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Biomedical subjects

K J Killian

Publications and source records attributed to K J Killian.

At least 19 recordsLinked to original sources
PubMed1995

Muscle strength, symptom intensity, and exercise capacity in patients with cardiorespiratory disorders.

The contribution of muscle strength to symptom intensity and work capacity was examined in normal individuals and patients with cardiorespiratory disorders. Respiratory muscle strengths (maximal inspiratory and expiratory pressures) and peripheral muscle strengths (leg extension, leg flexion, seated bench press, and seated row) were measured in 4,617 subjects referred for clinical exercise testing. Subjects then rated the intensity of leg effort, discomfort with breathing (dyspnea), and chest pain (Borg scale) during an incremental exercise task (100 kpm/min each minute) to capacity on a cycle ergometer. Subjects were classified into groups on the basis of pulmonary function, drug therapy for cardiac disorders, and the presence of chest pain during exercise with electrocardiographic changes indicative of myocardial ischemia. Respiratory and peripheral muscle strengths, normalized for differences in age, sex, and height, were significantly reduced in patients with cardiorespiratory disorders compared with normal individuals. Muscle strength was a significant contributor to symptom intensity and work capacity in both health and disease; a two-fold increase in muscle strength was associated with a 25 to 30% decrease in the intensity of both leg effort and dyspnea and a 1.4- to 1.6-fold increase in work capacity. These results emphasize the need for an integrative approach in the assessment and therapeutic management of exercise intolerance, which considers the contribution of muscle weakness to excessive symptoms and reduced work capacity, in addition to the contribution of ventilatory, gas exchange, and circulatory impairments.

Angina Pectoris↗
PubMed1994

Mechanisms of exertional dyspnea.

To understand why someone is dyspneic during exercise, we need to follow the advice of Sir Francis Bacon: "No natural phenomenon can be adequately studied in itself alone, but to be understood must be considered as it stands connected with all of nature." In the present context, this implies the careful measurement of events related to metabolism, circulation, and respiration and of the associated sensory events as these systems adapt to the strain and stress of exercise.

Dyspnea↗
PubMed1993

Factors determining pulmonary function in adolescent idiopathic thoracic scoliosis.

Adolescent idiopathic thoracic scoliosis may lead to severe pulmonary impairment and early death, but the responsible factors are poorly understood; pulmonary function is only weakly related to the angle of scoliosis. We performed a cross-sectional study using multivariate analysis to identify the individual and additive influence of different features of spinal deformity and nonstructural factors on pulmonary impairment. Pulmonary function was assessed by measuring lung volumes and diffusing capacity, with a priori selection of vital capacity (expressed as percentage of predicted, % VC) as the primary index of pulmonary impairment. Radiologic and physiologic measurements were made independently in 66 subjects who had not previously had spinal surgery. Angle of scoliosis (p = 0.01) was one of four features of spinal deformity associated with reduced % VC; greater number of vertebrae involved (p = 0.007), cephadal location of the curve (p = 0.04), and loss of the normal thoracic kyphosis (p = 0.002) made an equal and additive contribution to pulmonary impairment. Spinal deformity led to reductions in VC, primarily by reducing TLC. Spinal column rotation, respiratory muscle strength, and duration of the curvature were not related to pulmonary function (p > 0.05). We conclude that features of the spinal deformity are the major determinants of pulmonary impairment in idiopathic thoracic scoliosis but that the relationship between deformity and impairment is complex. The severity of pulmonary impairment cannot be inferred to a clinically useful extent from the angle of scoliosis alone.

Adolescent↗
PubMed1993

Factors influencing work capacity in adolescent idiopathic thoracic scoliosis.

