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Biomedical subjects

L H Hamilton

Publications and source records attributed to L H Hamilton.

At least 37 records · Page 2Linked to original sources
PubMed1979

Alterations in pulmonary function consequent to competitive marathon running.

This study was designed to investigate the mechanisms underlying the significant reductions in vital capacity after marathon racing originally reported over 50 years ago. Spirometric, maximum expiratory flow-volume (MEFV), DLCO and residual volume (RV) measurements were made on 13 runners (11 males and 2 females) 1--2 weeks prior to the marathon, immediately after finishing the race, and again the next day. An average 0.48 L (8.6%) reduction in post-race forced vital capacity (FVC) was accompanied by an equivalent increase in RV. Thus, total lung capacity did not change, and the reduction in FVC was a result of an expiratory rather than an inspiratory limitation. Post-race FEV1 and FEF200-1200 remained unchanged while FEV1-2, FEF1 and FEF2 were reduced 19.7, 26.7 and 23.3%, respectively. Mean DLCO was unchanged. Pulmonary function on the following day was similar to that observed on the control day. These data indicated that after the race, expiratory flow was unaffected at high lung volumes, but was decreased at low lung volumes (within the effort-independent portion of the MEFV curve). The results are compatible with small airway closure occurring at an increased lung volume, which would result in a decreased FVC and an increased RV.

Adult↗
PubMed1977

Nasal airway resistance computer.

An analogue computing system for the measurement of nasal airway resistance (Rn) has been developed. The instrument operates on the principle of measuring the transnasal pressure required to generate a measured nasal airflow rate. The system computes and displays inspiratory or expiratory nasal airway resistance measured at a preselected flow rate. The values are updated on a breath-by-breath basis and presented to a multi-channel recorder and a digital panel meter for visualization. The continuous Rn (at all inspiratory and expiratory flow rates above zero) can also be recorded. Use of the instrument for the evaluation of nasal decongestants has been demonstrated.

Airway Resistance↗
PubMed1977

Acoustic helium analyzer for closing volume measurement.

An acoustic gas analyzer was developed to measure helium during the closing volume (CV) test. It is based on the principle that altering the composition of a gas mixture will change the velocity at which sound is transmitted through the gas. The change in transit time for an acoustic burst across an in-line (breathe-through) cell is measured as a function of He concentration in the expired air during the CV test. Although CO2 and H2O vapor affect the signal, so it is not specific for He, the system provides good records of CV. A comparison of measurements in 21 normal subjects demonstrated no differences for CV measured in the same breath by the bolus technique using the acoustic gas analyzer and by the resident gas method using a nitrogen analyzer. Differences in closing volumes measured by the He bolus technique and the resident gas method might exist in patients with some kinds of pulmonary disease, and the suggestion is made that CV measurements by the two methods might assist in describing pulmonary alterations in patients with bronchopulmonary disease.

Closing Volume↗
PubMed1977

Application of a simple gas chromatographic technique for measuring breath hydrogen.

A simple gas chromatographic technique for analyzing H2 in expired air with a compact, relatively inexpensive gas chromatography specifically adapted for H2 analysis is described. Modifications in the basic chromatograph included increasing the capacity of the sample loop, lengthening the column, and using argon as the carrier gas to increase the sensitivity of the system. Methods for collecting and storing respiratory gas samples and for quantifying the results are described for clinical studies of carbohydrate malabsorption. Small errors in collection and quantitation are introduced by the method, but they are minor in relation to the changes in H2 concentration which are seen with significant malabsorption. This simplification of chromatograph technology could increase the general availability of this convenient, noninvasive and well-tolerated test of intestinal absorption of carbohydrates such as lactose.

Adult↗
PubMed1976

Metabolic changes in exercise-induced and methacholine-induced bronchoconstriction.

Metabolic and physiological responses to graded exercise and methacholine challenge were investigated in asthmatics with or without exercise-induced bronchoconstriction. The results showed that after methacholine challenge, free fatty acid levels increased only in patients with exercise-induced asthma, while they increased in both groups of asthmatics after treadmill exercise. No significant changes were noted in plasma lactic acid levels, ventilation, or oxygen consumption among the groups studied. These data suggest that asthmatics with exercise-induced bronchoconstriction may differ from other asthmatics in some of their metabolic responses.

Adolescent↗
PubMed1976

A study of a new bronchodilator: carbuterol.

A new oral bronchodilator, carbuterol, was studied in 9 subjects who had reversible airway obstruction. In addition to the spirometric changes, serial arterial blood gas determinations were done to see if the drug induced hypoxemia. Two- and 4-mg doses were compared with the placebo. There was a significant bronchodilating effect with the 4-mg dose beginning 30 min after administration of the drug. Maximal improvement of forced expiratory volume in 1 sec was observed at 4 hours, with a 42 per cent increase from the baseline. No significant hypoxemia was observed. The drug was considered an effective bronchodilating agent, with the effect lasting longer than 4 hours.

Adult↗
PubMed1975

Ability of single-breath nitrogen closing volume to detect early airway obstruction.

In order to determine the ability of single-breath nitrogen closing volume (CV) to detect early airway obstruction, the CV was measured in patients with either minimal obstruction of spirometry or with increased residual volume (RV). A total of 39 subjects was included in this study. The mean CV was largest in patients who had reduced maximum mid-expiratory flow rates (MMF). There was no difference in mean CV between smokers and the patients who had large RV but no airway obstruction, although both groups had higher mean CV than ex-smokers. Normal CV was seen in four of 11 patients who had reduced MMF and in four of seven who had large RV but no airway obstruction. All ex-smokers had normal CV while five of 12 smokers had adnormal CV. The results indicate that the closing volume should be used to complement spirometry, rather than to replace it, for screening of early airway obstruction.

Adult↗
PubMed1975

Effects of hypoxia and histamine infusion on lung blood volume.

Using an isolated perfused cat lung preparation we examined the effects of hypoxia and histamine infusion on the lung blood volume. Total lung blood volume was determined from the indocyanine green transit time and the ether bolus technique was used to estimate arterial and venous volumes during forward and retrograde perfusion, respectively. Changes in lung total fluid content were determined from changes in the blood volume of the perfusion system. Hypoxia increased perfusion pressure and decreased total fluid and blood volume. Histamine infusion also increased perfusion pressure and decreased blood volume. However, histamine increased total fluid volume, indicating an increase in vascular permeability. Hypoxia decreased arterial and venous volumes, and histamine decreased venous volume. The slopes of the arterial and venous volume/pressure curves were not altered by hypoxia or histamine.

Animals↗