No abstract

Evidence warranting low/moderate confidence suggests that midodrine improves clinical important outcomes in patients with SOH and RRS.

We examined 166 patients with advanced chronic obstructive pulmonary disease (COPD) treated with long-term oxygen therapy (LTOT) in order to evaluate the prognostic factors of such patients. The mean observation period was 24 months (range 2–50 months) and the following variables were considered: age, forced expiratory volume in 1 s (FEV₁), arterial oxygen tension (PaCO₂), arterial carbon dioxide tension (PaCO₂), hematocrit, right ventricular systolic pressure (RVSP; evaluated by Doppler echocardiography), number of hospi-talizations in the 2 years prior to prescription of LTOT and body mass index. The overall survival rate was 78.3% at 24 months and 67.1% at 36 months. A univariate analysis identified three variables as significant predictors of survival: FEV₁, PaO₂ and RVSP. A multivariate analysis, using Cox’s model, showed an independent predictive power for RVSP, age and FEV₁. RVSP higher than 35 mm Hg, age greater than 70 years and FEV₁ lower than 30% of the predicted value were associated with shortened survival. The importance of pulmonary hypertension as a predictor of death suggests that LTOT could be prescribed earlier for COPD patients with cor pulmonale, as oxygen has been shown to be the only effective therapy for improving the survival probability of these patients.

That there is some form of interaction between respiration and heart rate (H.R.) is very old knowledge, but it was only in the third decade of this century that Heymans (1929), using his technique of the isolated head, studied this interaction, with particular reference to the respiratory arrhythmia.Sinus arrhythmia becomes very evident when the depth and frequency of respiration are increased as in recovery after exercise. Considering the possibility of sudden large changes in blood flow through the chest producing an alteration of the H.R., some respiratory manceuvres, designed to vary the blood flow through the intrathoracic pressure, have been worked through systematically. But the sudden variations in the H.R. could not have been readily studied on account of the difficulties involved in accurate recording. A new technique has, in fact, made it possible to demonstrate a delay of about 5 sec in the cessation and reappearance of sinus arrhythmia when the breath is held.Analysis of the results seems to show a causal relationship between some alterations in intrapulmonary pressure and changes in H.R. Explanation of the results seems to involve the arterial baroreceptors or, at any rate, the left side of the heart, as the site of origin of the stimulus, which appears to be change of blood flow. The same mechanism might be involved also during ordinary quiet respiration. METHODSThe human experiments were performed on a group of fifteen male subjects ranging from 18 to 31 years of age. The subjects practised in advance the type of experiment to be performed, but the timing of events was given by the experimenter.The H.R. was computed from the QRS complexes of the e.c.g., recorded between the left leg and the forehead. A cardiotachometer of suitable design (Manzotti, 1956a) displayed the heart rate on linear ordinates, beat by beat, with a constant delay of 10 m-sec. The accuracy was ± 2%.A dotted record was obtained, each dot corresponding to one beat.In some experiments the respiratory movements were stethographically recorded by tying * Present address: Department of Physiology, University of Milan.