• Guilherme Loures de Araújo Penna, Paula Araujo Rosa, Pedro Martins Pereira Kurtz, Fabricio Braga, Gustavo Ferreira Almeida, Marcia Freitas, Luis Eduardo Drumond, Ronaldo Vegni E Souza, Michel Schatkin Cukier, André Salgado, Clóvis Faria, José Kezen, André Miguel Japiassú, Marcelo Kalichsztein, and Gustavo Nobre.
• Serviço de Terapia Intensiva, Casa de Saúde São José, Rio de Janeiro, RJ, Brasil.
• Rev Bras Ter Intensiva. 2009 Dec 1;21(4):349-52.

ObjectivesArterial pulse pressure respiratory variation is a good predictor of fluid response in ventilated patients. Recently, it was shown that respiratory variation in arterial pulse pressure correlates with variation in pulse oximetry plethysmographic waveform amplitude. We wanted to evaluate the correlation between respiratory variation in arterial pulse pressure and respiratory variation in pulse oximetry plethysmographic waveform amplitude, and to determine whether this correlation was influenced by norepinephrine administration.MethodsProspective study of sixty patients with normal sinus rhythm on mechanical ventilation, profoundly sedated and with stable hemodynamics. Oxygenation index and invasive arterial pressure were monitored. Respiratory variation in arterial pulse pressure and respiratory variation in pulse oximetry plethysmographic waveform amplitude were recorded simultaneously in a beat-to-beat evaluation, and were compared using the Pearson coefficient of agreement and linear regression.ResultsThirty patients (50%) required norepinephrine. There was a significant correlation (K = 0.66; p < 0.001) between respiratory variation in arterial pulse pressure and respiratory variation in pulse oximetry plethysmographic waveform amplitude. Area under the ROC curve was 0.88 (range, 0.79 - 0.97), with a best cutoff value of 14% to predict a respiratory variation in arterial pulse pressure of 13. The use of norepinephrine did not influence the correlation (K = 0.63, p = 0.001, respectively).ConclusionsRespiratory variation in arterial pulse pressure above 13% can be accurately predicted by a respiratory variation in pulse oximetry plethysmographic waveform amplitude of 14%. The use of norepinephrine does not alter this relationship.

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