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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
PubMed2001

Is exercise tolerance limited by the heart or the lungs?

This 55-year-old man with known rheumatic mitral valve disease is modestly disabled achieving a VO2max of 72% and a maximal power output of 76% of the predicted normal. His capacity to exercise is limited by dyspnea due to a reduction in his capacity to breathe. Ipratropium bromide was initiated to maximize his expiratory flow and improve his ventilatory capacity. A trial of inhaled steroids produced no improvement. He was referred for rehabilitation and smoking cessation. A decision was made to continue surveillance, postponing mitral valve replacement.

Blood↗
PubMed2000

Symptom perception during acute bronchoconstriction.

The hypothesis underlying the present study was that some of the variability in symptom intensity seen during acute bronchoconstriction may result from varying intensities of several stimuli yielding several sensations that can be identified by specific descriptive expressions (symptoms). A total of 232 subjects inhaled methacholine in doubling concentrations to a 20% decrease in FEV(1), or 64 mg/ml. The study identified the prevalence of dyspnea, nonspecific discomfort associated with the act of breathing, and 10 specific symptom expressions. Each symptom intensity was rated in Borg scale units. The contribution of the specific symptoms to the intensity of dyspnea is illustrated in the following equation (r = 0. 84): Dyspnea = 0.44 + 0.19 Difficult breathing + 0.41 Chest tightness + 0.20 Breathlessness + 0.14 Labored breathing + 0.11 Chest pain. Dyspnea was more intense with broncho-constriction, baseline pulmonary impairment, weight, and sex (being female). Dyspnea was less intense with age (being older) and as airway responsiveness to methacholine increased (p < 0.05 for all factors). Chest tightness and chest pain were at polar extremes on the discrimination scale, i.e., easily discriminated; chest tightness, difficult and labored breathing were not easily discriminated.

Adult↗
PubMed1999

Is there a conflict between minimizing effort and energy expenditure with increasing velocities of muscle contraction in humans?

1. The present study examined the possibility that minimizing effort conflicts with minimizing energy expenditure at different velocities of muscle contraction during cycling. 2. Six normal subjects underwent incremental exercise on an electrically stabilized cycle ergometer. Power output increased by 45 W every 3 min to exhaustion at pedalling frequencies of 40, 60, 80 and 100 r.p.m. on separate days. Energy expenditure (oxygen uptake), leg effort and dyspnoea (Borg 0-10 scale) were measured in parallel at the end of each minute. 3. All six subjects completed 10 min of exercise achieving 180 W for all four pedalling frequencies. Two-way analysis of variance indicated that oxygen uptake (P < 0.0001), leg effort (P < 0.0001) and dyspnoea (P < 0.0001) increased with duration of exercise and power output; oxygen uptake (P < 0.0001) and leg effort (P < 0.05) were significantly different between pedalling frequencies; the interactions were not significant. Oxygen uptake was minimal at 60 r.p.m., and increased at both higher and lower pedalling frequencies. Both leg effort and dyspnoea were minimal at 80 r.p.m.; leg effort intensified at higher and lower pedalling frequencies; and dyspnoea was most intense at 100 r.p.m. 4. There was a conflict between minimization of energy expenditure and leg effort at power outputs less than 180 W. Minimizing effort occurred at the expense of an increase in energy expenditure.

Adult↗
PubMed1998

Metabolic and hemodynamic responses of lower limb during exercise in patients with COPD.

