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Biomedical subjects

A H Morris

Publications and source records attributed to A H Morris.

At least 91 records · Page 5Linked to original sources
PubMed1986

Determination of lung water content and distribution by nuclear magnetic resonance imaging.

NMR imaging techniques are applicable to the assessment of lung water content and distribution because the NMR signal is, under certain conditions, proportional to tissue proton density. NMR imaging is noninvasive, easily repeatable, free from ionizing radiation, and particularly suitable for the assessment of spatial lung water distribution. Lung water content and distribution have been estimated in excised animal lungs and in intact dead or living animals, under normal conditions and in various types of experimental pulmonary edema. Excised human lungs and human subjects have also been studied. Published data indicate that measurements of lung water content by NMR imaging techniques are feasible. These techniques estimate lung water spatial distribution with satisfactory accuracy and excellent resolving power. The application of NMR imaging techniques poses several problems and limitations, but available data suggest that most of the problems can be solved. NMR imaging has the potential to become a powerful tool for lung water research. Prospects of clinical application are also encouraging; numerous applications can be foreseen, although lack of mobility of NMR imaging systems may be a significant limitation in critical care medicine.

Animals↗
PubMed1986

Genetics of Hunter syndrome: carrier detection, new mutations, segregation and linkage analysis.

We have investigated 31 families segregation for Hunter Syndrome in order to advance our understanding of the genetics of this disease. The hair root test for the diagnosis of carriers of Hunter Syndrome was improved by the adoption of a new diagnostic index that distinguishes between carrier and normal females better than previous methods of analysis. One hundred and eleven female relatives of the affected children were tested by such procedures. This showed that seven out of 31 mothers were not carriers (22.6%), thus suggesting a small deficit of new mutation relative to the expectation that 33% of lethal, recessive alleles arise anew in a population at equilibrium at a sex-linked locus with equal mutation rates in male and female gametogenesis. The difference, however, is not statistically significant. The age of the parents of new mutants was slightly but significantly raised. Nevertheless, the independent increase in the age of the fathers of new female mutants was not statistically significant. Finally, a deficit of affected males was observed. This was significant and suggests the possibility of intrauterine loss of some affected males. Linkage analysis between the Hunter Syndrome locus, three polymorphisms in the Factor IX gene and the anonymous polymorphic probes 52A and DX13 showed that the Hunter locus is fairly closely linked to DX13, and hence distal to the Factor IX gene, while no linkage was observed with the 52A polymorphic site. The maximum lod score for the linkage between factor IX and the Hunter Syndrome locus was 0.424 at theta = 0.25; and that for the linkage between the Hunter Syndrome locus and DX13 was 3.01 at theta = 0.1.

Age Factors↗
PubMed1986

A prospective study of acute hypoxic respiratory failure.

A prospective study of acute hypoxic respiratory failure was carried out by nine centers in a collaborative NIH study from 1 September 1975 to 1 March 1977. Serious hypoxic respiratory failure was defined in 713 patients by the presence of (1) endotracheal intubation and positive airway pressure for at least 24 hours, and (2) the administration of at least 50 percent oxygen. The 490 patients between 12 to 65 years of age had a mortality of 61 percent. Mortality increased with increasing organ failure: one organ system failure (lung only) 40 percent; two, 54 percent; three, 72 percent; four, 84 percent, five, 100 percent. Only 103 patients died with isolated lung failure, whereas 353 died of a combination of lung and other organ failures. Both the overall mortality (66 percent) and the mortality of those with only isolated lung failure (40 percent) were much higher than anticipated for the selection criteria.

Acute Disease↗
PubMed1985

When should we request radionuclide brain scans in elderly patients?

The radionuclide brain scans performed on a gamma camera (GC scans) in 146 patients over 65 years of age during a 6-month period are reviewed. Forty-four scans (30.1%) were reported as showing an abnormality. Three patients subsequently underwent surgery and drug therapy was commenced in 11 cases. However, in most cases the GC scan proved unhelpful in the patients' management. The usage and role of GC scanning in elderly patients admitted with a neurological disorder is examined.

Aged↗
PubMed1985

Granulocyte aggregation in adult respiratory distress syndrome (ARDS)--serial histologic and physiologic observations.

Although a number of studies have suggested that granulocyte sequestration is an important pathophysiologic event in ARDS, histologic evidence of aggregated granulocytes in the pulmonary microvasculature is limited, and serial histologic data have not been reported with physiologic measurements. We report a patient with ARDS who demonstrated microvascular granulocyte aggregation and lung edema in sections of a lung biopsy obtained seven days after the onset of symptoms. Pulmonary vascular resistance and pulmonary capillary wedge pressure were normal immediately before the biopsy. A second biopsy performed 12 days later showed decreased lung edema and no evidence of intravascular leukostasis. This case provides histologic support for the hypothesis that granulocyte aggregates contribute to pulmonary edema associated with ARDS.

Adult↗
PubMed1985

Frequency of wedge pressure errors in the ICU.

