Effects of high-frequency jet ventilation on arterial baroreflex regulation of heart rate

1987 ◽  
Vol 63 (6) ◽  
pp. 2216-2222 ◽  
Author(s):  
J. J. Rouby ◽  
M. Houissa ◽  
J. F. Brichant ◽  
J. F. Baron ◽  
C. McMillan ◽  
...  
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
High Frequency ◽  
Airway Pressure ◽  
Systolic Arterial Pressure ◽  
Right Atrial ◽  
Arterial Baroreflex ◽  
Mean Airway Pressure ◽  
Jet Ventilation ◽  
Pulmonary Volume

Fifteen anesthetized mechanically ventilated patients recovering from multiple trauma were studied to compare the effects of high-frequency jet ventilation (HFJV) and continuous positive-pressure ventilation (CPPV) on arterial baroreflex regulation of heart rate. Systolic arterial pressure and right atrial pressure were measured using indwelling catheters. Electrocardiogram (ECG) and mean airway pressure were continuously monitored. Lung volumes were measured using two linear differential transformers mounted on thoracic and abdominal belts. Baroreflex testing was performed by sequential intravenous bolus injections of phenylephrine (200 micrograms) and nitroglycerin (200 micrograms) to raise or lower systolic arterial pressure by 20–30 Torr. Baroreflex regulation of heart rate was expressed as the slope of the regression line between R-R interval of the ECG and systolic arterial pressure. In each mode of ventilation the ventilatory settings were chosen to control mean airway pressure and arterial PCO2 (PaCO2). In HFJV a tidal volume of 159 +/- 61 ml was administered at a frequency of 320 +/- 104 breaths/min, whereas in CPPV a tidal volume of 702 +/- 201 ml was administered at a frequency of 13 +/- 2 breaths/min. Control values of systolic arterial pressure, R-R interval, mean pulmonary volume above apneic functional residual capacity, end-expiratory pulmonary volume, right atrial pressure, mean airway pressure, PaCO2, pH, PaO2, and temperature before injection of phenylephrine or nitroglycerin were comparable in HFJV and CPPV. Baroreflex regulation of heart rate after nitroglycerin injection was significantly higher in HFJV (4.1 +/- 2.8 ms/Torr) than in CPPV (1.96 +/- 1.23 ms/Torr).(ABSTRACT TRUNCATED AT 250 WORDS)

Mean airway pressure and mean alveolar pressure during high-frequency jet ventilation in rabbits

1986 ◽  
Vol 61 (2) ◽  
pp. 456-463 ◽  
Author(s):  
J. J. Perez Fontan ◽  
G. P. Heldt ◽  
G. A. Gregory
Keyword(s):  
High Frequency ◽  
Airway Pressure ◽  
Flow Distribution ◽  
Alveolar Pressure ◽  
Mean Airway Pressure ◽  
Jet Ventilation ◽  
Pressure Losses ◽  
High Frequency Jet Ventilation ◽  
Airway Pressures ◽  
The Mean

Mean airway pressure underestimates mean alveolar pressure during high-frequency oscillatory ventilation. We hypothesized that high inspiratory flows characteristic of high-frequency jet ventilation may generate greater inspiratory than expiratory pressure losses in the airways, thereby causing mean airway pressure to overestimate, rather than underestimate, mean alveolar pressure. To test this hypothesis, we ventilated anesthetized paralyzed rabbits with a jet ventilator at frequencies of 5, 10, and 15 Hz, constant inspiratory-to-expiratory time ratio of 0.5 and mean airway pressures of 5 and 10 cmH2O. We measured mean total airway pressure in the trachea with a modified Pitot probe, and we estimated mean alveolar pressure as the mean pressure corresponding in the static pressure-volume relationship to the mean volume of the respiratory system measured with a jacket plethysmograph. We found that mean airway pressure was similar to mean alveolar pressure at frequencies of 5 and 10 Hz but overestimated it by 1.1 and 1.4 cmH2O at mean airway pressures of 5 and 10 cmH2O, respectively, when frequency was increased to 15 Hz. We attribute this finding primarily to the combined effect of nonlinear pressure frictional losses in the airways and higher inspiratory than expiratory flows. Despite the nonlinearity of the pressure-flow relationship, inspiratory and expiratory net pressure losses decreased with respect to mean inspiratory and expiratory flows at the higher rates, suggesting rate dependence of flow distribution. Redistribution of tidal volume to a shunt airway compliance is thought to occur at high frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac norepinephrine stores and chronotropic reflex response after thoracotomy

