Dual-respiratory rhythms. A key to diagnosis of diaphragmatic flutter in patients with HVS.

We discuss three cases of diaphragmatic flutter in patients with extreme polypnea and symptoms of respiratory alkalosis. Initially, the diagnosis for each case was HVS. However, analysis of the respiratory pattern during attacks revealed two frequencies. A fast respiratory rhythm (230 to 250 breaths per minute) was superimposed on a slow rhythm (15 to 30 breaths per minute). The fast rhythm maintained blood gases at normal limits or hypocapnic levels. The dual respiratory rhythms, which do not occur with HVS, indicated diaphragmatic flutter. In addition, the usual treatment for HVS-breathing CO2 mixed air-did not influence the attacks. For two of the three patients, an intravenous dose of DPH suppressed the abnormal respiratory patterns immediately and completely. The third patient responded to an intramuscular injection of haloperidol. For these cases, the dual respiratory rhythms were the key to diagnosis of diaphragmatic flutter which accompanied hyperventilation.