Biomedical subjects

M D Peake

Publications and source records attributed to M D Peake.

41 records · Page 3Linked to original sources

PubMed1981

Steady-state vascular responses to graded hypoxia in isolated lungs of five species.

In the isolated pig lung exposed to graded levels of hypoxia, steady-state pulmonary vasomotor tone is maximum at an O2 tension (PO2) of 50 Torr. Below 50-Torr decreases in PO2 cause steady-state tone to fall below this maximum. To determine whether this stimulus-response relation was peculiar to pigs, we measured the steady-state relation between PO2 and vasomotor tone in the isolated lungs of dogs, rabbits, cats, and ferrets, by using identical techniques in each species. Marked species differences were apparent in both the level of PO2 required to elicit responses and the amplitude of the responses. The ferret and the pig had the largest vasoconstrictor responses to hypoxia. No significant responses were obtained in the dog. The cat and rabbit were intermediate responders. In the ferret, cat, and rabbit, the stimulus-response relationship was biphasic, as in the pig. On the average, maximal constriction occurred at an PO2 of 25 Torr. When PO2 was lowered below 25 Torr, steady-state tone fell. Thus pulmonary vasodilation at low PO2 occurs in the isolated lungs of several species.

Animals↗

PubMed1980

Vasodilator and constrictor responses to hypoxia in isolated pig lungs.

We examined transient and steady-state responses of the pulmonary circulation to hypoxia in isolated pig lungs perfused with autologous blood. Responses were quantified by the pulmonary artery pressure at a flow of 1 l/min (Ppa1) read directly from pressure-flow recordings. Alveolar carbon dioxide tension was constant at 38 Torr and alveolar oxygen pressure (PAO2) was varied between 670 and 0 Torr. When PAO2 was lowered progressively every 10 min, the relation between PAO2 and Ppa1 was sigmoidal, with maximum constriction occurring at a PAO2 of 0 Torr; however, if Ppa1 was allowed to reach a steady state at each level of PAO2, the relation was reproducibly and reversibly biphasic. Ppa1 increased as PAO2 decreased from 670 to 60 Torr, was maximum and stable at PAO2 between 60 and 30 Torr, and decreased as PAO2 was lowered from 30 to 0 Torr. As a result, steady-state Ppa1 at PAO2 greater than or equal to 200 Torr was similar to that at PAO2 = 0 Torr. When PAO2 was changed from 200 Torr to a constant lower level, Ppa1 required 20-30 min to achieve a steady state at PAO2 greater than or equal to 25 Torr and 40-50 min at PAO2 of 10 and 0 Torr. With the latter, the responses consisted of vasoconstriction followed by marked vasodilation. Thus pulmonary vasomotor tone was a complex function of both PAO2 and time. Attempts to explain the pulmonary vascular response to hypoxia must take these complexities into account.

Animals↗

PubMed1979

Hypoxaemia in chronic obstructive bronchitis.

Arterial blood gas tensions were studied for six years in 85 patients (59 men, 26 women, mean age 58.8 years) with hypoxaemia associated with chronic bronchitis. All patients who died had a precipitous fall of arterial oxygen tension (PaO2) breathing air. In patients dying within two years of the first appearance of ankle oedema the mean rate of fall of PaO2 was 0.11 kPa/month. Patients who survived two years appeared to deteriorate more slowly (0.017 kPa/month) until some months before death, when they too deteriorated rapidly. Hypoxaemic patients with obstructive airways disease suffer a terminal rapid decline in arterial oxygen tension, which probably indicates real pathological change in the lungs and has important implications for long-term domiciliary oxygen treatment.

Aged↗

PubMed1979

Triamcinolone in corticosteroid-resistant asthma.

In an uncontrolled study 38 patients with chronic asthma were treated for up to 4.5 years (mean 2.9) with depot injections of triamcinolone acetonide. About half had proved difficult to control on large doses of corticosteroid tablets. Three-quarters were helped and the incidence of hospital admission amongst them was reduced. Side effects were tolerable and adrenal function was only moderately depressed. Spirometry showed continuing improvement up to three years after starting triamcinolone. Whether similar improvement could have been achieved by a different dosage regimen of corticosteroid tablets or whether it might have ocurred spontaneously was not tested. A controlled trial seems warranted.

Adult↗

PubMedDate not supplied

Controlled release salbutamol tablets versus aminophylline in the control of reversible airways obstruction.

A crossover study was carried out to compare the acceptability and efficacy of 8 mg twice daily controlled release salbutamol with 525 or 700 mg twice daily aminophylline in patients with reversible obstructive airways disease. Patients were randomly allocated into two groups to determine the treatment order. A 2-week run-in period was used to titrate the aminophylline dosage, followed by a crossover phase of two 4-week treatments. A total of 68 patients, aged 20-75 years, entered the study and 39 (57%) completed it. The two drugs differed in the pattern and severity of their side-effects. Of the 15 patients withdrawn because of severe adverse events, 12 were unable to tolerate treatment with aminophylline. There were no statistically significant differences between the treatments for lung function tests measured at the clinic, peak expiratory flow rate recorded by the patients, frequency (or severity) of asthma symptoms or the use of relief medication. Patients completing the study expressed a preference for controlled release salbutamol in 17/25 (68%) cases.

Albuterol↗