ONE LUNG VENTILATION (OLV)-SEPARATION Why & How ? By Ahmed Ibrahim ; M.D. Prof.of Anaesthesia...

ONE LUNG VENTILATION (OLV)-SEPARATION

Why & How ?

ByAhmed Ibrahim ; M.D.Prof.of Anaesthesia

Ain Shams University

OLV means: separation of the two lungs each lung functions independently by preparation of the airway

OLV provides: protection of healthy lung from infected/bleeding one diversion of ventilation away from damaged airway or lung improved exposure of surgical field

OLV causes: more manipulation of airway, more damage significant physiologic change & easy development of hpoxaemia

Indications for OLV

ABSOLUTE

1. Isolation of one lung from the other to avoid spillage or contamination.

2. Control of the distribution of ventilation (fistula, cyst, T.B disruption…).

3. Unilateral bronchopulmonary lavage.

RELATIVE

1. Surgical exposure.

2. Postcardiopulmonary bypass status, after removal of totally occluding chronic unilateral pulmonary emboli.

OLV is achieved by either;

-Double lumen ETT (DLT)

-Bronchial blocker

-Endobronchial tube

Anatomy of the Tracheobronchial Tree

Features of DLT

RUL, right upper lobe; LUL, left upper lobe

Carlens DLT Robertshaw DLT

Different types of DLT

Carlens White Bryce Smith

Robertshaw

lumen hook + + - -side Lt Rt Lt & Rt Lt & Rt

Basic pattern of a Right-Sided DLT

Rt Lt

Lt

passage of the left-sided DLT

guide for Length and Size of DLT

Length of tube , For 170 cm height, tube depth of 29 cm For every 10 cm height change , 1 cm depth

change

Patient characteristics Tube size (Fr gauge) Tracheal width (mm):

18161514

41393735

Patient height4’ 6”-5’5”5’5”-5’10”5’11”-6’4”

35-3737-3939-41

Patient age (year)13-14

12108

3532

28 (lt only) 26 (lt only)

Check Position of Lt -DLT

Checklist for tracheal placementa. inflate tracheal cuffb. ventilate rapidly by handc. check that both lungs are being ventilatedd. If not, withdraw 2-3 cm & repeat

Checklist for Lt side a. inflate Lt cuff > 2ml b. ventilate and check bilateral breath sounds c. clamp Rt tube d. check unilateral (Lt) breath sounds

Checklist for Rt side a. clamp Lt tube b. check unilateral (Rt) breath sounds

Major Malpositions of a Lt- DLT

Both cuffs inflatedClamp Rt lumen

Both cuffs inflatedClamp Lt lumen

Deflate Lt cuffClamp Lt lumen

Left

None / Very minimal

left

Left

Right

Both

Both

None / Very minimal

Both

Right

None / Very minimal

Right

Breath Sounds Heard

Lt

To ensure correct position of DLT clinically :

breath sounds are- normal (not diminished) &- follow the expected unilateral pattern with unilateral clamping

the chest rises and falls in accordance with the breath sounds

the ventilated lung feels reasonably compliant

no leaks are present

respiratory gas moisture appears and disappears with each tidal ventilation

N.B even if the DLT is thought to be properly positioned by clinical signs, subsequent FOB may reveal an incidence of malposition ( 38 -78 %)

FOB picture of Lt - DLT

FOB picture of Rt DLT

Relationship of FOB Size to Adult DLT

FOB Size (mm)(OD)

Adult DLT Size (French)

Fit of FOB inside DLT

5.6 All sizes Does not fit

4.941393735

Easy passageModerately easy passageTight fit, need lubricant, hard pushDoes not fit

3.6–4.2 All sizes Easy passage

Other Methods to Check DLT Position Chest radiograph ;

may be more useful than conventional auscultation and clamping in some patients, but it is always less precise than FOB. The DLT must have radiopaque markers at the end of Rt and Lt lumina.

Comparison of capnography;waveform and ETCO2 from each lumen may reveal a marked discrepancy (different degree of ventilation).

