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The neuromuscular drive is increased in patients with an airway obstruction. The aim of the study was to estimate an influence of beta-agonist on breathing pattern and mouth occlusion pressure (P0.1) in patients with reversible and nonreversible airway obstruction. Ventilatory function tests, pattern of breathing analysis, mouth occlusion pressure (P0.1) and inspiratory impedance (P0.1/Vt/Ti) were measured in 23 obstructive patients and 20 healthy subjects. In all patients these measurements were repeated 20 minutes after bronchodilator inhalation (0.2 mg fenoterol). During quiet room-air breathing in patients we observed increased Vt, Vt/Ti comparing with healthy persons. The time of inspiration (Ti) and total time (Ttot) were shortened in comparison to our control group. P0.1 and inspiratory impedance were significantly increased (P0.1 3.6 +/- 1.6 vs 1.6 +/- 0.3 cm H2O, p < 0.01 and P0.1/Vt/Ti 6.6 +/- 2.3 vs 3.8 +/- 1.0 cm H2O/L/s). Measurements performed after bronchodilator inhalation revealed decrease of P0.1 and P0.1/Vt/ Ti in patients responsive to beta-agonist (delta FEVI > 15%). In unresponsive patients (delta FEVI < or = 15%) such decrease in neuromuscular respiratory drive was not observed. We conclude that diminishing of increased neuromuscular respiratory drive in patients with reversible obstruction is a consequence of airway resistance decreasing. It seems to be an additional, advantageous for a patient, effect of bronchodilator inhalation.

In some patients obstructive sleep apnoea (OSA) may co-exist with chronic obstructive pulmonary disease (COPD) and respiratory failure; the so-called "overlap syndrome". Obstructive, hypercapnic patients have both blunted ventilatory and mouth occlusion pressure responses during CO2 stimulation. The purpose of this study was to compare the pattern of breathing and CO2 response between OSA patients and those with the overlap syndrome. Twenty obese men with OSA and normal lung function (Group A), 11 obese men with overlap syndrome (Group B) and 13 healthy nonobese subjects (Group C) were examined. Lung function tests, breathing pattern, mouth occlusion pressure (P0.2) at rest, and respiratory responses during CO2 rebreathing were investigated. Diagnosis of OSA was established by standard polysomnography. There were no statistical differences between Groups A and B in apnoea & hypopnoea index (62 vs 54), mean arterial oxygen saturation (SaO2) during sleep (85 vs 84%) and in body mass index (BMI) 34.3 vs 36.3 kg.m-2. Minute ventilation, mean inspiratory flow and P0.2 at rest were increased in both groups of patients in comparison to controls. During CO2 rebreathing, group A had normal ventilatory and P0.2 responses, similar to controls, (2.7 +/- 1.1 vs 2.1 +/- 0.4 l.min-1.mmHg-1 and 0.7 +/- 0.3 vs 0.71 +/- 0.25 cmH2O.mmHg-1, respectively). However, Group B had significantly decreased ventilatory and P0.2 responses to CO2 (0.71 +/- 0.23 l.min-1.mmHg-1 and 0.34 +/- 0.17 cmH2O.mmHg-1, respectively). This comparison showed that patients with OSA had normal CO2 response when awake, whereas those with overlap syndrome had diminished CO2 response when awake.(ABSTRACT TRUNCATED AT 250 WORDS)

The foundations for a computer program allowing to monitor "on line" physiological data to clinically evaluate ventilatory control were set up. The new equipment demonstrates important innovations--lowered flow resistance, and decreased dead space, modernization of the blocking steering the computer valve. The new program allowed to decrease the time for analysis from couple of minutes to seconds. The results of ventilatory control studies in 11 healthy volunteers were found in ranges of normal values calculated earlier using an analogue method and are similar to those from literature.

20 obese men with OSAS were examined. Polysomnography confirmed this diagnosis. In the daytime pattern of breathing, mouth occlusion pressure (P0.2) and ventilatory responses during CO2 rebreathing test were evaluated. Lung function indices were within normal limits except decreased value of MEF 25 and slight hypoxaemia (Pa0.2 -67 +/- 6 mm Hg). In comparison to control subjects the patients with OSAS when awake had increased ventilation, Vt/Ti ratio and P0.2. This suggests increased inspiratory neuromuscular output in daytime. During CO2 rebreathing test the whole ventilatory and P0.2 response lines were shifted to the left but the slopes of these lines were within normal limits. We conclude that the control of breathing in OSAS patients is changed in comparison to healthy subjects with normal weight.

Twenty eight COPD patients with respiratory insufficiency were studied. These included: 12 hypoxemic and normocapnic patients, 16 hypoxemic and hypercapnic patients, and 22 healthy volunteers. During at rest respiration both COPD groups differed from the control group--demonstrating a higher respiratory incidence, VT/Ti and PO2 values. During hypercapnic stimulation using the rebreathing method the ventilatory response to CO2 in the COPD patients was lowered in comparison with the control. Increase of occlusion pressure as a response to the increasing hypercapnia was lowered in both groups, significantly in patients with hypercapnia.

22 normal volunteers, 57 patients with obstructive changes and 34 with restrictive type changes were studied. The following parameters were analyzed: maximal inspiratory and expiratory pressures, occlusion pressure and components of the breathing pattern. The patients were divided according to the degree of airway resistance and fall of vital capacity. All patients compared with the healthy volunteers demonstrated higher minute ventilation, and a higher neuro-muscular respiratory drive as shown by the VT/Ti index and occlusion pressure. The breathing pattern did not correlate significantly with the different abnormalities of respiratory function in the studied groups. In the patients with obstructive changes a weak correlation was found between the occlusion pressure and airway resistance. In patients with restrictive type changes a weak correlation between occlusion pressure, static and specific compliance was found. The occlusion pressure was a more specific parameter characterizing respiratory drive compared with the VT/Ti index. Disturbances of pulmonary mechanics have a small but significant effect on respiratory control.