High-Frequency Jet Ventilation as an Alternative Method Compared to Conventional One-Lung Ventilation Using Double-Lumen Tubes During Minimally Invasive Coronary Artery Bypass Graft Surgery

Effects of one-lung flooding on porcine haemodynamics and gas exchange

Background and aim: We established a porcine model of one-lung flooding (OLF) that can be used for research on the use of ultrasound for lung tumour detection, ultrasound-guided transthoracic needle biopsy, and tumour ablation. However, OLF requires one-lung ventilation (OLV) and eliminates the recruitment strategies of the nonventilated lung. During thoracic surgery, OLV alone can be associated with hypoxia, hypercapnia, and right ventricular overload. Here, we examined whether OLF influences haemodynamics and gas exchange indices during and after OLV/OLF compared with OLV/apnoea and two-lung ventilation (TLV) following deflooding. Methods: Fourteen pigs were included in this study: five were allocated to the control group (CO) and nine were assigned to the OLF group (OLF). Assessments of haemodynamics, gas exchange, and lung sonography were performed after baseline measurements, during OLV/apnoea, OLV/OLF, and after deflooding and TLV. The volume of extravascular lung water was also measured. Results: OLF induced no significant deterioration of oxygenation or ventilation during OLF or after deflooding and TLV. Color-coded duplex sonography of the pulmonary artery in the flooded lung demonstrated an oscillating flow that corresponded to intrapulmonary circulatory arrest. After flooding of the nonventilated lung, the partial pressure of O₂ in the arterial blood increased and the shunt fraction decreased significantly compared to OLV/apnoea conditions. After deflooding and TLV, haemodynamics and gas exchange indices showed no differences compared to the CO group and baseline values, respectively. Conclusions: OLF is safe to use during acute animal experimentation. No clinically relevant deterioration of haemodynamics or gas exchange occurred during or after OLF. Due to the circulatory arrest in the flooded lung, the right-to-left shunt volume in the nonventilated lung was minimized. Survival experiments are necessary to further assess the utility of this method.

Thoracotomy for emergency repair of iatrogenic tracheal rupture: single center analysis of perioperative management and outcomes

Background

Iatrogenic tracheal ruptures are rare but life-threatening airway complications that often require surgical repair. Data on perioperative vital functions and anesthetic regimes are scarce. The goal of this study was to explore comorbidity, perioperative management, complications and outcomes of patients undergoing thoracotomy for surgical repair.

Methods

We retrospectively evaluated adult patients who required right thoracotomy for emergency surgical repair of iatrogenic posterior tracheal ruptures and were admitted to a university hospital over a 15-year period (2004–2018). The analyses included demographic, diagnostic, management and outcome data on preinjury morbidity and perioperative complications.

Results

Thirty-five patients who met the inclusion criteria were analyzed. All but two patients (96%) presented with critical underlying diseases and/or emergency tracheal intubations. The median time (interquartile range) from diagnosis to surgery was 0.3 (0.2–1.0) days. The durations of anesthesia, surgery and one-lung ventilation (OLV) were 172 (128–261) min, 100 (68–162) min, and 52 (40–99) min, respectively. The primary airway management approach to OLV was successful in only 12 patients (34%). Major complications during surgery were observed in 10 patients (29%). Four patients (11%) required cardiopulmonary resuscitation, one of whom received extracorporeal membrane oxygenation, and another one of these patients died during surgery. Major complications were associated with significantly higher all-cause 30-day mortality (p = 0.002) and adjusted mortality (p = 0.001) compared to patients with minor or no complications.

Conclusions

Surgical repair of iatrogenic tracheal ruptures requires advanced perioperative care in a specialized center due to high morbidity and potential complications. Airway management should include early anticipation of alternative OLV approaches to provide acceptable conditions for surgery.

Continuous Procedural Full-Lung Ventilation During Minimally Invasive Coronary Bypass Grafting

BACKGROUND

In the past, minimally invasive cardiac surgery (MICS)- coronary artery bypass graft surgery (CABG) alternatives have been introduced that dramatically reduce the invasiveness of standard operative procedures while still showing excellent clinical outcomes. However, in patients with high morbidity, reduced lung function impeding single-lung ventilation is one of the major concerns for MICS-CABG procedures, although those patients might reap the largest benefit from a procedure of reduced invasiveness.

METHODS

Here, we describe a simple surgical technique-the fan technique-that allows for continuous full-lung ventilation with unimpeded surgical view during common MICS-CABG procedures. To evaluate the procedural feasibility of this technique, we analyzed intraoperative ventilation measurements of 22 consecutive MICS-CABG patients in whom the fan technique was used.

