Independent Lung Ventilation (ILV) in ICU

There has been loss of interested in Independent Lung Ventilation (ILV) over the recent years. Reasons could be unfamiliarity with the technique, lack of guidelines or even publications. On the other side, we are faced with better accessibility of extra corporeal oxygenation modalities such as veno-venous extracorporeal membrane oxygenation (V-V ECMO) and extra corporeal CO2 removal (ECO2R).

With ILV specially designed double lumen endotracheal tubes (DLET) are used that enable separate lung ventilation using 2 ventilators. While single lumen ventilation is well known to anesthesiologist, its use together the use of ILV is seldom used in ICU. ILV can offer valuable rescue therapy for refractory hypoxemia in patients with predominantly unilateral lung injury especially in non ECMO centres or as a bridge to definite therapy (ECMO, surgery, bronchial artery embolisation etc).

It is shown that ILV improves aeration, oxygenation and CO2 clearance in patients with predominant unilateral lung injury as well as reduces

intrapulmonary shunt and eliminates inhomogeneity during mechanical ventilation (MV). Protective MV with 6 mL / kg Ideal Body Mass (IBM) will inevitably lead to over distention and hyperventilation ob uninjured lung leaving the injured lung under-distended or collapsed. Pendelluft phenomenon has been reported to be present in predominantly unilateral lung disease / injuries due to differences in time constants in lungs.

Unfortunately, there’s a lack of double blind multi central studies about the use of ILV. While using it, we rely on scarce body of evidence from the literature based ob observational data and case series, applying physiology principles and fallowing protective ventilation guidelines.

Key words: independent lung ventilation, ICU

For ILV specially designed DLET made of soft plastic or silicone are used. Some have special hook at the and (Carlen’s DLET) enabling positioning and securing its position at carina (Figure 1). DLETs for selective right and left main bronchus are available on the market, the latter being used predominantly as their positioning is much easier (Figure 2). While left-sided DLET can be successfully use for majority of cases, right sided are irreplaceable in some circumstances (tumor requiring sleeve resection, thoracic aorta aneurism, left sided pulmectomy). In ICU vast majority of patient requiring ILV can be adequately ventilated using left sided DLET.

Although DLETs are larger in diameter, separate lumens are smaller compared to single lumen ET and imminently leading to increased resistance (Table 2). Secretion clearance through DLETs is compromised due to various factors.

Since tube is placed more distally, diminishing muco-ciliary clearance is present. Routinely used aspiration catheters are too short to pass all the way pass DLET into main bronchus. Secretion removal via bronchoscope is advised. Special care must be paid to secure sufficient ventilatory gas temperature and moisture. Active humidification instead of HME filters should be used at all times. Cuff pressure must be kept below 25 cm H2O. Frequent measurements

using manometer should be performed on each round.

T requires additional training, attention must be paid to adequate final rotation of the tube. The goal is separation of left and right distal airways thus proximal lumen should be opening into trachea while distal to the selected bronchus (Figure 2). Specially designed Airtraq is available to facilitate intubation with DLET. In case of reintubation bougies can be used.

Adequate DLET positioning in the ICU should always be confirmed bronchoscopically as auscultation for breath sounds or X ray can be misleading in up to 40% of cases. Pediatric or specially designed thin bronchoscopes are needed.

After DLET position is confirmed, non-selected ventilation via both lumens or separated ventilation can be started. If non separate ventilation is desired (ie during process of weaning) DLET should be attached to the ventilator via connector and distal (bronchial) cuff deflated. In the case of ILV, 2 separate ventilators are connected each to separate DLET lumens with DLET cuffs inflated (Figure 3).

Ventilators can be synchronized in which case the frequency is identical while FiO2, Vt and PEEP vary, or a-synchronized where all of the ventilator parameters vary. For synchronization some ventilators employ special

connecting cables introducing concept of “the master” and “the slave” ventilator (for example Dräger). The master ventilator automatically synchronizes the slave ventilator. Worth noting, in this clinical setting both ventilators should be the same type. Ventilators from other companies (Medtronic, Heinen + Löwenstein) can be synchronized by simultaneous pressing “manual inspiration” key. In case of asynchronous ILV any 2 ventilators or ventilatory modes can be chosen.

The primary aim of ILV is improvement in oxygenation while preventing (additional) ventilatory associated lung injury (VALI). Secondary aim is to try to prevent unilateral disease to spread bilaterally (bronchially drained lung abscess or tuberculoma, unilateral hemorrhage). Some intensivists advocate synchronization while others claim that ventilatory settings should be individualized according to particular lung side and underlying condition. In our centre individualized approach to ILV is applied.

According to scarce literature data synchronization does not affect hemodynamics or oxygenation. Besides, taking into account pathophysiology of unilateral lung injury synchronization does not make much sense.