Surgeon ; may be able to palpate, redirect or assist in changing DLT

position from within the chest (by deflecting the DLT away from the wrong lung, etc..).  

Adequacy for Sealing (air Bubble test )

Complications of DLT

impediment to arterial oxygenation for OLV

tracheobronchial tree disruption, due to -excessive volume and pressure in bronchial

balloon -inappropriate tube size-malposition

traumatic laryngitis (hook)

inadvertent suturing of the DLT

to avoid Tracheobronchial tree Disruption ;

1. Be cautious in patients with bronchial wall abnormalities.

2. Pick an appropriately sized tube.

3. Be sure that tube is not malpositioned ; Use FOB.

4. Avoid overinflation of endobronchial cuff.

5. Deflate endobronchial cuff during turning.

6. Inflate endobronchial cuff slowly.

7. Inflate endobronchial cuff with inspired gases.

8. Do not allow tube to move during turning.

Relative Contraindications to Use of DLT

full stomach (risk of aspiration);

lesion (stricture, tumor) along pathway of DLT (may be traumatized);

small patients;

anticipated difficult intubation; extremely critically ill patients who have a single-lumen tube

already in place and who will not tolerate being taken off mechanical ventilation and PEEP even for a short time;

patients having some combination of these problems.

Under these circumstances, it is still possible to separate the lungs by : -using a single-lumen tube + FOB placement of a bronchial blocker ; or -FOB placement of a single-lumen tube in a main stem bronchus.

Bronchial Blockers (With Single-Lumen Endotracheal Tubes)

Lung separation can be effectively achieved with the use of a single-lumen endotracheal tube and a FOB placed bronchial blocker.

Often necessary in children as DLTs are too large to be used in them. The smallest DLT available is a left-sided 26 Fr tube, which may be used in patients 8 -12 years old and weighing 25 -35 kg.

Balloon-tipped luminal catheters have the advantage of allowing suctioning and injection of oxygen down the central lumen.

Indications for Use of Bronchial Blockers

1st , limitations to DLT (severely distorted airway, small patients , anticipated difficult intubation)

2nd , to avoid a risky change of DLT to single-lumen tube • whenever postoperative ventilation is anticipated • in cases of thoracic spine surgery in which a thoracotomy in

the supine or LDP is followed by surgery in the prone position.

3rd , situations in which both lungs may need to be blocked (e.g., bilateral operations, indecisive surgeons).

Types of bronchial blockers

Univent bronchial blocker system

Arndt endobronchial blocker

Cohen Flexitip Endobronchial Blocker

BB independent of a single-lumen tube

Univent bronchial blocker system

steps of FOB-aided method of positioning the Univent bronchial blocker in lt main stem bronchus

One- or two-lung ventilation is achieved simply by inflating or deflating, respectively, the bronchial blocker balloon

Advantages of the Univent Bronchial Blocker Tube ( Relative to DLT )

1. Easier to insert and properly position.

2. Can be properly positioned during continuous ventilation and

in the lateral decubitus position.

3. No need to change the tube when turning from the supine to

prone position or for postoperative mechanical ventilation.

4. Selective blockade of some lobes of each lung.

5. Possible to apply CPAP to nonventilated operative lung.

Limitations to the Use of Univent Bronchial Blocker

LIMITATION SOLUTION1. Slow inflation time (a) Deflate BB cuff and administer +ve pressure

breath through the main single lumen;(b) carefully administer one short high pressure (20–30 psi) jet ventilation

2. Slow deflation time (a) Deflate BB cuff and compress and evacuate the lung through the main single lumen; (b) apply suction to BB lumen

3. Blockage of BB lumen ( blood, pus,..)

Suction, stylet, and then suction

4. High-pressure cuff Use just-seal volume of air

5. Leak in BB cuff Make sure BB cuff is subcarinal, increase inflation volume, rearrange surgical field

Arndt endobronchial blocker[Wire guided Endobronchial Blocker (WEB)]

Cohen Flexitip Endobronchial Blocker

Bronchial Blockers that are Independent of a Single-Lumen Tube

Adults-Fogarty (embolectomy) catheter with a 3 ml balloon.

