Venous air embolism.
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Echocardiography, Transesophageal↗
Biomedical subjects
P G Boysen
Publications and source records attributed to P G Boysen.
Graded exercise testing and postthoracotomy complications.
A controversy exists over whether or not preoperative exercise testing can predict postthoracotomy complications. This study was designed to evaluate the usefulness of a presurgical exercise protocol in patients with lung disease, but no evidence of cardiac disease. Seventy patients underwent baseline pulmonary function testing and split function perfusion studies, when indicated, to calculate predicted postoperative pulmonary function. Noninvasive data were incrementally collected from 17 patients by using a treadmill exercise tolerance test that was designed to elicit maximal performance. Inhaled and exhaled gas flow and volume, the partial pressure of O2 and CO2, maximal O2 consumption (VO2max), and maximal minute ventilation (VE max) were measured. The breathing and heart rate reserves were calculated by standard formulae in an attempt to separate cardiac from pulmonary exercise limitation. Two patients had postoperative cardiopulmonary complications after thoracotomy and lung resection, and six patients had noncardiopulmonary complications. There was no significant prognostic relationship among VO2max, VE max, maximum O2 pulse, and the incidence of postoperative cardiopulmonary complications. The percentages of predicted VE max and predicted maximum heart rate were related to the occurrence of total complications, but not specifically to cardiopulmonary complications. The results emphasize the difficulty in attempting to exercise thoracotomy candidates with chronic lung disease to maximal performance. Excluding patients from further surgical consideration because of exercise limitation is not feasible based on these data.
Aged↗
Pressure support and flow-cycled, assisted mechanical ventilation in acute lung injury.
Pressure support is a ventilatory mode, available with many microprocessor ventilators, which is patient-triggered, pressure-limited, and flow-cycled. This study compared the respiratory and hemodynamic effects of PS used as a stand-alone mode of ventilation with those of conventional patient-triggered, flow-cycled, assisted mechanical ventilation. Instruments for hemodynamic and respiratory measurements were placed in ten spontaneously breathing, anesthetized sheep. In each animal, baseline measurements were made during PS and flow-cycled AMV. Acute lung injury was then instituted by instilling hydrochloric acid in the endotracheal tube, and after 60 minutes, measurements were repeated. No hemodynamic or respiratory variables differed, either before or after ALI, between PS and AMV. This study demonstrates that PS, when used as a stand-alone mode of ventilation, has similar hemodynamic and respiratory effects as flow-cycled AMV.
Animals↗
Accurate determination of end-tidal carbon dioxide during administration of oxygen by nasal cannulae.
Measurement of end-tidal carbon dioxide tension (PETCO2) by mass spectrometry or infrared capnometry provides a clinically useful approximation of arterial carbon dioxide tension (PaCO2) in intubated patients. Although several devices have been proposed to sample PETCO2 during spontaneous breathing (i.e., unintubated patients receiving supplemental oxygen), thus far no reports have documented their efficacy. This article reports the use of an easily constructed modification of simple nasal cannulae that permits accurate sampling of PETCO2 during oxygen administration to unintubated patients. After amputation of the closed tip, a cap from a syringe was inserted via a slit made at the base into one prong of a pair of nasal cannulae. A capnometer was connected to the syringe cap, and PETCO2 and PaCO2 were determined simultaneously during the administration of 3 L/min oxygen via nasal cannulae to 21 normocapnic patients. The PaCO2 - PETCO2 gradients were calculated and compared with values obtained in the same patients after intubation and mechanical ventilation. No significant difference was found between the calculated gradients with nasal cannulae (2.09 +/- 2.18 mm Hg) versus intubation (2.87 +/- 2.82 mm Hg). Simultaneous oxygen administration and accurate sampling of PETCO2 may be achieved in unintubated patients by using this easily constructed modification of nasal cannulae.
Adult↗
High-frequency percussive ventilation compared with conventional mechanical ventilation.