Using 94 flow-directed pulmonary artery catheters in 53 ICU patients, we obtained prospectively 282 pulmonary artery wedge pressure (WP) measurements from 286 attempts. After catheter manipulation, 96% of these WP measurements were ultimately free of technical problems, and 84% were confirmed by aspiration of pulmonary capillary blood from the wedge position. The 95% confidence interval for repeated measurements of WP in stable ICU patients was 4 mm Hg. The WP measurement error was defined as the difference between unconfirmed and confirmed WP pairs obtained from stable patients. The probability of encountering a WP measurement error of at least 4 mm Hg was 33% for the 93 WP measurements with technical problems, 5% for the 189 WP measurements without technical problems, and 14% for the entire set of 286 WP measurement attempts. Quality control procedures, including dynamic response testing, easily identified most errors.

Adolescent↗
PubMed1985

Wedge pressure confirmation by aspiration of pulmonary capillary blood.

In order to define the contribution of wedge blood composition to pulmonary artery wedge pressure (WP) measurement, we made 28 comparisons of WP and left atrial pressure (LAP) in 16 stable patients with pulmonary or cardiac failure after cardiac surgery. All technical problems associated with initial WP measurements were eliminated before simultaneously recording WP and LAP. Wedge blood samples (w), withdrawn from the distal pulmonary artery catheter port in the balloon occlusion position, were compared with paired arterial (a) blood samples. Wedge blood was defined as pulmonary capillary blood when the following three wedge-arterial gradient criteria were satisfied: (PwO2 - PaO2) greater than or equal to 19 torr; (PaCO2 - PwCO2) greater than or equal to 11 torr; and (pHw-pHa) greater than or equal to 0.08. When capillary blood was withdrawn from the wedge position, there was no difference between WP and LAP measurements. When wedge blood failed to satisfy capillary criteria, WP was significantly (p less than .05) different from LAP. Aspiration of capillary blood from the wedge position in ICU patients confirms that WP faithfully reflects LAP. It identifies those differences between WP and LAP which remain after technical problems are eliminated.

Capillaries↗
PubMed1985

Asymmetric spin echo sequences. A simple new method for obtaining NMR 1H spectral images.

The nuclear magnetic resonance (NMR) signal decay produced by reversible tissue-induced dephasing of the magnetization components in the transverse plane (reversible tissue-induced dephasing) was measured and expressed as a function of a new transverse relaxation time T'2 (T2 prime) for samples of rat liver, retroperitoneal fat, inflated lung, and corn oil. Simple exponentials did not adequately describe the observed NMR signal decay. Inflated lung demonstrated the most rapid signal decay (T'2 = 4.8 ms) followed by retroperitoneal fat (T'2 = 16 ms). No reversible tissue-induced dephasing was observed in liver (T'2 immeasurably long). In tissues which contain both fat and water, the chemically shifted 1H resonance peaks from -OH and -CH-are in phase with symmetric spin echo sequences but out of phase with asymmetric sequences. The interference of these two peaks produces a beat pattern with asymmetric sequences. Subtraction images obtained from paired symmetric- and asymmetric-sequence images accurately (r = .96) reflect T'2 and can be used to indicate the presence of fat. In vivo subtraction images of ethionine-induced fatty rat livers were significantly different from similar in vivo images of normal rat livers (P less than .0005). Since for each pixel of a subtraction image, the magnitude of the difference signal should be approximately proportional to the ratio of hydroxyl and alkyl protons, this simple spin echo sequence modification may obviate the need for more time-consuming 3-dimensional Fourier transform proton chemical shift images.

Adipose Tissue↗
PubMed1985

A new nuclear magnetic resonance property of lung.

Inflated lung has a nuclear magnetic resonance (NMR) free-induction decay (FID) which is short compared with that of collapsed lung and those of other body tissues. An almost identically short FID is obtained from a slurry of 5-micron alumina particles in water. Interfaces between air and water in lung and between alumina and water in the slurry appear to be the source of spatial internal magnetic inhomogeneities which produce NMR line broadening and the short FID. Paired images that included lung, taken with paired symmetric and asymmetric NMR spin-echo sequences, permit the generation of an image, by subtraction, of the lung isolated from surrounding tissue. These new lung images are neither proton density, T1 (spin-lattice relaxation time), nor T2 (spin-spin relaxation time) images. They complement current NMR images and provide information about regional lung inflation. This previously unrecognized NMR property of lung tissue has potential application in NMR imaging, in quantitative determination of lung water and its distribution, and in the quantitation of regional lung inflation.

Animals↗
PubMed1985

Acute respiratory failure caused by primary pulmonary coccidioidomycosis. Two case reports and a review of the literature.

Acute respiratory failure caused by infection with Coccidioides immitis is a rare, usually fatal, event. We report 2 patients who survived acute respiratory failure caused by primary pulmonary coccidioidomycosis. We attribute the severity of illness to a large inoculum of organisms. Their treatment included antifungal therapy with amphotericin B and diuresis to decrease noncardiogenic pulmonary edema. Coccidioidomycosis causing respiratory failure may be more frequent than currently clinically appreciated and may result from primary pulmonary coccidioidomycosis, miliary pulmonary disease, or as part of the multisystem organ failure seen in fungemic patients.

