frequency ◽  
Airway Pressure ◽  
Random Order ◽  
High Frequency Oscillation ◽  
Mean Airway Pressure ◽  
Mean Pressure ◽  
Residual Capacity ◽  
Lung Volume Recruitment ◽  
Arterial Po2

In diffuse lung injury, optimal oxygenation occurs with high-frequency oscillatory ventilation (HFO-A, where A is active expiratory phase) when sustained inflations (SI) are applied periodically to recruit lung volume. Theoretically pulsed pressures may be safer and more effective than static pressures for reexpanding alveoli. We compared the increases in lung volume and arterial PO2 (PaO2) induced by 30-s increases in mean airway pressure in six New Zealand White rabbits made atelectasis prone by saline lavage plus 1 h of conventional ventilation. Pulsatile SI's (HFO-A left on during increase in mean pressure) of delta PSI = 5, 10, and 15 cmH2O and static SI's (HFO-A off during SI) of delta PSI = 5, 10, 15, and 20 cmH2O were delivered in random order. Lungs were ventilated at 15 Hz, inspired fractional concentration of O2 = 1.0, and mean airway pressure 15-20 cmH2O between test periods and deflated to functional residual capacity before each SI to standardize volume history. With both maneuvers, increases in lung volume and PaO2 induced by SI's were proportional to the magnitude of the SI (P less than 0.001) in all cases. Pulsatile SI's consistently increased lung volume and PaO2 more than static SI's having the same delta PSI (P less than 0.005) such that any given target PaO2 or change in volume (delta V) was achieved at 5 cmH2O less mean pressure with the pulsatile maneuver. Respiratory system compliance increased after both types of SI. Oxygenation and lung volume changes at 5 min were related with r = 0.58 (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of the Ti/Te ratio on mean intratracheal pressure in high-frequency oscillatory ventilation

1998 ◽  
Vol 84 (5) ◽  
pp. 1520-1527 ◽  
Author(s):  
Ulrich Thome ◽  
Frank Pohlandt
Keyword(s):  
High Frequency ◽  
Airway Pressure ◽  
High Frequency Oscillatory Ventilation ◽  
Inspiratory Time ◽  
Mean Airway Pressure ◽  
Air Trapping ◽  
Oscillatory Ventilation ◽  
Mean Pressure ◽  
Oscillation Frequencies ◽  
High Frequency Oscillatory

In high-frequency oscillatory ventilation (HFOV), an adequate mean airway pressure is crucial for successful ventilation and optimal gas exchange, but air trapping cannot be detected by the usual measurement at the y piece. Intratracheal pressures produced by the high-frequency oscillators HFV-Infantstar (IS), Babylog 8000 (BL), and the SensorMedics 3100A (SM) [the latter with either 30% (SM30) or 50% (SM50) inspiratory time] were investigated in four anesthetized tracheotomized female piglets that were 1 day old and weighed 1.6–1.9 kg (mean 1.76 kg). The endotracheal tube was repeatedly clamped while the piglets were ventilated with an oscillation frequency of 10 Hz, and the airway pressure distal of the clamp was recorded as a measure of average intrapulmonary pressure during oscillation. Clamping resulted in a significant decrease of mean airway pressure when the piglets were ventilated with SM30(−0.86 cmH2O), BL (−0.66 cmH2O), and IS (−0.71 cmH2O), but airway pressure increased by a mean of 0.76 cmH2O with SM50. Intratracheal pressure, when measured by a catheter pressure transducer at various oscillation frequencies, was lower than at the y piece by 0.4–0.9 cmH2O (SM30), 0.3–3 cmH2O (BL), and 1–4.7 cmH2O (IS) but was 0.4–0.7 cmH2O higher with SM50. We conclude that the inspiratory-to-expiratory time (Ti/Te) ratio influences the intratracheal and intrapulmonary pressures in HFOV and may sustain a mean pressure gradient between the y piece and the trachea. A Ti/Te ratio < 1:1 may be useful to avoid air trapping when HFOV is used.

