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DISCUSSION part 2

The other possibility is that the right-sided ECG pattern in normal subjects may vary with age. If this is indeed so, then differences can be expected between our study population consisting of young male subjects and the study population of Andersen et al consisting of much older subjects. However, it is interesting to note that in the study reported by Morgera et alconsisting of 82 subjects (45 men and 37 women) without clinical and ECG evidence of cardiac and pulmonary disease and with an age spectrum which is somewhat similar to that of the subjects in the study by Andersen et al (mean, 44 years; range, 17 to 86 years), the prevalence of a combined qS and qr pattern was much lower than that seen in the study of Andersen et al but was similar to that seen in our study.

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Right Chest Electrocardiographic Patterns in Normal Subjects: DISCUSSION

May 1, 2011 Author: Walter Mcneil | Filed under: Main

In this study of 110 healthy young male subjects, the prevalence of a rS pattern decreased from V3R to V6R. For example, 89 percent of our subjects showed this pattern in V3R but only 37 percent of them showed it in V6R. However, the opposite was the case for a rSr pattern with a prevalence of 10 percent in V3R and 36 percent in V6R. These findings are similar to those reported by Andersen et al in 109 normal subjects and by Morgera et al3 in 82 normal subjects. Again, similar to the experience of Andersen et al, the amplitudes of the r wave, S wave and secondary r (qr, rSr) wave in our subjects progressively decreased from V3R to V6R (from a mean value of 3.0 to 1.0 mm for r wave, 5.9 to 1.7 mm for S wave and 2.0 to 1.6 mm for secondary r wave) (Tables 3 through 5, Fig 1).

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Right Chest Electrocardiographic Patterns in Normal Subjects: RESULTS

Apr 30, 2011 Author: Walter Mcneil | Filed under: Main

Table 1 shows the age and the number of subjects in each ethnic group. Table 2 shows the frequency of the various ECG patterns in leads V3R to VeR. The amplitudes of the r wave, S wave, secondary r wave (qr, rSr) and Q wave (all measured to the nearest 0.5 mm) are shown in Tables 3 through 6. In all the 110 subjects, the ST segments merged imperceptibly with the ascending limbs of the T waves and an actual J point was not present. The ST segment deviation was measured 40 and 80 ms after the last QRS deflection. Table 7 shows the percentage of subjects with 0.5 to 1 mm and 1.0 mm positive ST segment deviation.

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Right Chest Electrocardiographic Patterns in Normal Subjects

Apr 29, 2011 Author: Walter Mcneil | Filed under: Main

Patterns in Normal Subjects

To recent years, the important role of right-sided chest lead ECGs in the detection of RV infarction in patients suffering from inferior myocardial infarc­tion of the left ventricle has been fully recognized.Several authors have stated that the presence of Q waves and elevated ST segments in right-sided chest leads, especially in V4R, are highly sensitive and specific indicators of RV infarction. However, to be confident that this ECC abnormality has a high specificity for RV infarction, the spectrum of the right- sided ECG pattern in the normal population must be known. Since there have been very few reports so far describing right-sided ECG patterns in normal sub­jects, we decided to study 110 normal healthy male subjects who were about to undergo active, rigorous military training as part of their national service commitment.

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Pressure Ventilation: DISCUSSION

In the present study, HFJV applied with an identical Paw as during IPPV did not modify pulmonary gas exchange, MAP, and CI. Similarly, no significant differences in mean CBF values (Fb ISI) were noted.

Classic main determinants of CBF remained stable and were comparable during both modes of ventila­tion. The PaC02 and rectal temperature were main­tained in a narrow range fixed by our experimental protocol, and MAP did not change. Furthermore, Paw did not vary throughout the experiment, resulting in stable arterial oxygenation and probably in a similar lung volume, and with an identical effect on systemic hemodynamics. This is in agreement with previous studies showing a close relationship between Paw and systemic hemodynamics. In particular, our results confirm that HFJV has no different effect on cardiac output than during IPPV at similar Paw. Our patients had a relatively low dynamic total respiratory compli­ance (50 ml/cm H20), most probably due to a moderate interstitial pulmonary edema due to cardiopulmonary bypass. This relatively low compliance may have attenuated the influence of variations of intrathoracic pressure on cardiac filling pressures, ventricular vol­umes, and cardiac output.

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The investigation took place 205 ± 60 minutes after the end of the surgery. For technical reasons in measuring CBF, the latter was not measured in four patients during the second control period. Respiratory data are summarized in Table 1. To obtain PaC02 between 4.5 and 5.5 kPa, a tidal volume of 9.2 ±0.3 ml/kg was used during IPPV and the driving pressure of the HFJV ventilator was set at 1.0 ±0.1 bar. The Pa02 values were similar during the two types of ventilatory support. A dynamic total respiratory com­pliance of 50 ±5 ml/cm HzO was measured during IPPV. Peak inspiratory pressure was significantly (p<0.05) lower during HFJV than during the two periods of IPPV, whereas Paw remained in the same range during both modes of ventilation. (more…)

Patients

Twenty four patients (four women and 20 men), mean age 58.6 ±4.8 years (mean±SD), mean weight 72.3 ±10.2 kg, were investigated at least two hours after a classic intravenous anesthesia (midazolam 0.1 mg/kg/h, fentanyl 3.0 ±0.8 mg) for elective open- heart surgery. Patients presenting unstable angina, unilateral pul­monary pathology, chronic obstructive pulmonary disease, or asthma were excluded from the study. All patients gave their informed consent to the study which was accepted by the committee for ethics in human research of our institution.

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Positive Pressure Ventilation

Tntermittent positive pressure ventilation, particu­larly when applied with positive endexpiratory pressure, improves blood oxygenation by increasing volume and surface area of the lung for gas exchange.However, changes of lung volume and increased airway pressure have important side effects on cardiac output and regional blood flow. The magnitude of these hemodynamic changes is largely dependent on Paw and pulmonary compliance as well as on baroreceptor reflexes and blood volume. To avoid these untoward effects, Oberg and Sjostrand proposed a mechanical ventilation technique using low tidal volumes at a high respiratory rate. However, to obtain an adequate pulmonary gas exchange, Paw during HFJV had to be similar to Paw during IPPY If lung inflation was moderate and the regulation of systemic arterial pressure by baroreceptors was not modified, systemic hemodynamic effects of HFJV and IPPV were similar for identical values of Paw. In contrast, HFJV was less detrimental on the cardiovascular system than IPPV in case of cardiocirculatory shock.

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