PubMed Health⌕ Search

Biomedical subjects

K Axen

Publications and source records attributed to K Axen.

At least 19 recordsLinked to original sources
PubMed1996

Mechanical unweighting effects on treadmill exercise and pain in elderly people with osteoarthritis of the knee.

BACKGROUND AND PURPOSE: People with osteoarthritis (OA) of the knee who have pain generally exhibit decreased activity and physical deconditioning. This study investigated the effects of mechanical unweighting on knee pain and exercise responses in people with OA of the knee who have pain. SUBJECTS: Four men and 23 women, with a mean age of 67.9 years (SD = 11.3, range = 50-88) and having a 12-year average duration of knee OA, participated. METHODS: A mechanical unloading device enabled subjects to perform a modified Naughton treadmill exercise test at 0%, 20%, and 40% of body weight support (BWS). Oxygen consumption (VO2), heart rate (HR), and perceived pain were measured during the last minute of each exercise stage. RESULTS: Mechanical unweighting at 20% and 40% BWS decreased the Vo2 and HR responses to treadmill exercise but did not decrease knee pain during walking in this sample. CONCLUSION AND DISCUSSION: These findings indicate that treadmill exercise accompanied by BWS permits recommended training intensities to be obtained in elderly people with OA, but may not provide pain relief in this group.

Aged↗
PubMed1995

Effect of distractive auditory stimuli on exercise tolerance in patients with COPD.

We tested the hypothesis that a distractive stimulus, such as music, introduced during exercise can reduce perception of respiratory effort at any given level of exercise, whereas sensory deprivation increases effort perception. Thirty-six patients with moderate COPD participated in four sessions of symptom-limited exercise. The first session familiarized the subject with the protocol. The other sessions were performed under partial visual isolation while listening to music (M), or to grey noise (GN), or in silence (SIL), presented in randomized order. Subjects graded their respiratory effort using the Borg rating of perceived exertion (RPE) scale. Total exercise time (EXT) and external work (WT) were objective indices of exercise tolerance. EXT was 22% longer with M than with either GN or SIL (p < 0.001), and WT was 44% and 53% greater with M than with GN or SIL, respectively (p < 0.001). These increases occurred at a heart rate that was only a few beats higher than during GN or SIL (104 +/- 3 bpm for M and 101 +/- 3 bpm for GN and SIL), a minimal difference that was statistically significant (p < 0.001). At every level of exercise, perceived exertion with M was lower than for either GN or SIL (p < 0.001). Although the respective RPE was higher for SIL than for GN (p < 0.01) at every level of exercise, WT and EXT were no different. These data indicate that perceived effort can be significantly influenced by external factors. This in turn suggests that the use of distractive stimuli during exercise training programs with patients with COPD may significantly decrease perceived symptoms of respiratory discomfort, thus allowing the patient to exercise to a higher intensity, and potentially achieving more effective exercise reconditioning training.

Acoustic Stimulation↗
PubMed1994

Discrimination of transiently applied mechanical loads: breathing vs. pulling.

Two groups of 24 subjects each attempted to discriminate between large elastic and resistive loads during 50 randomized presentations of each load. Breathers inspired from the loads through a J valve, whereas pullers reciprocally stroked the plunger of a 2-liter syringe connected to the J valve. A range of load durations was obtained in each subject by prematurely unloading approximately one-half of the trials at graded times from their onset. Breathers produced random discrimination scores [50.8 +/- 2.5% (SE) correct] when loaded inspirations were shorter than unloaded inspirations [trials in which both loads induced equal airway pressure (and probably respiratory muscle tension) waveforms] and nonrandom discrimination scores (65.7 +/- 2.8% correct) when loaded inspirations were longer than unloaded inspirations (trials in which both loads induced different waveforms). In contrast, pullers produced nonrandom discrimination scores (62.2 +/- 2.9% correct) when loaded airflow durations were shorter than unloaded inspirations [trials in which both loads induced equal line pressure (and therefore limb muscle tension) waveforms]. Supplemental audio feedback related to instantaneous airflow (an expression of movement) improved load perception in breathers (to 64.2 +/- 3.0% correct; P < 0.01), indicating that airflow feedback introduced load-specific information that was lacking during breathing but redundant during pulling. In support of this hypothesis, airflow feedback by itself enabled a third group of listeners to identify load type with equal accuracy as pullers but with greater accuracy than breathers. These findings suggest that 1) uniformed subjects rely heavily on feedback from airway pressure and/or muscle tension receptors to perceive added loads to breathing and 2) limb mechanoreceptors provide a more sensitive appreciation of movement than do respiratory mechanoreceptors.

