Biomedical subjects

R B Light

Publications and source records attributed to R B Light.

45 records · Page 3Linked to original sources

PubMed1983

The physiology of recovery in experimental pneumococcal pneumonia.

Lobar distribution of pulmonary perfusion, arterial PO2 (PaO2), intrapulmonary shunt (Qs/Qt) and post mortem lobe wts were measured in 12 dogs with experimental lobar pneumococcal pneumonia. Six dogs (group I) had both perfusion and gas exchange measurements performed 48 h after an inoculum of Streptococcus pneumoniae was placed in a left lower lobe bronchus. Six other dogs (group II) had perfusion determinations before the induction of pneumonia and again 96 h after inoculation, at which time gas exchange measurements were performed. To ensure that group II dogs were recovering from the acute pneumonia, penicillin treatment was instituted at 48 h and continued until the time of study at 96 h. An improvement in gas exchange between the acute and convalescent states was demonstrated and was associated with a 50% reduction in excess wet wt and a 25% reduction in perfusion of the infected lower lobe. We conclude that improvement in gas exchange during recovery from acute lobar pneumonia is due, in part, to air space clearing with improved ventilation and, in part, to reduced perfusion of poorly ventilated lung. The results suggest that arterial hypoxemia in acute pneumonia is aggravated by vasodilatation or blockade of local hypoxic vasoconstriction by some aspect of the acute inflammatory response, and that the hypoxic vasoconstrictor response is restored during convalescence.

Acute Disease↗

PubMed1982

Plasma volume expansion in canine pneumococcal pneumonia: its effects on respiratory gas exchange and pneumonia size.

Patients with pneumococcal pneumonia are often given fluids intravenously for hydration and maintenance of circulating blood volume. We studied the effects of plasma volume expansion on respiratory gas exchange and pneumonia size in a canine model of lobar pneumonia. Seven ventilated anesthetized dogs (Group T) with left lower lobe pneumococcal pneumonia were infused with dextran 75 in 0.9% saline solution to increase the pulmonary capillary wedge pressure to 10 mmHg for 3 h. These were compared with 7 control dogs (Group C) with left lower lobe pneumonia. Measurements of cardiac output, intrapulmonary shunt (QS/QT), and lobar distribution of perfusion were taken at baseline (B), immediately after volume infusion (V), and 3 h later (F); similar intervals were used in control animals. In Group T, QS/QT increased significantly from 24% at B to 34% at F. Part of this increase in QS/QT occurred immediately after volume infusion (29% at V) and was associated with the concomitant increase in cardiac output (4.7 L/min at B to 10.6 L/min at F). In Group C, there were no changes in cardiac output or QS/QT. At autopsy, mean wet weight for both lower lobes in Group T were greater than in Group C. Accordingly, small elevations in pulmonary capillary wedge pressure associated with fluid administration caused large increases in lobar wet weights. At least in part, these increases represented transudation of plasma and crystalloid into alveolar spaces and suggested large increases in extravascular lung liquid flux from inflamed vessels in infected lung.

Animals↗

PubMed1981

Trimethoprim alone in the treatment and prophylaxis of urinary tract infection.

Trimethoprim was used alone to treat urinary tract infections in 20 women who were unable to tolerate sulfonamides. Of ten acute symptomatic urinary tract infections, four were cured, three were not, and three cases could not be evaluated. Two other women received trimethoprim for suppression of infection complicating stag-horn calculi. The conditions of both patients improved clinically but the urine remained infected. Eight women treated prophylactically with low-dose trimethoprim for recurrent urinary tract infection accumulated a total of 16 patient-years of prophylaxis. During treatment, the incidence of infection was 0.56 per patient-year compared with 4.25 infections in the year preceding study. Adverse reactions occurred in eight of 20 patients and administration of the drug had to be stopped in five cases. Trimethoprim alone is effective for the treatment and prophylaxis of urinary tract infections, but may cause a high incidence of adverse reactions in patients known to be sensitive to sulfonamides.

Adult↗

PubMed1981

The effect of unilateral PEEP on gas exchange and pulmonary perfusion in canine lobar pneumonia.

