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Biomedical subjects

J M Luce

Publications and source records attributed to J M Luce.

At least 109 records · Page 6Linked to original sources
PubMed1984

Site of deposition and factors affecting clearance of aerosolized solute from canine lungs.

We determined the influence of several factors on lung solute clearance using aerosolized 99mTc-diethylenetriaminepentaacetate. We used a jet nebulizer-plate separator-balloon system to generate particles with an activity median aerodynamic diameter of 1.1 micron, administered the aerosol in a standard fashion, and determined clearance half times (t1/2) with a gamma-scintillation camera. The following serial studies were performed in five anesthetized, paralyzed, intubated, mechanically ventilated dogs: 1) control, with ventilatory frequency (f) = 15 breaths/min and tidal volume (VT) = 15 ml/kg during solute clearance; 2) repeat control, for reproducibility; 3) increased frequency, with f = 25 breaths/min and VT = 10 ml/kg; 4) positive end-expiratory pressure (PEEP) of 10 cmH2O; 5) unilateral pulmonary arterial occlusion (PAO); and 6) bronchial arterial occlusion (BAO). Control t1/2 was 25 +/- 5 min and did not change in the repeat control, increased frequency, or BAO experiments. PEEP markedly decreased t1/2 to 13 +/- 3 min (P less than 0.01), and PAO increased it to 37 +/- 6 min (P less than 0.05). We conclude that clearance from the lungs by our method is uninfluenced by increased frequency, increases markedly with PEEP, and depends on pulmonary, not bronchial, blood flow.

Aerosols↗
PubMed1984

Correlation between serial pulmonary function tests and fiberoptic bronchoscopy in patients with Pneumocystis carinii pneumonia and the acquired immune deficiency syndrome.

The records of 9 adult male patients with the acquired immune deficiency syndrome (AIDS) and biopsy-proved Pneumocystis carinii pneumonia were reviewed to determine the correlation between serial pulmonary function tests and the presence or absence of Pneumocystis organisms in subsequent bronchoscopy specimens. At diagnosis, total lung capacity (TLC) or vital capacity (VC) was abnormally low in 4 patients (44%) and diffusing capacity (DLCO) was abnormally low in 8 patients (89%). The ratio of forced expiratory volume in one second (FEV1) to forced vital capacity (FVC) was elevated in all patients. After 21 to 47 days of specific therapy for Pneumocystis pneumonia, changes in DLCO, TLC, VC, and FEV1/FVC did not correlate with the presence or absence of Pneumocystis organisms in bronchoscopy specimens from 7 patients. However, changes in DLCO 105 to 258 days after diagnosis seemed to correlate with the late response to treatment in 6 patients. These results suggest that decisions to terminate specific therapy for Pneumocystis pneumonia in patients with AIDS should not be based on short-term changes in pulmonary function.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Correlation between gallium lung scans and fiberoptic bronchoscopy in patients with suspected Pneumocystis carinii pneumonia and the acquired immune deficiency syndrome.

We retrospectively examined the sensitivity and specificity of gallium lung scans for detecting Pneumocystis carinii pneumonia in 22 patients with known or suspected acquired immune deficiency syndrome. Correlations were made between bronchoscopic results and gallium scan findings interpreted using a simple system (normal or abnormal) and a graded score (1 to 4). All 12 patients with Pneumocystis had abnormal scans by both interpretations (sensitivity, 100%). Five of these 12 patients had normal arterial PO2 values, chest roentgenograms, or both. In the 10 patients without Pneumocystis, scans were read as abnormal in 8 using the simple system (specificity, 20%) but were abnormal in only 1 using the grading system (specificity, 90%). Five patients with Pneumocystis pneumonia had scans and bronchoscopy after treatment; neither method of interpretation correlated with the presence of organisms. We conclude: (1) gallium scanning is a sensitive initial diagnostic test in patients with suspected Pneumocystis pneumonia; (2) a graded scoring system improves specificity; (3) an abnormal gallium scan (3 or greater) in patients with suspected Pneumocystis pneumonia is an indication for biopsy, even when the PO2 and/or chest roentgenogram are normal.

Acquired Immunodeficiency Syndrome↗
PubMed1983

The effects of prophylactic expiratory positive airway pressure on the resolution of oleic acid-induced lung injury in dogs.

