Hörmann C, Benzer H, Baum M, Wicke K, Putensen C, Putz G, Hartlieb S
Universitätsklinik für Anästhesie und Allgemeine Intensivmedizin, Institut für Radiodiagnostik und Computertomographie Innsbruck.
Anaesthesist. 1994 Jul;43(7):454-62. doi: 10.1007/s001010050078.
As early as 1974, Brian advocated the prone position for ventilated patients. He suggested that this position might enhance ventilation of the dorsal parts of the lungs, thereby improving oxygenation. These considerations have been confirmed by several experimental and clinical studies. Better secretion removal, decreased intrapulmonary shunting, and an increased FRC are thought to be responsible for the observed improvement of oxygenation. However, the prone position never became very popular in the clinical treatment of the adult respiratory distress syndrome (ARDS). Routine performance of thoracic CT scans in ARDS patients demonstrated preferential distribution of pathological densities in the dependent lung areas. The prone position therefore could possibly benefit these patients, as shown by two recent studies. The aim of our study was to evaluate the influence of repeatedly turning the patient to the prone position on gas exchange and thoracic CT findings in multiple-trauma patients. METHODS. Seven ventilated intensive care patients with severe ARDS (Murray Score > 2.5, Quotient > 0.7, mean airway pressure > 18 cm H2O, thoracic CT scan showing dorsal atelectases) were included in the study. Patients were turned from the supine to the prone position at 12-h intervals using an air-cushion bed (Mediscus, Austria). Redistribution of dystelectatic or atelectatic dependent lung areas was verified by means of repeated thoracic CT scans (Figs. 1, 8). RESULTS. The patients were intermittently turned for 6.5 +/- 1.1 days. The course of gas exchange is shown in Figs. 2 and 3. Initially, improvement of the respiratory quotient could only be achieved during prone positioning, from the 2nd day in the supine position as well. Intrapulmonary shunting showed a similar trend (Figs. 4 and 5). No significant changes in cardiovascular parameters could be observed. Control thoracic CT scans showed uniform reduction of atelectases in dependent lung areas (Figs. 1 and 8). The inspiratory fraction of oxygen could be reduced significantly as of the 2nd day (Fig. 7). Constant levels of positive end-expiratory pressure and tidal volume were associated with decreasing mean and plateau airway pressures (Fig. 6). DISCUSSION. Repeatedly turning the patient to the prone position produced long-lasting improvement of arterial oxygenation, which persists up to the end of the weaning process. This is in good accordance with other studies, however, this is the first study to report an observation period of more than 6 days of repeatedly turning the patient. These positive effects on gas exchange can be attributed to sudden improvement of the ventilation-perfusion ratio within the lung areas that become dependent after turning to the prone position. Due to reduced hydrostatic pressure and relative hyperventilation, previously collapsed alveoli are recruited in the lung areas that become non-dependent after turning to the prone position.
早在1974年，布莱恩就主张对接受通气治疗的患者采用俯卧位。他认为这种体位可能会增强肺背侧部分的通气，从而改善氧合。这些观点已得到多项实验和临床研究的证实。更好的分泌物清除、肺内分流减少以及功能残气量增加被认为是观察到的氧合改善的原因。然而，俯卧位在成人呼吸窘迫综合征（ARDS）的临床治疗中从未变得非常流行。对ARDS患者进行常规胸部CT扫描显示，病理密度在下垂肺区呈优先分布。因此，最近的两项研究表明，俯卧位可能会使这些患者受益。我们研究的目的是评估多次将患者转为俯卧位对多发伤患者气体交换和胸部CT结果的影响。方法。本研究纳入了7名患有严重ARDS的通气重症监护患者（默里评分>2.5，比值>0.7，平均气道压>18 cm H2O，胸部CT扫描显示背侧肺不张）。使用气垫床（奥地利Mediscus公司）每隔12小时将患者从仰卧位转为俯卧位。通过重复胸部CT扫描（图1、8）来验证下垂性肺不张或肺不张区域的重新分布。结果。患者间歇性翻身6.5±1.1天。气体交换过程见图2和图3。最初，仅在俯卧位时呼吸商得到改善，从仰卧位第2天起也是如此。肺内分流呈现类似趋势（图4和图5）。未观察到心血管参数有显著变化。对照胸部CT扫描显示下垂肺区肺不张均匀减轻（图1和图8）。从第2天起，氧吸入分数可显著降低（图7）。呼气末正压和潮气量保持恒定，同时平均气道压和平台气道压降低（图6）。讨论。多次将患者转为俯卧位可使动脉氧合得到持久改善，这种改善一直持续到撤机过程结束。这与其他研究结果相符，然而，这是第一项报告对患者进行超过6天的多次翻身观察期的研究。这些对气体交换的积极影响可归因于转为俯卧位后下垂肺区通气/灌注比值的突然改善。由于静水压力降低和相对过度通气，先前塌陷的肺泡在转为俯卧位后变为非下垂的肺区中重新开放。
