Biomedical subjects

N R MacIntyre

Publications and source records attributed to N R MacIntyre.

64 records · Page 4Linked to original sources

PubMed1985

Aerosol delivery in intubated, mechanically ventilated patients.

To study the effects of respiratory failure and mechanical ventilation on aerosol delivery to the lungs, we performed nuclear scans after aerosolization of 5 to 9 mCi of Tc-99m diethylenetriamine pentaacetic acid in seven stable, intubated, and mechanically ventilated patients. The radioactivity reaching the lungs was 2.9 +/- .7% (mean +/- SD) of the administered dose, an amount significantly less than that in three healthy nonintubated subjects and also less than what would be expected in nonintubated subjects from other published reports. We then performed a subsequent study in 15 additional mechanically ventilated patients who were receiving aerosolized bronchodilators through their endotracheal tube. In these patients, heart rate and lung mechanical function values before and after treatment were not significantly different. We conclude from these studies that aerosol delivery in mechanically ventilated patients is significantly reduced and that this is probably due to a combination of suboptimal breathing pattern, intrinsic airway disease, and the endotracheal tube functioning as both a site for aerosol deposition through impaction as well as a barrier to gastrointestinal absorption.

Aerosols↗

PubMed1984

Prediction of subsequent ischemic heart disease using serial resting electrocardiograms.

To test the hypothesis that subtle changes in the resting electrocardiogram can have predictive value for subsequent cardiovascular disease, the authors evaluated serial electrocardiograms from a cohort of initially healthy men and related these to later development of ischemic heart disease. The cohort of 1056 men originally physically qualified for naval aviation were followed from 24-61 years of age between 1940 and 1977. Resting electrocardiograms were obtained at 24, 36, 42, and 54 years of age. Particular emphasis was directed to measurement of electrocardiographic intervals, amplitudes, and vectorial orientation. The potential effects of weight, blood pressure, and other major risk factors on electrocardiographic changes were controlled in analysis. At younger ages, the amplitude of the T wave in lead 2 and the change in P-R interval were predictive of cardiovascular disease. With aging of the cohort, more leftward orientation of the frontal plane QRS and T forces were predictive, as were the serial changes in the angle between QRS and T. When major risk factors (smoking, blood pressures, and serum cholesterol) were included in a predictive model, addition of electrocardiographic changes significantly improved prediction of ischemic heart disease. These subtle serial changes may be helpful to epidemiologists and clinical investigators in assessing risk of subsequent cardiovascular disease.

Adult↗

PubMed1984

Hemodynamic monitoring in respiratory care.

Continuous, invasive hemodynamic monitoring of patients in respiratory failure is an important aspect of total respiratory care. Understanding both the technical and physiological principles underlying hemodynamic monitoring is therefore important for respiratory care practitioners. This review is designed to meet this need by (1) addressing the technical aspects of hemodynamic monitoring (catheters, transducers, and monitors), (2) discussing the determinants of commonly measured hemodynamic variables (intravascular pressures and cardiac output), and (3) offering an orderly approach to hemodynamic data that allows for rapid determination of the patient's physiologic state and appropriate diagnostic possibilities. These principles are illustrated by five examples.

Hemodynamics↗

PubMed1983

Pulmonary function in mechanically-ventilated patients during 24-hour use of a hygroscopic condensor humidifier.

Hygroscopic condensor humidifiers (HCH) are reportedly capable of humidifying even the driest of ventilator source gases with at least 30 mg H2O/liter of ventilation. To assess the adequacy of the HCH during mechanical ventilation, we studied 26 patients over a 72-hour period (alternating 24-hour periods of humidification by a conventional cascade and the HCH). In these patients, we found no significant difference in static lung compliance, airway resistance, PaO2, and PaCO2 on either system. Additionally, estimates of sputum volume (over a four-hour collection period) and clearance of aerosolized 99mTc labelled DTPA (in five of these patients) also showed no significant differences between the two systems. We conclude that the HCH is capable of supplying necessary heat and moisture to most mechanically-ventilated patients for at least a period of 24 hours.

Adult↗

PubMed1982

Regional diffusing capacity in normal lungs during a slow exhalation.

From an analysis of carbon monoxide uptake and xenon-133 distribution after two bolus inhalations of these gases, we calculated regional diffusing capacity in the upper and lower volume halves of the lungs during the middle 60% of an exhaled vital capacity in five seated normal subjects. We found that the regional diffusing capacity of the upper half of the lungs was 11.6 +/- 4.2 (mean +/- SD) ml.min-1.Torr-1 and that the regional diffusing capacity of the lower half of the lungs was 24.4 +/- 2.4 ml.min-1.Torr-1 after 25% of the vital capacity had been exhaled. These values remained relatively constant as lung volume decreased from 25 to 75% of the exhaled vital capacity. Diffusing capacity in the upper half of the lungs ranged from 9.4 to 12.4 ml.min-1.Torr-1 during exhalation, and in the lower half of the lungs from 21.0 to 28.6 ml.min-1.Torr-1 during exhalation. These results suggest that total lung diffusing capacity remains relatively constant over this midrange of lung volumes and that this occurs because the regional diffusing capacities in both the upper and lower halves of the lungs remain relatively constant.