RESULTS

This study demonstrates a significant improvement of standard respiratory measurements during procedural full-lung ventilation using the fan technique as compared with conventional single-lung ventilation (ventilation pressure 21.4 ± 3.2 versus 26.6 ± 3 mbar, p < 0.001; respiratory rate 13.1 ± 1.4 versus 14.4 ± 2.2 breaths per minute, p < 0.001; minute volume 7.4 ± 1.1 versus 6.2 ± 1 L/min, p < 0.0001; Pao₂ during ventilation 294.9 ± 74.6 versus 153.2 ± 71 mm Hg, p < 0.0001).

CONCLUSIONS

The presented technique may not only enable us to perform MICS-CABG procedures in patients not suitable for single-lung ventilation owing to reduced pulmonary function, but also may soon also become a standard procedure for MICS-CABG surgery, especially with regard to procedures involving complex and time-consuming multivessel revascularizations. However, further studies are strongly warranted to assess whether the fan technique may also decrease postoperative pulmonary complications and benefit clinical outcome indicators.

[Anesthesia in thoracic surgery]

Thoracic surgery represents a special challenge for anesthesia and requires a high level of human and material resources. Accurate knowledge of the pathophysiology is essential for selection of the anesthetic procedure, the separation of the lungs, monitoring and treatment of hemodynamics as well as for postoperative follow-up care. The increasing number of thoracic interventions and patients who are often suffering from complex diseases require close interdisciplinary cooperation between surgeons, anesthesiologists and intensive care specialists. In addition to the anesthetic techniques particular attention must be paid to the prevention of perioperative complications that can have a relevant effect on patient outcome. In particular hypoxemia during one-lung ventilation influences postoperative morbidity and mortality. Protective pulmonary ventilation strategies play an important role in prevention of postoperative acute lung injury.

Lung Injury After One-Lung Ventilation: A Review of the Pathophysiologic Mechanisms Affecting the Ventilated and the Collapsed Lung

Lung injury is the leading cause of death after thoracic surgery. Initially recognized after pneumonectomy, it has since been described after any period of 1-lung ventilation (OLV), even in the absence of lung resection. Overhydration and high tidal volumes were thought to be responsible at various points; however, it is now recognized that the pathophysiology is more complex and multifactorial. All causative mechanisms known to trigger ventilator-induced lung injury have been described in the OLV setting. The ventilated lung is exposed to high strain secondary to large, nonphysiologic tidal volumes and loss of the normal functional residual capacity. In addition, the ventilated lung experiences oxidative stress, as well as capillary shear stress because of hyperperfusion. Surgical manipulation and/or resection of the collapsed lung may induce lung injury. Re-expansion of the collapsed lung at the conclusion of OLV invariably induces duration-dependent, ischemia-reperfusion injury. Inflammatory cytokines are released in response to localized injury and may promote local and contralateral lung injury. Protective ventilation and volatile anesthesia lessen the degree of injury; however, increases in biochemical and histologic markers of lung injury appear unavoidable. The endothelial glycocalyx may represent a common pathway for lung injury creation during OLV, because it is damaged by most of the recognized lung injurious mechanisms. Experimental therapies to stabilize the endothelial glycocalyx may afford the ability to reduce lung injury in the future. In the interim, protective ventilation with tidal volumes of 4 to 5 mL/kg predicted body weight, positive end-expiratory pressure of 5 to 10 cm H2O, and routine lung recruitment should be used during OLV in an attempt to minimize harmful lung stress and strain. Additional strategies to reduce lung injury include routine volatile anesthesia and efforts to minimize OLV duration and hyperoxia.

Managing hypoxemia during minimally invasive thoracic surgery

An ever-increasing number of thoracic procedures are being performed through minimally invasive techniques. Although the incidence of hypoxemia during one-lung ventilation (OLV) has decreased over the years, it remains an issue in roughly 10% of cases. Algorithms for the management of OLV hypoxemia have to be adapted to the thoracoscopic approach, in particular the need for optimal surgical exposure. With appropriate planning and caution, most of the treatment modalities for OLV hypoxemia can be applied to the thoracoscopy setting, with some modifications.

Comparison of superimposed high-frequency jet ventilation with conventional jet ventilation for laryngeal surgery

BACKGROUND

New ventilators have simplified the use of supraglottic superimposed high-frequency jet ventilation (SHFJV(SG)), but it has not been systematically compared with other modes of jet ventilation (JV) in humans. We sought to investigate whether SHFJV(SG) would provide more effective ventilation compared with single-frequency JV techniques.

