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Biomedical subjects

R N Davidson

Publications and source records attributed to R N Davidson.

At least 73 records · Page 4Linked to original sources
PubMed1986

Within-breath changes of airway calibre in patients with airflow obstruction by continuous measurement of respiratory impedance.

We bench-tested a commercially available instrument for measuring respiratory impedance (Siregnost FD5: Siemens) and found that resistance (R) and phase changes were accurately recorded in models. In a single human subject, total respiratory resistance (R(l)) was closely comparable to resistance measured by the Mead-Whittenberger technique. The derived continuous variable (R(os)) was similar to R at less than 4 cmH2O . litres-1 . sec, but underestimated R at higher values. Ros was highly correlated with airways resistance by body plethysmography (R(aw)), but with a low slope and high intercept (R(os) = 1.38 + 0.59 R(aw): r = 0.89). Because of turbulence, both in model larynxes and in normal subjects, R(os) tends to rise with increases in flow in either direction. R(os) also tends to fall as lung volume rises, and vice versa, reflecting cyclic changes in airway calibre. We devised indices of expiratory narrowing of airways from the maximum flow-volume loop, and the plethysmographic alveolar pressure-flow loop, and compared them with the slope of the relation between R(os) and lung volume during tidal breathing, in nine normal subjects and 16 patients with airflow obstruction. Twelve of the 16 patients, all with abnormal flow-volume loops, had high R(os)-volume slopes, demonstrating excessive expiratory narrowing even during tidal breathing. We found no patients with normal inspiratory R(os) together with an abnormal R(os)-volume slope. Thus unstressed inspiratory calibre was never dissociated from airways narrowing on expiration.

Adult↗
PubMed1986

Lung function and within-breath changes in resistance in patients who have had a laryngectomy.

We describe the construction of a simple device which may be used to connect a patient with a tracheostomy to standard lung function testing equipment. We compared the lung function of nine patients after laryngectomy with nine patients matched for similar degrees of airflow obstruction, and found that peak flow rate (as per cent predicted) was significantly lower than predicted FEV1 in the patients with tracheostomy. This suggests that the larynx may normally affect production of peak flow. We then compared the change in resistance over the normal tidal volume in the two groups, finding no significant difference, and obtained similar results from paired studies in two patients before and after laryngectomy. We conclude that, while the laryngeal aperture varies during tidal breathing, it plays no major part in the overall resistance changes which occur during a normal breath.

Adult↗
PubMed1985

The effect of intravenous sodium cromoglycate on the bronchoconstriction induced by sulphur dioxide inhalation in man.

Ten healthy subjects received, on separate occasions, intravenous infusions of 0.9% NaCl solution (saline) and of sodium cromoglycate given in a double-blind cross-over fashion. After 20 min of infusion the specific airway conductance (sGaw) of each subject was measured in a body plethysmograph. The subject then breathed first a low (1-20 p.p.m.) and then a higher (4-40 p.p.m.) concentration of sulphur dioxide (SO2) for 2 min while the infusion continued. Measurements of sGaw were repeated after each inhalation of SO2. Sodium cromoglycate infusion did not affect the sGaw measured before challenge with SO2. During the infusion of sodium cromoglycate, the falls in sGaw in response to both concentrations of SO2 were significantly less than those which occurred during saline infusion. Plasma concentrations of sodium cromoglycate were found to be 209 +/- 22 nmol/l at the end of the drug infusion. This is about one-hundredth of lowest dose required to stabilize mast cells in vitro. We conclude that sodium cromoglycate acted by a mechanism which did not involve mast cells. Other possible modes of action are discussed.

Adult↗
PubMed1978

Community paediatrics in Cap Bon, Tunisia.

The author spent an undergraduate elective period in Tunisia, and some of the features of a community health scheme in rural Cap Bon are described, such as the use of auxiliaries and standardized techniques.

Child↗
PubMedDate not supplied

Schistosomal periportal fibrosis in Zimbabwe: use of ultrasound in patients with oesophageal varices.

Ultrasound (U/S) imaging of liver was used in a prospective study of 62 consecutive patients with oesophageal varices in the central hospitals in Harare; 50 had haematemesis. U/S changes of Symmers's periportal fibrosis (PPF) were graded from mild (grade 1) to gross (grade 4). 46 patients (74%) had U/S features of PPF: 7 were grade 1, 7 grade 2, 29 grade 3, and 3 grade 4. Patients with PPF were more likely to have bled (P less than 0.05) and were less likely to have ascites (P less than 0.05) than those without PPF. Spleen or liver size or grade of varices did not correlate with the U/S grade of PPF. Rectal snips were positive for schistosome ova in 19 of 28 cases with PPF and 2 of 7 cases without PPF. Patients with PPF were more likely than those without PPF (P less than 0.005) or controls (P less than 0.0001) to have spent their childhood in an area of Zimbabwe with a high prevalence of Schistosoma mansoni. Schistosomal PPF appears to be a common cause of portal hypertension in Zimbabwe. It is strongly associated with childhood spent in areas of high S. mansoni prevalence.

Adult↗
PubMedDate not supplied

Aminosidine (paromomycin) in the treatment of leishmaniasis imported into the United Kingdom.