Acoustic Stimulation↗
PubMed1993

Use of maximum expiratory flow-volume curve parameters in the assessment of exercise-induced bronchospasm.

Exercise-induced bronchospasm (EIB) is often inferred from the reduction after exercise in one arbitrarily selected value derived from the maximum expiratory flow-volume (MEFV) curve (eg, FEV1) on a single test; however, patients with symptoms of EIB not meeting these criteria may risk being undiagnosed. To assess the ability of repeated tests using additional MEFV parameters in identifying EIB-prone patients, we investigated the effects of exercise provocation on the MEFV curve on two separate occasions. Of 95 patients with symptoms of EIB, 61 had reproducible exercise-induced changes (< 10 percent intraresponse variation), falling into four patterns: 27 (44 percent) had significantly reduced VC and airflow throughout the MEFV curve; 18 (30 percent) had unchanged VC but decreased airflow throughout the curve; 11 (18 percent) had reduced airflow above 50 percent VC but not below 50 percent VC; and 5 (8 percent) had significant reductions in airflow only at 50 percent VC or below. Of the other 34 subjects, 18 had no apparent response, and 16 responded on only one occasion, making objective assessment of these patients' EIB equivocal. We conclude that for a given individual, failure to meet arbitrary criteria does not rule out EIB. Additionally, a more subjective approach that integrates, among other factors, all routine MEFV curve parameters taken from multiple tests with clinical symptoms and history provide a more accurate assessment of EIB.

Adolescent↗
PubMed1991

Effect of milk ingestion on pulmonary function in healthy and asthmatic subjects.

Since Maimonides, it has been common in folk medicine to proscribe milk for asthmatics because its putative stimulation of mucus production can exacerbate asthma symptoms. A literature review, however, failed to reveal any data supporting this notion. We, therefore, compared the effects of ingesting 16 oz. of whole milk (16 g lipid), skim milk (2 g lipid), and water (each on a separate day) on: (1) forced expiratory volume in 1 second (FEV1), (2) forced expiratory flow at 50% of vital capacity (V50), and (3) pulmonary diffusing capacity (DLCO) in 11 asthmatic and 10 nonasthmatic subjects. Measurements were taken at 30 minute intervals for 3 hours. The two milk types did not significantly change FEV1 or V50 in either group, indicating that the amount ingested did not change airway resistance sufficiently to alter airflow parameters. In the asthmatic group, however, DLCO decreased progressively over the 3 hours by 6.8 +/- 1.4% (mean +/- SE) per hour after whole milk (maximum reduction = 21 +/- 1.4%) but not after water or skim milk. In the nonasthmatic group, no significant effects were observed on DLCO after any of the liquids. These data suggest that milk lipids can disturb gas exchange in asthmatic patients.

Adult↗
PubMed1990

Complications after cardiac operations in patients with severe pulmonary impairment.