In seven patients with severe respiratory distress, conventional mechanical ventilation and PEEP were used initially for respiratory support, which was changed to high-frequency percussive ventilation (HFPV) at the same level of airway pressure and FIO2. During both modes of ventilation, patients could breathe spontaneously via a low-threshold demand valve. With HFPV, PaO2 improved significantly (p less than .01) compared with PaO2 during conventional methods. Cardiac output was unaffected by the change to HFPV.
Carbon Dioxide↗
Effects of expiratory flow resistance on inspiratory work of breathing.
To minimize work of breathing, airway pressure should not fluctuate during spontaneous breathing with continuous positive airway pressure (CPAP). However, flow resistance in the inspiratory limb of the breathing circuit and an inadequate continuous gas flow rate result in airway pressure fluctuation and increased work of breathing. Flow resistance of the expiratory pressure/exhalation valve also directly affects the level of airway pressure during spontaneous inhalation with CPAP (the greater the resistance of the valve, the greater the decrease in airway pressure and work of breathing). We compared this effect with three types of expiratory pressure valves: a threshold resistor with low resistance to flow, an inflatable balloon (mushroom) valve with moderate resistance to flow, and a variable-orifice flow resistor with a high resistance to flow. Work increased up to threefold with the balloon valve and more than tenfold with the flow resistor compared with the threshold resistor. To apply CPAP, expiratory pressure valves with low resistance to flow should be used to minimize fluctuations in airway pressure and, thus, in the work of spontaneous breathing.
Humans↗
Noninvasive monitoring of lung function during mechanical ventilation.
Noninvasive monitoring can greatly enhance decision-making and clinical approaches to the respiratory failure patient. Newer microprocessor systems will calculate, present, and trend derived data such as airway resistance and lung-thorax compliance. These changes characterize the degree of lung dysfunction and parallel abnormalities in gas exchange.
Airway Resistance↗
Failure of high frequency jet ventilation to ventilate patients adequately during extracorporeal shock-wave lithotripsy.
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Adult↗
Flow resistance of expiratory positive-pressure valve systems.
The flow-resistive characteristics of a variety of commercially available expiratory positive-pressure valve systems used to provide continuous positive airway pressure (CPAP) and positive end-expiratory pressure were evaluated. One flow-resistor and seven threshold-resistor expiratory pressure valve systems were set at 5, 10, 15, 20, and 25 cm H2O of expiratory pressure, and sinusoidal exhaled flows peaking at 50,100, and 200 L/min were directed through each valve at each level of expiratory pressure. The Siemens flow-resistor valve demonstrated the greatest deviation in pressure above set CPAP levels at peak flow rates of 100 and 200 L/min, which suggests high resistance to exhaled flow. The Vital Signs threshold-resistor valve demonstrated the least deviation in pressure from set CPAP levels at all rates of exhaled flow, which suggests low flow resistance. The Emerson and IMV Bird threshold-resistor systems resisted flow less than the BEAR-2 and the Puritan-Bennett MA-2 and 7200 inflatable-balloon threshold-resistor-like valve systems. These data suggest that threshold resistors may be classified as low-resistance or high-resistance types. Using only low-resistance threshold resistors for CPAP may minimize the incidence of barotrauma and other deleterious effects related to airway pressure.
Airway Resistance↗
A manometer to measure demand valve reference pressure.
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Equipment Design↗
A mechanical model of spontaneous ventilation.
An Emerson 3-PV ventilator was modified to function as a model for spontaneous ventilation. Respiratory rates, tidal volumes, inspiratory/expiratory time ratios, and flow rates were adjusted to produce sinusoidal inspiratory and expiratory flow patterns that mimicked physiologic ventilation.
Models, Biological↗
Nocturnal oxygen therapy and hemodynamic changes in COPD.
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Hemodynamics↗
Demand valve improperly set resulting in pulmonary barotrauma.
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Adult↗
Prediction of theophylline dosage regimens from limited serum sampling.