Adult↗
PubMed1985

Adult respiratory distress syndrome: successful support with continuous negative extrathoracic pressure.

We describe the use of continuous negative extrathoracic pressure to treat successfully the adult respiratory distress syndrome in a 19-yr-old woman who resisted the application of positive airway pressure. Arterial hypoxemia was reversed with -26 cm H2O of extrathoracic pressure, produced by a modified Emerson iron lung. Cerebral and renal functions were maintained, and barotrauma did not occur. The patient required continuous negative extrathoracic pressure for 9 days; 12 days after admission, she was discharged. This case indicates that negative extrathoracic pressure therapy can be an effective and safe alternative to positive airway pressure for the management of selected patients with adult respiratory distress syndrome.

Adult↗
PubMed1984

Frequency of technical problems encountered in the measurement of pulmonary artery wedge pressure.

A total of 2711 pulmonary artery wedge pressure (WP) measurement attempts were made prospectively from WP recordings in 44 (30 men) critically ill patients, using 77 flow-directed catheters. Of these, 322 (12%) failed to yield a WP measurement, and 521 (18%) were associated with technical problems. One half of these technical problems were due to poor dynamic response or damped pressure tracings; other problems included balloon overinflation, partial WP, and inability to aspirate blood from the pulmonary artery (PA) port. Only 50% of wedge blood sampled at the time of initial PA catheterization yielded capillary blood (PO2 greater than or equal to 10 torr higher than PaO2). In 12 stable patients in whom paired measurements were available, there were clinically important differences (-13 to +22 torr) between paired WP measurements made before and after rapid correction of technical problems. Technical problems are common and may be associated with clinically important errors. Those due to poor dynamic response are easily and rapidly detected at the bedside.

Adult↗
PubMed1984

Comparative radiographic features of community acquired Legionnaires' disease, pneumococcal pneumonia, mycoplasma pneumonia, and psittacosis.

The features of the chest radiographs of 49 adults with legionnaires' disease were compared with those of 91 adults with pneumococcal pneumonia (31 of whom had bacteraemia or antigenaemia), 46 with mycoplasma pneumonia, and 10 with psittacosis pneumonia. No distinctive pattern was seen for any group. Homogeneous shadowing was more frequent in legionnaires' disease (40/49 cases) (p less than 0.005), bacteraemic pneumococcal pneumonia (25/31) (p less than 0.01) and non-bacteraemic pneumococcal pneumonia (42/60) (p less than 0.05) than in mycoplasma pneumonia (23/46). Multilobe disease at presentation was commoner in bacteraemic pneumococcal pneumonia (20/31) than in non-bacteraemic pneumococcal pneumonia (15/60) (p less than 0.001) or legionnaires' disease (19/49) (p less than 0.025). In bacteraemic pneumococcal pneumonia multilobe disease at presentation was associated with increased mortality. Pleural effusions and some degree of lung collapse were seen in all groups, although effusions were commoner in bacteraemic pneumococcal pneumonia. Cavitation was unusual. Lymphadenopathy occurred only in mycoplasma pneumonia (10/46). Radiographic deterioration was particularly a feature of legionnaires' disease (30/46) and bacteraemic pneumococcal pneumonia (14/27), and these groups also showed slow radiographic resolution in survivors. Radiographic resolution was fastest with mycoplasma pneumonia; psittacosis and non-bacteraemic pneumococcal pneumonia cleared at an intermediate rate. Residual intrapulmonary streaky opacities remained in over a quarter of survivors from legionnaires' disease (12/42) and bacteraemic pneumococcal pneumonia (5/19).

Adolescent↗
PubMed1984

Determination of lung water content and distribution by nuclear magnetic resonance.

The present study was designed to determine the value of nuclear magnetic resonance (NMR) imaging as a technique for quantifying lung water distribution and to estimate the degree of spatial resolution achieved by this technique. The spatial distribution of water was determined in six small (0.76 ml) rat lung tissue specimens by an NMR line-scan technique. After NMR imaging, each lung specimen was frozen and subdivided into slices; the gravimetric lung water content for each lung slice was compared with the integrated NMR water content over the volume corresponding to the same lung slice. In each tissue specimen, NMR and gravimetric lung water values were significantly correlated; the correlation coefficient for the pooled data for all six lung specimens was 0.91 (P less than 0.01). In two lung specimens, NMR values tended to be slightly higher than the gravimetric values. The magnitude of the difference between NMR and gravimetric values was generally less than 20% and only occasionally exceeded 25%. Our results suggest that the NMR-imaging method provides satisfactory estimates of lung water content and its distribution; the resolving power of the technique is excellent, as shown by its ability to detect water content differences between lung tissue slices of volume as small as 0.076 ml.

Animals↗