The factors contributing to reduced work capacity (disability) in adolescent idiopathic thoracic scoliosis are poorly understood. We performed a cross-sectional study using multivariate analysis to identify the individual and additive influence of spinal deformity, pulmonary impairment, and muscular function on work capacity in 79 subjects with idiopathic scoliosis (angle of scoliosis 45 +/- 18.5 degrees, SD). Work capacity was measured using an incremental cycle test, and the cardiorespiratory response to exercise was compared with that of normal subjects. Work capacity was reduced (% Wcap, 86%; 95% CI 81.9 to 89.7), indicating significant disability. The % Wcap was unrelated to the nature and extent of spinal deformity (p > 0.05). Leg muscularity and pulmonary impairment had an additive influence on work capacity, the relationship with muscularity being the stronger of the two. Independently of muscularity and pulmonary impairment, a high heart rate response at submaximal work rates was also associated with a reduced work capacity. Ventilation was normal for metabolic demands. During exercise, the tidal volumes of scoliotic subjects were reduced in proportion to the vital capacity. We conclude that disability occurs with mild to moderate idiopathic scoliosis and appears to be related to a combination of reduced ventilatory capacity, reduced muscularity, and cardiovascular deconditioning. These findings suggest that physical activity should be encouraged in subjects with idiopathic scoliosis to maintain peripheral muscle and cardiovascular conditioning, thereby minimizing disability.

Adolescent↗
PubMed1993

Factors contributing to dyspnoea during bronchoconstriction and exercise in asthmatic subjects.

The purpose of the present study was to identify: 1) whether dyspnoea during bronchoconstriction and exercise is related, in asthmatic subjects; and 2) to what extent baseline pulmonary function and respiratory muscle strength contribute to dyspnoea under both conditions. One hundred and seventy five consecutive subjects, referred with suspected asthma, rated the intensity of dyspnoea (Borg scale 0-10): 1) during the administration of doubling concentrations of methacholine to 32 mg.ml-1 methacholine, or until the baseline forced expiratory volume in one second (FEV1) was reduced by 20%; and 2) during incremental cycle ergometry (100 kpm.min-1 each minute) to maximal capacity. 138/175 subjects achieved a 20% reduction in their baseline FEV1; 18 of the 138 were excluded, 2 children and 16 with complicating pulmonary disorders (diffusing capacity of the lung for carbon monoxide (DLCO) and/or total lung capacity (TLC) < 70% predicted). The remaining 120 out of 175 constituted the study population. Dyspnoea following a 20% reduction in the baseline FEV1 (Dys20%) was linearly interpolated, using the rating of dyspnoea and the FEV1 at the two final concentrations of methacholine. In the 120 asthmatic subjects, the mean intensity of dyspnoea was "moderate" (2.9, SD 1.91; Borg 0-10) and the intensity across subjects was not significantly related to baseline FEV1, vital capacity (VC), FEV1/VC, DLCO, TLC and maximal static inspiratory pressure (MIP), alone or in combination.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Dyspnea and leg effort during incremental cycle ergometry.

The aim of this study was to establish the perceived magnitude of dyspnea (discomfort associated with breathing) and leg effort experienced by normal subjects during a standardized incremental exercise test to maximal capacity; 460 normal subjects (297 male and 163 female 20 to 70 yr of age) were studied. The perceptual magnitude of both symptoms was rated using simple descriptive phrases (slight, moderate, maximal) tagged to numbers from zero to 10 on the Borg scale, which is an interval scale with ratio properties. Leg effort and dyspnea increased with power output, were higher in women than in men (p less than 0.0001), increased with advancing age (p less than 0.0001), and declined as height increased (p less than 0.0001). Leg effort = 4.82 + 0.007 kpm/min + 1.05 sex + 0.04 age - 0.055 Ht (r = 0.78; SD, 1.80). Dyspnea = 4.96 + 0.006 kpm/min + 0.96 sex + 0.04 age - 0.05 Ht (r = 0.74; SD, 1.80) (m = 1; f = 2). With power output expressed as a percentage of maximal power output (%MPO) both symptoms increased in an alinear manner. Effort = 0.0014 * %MPO1.86 (r = 0.86; SD, 1.50). Dyspnea = 0.0016 * %MPO1.79 (r = 0.81; SD, 1.57). Sex, age, or stature did not contribute to the rating of effort or dyspnea when power output was normalized in this way.

