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Physische Belastungsreaktionen bei fahrradergometrischen Untersuchungen in sitzender- und halbliegender Position
Abstract
Zusammenfassung
Fahrradergometrische Untersuchungen werden zur Therapiesteuerung und zur Feststellung der körperlichen Leistungsfähigkeit und Belastbarkeit bei sportmedizinischen Untersuchungen eingesetzt. Dabei haben sich die sitzende und halbliegende Fahrradergometrie etabliert. Zur Übertragbarkeit der durch die unterschiedlichen Belastungssituationen ermittelten Ergebnisse gibt es nur wenige Veröffentlichungen, die zudem ohne eindeutige Aussagen sind. Ziel der Studie ist es, durch eine Einzelfalluntersuchung exemplarisch die Vergleichbarkeit der beiden Belastungssituationen anhand von spirometrischen und kardiozirkulatorischen Parametern zu ermitteln. Die vorliegenden Ergebnisse legen die Vermutung nahe, dass eine Limitierung der Übertragbarkeit von spiroergometrisch gewonnenen Belastbarkeitswerten auf die jeweils adäquate Sitz- bzw. Halbliegeposition im Ergometertraining nicht angebracht scheint.
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››The efficiency η of energy conversion is defined as the ratio
between muscular power and metabolic energy expenditure. Following
definitions are used: ηgross (muscular power/total energy
expenditure), ηnet (muscular power/(total energy expenditure–
resting energy expenditure)), ηwork (muscular power/(total energy
expenditure–idling energy expenditure)), ηdelta (Δmuscular
power/Δenergy expenditure). ηnet of isolated muscles amounts
to 30%. Because of supporting functions, lower values result in
vivo during positive exercise. During negative exercise the body
often stores energy (elastic, potential, kinetic) which markedly
improves η if reused.
››Measurements are performed using ergometers (cycle ergometers,
treadmill etc.) and indirect calorimetry (V˙O2 and V˙CO2).
Determination of both gases is essential, because varying proportions
of fat and carbohydrate oxidation influence energy
turnover. For intense exercise, the anaerobic energy yield is
calculated from oxygen deficit or blood lactate. Measurements
have to be standardized, because movement frequency and power
influence η. For comparisons ηnet is preferable which little
depends on power.
››During sports, values vary between 1 (arching) and 50% (running).
Measurement of energy expenditure per m distance and
kg of body mass is also applicable for efficiency estimation. The
efficiency of complex movements can be improved by practicing,
since optimized coordination reduces energy need. Aging and
fatigue are therefore also influential. The mitochondrial function
is probably not trainable. Clear sex differences have not been
observed. An improvement of efficiency in hypoxia is improbable;
a relative increase of carbohydrate metabolism reduces the need
for oxygen. An increase of efficiency by nitrate consumption is
under discussion.
Three recent advances in assessment of routine lung function are reviewed. In both normal subjects and patients with obstructive lung disease, the flows during the forced vital capacity (FVC) manoeuvre depend significantly on the pattern of the preceding inspiratory manoeuvre. Accordingly, the latter should be standardized in clinical and epidemiological studies. Although the nature of this phenomenon is not fully understood, stress relaxation of lung tissues probably plays the primary role. The negative expiratory pressure technique provides a simple and reliable tool for detecting expiratory flow limitation both at rest and during exercise. The method does not require body plethysmography or the patient’s cooperation and coordination, and can be applied in any desired body posture. A simple method for monitoring FVC performance has been developed. It allows detection of flow limitation during the FVC manoeuvre.
Purpose:
The influence of posture on breathing effort in patients with difficult weaning is unknown. We hypothesized that posture could modulate the breathing effort in difficult-to-wean patients.