Setting Mean Airway Pressure during High-frequency Oscillatory Ventilation According to the Static Pressure–Volume Curve in Surfactant-deficient Lung Injury

2003 ◽  
Vol 99 (6) ◽  
pp. 1313-1322 ◽  
Author(s):  
Thomas Luecke ◽  
Juergen P. Meinhardt ◽  
Peter Herrmann ◽  
Gerald Weisser ◽  
Paolo Pelosi ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Lung Volume ◽  
High Frequency ◽  
Airway Pressure ◽  
Static Pressure ◽  
High Frequency Oscillatory Ventilation ◽  
Mean Airway Pressure ◽  
Oscillatory Ventilation ◽  
Hemodynamic Variables ◽  
High Frequency Oscillatory

Background Numerous studies suggest setting positive end-expiratory pressure during conventional ventilation according to the static pressure-volume (P-V) curve, whereas data on how to adjust mean airway pressure (P(aw)) during high-frequency oscillatory ventilation (HFOV) are still scarce. The aims of the current study were to (1) examine the respiratory and hemodynamic effects of setting P(aw) during HFOV according to the static P-V curve, (2) assess the effect of increasing and decreasing P(aw) on slice volumes and aeration patterns at the lung apex and base using computed tomography, and (3) study the suitability of the P-V curve to set P(aw) by comparing computed tomography findings during HFOV with those obtained during recording of the static P-V curve at comparable pressures. Methods Saline lung lavage was performed in seven adult pigs. P-V curves were obtained with computed tomography scanning at each volume step at the lung apex and base. The lower inflection point (Pflex) was determined, and HFOV was started with P(aw) set at Pflex. The pigs were provided five 1-h cycles of HFOV. P(aw), first set at Pflex, was increased to 1.5 times Pflex (termed 1.5 Pflex(inc)) and 2 Pflex and decreased thereafter to 1.5 times Pflex and Pflex (termed 1.5 Pflex(dec) and Pflex(dec)). Hourly measurements of respiratory and hemodynamic variables as well as computed tomography scans at the apex and base were made. Results High-frequency oscillatory ventilation at a P(aw) of 1.5 Pflex(inc) reestablished preinjury arterial oxygen tension values. Further increase in P(aw) did not change oxygenation, but it decreased oxygen delivery as a result of decreased cardiac output. No differences in respiratory or hemodynamic variables were observed when comparing HFOV at corresponding P(aw) during increasing and decreasing P(aw). Variation in total slice lung volume (TLVs) was far less than expected from the static P-V curve. Overdistended lung volume was constant and less than 3% of TLVs. TLVs values during HFOV at Pflex, 1.5 Pflex(inc), and 2 Pflex were significantly greater than TLVs values at corresponding tracheal pressures on the inflation limb of the static P-V curve and located near the deflation limb. In contrast, TLVs values during HFOV at decreasing P(aw) (i.e., 1.5 Pflex(dec) and Pflex(dec)) were not significantly greater than corresponding TLV on the deflation limb of the static P-V curves. The marked hysteresis observed during static P-V curve recordings was absent during HFOV. Conclusions High-frequency oscillatory ventilation using P(aw) set according to a static P-V curve results in effective lung recruitment, and slice lung volumes during HFOV are equal to those from the deflation limb of the static P-V curve at equivalent pressures.

Effects of mean airway pressure on gas transport during high-frequency ventilation in dogs

1986 ◽  
Vol 61 (5) ◽  
pp. 1896-1902 ◽  
Author(s):  
Y. Yamada ◽  
J. G. Venegas ◽  
D. J. Strieder ◽  
C. A. Hales
Keyword(s):  
Lung Volume ◽  
High Frequency ◽  
Airway Pressure ◽  
Gas Transport ◽  
Blood Gases ◽  
Co2 Production ◽  
High Frequency Ventilation ◽  
Mean Airway Pressure ◽  
Arterial Blood ◽  
Frequency Ventilation

