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Biomedical subjects

S M Guenther

Publications and source records attributed to S M Guenther.

14 recordsLinked to original sources
PubMed1988

Variability of resting respiratory drive and timing in healthy subjects.

Studies of breathing pattern have focused primarily on changes in the mean values of the breathing pattern components, whereas there has been minimal investigation of breath-to-breath variability, which should provide information on the constancy with which respiration is controlled. In this study we examined the variability of breathing pattern both on a breath-to-breath and day-to-day basis by calculating the coefficient of variation (i.e., the standard deviation expressed as a percentage of the mean). By examining breath-to-breath data, we found that the coefficients of variation of tidal volume (VT) and fractional inspiratory time (TI/TT, an index of timing) obtained with an inductive plethysmograph and spirometer were within 1% of each other. Examination of breath-to-breath variability in breathing pattern over a 15-min period in 65 subjects revealed large coefficients of variation, indicating the need to base calculations on a relatively large number of breaths. Less breath-to-breath variability was observed in respiratory frequency [f, 20.8 +/- 11.5% (SD)] and TI/TT (17.9 +/- 6.5%) than in VT (33 +/- 14.9%) and mean inspiratory flow (VT/TI, an index of drive; 31.6 +/- 12.6%; P less than 0.0001). Older subjects (60-81 yr) displayed greater breath-to-breath variability than young subjects (21-50 yr). Use of a mouthpiece did not affect the degree of variability.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Accuracy of the respiratory inductive plethysmograph during loaded breathing.

Indirect methods of measuring ventilation, such as the respiratory inductive plethysmograph (RIP), operate on the assumption that the respiratory system possesses two degrees of freedom of motion: the rib cage and abdomen. Accurate measurements have been obtained in many patients with pulmonary disease who possess additional degrees of freedom. Since calibration and validation of the RIP was carried out during quiet breathing in these patients, the amount of asynchronous or paradoxic breathing was presumably similar during the calibration and validation runs. Conversely, accuracy might be lost if following the initial calibration procedure the magnitude of chest wall distortion increased during subsequent validation runs. We calibrated the RIP during quiet breathing and examined its accuracy while subsequently breathing against resistive loads that required the generation of 20-80% of the subject's maximum inspiratory mouth pressure (Pmmax). We compared the relative accuracy of three commonly employed calibration methods: isovolume technique, least-squares technique, and single position loop-area technique. Up to 60% of Pmmax, 89% of the RIP values with the least-squares technique were within +/- 10% of simultaneous spirometric (SP) measurements and 100% were within +/- 20% of SP, compared with 63 and 91%, respectively, for the loop-area technique and 19 and 54%, respectively, for the isovolume technique. At 70 and 80% of Pmmax accuracy deteriorated. Accuracy of respiratory timing was judged in terms of fractional inspiratory time (TI/TT).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Does rib cage-abdominal paradox signify respiratory muscle fatigue?

Studies suggesting that abnormal motion of the rib cage (RC) and abdomen (Ab) may indicate respiratory muscle fatigue have not separated the influence of respiratory load from that of fatigue in its pathogenesis. We hypothesized that abnormalities on RC-Ab motion are primarily related to increased load rather than fatigue. We tested this hypothesis in subjects breathing against resistive loads while maintaining 30 and 60% of maximum mouth pressure (Pmmax). RC-Ab asynchrony and paradox and the degree of variation in compartmental contribution to tidal volume were measured by inductive plethysmography and quantitated by the Konno-Mead method of analysis. Comparing measurements of base line and 30 and 60% of Pmmax indicated that the degree of asynchrony, paradox, and variation in compartmental contribution were significantly related to the level of the load; significant abnormalities were observed at even 30% of Pmmax, a target pressure that can be sustained indefinitely. In another group of subjects, fatigue was induced by sustaining 60% of Pmmax to the limits of tolerance. Indexes of abnormal RC-Ab motion increased from base line during the 1st min of loaded breathing but displayed no progression from the beginning to the end of the fatigue run. Immediately on discontinuation of the load, the indexes returned to levels similar to base line despite persistence of the fatigue state. These results in healthy subjects breathing against severe resistances indicate that RC-Ab asynchrony and paradox and variation in compartmental contribution to tidal volume are predominantly due to increases in respiratory load rather than muscle fatigue.

