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Biomedical subjects

M W Thomas

Publications and source records attributed to M W Thomas.

29 records · Page 2Linked to original sources
PubMed1979

Longitudinal mixing in pulmonary airways: comparison of inspiration and expiration.

The increase in dispersion of an inert tracer bolus of helium (He) or sulfur hexafluoride (SF6) was used as a direct and noninvasive measure of longitudinal mixing in the conducting airways. Over a 0- to 260-ml range of bolus penetration, a change in the inspiratory flow from 0.35 to 1.2 l/s did not affect the dispersion of He and SF6, this implies that pure convective dispersion is the dominant inspiratory mixing process. The same change in expiratory flow caused a significant increase in SF6 dispersion only; this indicates that Taylor dispersion is important during expiration. In experiments performed at a fixed penetration of 160 ml and with SF6 only, the inspiratory and the expiratory flows were independently varied from 0.18 to 5.4 l/s. Though the bolus dispersion exhibited a mildly negative correlation with inspiratory flow, it was linearly correlated with expiratory flow. From the former result we conclude that although inspiratory mixing occurs primarily by convective dispersion, there is also a small degree of turbulent dispersion. The latter result confirms that expiratory mixing is primarily due to Taylor dispersion.

Helium↗
PubMed1978

Longitudinal mixing in pulmonary airways--normal subjects respiring at a constant flow.

We have measured the impulse response of helium and sulfur hexafluoride in the airways of five normal human subjects at a respiratory flow of 400 ml/s. The longitudinal mixing of the inert gases was characterized by the increased volume variance of the expired concentration response. This parameter was measured over the largest possible range of airway penetrations, 30-290 ml. Employing a symmetrical model of the airway geometry, we have computed the values of a mean mixing coefficient from the volume variance data. This mixing coefficient is largest in the large airways and decreases rapidly with increasing penetration; it may be as much as 4,000 times greater than the molecular diffusivity; and it is relatively independent of the inert gas tested, at least up to an airway penetration of 180 ml. These observations are consistent with several preivously proposed mixing mechanisms including axial streaming, turbulent dispersion, and mixing by geometric asymmetry. However, the latter observation appears to rule out the importance of laminar dispersion since mixing by this mechanism is inversely dependent on the molecular diffusivity.

Humans↗
PubMedDate not supplied

Significance of the Heineke-Mikulicz pyloroplasty in the treatment of gastric dilatation-volvulus. A prospective clinical study.

Twenty-six dogs with gastric dilatation-volvulus (GDV) were stabilized medically, followed by tube gastrostomy and gastropexy. In 13 dogs, a Heineke-Mikulicz pyloroplasty was also performed. Complications and recurrences were monitored during the immediate postoperative period and for 5 to 31 months thereafter. Barium gastrograms and contrast radiographs of the stomach were evaluated at week 1 and months 5 to 31. Significantly fewer dogs without pyloroplasty had complications during the immediate postoperative period. There were no differences in the long-term complication rates. Radiographic evaluations of the width of the pylorus, the size of the stomach, and the rate of gastric emptying showed no differences between dogs with and without pyloroplasty at any evaluation period. The Heineke-Mikulicz pyloroplasty increased the immediate postoperative complication rate after surgical fixation of the stomach for the treatment of GDV. It did not appear to influence the long-term outcome of the surgical treatment of this disease. The Heineke-Mikulicz pyloroplasty is not recommended in the treatment of GDV unless pyloric outflow obstruction can be demonstrated.

Animals↗
PubMedDate not supplied

Gastric conduit urinary diversion in normal dogs. Part I, Upper urinary tract structure, function, and sepsis.

The urinary bladder of 10 clinically normal dogs was excised and the ureters were implanted into an isolated, vagotomized gastric segment derived from the fundic region of the stomach. The gastric segment was closed to form a conduit. Continence was maintained with a modified Kock "nipple valve" created from an isolated segment of ileum. Four dogs were euthanatized by day 30 because of complications related to the early onset of renal failure and electrolyte alterations. Six dogs were euthanatized on day 150. Ureteral dilatation, hydronephrosis, and decreased endogenous creatinine clearance rates were measured in all dogs at the end of the survival period. Pyelonephritis was diagnosed histologically in seven dogs. Positive renal cultures were obtained from seven dogs at necropsy. It was concluded that gastric conduit urinary diversion is unsatisfactory for long-term or short-term clinical use in dogs.

Animals↗
PubMedDate not supplied

Gastric conduit urinary diversion in normal dogs. Part II, Hypochloremic metabolic alkalosis.

Gastric conduit urinary diversion was performed in 10 dogs after complete cystectomy. Four dogs were euthanatized on day 30 because of hypochloremic metabolic alkalosis and renal failure. Hematologic and biochemical changes in six dogs evaluated for 120 days were compatible with hypochloremic metabolic alkalosis. The continuous loss of hydrochloric acid from the gastric conduit resulted in significant increases in arterial blood pH, PaCO2, anion gap, TCO2, and the concentration of HCO3-. There were significant decreases in PaO2 and the serum concentrations of chloride and potassium. Deterioration of renal function resulted in all dogs. It was concluded that hypochloremic metabolic alkalosis makes gastric conduit urinary diversion unsatisfactory for clinical use in dogs.

Acid-Base Equilibrium↗
PubMedDate not supplied

Envenomation by the inland taipan, Oxyuranus microlepidotus.

A case of envenomation by a three-week-old inland taipan (Oxyuranus microlepidotus)-the second recorded case of a bite by possibly the most venomous snake in the world - is reported. Evidence which supports the use of the term "inland taipan", and confirms the effectiveness of taipan antivenom in the treatment of bites by this snake, is presented.

Adult↗