Driving pressure: A useful tool for reducing postoperative pulmonary complications

Abstract

The operating room is a unique environment where surgery exposes patients to non-physiological changes that can compromise lung mechanics. Therefore, raising clinicians’ awareness of the potential risk of ventilator-induced lung injury (VILI) is mandatory. Driving pressure is a useful tool for reducing lung complications in patients with acute respiratory distress syndrome and those undergoing elective surgery. Driving pressure has been most extensively studied in the context of single-lung ventilation during thoracic surgery. However, the awareness of association of VILI risk and patient positioning (prone, beach-chair, park-bench) and type of surgery must be raised.

Key Words: Ventilator-induced lung injury; Protective ventilation; Driving pressure; Mechanical ventilation; Surgery room; Single-lung ventilation; Operative room; Surgery

Core Tip: Driving pressure is a fundamental tool in patients with acute respiratory distress syndrome and those in the operative room setting. Surgery exposes patients to physiological and non-physiological modifications that compromise their mechanical lung properties. Raising awareness of the potential risk of ventilator-induced lung injury should be mandatory for clinicians to reduce postoperative lung complications.

TO THE EDITOR

We read the article "Driving pressure in mechanical ventilation: A review" by Zaidi et al[1]. We want to congratulate the authors for comprehensively summarizing the role of driving pressure in various mechanical ventilation scenarios. However, we believe that further exploration of the role of driving pressure in operating rooms is necessary.

The review emphasizes the importance of protective ventilation across diverse settings. We contend that the operating room presents a unique environment where it is crucial to evaluate the risk of ventilator-induced lung injury (VILI). Currently, scientific evidence for many surgical settings is lacking, and some information has been translated from intensive care units[2].

As highlighted by the authors, single-lung ventilation in thoracic surgery is associated with a high incidence of postoperative pulmonary complications (PPCs), which can be alleviated using protective ventilation strategies. However, it remains unclear how surgeons address the risk of PPCs in settings where the risk may not be as evident. Aresurgeons equally vigilant across all surgical settings?

The initial message underscores that maintaining a low driving pressure is crucial for preventing PPCs in non-cardiac surgery[3]. Meta-analyses have confirmed the independent association between driving pressure and the development of PPCs[4]. The driving pressure can be reduced either by lowering the tidal volume or adjusting the positive end-expiratory pressure (PEEP) levels. While the protective effects of low tidal ventilation on driving pressure are generally acknowledged, the benefits of PEEP remain debated, despite its close association with driving pressure. Tidal volume optimization and PEEP titration are effective strategies for reducing driving pressure, and driving pressure-guided ventilation may be a useful approach for general anesthesia[5]. However, in clinical practice, our comprehensive understanding of lung mechanics in different settings remains a topic of inquiry.

Patient positioning, such as prone, beach-chair, or park-bench, is known to alter the mechanical properties of the lung[6]. During surgery, patients may be placed in different positions (supine, lateral, or prone), which affect lung compliance, chest wall compliance, regional lung volume distribution, airway resistance, and lung gravitational gradient. Pulmonary mechanical properties are known to change with position, yet the extent to which driving pressure is altered and its clinical implications remain unclear.

The measurement of driving pressure plays a fundamental role in both open abdominal surgery and laparoscopic surgery, as they induce distinct alterations in lung mechanical properties. For instance, laparoscopic surgery leads to cephalic displacement of the diaphragm, increased airway pressure, decreased chest wall compliance, and altered lung volumes[7]. Pneumoperitoneum contributes to atelectasis and disrupts gas volume distribution in the lungs. While laparotomy also affects diaphragm function and increases the risk of atelectasis, it does so to a lesser extent than laparoscopy[8]. Patients undergoing major abdominal surgery experience improved intraoperative oxygenation and fewer PPCs, including atelectasis, when PEEP is adjusted to minimize driving pressure[9,10]. During pneumoperitoneum, respiratory mechanical properties undergo changes, with rising intra-abdominal pressure resulting in a linear increase in driving pressure within the standard pneumoperitoneum pressure ranges[11]. Driving pressure-guided ventilation during laparoscopic surgery reduces postoperative atelectasis; however, its assessment remains controversial[12]. Robotic surgery, similar to laparoscopy, often requires more extreme conditions. Patients subjected to robotic surgery under the highest driving pressure have been shown to exhibit a higher incidence of PPCs[13].

Patients with obesity necessitate special consideration in noncardiac surgery settings. As emphasized by the authors, these patients typically have higher chest walls, lower or negative pleural transpulmonary pressures, and lower compliance. Obese patients often undergo laparoscopic surgery or are placed in the Trendelenburg position, both of which elevate abdominal pressure and compromise lung ventilation.

Pregnancy presents anesthesiologists a different pattern of physiological changes in lung mechanics. Late pregnancy is marked by reduced lung volume, increased airway resistance, and higher pulmonary elastance[14]. While protective mechanical ventilation appears to be the most commonly used technique[15], there is lack of data on whether driving pressure-guided ventilation improves PPCs. In addition, obstetric surgery carries a risk of cardiopulmonary complications, such as placental embolism, which are unique to this surgical context[16].

The complex correlation between the lungs and the brain is gaining attention, especially in critical care settings[17]. Protective ventilation using low tidal volumes is recognized as the standard strategy for acute brain injuries[18]. However, the impact of mechanical ventilation on neurosurgical patients without prior traumatic injuries, such as oncology patients, remains unknown. Mechanical ventilation is likely to influence the neurosurgical pathology, suggesting the need for future research to investigate the role of driving pressure in these patients and its implications.

Finally, coronavirus disease 2019 has helped raise awareness about the risk of VILI, prompting a reevaluation of perioperative management for mechanically ventilated patients undergoing surgery. Recent studies have shown that even in patients without severe acute respiratory syndrome coronavirus 2-related acute respiratory distress syndrome, driving pressure-guided ventilation reduces the incidence of PPCs in those undergoing elective general anesthesia[19,20].

In summary, the optimal ventilation strategy remains unclear, and we lack a comprehensive understanding of how volume and pressure affect patients during mechanical ventilation. It is well known that PEEP, driving pressure, and tidal volume are closely related, and optimizing them constitutes the best ventilatory strategy for the patients.

Notably, the emerging concept of mechanical power may provide more answers than the driving pressure. Mechanical power, which represents the energy transferred to the lungs during mechanical ventilation, could potentially serve as a biomarker for the risk of PPCs[21].

Increased awareness of the potential risk of VILI in the operating room should be compulsory for clinicians. Various surgical settings expose the patient to non-physiological changes that may compromise lung mechanics, requiring anesthesiologists to consider these factors. Although further studies are needed, monitoring ventilation and maintaining protective parameters remain the current recommendations.