Respiratory Mechanics, Respiratory Muscle Strength, Control of Ventilation and Gas Exchange in Patients with Autoimmune Liver Disease

Objectives: To assess respiratory elastance and resistive properties in patients with autoimmune liver disorders using the passive relaxation expiration technique and compare findings to a group of patients with non-autoimmune liver disease and control subjects. These findings were then related to control of ventilation and gas exchange. A secondary objective was to assess respiratory muscle strength and gas exchange and their relation to respiratory mechanics. Methods: Measurements included respiratory elastance and resistance using the passive relaxation method. Pulmonary function, gas exchange and control of ventilation were assessed using standard methods. Results: a) Compared to control subjects, Ers in patients with liver disease was on average 50% greater than in controls;b) mean respiratory resistance, expressed as the respiratory constants, K1 and K2 in the Rohrer relationship, Pao/V’ = K1 + K2V’, was not different from control resistance;c) mean maximal inspiratory and maximal expiratory pressures averaged 36% and 55% of their respective control values;d) inspiratory occlusion pressure in 0.1 sec (P0.1) was increased and negatively associated with FVC;and e) increases in P0.1, mean inspiratory flow (Vt/Ti) and presence of respiratory alkalosis confirmed the increase in ventilatory drive. Despite inspiratory muscle weakness in patients, P0.1/Pimax averaged 5-fold higher than in control subjects. Conclusions: Despite inspiratory muscle weakness and a V’E similar to that in normal subjects, central drive is increased in patients with chronic liver disease. The increase in ventilatory drive is related to smaller lung volumes and weakly associated with increase in respiratory elastance. Findings confirm that P0.1 is a reliable measure of central drive and is an approach that can be used in the evaluation of control of ventilation in patients with chronic liver disease.

EVALUATION OF THE BRAIN TOLERANCE TO CAROTID ARTERY OCCLUSION

Objective: To establish an objective criterion for assessing brain tolerance to carotid artery occlusion. Methods Endovascular trial balloon occlusion of carotid artery (TBO) in combination with single-photon emission computed tomography (SPECT), transcranial Doppler ultrasonography (TCD) and carotid artery stump pressure (SP) measurement was performed routinely for those patients who might have carotid artery manipulated or permanently occluded. Results Out of the 10 cases, one failed the TBO, though an angiographically adequate collateral circulation was observed. The patient’s SP and relative symmetry (rS) of SPECT imaging were 51mmHg and 86%. The remaining cases showed negative TBOs. After carotid occlusions, their mean velocity of ipsilateral middle cerebral artery decreased (16. 3 ± 6. 9 )%. The mean rS was (98. 0 ± 2. 4)% (92. 7% -101. 3% ). The mean SP was (64. 5 ± 13. 0)mmHg [(72. 3±11. 3)% of baseline, range 32-83mmHg. For one subject, the ICA was occluded spontaneously in the test. A reversal internal carotid artery (ICA ) flow was noted in 3 patients with balloon inflated in the common carotid artery (CCA ). When the CCA was occluded, the system blood pressure and heart rate increased apparently. However, this phenomenon did not occur when the ballon was inflated in the ICA. Conclusion With this TBO technique, clinically silent areas of decreased perfusion might be detected. We suggest it be a routine examination prior to carotid manipulations.