Adult↗

PubMed1981

Nonlinear increases in diffusing capacity during exercise by seated and supine subjects.

To study the effects of exercise on pulmonary diffusing capacity, we measured the lungs' diffusing capacity for carbon monoxide (DLCO) during exhalation from 30 to 45% exhaled vital capacity in eight healthy subjects at rest and during exercise while both sitting and supine. We found that DLCO at these lung volumes in resting subjects was 26.3 +/- 3.2% (mean +/- SE) higher in the supine than in the sitting position (P less than 0.001). We also found that, in both positions, DLCO at these lung volumes increased significantly (P less than 0.001) with increasing exercise and approached similar values at maximal exercise. The pattern of increase in DLCO with an increase in oxygen consumption in both positions was curvilinear in that the rate of increase in DLCO during mild exercise was greater than the rate of increase in DLCO during heavy exercise (P = 0.02). Furthermore, in the supine position during exercise, it appeared that DLCO reached a physiological maximum.

Adult↗

PubMed1981

Long-term follow-up of lung volume measurements in initially healthy young aviators.

Lung volume measurements on a large number of initially healthy young military aviators (the U.S. Navy's "1000 Aviator" cohort) were recorded periodically in follow-up from 1940-69. Vital capacities were measured spirometrically and total lung capacities were measured planimetrically from chest roentgenograms. Residual volumes were calculated by subtracting the vital capacity from the total lung capacity in each subject. Additional variables available for analysis were cigarette smoking histories, family histories, aviation career patterns, pulmonary symptoms, cardiac disease diagnoses, and anthropometric measurements. Multiple linear regression techniques were used on these variables to construct prediction equations for each lung volume in 1969. From these longitudinal analyses, cigarette smoking and pulmonary symptoms were found to be associated with an "obstructive lung volume pattern in 1969, while coronary artery disease and weight gain were found to be associated with a "restrictive" lung volume pattern in 1969. A career in military aviation had no significant association with lung volumes.

Adult↗

PubMed1981

Eight-year follow-up of exercise electrocardiograms in healthy, middle-aged aviators.

To study to prognostic capabilities of the exercise electrocardiogram (ECG) in a fit, healthy, middle-aged population, 548 members of the U.S. Navy's "1000 Aviator" cohort were exercised to 85% predicted maximum heart rate in 1969 and then followed-up in 1977 for the development of clinically evident coronary artery disease (CAD). Of these subjects, 23 (4.2%) had significant ST depression during their exercise test in 1969. At the end of the 8-year follow-up period, 38 of the 548 subjects (6.9%) had developed clinically evident CAD. The sensitivity (percent of disease predicted by an abnormal test) and predictive value (percent of abnormal tests predictive of disease) of an abnormal exercise test were 15.7% and 26%, respectively. We conclude that even in a carefully screened aviator population with a low risk for CAD, a single normal exercise ECG does not exclude the presence of latent CAD. Furthermore, in this population, a single abnormal exercise ECG should not be a disqualifying defect without further work-up.

Adult↗

PubMed1978

Longevity in military pilots: 37-year followup of the Navy's "1000 aviators".

The 37-year nonmilitary mortality rate for initially healthy aviators was determined in a followup program on the U.S. Navy's "1000 Aviator" cohort. Of the 800 survivors of World War II and the Korean conflict, 95 were found to have died from nonmilitary causes over this followup period. This is markedly less than the 208 that would be expected from a random sample of white American men over a similar period (p less than 0.005). It is also significantly less than the 143 that would have been expected from a group of men who had passed an initial insurance physical (p less than 0.005). Lower-than-expected death rates occurred in all three major categories of cause of death in this age group: cardiovascular, neoplastic, and accidental. The generally good socioeconomic background, the positive genetic influence of long-lived parents, the above average intelligence, and the health and fitness orientation of the military aviator are all thought to be factors contributing to this increased longevity.

Accidents↗

PubMedDate not supplied

Asbestos content of bronchoalveolar lavage fluid. A comparison of light and scanning electron microscopic analysis.

We studied the asbestos content of bronchoalveolar lavage fluid (BALF) from 9 patients with asbestosis, 17 asbestos exposed but without asbestosis, 15 with idiopathic pulmonary fibrosis (IPF) and 9 nonexposed volunteers. The cellular lavage pellet was digested and filtered for asbestos body (AB) quantification by light microscopy (LM) and analysis of numbers and types of uncoated fibers (UF) by scanning electron microscopy (SEM) and energy dispersive x-ray analysis. BALF of asbestosis patients had significantly higher AB content than that of the combined IPF and volunteer groups. The UF content as determined by SEM was similar in all four groups. Commercial amphiboles (amosite or crocidolite) were identified more frequently in BALF from patients with asbestosis than from the other groups. ABs were detected by SEM only in highly exposed individuals. We conclude that the findings of > 1 AB per 10(6) cells or 1 AB/mL BALF by LM and of ABs or commercial amphibole fibers by SEM are indicative of considerable exposure to asbestos in the majority of cases.

Adult↗