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Biomedical subjects

D Peppi

Publications and source records attributed to D Peppi.

14 recordsLinked to original sources
PubMed1992

A two-bag system for continuous measurement of oxygen uptake.

Collection of mixed expired gas in a bag has been a classic method for the estimation of VO2 during the steady state but has not been employed during unsteady state exercise in part because there is a need for suspending the acquisition of data during the period of gas analysis unless many bags are used. In this study a two-bag system is described in which one bag fills while the other is analyzed. Bag volume is under the control of the operator, and we employed volumes of 30 to 50 L. Thirty-one subjects were studied with this circuit in a progressive treadmill test. Although VO2 could be falsely elevated during periods of overbreathing, this source of error could be identified and its effect reduced if VO2 was plotted against both ventilation and power requirement. Plateau values of VO2 were identified only in six subjects and the ventilatory threshold in 16.

Adult↗
PubMed1991

The effect of progressive exercise on the equilibrium rebreathing cardiac output method.

The equilibrium CO2 rebreathing method has been used in the study of exercise cardiac output (Q) in health and disease, but the requirement for a steady state has usually limited its application to step function exercise. This limits testing to only a few levels of exertion in a laboratory session. We have devised a treadmill test where the grade is flat at the beginning and rises continuously at 1%.min-1 after stable measurements are obtained during level walking. The walking speed is determined by the subject's comfort and tolerance for fast walking. In series I seven normal subjects were studied with this protocol, and an automated system was employed for estimation of Q and oxygen uptake (VO2). For comparison of steady state and progressive tests, an interpolation method was devised which furnished a value of Q (progressive) that could exist at the value of VO2 obtained during the steady state. The average difference in Q so estimated between the steady state and the unsteady state was 0.3 l.min-1, SD = 1.7. This difference was less than the difference between averages of duplicate values of Q obtained during the steady state (1.11.min-1, SD = 16), and the difference between the two differences was not significant. Based on 51 determinations of Q and VO2 in eight normal subjects the unsteady state procedure furnished an average value of the relation slope of delta Q/delta VO2(-1) of 4.8 l.l-1. We conclude that the equilibrium CO2 method can be used to depict the Q, VO2 relationship over the range of VO2 at which rebreathing is tolerable.

Adult↗
PubMed1986

Dyspnea in patients with hyperbradykininism and excessive venous pooling.

In the original description of the syndrome of hyperbradykininism, dyspnea on exertion was not described. However, in five women with the syndrome, ages 31 to 58, four of whom had at least one elevated value of blood kinin as determined by radioimmunoassay, dyspnea on exertion was a prominent complaint. During treadmill walking at a constant power requirement against gravity, expired air gas collections and equilibrium carbon dioxide rebreathing were performed. Seventeen apparently healthy women, ages 18 to 48, served as control subjects. Although oxygen uptake was the same in both groups by design (oxygen uptake 0.91 liters per minute, 0.11 standard deviation [SD], in the control subjects; oxygen uptake 0.97 liters per minute, 0.12 [SD] in the patients), cardiac output was significantly reduced in the patients (cardiac output 8.4 liters per minute, 1.3 [SD], in the control subjects; cardiac output 6.3 liters per minute, 0.9 [SD], in the patients, p less than 0.01). End-tidal carbon dioxide tension was significantly lower in the patients (end-tidal carbon dioxide tension 41 torr, 3 [SD], for the control subjects; end-tidal carbon dioxide tension 33 torr, 7 [SD], for the patients). In one patient, repeated studies over a 12-month period demonstrated a positive relationship between end-tidal carbon dioxide tension and the respiratory exchange ratio. (Respiratory exchange ratio = 0.01 + 0.027 X end-tidal carbon dioxide tension, 0.073 standard error of the estimate [SEE], 0.71 regular correlation coefficient, n = 20). This relationship was opposite to that expected with voluntary overbreathing; it was interpreted to mean that reduced cardiac output with exercise occurred to a variable degree and was the cause of hyperpnea and hypocapnia. In the same patient, studies at exercise with and without the Jobst (antigravity) garment and studies at exercise in the supine and erect position were consistent with the hypothesis that dyspnea and exercise intolerance were caused by venous pooling when standing. It is concluded that hyperbradykininism is characterized not only by orthostatic hypotension and tachycardia with light-headedness, as originally described, but also by severe dyspnea on exertion with exercise intolerance. The mechanism remains obscure, and the treatment is unsatisfactory, but temporary improvement in the abnormal physiology can be achieved in some patients with the use of an antigravity garment.

