Low flow inflation pressure-time curve in patients with acute respiratory distress syndrome.

OBJECTIVE: In mechanically ventilated patients with ARDS, determination of the lower (LIP) and upper (UIP) inflection points of the static pressure-volume curve (P-V) is crucial for planning ventilatory strategies. Recently, a simple new method was proposed for measuring the P-V curve by inflating the lung with constant low flow [14]. We hypothesized that during low flow inflation LIP and UIP might be determined using the pressure-time curve (P-T) instead of P-V. METHODS: Eleven paralyzed patients with ARDS were studied. During volume control ventilation the patients were allowed to reach passive functional residual capacity (FRC) and then ventilator frequency, inspiratory to total breath duration ratio and tidal volume (VT) were set to 5 breaths/ min, 80% and 500 or 1,500 ml, respectively. With these settings, constant inspiratory flow (V'I) was administered for 9.6 s and ranged, depending on VT, between 0.05 and 0.15 l/s. P-V and P-T were obtained at two levels of positive end-expiratory pressure (PEEP; 0 and 10 cm H2O), with V'I being achieved either fast (< 0.1 s, minimum delay) or slowly (0.4 s, maximum delay). RESULTS: With minimum flow delay for a given experimental condition, the shape of the P-T did not differ from that of P-V. In all cases P-T correctly identified the presence of LIP and UIP, which did not differ significantly between P-T and P-V. With maximum flow delay, compared to P-V, the initial part of P-T was significantly shifted to the left. P-T did not identify the presence of UIP and LIP in one and two cases, respectively. CONCLUSIONS: Provided that constant flow is given relatively fast, P-T accurately determines the shape of P-V, as well as the LIP and UIP. Flow delay causes a leftward shift of the initial part of P-T, masking the presence of LIP and UIP in some cases.

Primary cystadenomatous tumors of the bile ducts.

Two cases of cystadenomatous tumors of the biliary tract are presented. One was a cystadenoma and the other one was a cystadenocarcinoma. They are rare tumors, difficult to diagnose accurately preoperatively. The differential diagnosis of the cystic tumors of the liver in countries with a high incidence of liver hydatid disease is very important.

High-rate cardiac pacing increases blood pressure and decreases right atrial pressure in patients with hemodynamic significant acute right ventricular myocardial infarction and bradyarrhythmia.

BACKGROUND: In an 84-year-old patient with acute right ventricular myocardial infarction (RVI), complete heart block, and low cardiac output, a significant increase in blood pressure (BP) and decrease in right atrial pressure (RAP) were accidentally observed during the performance of high-rate ventricular pacing. METHODS: Based on that observation, the acute effects of high-rate cardiac pacing (VVI or AAI) on BP and RAP were studied in 15 consecutive patients (67.4 +/- 7.7 years), with hemodynamically significant RVI. Ten had advanced heart block and five had sinus bradycardia. Cardiac pacing with simultaneous recording of BP and RAP at intrinsic rhythm and at heart rates of 70, 90, 110, 130 beats/min was performed. RESULTS: Systolic BP (SBP) increased significantly from 94.6 +/- 15 mmHg during intrinsic rhythm to 101.9 +/- 13.8 mmHg-127 +/- 12.2 mmHg at heart rates 70-130 beats/min (p < 0.0001). Diastolic BP (DBP) also increased from 48.2 +/- 8.7 to 53.9 +/- 3.7-69.1 +/- 3 mmHg at heart rates 70-130 beats/min, (p < 0.014-0.0001). Mean RAP decreased from 14.5 +/- 5 to 14.1 +/- 5 mmHg-11.1 +/- 4.1 mmHg at heart rates 70-130 beats/min (p = 0.16-0.0001). Significant elevation of SBP (p < 0.007), DBP (p < 0.0075), and decrease of RAP (p < 0.038) were also detected by comparing the usual pacing rate at 70 beats/min with pacing rates at 90-130 beats/min. CONCLUSIONS: These findings, if demonstrated over a prolonged period during the acute state of RVI, may influence the management of patients with RVI to include high-rate cardiac pacing, probably in the range of 80-110 beats/min.