Abdomen↗
PubMed1987

Konno-Mead analysis of ribcage-abdominal motion during successful and unsuccessful trials of weaning from mechanical ventilation.

Respiratory muscle fatigue is considered a common cause of weaning failure but its detection is hampered by the lack of a satisfactory diagnostic test. Abdominal paradox has been proposed as a valuable clinical index of fatigue and thus its presence may lead to curtailment of weaning trials. However, sensitivity and specificity of this sign as a predictor of weaning outcome is unknown. We hypothesize that abnormal ribcage-abdominal (RC-Ab) motion is a common finding in the early stages of weaning and its presence does not inevitably imply an unsuccessful weaning outcome. We tested this hypothesis in patients undergoing a weaning trial: one group had a successful weaning outcome and were extubated (n = 10) and the other group failed the trial (n = 7). Normal RC-Ab motion was separately characterized in 17 healthy subjects. Employing a calibrated respiratory inductive plethysmograph, quantitative assessment of asynchrony and paradox was obtained by computing several indices from series of breaths at fixed time periods using the Konno-Mead method of analysis. During the weaning trial, both groups of patients displayed significant increases in asynchrony and Ab paradox compared to normal values. As a group, patients who failed the trial displayed significantly greater asynchrony and paradox of the RC and Ab than patients with a successful outcome. However, there was considerable overlap between the individual patients in the 2 study groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1987

Comparison of gynecologic health care problems between lesbians and bisexual women. A survey of 2,345 women.

A survey of reproductive system problems was conducted in a large group of lesbians (n = 1,921) and bisexual women (n = 424) in a nonclinical setting. Demographically the groups were similar: the majority of respondents were white, urban and well educated. A history of heterosexual coitus was common in both groups (bisexuals, 95%; lesbians, 77%). Bisexuals were more likely than lesbians to report an abnormal Papanicolaou smear, cystitis, genital herpes, gonorrhea and vaginal infections. When sexual orientation was controlled for, most, but not all, of these differences were associated with a difference in reported frequency of (prior) coitus. Despite the lower risk of certain problems, however, the lesbians who reported no previous coitus did report the occurrence of vaginitis, abnormal Papanicolaou smears and genital herpes. There were no differences in past oral contraceptive use, endometriosis, menstrual dysfunction or breast disease. The lesbian group reported a greater percentage of hysterectomies. These data suggest that, overall, the sexual behaviors of lesbians are associated with a lower risk of most sexually transmitted diseases.

Adult↗
PubMed1987

Parenting desires among bisexual women and lesbians.

Parenting desires were ascertained among a large group of lesbians (n = 1,921) and bisexual women (n = 424) recruited in a nonclinical setting. More than 50% of each sexual-orientation group had considered having a child since recognizing their current sexual identity. Lesbians were more likely than bisexuals to favor adoption and donor insemination as options, whereas bisexuals were more likely to consider intercourse with either a cooperative or unsuspecting man. Overall, however, 47 women (2%) reported success in obtaining a child through one of these options.

Adoption↗
PubMed1986

Breathing pattern and metabolic behavior during anticipation of exercise.