It includes a stylet so that it is possible to place a curvature at the distal tip to facilitate entry into the larynx and either mainstem bronchus .

-balloon-tipped luminal catheters (such as Foley type) may be used as bronchial blockers. Very small children (10 kg or less)

- Fogarty catheter with a 0.5 ml balloon

- Swan-Ganz catheter (1 ml balloon)  

* these catheters have to be positioned under direct vision; a FOB method is perfectly acceptable; the FOB outside diameter must be approximately 2 mm to fit inside the endotracheal tube (3 mm internal diameter or greater). Otherwise, the bronchial blocker must be situated with a rigid bronchoscope.

* Paediatric patients of intermediate size require intermediate size occlusion catheters and judgment on the mode of placement (i.e., via rigid versus FOB).

Lung separation with a single-lumen tube, FOB, and Rt lung bronchial blocker

Disadvantages of a blocker that is independent of the single-lumen tube as compared with DLT

inability to suction and/or to ventilate the lung distal to the blocker.

increased placement time. the definite need for a fiberoptic or rigid

bronchoscope. if bronchial blocker backs out into the trachea,

the seal between the two lungs will be lost and the trachea will be at least partially obstructed by the blocker, and ventilation will be greatly impaired.

Endobronchial Intubation with Single-Lumen Tubes

In adults, is often the easiest, quickest way for lung separation in patients presenting with haemoptysis , either

-blind, or -FOB , or-guidance by surgeon from within chest

In children it may be the simplest way to achieve OLV

Disadvantages-inability to do suctioning or ventilation of operative side.-difficult positioning bronchial cuff with inadequate ventilation of

Rt upper lobe after Rt endobronchial intubation.

In summary,

DLT is the method of choice for lung separation in most adult patients. The precise location can be determined by FOB . In situations where insertion of a DLT may be difficult and/or dangerous, separating the lungs is achieved either with a single-lumen tube alone or in combination with a bronchial blocker (e.g., the Univent tube).

Therefore, regardless of what method of lung separation chosen, there is a real need of a small-diameter FOB (for checking the position of the DLT, placing a single-lumen tube in a mainstem bronchus, and placing a bronchial blocker) .

Physiology of OLV (Arterial Oxygenation and Carbon Dioxide Elimination)

Blood passing through : : non ventilated lung ,non ventilated lung , retains CO2 and does not take O2. over ventilated lung ,over ventilated lung , gives off more than a normal amount of CO2

but cannot take up a proportionately increased amount of O2 .

Thus, during one-lung ventilation

more decreased oxygenation than during two-lung

ventilation in LDP due to an obligatory Rt-Lt transpulmonary

shunt through the nonventilated nondependent lung.

Consequently, lower PaO2 & larger P(A-a)O2

usually carbon dioxide elimination is not a problem; but

retention of CO2 by blood traversing the nonventilated lung

slightly exceeds the increased elimination of CO2 from blood

traversing the ventilated lung, and the PaCO2 will usually

slowly increase and P(A-a)CO2 decreases .

Two-lung ventilation versus OLV

during OLV, the nonventilated lung has some blood flow and therefore has an obligatory shunt, which is not present during two-lung ventilation & is the most important reason for increased P(A-a)O2.

Blood Flow distribution during OLV

The major determinants of blood flow distribution between both lungs :

•gravity,

•amount of lung disease,

•magnitude HPV,

•surgical interference nondependent ,

•ventilation mode dependent

Blood Flow Distribution During OLV , cont….

Lung condition (amount of lung disease)

*severely diseased nondependent lung, may have a fixed reduction in blood flow preoperatively and its collapse may not cause much increase in shunt.

*increases in PVR in dependent ventilated lung decreases its ability to accept redistributed blood from the hypoxic lung. This may occur in case of :

-decreasing FIO2 in the dependent lung .

-decreasing temperature .

