DR. ARATI MOHAN BADGANDI

PROBLEMS OF OPEN CHEST AND PATHOPHYSIOLOGY OF

ONE-LUNG VENTILATION

INTRODUCTIONPrinciple of one lung ventilation is one lung for the

surgeon and one for the anesthetist.The collapsed lung gives good access to surgeon and

the uncollapsed lung is used by the anesthetist to oxygenate.

Originally One Lung Ventilation was carried out to prevent spillage of infected materials, mucous, tumour materials from diseased Lung to normal Lung during Lung Surgeries.

GALES and waters first reported the use of selective Lung Ventilation during thoracic surgeries in 1931.

1949 Carlens originated P.V.C disposable DLT. Rowbatham introduced a DLT in 1962.

ADVANTAGES OF OLVIndependent channel for ventilation and suctioning.Isolation of normal lung from diseased, thereby

preventing contamination by infected secretion, mucous, tumour materials.

Independent collapse of lung to be operated and reexpansion when needed.

Provides optional operating condition facilitating easy approach; retraction of affected area with minimal stretching and trauma to tissues.

Provides blood less field and shortens the duration of surgery.

Complete collapse of lung facilitates other surgeries - spinal, laproscopic assisted vagotomy, oesophageal.

Avoids complication of prone position.

INDICATIONS OF OLV

TECHNIQUES OF PROVIDING OLVIn general three techniques are used-1. DLT.(DOUBLE LUMEN TUBE).2. Bronchial Blockers(univent tubes)3. Single Luman Endobronchial tubes.Arterial hypoxemia is the main pathophysiological

change during OLV.

Pathophysiology in awake patient with closed chest in lateral decubitusDuring spontaneous ventilation the dependent lung

is better ventilated than the non-dependent one. On induction of GA with NM paralysis both lungs

move down on the pressure volume curve. Perfusion: Dependent lung better perfused.Blood flow to non dependent lung is decreased by

10% Rt lung Bf :45% (55%) Lt lung Bf :35% (45%)

PATHOPHYSIOLOGY IN Anesthetised PATIENT WITH closed chest IN LDP

Perfusion : induction of anesthesia does not cause any change in perfusion .

Ventilation : GA decreases FRC hence compliance Mediastinum rests on dependent lung thus impeding

expansion.Weight of abdominal contents pushing the diaphragm

impedes lower lung expansion.V/Q MISMATCH

Compression (with loss of FRC) of the dependent lung and restriction of its excursion (decrease in compliance) by the mediastinum.

Cephalad movement of the abdominal organs against the flaccid diaphragm, and exaggerated flexed position with chest rolls to free the axillary contents occurs in LDP.

The net result is that the non-dependent lung is better ventilated - FRC 1.5 times that of the dependent lung.

This leads to (V/Q) mismatching, as the dependent lung is better perfused and under ventilated and the non-dependent lung is under perfused and better ventilated.

Gravity has no significant effect on distribution of ventilation during IPPV in the lat. decubitus position.

PATHOPHYSIOLOGY OF ANAESTHETISED PATIENT WITH OPEN CHEST IN LDP

Perfusion : not altered (dependent> nondependent).Ventilation: upper lung is better ventilated as it is no

longer restricted by chest wall.When the non-dependent hemithorax is opened, there

is further increase in FRC and compliance of the non-dependent lung and a decrease of these parameters of the dependent lung with two-lung ventilation.

This causes further deterioration of ventilation perfusion mismatch.

When the non-dependent lung is collapsed, the blood flow to that lung is not oxygenated leading to increased P (A-a) O2 gradient and impaired oxygenation.

PATHOPHYSIOLOGY OF LDP & OLV- V/Q MISMATCH

V/Q Mismatch is due to creation of an OBLIGATORY RT TO LT TRANS PULMONARY SHUNT .

During 2 Lung Ventilation in LDP-60% of Cardiac Output (CO) goes to dependent Lung and 40% to Non dependent Lung

Normal Venous admixture is 10% and is equally shared(5%+5%) between two lungs.

So average percentage of CO participating in gaseous exchange in Non-dependent-Lung is 35%; and in dependent Lung in 55%.

In OLV: the dependent lung ventilated with whole of tidal volume and non-dependent lung in NOT Ventilated, but still perfused.

The result is creation of an obligatory R-L TRANS PULMONARY SHUNT through Non ventilated non dependent lung that is 35% of CO-not oxygenated .

Un-inhibited H.P.V. reduce 50% of blood flow to the NON-VENTILATED Lung - blood flow becomes 17.5% (35/2) and shunt will be also 17.5% only.

If this is added to 5% of existing shunt the total shunt in NON-VENTILATED Lung will be 22.5(17.5+5)%.

So altogether in OLV the shunt will be 27.5% (22.5+5) causing impairement optimal PaO2.

Other factors like absorption atelectasis due to circum ferential compression of dependent lung

Accumulation of secretion and fluid transudate (particularly in prolonge surgery and anesthesia) in dependent lung low V/Q and increase P(A-a) O2 gradient and impaired oxygenation.

Awake/closed chest Anesthetized

V-Q relationships in the anesthetized, open-chest and paralyzed patients in LDP

PHYSIOLOGY OF LDP & OLV- V/Q MISMATCH

RECTIFIED BY:Adequate ventilation to dependent lung- increase FIO2Adjustment of I:E (1:2) ratioRR to keep CO2 40mg Hg.(20% increase)Limiting Inspiratory flow and Expiratory airway

resistance (unchanged Minute Ventilation)Vigilent monitoring of peak inspiratory pressure.

Sao2,PETCO2 if possible ABG.Maintaining optimal COSuctioning of dependent lung as and when needed.

