Association of Preoperative Clinical Characteristics with Duration of Mechanical Ventilation Following Coronary Artery Bypass Grafting: A Comparative Observational Study

Aim: To examine associations of preoperative clinical characteristics and surgical technique with the duration of postoperative invasive mechanical ventilation after coronary artery bypass grafting (CABG). Method: This prospective comparative observational study included 230 adults undergoing elective CABG at the Punjab Institute of Cardiology, Lahore, Pakistan, between May and November 2023. Patients were enrolled consecutively. Age, sex, body mass index (BMI), New York Heart Association (NYHA) class, hypertension, diabetes, hyperlipidemia, and smoking history were assessed against ventilation duration (hours). The primary outcome was recorded ventilation duration in hours. Prolonged mechanical ventilation (PMV), defined as >24 hours, was a secondary outcome derived from recorded duration. Duration was summarized as median (interquartile range [IQR]) and compared using the Mann–Whitney U test. Multivariable linear regression of log-transformed duration with HC3 robust standard errors estimated adjusted geometric mean ratios (GMRs). Findings: Of 230 patients, 180 (78.3%) underwent on-pump and 50 (21.7%) underwent off-pump CABG. Median ventilation duration was 5 (IQR 4–7) hours after on-pump versus 4 (4–5) hours after off-pump CABG (p=0.0032). PMV occurred in 26/180 (14.4%) and 3/50 (6.0%) patients, respectively (Fisher exact p=0.149). After adjustment for age, sex, body mass index, NYHA class, hypertension, diabetes, hyperlipidemia, smoking, and operative technique, on-pump CABG (GMR 1.32, 95% CI 1.09–1.59), smoking history (GMR 1.36, 95% CI 1.12–1.66) and recorded hyperlipidemia (GMR 1.33, 95% CI 1.15–1.54) were associated with longer ventilation. Conclusion: In this study, on-pump CABG was associated with longer postoperative mechanical ventilation than off-pump CABG. Smoking history and hyperlipidemia were also independently associated with longer ventilation duration. These findings highlight the importance of preoperative clinical assessment and surgical technique in postoperative respiratory care, although future prospective studies are needed to confirm these associations.