In 10 anesthetized, paralyzed, supine dogs, arterial blood gases and CO2 production (VCO2) were measured after 10-min runs of high-frequency ventilation (HFV) at three levels of mean airway pressure (Paw) (0, 5, and 10 cmH2O). HFV was delivered at frequencies (f) of 3, 6, and 9 Hz with a ventilator that generated known tidal volumes (VT) independent of respiratory system impedance. At each f, VT was adjusted at Paw of 0 cmH2O to obtain a eucapnia. As Paw was increased to 5 and 10 cmH2O, arterial PCO2 (PaCO2) increased and arterial PO2 (PaO2) decreased monotonically and significantly. The effect of Paw on PaCO2 and PaO2 was the same at 3, 6, and 9 Hz. Alveolar ventilation (VA), calculated from VCO2 and PaCO2, significantly decreased by 22.7 +/- 2.6 and 40.1 +/- 2.6% after Paw was increased to 5 and 10 cmH2O, respectively. By taking into account the changes in anatomic dead space (VD) with lung volume, VA at different levels of Paw fits the gas transport relationship for HFV derived previously: VA = 0.13 (VT/VD)1.2 VTf (J. Appl. Physiol. 60: 1025–1030, 1986). We conclude that increasing Paw and lung volume significantly decreases gas transport during HFV and that this effect is due to the concomitant increase of the volume of conducting airways.

Differential effect of recruitment maneuvres on pulmonary blood flow and oxygenation during HFOV in preterm lambs

2008 ◽  
Vol 105 (2) ◽  
pp. 603-610 ◽  
Author(s):  
Graeme R. Polglase ◽  
Timothy J. M. Moss ◽  
Ilias Nitsos ◽  
Beth J. Allison ◽  
J. Jane Pillow ◽  
...  
Keyword(s):  
Blood Flow ◽  
Lung Volume ◽  
Airway Pressure ◽  
Pulmonary Blood Flow ◽  
Ductus Arteriosus ◽  
Oxygenation Index ◽  
Preterm Neonates ◽  
Mean Airway Pressure ◽  
Lung Volume Recruitment ◽  
High Frequency Oscillatory

The effects of lung volume recruitment manouvres on pulmonary blood flow (PBF) during high-frequency oscillatory ventilation (HFOV) in preterm neonates are unknown. Since increased airway pressure adversely affects PBF, we compared the effects of two HFOV recruitment strategies on PBF and oxygenation index (OI). Preterm lambs (128 ± 1 day gestation; term ∼150 days) were anesthetized and ventilated using HFOV (10 Hz, 33% tI) with a mean airway pressure (Pao) of 15 cmH2O. Lung volume was recruited by either increasing Pao to 25 cmH2O for 1 min, repeated five times at 5-min intervals (Sigh group; n = 5) or stepwise (5 cmH2O) changes in Pao at 5-min intervals incrementing up to 30 cmH2O then decrementing back to 15 cmH2O (Ramp group; n = 6). Controls ( n = 5) received constant HFOV at 15 cmH2O. PBF progressively decreased (by 45 ± 4%) and OI increased (by 15 ± 6%, indicating reduced oxygenation) in controls during HFOV, which was similar to the changes observed in the Sigh group of lambs. In the Ramp group, PBF fell (by 54 ± 10%) as airway pressure increased ( r2 = 0.99), although the PBF did not increase again as the Pao was subsequently reduced. The OI decreased (by 47 ± 9%), reflecting improved oxygenation at high Pao levels during HFOV in the Ramp group. However, high Pao restored retrograde PBF during diastole in four of six lambs, indicating the restoration of right-to-left shunting through the ductus arteriosus. Thus the choice of volume recruitment maneuvre influences the magnitude of change in OI and PBF that occurs during HFOV. Despite significantly improving OI, the ramp recruitment approach causes sustained changes in PBF.