Adult↗
PubMed1981

Relationship of rib cage and abdomen motion to diaphragm function during quiet breathing.

Although rib cage (RC) and abdomen (Ab) motion is believed to reflect intercostal and diaphragm contributions to breathing, systematic investigations have failed to confirm this. We measured inspiratory changes in RC and Ab anterior-posterior diameter (delta RC and delta Ab) both corrected for volume equivalence (isovolume) and not corrected (isodistance, observed), and correlated these with simultaneous changes in gastric (delta Pab) and esophageal (delta Ppl) pressure: delta Pab - delta Ppl = delta Pdi, the change in transdiaphragmatic pressure. The delta Pab/delta Pdi was used as an index of the relative contribution of diaphragm motion to the breathing process. Relative abdomen motion was expressed as delta Ab/(delta Ab + delta RC). Isodistance and isovolume delta Ab/(delta Ab + delta RC) correlated, R = 0.69; observed abdomen motion overestimated abdomen-diaphragm contribution to tidal volume. Isodistance delta Ab/(delta Ab + delta RC) was less for women than men; isovolume delta Ab/(delta Ab + delta RC) was similar for the two sexes. Among individuals, isodistance delta Ab/(delta Ab + delta RC) correlated with delta Pab/delta Pdi (R = 0.73, P less than 0.001). Within a given individual, the mean R for seven subjects for delta Pab/delta Pdi vs delta Ab/(delta Ab + delta RC) was 0.90. We conclude that observed rib cage and abdomen motion reflects intercostal and diaphragm contributions to breathing; the correlation is better within a given subject than among individuals.

Abdomen↗
PubMed1980

Mixed venous CO2 tension during exercise.

A series of experiments was undertaken in a total of 95 adult subjects, of whom 25 had coronary artery disease, to evaluate the extrapolation (Defares) CO2 rebreathing method vs. the equilibrium (Collier) method for estimating mixed venous CO2 tension. Collier values were corrected for the downstream effect, whereas Defares values were uncorrected. Although the methods gave similar mean values in separate series with normal subjects walking on a treadmill set at 123 W for 3 min, Collier values had a coefficient of variation (CV) of 2.5% in duplicate determinations and Defares values had a CV of 4.5%. In paired comparisons Defares values averaged either higher or lower than Collier values depending on variations in technique and the analysis of Defares tracings. Collier values were essentially unaffected by the duration of the rebreathing period (10 vs. 15 s). The Collier technique appears to be superior for the exercise evaluation of cardiac output in healthy and diseased subjects when the goal is obtain values at 82 or 123 W in single test sessions.

Adult↗
PubMed1979

One- and three-minute exercise response in coronary artery disease.

Treadmill exercise responses of oxygen uptake (VO2), CO2 production (VCO2), and venoarterial CO2 difference (Cv-Ca), measured by CO2 rebreathing (Defares technique) at 1 and 3 min of exercise, were studied in two separate series of control (apparently healthy) and coronary artery disease (CAD) subjects. In the 1-min series there were 21 controls and 15 CAD subjects. In the 3-min series there were 21 controls and 18 CAD subjects. All were males, ages 30--60 yr, and the CAD subjects had histories of myocardial infarction. In both series VO2 at 1 min and power requirement (P ) = 1,000 (VO2-1-1,000) was estimated where P =weight (kg) X grade (fractional) X walking speed (m/min). In the 1-min series (P = 1,000) all measurements were made at 45--60 s in separate test runs. In the 3-min series P was 750 kg.m/min, VCO2 and VO2 were measured at 2.5--3 min exercise, and Cv-Ca was measured at 3--3.25 min in the same test run. Data indicate that the average cardiac output (Q) for control subjects was 15 l/min in both series with lower values for CAD subjects. At 1 min reduced Q was accompanied by reduced VO2 or VCO2 and increased Cv-Ca, whereas at 3 min reduced Q was accompanied by increased Cv-Ca.

