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Biomedical subjects

D H Simmons

Publications and source records attributed to D H Simmons.

At least 37 records · Page 2Linked to original sources
PubMed1978

Effects of continuous positive airway pressure after oleic acid-induced lung injury in dogs.

The physiologic effects of continuous positive airway pressure (CPAP) of 5,10,15, and 20 cm H2O during spontaneous ventilation were studied in six anesthetized dogs with simulated respiratory distress syndrome (RDS) induced by iv infusion of oleic acid and in three normal controls. After oleic acid, mean PaO2 dropped to 63.6 +/- 3.1 mm Hg while breathing 100% oxygen and mean shunt fraction was 48.3 +/- 3.0%. PaO2 and shunt fraction improved significantly at the two highest levels of CPAP (e.g.,PaO2 271.3 +/- 41.3 mm Hg and shunt fraction 17.8 +/-2.2% at 20 cm H2O CPAP). Mean mixed venous PO2 rose from 37.4 +/- 1.5 mm Hg with no CPAP TO 60.8 +/- 3.1 mm Hg at 20 cm H2O CPAP. Tissue oxygenation appeared to improve during CPAP, since cardiac output, oxygen delivery, and serum lactate were not significantly affected and mixed venous PO2 rose significantly. However, significant hypoventilation occurred at all but the lowest level of CPAP, mean PaCO2 rising from 44.1 +/- 1.8 mm Hg with no CPAP to 77.6 +/-6.8 mm Hg at 20 cm H2O CPAP. The hypoventilation during CPAP is consistent with increased work of breathing due to a combination of decreased lung compliance and increased dead space ventilation due to rapid, shallow breathing.

Animals↗
PubMed1978

Diagnostic value of fiberoptic bronchoscopy in metastatic pulmonary tumors.

The fiberoptic bronchoscopic procedure (with brushings, washings, and biopsies) was performed and specimens of sputum were obtained before the procedure in 37 patients with cancer metastatic to the lung. Of the 37 patients studied, endobronchial lesions were visualized at bronchoscopic examination in 14 (group 1), and no endobronchial lesion was seen in 23 (group 2). The yield of bronchial brushing and washings was not significantly different in group 1 and 2, whereas examination of sputum obtained before the bronchoscopic procedure and bronchial biopsy in group 1 yielded higher results than the same procedures in group 2. The radiographic findings did not influence the yield with any of the bronchoscopic procedures. The overall positive diagnostic yield from fiberoptic bronchoscopic procedures among these patients was 54 percent (20/37), regardless of their bronchoscopic or radiologic findings.

Biopsy↗
PubMed1977

Effects of hydration and physical therapy on tracheal transport velocity.

A new tracer method for quantitative measurement of tracheal transport velocity (mm per min) in dogs has been described. Using the same technique, the effects of dehydration, rehydration, postural drainage, and chest percussion on tracheal transport velocity were studied. Mean tracheal transport velocity decreased significantly (14.1 +/- 1.4) after dehydration (P less than 0.05) and reverted to normal (19.0 +/- 1.3) with rehydration in 10 dogs. After postural drainage in 7 dogs, mean tracheal transport velocity increased 39.7 +/- 1.78 (SE) per cent (P less than 0.01). After chest percussion in 6 dogs, mean tracheal transport velocity increased 50.9 +/- 1.22 (SE) per cent. With combined postural drainage and chest percussion, mean tracheal transport velocity increased 50.0 +/- 0.32 (SE) per cent. Although maximal improvement occurred after the combined therapy, the changes were not significantly different from those observed with each therapy alone. These therapeutic measures have been used empirically in the past. The present study gives some objective evidence for their beneficial effects in anesthetized dogs.

Animals↗
PubMed1977

A systematic error in the determination of blood PCO2.

