Nasogastric (NG) tubes are routinely used in patients undergoing cardiac surgery. This randomized study was designed to assess gastroesophageal reflux (GER) without a NG tube (control) compared with a NG tube managed either by gravity drainage (gravity) or continuous low-grade suction (suction). Antimony pH probes were placed in the lower esophagus and trachea after induction of anesthesia in 51 patients, and pH was recorded every 5 s until the time of tracheal extubation. GER was defined as reversible decrease in esophageal pH to less than 4.0. No significant difference was found between groups in age, weight, gender, duration of postoperative ventilation, morphine use, or antiemetic use. All indicators of GER were seen more frequently in the gravity group compared with the two other groups (P < 0.001). One episode of sudden decrease in tracheal pH was observed in a patient in the gravity group, indicating tracheal aspiration, which was associated with delayed extubation and postoperative pneumonia. The absence of a NG tube is not associated with reflux, probably since the gastroesophageal sphincter remains competent. NG tubes are not routinely necessary for cardiac surgery in patients without risk factors for GER, and increase reflux risk if managed without low-grade suction.
We have measured the arterial to end-tidal PCO2 difference (PaCO2-PE'CO2) in 22 patients undergoing pulmonary resection in the lateral thoracotomy position during two-lung ventilation (TLV) and after transition to one-lung ventilation (OLV). With OLV for each patient, the practice of correcting the estimate by an initial measurement of (PaCO2-PE'CO2) was evaluated by subtracting the initial (PaCO2-PE'CO2) from subsequent values measured at 10-min intervals. Net (uncorrected) and corrected differences during OLV were analysed using ANOVA. (PaCO2-PE'CO2) values during TLV and OLV were similar: mean (SD) 1.3 (0.6) kPa and 1.2 (0.7) kPa, respectively (ns). Mean (PaCO2-PE'CO2) varied in the range 0.2-2.5 kPa, while maximum (PaCO2-PE'CO2) was 0.3-2.8 kPa. The mean (SD) of 133 pairs of measurements with OLV was 1.1 (0.7) kPa. Even after correction, mean (PaCO2-PE'CO2) varied in the range -0.7 to 0.8 kPa; individual extreme values were from -1.3 to 1.7 kPa. Variation between patients was found to be greater than variation within patients for both net and corrected differences (F ratio = 37.0 and 10.9, respectively), although calculating a corrected difference did reduce variation between patients from a mean square value of 2.44 to 0.61. The wide variation in (PaCO2-PE'CO2) suggests that the accuracy of estimation of PaCO2 by monitoring PE'CO2, although improved by the use of a corrected difference, remains questionable during OLV.
SummaryIn critically ill patients with septicaemia, the increased that the time delay between the instigation of the patient's oxygen requirements demand increased oxygen delivery inspiratory effort and the onset of inspiratory gas flow is and a reduction in the metabolic demands of tissues. minimal, thus avoiding an intrapulmonary pressure drop Respiratory muscles in particular can utilise large amounts which will greatly increase the work of breathing. A survey of oxygen when the work of breathing is increased. A of 55 major intensive care units in the United Kingdom in reduction in the work of breathing leads to a reduced 1984 found that this physiological goal was achieved in oxygen cost of breathing, thus avoiding 'oxygen steal' from 82% of units by custom-made CPAP circuits, while 78% nonrespiratory tissues and consequent impairment of vital had ventilators equipped with a CPAP facility [4]. Of the organ function.CPAP systems investigated, the most acceptable adult Continuous positive airways pressure (CPAP) is a widely CPAP delivery system was the traditional custom-made used technique for respiratory support in patients with type with a high flow (greater than 301.min-'), a large respiratory failure. With CPAP, a significant decrease inspiratory reservoir, and a water bottle. (25%) in the work of breathing has been demonstrated in These considerations led us to compare the CPAP mode babies [l], and a similar decrease suggested in adults [2]. To of the Engstrom Erica ventilator with a custom-made minimise the work of breathing during CPAP, the airway continuous flow CPAP system in terms of measured and pressure must be maintained at a near constant value derived haemodynamic variables and oxygen consumption throughout the respiratory cycle [3]. It is also important and delivery during weaning from mechanical ventilation.
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