The postoperative courses of 39 patients with severe lung disease (31 with obstructive disease and 8 restrictive) who underwent a cardiac operation were retrospectively reviewed. The stay in the intensive care unit of the study group was 7.9 +/- 10.3 days (mean +/- standard deviation) compared with 2.4 +/- 3.9 days for the control group (100 patients with less impaired pulmonary function) (p less than 0.001). The study group also had a greater number of valve replacements than did the control group (p less than 0.01). Patients with obstructive disease had more respiratory complications than did patients with restrictive disease (p less than 0.05). There were 21 cases of atelectasis. Effusions were noted in 11 patients. Ten patients had bronchospasm. Bronchial secretions were a major problem in 6 patients. Pneumonia developed in 4 patients, and pneumothorax occurred in 3 others. The two in-hospital deaths were not directly related to pulmonary complications. Our findings indicate that (1) patients with severe lung impairment generally do well after a cardiac operation but have more postoperative pulmonary complications than patients with less impairment; (2) patients with restrictive pulmonary disease appear to fare better than those with obstructive disease; (3) pulmonary function tests can alert the clinician to the possible risk of postoperative complications, but they cannot, by themselves, be used to exclude patients from operation; and (4) patients with severe pulmonary impairment facing valve replacement are at greater risk of pulmonary complications than patients having other types of cardiac surgical intervention.

Bronchial Spasm↗
PubMed1990

Pentoxifylline improves pulmonary gas exchange.

Pentoxifylline is a xanthine derivative with hemorrheologic and vascular properties that may improve gas exchange in patients with chronic obstructive pulmonary disease (COPD). We tested this hypothesis in 12 patients with COPD (mean FEV1 = 40 percent predicted; mean DCO, 8.6 ml/min/mm Hg) randomly divided into a treatment and control group and six healthy volunteers. Following establishment of baseline DCO and maximum expiratory flow volume (MEFV) curve values, each subject in the treatment and healthy groups took 400 mg of pentoxifylline three times a day for 12 weeks. Weekly DCO and MEFV curves were measured before treadmill exercise in both COPD groups and before and after exercise in the healthy group. The MEFV curve parameters from the final three weeks of therapy did not differ significantly from baseline values. During this time, however, the treatment COPD group's resting DCO rose by 8.2 +/- 2.4 percent over baseline level (p less than 0.01). Treadmill walk time increased from 17.7 +/- 2.9 minutes to 23.2 +/- 2.9 minutes (p less than 0.02). This was accompanied by improved exercise oxygen saturation measured by oximetry (SoxiO2). Premedication SoxiO2 fell from 92.8 +/- 1.2 percent to 88.6 +/- 2.5 percent during exercise, and from 94.4 +/- 1.1 percent to only 91.8 +/- 1.0 percent after 12 weeks of medication (p less than 0.05). No such improvement was noted in the control COPD group. Although the healthy group's resting SoxiO2 and DCO did not change during treatment, their exercise DCO increased significantly from 36.3 +/- 3.1 ml/min/mm Hg to 41.8 +/- 3.5 ml/min/mm Hg (p less than 0.001). These data demonstrate that pentoxifylline improves gas exchange, possibly by increasing cardiac output, and/or by raising mixed venous PO2, and/or by improving blood flow to underperfused alveoli.

Adult↗
PubMed1989

Aortic arch anomaly presenting as exercise-induced asthma.

We present the case of a young woman with a right aortic arch who first became symptomatic when she began a vigorous exercise program. Her symptoms were very suggestive of exercise-induced bronchospasm. Her flow-volume curves, however, showed evidence of variable intrathoracic large airways obstruction. A magnetic resonance imaging scan confirmed the presence of severe tracheal narrowing caused by her right aortic arch.

Adult↗
PubMed1989

Aerobic training effects of electrically induced lower extremity exercises in spinal cord injured people.