The mechanisms responsible for the marked increase in ventilation at the onset of exercise are incompletely defined. A conditioned response to exercise anticipation has been suggested as an influencing factor, but systematic measurements have not been made during the transition from rest to the time when exercise is anticipated but has not yet commenced. We tested the hypothesis that cortical activity associated with the anticipation of exercise causes hyperpnea, which is at least partly responsible for the increased ventilation at the onset of exercise. To assess the influence of continuous cortical activity in the absence of exercise anticipation the subjects performed mental arithmetic tasks. Fifteen subjects performed the two experiments in a random order. Ventilation was measured noninvasively using a calibrated respiratory inductive plethysmograph and end-tidal CO2 concentration (FETCO2) was monitored at the nasal vestibule. Both exercise anticipation and mental arithmetic caused an increase in minute ventilation (VI) (P less than 0.01) and mean inspiratory flow (VT/TI, P less than 0.01), which reflects respiratory center drive, although the derivation differed in that the former was volume based, whereas the latter was due to alteration in timing. Despite the increase in VI, FETCO2 remained constant in both instances. In a complementary study the constant FETCO2 in the face of increased VI was shown to be due to increased CO2 output. The results show that the mere anticipation of exercise causes an increase in ventilation. The mechanism responsible for this hyperpnea cannot be due solely to respiratory center activation because of the constancy of FETCO2 and the associated alterations in cardiac and metabolic behavior.

Adult↗
PubMed1986

The pattern of breathing during successful and unsuccessful trials of weaning from mechanical ventilation.

We prospectively examined the pattern of breathing in patients being weaned from mechanical ventilation: one group (n = 10) underwent a successful weaning trial and were extubated, whereas another group (n = 7) developed respiratory failure and required the reinstitution of mechanical ventilation. During the period of ventilator support, minute ventilation (VI), tidal volume (VT), and respiratory frequency (f) were similar in the 2 groups. After discontinuation of the ventilator, VI remained similar in the 2 groups, but VT was lower and f was higher in the patients who failed the trial compared with those who were successful, 194 +/- 23 and 398 +/- 56 ml (p less than 0.001), respectively, and 32.3 +/- 2.3 and 20.9 +/- 2.8 breaths/min (p less than 0.001), respectively. The failure group displayed a significant increase in PaCO2 (p less than 0.005) during spontaneous breathing, without a concomitant increase in the alveolar-arterial PO2 difference. Eighty-one percent of the variance in PaCO2 was accounted for by the pattern of rapid, shallow breathing. During weaning, resting respiratory drive (reflected by mean inspiratory flow, VT/TI) and fractional inspiratory time (TI/Ttot) were similar in the 2 groups. The patients in the failure group showed significant increases in VT/TI, 265 +/- 27 to 328 +/- 32 ml/s (p less than 0.01), and VI, 5.82 +/- 0.53 to 7.32 +/- 0.52 L/min (p less than 0.01), from the beginning to the end of the weaning trial; VT and f showed no further change.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Respiratory↗
PubMed1985

Health care attitudes and experiences during gynecologic care among lesbians and bisexuals.

Bisexuals (N = 424) and lesbians (N = 1,921) were surveyed regarding their sources of gynecologic care, utilization patterns, openness with physicians, and assessment of quality of care. About 40 per cent of each group believed that physician knowledge about their sexual preference would hinder the quality of medical care and about as many believed that it would have no effect. About one-third in each group had not disclosed their sexual behavior although they desired to do so. Physicians rarely requested this information. A lesbian physician was overwhelmingly preferred for gynecologic care (96 per cent), particularly for problems with sexual functioning. Previous satisfaction with gynecologic care was most often described as "adequate," but almost as often as "variable" and "poor." Data suggest that quality, utilization, and medical outcomes of gynecologic care to this group would be improved if physicians would communicate greater awareness of sexual orientation in a nonprejudicial manner and ensure confidentiality.

Adult↗
PubMed1981

Factors influencing lesbian gynecologic care: a preliminary study.

One hundred seventeen homosexual women were surveyed to determine their health care utilization patterns, their gynecologic and obstetric problems, and their attitudes toward physicians. It was found that these women actively utilized the health care system, although many chose less traditional sources. The gamut of both obstetric and gynecologic problems were seen, but venereal disease and cervical dysplasia were uncommon. No medical problems specific to homosexual women were identified. Many of these lesbians expressed concern about the effect on their health care of physicians' negative attitude toward homosexuals.

Adult↗