Adult↗
PubMed1979

Measurement of transdiaphragmatic pressure with a single gastric-esophageal probe.

A single gastric-esophageal probe, 5 mm in diam, with two transducers mounted near the tip has been used to measure transdiaphragmatic pressure in human subjects. The transducers are linear up to at least 200 cmH2O pressure and provide equal deflections for both positive and negative pressures. The method is shown to give results comparable to the standard procedure using two balloon-tipped catheters, one in the stomach and one in the esophagus.

Catheterization↗
PubMed1977

Prospective study of controlled oxygen therapy. Poor prognosis of patients with asynchronous breathing.

Thirty-two patients were evaluated within 24 hours of admission for 36 episodes of acute respiratory failure (arterial oxygen pressure less than or equal to 50 mm Hg). Clinical data, spirometric determinations, blood gas analysis, and synchronization of chest (rib cage) and abdominal (diaphragmatic) breathing movements were studied. All patients were initially treated with controlled oxygen therapy. In 25 episodes the patients recovered without intubation (successes). In nine episodes the patients required intubation and assisted ventilation; two of these patients died. Two patients died without intubation. The 25 successful episodes were compared with the 11 requiring intubation or associated with death (failures). The breathing pattern proved to be the best single factor for predicting success or failure (77 percent correct prediction). The breathing pattern plus the arterial carbon dioxide tension on admission was the best two-factor guide (86 percent correct prediction). Patients with asynchronous breathing and severe hypercapnia are so unlikely to do well with a program of controlled oxygen therapy that preparations for intubation and assisted ventilation should be made on admission and such measures should be instituted at the first sign of deterioration.

Airway Obstruction↗
PubMed1976

Effect of cardiac, pulmonary, and vascular disease on one-minute oxygen uptake.

A simplified method for estimation of one-minute oxygen uptake (VO2-1) during treadmill grade walking at vertical power requirements of 250, 750, and 1,000 kg-meters/min was devised, where power=weight (kg) X grade (fractional) X walking speed. All subjects were men. There were 29 controls, 34 subjects with coronary arterial disease (of whom 18 had had myocardial infarction), nine subjects with diffuse pulmonary disease, and four subjects with ischemic vascular disease. Abnormally reduced values for VO2-1 were related to these diseases and, more specifically, to a history of myocardial infarction and (in pulmonary subjects) to reduced single-breath diffusing capacity. Lowest values of VO2-1 for a group were found in ischemic vascular disease. Reduced response of VO2-1 may therefore be caused by central defects of oxygen transport.

Adult↗
PubMed1975

Asynchronous breathing movements in patients with chronic obstructive pulmonary disease.

An electromagnetic ventilation monitor was used to record the separate anterior-posterior movements of the chest and abdomen during the breathing cycle in 30 patients with chronic obstructive pulmonary disease (COPD) and in 10 normal subjects. In all normal subjects and 17 COPD patients, the chest and abdomen movements were syndhronous and in phase with the flow of air as measured with a spirometer. In 13 COPD patients chest movement was synchronous with the flow of air, but the abdomen moved inward suddently near or at end inspiration and then outward during a variable part of expiration. Compared to COPD patients with a normal breathing pattern, those with asynchronous breathing movements had poorer ventilatory mechanics and 10 of the 13 were dependent on assisted ventilation. Nine of the 13 patients with asynchronous breathing have died in a 10 month period, a significantly higher mortality than in those with normal breathing.

Abdomen↗