Effect of Hemidiaphragmatic Paresis Caused by Interscalene Brachial Plexus Block on Breathing Pattern, Chest Wall Mechanics, and Arterial Blood Gases

Abstract

We investigated the effects of hemidiaphragmatic paresis caused by interscalene brachial plexus block on breathing patterns, chest wall mechanics, and arterial blood gas tensions using respiratory inductive plethysmography.Ten healthy patients received interscalene block with 20-40 mL 1.5% lidocaine with epinephrine. Rib cage contribution to tidal volume (%RC) increased from 28.9% +/- 9.7% to 50.0% +/- 8.3% (P 2 decreased from 84.7 +/- 7.3 mm Hg to 78.0 +/- 9.5 mm Hg (P 2. These results indicated that VT, VE, and PaCO₂ were maintained after interscalene block, apparently by increases in f and %RC to compensate for hemidiaphragmatic paresis caused by interscalene block. Nevertheless, PaO₂ was reduced, presumably due to increased ventilation-perfusion mismatching. Recognizing that we studied healthy patients, the decrease in PaO₂ may be more in patients with cardiopulmonary disease. (Anesth Analg 1995;81:962-6)