1975 ◽  
Vol 39 (2) ◽  
pp. 287-291 ◽  
Author(s):  
H. R. Schelbert ◽  
R. S. Pavelec ◽  
S. Sandoval ◽  
J. W. Covell
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Heart Rate Response ◽  
Systolic Arterial Pressure ◽  
Right Atrial ◽  
Reflex Response ◽  
Initial Operation ◽  
Chronotropic Response ◽  
Right Thoracotomy ◽  
Significant Depression

Although alterations in cardiac reflex activity, as well as in cardiac norepinephrine stores, have been shown following thoracic operations, the physiological relationship between these alterations has not been investigated. Cardiac norepinephrine stores were examined in 17 normal dogs, and in 16 dogs 1–6 wk after a right thoracotomy. The heart rate response to induced arterial hypotension (mean decrease 17–20 mmHg) prior to and following surgery was also examined in 10 dogs. A significant depression in right atrial norepinephrine stores from normal levels of 1.95 +/- 0.13 mug/g to 1.30 +/- 0.25 mug/g (33%) (P less than 0.05) was observed during the first wk following surgery. During the same period the heart rate response to a fall of 17–20 mmHg systolic arterial pressure was clearly reduced from 52.8 +/- 6.9 beats/min to 17.0 +/- 4.8 beats/min (67.8%; P less than 0.05). Right atrial norepinephrine stores at the time of the initial operation and when reflex responses were most markedly depressed demonstrated that the decrease in norepinephrine stores was paralleled by attenuation of the chronotropic response to hypotension.

Regional blood volume distribution during positive and negative airway pressure breathing in supine humans

1993 ◽  
Vol 75 (4) ◽  
pp. 1740-1747 ◽  
Author(s):  
J. Peters ◽  
B. Hecker ◽  
D. Neuser ◽  
W. Schaden
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Arterial Pressure ◽  
Vascular Resistance ◽  
Airway Pressure ◽  
Left Ventricular ◽  
Whole Body ◽  
Blood Content ◽  
Calf Blood Flow ◽  
Negative Airway Pressure

To assess the effects of continuous positive (CPAP) or negative airway pressure (CNAP) breathing (+/- 10#x2013;12 cmH2O, duration 25 min) on blood content in the body's capacitance vasculature, regional distribution of labeled red blood cells was evaluated in seven spontaneously breathing supine volunteers. Counts were acquired by whole body scans and detectors overlying the liver, intestine, left ventricle, and lower arm, and arterial pressure, heart rate, calf blood flow and vascular resistance, hematocrit, vasopressin, and atrial natriuretic peptide plasma concentrations were also obtained. With CPAP, thoracic, cardiac, and left ventricular counts diminished significantly by 7#x2013;10%, were accompanied by significant increases in counts over both the gut and liver, and remained decreased during CPAP but reversed to baseline with zero airway pressure. Calf blood flow and vascular resistance significantly decreased and increased, respectively, whereas limb counts, arterial pressure, heart rate, and hormone concentrations remained unchanged. With CNAP, in contrast, regional counts and other variables did not change. Thus, moderate levels of CPAP deplete the intrathoracic vascular bed and heart, shifting blood toward the gut and liver but not toward the limbs. No short-term compensation increasing cardiac filling during CPAP was seen. In contrast, CNAP did not alter intrathoracic or organ blood content and, therefore, does not simply mirror the effects evoked by CPAP.

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.

scholarly journals MEAN AIRWAY PRESSURE (MAP) DURING HIGH FREQUENCY FLOW INTERRUPTION (HFFI).1979

1996 ◽  
Vol 39 ◽  
pp. 332-332
Author(s):  
Wil Geven ◽  
Dianne Visser ◽  
Jeroen Hopman ◽  
Desiree Cremers ◽  
Margot van de Bor
Keyword(s):  
High Frequency ◽  
Airway Pressure ◽  
Mean Airway Pressure ◽  
Flow Interruption
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