RESUMO
During untreated ventricular fibrillation (VF), before CPR is applied, different bodily systems deteriorate at different rates. This paper describes the times when the EEG disappears, when respiratory arrest occurs, and when PD-PEA occurs. It also describes the frequency of VF waves over a 7-min period and how the frequency increases with good CPR.
Assuntos
Reanimação Cardiopulmonar/métodos , Insuficiência Cardíaca/prevenção & controle , Insuficiência Cardíaca/fisiopatologia , Modelos Cardiovasculares , Terapia Assistida por Computador/métodos , Fibrilação Ventricular/fisiopatologia , Fibrilação Ventricular/reabilitação , Simulação por Computador , Insuficiência Cardíaca/etiologia , Humanos , Fibrilação Ventricular/complicaçõesRESUMO
The objective of this 14-pig study was designed to determine the amount of lung ventilation obtainable by only rhythmic chest compression (100/min, 100 lbs). Tidal volume (TV), dead space (DS), and respiration rate (R) were measured with normal breathing and with rhythmic chest compression during ventricular fibrillation. The ratio of TV/DS was calculated in both cases. For normal breathing the ratio was 2.54 +/- 0.68; for chest compression breathing the ratio was 0.80 +/- 0.07. Minute alveolar ventilation (TV - DS)R was computed for both cases. With spontaneous breathing, the minute alveolar volume was 5.48 +/- 2.1 l/min. With only chest-compression breathing, the alveolar ventilation was -1.49 +/- 0.64 l/min. The negative minute alveolar volume and fractional ratio reveals that TV was less than the dead space indicating that chest-compression alone does not ventilate the lungs.
Assuntos
Reanimação Cardiopulmonar/métodos , Pulmão/fisiologia , Ventilação Pulmonar/fisiologia , Mecânica Respiratória/fisiologia , Volume de Ventilação Pulmonar/fisiologia , Animais , SuínosRESUMO
BACKGROUND: Ventricular-fibrillation (VF) wave frequency is known to decrease with prolonged, untreated VF. VF wave frequency is used as an algorithm to identify VF in AEDs and ICDs; yet the nature of the frequency change is not appreciated. METHODS: In this study, anesthetized pigs were used and VF was induced electrically. VF wave frequency was measured each second during VF for periods up to 200 sec. Defibrillation was achieved with transchest electrodes. VF wave frequency was plotted for each second during VF. In 2 animals, CPR was applied and VF wave frequency was measured. RESULTS: In all cases VF wave frequency decreased with increasing duration of VF. At the onset of VF, the VF wave frequency ranged from 5 to 12/sec. A plot of the normalized ratio of VF wave frequency during fibrillation to the VF frequency at induction decreased to between 0.1 and 0.8 of the initial frequency. In one of the animals, VF was initiated, CPR was provided and the VF wave frequency was measured over a 200-second period. Then, the procedure was repeated without CPR. Beyond 130 seconds, the VF frequency with CPR was higher than that without CPR, indicating myocardial oxygenation. CONCLUSION: Those who use VF wave frequency to identify the presence of VF should be aware of the nature of the VF wave frequency decrease with the passage of time.
