Respiratory complications are a major contributor to postoperative morbidity and mortality after cardiac surgery. Goret et al. conducted a randomized clinical trial comparing 2 groups:

• Use of noninvasive mechanical ventilation (NIV) for 5 days before cardiac surgery and during the postoperative period (n = 107 patients)
• Standard care (n = 102 patients)

Patients with obstructive sleep apnea syndrome receiving CPAP were excluded, and the primary objective was to assess the impact of NIV on acute heart and respiratory failure up to 3 months after surgery.

The primary endpoint of acute cardiac and respiratory complications at 1 month after surgery was lower in the NIV group. When analyzed separately, only acute respiratory failure was significantly reduced in the NIV group, with no differences observed in the incidence of acute heart failure.

Despite the small sample size, the findings suggest a significant reduction in the risk of respiratory complications with NIV use before and after cardiac surgery, although implementation remains difficult, mainly because of poor adherence to NIV use, with 44% of patients discontinuing it during the postoperative period. This issue, together with the difficulty of conducting a blinded study involving NIV, makes the results difficult to extrapolate.

Meta-analyses evaluating prophylactic NIV after cardiac surgery have yielded conflicting results. Goret et al. introduce preoperative NIV as a form of “prehabilitation.” Preoperative NIV may improve postoperative adherence by allowing patients to become familiar with the technique. It remains unknown whether patients who tolerated NIV for longer periods achieved better outcomes. In addition, implementing preoperative NIV in all patients would require substantial financial and human resources.

This study shows promising results, but further data are needed to define the minimum treatment threshold required to achieve benefit and to identify strategies capable of improving postoperative adherence to NIV.

COMMENTARY:

In recent years, the profile of patients undergoing cardiac surgery has changed substantially. Mean age continues to rise, and the prevalence of frailty and associated comorbidities has increased, translating into greater perioperative complexity and a higher risk of postoperative complications. Among these, postoperative pulmonary complications (PPCs) are one of the main determinants of morbidity and mortality, prolonged ICU and hospital stay, and increased healthcare costs. Their estimated prevalence ranges from 30% to 50%, although this may be underestimated because of heterogeneity in definitions and diagnostic criteria across studies. The term PPC encompasses a broad spectrum of conditions, including atelectasis, pleural effusion, acute respiratory failure, respiratory infection, pneumothorax, bronchospasm, acute respiratory distress syndrome, and aspiration pneumonitis. Atelectasis and pleural effusions are the most common manifestations.

Cardiac surgery induces major changes in pulmonary function through multiple mechanisms. These include the surgical trauma associated with sternotomy, reflex phrenic nerve inhibition, diaphragmatic dysfunction, postoperative pain, impaired chest wall compliance, and the residual effects of general anesthesia during prolonged supine positioning. Cardiopulmonary bypass adds a systemic inflammatory and oxidative stress component that may promote lung injury through ischemia-reperfusion mechanisms. Altogether, these factors lead to reduced vital capacity, decreased functional residual capacity, distal airway closure, persistent atelectasis, and postoperative hypoxemia.

Protective intraoperative ventilation and selective recruitment maneuvers aimed at avoiding alveolar overdistension are currently recommended. However, the optimal intraoperative ventilatory settings remain poorly defined. In addition, the benefits achieved during surgery may be attenuated after extubation if adequate respiratory support strategies are not maintained.

Several clinical variables have been associated with a higher risk of PPCs, including age > 50 years, body mass index > 40 kg/m², ASA > II, obstructive sleep apnea syndrome, preoperative anemia and hypoxemia, urgent or emergency surgery, prolonged preoperative mechanical ventilation, chronic obstructive pulmonary disease, or an elevated EuroSCORE II. Multiple respiratory risk assessment tools have been developed, but their practical applicability is limited by their complexity and lack of external validation. Early identification of high-risk subgroups is essential for implementing individualized preventive strategies.

Cardiac prehabilitation is a multimodal intervention designed to optimize functional status before surgery. It includes aerobic exercise programs, respiratory muscle training, nutritional optimization, metabolic control, education, and psychosocial support. However, protocols remain heterogeneous, and the intervention requires high patient adherence as well as considerable specialized resources. From a pathophysiological standpoint, NIV offers several potential benefits:

• Alveolar recruitment
• Restoration of functional residual capacity
• Improved oxygenation
• Reduced work of breathing
• Optimization of ventilation-perfusion matching
• Reduced left ventricular preload and afterload

The literature shows heterogeneous results regarding the prophylactic use of NIV in cardiac surgery. Some studies have reported a reduction in atelectasis and shorter ICU and hospital stay. However, most have not consistently demonstrated reductions in reintubation, mortality, or cardiac complications.

Methodological limitations are frequent, including small sample sizes, variable definitions of PPCs, different ventilatory modes, different NIV interfaces, heterogeneous timing of application, and high dropout rates, especially in the immediate postoperative period because of pain, nausea, or patient discomfort.

High-flow oxygen therapy (HFOT) represents a potential alternative with better tolerance than conventional NIV, but its role in cardiac surgery has yet to be established.

In summary, respiratory complications after cardiac surgery are common, multifactorial, and clinically relevant. Preventive strategies should be comprehensive and begin in the preoperative period, combining risk identification, functional optimization, and protective ventilatory strategies during the intraoperative and postoperative phases.

NIV may improve parameters such as oxygenation and atelectasis, but the current evidence does not consistently demonstrate a reduction in reintubation or mortality rates. The high discontinuation rate limits its real-world effectiveness, which is why the reviewed article proposes preoperative use as a novel strategy, with the aim of improving patient adaptation during the postoperative period.

Benefit may depend on appropriate patient selection, timing of application, and duration of support. Standardized protocols and accurate risk stratification are still needed and remain to be defined.

In conclusion, the progressive increase in the complexity of patients undergoing cardiac surgery requires optimization of pulmonary protection strategies. NIV may be part of a multimodal approach, particularly in selected subgroups, but current evidence is insufficient to support its routine prophylactic use in all patients. Management should begin in the preoperative period and be sustained throughout the entire perioperative course in order to preserve its potential benefits.

REFERENCE:

Trela KC, Dhawan R. Noninvasive Ventilation in Cardiac Surgery Patients to Reduce Pulmonary Complications: Teaching an Old Dog New Tricks. J Cardiothorac Vasc Anesth. 2025 Dec;39(12):3219-3222. doi: 10.1053/j.jvca.2025.07.023.