Eleven people with spinal cord injury (SCI) (C4-T6) participated in a program of functional electric stimulation (FES) of their paralyzed leg muscles using the REGYS I system. Individualized protocols consisted of an initial phase of weight lifting, an intermediate phase of ergometer pedalling against 0 Kilopond (kp) alternated with 1/8kp for six two-minute runs separated by two-minute rest periods, and a final phase of 36 sessions of continuous ergometer pedalling against variable resistance. A metabolic analyzer measured exercise stress test parameters before and after each phase while subjects pedalled against incremented resistance. Peak oxygen consumption and total stress test time increased markedly. The respiratory exchange ratio (R=VCO2/VO2) at termination, however, did not differ from unity at any phase, indicating that fatigue (defined as a failure to maintain a pedalling frequency of 35 rpm) occurred when the anaerobic threshold was reached, and that FES exercise can increase the aerobic capacity of persons with SCI. The initial velocity of quadriceps shortening (derived from patellar tendon displacements) also decreased in five of eight subjects tested, suggesting corresponding increases in quadriceps twitch time. Since muscle inactivity converts slow-twitch to fast-twitch fibers, our subjects' increased muscle endurance accompanied by decreased muscle-shortening velocity were compatible with a disproportionate increase in the function of slow-twitch fibers relative to fast-twitch fibers. Although these findings demonstrate that lower extremity FES exercises can safely achieve significant aerobic training effects in patients with SCI, the peak levels of cardiorespiratory performance were similar to those reported for quadriplegic people performing maximal voluntary upper extremity exercises.

Adult↗
PubMed1988

Respiratory load compensation in neuromuscular disorders.

First-breath ventilatory responses to graded elastic (delta E) and resistive (delta R) loads from 10 people with spinal muscular atrophy (SMA), 15 people with Duchenne muscular dystrophy (DMD), and 80 able-bodied people were compared. The SMA and DMD groups produced equal tidal volume, respiratory frequency, inspiratory duration (TI), expiratory duration, mean inspiratory airflow, and duty cycle responses to both delta E and delta R. Thus SMA (primarily a motoneuron disorder) and DMD (primarily a muscle disorder) have the same net effect on loaded breathing responses. The SMA and DMD groups failed to duplicate the normal group's short expirations during delta E, long inspirations during delta R, and thus, extended duty cycles during both delta E and delta R. The deficit in load compensation therefore was due to impaired regulation of respiratory timing (reflecting neural mechanisms) but not airflow defense (reflecting mechanical and neural mechanisms). One-fifth of the normal but none of the SMA or DMD subjects actively generated an "optimal" TI response (defined theoretically as TI greater than 160% control during large delta R and TI less than 75% control during large delta E). This lack of optimal responses, which is the same abnormality exhibited by quadriplegic people, suggests that SMA and DMD also impair human ability to discriminate between large delta R and delta E. These findings support the hypothesis that neuromuscular disorders can lead to disturbances in respiratory perception.

Adult↗
PubMed1988

Changes in serum K+ in healthy and in asthmatic subjects during exercise.

Adrenergic mechanisms modulate exercise-induced changes in blood serum K+ concentration ([K+]). Impairment of these same mechanisms may be associated with bronchial hyper-reactivity. If this is accurate, asthmatic subjects should show disturbed K+ regulation during exercise. We measured [K+] and FEV1 in 13 healthy control and in 13 asthmatic subjects pre-exercise, at peak exercise (within 1 min of stopping exercise), and 10 min postexercise. This was done on 2 separate days, one with and one without bronchodilator (BD) pretreatment. Both groups were equally fit, exercising to the same O2 consumption and heart rate. Resting [K+] was normal for both groups (two-day averages were 4.00 +/- 0.07 and 4.09 +/- 0.07 mmol/L, mean +/- SEM, in control and asthmatic subjects, respectively). Without BD pretreatment, at peak exercise, [K+] in control subjects rose by 0.56 +/- 0.08 compared with 0.96 +/- 0.09 in asthmatics (p less than 0.01). After exercise, [K+] returned to baseline (4.12 +/- 0.08) in control subjects but remained elevated in asthmatics (4.60 +/- 0.12, p less than 0.01). Although FEV1 was unchanged in control subjects, in asthmatics it fell after exercise (p less than 0.01). With BD pretreatment: peak exercise [K+] increased by 0.55 +/- 0.09 in control subjects, and by 0.49 +/- 0.01 in asthmatics (p less than 0.01). By 10 min postexercise, it returned to baseline in both groups (4.15 +/- 0.11 for control subjects and 4.32 +/- 0.07 for asthmatics). The asthma group's fall in FEV1 was also abolished. These data indicate that postexercise K+ remains elevated in asthmatics, supporting the suggestion that their adrenergic function is impaired.

