Showing papers by "Alan H. Morris published in 1985"

Frequency of wedge pressure errors in the ICU.

Abstract: 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.

A new nuclear magnetic resonance property of lung

Abstract: 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.

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

Abstract: 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.

Standardization of computation of single-breath transfer factor.

Abstract: The transfer factor (TLCOsb) is currently widely used as a lung function test. Although the test maneuver itself is well described and uniformly approached by most workers, the computation technique varies considerably. Significant changes in the TLCOsb are induced by correcting for: blood hemoglobin concentration [Hb], apparatus and anatomic dead space (VD), alveolar gas sample dead space (VDbag), carboxyhemoglobin concentration (COHb), alveolar carbon dioxide fraction (FACO2), initial inspired gas (VI) conditions, and breath-hold time (t). The quantitative impact upon TLCOsb of the presence or absence of corrections was calculated using TLCOsb measurements from 245 normal subjects. The average change (%) in computed TLCOsb induced by correcting for the above variables is: Hb (+8%); VD (-8%); VDbag (-0.3 to -6%); COHb (+X% for X% COHb); FACO2 (+5%); VI (+4%); t (+7%). Since corrections are made by some laboratories and not by others and since no uniformity exists concerning the corrections to be made, it is possible for two laboratories to choose their computation routines in such a way that they would compute, from the same test results, TLCOsb values which differ by 41%. Standardization of the TLCOsb computation technique is needed.

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

Abstract: 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.

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

Abstract: We describe the use of continuous negative extra-thoracic 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 aontinuous 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.,

Wedge pressure confirmation by aspiration of pulmonary capillary blood.

Abstract: 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.