Dead space during one-lung ventilation

Effects of starting one lung ventilation and applying individualized PEEP right after patients are placed in lateral decubitus position on intraoperative oxygenation for patients undergoing thoracoscopic pulmonary lobectomy: study protocol for a randomized controlled trial

BACKGROUND

For patients receiving one lung ventilation in thoracic surgery, numerous studies have proved the superiority of lung protective ventilation of low tidal volume combined with recruitment maneuvers (RM) and individualized PEEP. However, RM may lead to overinflation which aggravates lung injury and intrapulmonary shunt. According to CT results, atelectasis usually forms in gravity dependent lung regions, regardless of body position. So, during anesthesia induction in supine position, atelectasis usually forms in the dorsal parts of lungs, however, when patients are turned into lateral decubitus position, collapsed lung tissue in the dorsal parts would reexpand, while atelectasis would slowly reappear in the lower flank of the lung. We hypothesize that applying sufficient PEEP without RM before the formation of atelectasis in the lower flank of the lung may beas effective to prevent atelectasis and thus improve oxygenation as applying PEEP with RM.

METHODS

A total of 84 patients scheduled for elective pulmonary lobe resection necessitating one lung ventilation will be recruited and randomized totwo parallel groups. For all patients, one lung ventilation is initiated the right after patients are turned into lateral decubitus position. For patients in the study group, individualized PEEP titration is started the moment one lung ventilation is started, while patients in the control group will receive a recruitment maneuver followed by individualized PEEP titration after initiation of one lung ventilation. The primary endpoint will be oxygenation index measured at T4. Secondary endpoints will include intrapulmonary shunt, respiratory mechanics, PPCs, and hemodynamic indicators.

DISCUSSION

Numerous previous studies compared the effects of individualized PEEP applied alone with that applied in combination with RM on oxygenation index, PPCs, intrapulmonary shunt and respiratory mechanics after atelectasis was formed in patients receiving one lung ventilation during thoracoscopic surgery. In this study, we will apply individualized PEEP before the formation of atelectasis while not performing RM in patients allocated to the study group, and then we're going to observe its effects on the aspects mentioned above. The results of this trial will provide a ventilation strategy that may be conductive to improving intraoperative oxygenation and avoiding the detrimental effects of RM for patients receiving one lung ventilation.

TRIAL REGISTRATION

www.Chictr.org.cn ChiCTR2400080682. Registered on February 5, 2024.

A structured narrative review of clinical and experimental studies of the use of different positive end-expiratory pressure levels during thoracic surgery

OBJECTIVES

This study aimed to present a review on the general effects of different positive end-expiratory pressure (PEEP) levels during thoracic surgery by qualitatively categorizing the effects into detrimental, beneficial, and inconclusive.

DATA SOURCE

Literature search of Pubmed, CNKI, and Wanfang was made to find relative articles about PEEP levels during thoracic surgery. We used the following keywords as one-lung ventilation, PEEP, and thoracic surgery.

RESULTS

We divide the non-individualized PEEP value into five grades, that is, less than 5, 5, 5-10, 10, and more than 10 cmH₂ O, among which 5 cmH₂ O is the most commonly used in clinic at present to maintain alveolar dilatation and reduce the shunt fraction and the occurrence of atelectasis, whereas individualized PEEP, adjusted by test titration or imaging method to adapt to patients' personal characteristics, can effectively ameliorate intraoperative oxygenation and obtain optimal pulmonary compliance and better indexes relating to respiratory mechanics.

CONCLUSIONS

Available data suggest that PEEP might play an important role in one-lung ventilation, the understanding of which will help in exploring a simple and economical method to set the appropriate PEEP level.

Pulmonary levels of biomarkers for inflammation and lung injury in protective versus conventional one-lung ventilation for oesophagectomy: A randomised clinical trial

BACKGROUND

It is uncertain whether protective ventilation reduces ventilation-induced pulmonary inflammation and injury during one-lung ventilation.

OBJECTIVE

To compare intra-operative protective ventilation with conventional during oesophagectomy with respect to pulmonary levels of biomarkers for inflammation and lung injury.

DESIGN

Randomised clinical trial.

SETTING

Tertiary centre for oesophageal diseases.

PATIENTS

Twenty-nine patients scheduled for one-lung ventilation during oesophagectomy.

INTERVENTIONS

Low tidal volume (VT) of 6 ml kg predicted body weight (pbw) during two-lung ventilation and 3 ml kgpbw during one-lung ventilation with 5 cmH2O positive end expired pressure versus intermediate VT of 10 ml kgpbw during two-lung ventilation and 5 ml kgpbw body weight during one-lung ventilation with no positive end-expiratory pressure.

OUTCOME MEASURES

The primary outcome was the change in bronchoalveolar lavage (BAL) levels of preselected biomarkers for inflammation (TNF-α, IL-6 and IL-8) and lung injury (soluble Receptor for Advanced Glycation End-products, surfactant protein-D, Clara Cell protein 16 and Krebs von den Lungen 6), from start to end of ventilation.