There is no general agreement on which mode of ventilation (controlled, assisted spontaneous) or type ob breaths (volume vs pressure) to use. At our ICU Bi-Level mode is used, PEEP and FiO2 being selected according to

ARDSnet / Berlin ARDS definition recommendation, while pplato is

maintained below 30 cm H2O and respiraratory rate (RR) is set to optimize CO2 removal while maintaining pH > 7.10. Usually RR is kept below 28 breaths

per minute with inspiration to expiration ratio (I : E) < 1 : 1. Vt in uninjured lungs should be kept within 3 – 4 mL / kg IBW, while in the injured lung Vt is initially set to 2 mL / kg IBW and then titrated accordingly not to exceed pplato of 30 cm H2O. Respiratory rate in the diseased lung is set to 10/min, I : E is set

to > 2 : 1, working pressure (pplato – PEEP) to < 15 cm H2O (Table 3). At the

time, there is no data on transpulmonary pressure guided ventilation using esophageal catheter.

Recruitment maneuvers are recommended unless broncho-pleural fistula or undrained pneumothorax is present. Some authors use pressure support ventilation (PSV) with PEEP in the injured lung. Again, no high quality data exist on the subject.

Deep sedation (RASS -5) with analgesia and in case of severe ARDS 48 hrs trial of paralysis with cis-atracurium in needed. Sedation with volatiles using Anaconda can be used as well as propofol. We strongly discourage the use of benzodiazepines as they have prolonged action due to accumulation and active metabolite formation. Worth noting, benzodiazepines have strong causative effect in delirium development. We recommend sufentanyl or remifentanyl as analgesic given the favourable pharmacokinetic properties. The use of morphine should be discouraged due to long half live and active metabolites.

In the case of ventilator should be set in the manner that minimizes air leaks. As a general rule additional VALI must be avoided. Volume control ventilation in injured lungs is preferred over pressure control modes with PEEP and Vt set in the manner to minimize air leaks. If BPF is situated distally in the airways, by increasing maximal inspiratory flow (Ṽ), leaks might be decreased since inspiratory time will be decreased as well. However, in the case of proximal BPF, increasing Ṽ increases peak airway pressure and thus increases proximal leaks. Of note, in pressure modes, flow is non-operator setparameter.

With ILV multiple complications are described ranging from intubation related, to dislocation of the tube (Table 4). Of special notion is dislocation of the tube. It is well known that head and neck motion in patients intubated with single lumen ET displaces ET in the range 2 – 3 cm. Same range of movement is enough to dislodge tube distally into the main bronchus and or get displaced proximally into trachea. In either case ILV won’t be possible.

Daily evaluation should be performed on whether to continue ILV, wean the patent off ILV and starting conventional ventilation or increasing support with upgrade to VV ECMO. Attention should be payed to early recognition of ILV failure and upgrade to ECMO should be promptly performed unless there are absolute contraindications (ie. end stage malignoma, multiple end organ failure, known do not resuscitate (DNR) order etc).

As the patient’s respiratory failure improves conventional mechanical ventilation should be introduced. As mentioned before, improvement should be daily assessed (Table 5). Goal is to step wise increase ventilation in injured lungs until similar ventilatory settings are accomplished on both ventilators.

After patient remains stable reintubation with single lumen ET is performed.

As we previously reported total of 8 patients underwent ILV during 2010 and 2016 (0,9% of all ventilated patients). All patients had paO2/FiO2<200, all were ventilated in pressure modes (P-AC, BiLEVEL), ventilators were not synchronized – PEEP, RR, FiO2 and Vt were set individually for each ventilator

following blood gas results. Recruitment manuvers and NO were used at

physician’s discretion. In 5 patient’s oxygenation improved significantly within 2 hours of ILV. 2 patients were upgraded to V-V ECMO (Wegener’s, pneumonia), in 4 contraindications to ECMO was established. 3 patients died (lung carcinoma, emphysema, Wegener’s). All tube placements were confirmed radiologically, 1 intubation with double lumen tube was performed via bougie and proper placement confirmed bronhcoscopically. In all patients left sided double lumen tubes were used only. In one patient carinal decubitus was observed due to double lumen tube’s hook. Patients underwent ILV for median 4 days (range 2 – 10 days).

In severe single sided lung injury necessitating MV, ILV should be considered as it represents valuable adjunct in treating refractory hypoxemia. With lung separation both lungs can be ventilated according to protective ventilation strategy. Special care is needed to prevent tube dislocation, cuffs overinflation and trauma to larynx, trachea and bronchi. Since tubes’ lumens are narrower special attention to possible tube blockage must be paid. Daily reevaluation and conventional tube placement is warranted as soon as possible.

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