We report 11 patients with leishmaniasis from different endemic areas, treated in the UK with intravenous aminosidine alone or in combination with other drugs. Clinical and parasitological cures were achieved in all 7 patients from the Mediterranean zone who had visceral disease, with one relapse. Two of 4 patients with cutaneous or mucosal disease were cured; the other 2, from Iraq and Iran, did not respond. Toxic effects were high-tone deafness in 2 patients, one of whom had pre-existing renal impairment, and transient, mild elevation of serum creatinine in 3. Aminosidine is an effective, tolerable and relatively non-toxic alternative to existing antileishmanial drugs for the treatment of visceral leishmaniasis. Further studies will be needed to assess its place in cutaneous and mucosal disease.

Adolescent↗
PubMedDate not supplied

A topical nitric oxide-generating therapy for cutaneous leishmaniasis.

Nitric oxide (NO) synthesized by macrophages is cidal to Leishmania. Since NO diffuses into tissues, we reasoned that NO-generating creams applied topically to lesions might be an effective and inexpensive treatment for cutaneous leishmaniasis (CL). NO was generated non-enzymatically by the acidification of nitrite (KNO2) by ascorbic acid (ASC) or salicylic acid (SAL). Experiments in vitro showed that the combinations of KNO2 and SAL, ASC, or KC1 all killed promastigotes and amastigotes of L. major in a dose- and time-dependent manner, but were toxic to macrophages at higher concentrations. Experiments in vivo showed modest efficacy of the combinations applied topically to L. major CL lesions of BALB/c mice. Forty patients with parasitologically proven L. tropica CL from Aleppo, Syria, were treated for 4 weeks with KNO2 in aqueous cream combined with KC1, ASC, or SAL. Only 11 (28%) of 40 patients showed improvement and only 5 (12%) of 40 were cured at 2 months. Further development of NO-generating creams is warranted.

Administration, Topical↗
PubMedDate not supplied

Childhood tuberculosis--problems ahead.

Childhood tuberculosis (TB) is on the increase, both in developing countries and in the UK. Children cannot usually be diagnosed as having TB by sputum microscopy and culture alone, so millions of children are destined to die of undiagnosed TB in poor countries. Drug resistance is likely to affect a greater proportion of TB cases in children, because they have been recently infected by adults. Whilst BCG vaccination can protect against miliary TB and TB meningitis, it will not interrupt the chain of transmission. HIV co-infected mothers are capable of passing congenital TB to their children.

Antitubercular Agents↗
PubMedDate not supplied

Ethiopian visceral leishmaniasis: generic and proprietary sodium stibogluconate are equivalent; HIV co-infected patients have a poor outcome.

We evaluated generic sodium stibogluconate (SSG) (International Dispensary Association, Amsterdam) versus Pentostam (sodium stibogluconate, GlaxoWellcome, London) under field conditions in Ethiopian patients with visceral leishmaniasis (VL; kala-azar). The 199 patients were randomly assigned to Pentostam (n = 104) or SSG (n = 95) in 1998/99; both drugs were given at 20 mg/kg intra-muscularly for 30 days. A clinical cure after 30-days treatment was achieved in 70.2% (Pentostam) and 81.1% (SSG). There were no significant differences between the 2 drugs for the following parameters: frequency of intercurrent events (vomiting, diarrhoea, bleeding or pneumonia) or main outcome (death during treatment and death after 6-month follow-up; relapse or post kala-azar dermal leishmaniasis at 6-months follow-up). Twenty-seven patients had confirmed co-infection with HIV. On admission, HIV co-infected VL patients were clinically indistinguishable from HIV-negative VL patients. The HIV co-infected VL patients had a higher mortality during treatment (33.3% vs 3.6%). At 6-month follow-up, HIV-positive patients had a higher relapse rate (16.7% vs 1.2%), a higher death rate during the follow-up period (14.3% vs 2.4%), and more frequent moderate or severe post kala-azar dermal leishmaniasis (27.3% vs 13.3%). Only 43.5% of the HIV-positive patients were considered cured at 6-months follow-up vs 92.1% of the HIV-negative patients. HIV-positive patients relapsing with VL could become a reservoir of antimonial-resistant Leishmania donovani.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Emergence or re-emergence of visceral leishmaniasis in areas of Somalia, north-eastern Kenya, and south-eastern Ethiopia in 2000-01.

Visceral leishmaniasis (VL) was known to be endemic in Somalia along the basins of the (Middle) Shebelle and (Lower) Juba rivers, and in Kenya in parts of the Rift Valley, on the border with Uganda and the Eastern Provinces. From May 2000 to August 2001, we diagnosed 904 patients with VL. The patients came from an area which spanned the Wajir and Mandera districts of north-eastern Kenya, southern Somalia, and south-eastern Ethiopia. Small numbers of patients were also seen in northern Somalia. These areas were either previously non-endemic for VL, or had only sporadic cases prior to the epidemic. We describe the features of the outbreak and review the history of VL in the region. Unusual rainfall patterns, malnutrition, and migration of a Leishmania-infected population seeking food and security may have contributed to this outbreak.

Adolescent↗