Introduction: Postoperative pulmonary complications (PPC) is one of the most frequent complications after cardiac surgery and a cause of prolonged hospitalization and decreased functional level after dismission. Mobilization and physical activity is a primary intervention in prevention and treatment of PPC, but knowledge about the impact of change of position in lung function in patients a few days after cardiac surgery is sparse. The primary aim of this study is to describe changes in lung function from supine to sitting position. The secondary aim is to test a handheld medical device for measurement of lung function (Spiropalm 6MWT, Cosmed, Italy) in terms of a later assessment of the relevance of implementation in clinical practice.
Methods: Lung function was measured 3 minutes in each position. Primary outcomes were: tidal volume (Vt), inspiratory capacity (IC), alveolar ventilation (VA) and peripheral oxygen saturation (SpO2). Secondary outcomes were: heart rate (HR), respiratory rate (RR), deadspace (Vd), pain and dyspnea. Tests for differences between positions were performed. To test, whether a calculated value of VA from Spiropalm were a clinically satisfying estimate of the actual ventilation, VA was calculated from Vt and mean values for Vd. These were compared to VA
Results: Results were based on data from 15 patients. Assessment took place on the 2nd or 3rd day after cardiac surgery. Significant increases were found in Vt (25%), IC (21%, VA (20%), Vd (15%) and SpO2 (0,89%). RF and HR were unchanged. Calculated values for VA were not statistically different from the actual VA, and correlation was moderate/strong. Bland Altman plots revealed increasing difference with increasing VA and large limits of agreements.
Conclusion: Significant increases were found in all primary outcomes and in Vd. The increase in SpO2 was unexpectedly not clinically relevant. This study brings more evidence to the practice of early mobilization as prevention and treatment of PPC in patients with relatively uncomplicated postoperative status. Inclusion of more patients would strengthen the power of the result, and further studies on lung function under physical activity as standing and walking are obvious. Calculating VA from estimated values for Vd is not a sufficiently accurate method of assessing VA. The relevance of implementing Spiropalm for assessment of the lung function for cardiac surgery patients should be further investigated.