Adult↗
PubMed1987

Respiratory load-compensating mechanisms in muscular dystrophy.

First-breath ventilatory responses to graded elastic and resistive loads were obtained from 15 people with Duchenne muscular dystrophy (DMD), 5 people with facioscapulohumeral MD (FSH), 3 people with Becker MD, and 3 people with limb-girdle MD. For each load tidal volumes from different individuals ranged from relatively small to comparatively large values, indicating a correspondingly wide range of end-inspiratory efforts; strong tidal volume defenders generally employed longer inspirations and higher mean inspiratory airflows than did weak tidal volume defenders; and individual frequency responses were mediated by changes in inspiratory and/or expiratory timing. Thus the loaded breathing responses of people with MD are qualitatively the same as those of quadriplegic and able-bodied people. Quantitatively, however, the DMD group generated considerably larger tidal volumes than did the FSH group during both elastic and resistive loading. These larger tidal volumes were achieved by both longer inspirations (a neurally mediated phenomenon) and higher mean inspiratory airflows (a mechanically and/or neurally mediated phenomenon). These findings, which could not be attributed to differences in respiratory motor function, suggest that there are differences between the respiratory sensory and/or central functions in the Duchenne and facioscapulohumeral types of MD.

Biomechanical Phenomena↗
PubMed1987

Effect of aerobic training on forced expiratory airflow in exercising asthmatic humans.

Pulmonary function after exercise was evaluated in 22 asthmatic subjects before and after a 36-session training sequence of aerobic exercise. Training did not change pulmonary function values, except for a small increase in maximal voluntary ventilation (P less than 0.02), which was attributed to respiratory muscle training. After aerobic training, both external work at a given heart rate and peak O2 consumption increased by 30 and 15%, respectively. At the same minute ventilation (VE), immediate postexercise forced expiratory airflow was higher after training (P less than 0.02), and reduction in forced expiratory airflow during the first 9 min postexercise was less after training (P less than 0.01). The posttraining airflow response to the pretraining work load was, as expected, less than the pretraining response (P less than 0.02). Although the difference in maximal-to-minimal airflow at the same VE was similar before and after training, the airflow increase accounted for 50% of the response after training compared with 16% of the pretraining response. Furthermore the strong negative correlation (P less than 0.01) between maximal and minimal airflow both pre- and posttraining indicates that exercise-induced bronchospasm (EIB) severity is, in part, determined by the degree of exercise-induced bronchodilation. We conclude that aerobic training significantly increases exercise-induced bronchodilation and diminishes EIB.

Aerobiosis↗
PubMed1986

Treadmill exercise training in chronic obstructive pulmonary disease.

Eight men and six women with severe chronic obstructive pulmonary disease (COPD) performed a pulmonary function test and a treadmill exercise stress test before and after an individualized training program, which nominally consisted of three 20-minute sessions of treadmill exercise per week for five consecutive weeks. Training sessions were terminated before 20 minutes if there were subjective complaints, or if the subject's heart rate reached 80% of the maximum heart rate observed during the pretraining stress test. This program failed to improve any of the pulmonary function test parameters (lung volumes, airflows, maximum voluntary ventilation, and resting levels of blood gases) and failed to improve most exercise stress test parameters (maximum oxygen consumption and carbon dioxide production, respiratory exchange ratio, and heart rate at termination of exercise). This program, however, did increase the group's average stress test time from 9.0-13.7 minutes (p less than 0.001) and increased the total external work (calculated from the sum of its vertical and horizontal components) from 3.5-6.8kcal (p less than 0.01). Eight of the 11 subjects who initially received 2L/min of 100% oxygen, via a nasal cannula, to alleviate dyspnea and to promote endurance were completely weaned from supplemental oxygen by the end of the training program. These findings demonstrate that a treadmill exercise program based on stress test data can increase the efficiency (external work per unit of oxygen consumed) and thus, the exercise tolerance, of persons with severe COPD.

