Arterialized capillary sampling using histamine iontophoresis

Properties of transdermal histamine iontophoresis: differential effects of season, gender, and body region

Histamine iontophoresis is demonstrated to be a reliable model for the study of inflammatory skin responses. It has the advantage of a non-invasive and uniform mode of application and is free of unwanted side effects. The wheal and flare responses to histamine are linearly related to dose over a wide range of stimulus strengths (r = 0.88). In summer, wheal responses were smaller, probably due to increased thickness of the epidermis. Female subjects generally expressed larger wheal responses than males, presumably due to differences in epidermal thickness and structure. There were significant regional differences in wheal, flare, and laser Doppler recorded flux responses. Ratings of itch sensations also showed clear, but less pronounced, differences of body regions. Significant regional differences of wheal and flare responses existed. Sensory discrimination of different stimulus levels was demonstrated with visual analogue scale ratings.

Comparison of capillary and arterial blood gas measurements in neonates

One hundred and fifty eight paired arterial and capillary blood samples were obtained from 41 sick preterm infants in their first week of life and the pH, and PCO2, and PO2 concentrations were measured. Half of the capillary samples were obtained from unwarmed heels and half from heels warmed to 40 degrees C. A potentially significant discrepancy (arbitrarily defined as 0.05 units for pH. 1 kPa for PCO2, and 3 kPa for PO2) was found in 19 (24%) of cases for pH, in 9 (11%) for PCO2 and in 21 (26%) for PO2. Warming the heel produced no significant improvement in results. We conclude that capillary blood provides satisfactory measurements of pH and PCO2 for all but the most critical purposes, but that the usefulness of capillary PO2 estimations is limited to the exclusion of hypoxia.

Iontophoresis in dermatology. A review

Iontophoresis, the process of increasing the penetration of drugs into surface tissues by the application of an electric current, has been applied to a great many disease conditions over its 200-year history. Although its greatest success has been in the treatment of hyperhidrosis, it is steadily finding new applications. Many aspects of the mechanisms of iontophoresis have yet to be studied before the technic is both fully understood and maximally utilized. In this article we review the literature on iontophoresis as it pertains to dermatology, including the basic principles, engineering aspects.

Multiple factors limit exercise capacity in cystic fibrosis

Exercise testing was performed in 50 patients with cystic fibrosis to determine whether hemodynamic factors limit exercise capacity in the disease. Prior to exercise testing, lung function and blood gas values were measured. Nutritional status was determined by calculating a weight for height (Wt for Ht) ratio for each subject. A progressive exercise test was used to determine maximum work capacity (Wmax). Cardiac output (Q) (indirect Fick method), and stroke volume (SV) were computed during steady-state exercise at 50% Wmax in 21 of 50 patients. Wmax, SV, Q, and lung function results are expressed as per cent predicted. The mean (+/- SD) Wmax was 75 +/- 23%. Multiple regression analysis showed that maximum voluntary ventilation, resting PaO2, and Wt for Ht accounted for 84% of the variance in Wmax. Although some patients had a reduced SV (mean = 96%) during steady-state exercise, all patients achieved a normal cardiac output (mean = 115%). SV correlated with resting PaO2 but not with lung function. We conclude that exercise capacity in cystic fibrosis is influenced by lung function, nutritional status, and resting hypoxemia, but not by cardiac function; the SV limitation noted in some patients may be due to increased pulmonary vascular resistance related to hypoxemia.

The effect of digoxin on exercise capacity and exercising cardiac function in cystic fibrosis

The ability of digoxin to increase exercise capacity and stroke volume (SV) during exercise was evaluated in ten patients with cystic fibrosis (CF) ages 12 to 20 years with moderate to severe degrees of airway obstruction but no history of heart failure. A double-blind crossover trial of digoxin versus placebo was carried out. An evaluation of exercise performance was undertaken upon entry into the study, and after each of the one-week periods in which digoxin 0.25 mg/day or placebo was taken. Exercise testing consisted of a progressive exercise test on a cycle ergometer to measure maximum work capacity (Wmax) and a steady state test at 2/3 of the baseline Wmax. During the steady state test, the oxygen consumption and carbon dioxide production were measured and cardiac output (Q) was calculated by the indirect Fick (CO2) method. From Q and heart rate (HR), SV was derived. After digoxin, Wmax was unchanged. On steady state exercise HR was unchanged, but there was a slight but significant fall in Q due to a fall in SV. The decrease in SV was associated with exercising hypoxemia. We conclude that digoxin did not increase exercise capacity or improve exercising cardiac function in patients with moderate to severe airway obstruction due to CF.

The management of respiratory failure in infancy

The management of respiratory failure in infancy has altered considerably over the past two decades, due both to an increasing understanding of the underlying pathophysiological mechanisms involved and the development of new techniques of treatment. This paper outlines the rationale, indications, and details of the therapy which may be required in neonates and infants suffering from illnesses affecting respiratory function.