Chest
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Comparative Study
Comparison of arterial-end-tidal PCO2 difference and dead space/tidal volume ratio in respiratory failure.
End-tidal CO2 monitors are used to estimate arterial CO2 pressure (PaCO2), but appropriate use of this noninvasive method of assessing blood gases is unclear. In patients with lung disease, the end-tidal CO2 pressure (PETCO2) can differ from PaCO2 because of ventilation-perfusion (VA/Q) mismatching, and changes in PETCO2 may be seen with corresponding increase, decrease, or no change in PaCO2 depending on what happens to VA/Q mismatching. We compared the difference between PETCO2 and PaCO2 in 17 patients undergoing mechanical ventilation. ⋯ Our studies confirm that PetCO2 is a poor estimate of PaCO2 in patients with respiratory failure. However, the P(a-et)CO2 may be the most appropriate use for end-tidal PCO2 monitoring. In addition, we found that the end-tidal CO2 monitor may be easily adapted for expedient measurement of VD/VT.
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To assess the relative contributions of age, gender, obesity, pulmonary function, and the severity of sleep-induced respiratory abnormalities to the development of alveolar hypoventilation in patients with occlusive sleep apnea syndrome, prospective data from III patients with occlusive sleep apnea were analyzed by stepwise logistic and multiple regression techniques. The significant variables in a logistic regression model predicting the presence of hypercapnia were daytime arterial oxygen pressure (PaO2; p less than 0.0001) and gender (p less than 0.04), the latter reflecting the higher number of hypercapnic women in our patient population. Multiple regression analysis performed in the hypercapnic group to study the determinants of the severity of elevation of arterial carbon dioxide tension (PaCO2) revealed significant contribution from the PaO2, the apnea-plus-hypopnea index (AHI), and the percent predicted forced vital capacity (r2 = 0.56; p less than 0.0001), whereas in the normocapnic patients, PaCO2 related to PaO2 only. These results suggest that daytime hypoxemia, mechanical impairment of the respiratory system due to obesity or obstructive airway disease (or both), and the severity of sleep-induced respiratory abnormalities as assessed by AHI contribute to the severity of carbon dioxide retention in patients with occlusive sleep apnea in a multifactorial fashion.
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Despite the fact that endotracheal intubation is a skill essential for clinicians of varied specialties, the procedure is not without risk, especially when practiced in an emergency setting, particularly the field environment. Of all complications, none is more serious than unrecognized esophageal intubation. Clinical experience with a method of guided orotracheal intubation using a rigid-wire lighted stylet prompted us to develop a technique to confirm correct intratracheal placement of an endotracheal tube using a new flexible lighted stylet designed for nasotracheal intubation. ⋯ The level of experience or training bore no relationship to the ability of the intubator to identify correct placement. We conclude from the study that this technique is a rapid and reliable method of confirming correct placement of endotracheal tubes. The use of this method could reduce, if not eliminate, unrecognized esophageal intubation in the field, emergency department, the critical care unit, and the operating room.
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The correlation between mixed venous oxygen saturation (SvO2) and hemodynamic measurements was studied in 13 patients undergoing descending thoracic aortic aneurysm resection (DTAAR). A significant correlation (p less than 0.05) was found between cardiac index (CI) and SvO2 after the induction of anesthesia and at the end of surgery. However, no significant correlation could be found between SvO2 and CI during the most critical periods of the surgery that included the collapse of the left lung, the aortic clamping, and the aortic declamping. During DTAAR, continuous SvO2 monitoring is useful, but it cannot substitute for intermittent cardiac output and oxygen consumption (VO2) determinations.
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In the case reported, a patient with severe right ventricular failure following coronary revascularization was successfully weaned from cardiopulmonary bypass following creation of an atrial septal defect. This technique facilitated rapid decompression of the failing right ventricle by shunting blood to the more compliant left ventricle, thus augmenting left ventricular preload and enhancing cardiac output. Recovery of right ventricular function was demonstrated by progressive hemodynamic improvement, as well as reduction of right-to-left intracardiac shunting and resolution of arterial hypoxemia.