Aged↗
PubMed1986

Reduced hyperpnea-induced bronchospasm following repeated cold air challenge.

This study assessed reduction in expiratory function in 12 asthmatic subjects both after 5 min of cold air provocation (CAP) with dry air conditioned to approximately 0 degrees C and after exercise (to 85% of predicted maximum heart rate) while breathing ambient room air (approximately 21 degrees C and 40% relative humidity). These assessments were done both before and after the following training protocol. Three 5-min periods of isocapnic cold air hyperpnea separated by 5-min rest periods were performed breathing 0 degrees to -10 degrees C air, for 36 sessions over 12 wk. As expected, pretraining expiratory function was significantly reduced (P less than 0.001) after both CAP and exercise. The posttraining reduction in expiratory function after CAP and exercise, however, was significantly less pronounced (largest P less than 0.05). These data support our hypothesis that repeated bouts of cold air challenge result in airway acclimatization to cold air and consequent decrease in exercise-induced bronchospasm. Acclimatization may result directly either by habituation of the airways or by vasodilation leading to increased bronchial blood flow and consequent reduced airway cooling. An unanticipated finding, though, is that repeated cold air challenge may also cause long-term inflammatory changes in the airways. A significant percentage of subjects experienced reduced base-line pulmonary function and overall exacerbation of asthma symptoms during the training period.

Acclimatization↗
PubMed1986

Effects of perceived musical rhythm on respiratory pattern.

The effects of rhythmic input on breath period (TT) under constant metabolic drive were assessed in 10 musically trained and 10 untrained subjects. They tapped to a metronome and then to four musical segments, each for 5 min. Ten of these subjects (5 from each group) also listened to the selections without tapping. TT, beat period (TB), and phase coupling (PC) were assessed during the last 20 breaths of each presentation. TT coefficient of variation decreased significantly (P less than 0.001) in all subjects (base line = 23%; listening = 15%; listening and tapping = 10%). Significant correlation between rhythm and TT, indicating relative entrainment, was found in half of the subjects (r greater than 0.45; P less than 0.01). Significant integer TT/TB ratio and PC, both indicating tight entrainment between rhythm and breathing, were observed in 12 subjects (though not consistently in each one). These data advance the following hypothesis: musical rhythm can be a zeitgeber (i.e., pacemaker), with its ability to entrain respiration dependent on the strength of its signal relative to spurious signals from the higher neural centers that introduce noise into the central pattern generator. Tapping reinforces the zeitgeber, increasing its signal-to-noise ratio and thereby promoting entrainment.

Auditory Perception↗
PubMed1985

Diaphragmatic function following cervical cord injury: neurally mediated improvement.

Vital capacity measurements from 36 people rendered quadriplegic by traumatic cervical cord injuries generally increased during the first ten months after injury, indicating spontaneous improvement in respiratory muscle function. Reasoning that a renewal of neural supply to the diaphragm would probably be accompanied by a parallel renewal of neural supply to other muscles having adjacent motor pathways, the present study compared vital capacity measurements with concomitant muscle function evaluations from 20 of these people. Qualitatively, increases in vital capacity were invariably accompanied by increases in the function of a group of muscles (primarily of the shoulder and upper arm) having some segmental innervation in common with the diaphragm (C3-C5) but were only sometimes accompanied by increases in the function of a group of muscles (primarily of the forearm and wrist) having segmental innervation below that of the diaphragm (C6-C8). These findings suggest that the spontaneous improvement in vital capacity observed in quadriplegic people is mediated in part by corresponding improvement in the neural supply to the diaphragm. Quantitatively, however, linear regression analysis indicated that neither the rate nor the absolute amount of improvement in vital capacity could be predicted with any reliability from pulmonary function tests, neurologic examinations, or muscle function evaluations performed in the early stage of recovery.

Adolescent↗