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Biomedical subjects

S Waurick

Publications and source records attributed to S Waurick.

11 recordsLinked to original sources
PubMed2001

[Effect of surgical positioning and spinal anesthesia on lung function].

BACKGROUND: Various surgical positions, e.g., lithotomy, prone, or head-down positions influence respiratory mechanics. The aim of the present paper was to investigate whether particular surgical positions (lithotomy, lithotomy with head-down tilt, prone, prone with a roller placed under the abdomen) as well as spinal anaesthesia in lithotomy position impair the pulmonary function to a greater extent than supine position and whether they have to be considered as increasing the perioperative risk in elderly patients and patients with ventilatory disorders. METHODS: In two separate experimental series, we examined a) the influence of the surgical positions on the pulmonary function in 45 subjects (25 without and 20 with ventilatory disorders) and b) the effects of spinal anaesthesia in 25 urologic patients (9 without and 16 with ventilatory disorders). Static and dynamic lung function parameters were determined. Under spinal anaesthesia, the arterial O2 saturation and the end-expiratory partial pressure of CO2 were measured additionally. RESULTS: The most pronounced lung function decrease occurred with the transition from seated to supine position. Lithotomy and prone positions impaired the respiratory function only slightly. In elderly persons and in patients with ventilatory disorders, the spirometric changes tended to be stronger than in young persons, but were not considered to increase the perioperative pulmonary risk. A combination of lithotomy position and spinal anaesthesia did likewise not remarkably impair the respiratory function. CONCLUSIONS: Lithotomy and prone positions as well as spinal anaesthesia are not considered to be an additional risk factor for pulmonary function.

Adult↗
PubMed1999

Phase-dependence of breathing and finger tracking movements during normocapnia and hypercapnia.

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.

Adult↗
PubMed1996

Breathing--homeostatic function and voluntary motor activity.

In a magnitude production test, subjects of both sexes rated their breath depth under different conditions. In the first group, 50 subjects were examined at rest in the supine position and breathing spontaneously or assisted by a respirator. The second group, consisting of 33 subjects, was tested in the sitting position at rest and during mild bicycle exercise (females 35 W, males 40 W). Subjectively quantified breath depths and corresponding tidal volumes were compared and their relations were described by Stevens power function. The assessment of breath depth in spontaneous breathing at rest was remarkably precise (mean Stevens exponent 0.94 +/- 0.02). During assisted ventilation, rating was less accurate and tended to underestimate breath depth. Noticeable under both conditions was a tendency to overestimate voluntary tidal volume reductions. This was more pronounced in young (up to 35 years) women than in men or elderly women. During exercise, the subjects (men and women) overestimated both increases and reductions of tidal volume. Each voluntary tidal volume modification was accompanied immediately by involuntary changes of inspiration and expiration times, thus, partially compensating disturbances of ventilation. In addition, voluntarily reduced tidal volumes were quantitatively compensated within the first breath subsequent to the voluntary manoeuver. We conclude that breath depth sensation is more strongly related to proprioceptive signals than to visceroceptive signals and is influenced by the autonomous respiratory drive. Furthermore, proprioception is assumed to participate in the control of the autonomous respiratory drive.

Adult↗
PubMed1994

[The prognostic relevance of preoperative pulmonary function tests].

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 differentiated prognostic model that allows the establishment of an appropriate and economical therapeutic regimen of perioperative pulmonary care.

Adult↗
PubMed1990

[Effect of central coordination in the sense of v. Holst on the control of breathing and limb movements in humans].

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.

Hip Joint↗
PubMed1984

[Regulation of respiration in assisted ventilation].

Based on knowledge of the control of external respiration, the physiological reactions are discussed which should be evoked proprioceptively and chemoreceptively by an assisting respirator's disturbances of spontaneous breathing movements. The following possible states are discriminated: 1. "no adaption": the respiratory motor system does not remain passive during the machine's stroke; 2. "passive adaption": the respiratory motor system remains passive during the respirator's stroke; to changes of the blood gas-status, only the breathing frequency responds, but in just the same manner as during spontaneous ventilation; 3. "active adaption": the ventilatory motor apparatus remains passive during the respirator's operation; changes of the blood gases are responded to by the breathing frequency only, but in a manner different to spontaneous breathing and which compensates for the invariability of the fixed stroke-volume. - Related to these 3 states, consequences concerning the efficiency of chemical respiratory control can be derived which should reveal themselves during experimental manipulation of the blood gas partial pressures. Accordingly, the CO2-response curves of minute ventilation, breathing frequency and tidal-volume generated in 9 healthy, awake and cooperative subjects during spontaneous breathing and assisted (stroke-volume controlled) respiration with gas mixtures of 0, 3 and 6% CO2 were investigated and compared. (In each subject assisted ventilation with 2 or 3 different stroke-volumes was performed. The smallest stroke-volume equalled the medium tidal-volume of spontaneous ventilation. Every stroke-volume produced its particular CO2-response curve). Hence it follows that with assisted ventilation, using a stroke-volume larger than the spontaneous tidal-volume, the subjects maintain a state between "passive" and "active adaption".(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Dioxide↗
PubMed1975

[Contribution to the structure of respiration control].

A structure is reported which describes the relatively free availability of the motor respiratory apparatus to non-respiratory functions due to the presence of a respiratory control both on homeostatic and motor levels. It is assumed that, at the motor level, a competition develops of two or more regulators for the same parameter (e.g. the activity of neurons that can be claimed both by respiratory and by a second skeletal motor process). The compromise being reached is dependent on the amplification in the competing circuits. The correlation between the metabolic value and that of the respiration-time volume may be accomplished by the fact that amplification in the respiratory-motor circuit is rendered variable as a result of its interconnection with the chemical respiratory control. The high time constant of the latter allows for the instantaneous free availability of the motor respiratory apparatus to non-respiratory functions. The postulated structure offers better interpretations for the actual respiration behaviour than those considering the respiratory function alone.

Homeostasis↗