It is not known whether positive end-expiratory airway pressure (PEEP) merely improves gas exchange in patients with the adult respiratory distress syndrome (ARDS) or if it also affects the resolution of their lung injury. The present investigation was performed to determine whether expiratory positive airway pressure (EPAP), a form of PEEP, is prophylactic in preventing the lung injury induced by oleic acid in dogs or in enhancing its resolution. Arterial and mixed venous blood gases and functional residual capacity (FRC) were measured in 14 pairs of mongrel dogs with indwelling catheters and permanent tracheostomies. One member of each pair was treated with 10 cm H2O EPAP through a valve attached to the tracheostomy tube. Both dogs received 0.06 ml/kg oleic acid intravenously at hour 0. Measurements were made at three, 12, and 24 hours, when EPAP was discontinued, and over the next six days. Five dog pairs were sacrificed at 72 hours; the other surviving animals were sacrificed at 168 hours. FRC was higher at three, 12, and 24 hours in dogs receiving EPAP than in the untreated dogs. The arterial oxygen tension (PaO2) was higher and the venous admixture (Qva/Qt) was lower at three and 12 hours in the dogs receiving EPAP than in the untreated dogs. However, after 24 hours, no differences were noted between the two groups in FRC, PaO2, Qav/Qt, mortality, final lung compliance to initial lung compliance differences, lung water to dry lung weight ratios, or histology. It is concluded that EPAP improves gas exchange during its administration, but has no demonstrable prophylactic effect on the resolution of lung injury in the oleic acid model of human ARDS.

Animals↗
PubMed1983

Regional blood flow during cardiopulmonary resuscitation in dogs using simultaneous and nonsimultaneous compression and ventilation.

We studied regional blood flow (QR) using radiolabeled microspheres and measured hemodynamic variables in 20 anesthetized dogs in normal sinus rhythm and during ventricular fibrillation treated with cardiopulmonary resuscitation (CPR). Nonsimultaneous compression and ventilation CPR (NSCV-CPR) was performed in seven dogs with a pneumatic piston that gave 50 chest compressions/min with an open airway with 10 ventilations at an airway pressure of 33 mm Hg interposed between each fifth and sixth compression. Simultaneous compression and ventilation (SCV-CPR) was performed in seven dogs with the piston and in six other dogs with a circumferential pneumatic vest. Both devices gave 30 compressions/min simultaneously with 30 ventilations that elevated airway pressure to 80 mm Hg., The abdomen was bound during SCV-CPR. Regional blood flow (mean +/- SD) to the cerebral hemispheres, cardiac ventricles, and kidneys, expressed as ml/min/100 g tissue, was 3.1 +/- 4.0, 3.4 +/- 3.3 and 1.5 +/- 1.5, respectively, during NSCV-CPR; 11.5 +/- 5.9, 4.9 +/- 4.7 and 2.7 +/- 2.7 during SCV-CPR (vest); and 16.2 +/- 7.2, 11.0 +/- 4.0 and 20.1 +/- 20.2 during SCV-CPR (piston) (all p less than 0.05 compared with NSCV-CPR). These results indicate that QR to all organs studied is reduced below normal sinus rhythm levels during CPR for ventricular fibrillation, QR to the brain is proportionately greater than QR to the heart and kidneys, and QR to the brain is greater with both forms of SCV-CPR than with NSCV-CPR.

Animals↗
PubMed1983

Diagnostic utility of fiberoptic bronchoscopy in patients with Pneumocystis carinii pneumonia and the acquired immune deficiency syndrome.

The records of 35 adult male patients with suspected Pneumocystis carinii pneumonia and the acquired immune deficiency syndrome were reviewed to determine the diagnostic utility of fiberoptic bronchoscopy. Twenty-two of the 24 patients (92%) shown to have Pneumocystis pneumonia were diagnosed by bronchoscopy; 20 patients were diagnosed after 1 bronchoscopy and 2 patients after 2 bronchoscopies. The sensitivity of bronchoscopy specimens for diagnosing Pneumocystis pneumonia was 79% for transbronchial biopsies (19 of 24), 78% for transbronchial biopsy touch preparations (7 of 9), 55% for bronchial washings (11 of 20), and 39% for bronchial brushings (7 of 18). The overall sensitivity of fiberoptic bronchoscopy was 85% (22 positive of 26 total bronchoscopies). Complications, occurring during 6 of the 37 bronchoscopies, were slight hemoptysis (1 patient), fever (2 patients), septic shock (1 patient), and pneumothorax (2 patients). Fiberoptic bronchoscopy is a safe and effective procedure for making the early diagnosis of Pneumocystis carinii pneumonia in adult male patients with the acquired immune deficiency syndrome.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Long-term oxygen therapy: physiologic and economic considerations.