Adult↗
PubMed1992

Exercise capacity and ventilatory, circulatory, and symptom limitation in patients with chronic airflow limitation.

Dyspnea, leg effort (Borg 0 to 10 scale), ventilation, and heart rate (VEmax/VEcap; HRmax/HRcap expressed as a percentage of capacity) were measured at maximal exercise (cycle ergometer) in 97 patients with chronic airflow limitation (CAL) (FEV, 46.6 +/- 14.23% of predicted) and compared with 320 matched control subjects. Patients with CAL achieved a maximum power output of 86 +/- 39.5 W (60 +/- 23.2% of predicted) compared with 140 +/- 37.5 W (98 +/- 14.5% of predicted) in controls (p less than 0.0001), VEmax/VEcap was 72 +/- 19.3% compared with 53 +/- 18.6% (p less than 0.0001), and HRmax/HRcap was 76 +/- 13.5% compared with 82 +/- 13% (p less than 0.001). These findings were expected. The median intensity of dyspnea was 6 (severe to very severe) and leg effort was 7 (very severe) in both groups, and these findings were unexpected. The patients with CAL were handicapped by an increase in both dyspnea and peripheral muscular effort relative to the actual power output. The rating of dyspnea exceeded leg effort in 25 (26%) of CAL versus 69 (22%) control subjects: the rating of leg effort exceeded dyspnea in 42 (43%) CAL and 117 (36%) control subjects; both were rated equally in 30 (31%) CAL and 134 (42%) control subjects, respectively (NS). VEmax/VEcap and HRmax/HRcap were not significantly different in those limited by dyspnea, leg fatigue, or a combination of both. All values are expressed +/- SD.

Cardiac Output↗
PubMed1991

Breathing during prolonged exercise in humans.

1. Six normal subjects cycled to endurance or for 60 min at four work rates (WR 1-4): mean of 34% working capacity (93 watts for 60 min); 43% (120 watts for 56 min); 63% (177 watts for 37 min); and 84% (233 watts for 12 min), to determine how breathing pattern and dyspnoea change during prolonged activity. Four to six minutes were allowed to establish steady state and subsequent changes were considered to be endurance related. 2. Dyspnoea (Borg scale, 0-10) increased with the duration of activity at all work rates. 3. Ventilation (VE) did not change at WR1; increased from 44 to 47 l min-1 at WR2; from 60 to 88 l min-1 at WR3; and from 111 to 132 l min-1 at WR4. Dyspnoea was significantly and independently related to ventilation and duration of activity: dyspnoea = 0.004 VE1.36 time 0.25 (r = 0.81; partial F 202 and 26 respectively). 4. Inspiratory resistance did not increase at any work rate. Dynamic elastance remained constant during WR1, WR2 and WR3 but increased from 7.4 to 9.1 cmH2O l-1 during WR4. 5. Peak inspiratory pressure did not increase, and the increase in VE was accomplished by an increased breathing frequency without change in duty cycle. 6. Duration of activity is an important contributor to dyspnoea independent of changes in respiratory muscle contractile activity.

Adult↗
PubMed1991

Effort and dyspnoea during work of varying intensity and duration.

This study quantified the separate contributions of the intensity of exercise and its duration to muscular effort and dyspnoea during cycle ergometry. Six normal subjects estimated the perceived intensity (Borg scale 0-10) of peripheral muscular effort and dyspnoea during incremental exercise to their maximum work capacity (Wcap). On separate days, the same subjects exercised to endurance or 60 min at work rates rated for leg effort on the initial incremental test as: 2 ("slight", 33.1 +/- 1.45% Wcap) (mean +/- SE); 3 ("moderate", omission 83.6 +/- 3.87% Wcap). Perceived leg effort increased by a factor of 4.4 (2(2.13)) with a doubling of work rate and by 1.3 (2(0.39)) with a doubling of duration, as expressed by: Leg effort = k x %Wcap2.13 x Time0.39 (r2 = 0.87) Perceived dysponea increased 5.3-fold with a doubling of work rate and by 1.4-fold with a doubling of duration: Dysponea = k x %Wcap2.41 x Time0.47 (r2 = 0.75) Changes in work intensity, rather than duration, dominated symptom magnitudes such that in the performance of a given task, halving the intensity and doubling the duration of activity reduces the maximal intensity of muscular effort and dyspnoea to less than a third.