RESULTS

Median [IQR] VT in the protective ventilation group (n = 13) was 6.0 [5.7 to 7.8] and 3.1 [3.0 to 3.6] ml kgpbw during two and one-lung ventilation; VT in the conventional ventilation group (n = 16) was 9.8 [7.0 to 10.1] and 5.2 [5.0 to 5.5] ml kgpbw during two and one-lung ventilation. BAL levels of biomarkers for inflammation increased from start to end of ventilation in both groups; levels of soluble Receptor for Advanced Glycation End-products, Clara Cell protein 16 and Krebs von den Lungen 6 did not change, while levels of surfactant protein-D decreased. Changes in BAL biomarkers levels were not significantly different between the two ventilation strategies.

CONCLUSION

Intra-operative protective ventilation compared with conventional ventilation does not affect changes in pulmonary levels of biomarkers for inflammation and lung injury in patients undergoing one-lung ventilation for oesophagectomy.

TRIAL REGISTRATION

The 'Low versus Conventional tidal volumes during one-lung ventilation for minimally invasive oesophagectomy trial' (LoCo) was registered at the Netherlands Trial Register (study identifier NTR 4391).

Application of alveolar recruitment strategy and positive end-expiratory pressure combined with autoflow in the one-lung ventilation during thoracic surgery in obese patients

Background

The present study aims to evaluate the influence of alveolar recruitment strategy (ARS) and positive end-expiratory pressure (PEEP) combined with autoflow on respiratory mechanics, the oxygen index (OI), pulmonary shut [Qs/Qt(%)], and the concentrations of IL-6 and TNF-α in venous blood after surgery in obese patients who experienced thoracic surgery with one-lung ventilation (OLV).

Methods

A total of 36 obese patients with ASAII-III degree, who experienced selective pulmonary lobectomy, were within 36-74 years old, and had a BMI of 30-40 kg/m², were randomly divided into two groups: control group (C group) and protective ventilation group (P group). In the P group, ARS was given once when OLV began. Then, ventilation at 7 mmHg of PEEP and autoflow were given. The P_peak before OLV (T₁), at 30 minutes after OLV (T₂), and at the 5 minutes after two-lung ventilation (TLV) (T₃), and the changes of P_plat and Cdyn were recorded. Then, arteriovenous blood was drawn at T₁, T₂, T₃ and T₄ (6 hours after the operation), blood-gas indicators, including SPO₂, PaCO₂ and PaO₂, were measured, and the value of Qs/Qt(%) was calculated. Afterwards, venous blood was collected at T₁ and T₅ (18 hours after surgery), and the concentrations of IL-6 and TNF-α were detected. The clinical pulmonary infection score (CPIS) was determined at the first day and seventh day after the operation.

Results

In both groups, Cdyn and OI decreased, while P_plat, P_peak and Qs/Qt(%) increased (P<0.05) at T₂, when compared with those at T₁. At T₂ and T₃, P_plat and P_peak decreased (P<0.05) in the P group, when compared with the C group. At T₂, T₃ and T₄, OI increased (P<0.05) in the P group, when compared with the C group. At T₂, T₃ and T₄, PaCO₂ and Qs/Qt(%) decreased in the P group, when compared with the C group. The concentrations of IL-6 and TNF-α decreased in the P group, when compared with the C group.

Conclusions

The ventilation model of ARS and PEEP combined with autoflow can better reduce airway pressure and the production of injurious inflammatory cytokines in blood in obese patients. Furthermore, it can reduce Qs/Qt during and at 6 hours after thoracotomy, improve OI and maintain the acid-base balance of the internal environment, which may be applied in clinical work. This brings new enlightenment and needs to be clarified through further studies.

Volumetric capnography: lessons from the past and current clinical applications

Dead space is an important component of ventilation–perfusion abnormalities. Measurement of dead space has diagnostic, prognostic and therapeutic applications. In the intensive care unit (ICU) dead space measurement can be used to guide therapy for patients with acute respiratory distress syndrome (ARDS); in the emergency department it can guide thrombolytic therapy for pulmonary embolism; in peri-operative patients it can indicate the success of recruitment maneuvers. A newly available technique called volumetric capnography (Vcap) allows measurement of physiological and alveolar dead space on a regular basis at the bedside. We discuss the components of dead space, explain important differences between the Bohr and Enghoff approaches, discuss the clinical significance of arterial to end-tidal CO₂ gradient and finally summarize potential clinical indications for Vcap measurements in the emergency room, operating room and ICU.

Adult patient with pulmonary agenesis: focusing on one-lung ventilation during general anesthesia

Congenital pulmonary agenesis is a rare condition with high mortality. Mechanical ventilation in these patients is challenging and there has no such case been reported in the literature. We reported a 61-year-old female with lung agenesis who presented to our hospital with pneumonia and pelvic mass. In the past, she had undergone repairing of atrial septal defect and mitral valve forming surgery at 6-year-old. Thereafter she had remained asymptomatic until this time of hospital admission. The patient underwent operation for the pelvic mass with one-lung ventilation (OLV) under general anesthesia. We highlighted the use of protective ventilation (PV) strategy during OLV.