Effect of mean airway pressure on gas exchange during high-frequency oscillatory ventilation

1991 ◽  
Vol 70 (2) ◽  
pp. 701-707 ◽  
Author(s):  
B. R. Boynton ◽  
D. Villanueva ◽  
M. D. Hammond ◽  
P. N. Vreeland ◽  
B. Buckley ◽  
...  
Keyword(s):  
Lung Volume ◽  
High Frequency ◽  
Airway Pressure ◽  
Total Lung Capacity ◽  
High Frequency Oscillatory Ventilation ◽  
Venous Admixture ◽  
Mean Airway Pressure ◽  
Lung Capacity ◽  
Before And After ◽  
High Frequency Oscillatory

We studied the effect of mean airway pressure (Paw) on gas exchange during high-frequency oscillatory ventilation in 14 adult rabbits before and after pulmonary saline lavage. Sinusoidal volume changes were delivered through a tracheostomy at 16 Hz, a tidal volume of 1 or 2 ml/kg, and inspired O2 fraction of 0.5. Arterial PO2 and PCO2 (PaO2, PaCO2), lung volume change, and venous admixture were measured at Paw from 5 to 25 cmH2O after either deflation from total lung capacity or inflation from relaxation volume (Vr). The rabbits were lavaged with saline until PaO2 was less than 70 Torr, and all measurements were repeated. Lung volume change was measured in a pressure plethysmograph. Raising Paw from 5 to 25 cmH2O increased lung volume by 48-50 ml above Vr in both healthy and lavaged rabbits. Before lavage, PaO2 was relatively insensitive to changes in Paw, but after lavage PaO2 increased with Paw from 42.8 +/- 7.8 to 137.3 +/- 18.3 (SE) Torr (P less than 0.001). PaCO2 was insensitive to Paw change before and after lavage. At each Paw after lavage, lung volume was larger, venous admixture smaller, and PaO2 higher after deflation from total lung capacity than after inflation from Vr. This study shows that the effect of increased Paw on PaO2 is mediated through an increase in lung volume. In saline-lavaged lungs, equal distending pressures do not necessarily imply equal lung volumes and thus do not imply equal PaO2.

Effects of mean airway pressure and tidal volume on lung and chest wall mechanics in the dog

1993 ◽  
Vol 74 (5) ◽  
pp. 2286-2293 ◽  
Author(s):  
G. M. Barnas ◽  
J. Sprung
Keyword(s):  
Mechanical Properties ◽  
Tidal Volume ◽  
Chest Wall ◽  
Respiratory System ◽  
Lung Volume ◽  
Airway Pressure ◽  
Dynamic Mechanical Properties ◽  
Mean Airway Pressure ◽  
Residual Capacity ◽  
Normal Mean

Dependencies of the dynamic mechanical properties of the respiratory system on mean airway pressure (Paw) and the effects of tidal volume (VT) are not completely clear. We measured resistance and dynamic elastance of the total respiratory system (Rrs and Ers), lungs (RL and EL), and chest wall (Rcw and Ecw) in six healthy anesthetized paralyzed dogs during sinusoidal volume oscillations at the trachea (50–300 ml; 0.4 Hz) delivered at mean Paw from -9 to +23 cmH2O. Changes in end-expiratory lung volume, estimated with inductance plethysmographic belts, showed a typical sigmoidal relationship to mean Paw. Each dog showed the same dependencies of mechanical properties on mean Paw and VT. All elastances and resistances were minimal between 5 and 10 cmH2O mean Paw. All elastances, Rrs, and RL increased greatly with decreasing Paw below 5 cmH2O. Ers and EL increased above 10 cmH2O. Ecw, Ers, Rcw, and Rrs decreased slightly with increasing VT, but RL and EL were independent of VT. We conclude that 1) respiratory system impedance is minimal at the normal mean lung volume of supine anesthetized paralyzed dogs; 2) the dependency of RL on lung volume above functional residual capacity is dependent on VT and respiratory frequency; and 3) chest wall, but not lung, mechanical behavior is nonlinear (i.e., VT dependent) at any given lung volume.

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