Premature lactic acidosis during exercise in patients with chronic obstructive pulmonary disease (COPD) may play a role in exercise intolerance. In this study, we evaluated whether the early exercise-induced lactic acidosis in these individuals can be explained by changes in peripheral O2 delivery (O2). Measurements of leg blood flow by thermodilution and of arterial and femoral venous blood gases, pH, and lactate were obtained during a standard incremental exercise test to capacity in eight patients with severe COPD and in eight age-matched controls. No significant difference was found between the two groups in leg blood flow at rest or during exercise at the same power outputs. Blood lactate concentrations and lactate release from the lower limb were greater in COPD patients at all submaximal exercise levels (all P < 0.05). Leg D02 at a given power output was not significantly different between the two groups, and no significant correlation was found between this parameter and blood lactate concentrations. COPD patients had lower arterial and venous pH at submaximal exercise, and there was a significant positive correlation between venous pH at 40 W and the peak O2 uptake (r = 0.91, P < 0.0001). The correlation between venous pH and peak O2 uptake suggests that early muscle acidosis may be involved in early exercise termination in COPD patients. The early lactate release from the lower limb during exercise could not be accounted for by changes in peripheral O2. The present results point to skeletal muscle dysfunction as being responsible for the early onset of lactic acidosis in COPD.

Acidosis, Lactic↗
PubMed1996

Quantification of intensity of sensations during muscular work by normal subjects.

Eleven subjects performed a series of 30-s work bouts on a cycle ergometer at power outputs ranging from 20-120% of the work capacity (Wcap) achieved during an incremental cycle to exhaustion and estimated the intensity of several sensations (leg effort, muscle tension, muscle discomfort, muscle pain, and breathing discomfort) by using Borg's category-ratio scale (range 0-10 units). Leg effort was perceived as "just noticeable" at 31 +/- 15% Wcap, muscle tension was just noticeable at 31 +/- 16% Wcap, muscle discomfort was just noticeable at 47 +/- 21% Wcap, breathing discomfort was just noticeable at 52 +/- 19% Wcap, and muscle pain was just noticeable at 58 +/- 33% Wcap. The intensity of all sensations increased in a positively accelerating manner with increases in power output (P < 0.001). Above 60% Wcap, the intensity of leg effort and muscle tension exceeded the intensity of muscle pain (P < 0.01), and above 100% Wcap the intensity of muscle discomfort also exceeded the intensity of muscle pain (P < 0.01). At 120% Wcap, leg effort, muscle tension, and muscle discomfort were rated between "severe" and "very severe" (6.1 +/- 2.2, 6.4 +/- 2.0, and 5.6 +/- 2.1 Borg units, respectively), whereas muscle pain and breathing discomfort were rated between "moderate" and "somewhat severe" (3.6 +/- 2.1 and 3.3 +/- 1.9 Borg units, respectively). These results suggest that subjects have a perception of muscle pain during muscular work that is distinct from perceptions of leg effort, muscle tension, and muscle discomfort.

Adult↗
PubMed1996

Symptom intensity and subjective limitation to exercise in patients with cardiorespiratory disorders.

The aim of the study was to compare (1) the intensity of leg effort and dyspnea during exercise and (2) subjective limitations to performance in normal subjects, patients receiving medication for cardiac disorders, patients with pulmonary impairment, patients with pulmonary impairment who were also receiving cardiac medications, patients experiencing chest pain during exercise, and patients who had a reduced exercise capacity but did not have pulmonary impairment and were not receiving cardiac medication. Five hundred seventy-eight subjects rated the intensity of leg effort, discomfort with breathing (dyspnea), and chest pain every minute (Borg scale) during an incremental exercise task (100 kpm/min each minute) to maximum work capacity on a cycle ergometer and following exercise indicated their subjective limitation by completing a simple questionnaire. Leg effort and dyspnea increased systematically with power output in a positively accelerating manner in all groups; both symptoms were significantly more intense in the impaired groups compared with the normal group at submaximal power outputs. In all groups, there was a significant relationship between symptom intensity at submaximal power outputs and the maximal power output achieved. Leg discomfort in combination with breathing discomfort was the predominant subjective limitation in all groups; chest pain in combination with leg and breathing discomfort was the major subjective limitation in individuals with angina. Activation of the sensory systems during exercise is accompanied by a perception of discomfort associated with the peripheral exercising muscles and discomfort with breathing; both discomfort associated with the exercising muscles and discomfort associated with breathing contribute to exercise limitation to a large degree in normal subjects and patients with cardiorespiratory diseases.

Angina Pectoris↗
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↗