Biomedical subjects

T H Rossing

Publications and source records attributed to T H Rossing.

43 records · Page 3Linked to original sources

PubMed1982

CO2 elimination by high-frequency oscillations in dogs--effects of histamine infusion.

Effective gas exchange can be achieved in normal dogs by ventilation at frequencies of 4-20 Hz using stroke volumes (SV) smaller than the anatomic dead space. CO2 elimination is largely a function of tracheal SV-frequency product (Vosc) in anesthetized, paralyzed dogs with normal lungs. To determine the effect of constriction of small airways on gas exchange during such high-frequency ventilation (HFV), we ventilated five anesthetized, paralyzed, and vagotomized dogs via a tracheal cannula before and during intravenous histamine infusion. Vosc was varied by varying the frequency while keeping SV constant. For low Vosc, CO2 elimination (VCO2) increased directly with Vosc during control and histamine experiments. At high Vosc, VCO2 continued to increase directly with Vosc during the control study, but during histamine infusion VCO2 was lower than control values. Eucapnia could be maintained in each dog during HFV, even during airway constriction. During histamine infusion the frequency-dependent mechanical properties of the lung influence the delivery of the HFV SV to the respiratory zone, and this may explain the lower VCO2 observed.

Animals↗

PubMed1982

Survival in lung cancer. An analysis of the effects of age, sex, resectability, and histopathologic type.

Records of 6,686 patients with primary lung malignancies were retrieved from a tumor registry. Survival curves according to histopathologic type demonstrated that patients with anaplastic tumors have a lower cumulative survival than those with either squamous cell cancers or adenocarcinomas (p less than 0.001), but survival for the latter two histologic types is similar. Age at diagnosis influences survival, and women with squamous or anaplastic tumors have a better prognosis than men with the same cell types (p less than 0.001). Although selection for resection is strongly associated with lower early mortality, all patients alive 2 yr after diagnosis have a similar prognosis is regardless of initial resectability. Each survival curve shows a high early mortality and a lower late mortality, indicating that each group can be considered to consist of 2 subgroups with different risks of dying of lung cancer. A mathematical model is described that closely approximates the actuarial survival.

Adenocarcinoma↗

PubMed1981

Tidal volume and frequency dependence of carbon dioxide elimination by high-frequency ventilation.

Six patients with chronic respiratory failure received mechanical ventilation with tidal volumes less than or equal to the dead-space volume, at frequencies of 30 to 900 breaths per minute. The rate of elimination of carbon dioxide from the ventilator system during a brief trial of high-frequency ventilation accurately predicted the long-term effectiveness of a given combination of frequency and tidal volume. Below frequencies of about 200 breaths per minute, the volume of carbon dioxide eliminated from these patients was most strongly related to the product of frequency and tidal volume; at higher frequencies, carbon dioxide elimination was determined by the tidal volume and was independent of frequency. These results suggest that although the effectiveness of high-frequency ventilation is primarily a function of the product of tidal volume and frequency, above a critical frequency the mechanical characteristics of the lung reduce gas transport by limiting the volume transmitted to the periphery of the lung.

Adolescent↗

PubMed1981

A controlled trial of the use of single versus combined-drug therapy in the treatment of acute episodes of asthma.

Eighty-nine patients who presented to the hospital for treatment of acute episodes of asthma were randomly assigned to initial therapy with subcutaneously administered epinephrine or 1 of 2 combination regimens consisting of intravenously administered aminophylline and either subcutaneously administered of epinephrine or inhaled isoproterenol. During the first hour of treatment, as a group, the patients treated with the 2-drug regimens showed greater objective improvement than did patients who received epinephrine alone. This was particularly true for patients with either severe airway obstruction or a subtherapeutic theophylline concentration at the time of presentation. There were no differences in the heart rate and blood pressure responses to the 3 regimens, and symptoms consistent with drug side effects were not reported more frequently by patients treated with 2 drugs. Thus, the combination of sympathomimetics and aminophylline appear more effective, and no more toxic, than epinephrine alone for the initial treatment of acute episodes of asthma.

Acute Disease↗

PubMed1981

Effects of frequency, tidal volume, and lung volume on CO2 elimination in dogs by high frequency (2-30 Hz), low tidal volume ventilation.

Recent studies have shown that effective pulmonary ventilation is possible with tidal volumes (VT) less than the anatomic dead-space if the oscillatory frequency (f) is sufficiently large. We systematically studied the effect on pulmonary CO2 elimination (VCO2) of varying f (2-30 Hz) and VT (1-7 ml/kg) as well as lung volume (VL) in 13 anesthetized, paralyzed dogs in order to examine the contribution of those variables that are thought to be important in determining gas exchange by high frequency ventilation. All experiments were performed when the alveolar PCO2 was 40 +/- 1.5 mm Hg. In all studies, VCO2 increased monotonically with f at constant VT. We quantitated the effects of f and VT on VCO2 by using the dimensionless equation VCO2/VOSC = a(VT/VTo)b(f/fo)c where: VOSC = f X VT, VTo = mean VT, fo = mean f and a, b, c, are constants obtained by multiple regression. The mean values of a, b, and c for all dogs were 2.12 X 10(-3), 0.49, and 0.08, respectively. The most important variable in determining VCO2 was VOSC; however, there was considerable variability among dogs in the independent effect of VT and f on VCO2, with a doubling of VT at a constant VOSC causing changes in VCO2 ranging from -13 to +110% (mean = +35%). Increasing VL from functional residual capacity (FRC) to the lung volume at an airway opening minus body surface pressure of 25 cm H2O had no significant effect on VCO2.

Animals↗

PubMed1980

Emergency therapy of asthma: comparison of the acute effects of parenteral and inhaled sympathomimetics and infused aminophylline.

Forty-eight patients who presented with acute episodes of asthma were randomized to treatment with subcutaneously administered epinephrine, inhaled isoproterenol, or intravenously administered aminophylline. The patients' couses were followed clinically and with spirometry. Although there were no significant differences between the groups before treatment for any measured variable, at the end of 1 hour, the mean improvement inforced expiratory volume in one second (FEV1) was significantly greater for patients treated with epinephrine (0.76 L) or nebulized isoproterenol (0.79 L) than for those given aminophylline (0.23 L). Similarly, the mean duration of therapy required before discharge from the emergency room was significantly longer for patients receiving aminophylline (5.4 h) than for patients treated with either epinephrine (3.5 h) or isisoproeternol (3.0 h). There was no significant differences between the effects of the 2 beta agonists. These results demonstrated that short-acting sympathomimtic agents produce more rapid and potent bronchodilatation in acutely ill asthmatics than that provided by intravenously administered methylxanthines, and that there are no disadvantages to using an inhaled beta agonist rather than one administered parenterally.

Administration, Intranasal↗

PubMedDate not supplied

Diphtheria immunity in Massachusetts--a study of three urban patient populations.

To determine the status of diphtheria immunity among our patients, we measured diphtheria antitoxin levels in three separate patient populations. The technique used was toxin neutralization in rabbit skin, which allowed us to evaluate the immune status of individual patients. We studied an emergency room population, a sampling of inpatients from an urban teaching hospital, and a group of older patients from a chronic care hospital. Overall, approximately 80% of patients had adequate diphtheria antitoxin levels in their serum. However, two subgroups emerged with lower levels, with potential nonimmunity. These were certain young patients, either foreign born or with a potentially "immunocompromising disorder," and the elderly chronically ill. We conclude that while overall diphtheria immunity in our patients appears adequate, subgroups with increased risks do exist and immunization for these subgroups should be undertaken.

Adolescent↗