Long-term oxygen therapy appears to be a safe means of treating hypoxemia. It can provide many physiologic improvements and prolongs life in persons with severe chronic arterial hypoxemia at rest. Recent studies suggest that arterial hypoxia is common during exercise and sleep, and it is likely that some patients with intermittent desaturation would benefit physiologically from supplemental oxygen. Oxygen is an expensive drug, and we do not know whether its benefits are greater than its costs in patients who are not hypoxic at rest. I believe that low-flow oxygen administered as continuously as possible should be strongly considered for all patients whose PaO2 is 55 mm Hg or less at rest, regardless of whether they have cor pulmonale, and for all patients with cor pulmonale, regardless of their PaO2.

Humans↗
PubMed1983

Interstitial lung disease.

Under this umbrella are grouped a multitude of disorders--with broadly similar manifestations but widely differing etiologies--believed to affect more than 10 million people in the United States. Cases attributable to known causes are treatable. Most, however, are of uncertain etiology and respond poorly to treatment. An updated diagnostic and therapeutic approach is presented.

Alveolitis, Extrinsic Allergic↗
PubMed1982

Mechanism by which positive end-expiratory pressure increases cerebrospinal fluid pressure in dogs.

We investigated possible mechanisms by which positive end-expiratory pressure (PEEP) increased cerebrospinal fluid pressure (PCSF) in anesthetized mechanically ventilated dogs. In part I of the study, PEEP was applied in 5 cmH2O increments each lasting 1-2 min, before and after a snare separated the spinal from the cerebral subarachnoid space in each animal. Next, with the spinal cord still ligated, the dogs were ventilated without PEEP while superior vena cava pressure (PSVC) was raised in 5 cmH2O increments by means of a fluid reservoir connected with the superior vena cava. Cerebrospinal fluid pressure in the cisterna magna increased immediately and in parallel with PEEP before and after the spinal subarachnoid space was occluded and also increased when PSVC was raised independently; in all circumstances the increase in PCSF correlated closely with PSVC (r = 0.926). In part II of the study, arterial blood gases were drawn before and after PEEP was applied in the same increments and for the same duration as in part I. Cerebrospinal fluid pressure measured with a hollow skull screw again rose in parallel with PEEP, whereas arterial carbon dioxide tension rose only slightly at 60 s. In part III of the study, mean arterial pressure (Pa) was allowed to decrease with PEEP or was held constant by distal aortic obstruction and volume infusion. Cerebrospinal fluid pressure increased regardless of Pa, but the increase was greater when Pa was held constant than when it fell with PEEP. We conclude that PEEP increases PCSF primarily by increasing PSVC and decreasing cerebral venous outflow. This effect is augmented if cerebral arterial inflow is increased as well.

Animals↗
PubMed1982

A Starling resistor regulates cerebral venous outflow in dogs.

This investigation was undertaken to determine whether a Starling resistor or venous waterfall effect exists between the sagittal sinus and the cerebral veins such that increases in sagittal sinus pressure (Pss) do not abolish cerebral venous outflow and to examine two possible contributions of extracranial venous valves in regulating outflow. Anesthetized dogs were subjected to positive end-expiratory pressure (PEEP) before and after intracranial pressure (Pic) was elevated by inflation of an epidural balloon. PEEP raised Pss equally in all animals, but Pic and cerebral venous pressure (Pcv) increased less in the presence of intracranial hypertension. When Pss was low, passage of a catheter in the cerebral vein in and out of the sagittal sinus demonstrated an abrupt drop in pressure as the sinus was entered. When Pss was raised and lowered independently of superior vena caval pressure (Psvc) the changes in Pic and Pcv were less when Pss was decreased than when it was increased. Sustained increases and decreases in Psvc caused increases and decreases in Pcv, Pic, Pss, and external jugular venous pressure (Pejv) regardless of whether external jugular venous valves were present or absent. We conclude that a Starling resistor between the sagittal sinus and the cerebral veins regulates cerebral venous outflow when Pss is increased by PEEP and other maneuvers that raise Psvc. The waterfall maintains Pcv and Pic at normal levels when Psvc and Pss are reduced. Extracranial venous valves are not essential to this mechanism.

Animals↗
PubMed1982

The effects of expiratory positive airway pressure on the resolution of oleic acid-induced lung injury in dogs.

