Relationship between intrathoracic pressure and hemodynamics during cardiopulmonary resuscitation in a porcine model of prolonged cardiac arrest

Background The influences of intrathoracic pressure （ITP） to hemodynamic and respiratory parameters during cardiopulmonary resuscitation （CPR） are confusing. In this research, we investigated the phasic changes of ITP during CPR and reveal the relationships among the hemodynamics, respiratory parameters, and ITP. Methods After 8 minutes of untreated ventricular fibrillation, which was induced in twenty intubated male domestic pigs, 12 minutes of 30：2 CPR was performed. Continuous respiratory variables, hemodynamics, ITP and blood gas analysis were measured during CPR. After that, defibrillation was done and prognostic indicators after CPR was recorded. Results Average ITP at baseline was -（14.1±1.6） mmHg （1 mmHg=0.133 kPa）. When gasping inspirations were going on, it decreased sharply to near-50 mmHg. ITP fluctuated up and down quickly from near -20 mmHg to 20 mmHg when compressions were performed. These phasic changes became mild as the CPR was performed, the contrast of high and low ITP decreased to （12.95±2.91） mmHg at the end of 12 minutes of CPR. Total alveolus minute volume decreased too because of the decrease of compression and gasp related ventilations. Curve correlation was found between the tidal volume of compression and ITP： ITP=607.33/（1 ± 3134 x e-0.58 mv）, （e： natural constant, R2=0.895）. Negative correlations were found between the right atrial diastolic pressure and ITP （r=-0.753, P 〈0.01）; and positive correlations were found between the coronary perfusion pressure and ITP （r=0.626, P 〈0.01）. Conclusions ITP is one of the key factors which can influence the prognosis of CPR. Correlations were found between the changes of ITP and the tidal volumes of compressions, right atrial diastolic pressure and coronary perfusion pressure during CPR. More positive ITP during compression and more negative during decompression were good to ventilation and perfusion.

Respiratory Changes in the Superior Vena Cava Area on Inspiratory and Expiratory Chest CT: Comparison between Patients with COPD and with Bronchial Asthma

Purpose: In patients with obstructive lung diseases, alteration of intrathoracic pressure is closely related to hyperinflation and leads to hemodynamic impairments. Both intrathoracic pressure and hemodynamics are affected by the respiratory phase. In fact, a previous study showed that respiratory phasic variations in the superior vena cava (SVC) area significantly correlated with the extent of emphysema. Chronic obstructive pulmonary disease (COPD) and bronchial asthma manifest different pathophysiological changes in hyperinflation and hemodynamics. The current study was conducted to evaluate differences in respiratory variations in the cross-sectional area of the SVC between patients with COPD and with asthma. Materials and Methods: We measured the SVC area and calculated the ratio of the SVC area on inspiratory and expiratory scans (i/e-SVC ratio) in 66 patients with COPD and 16 patients with asthma. The cor-relations of the i/e-SVC ratios with airflow limitation, pulmonary small vessels less than 5 mm2 (%cross-sectional area [%CSA] < 5), and respiratory changes in lung volume (i/e-LV) obtained by inspiratory and expiratory computed tomography (CT) images were evaluated. Results: There was no significant difference in i/e-SVC ratio between COPD and asthma groups. In COPD patients, the i/e-SVC ratio significantly correlated with the %CSA ﹣0.433, P = 0.003), i/e-LV ratio (ρ = ﹣0.371, P = 0.011), and percent of predicted forced expiratory volume in 1 second (FEV1% predicted) (ρ = ﹣0.474, P = 0.001), whereas in asthma patients, there were no significant correlations between the i/e-SVC ratio and those functional parameters. Conclusion: There would be differences in the relationship between intrathoracic pressure and cardiopulmonary hemodynamics between COPD and asthma patients.