Intravenous aminophylline was administered to 13 subjects (6 normal, 7 with chronic obstructive pulmonary disease), and multiple blood specimens were drawn over an 8-hour period for theophylline analysis. Half of the samples were obtained during the distribution phase of the drug and the remainder during the elimination phase. These data were entered into a computer program that both calculates and graphically displays individual two-compartment pharmacokinetic data, and recommends a dosing regimen. Analysis of these data demonstrates wide variability in the theophylline volume of distribution, half-life, and predicted dosage regimen. Dosage regimens can be individualized by obtaining two specimens for theophylline analysis during the elimination phase after intravenous administration of the drug; these regimens correlate extremely well (r2 = 0.95) with those designed using all the data points.
Drug Administration Schedule↗
Hemodynamic monitoring in the adult respiratory distress syndrome.
Because of the derangements in pulmonary function in the patient with adult respiratory distress syndrome and alterations in cardiac pulmonary function during therapy, hemodynamic monitoring can provide important diagnostic and therapeutic information. Early differentiation between cardiogenic and noncardiogenic pulmonary edema can be facilitated. The response to therapy can be monitored so that cardiopulmonary function can be optimized. Although some interrelationships in this response to therapy have not been fully elucidated, more intelligent therapeutic approaches can be individualized for each patient.
Adult↗
Alcohol increases sleep apnea and oxygen desaturation in asymptomatic men.
Using standard sleep techniques, we performed a placebo-controlled and randomized study to assess the effect of alcohol ingestion (2 ml/kg of body weight) on breathing and oxygen saturation during sleep. Twenty asymptomatic men volunteered for the two-night study: 11 were given a placebo on night 1, and alcohol on night 2 (group A); nine were given alcohol on night 1 and a placebo on night 2 (group B). We compared the incidence of sleep events (apnea, hypopnea and arterial oxygen disaturation) during the nights the subjects received alcohol and during the nights they received the placebo. Alcohol was associated with significant increases in the occurrence of the following: the number of sleep events (207 to 383,p less than 0.01), the events of arterial oxygen disaturation (118 to 226, p less than 0.01) and the number of apneic events (20 to 110, p less than 0.01). Alcohol had no significant effects on the number of times hypopnea occurred. Values obtained during sleep on the control night after alcohol ingestion also showed that the episodes of arterial oxygen desaturation remained statistically increased over control values before the ingestion of any alcohol (p = 0.01). These results show that in asymptomatic men alcohol ingestion increases the incidence of arterial oxygen desaturation and disordered breathing during sleep and that the increase in arterial oxygen desaturation persists for an additional night, even when no alcohol is consumed.
Adult↗
Menopause, medroxyprogesterone and breathing during sleep.
Twenty-one postmenopausal women were monitored for sleep-disordered breathing and nocturnal oxygen desaturation to evaluate the contribution of progestational hormones to the occurrence of these sleep events. For approximately one month 11 subjects received 30 mg of medroxyprogesterone (MPG) daily, and 10 received placebo tablets in a randomized, double-blind controlled study. Respiration, saturation and electroencephalography were monitored during one night of sleep before and one night after therapy. Contrasted with the low incidence of disordered breathing and desaturation in premenopausal women, 71 percent of the postmenopausal women had such events. In the placebo-treated group, all measured variables of sleep and breathing were identical on the two nights, which suggested that the findings of a single night of sleep monitoring may be representative of other nights of sleep. Although several subjects appeared to show improvement with MPG, only the maximum duration of apnea was significantly reduced the second night (p less than 0.03).
Adult↗
A radiographic method for measuring steady-state functional residual capacity in the supine patient. A method suitable for sleep studies.
We have devised a method to measure functional residual capacity (FRC) in the recumbent, spontaneously breathing patient. Simultaneous anteroposterior and lateral chest radiographs were exposed at the end of an exhalation, as determined by tracings of flow sensed by a nasal thermistor. The volume of the lungs was then planimetrically measured. Functional residual capacity was sequentially measured in 20 supine subjects, both by a helium dilution technique and by the radiographic technique. Planimetric measurement of FRC correlated well with the helium dilution technique, with a range of FRC measurements from 1.53 to 6.41 L (r = 0.94). This method of measuring lung volume should be useful in evaluating changes in FRC associated with different sleep stages and in explaining the mechanisms causing nocturnal oxygen desaturation in patients with chronic obstructive lung disease.
Functional Residual Capacity↗