Postoperative pulmonary complications increase mortality, length, and cost of hospitalization. A better diaphragmatic strength may help face an increased work of breathing postoperatively. We, therefore, sought to determine if a low preoperative diaphragm thickening fraction (TFdi) determined by ultrasonography helped predict the occurrence of postoperative pulmonary complications after cardiac surgery independently of indicators of frailty, sarcopenia, and pulmonary function.
Prospective observational cohort study.
Montreal Heart Institute, an academic cardiac surgery center in Canada.
Adults undergoing nonemergency cardiac surgery.
We measured the preoperative thickness of the right and left hemidiaphragms at their zone of apposition at end-expiration (Tdi,ee) and peak-inspiration (Tdi,ei) with ultrasonography. Maximal thickening fraction of the diaphragm during inspiration (TFdi,max) was calculated using the following formula: TFdi,max = (Tdi,ei–Tdi,ee)/Tdi,ee. We also evaluated other potential risk factors including demographic parameters, comorbidities, Clinical Frailty Scale, grip strength, 5-meter walk test, and pulmonary function tests. We repeated TFdi,max measurements within 24 hours of extubation. The primary composite outcome of this study was the occurrence of postoperative pulmonary complications, defined as pneumonia, clinically significant atelectasis, or prolonged mechanical ventilation (> 24 hr).
Of the 115 patients included, 34 (29.6%) developed postoperative pulmonary complications, including two with pneumonia, four with prolonged mechanical ventilation, and 32 with clinically significant atelectasis. Those with postoperative pulmonary complications had prolonged ICU and hospital length of stays. They had a lower TFdi,max (37% [interquartile range, 31–45%] vs 44% [interquartile range, 33–58%]; p = 0.03). In multiple logistic regression, a TFdi,max less than 38.1% was associated with postoperative pulmonary complications (odds ratio, 4.9; 95% CI, 1.81–13.50; p = 0.002). All patients who developed pneumonia or prolonged mechanical ventilation had a TFdi,max less than 38.1%. Respiratory rate and diabetes were also independently associated with postoperative pulmonary complications, while pulmonary function tests and the assessed indicators of frailty and sarcopenia were not.
A low preoperative TFdi,max can help to identify patients at increased risk of postoperative pulmonary complications after cardiac surgery.
1Intensive Care Unit, Department of Cardiac Surgery, Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada.
2Department of Medicine, Hôpital Sacré-Coeur de Montréal, Montreal, QC, Canada.
3Department of Medicine, Hôpital Le Gardeur, Terrebonne, QC, Canada.
4Department of Medicine, Centre Hospitalier Régional de Trois-Rivières, Trois-Rivières, QC, Canada.
5Department of Anesthesia, Centre Hospitalier de l’Université de Montréal, Montreal, QC, Canada.
6Department of Medicine, Hôpital Maisonneuve-Rosemont, Montreal, QC, Canada.
7Department of Biostatistics, Montreal Health Innovations Coordinating Center, Montreal Heart Institute, Montreal, QC, Canada.
8Intensive Care Unit, Department of Anesthesiology, Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada.
Clinical Trial Registration: ClinicalTrials.gov NCT02658006.
Dr. Denault takes responsibility for the content of the article, including the data and analysis. Dr. Denault had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Drs. Cavayas, Eljaiek, Rodrigue, Levesque, and Denault contributed to study design and data collection. Drs. Cavayas, Eljaiek, Rodrigue, Lamarche, Girard, Wang, Levesque, and Denault contributed to data analysis and interpretation, and the writing of the article. All authors approved the article.
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Dr. Girard received funding from GE Healthcare (consulting). The remaining authors have disclosed that they do not have any potential conflicts of interest.
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