METHODS

A total of 16 patients undergoing minor laryngeal surgery under general anaesthesia were included. In each patient, four different JV techniques were applied in random order for 10-min periods: SHFJV(SG), supraglottic normal frequency (NFJV(SG)), supraglottic high frequency (HFJV(SG)), and infraglottic high-frequency jet ventilation (HFJV(IG)). Chest wall volume variations were continuously measured with opto-electronic plethysmography (OEP), intratracheal pressure was recorded and blood gases were measured.

RESULTS

Chest wall volumes were normalized to NFJV(SG) end-expiratory level. The increase in end-expiratory chest wall volume (EEV(CW)) was 239 (196) ml during SHFJV(SG) (P<0.05 compared with NFJV(SG)). EEV(CW) was 148 (145) and 44 (106) ml during HFJV(SG) and HFJV(IG), respectively (P<0.05 compared with SHFJV(SG)). Tidal volume (V(T)) during SHFJV(SG) was 269 (149) ml. V(T) was 229 (169) ml (P=1.00 compared with SHFJV(SG)), 145 (50) ml (P<0.05), and 110 (33) ml (P<0.01) during NFJV(SG), HFJV(SG), and HFJV(IG), respectively. Intratracheal pressures corresponded well to changes in both EEV(CW) and V(T). All JV modes resulted in adequate oxygenation. However, was lowest during HFJV(SG) [4.3 (1.3) kPa; P<0.01 compared with SHFJV(SG)].

CONCLUSION

SHFJV(SG) was associated with increased EEV(CW) and V(T) compared with the three other investigated JV modes. All four modes provided adequate ventilation and oxygenation, and thus can be used for uncomplicated laryngeal surgery in healthy patients with limited airway obstruction.

One-lung ventilation and arterial oxygenation

PURPOSE OF REVIEW

Hypoxemia during one-lung ventilation (OLV) has become less common; however, it may still occur in about 10% of cases. We review recent developments which may affect the incidence and treatment of hypoxemia during OLV.

RECENT FINDINGS

Changes in surgical techniques are affecting oxygenation during OLV. The increased use of the supine position may adversely affect the prevalence of hypoxemia, whereas the increased application of thoracoscopic techniques is limiting the treatment options. Treatment options such as global or selective recruitment maneuvers and drug effects of dexmedetomidine and epoprostenol on arterial oxygenation during OLV are discussed. Capnometry prior to, or early during OLV, may in fact be able to predict the degree of hypoxemia during OLV. Persistent controversies surrounding the effect of epidural anesthesia, ventilatory modalities and gravity are reviewed.

SUMMARY

Interesting concepts have emerged from case reports and small studies on the treatment and prediction of hypoxemia during OLV. Definitive studies on the most effective ventilatory mode remain elusive. End-organ effects of OLV are an exciting new concept that may shape clinical practice and research going forward.

Effects of Nondependent Lung Ventilation With Continuous Positive-Pressure Ventilation and High-Frequency Positive-Pressure Ventilation on Right-Ventricular Function During 1-Lung Ventilation

Background. The application of volume-controlled high frequency positive pressure ventilation (HFPPV) to the nondependent lung (NL) may have comparable effects to continuous positive airway pressure (CPAP) on the right ventricular (RV) function, oxygenation, and surgical conditions during one lung ventilation (OLV) for thoracotomy. Methods. After local ethics committee approval and informed consent, 75 patients scheduled for elective thoracotomy using OLV were randomly allocated to receive nondependent lung either CPAP 2 (CPAP2; n=25) or 5 (CPAP5; n=25) cm H2O pressure setting of the device or HFPPV using VT 3 mL-1, I: E ratio <0.3 and R.R 60/min (HFPPV; n=25), followed 15 min of OLV. Intraoperative changes in RV ejection fraction (REF), end-diastolic volume (RVEDVI) and stroke work (RVSWI), stroke volume (SVI), oxygen delivery (DO2), and uptake (VO2) indices and shunt fraction (Qs: Qt) were recorded without any surgical manipulation of the lung. Results. The application of NL-HFPPV resulted in improved REF by 33%, SVI and DO2 (P < 0.01) and reduced RVEDVI, RVSWI, PVRI, oxygen uptake, and shunt fraction by 24.8% (P < 0.01) than in the NL-CPAP groups. Conclusion. We concluded that the use of NL-HFPPV is a feasible option and offers improved RV function and oxygenation during OLV for open thoracotomy.