It is not known whether positive end-expiratory pressure (PEEP) merely improves gas exchange in patients with the adult respiratory distress syndrome or also affects the resolution of their lung injury. We examined the effects of expiratory positive airway pressure (EPAP), a form of PEEP, on 13 pairs of spontaneously breathing mongrel dogs with permanent tracheostomies that were subjected to acute lung injury from oleic acid. One member of each pair was treated with 10 cm H2O EPAP by means of a special valve attached to its tracheostomy tube; the other member breathed through the tracheostomy tube alone. The EPAP was applied 3 h after an intravenous injection of 0.06 ml/kg oleic acid and continued for a total of 21 h. Functional residual capacity (FRC) was increased to preinjury values in the EPAP-treated dogs at 3, 12, and 24 h compared with that in the untreated dogs. The PaO2 was higher and the venous admixture (Qva/QT) was lower in the EPAP-treated dogs compared with that in the untreated dogs at 3 and at 12 h. However, over the 7 days after removal of EPAP no significant differences were noted between the 2 groups in FRC, PaO2, Qva/QT, inert gas elimination profiles, mortality, final lung compliance to initial lung compliance differences, lung water to dry lung weight ratios, or histologic features. We conclude that EPAP improves gas exchange during its administration but has no demonstrable effect on the resolution of lung injury induced by oleic acid in dogs.

Animals↗
PubMed1981

Increasing intracranial pressure with air causes air embolism, not neurogenic pulmonary edema.

In an effort to duplicate a previous model of neurogenic pulmonary edema (NPE), we maintained intracranial pressure (PIC) at 20 Torr below mean arterial pressure in six closed-chested dogs anesthetized with alpha-chloralose and urethan. This was accomplished by infusing 1) isotonic saline (NS), 2) a gas mixture of 80% helium and 20% oxygen (HeO2), or 3) 100% carbon dioxide (CO2) through a trephined hole into the subdural space. Three more animals were studied with the same protocol after thoracotomy to permit Doppler examination for bubbles in the left pulmonary artery. Significant increases in pulmonary artery pressure, pulmonary vascular resistance, physiological shunt, dead space fraction, and hypoxemia were recorded when Pic was elevated by HeO2 infusion but not during infusion of NS or CO2. Pulmonary gas-bubble embolism was suggested by an increase in the fraction of helium in expired gas during HeO2 infusion and confirmed by Doppler recordings. We conclude that increasing Pic with air produces the physiological changes of air embolism; this is not a satisfactory model for investigating NPE.

Animals↗
PubMed1981

Effects of positive end-expiratory pressure on intracranial pressure in dogs with intracranial hypertension.

Positive end-expiratory pressure (PEEP) is used to improve oxygenation in patients with the adult respiratory distress syndrome. Nevertheless, this treatment may increase intracranial pressure (ICP) and be detrimental to certain neurosurgical patients. This clinical situation was simulated by administering PEEP to dogs with normal and elevated ICP. Increases in PEEP increased ICP in all animals. However, the presence of intracranial hypertension diminished the increase in ICP seen at a given level of PEEP. Cerebral perfusion pressure also fell less in the presence of intracranial hypertension than it did in the absence, although in the former situation cerebral perfusion pressure was at the lower limits of the range of cerebral autoregulation. These findings suggest that PEEP is no more detrimental to patients with elevated ICP than it is to patients whose ICP is normal, assuming that their cerebral autoregulation is not impaired.

Animals↗
PubMed1980

New developments in cardiopulmonary resuscitation.

The traditional concept of cardiopulmonary resuscitation (CPR) is that the heart is squeezed between the sternum and the spine during external cardiac massage to create a pressure gradient that forces blood from the heart to the periphery. Although the heart may actually be squeezed in some persons by this maneuver, a newer view of CPR holds that closed-chest compression produces a generalized rise in intrathoracic pressure that is applied to the pulmonary vascular bed as well as the heart. Thus, the heart does not serve primarily as a pump during external cardiac massage but instead acts as a conduit for blood from the lungs. Furthermore, flow into extrathoracic vessels depends on their tendency to remain open or to collapse: forward flow occurs across the head during CPR because a pressure gradient is developed between the carotid artery and the more compressible jugular vein. These ideas have potential clinical implications and greatly increase our understanding of the physiology of CPR.

Coronary Circulation↗
PubMed1980

Preoperative evaluation and perioperative management of patients with pulmonary disease.

Numerous studies in recent years have documented the increased risk of perioperative complications in patients with pulmonary disease. In assessing lung function before anesthesia and surgery, history and physical examination may be helpful but spirometry and blood gas determination are more accurate indicators of significant pulmonary disease. Risk apparently can be minimized by intensive chest therapy before and after surgery. Low-dose heparin therapy, in particular, is rec-mmended to prevent deep venous thrombosis and pulmonary embolism.

Blood Gas Analysis↗