Methods:
A prospective, crossover, physiologic study was performed in 24 intubated patients breathing with pressure support who had already failed a spontaneous breathing trial or an extubation episode. Their median duration of mechanical ventilation before measurements was 25 days. Breathing pattern, occlusion pressure (P (0.1)), intrinsic PEEP (PEEP(i)), and inspiratory muscle effort evaluated by the pressure-time product of the respiratory muscles and the work of breathing were measured during three postures: the seated position in bed (90°LD), simulating the position in a chair, the semi-seated (45°), and the supine (0°) positions consecutively applied in a random order. A comfort score was obtained in 17 cooperative patients. The influence of position on chest wall compliance was measured in another group of 11 sedated patients.
Results:
The 45° position was associated with the lowest levels of effort (p ≤ 0.01) and occlusion pressure (p < 0.05), and tended to be more often comfortable. Respiratory effort was the lowest at 45° in 18/24 patients. PEEP(i) and PEEP(i)-related work were slightly higher in the supine position (p ≤ 0.01), whereas respiratory effort, heart rate, and P (0.1) values were increased in the seated position (p < 0.05).
Conclusion:
A 45° position helps to unload the respiratory muscles, moderately reduces PEEP(i), and is often considered as comfortable. The semi-seated position may help the weaning process in ventilator-dependent patients.
A meta-analysis including 32 randomised controlled trials on the effects of inspiratory muscle training (IMT) in chronic obstructive pulmonary disease (COPD) patients was performed. Overall and subgroup analyses with respect to training modality (strength or endurance training, added to general exercise training) and patient characteristics were performed. Significant improvements were found in maximal inspiratory muscle strength ( P I,max ; +13 cmH 2 O), endurance time (+261 s), 6- or 12-min walking distance (+32 and +85 m respectively) and quality of life (+3.8 units). Dyspnoea was significantly reduced (Borg score -0.9 point; Transitional Dyspnoea Index +2.8 units). Endurance exercise capacity tended to improve, while no effects on maximal exercise capacity were found. Respiratory muscle endurance training revealed no significant effect on P I,max , functional exercise capacity and dyspnoea. IMT added to a general exercise programme improved P I,max significantly, while functional exercise capacity tended to increase in patients with inspiratory muscle weakness ( P I,max <60 cmH 2 O).
IMT improves inspiratory muscle strength and endurance, functional exercise capacity, dyspnoea and quality of life. Inspiratory muscle endurance training was shown to be less effective than respiratory muscle strength training. In patients with inspiratory muscle weakness, the addition of IMT to a general exercise training program improved P I,max and tended to improve exercise performance.
Chair-sitting may allow for more readily activated scalene, sternocleidomastoid, and parasternal intercostal muscles, and may raise and enlarge the upper thoracic cage, thereby allowing the thoracic cage to be more easily compressed.
To evaluate the effect of chair-sitting during exercise training on respiratory muscle function in mechanically ventilated patients.
We randomized 16 patients to a control group and 18 patients to a chair-sitting group. The patients in the chair-sitting group were transferred by 2 intensive care unit nurses from bed to armchair and rested for at least 30 min, based on the individual patient's tolerance. We measured heart rate, blood pressure, S(pO(2)), and respiratory rate. In the treatment group, before transferring the patient from bed to armchair, and 30 min after the completion of chair-sitting we measured respiratory muscle function variables, including the ratio of respiratory rate (f) to tidal volume (V(T)), S(pO(2)), maximum inspiratory pressure (P(Imax)) and maximum expiratory pressure (P(Emax)). In the control patients we took those same measurements while the patient was in semirecumbent position, before and after treatments, for at least 6 days or until the patient was discharged from the intensive care unit or died.
The 2 groups did not significantly differ in age, sex, or clinical outcomes. Respiratory rate, V(T), f/V(T), S(pO(2)), P(Imax), and P(Emax) were not significantly better in the chair-sitting group. The study period significantly improved respiratory rate, V(T), P(Imax), and P(Emax) (all P < .001), but not f/V(T).
Six days of chair-sitting exercise training did not significantly improve respiratory muscle function in mechanically ventilated patients.
Wechselwirkungen zwischen Katecholaminen, β-Adrenozeptoren, akuter körperlicher Belastung und Training
- G Strobel