Two methods for measuring respiratory mechanics by forced oscillations were compared, one using a frequency spectrum of 2–32 Hz produced by a pseudorandom noise generator (PRN), the other (Siregnost FD 5) a constant frequency of 10 Hz. In normals and patients with various lung diseases real part of impedance, Re, and phase angle, ψ, determined at 10 Hz with the two devices correlated well; however, Re measured by Siregnost FD 5 was always higher when compared to PRN. In patients with airway obstruction frequency dependence of resistance and reactance could be shown to be related to the severity of the disease. This important information cannot be obtained by Siregnost FD 5. As Siregnost FD 5 is a simple and reliable method, it is a valuable completion of standard lung function methods. However, for detailed analysis the respiratory system should be investigated at a variety of frequencies.
Eight children, five boys and three girls, aging from 2 to 13 years (M = 9 +/- 3) were treated with the "Vienna phrenic pacemaker". Indication for implantation was central alveolar hypoventilation syndrome (CAH) in one case and total ventilatory insufficiency due to high cervical cord or brain stem lesion (SCI) in seven cases. Four electrodes were applied to each phrenic nerve via sternotomy. Both hemidiaphragms were paced synchronously with increasing duty cycles to condition the diaphragms for continuous electrophrenic respiration (EPR). EPR could be performed successfully in all children but one. Four children could achieve chronical EPR, one is in conditioning period. Two patients could not be discharged from hospital due to parental neglect and died after two and three years of intermittent stimulation. Six children could be discharged from hospital, two of them died after one and four years of chronic pacing. In one case tracheotomy could be closed definitively. Ventilatory insufficiency due to CAH and SCI can be treated even in children with diaphragm pacing, provided the indication for implantation, containing medical and social aspects, was made correctly. Diaphragm pacing probably will not lengthen life of severely injured children but it can increase the quality of their life and therefore should be preferred to positive pressure mechanical ventilation.
Measurement of DCO is known to be dependent upon functional inhomogeneities. Because different types of inhomogeneities are operative in patients with bronchial asthma and patients with emphysema, different changes of DCO with increasing breath-holding time, tA, are to be expected. We studied the change of Dco with increasing breath-holding time in healthy subjects, patients with asthma bronchiale and patients with emphysema. In the patients the severity of airway obstruction was about the same. The following results were obtained: (a) in healthy subjects and in the asthmatics DCO decreased with tA, in a similar manner, approaching a value (ml·min-1·Terror-1) of 34.7 and 31.6 at 10 sec, respectively, and (b) in patients with emphysema DCO increased with tA, yielding negative values at small tA: 1.5 sec-23.4; 10 sec: 11.7.From these results we suggest that in healthy subjects and in patients with bronchial asthma parallel inhomogeneities influence the course of DCO. In emphysema the time course of DCO is best explained with a faster intrapulmonary mixing of He compared to CO. This behavior indicates that in emphysema low DCO values can be mainly attributed to large diffusional resistances (stratification) within the lungs.
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