Biomedical subjects

Jonas Nielsen

Publications and source records attributed to Jonas Nielsen.

3 recordsLinked to original sources

PubMed2006

Central hemodynamics during lung recruitment maneuvers at hypovolemia, normovolemia and hypervolemia. A study by echocardiography and continuous pulmonary artery flow measurements in lung-injured pigs.

OBJECTIVE: The impact of lung-recruitment maneuvers on heart function at different volemic levels has not been studied in detail. We therefore investigated the effect on central hemodynamics of lung recruitment maneuvers at hypovolemia, normovolemia and hypervolemia in experimental lung injury. DESIGN: Randomized, controlled, cross-over experimental study. SETTING: Animal laboratory at a university hospital. PARTICIPANTS: Eleven anesthetized and lung-lavaged pigs. INTERVENTION: The animals were randomized to 10-s lung recruitment maneuvers followed by 30-s maneuvers (40 cm H(2)O airway pressure) or vice versa, performed under hypovolemia, normovolemia and hypervolemia. MEASUREMENTS AND MAIN RESULTS: Left-ventricular end-diastolic diameter and cardiac output were measured before, during, and 1 min and 5 min after the lung recruitment maneuver and left-ventricular eccentricity index was calculated for before and during the maneuver. Cardiac output and left-ventricular end-diastolic diameter (within parentheses) decreased significantly during both the 10-s and 30-s lung recruitment maneuvers at hypovolemia, by a mean of 89% (35) and 92% (33), at normovolemia by 75% (33) and 86% (32), and at hypervolemia by 56% (32) and 64% (43), respectively. At hypovolemia, cardiac output was increased above baseline 1-5 min following the 30-s maneuver. Left-ventricular eccentricity index increased significantly during the maneuver, indicating right ventricular dysfunction. CONCLUSIONS: In this animal lung injury model, lung recruitment maneuvers significantly decreased left-ventricular end-diastolic volume and cardiac output at hypovolemia. Hypervolemia did partly counteract this compromise. In addition, a marked right-ventricular dysfunction during the maneuver was found.

Animals↗

PubMed2006

Selective recruitment maneuvers for lobar atelectasis: effects on lung function and central hemodynamics: an experimental study in pigs.

We investigated whether selective lung recruitment of a lobar collapse would improve oxygenation and lung volume as well as a general (global) lung recruitment maneuver, with fewer circulatory side effects. In 10 ventilated, anesthetized pigs, a bronchial blocker was inserted in the right lower lobe, which was selectively lavaged to create a dense lobar collapse. The pigs were randomized into two orders of lung recruitment maneuvers (40 cm H2O airway pressure for 30 s): either a selective lung recruitment maneuver (using the inner lumen of the bronchial blocker) followed by a general lung recruitment maneuver, or vice versa. Median end-expiratory lung volume and median Pao2 increased significantly by approximately 100 mL and 16 kPa, respectively, with no significant differences between the two recruitment methods. There were no circulatory changes during the selective lung recruitment maneuver, but during the general lung recruitment maneuver, mean arterial blood pressure decreased significantly by 36 (21, 41) mm Hg (median, 25th and 75th percentiles), cardiac output by 2.1 (1.6, 2.5) L/min and left ventricular end-diastolic area by 4.4 (3.5, 4.5) cm2. In conclusion, a selective recruitment maneuver improved lung function similar to a general lung recruitment maneuver but without any circulatory side effects.

Animals↗

PubMed2005

Lung recruitment maneuver depresses central hemodynamics in patients following cardiac surgery.

OBJECTIVE: To assess the impact of the lung recruitment maneuver on circulation following cardiac surgery. DESIGN AND SETTING: Prospective randomized cross-over study at the Departments of Anesthesia and Thoracic Surgery, Copenhagen University Hospital. PATIENTS: Ten adult undergoing coronary artery bypass surgery. INTERVENTIONS: Patients were randomized to two durations of lung recruitment maneuvers (40 cmH2O airway pressure for 10 s and 20 s or vice versa after 5 min) administered immediately after surgery. MEASUREMENTS AND RESULTS: Transesophageal echocardiography (left ventricular short axis view), pulse contour cardiac output, and arterial blood pressure were monitored continuously. Systemic and pulmonary arterial blood gases were sampled before and after each lung recruitment maneuver to calculate the intrapulmonary shunt. Left ventricular end-diastolic areas decreased significantly during both the 10-s and the 20-s lung recruitment maneuvers. Cardiac output was 5.6+/-0.8 l/min at baseline, decreasing by 3.0+/-1.1 l/min and 3.6+/-1.2 l/min during lung recruitment maneuvers of 10 and 20 s, respectively. Shunt decreased from 20+/-5% to 15+/-6% after the first lung recruitment maneuver and from 15+/-6% to 12+/-5% after the second. CONCLUSIONS: Lung recruitment maneuvers markedly reduced cardiac output and left ventricular end-diastolic areas in hemodynamically stable patients following cardiac surgery.

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