Positive end-expiratory pressure (PEEP) has little beneficial effect in improving gas exchange in canine left lower lobe (LLL) pneumonia. This is true because while PEEP improves lobar gas exchange, it also increases relative perfusion (QL) to the diseased lobe. The authors hypothesized that PEEP administered to only the diseased lung would avoid the increased QLLL. Six dogs with LLL pneumonia in which PEEP was applied only to the left lung were observed. The dogs were studied supine and each lung was ventilated separately with 100 per cent O2. Measurements of arterial oxygen tension (PaO2), shunt (Qs/Qt) and lobar distribution of pulmonary perfusion were made before, during, and after 12 cm H2O PEEP. Changes in QLLL expressed as per cent of cardiac output were determined using radiolabeled microspheres. PEEP improved PaO2 from 310 +/- 86 to 532 +/- 58 torr and Qs/Qt from 29 +/- 5 per cent to 12 +/- 5 per cent, returning after PEEP to 337 +/- 84 torr and 26 +/- 5 per cent, respectively. QLLL per cent did not increase during PEEP. These results suggest that unilateral PEEP improves regional gas exchange within the pneumonia lobe, probably by ventilating units which were previously perfused but not ventilated. Further, this improvement in regional gas exchange occurred without the diversion of blood flow towards consolidated lung that occurs with whole-lung PEEP, and so resulted in a substantial net improvement in overall gas exchange.

Animals↗

PubMed1981

Effect of pneumococcal lobar pneumonia on canine lung mechanics.

We produced left lower lobe (LLL) pneumococcal pneumonia in seven dogs and measured lung volumes and pulmonary mechanics before (day 1) and 48 h after (day 3) development of the infection. Compared with seven control dogs, total lung capacity (TLC) and functional residual capacity (FRC) decreased 550 and 140 ml, respectively, representing a 15% reduction from the initial value in both cases. Compliance measured during tidal breathing decreased by 30%, and even when corrected for the smaller FRC on day 3, specific compliance (CLsp) was reduced. At autopsy, the infected LLL had an excess weight of 89 g, and its 50% reduction in gas volume accounted for the decrease in TLC from day 1 to day 3. Compared with control dogs, there were no changes in the deflation pressure-volume curves of the noninfected lung of the pneumonia dogs. These results indicate that the reduction in TLC in bacterial lobar pneumonia was small and resulted from the reduced gas volume of the infected lobe. Assuming that the increased weight gain in the LLL represented 89 ml of exudate that filled alveoli, we propose that bacterial pneumonia reduced gas volume at FRC by filling alveoli with inflammatory exudate and further decreased TLC by preventing these alveoli from inflating. The reduced CLsp suggested nonventilation of air spaces in addition to those that were liquid filled and was consistent with nonventilation of the entire LLL.

Animals↗

PubMed1981

Effect of PEEP on gas exchange and pulmonary perfusion in canine lobar pneumonia.

We investigated the effects of positive end-expiratory pressure (PEEP) on respiratory gas exchange and pulmonary perfusion in 10 dogs with left lower lobe (LLL) pneumonia. In 6 dogs, measurements were made with the chest closed and 12 cmH2O were applied; in 4 other open-chest dogs (group O), 6 cmH2O were used. Both groups showed similar changes, and the individual results for all dogs were averaged. With the animals breathing 100% oxygen, total pulmonary shunt (Qs/Qt), arterial oxygen tension (PaO2), and the relative distribution of pulmonary blood flow were measured before, during, and after PEEP. During the control periods, QLLL when expressed as a percent cardiac output averaged 24 +/- 7%. With PEEP, QLLL increased by more than 50% to a mean value of 37 +/- 5%. Despite this increase, the respective values of Qs/Qt and PaO2 improved slightly from 28% and 288 Torr to 25% and 370 Torr. This result suggested that PEEP also improved regional gas exchange, and this finding was subsequently confirmed in Group O where the shunt fractions of the lower lobes were additionally measured. Accordingly, our results show that PEEP altered regional perfusion and shunt so that, on the mean, there was little change in total pulmonary shunt. Whether PEEP worsened or improved gas exchange in any individual experiment was dependent on the relative magnitude of the changes in each of these regional parameters.