An analysis was made of the effect of sodium heparin solution on the determination of arterial blood PCO2, pH, and bicarbonate. Dilution of blood by heparin solution did not affect the pH of blood samples significantly but reduced the measured PCO2 and th calculated bicarbonate and base excess in direct proportion to the amount of dilution. Used in the usual quantities as an anticoagulant, lubricant, and filler of needle and syringe dead space, heparin solution caused a 17 per cent or greater reduction in PCO2 and bicarbonate in approximately 17 per cent of the arterial blood samples currently received for analysis in a university hospital laboratory. Such unrecognized errors could cause misinterpretations of acid-base status. Completely filling the sampling syringe with blood and using a small-gauge needle will reduce the error.

Bicarbonates↗
PubMed1977

Measurement of mucociliary transport velocity in the intact mucosa.

A new method for measuring the velocity of the tracheal mucous transport rate in anesthetized dogs is described. The length of the trachea is determined with the bronchoscope as the distance between the larynx and the lower end of the trachea at the level of the carina. A small volume (0.04 to 0.1 ml) of albumin microspheres 5 mgm to 7 mum in diameter labeled with radioactive 99m technetium or 113m indium is deposited on the mucosal surface at the lower end of the trachea via a catheter placed in the inner channel of a fiberoptic bronchoscope. The movement of the microspheres towards the larynx is visualized and recorded using a scintallation camera (Picker Dyna Camera) with a large field of view (30 cm in diameter) for 30 to 60 minutes, depending upon the time required for the spheres to reach the top of the trachea. Polaroid pictures are made immediately and every minute thereafter until the activity reaches the larynx. The data are also recorded and stored on magnetic tape for subsequent analyses by computer. The length in millimeters divided by the time in minutes gives the transport velocity rate. The mean velocity was found to be 19.2 +/- 1.6 mm/min (+/- SE).

Animals↗
PubMed1977

Hemoptysis: diagnosis and management.

Hemoptysis is one of the most important symptoms of cardiopulmonary disease-first, because bleeding even in small amounts may indicate the presence of such serious diseases as bronchogenic carcinoma or active tuberculosis, and second, because untreated massive hemorrhage is associated with a high mortality rate. The cause of hemoptysis may be suggested by the history, physical examination or chest x-ray findings, but often diagnostic procedures such as bronchoscopy, bronchography and pulmonary angiography are needed for definitive diagnosis. The importance of early localization of the bleeding site and surgical intervention in patients with massive hemoptysis is stressed.

Adult↗
PubMed1976

Mixed venous oxygen tension and hyperlactatemia. Survival in severe cardiopulmonary disease.

Mixed venous oxygen tension (PVo2), cardiac output (Q), and arterial oxygen tension (Pao2) were measured in 20 patients with severe cardiac or pulmonary disease or both to determine which of these variables would best predict hyperlactatemia and survival. There was no correlation between Pao2 and either hyperlactatemia or survival, possibly because all oxygen tensions were greater than 40 mm Hg. There was a good correlation between Q and both hyperlactatemia and survival, and a slightly better correlation between PVo2 and both hyperlactatemia and survival. Mixed venous oxygen tension, a reflection of both Pao2 and Q, was a better predictor of hyperlactatemia and death than either arterial Pao2 or Q alone. It is also more easily measured and, therefore, more clinically useful than either Q, as a predictor of anaerobiosis and survival, or blood lactate concentration, as a predictor of survival. A mixed venous oxygen tension below 28 mm Hg was usually associated with hyperlactatemia and was always associated with death.

Aerobiosis↗
PubMed1975

Nitrogen dioxide and the erythrocyte redox state.

Normal human erythrocytes were exposed for two hours at 38 C to an atmosphere of air containing variable concentrations of nitrogen dioxide, in order to detect any primary cytoplasmic effect of NO2 on the calculated oxidation-reduction (redox) ratio ([NAD+]/[NADH]) of a mitochondria-free cell. Substantial increases in the redox ratio were noted only when NO2 concentrations exceeded 15 ppm. In the range of 15 to 500 ppm NO2, the increase in the redox ratio significantly correlated with the NO2 concentration (r=.71; p less than .01). Intracellular to extracellular anion distribution ratios for chloride, lactate, and pyruvate were similar in NO2 and non-NO2 exposed cells, suggesting absence of a substantial hemolytic effect. These data identify a direct cytoplasmic NO2-induced biochemical change that may be mediated by a mechanism other than lipid peroxidation. Alteration of hemoglobin or NAD-NADH-dependent enzyme activity is suggested.

