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Biomedical subjects

E E Davies

Publications and source records attributed to E E Davies.

At least 19 recordsLinked to original sources
PubMed1986

A rapid rebreathing method for measurement of pulmonary gas volume in humans.

We have developed a rapid gas-dilution technique, with which pulmonary gas volume can be measured in only 20 s, even in the presence of maldistribution of ventilation. The subject rebreathes from a 0.75-liter anesthetic bag filled with 10% He and 30% O2 in argon. Breath-by-breath flow-weighted inspired concentrations of all gases present are calculated from continuous measurement by mass spectrometry. Insoluble gas concentrations are corrected continuously for shrinkage of the system volume. By use of these corrected values a mathematical extrapolation predicts the equilibrium concentration for He in the absence of complete mixing. Validation of the technique was carried out by comparing volumes calculated from the predicted equilibrium value with those obtained by whole-body plethysmography in 7 normal subjects and 12 patients with lung disease. In normal subjects equilibrium was usually attained within the 20 breaths and no extrapolation was required. In most of the patients, however, equilibrium was not reached and the use of the extrapolation technique increased the proportion of the lung volume measured by gas dilution from 0.82 +/- 0.16 (SD) to 0.95 +/- 0.12 of that measured by plethysmography.

Adult↗
PubMed1986

Modification of pulmonary gas mixing by postural changes.

Mixing for two gases of markedly different gaseous diffusivity, helium (He) (mol wt = 4) and sulfur hexafluoride (SF6) (mol wt = 146) has been studied by a rebreathing method in different postures. In nine normal subjects duplicate measurements were made in the erect (seated), supine, and lateral decubitus posture, at a constant tidal volume (700 ml) and frequency (1 Hz) starting from functional residual capacity (FRC). Additional measurements were made on four of the subjects, rebreathing seated erect at a volume similar to the relaxed FRC supine and supine at a volume similar to the relaxed FRC seated. In the supine posture the mean breath number to reach 99% equilibrium (n99), was not significantly different for the two gases, 8.9 for He and 9.8 for SF6. There was a difference (P less than 0.01) when erect; n99 (He) = 8.2 and n99 (SF6) = 10.9. The greatest He-SF6 difference (P less than 0.001) was in the lateral decubitus position n99 (He) = 10.1 and n99 (SF6) = 15.9. The mean relaxed FRC as percent of seated was 71% supine and 75% in lateral decubitus posture. Rebreathing seated at a lower volume did not abolish the He-SF6 mixing difference nor did rebreathing at a higher volume when supine induce a He-SF6 mixing difference. Thus the effect of posture on gas mixing cannot be due solely to lung volume and must represent a convective and diffusive dependent change in the distribution of ventilation per unit lung volume.

Adult↗
PubMed1979

Endodontic perforations which resulted in alveolar bone loss. Report of five cases.

Five cases in which perforations of mandibular molars into the furca occurred during endodontic instrumentation of the canal are presented. This resulted in alveolar bone loss. All were relatively asymptomatic, which could present a problem in diagnosis of the periodontal defect. The prognosis is questionable. The only tooth retained was treated surgically by an apically positioned flap and opening of the furca area to make it accessible to cleansing. The best treatment is the avoidance of the perforation. This is accomplished by considering the configuration of the canals and the size of the reamer than can follow it. Overinstrumentation with an endodontic instrument that is too large in diameter should be avoided.

Adult↗
PubMed1978

Alveolar bone loss associated with vertical root fractures. Report of six cases.

Six cases of vertical root fractures accompanied by vertical bone loss are presented. Possible causes for these fractures are suggested. Four vertical fractures probably resulted from the use of excessive pressure at the time of obturation of the canals. One vertical root fracture may have been caused by the cementation of a post, and another may have been caused by the cementation of an inlay in an endodontically treated tooth. All of the fractures resulted in alveolar bone loss to the apical extent of the fracture lines. The definitive treatment in each case was extraction of the tooth or root amputation. In one case successful treatment was accomplished by apically positioning the flap.

Adult↗
PubMed1978

"The pill".

Explore the source record for details and available documents.

Dental Plaque↗
PubMed1977

Oral health of airmen: analysis of panoramic radiographic and Polaroid photographic survey.

An oral health survey of 5,783 basic airmen was conducted. In this study, emphasis was placed on detection of periodontal disease. Numerous pathologic conditions were found and recorded. In addition, the presence or absence of evidence of previous dental care and its nature were reported. We believe that panoramic radiographs and Polaroid intraoral photographs have merit in mass screening of large numbers of persons for the detection of periodontal disease. Through the use of these diagnostic aids, various degrees of periodontal disease could be diagnosed. Other pathologic entities that might have been missed with routine dental radiographs were observed. However, although the diagnostic aids used in this report are a helpful adjunct, in their present state of development they should not be used to replace standard dental radiographs and clinical examination.

Aerospace Medicine↗
PubMed1976

Local regulation of pulmonary blood flow and ventilation-perfusion ratios in the coatimundi.

Small catheters (ca. 3 mm diam at tip) were wedged in subsegmental bronchi in anesthetized coatimundi (Nasua nasua) during spontaneous breathing. Mixed expired gases of a group of lobules were sampled continuously without contamination from neighboring units, and local tidal volume, frequency, carbon dioxide production, and oxygen consumption were measured, as well as mixed venous PO2 and PCO2. Local ventilation-perfusion ratio, alveolar PO2, PCO2, and blood flow were calculated. There was a 22% reduction (range 15-38) in local perfusion (as percent of flow at PAO2 100 mmHg) per 10 mmHg fall in local alveolar oxygen tension over the PAO2 range 150-36 mmHg. Local hypercapnia had little effect on local flow. Local tidal volume (ca. 1% of total tidal volume) was unaffected by changes in alveolar gas tensions. The contribution of vasoconstriction or vasodilatation, as a negative feedback system, to the stability of local PAO2 was greatest close to the physiologic range (65-85 mmHg) falloderate efficiency.

Animals↗
PubMed1976

Estimation of cardiac output by an N2O rebreathing method in adults and children.

A nitrous oxide rebreathing method was used to measure recirculation time and cardiac output (as pulmonary blood flow) in adults and children during exercise. The method was compared with the indirect (CO2) Fick rebreathing method in almost simultaneous measurements of cardiac output. Recirculation time varied from about 15 s at rest to 8.5 s at high levels of exercise, and was slightly longer in children than adults. Cardiac output estimated by both methods was within the normal range for children and adults, being lower for a given oxygen consumption in children. For the adults the mean intrasubject variability of the N2O rebreathing method, measured as the coefficient of variation of cardiac output, was in the range of 6-8% at all levels of work. This was lower than reported for other N2O rebreathing methods, and similar to values based on the indirect (CO2) Fick, direct (O2) Fick, and dye-dilution methods of estimating cardiac output. The method is therefore proposed as a noninvasive technique suitable for rapid, accurate, and reproducible measurements of cardiac output.

Adult↗