“Best” PEEP during one-lung ventilation

Abstract

Eight patients were studied under general anaesthesia for elective pulmonary lobectomy to see if intrinsic positive end-expired pressure (PEEPi) would appear or increase in the dependent lung during one-lung ventilation (OLV) or if application of external PEEP equal to individually measured PEEPi would produce better arterial oxygenation, haemodynamic state and oxygen delivery than either zero PEEP (ZEEP) or an external PEEP 5 cm H2O greater than PEEPi. Patients were non-obese, without obstructive airways disease, aged 53-76 yr and ASA < III. They received standardized anaesthesia with fentanyl, 50% nitrous oxide in oxygen and isoflurane; monitoring included radial and fibreoptic pulmonary arterial catheters and intermittent positive pressure ventilation with a tidal volume of 8 ml kg-1, 16 bpm, and an I:E ratio of 1:2. PEEPi was measured during two-lung ventilation (TLV) and OLV, using rapid airway occlusion at end-expiration. There was no PEEPi during TLV, but 2-6 mm Hg of PEEPi appeared during OLV. Applying external PEEP equal to individually measured PEEPi reduced venous admixture and increased PaO2 without a decrease in cardiac index (thus increasing oxygen delivery) compared with ZEEP, but the improvement in pulmonary gas exchange was lost and an additional penalty of reduced cardiac output was imposed when external PEEP was increased to 5 mm Hg above PEEPi.

Variations in dynamic lung compliance during endoscopic thoracic sympathectomy with CO 2 insufflation

“…During OLCV with capnothorax, a variety of pathophysiologic changes occur which may interfere with the ability of ventilated lung to maintain its normal FRC. In one study, the peak and inspiratory airway pressures were significantly lower during two-lung ventilation than at any time during OLCV [5]. In the present study, there were significant differences between the peak airway pressure before and during OLCV at different IPP.…”

Monitoring of vecuronium-induced neuromuscular blockade during one-lung ventilation

“…Hence, not only defl ation of the lung but also hyperinfl ation of the lung may accelerate recovery from neuromuscular blockade. It has been reported that the magnitude of autopositive end-expiratory pressure (auto-PEEP) is higher during OLV than during TLV [7,8,10,11]. Inomata et al [10] noted that airway resistance increased because of a decrease in the compliance of the dependent lung during OLV, while they found that auto-PEEP was most likely to exist when airway resistance was increased.…”

“…It has been reported that the magnitude of autopositive end-expiratory pressure (auto-PEEP) is higher during OLV than during TLV [7,8,10,11]. Inomata et al [10] noted that airway resistance increased because of a decrease in the compliance of the dependent lung during OLV, while they found that auto-PEEP was most likely to exist when airway resistance was increased. They also postulated that auto-PEEP tended to appear in the dependent lung during OLV, primarily because of high airway resistance from a relatively small tracheal tube for OLV.…”

“…Consequently, both defl ation and hyperinfl ation of the lung are thought to strengthen the contraction of the skeletal muscles. Also, the airfl ow resistance is higher for the double-lumen tube compared with a single-lumen tube [9], and the magnitude of autopositive end-expiratory pressure (auto-PEEP) is higher during OLV than during two-lung ventilation (TLV) [7,8,10,11]. Such types of ventilatory loading markedly increase spontaneous activity in the pulmonary vagal afferent nerves [12], which, as noted above, enhances the activity of the skeletal muscles.…”

Protective Ventilatory Approaches to One-Lung Ventilation: More than Reduction of Tidal Volume

“…Mild to moderate PEEP levels are sufficient to keep recruited alveoli open in healthy subjects without deterioration of hemodynamics or hypoxic pulmonary vasoconstriction [107,108]. An external PEEP of 5 cmH 2 O did not increase the total PEEP in patients during OLV [109].…”