Cell Fractionation↗
PubMed1975

Mechanism of arterial hypoxemia following pulmonary thromboembolism in dogs.

Mongrel dogs (29) were anesthetized, paralyzed, and ventilated at a constant minute volume. AaD02 breathing air and 100% O2, venous admixture breathing air (Qva/Qt) and 100% O2 (Qs/Qt), single-breath diffusing capacity for CO (DLCO), and total pulmonary resistance (RL) and pulmonary compliance (CL) were measured before and after pulmonary embolization with autologus in vivo venous thrombi. Nine dogs were heparinized before embolization. In the 20 nonheparinized dogs AaDo2 breathing air increased from 11 to 26 mmHg, Qva/Qt from 4 to 22%, and Qs/At from 5 to 8%. DLCO decreased 24%, RL increased 43%, and CL fell 30%. In the nine heparinized dogs AaDo2 breathing air increased from 8 to 13 mmHg and Qva/Qt from 3 to 8%; Qs/Qt did not change. DLCO decreased 31%; RL and CL did not change significantly. The increase in Qva/Qt of 5% in the heparinized dogs was significantly less (P smaller than 0.001) than the increase of 18% in the nonheparinized dogs. These findings suggest that arterial hypoxemia following thromboembolism is due to ventilation-perfusion inequality caused by changes in lung mechanics.

Animals↗
PubMed1975

Pulmonary edema and wheezing after pulmonary embolism.

A young, pregnant woman with angiographically proved pulmonary emboli developed pulmonary edema and wheezing without evidence of left ventricular failure. This cast study points out the unusual association of pulmonary embolism with pulmonary edema, wheezing, and hyper-reactive airways in a patient with a positive family history of allergy, but no antecedent history of bronchospasm. Mechanisms for the occurrence of noncardiogenic pulmonary edema and wheezing after pulmonary embolism are reviewed.

Adult↗
PubMed1975

Flexible fiberoptic pleuroscopy: pleural and lung biopsy.

While diagnostic procedures are available to explore most of the body cavities for diagnosis and treatment, examination of the pleural cavity remains difficult, mainly because the negative pressure in the pleural cavity makes direct examination impossible without collapsing the lung. The ability to diagnose pleural and pulmonary disease by conventional techniques, such as blind pleural and lung biopsy, cytology of bronchial washings and brushings, radiologic techniques or cultures is limited and frequently fails to provide an accurate diagnosis. Exploratory thoracotomy, with a relatively high complication rate, remains the method of choice in many cases. We have devised a new technique for exploring the pleural cavity under direct vision while avoiding lung collapse, using a modified flexible fiberoptic bronchoscope introduced into the pleural cavity through a specially designed cannula.

Animals↗
PubMed1975

Double-blind comparison of acute bronchial and cardiovascular effects of oral terbutaline and ephedrine.

Acute effects of oral terbutaline (5 mg), ephedrine (25 mg) and placebo on bronchial dynamics, heart rate, systolic and diastolic pressure and arterial blood gases at rest were compared over a period of 7 hours in 20 subjects with bronchial asthma using a double-blind crossover technique. Both terbutaline and ephedrine caused significant bronchodilation, but the effect of terbutaline on specific airway conductance (SGA) was significantly greater (peak mean increase in SGA 0.069 vs 0.027 L/sec/cm H2O/L), had an earlier onset (30 minutes vs 1 hour) and lasted longer (7 hours vs 4 hours) than that of ephedrine. Slight but significant increases in arterial Po2 were noted following institution of both ephedrine and terbutaline, suggesting improvement in ventilation-perfusion relationships. Both drugs caused modest but statistically significant increases in heart rate of 8.4-10.9 beats/min and the mean peak increase following terbutaline (8.4 beats/min) was comparable to that following ephedrine. In constrast to ephedrine, terbutaline caused significant, although slight, increases in systolic pressure and decreases in diastolic pressure, indicating that this drug, in the dose recommended for clinical use, is not free of cardiovascular effects.

Adolescent↗