Also, development of a hypoxic compartment (area of low V/Q and atelectasis) in the dependent lung increases its PVR (HPV), thereby decreasing dependent lung and increasing nondependent lung blood flow.

This may develop intraoperatively for several reasons:

1. in LDP ,ventilated dependent lung usually hasa reduced volume resulting from combined factorsof induction of anaesthesia and circumferentialcompression by mediastinum ,abdominal contents, and suboptimal positioning effects (rolls, packs, supports).

2. absorption atelectasis can occur in regions with low V/Q when they are

exposed to high FIO2 .

3. difficulty in secretion removal .

4.maintaining the LDP for prolonged periods may cause fluid to transude into the dependent lung and cause further decrease in lung volume and increase in airway closure.  

Blood Flow Distribution During OLV , cont….

Blood Flow Distribution During OLV , cont.

Surgical interference(compression ,retraction and ligation of pulmonary vessels during pulmonary resection) of the nondependent lung may further passively reduce its blood flow.

Mode of ventilation of dependent lung• If hyperventilated PaCO2 HPV

• Excessive AWP (PEEP or VT ) dependent PVR and nondependent lung blood flow.

• FIO2 -VD in dependent lung, augmenting HPV in nondependent lung

-but ,may cause absorption atelectasis in regions that have low V/Q ratios

Blood Flow Distribution During OLV , cont.

Magnitude of HPV

• HPV is an autoregulatory mechanism that protects the PaO2 by decreasing the amount of shunt flow that can occur through hypoxic lung as it diverts blood flow from the atelectatic lung toward the remaining normoxic or hyperoxic ventilated lung.

• HPV is of little importance When ;-very little of the lung is hypoxic (near 0%) because shunt will be small. -most of the lung is hypoxic (near 100%) there is no significant normoxic region to which the hypoxic region can divert flow.

• Of great importance if the percentage of hypoxic lung is intermediate ( 30 and 70%), which is the case during OLV

Factors that might determine the amount of regional HPV

Blood Flow Distribution During OLV , cont.

Factors that might determine the amount of regional HPV , cont.

1. Distribution of the alveolar hypoxia is probably not a determinant of the amount of HPV; all regions of the lung respond to alveolar hypoxia with vasoconstriction.

2. Atelectasis, most of blood flow reduction in acutely atelectatic lung is due to HPV and none of it to passive mechanical factors (such as vessel tortuosity).

3. Vasodilator drugs, most of them inhibit regional HPV

4. Anaesthetic drugs

5. Pulmonary vascular pressure, HPV response is-maximal at normal PVP and -decreased at either high or low PVP.

6. Pv¯O2 , HPV response also is -maximal when Pv¯O2 is normal and -decreased by either high or low Pv¯O2.

7. FIO2 selectively decreasing the FIO2 in the normoxic compartment causes an increase

in normoxic lung vascular tone, thereby decreasing blood flow diversion from hypoxic to normoxic lung.

8. Vasoconstrictor drugs constrict normoxic lung vessels preferentially, thereby disproportionately increasing normoxic lung   PVR causing decrease normoxic lung blood flow and increase atelectatic lung blood flow.

9. PaCO2 , hypocapnia inhibits & hypercapnia directly enhances regional HPV. 10. PEEP 

Other Causes of Hypoxaemia During OLV

Failure of the oxygen supply.

Gross hypoventilation of the dependent lung.

Blockage of the dependent lung airway lumen e.g. by secretions

Malposition of the DLT Decrease of Pv¯O2 (decreased cardiac output, increased

oxygen consumption [excessive sympathetic nervous system stimulation, hyperthermia, shivering])

  Transfusion of blood may cause pulmonary dysfunction

attributed to the action of isoantibodies against leukocytes, which causes cellular aggregation, microvascular occlusion, and capillary leakage.

Ventilatory Management of OLV

Conventional Ventilatory Management

Differential Lung Ventilation Management

High-Frequency Ventilation Management

Low-Flow Apnoeic Ventilation (Apnoeic Insufflation)

Conventional Ventilatory Management

•Maintain two-lung ventilation as long as possible.