Adult↗
PubMed1990

Methacholine airway responsiveness decreases during exercise in asthmatic subjects.

In many asthmatic subjects, bronchoconstriction develops 2 to 5 min after exercise, reaches a maximum at approximately 10 min, and declines over the next 60 min. However, bronchodilation is typically observed during and immediately after exercise. We measured the bronchoconstrictor responses to increasing concentrations of inhaled methacholine at rest and during two levels of exercise in seven asthmatic subjects to determine the protection against bronchoconstriction afforded by exercise. On the first day, an incremental Stage 1 exercise test was performed to determine the work capacity (Wcap) of each subject. On the second, third, and fourth days, methacholine was inhaled at rest or during steady-state exercise at one-third or two-thirds of Wcap. The bronchoconstrictor response to methacholine was significantly reduced during exercise (p less than 0.0001). The concentration of methacholine required to produce a 20% reduction in FEV1 (PC20) increased from 2.80 mg/ml (%SEM, 1.62) at rest to 7.29 mg/ml (%SEM, 1.43) during exercise at one-third Wcap, and to 31.03 mg/ml (%SEM, 1.74) during exercise at two-thirds Wcap (p less than 0.001). This study has demonstrated that there is greater than tenfold protection against bronchoconstriction by methacholine during exercise, and the magnitude of the protection depends on the intensity of exercise performed. The mechanism of this protection is not known, but may have clinical utility.

Adolescent↗
PubMed1989

An approach to dyspnea in cancer patients.

There are many potential causes of dyspnea in the patient with cancer. Ultimately, a sense of increased respiratory effort is common to all of these diverse situations. An organized approach to dyspnea in the cancer patient is presented based on psychophysical principles, and treatment modalities are suggested.

Airway Resistance↗
PubMed1989

Influence of age and stature on exercise capacity during incremental cycle ergometry in men and women.

The present study re-evaluated the accuracy of standards for maximal exercise capacity (Wcap) recently reported from our laboratory by examining the interaction between height and age on Wcap achieved and predicted in 1,071 subjects (732 males and 339 females). They underwent an incremental exercise test on a cycle ergometer using the same incremental protocol and exercise mode as the previous study, and were retrospectively judged to be normal. Although Wcap predicted was either not significantly different (males) or underestimated Wcap by less than 5% (females, p less than 0.05), significant differences were found in subjects at the extremes of the population ranges for height and age. The influences of age 9yr) and height (m) were found to be nonlinear and interactive, as described by the equations: Males: Wcap = 1506*Ht2.70*Age-0.46(r = 0.78) (lower limit 81% pred) Females: Wcap = 969*Ht2.80*Age-0.43(r = 0.77) (lower limit 79% pred) Wcap (kpm/min) predicted by these equations was compared to Wcap achieved by the 100 subjects who took part in the original study; no significant differences were found (paired t test, p less than 0.05). The interactive influences of age and height expressed by the equations are more plausible from a biological point of view than the linear, additive relationships previously described. The equations should be more reliable than previous equations for patients referred for exercise testing.

Aging↗
PubMed1988

Inspiratory muscles during exercise: a problem of supply and demand.

The capacity of inspiratory muscles to generate esophageal pressure at several lung volumes from functional residual capacity (FRC) to total lung capacity (TLC) and several flow rates from zero to maximal flow was measured in five normal subjects. Static capacity was 126 +/- 14.6 cmH2O at FRC, remained unchanged between 30 and 55% TLC, and decreased to 40 +/- 6.8 cmH2O at TLC. Dynamic capacity declined by a further 5.0 +/- 0.35% from the static pressure at any given lung volume for every liter per second increase in inspiratory flow. The subjects underwent progressive incremental exercise to maximum power and achieved 1,800 +/- 45 kpm/min and maximum O2 uptake of 3,518 +/- 222 ml/min. During exercise peak esophageal pressure increased from 9.4 +/- 1.81 to 38.2 +/- 5.70 cmH2O and end-inspiratory esophageal pressure increased from 7.8 +/- 0.52 to 22.5 +/- 2.03 cmH2O from rest to maximum exercise. Because the estimated capacity available to meet these demands is critically dependent on end-inspiratory lung volume, the changes in lung volume during exercise were measured in three of the subjects using He dilution. End-expiratory volume was 52.3 +/- 2.42% TLC at rest and 38.5 +/- 0.79% TLC at maximum exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Respiratory muscles and dyspnea.