Animals↗

PubMed1981

Pathophysiology of gas exchange and pulmonary perfusion in pneumococcal lobar pneumonia in dogs.

We placed an inoculum of Streptococcus pneumoniae type III into a left lower lobe bronchus of six dogs (group P), and in six other dogs (Group C) a sterile control inoculum was used. Measurements of shunt (Qs/Qt) and venous admixture (Qva/Qt) were made immediately before (day 1) and 48 h after (day 3) inoculation. All dogs in group P had extensive lobar pneumonia confirmed radiologically and at autopsy, whereas Group C had only small sterile lesions at the site of inoculation. In group P, mean Qs/Qt and Qva/Qt increased significantly to 0.15 and 0.21, respectively. Mean lobar Qs/Qt, calculated using blood samples from lobar veins at thoracotomy on day 3, was markedly increased in the pneumonia lobe (0.69) compared with the contralateral lower lobe (0.08), and alveolar ventilation of that lobe approached zero. Perfusion of the infected lobe determined by radioactive microspheres showed a variable and statistically nonsignificant decrease between control and infected states that was not affected by oxygen breathing. In group C there was no change between days 1 and 3 in gas exchange or in distribution of pulmonary perfusion. We conclude that hypoxemia in pneumonia was due to both increased shunt and venous admixture in the infected regions, and that local hypoxic vasoconstriction was in most instances ineffective in directing blood flow away from the consolidated lobe.

Animals↗

PubMed1981

Epidemiologic features of urinary infections due to enterobacteriaceae resistant to nalidixic acid and trimethoprim.

For a period of one year we identified all urinary isolates of Enterobacteriaceae resistant to either nalidixic acid (NA) or trimethoprim (TMP). Host and organism characteristics associated with the occurrence of 68 NA and 61 TMP-resistant isolates were compared with 61 matched antimicrobial-susceptible controls. Minimum inhibitory concentrations to NA and TMP were carried out on all isolates, Escherichia coli isolates were biotyped and TMP-sulfamethoxazole (SMX) synergy studies were performed on TMP-resistant isolates. Study patients were reviewed with regard to age, renal function, presence of structural urinary tract abnormality, history of antimicrobial treatment and persistence of study strains within the urinary tract. Resistance to both drugs was associated with prior treatment with the relevant antimicrobial and with underlying urinary tract abnormality. No association was noted between resistance and patient age or renal function. Once resistant organisms infected an abnormal urinary tract, they were able to persist almost indefinitely. Patients with persistent urinary infections associated with structural urinary tract abnormality account for most NA or TMP-resistant infections in our hospital and constitute an identifiable group in whom the therapeutic usefulness of these drugs is limited.

Adult↗

PubMed1979

Prophylaxis of recurrent urinary tract infection in female patients. Efficacy of low-dose, thrice-weekly therapy with trimethoprim-sulfamethoxazole.

Thirty-two women with recurrent urinary tract infections were treated after eradication of existing infections with a mixture of 40 mg of trimethoprim and 200 mg of sulfamethoxazole thrice weekly at bedtime for six months. Six preadolescents received one half this dose. During 21.3 cumulative patient-years of prophylaxis, one infection due to Streptococcus faecalis and one due to a sulfamthoxazole-and trimethoprim-sensitive Escherichia coli occurred--an infection incidence of 0.1 per patient-year. During prophylaxis, 61 of 72 periurethral cultures and 24 of 51 anal canal cultures failed to yield Enterobacteriaceae. One patient had transient colonization with a trimethoprim-resistant E coli during prophylaxis. Twenty-one patients had recurrent infection within six months of discontinuation of prophylaxis, with a mean time to recurrence of 2.6 months. One infection recurred 26 weeks following prophylaxis with a Proteus mirabilis. Thrice-weekly trimethoprim-sulfamethoxazole therapy was effective for prophylaxis of recurrent urinary tract infections and did not predispose to colonization or infection with trimethoprim-resistant Enterobacteriaceae.

Adolescent↗