•Use FIO2 = 1.0

•Begin OLV with tidal volume of 10 ml / kg.

•Adjust respiratory rate so that PaCO2 ~ 40 mmHg.

•Continuous monitoring of oxygenation and ventilation.

Differential Lung Ventilation Management

Intermittent Inflation of the Nondependent Operative Lung may be expected to increase PaO2 for a variable period of time.

Selective Dependent Lung PEEP

Selective Nondependent Lung CPAP (without tidal ventilation)

Differential Lung PEEP/CPAP

Selective PEEP to dependent lung improves V/Q but also increases PVR in it ; this diverts blood and increases shunt flow through, the nonventilated lung.

Dependent lung is ventilated but compressed by : Mediastinum , Diaphragm P ( rolls, packs, shoulder supports) .The nondependent lung is nonventilated , and blood flow through it is a shunt flow.

Selective CPAP to nondependent lung permits oxygen uptake from it ; Even if CPAP causes a rise in

PVR and diverts blood to dependent lung, the diverted blood flow can still participate in gas exchange in the

ventilated dependent lung that greatly increases PaO2

Differential lung CPAP (nondependent) /PEEP (dependent), wherever blood goes, both lungs can participate in O2 uptake. With this pattern, PaO2 can be restored to levels near those achieved by two-lung ventilation.

CPAP is created by the free flow of oxygen into the lung versus the restricted outflow of oxygen from the lung by the pressure relief valve.

The three essential components of a nondependent lung CPAP system

The Mallinckrodt Broncho-Cath CPAP System(Photography courtesy of Mallinckrodt Medical, Inc., St. Louis, MO.)

Recommended Combined Conventional and Differential Lung Management of OLV

1. Maintain two-lung ventilation until pleura is opened

2. Dependant lung• FIO2 = 1.0

• VT = 10 ml / Kg

• RR , so that PaCO2 ~ 40 mmHg

• PEEP = 5 - 10 cmH2O

3. If severe hypoxaemia occurs • Check DLT position by FOB• Check haemodynamic status• Non dependant lung CPAP (5 - 10 cmH2O)

• Dependent lung PEEP• Intermittent two lung ventilation• Clamp pulmonary artery (pneumonectomy)

High-Frequency Ventilation (HFV) Management

HFV delivers , very small VT (<2 ml/kg) at high rates (60 - 2,400 breaths/min)

So,• can be delivered through very small catheters

• it decreases PAWP

So,

it may be uniquely useful in facilitating the performance of thoracic surgery in

the following three ways; -Use in Major Conducting Airway Surgery -Use in Bronchopleural Fistula -Use in Minimizing Movement of the Operative Field

TYPE OF TYPE OF HFVHFV

RATE/MINRATE/MIN TYPE OF TYPE OF VENTILATORVENTILATOR

GAS GAS ENTRAINMENENTRAINMEN

TT

INSPIRATIOINSPIRATIONN

EXHALATIOEXHALATIONN

HFPPHFPPVV

60–100 Volume No Active Passive

HFJVHFJV 100–400 Jet pulsation

Yes Active Passive

HFOVHFOV 400–2,400

Piston pump

Yes Active Active

HFIHFI 100-600 Rotating ball

Yes Active Passive

Types of HFV

Low-Flow Apnoeic Ventilation (Apnoeic Insufflation)

If ventilation is stopped during administration of 100 % O2 and airway is left connected to a fresh gas supply, O2 will be drawn into the lung by mass movement to replace the diffused O2 . There is usually no difficulty in maintaining an adequate PaO2 (especially if 5–10 cmH2O of CPAP is used) at least for 20 minutes .

If flow of O2 is relatively low (<0.1 L/kg/min) almost all CO2

produced is retained, and PaCO2 rises approximately 6 mmHg in the 1st minute and then 3 - 4 mmHg each minute thereafter .

Safe period < 10 min 

arterial oxygen saturation monitoring via pulse oximetry is mandatory.