We found modulations in the time-course of breathing during rhythmic abduction-adduction movements in shoulder and hip joints which can be interpreted as phenomena of central coordination in the sense of v. Holst. They occurred in more than 75% of the recorded breaths. The strength of this coordination depends on number and kind of limbs moving rhythmically and on the use of an acoustic trigger signal ("Zeitgeber") for the limb rhythm as well. Our findings indicate that reactions of the respiratory apparatus cannot be regarded only in connection with its homeostatic function and with mechanical influences. Breathing control appears integrated in the whole organism's "motor control system". Therefore, an influence of breathing movements on other motor processes is possible as well. Coordination leads to a stable temporal order between breathing and additional movements. Its possible advantage could be an energetic economization as may be concluded from analogous phenomena in coupled non-linear oscillators.

Arm and leg movements are known to produce temporal pattern changes of breathing. This can be interpreted as coordination, as defined by von Holst (1939). The aim of the present study was to find whether breathing exerts an influence in a reverse direction on a nonrespiratory movement as well. A pursuit tracking test was used, and test individuals (N = 19) were instructed to track a visually presented step function by flexion or extension of their right index finger. Velocity and precision of the step responses proved to be dependent on their relation to the breathing time course; the differences between inspiratory and expiratory responses were smaller than those within each half-cycle. The movements were performed more rapidly and more precisely in about the middle of each half-cycle than immediately after the respiratory phase transition or during the second half of each inspiration or expiration. Discontinuous short-lasting motor actions exerted a coordinative influence on respiration comparablewith that of periodical events: Breaths coinciding with step responses were shortened, preferably when the preset step was given early in the inspiration. It was hypothesized that the reciprocal effect between both motor actions changes periodically. In the first part of each respiratory half-cycle, the respiratory rhythm exerts only a weak influence on additional movements, but it can be altered easily by simultaneous motor processes. Toward the respiratory phase-switching, the respiratory rhythm behaves more stably against coordinative influences and becomes capable of impairing an additional movement.

The coordination between breathing and other motor activities usually implies that the respiratory rhythm has become entrained by the rhythm of the simultaneous movement. Our hypothesis was that by increasing the respiratory drive, e.g. by hypercapnia, we would be able to reduce the subordination of breathing to other movements and, on the other hand, enhance effects of breathing on those movements. We investigated interactions between breathing and finger flexion movements in a visually controlled step-tracking procedure which allowed us to distinguish the mutual effects and to detect the dependence of these effects on the phase-relationship between breathing and movement. In contrast to our hypothesis, we found no large increase of the respiratory influences on finger movements during hypercapnia. A noteworthy difference to normocapnia was a shortening of the finger flexion time during the final stage of expiration which was associated with an increased frequency of coincidence between the end of flexion time and the transition from expiration to inspiration. On the other hand, the response of breathing to the finger movement increased when the tracking signal was presented at the beginning of inspiration. The results of the study disproved our hypothesis and demonstrated that, during hypercapnia, breathing can be even more susceptible to influences originating from motor control. Thus, they are in agreement with the findings of a previous study that the coordination between breathing and rhythmic limb movements becomes closer during hypercapnia.

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At Leipzig University, preoperative pulmonary function testing has been performed for about 3 years in order to detect and classify patients at high pulmonary risk. During the postoperative period, the risk of developing pulmonary complications is particularly high due to factors influencing respiratory mechanics such as the supine position, pain, residual effects of narcotic drugs, etc. It has often been emphasised that an underlying ventilatory disturbance such as obstructive lung disease or smoking may enhance the postoperative pulmonary risk, although the extent of the influence of preoperative pulmonary diseases on the postoperative complication rate is still controversial. The prediction of postoperative lung function from preoperative spirometric values is complicated by factors such as patient cooperation, pulmonary complications secondary to aspiration, infection, peritonitis, etc., and by differing and therefore non-comparable postoperative care. For this reason, the criteria for assessing pulmonary risk vary widely. METHODS. We examined 339 patients (mean age 59.3 years) preoperatively by quiet and forced spirometry; in most cases we also measured airway resistance and functional residual capacity. We estimated the postoperative lung function using the quadrant scheme of Miller and compared this risk class with our spirometric diagnosis and the postoperative clinical course. RESULTS. According to our results, Miller's classification seems inadequately differentiated for patients with mild to moderate ventilatory disturbances. A relatively high percentage of these patients were considered to have normal postoperative lung function. Some patients with severely diminished pulmonary function were classified as having sufficient postoperative lung function. The number and severity of pulmonary complications also corresponded better with the spirometric diagnosis, which was made using all spirometric parameters and not only vital capacity (VC) and 1-s forced expiratory volume (FEV1). We found that the percentage of primary respiratory complications increased with deterioration of the preoperative spirometric values. To provide a prognostic model combining both the advantages of using only a few parameters (FEV1, VC) and appropriate risk assessment, we propose a modification of the Miller scheme consisting of five risk classes. The analysis of the respiratory therapy regimen was unsatisfactory because of discrepancies between the predicted pulmonary risk, the use of respiratory therapy, and the occurrence of pulmonary complications. CONCLUSIONS. For minimising perioperative pulmonary complications, respiratory care (prophylaxis and therapy) adequate for the functional risk of the patient is necessary. We assume that intensive pre- and postoperative respiratory care and therapy in patients with underlying reductions in ventilatory function can help to avoid or reduce respiratory complications. The modification of Miller's scheme proposed after evaluating the postoperative course of our patients provides a diff...