This article reviews the classical basis on which dyspnea is identified and quantified. The sensation or sensations of discomfort experienced during breathing are then viewed using a background of sensory physiology. Exploiting psychophysical techniques, the origin of the sensation of discomfort is viewed within the constraints of the presently-known sensory structures. The contribution of these sensory structures to the quality and quantity of discomfort is suggested, indicating the central role played by the respiratory muscles.

Dyspnea↗
PubMed1987

Effect of thoracoabdominal breathing patterns on inspiratory effort sensation.

The respiratory sensations evoked by added inspiratory loads are currently thought to be largely mediated by the activity of the inspiratory muscles. Because of the differences in proprioceptors and in afferent and efferent innervations among the inspiratory muscles, we hypothesized that the sensation evoked by a given load would be different when the motor command is directed mainly to rib cage muscles or mainly to the diaphragm. To test this hypothesis, we studied six normal subjects breathing against several inspiratory resistances while emphasizing the use of rib cage muscles, or the diaphragm, or a combination of both. At the end of 10 loaded breaths the subjects rated the perceived magnitude of inspiratory effort on a Borg scale. A linear and unique relationship (r = 0.96 +/- 0.02; P less than 0.001) was found between the sensation and esophageal pressure (Pes) in the three thoracoabdominal breathing patterns. We conclude that the level of Pes, whether generated mainly by the rib cage muscles or the diaphragm, is the main variable related to the sensation of inspiratory effort under external inspiratory loads.

Abdomen↗
PubMed1986

Breathlessness during exercise with and without resistive loading.

The purpose of this study was to quantify the intensity of breathlessness associated with exercise and respiratory resistive loading, with the specific purpose of isolating the quantitative contributions of inspiratory pressure, length, velocity, and frequency of inspiratory muscle shortening and duty cycle to breathlessness. The intensity of inspiratory pressure was quantified by measurement of estimated esophageal pressure (Pes = pressure at the mouth plus lung pressure), the extent of shortening by tidal volume (VT), and the velocity of shortening by inspiratory flow rate (VI). Six normal subjects underwent five incremental (100 kpm X min-1 X min-1) exercise tests on a cycle ergometer to maximum capacity. The first and last test were unloaded and the intervening tests were performed with external added resistances of 33, 57, and 73 cm H2O X l-1 X s in random order. The resistances were selected to provide a range of pressures, tidal volumes, flow rates, and patterns of breathing. At rest and at the end of each minute during exercise the subjects estimated the intensity of breathlessness (psi) by selecting a number ranging from 0 to 10 (Borg rating scale, 0 indicating no appreciable breathlessness and 10 the maximum tolerable sensation). Breathlessness was significantly and independently related to Pes (P less than 0.0001), VI (P less than 0.0001), frequency of breathing (fb) (P less than 0.01), and duty cycle [ratio of inspiratory duration to total breath duration (TI/TT)] (P less than 0.01): psi = 0.11 Pes + 0.61 VI + 1.99 TI/TT + 0.04 fb - 2.60 (r = 0.83). The results suggest that peak pressure (tension), VI (velocity of inspiratory muscle shortening), TI/TT, and fb contribute independently and collectively to breathlessness. The perception of respiratory muscle effort is ideally suited to subserve this sensation. The neurophysiological mechanism purported is a conscious awareness of the intensity of the outgoing motor command by means of corollary discharge within the central nervous system.

Adult↗