Avoiding Over enthusiastic Hyperventilation.

Hypoxemia in OLV

FRC REDUCTION is another important cause of hypoxemia.

Causes are-1. In LDP-Shifting intra abdominal content, causes

cephaled shift of Diaphragm reducing FRC.2. GA and the mechanical effects of ventilation.3. Weight of sagging Mediastinum4. Sub-optimal position of the patient with rolls and

packs on the operation table as shoulder support

Hypoxemia in OLV

CAN BE OPTIMISED BY:Vigilent Monitoring of vital parametersOptimal ventilatory settings of dependent lung so

that- inspiratory pressure not more than 30cm.PEEP to the ventilated lung to recruit collapsed under

ventilated alevoli of dependent lung will improve FRC/V/Q ratio and oxygenation

Hypoxemia in OLV

Application of CPAP to Non-Ventilated lung, increases oxygenation by improving V/Q ratio and

causing vasoconstriction; then diversion of perfused blood to dependent lung.

This can be possible only when there is no major leak of bronchial tre as not helpful with broncho plural fistula and massive pulmonary hemorrhage etc.,

Institution of both lung ventilation periodically in long surgical procedure.

Maintaining optimal CO through out the procedure.

HYPOXIC PULMONARY VASOCONSTRICTION HPV is an auto regulatory mechanism that maintain

Pao2 by decreasing amount shunt flow through hypoxic non ventilated lung.

HPV primarily occurs in pulmonary arterioles of 200µm diameter which are situated close to small bronchiole and alveoli.

Precise mechanism of HPV not known. Various theories have been put forth: Direct action on pulmonary smooth muscle cells,

sensed by mitochondrial electron transport chain ,reactive oxygen species(H2 O 2 superoxide ) acting as second messengers to increase calcium content resulting in vasoconstriction.

Endothelial derived products potentiate (eg:leucotrines) and attenuate (NO PGI2) HPV.

Factors determining HPV are:1. Distribution Hypoxia (in non ventilated lung) causing

vasoconstriction and directing CO to normoxic lung and reducing shunt fraction.

2. Atelectasis of non ventilated lung-causing increased PVR and vasoconstriction and direct blood flow to normoxic lung, then decreasing shunt traction.

3. Vasodilator drugs directly inhibits HPV but indirectly by decreasing CO and lower Pvo2 thereby producing potent stimulation of HPV in normoxic lung and offset HPV in the original hypoxia lung and results in no flood diversion from more obviously Hypoxia Lung.

4. Vasoconstrictors will preferentially constricts pulmonary vessels perfusing both lung segments and may direct blood to hypoxia lung due to vasoconstriction in normoxic lung vascular.

5. Selectively decreasing FiO2 in normoxic compartment (1 to .5 to .3) causes on increase in vascular resistance there by decreasing blood flow diversion from hypoxic lung to normoxic lung.

Diagram of the tracheo bronchial tree

DLTs, bronchial blockers, or single-lumen endobronchial tubes (SLTs)

Lung-Isolation Techniques

Carlens, a left-sided + a carinal hook

a right-sided Carlens tube

Bryce-Smith, no hook but a slotted cuff/Rt

Robertshaw, most widely used

1. Type:

All have two lumina/cuffs, one terminating in the trachea and the other in the mainstem bronchus

Right-sided or left-sided available

Available size: 26F, 28F, 32F ,35F, 37F, 39F, 41F.

Double lumen endotracheal tubes

Selection of Double-Lumen Tube Size Based on Adult Patients’ Sex and Height

SexHeight (cm) Size (Fr)

Female <160 (63 in.) * 35

Female >160 37

Male <170 (67 in.) † 39

Male >170 41

INDICATIONS FOR RT DLTs

*exophyptic tumour that compresses the entrance of lt

bronchus

*intraluminal tumour near entrance of lt bronchus

*lt-sided tracheo broncheal disruption

*descending thoracic aortic aneurysm compressing the main

stem bronchus.

Insert tip of tube through cords and immediately rotate 90 degrees in direction of bronchus you are aiming to intubate.

2. Advance tube until comes to a halt. (No xs force needed).

3. Inflate tracheal cuff until air leak disappears & check both lungs ventilate (just as you would a single lumen tube).

4. Clamp tracheal lumen & check that only opposite side of chest moves and has air entry. Remember to open cap on clamped side so air can escape and lung collapse. You should feel a ‘whoosh’ of air as lung collapses. Make sure your clamp is proximal to the open cap or you will have trapped the air in the lung.

5. Inflate bronchial cuff until no leak is heard via tracheal lumen. Need about 2 mls air

6. Repeat 4. By clamping bronchial lumen instead of tracheal.

7. Switch on ventilator and collapse lung to be operated on. Check you can achieve a reasonable tidal volume without excessive pressure and that the capnograph trace has not changed compared to 2-lung ventilation.

INSERTION TECHNIQUE

Bronchial blockers

These devices are either within a modified SLT as an enclosed bronchial

blocker (Torque Control Blocker Univent; Vitaid, Lewinston, NY) or are used

independently with a conventional SLT,

the Arndt wire-guided endobronchial blocker (Cook Critical Care, Bloomington, IN), Cohen tip-deflecting endobronchial blocker (Cook Critical Care, Bloomington, IN), and the Fuji Uniblocker (Vitaid, Lewinston, NY).

Bronchial blockers

Characteristics of the Cohen, Arndt, and Fuji Bronchial Blockers

 Cohen Blocker

Arndt BlockerFuji Uniblocker

Size 9 Fr 5 Fr, 7 Fr, and 9 Fr 5 Fr, 9 Fr

Balloon shape Spherical Spherical or elliptical Spherical

Guidance mechanism

Wheel device to deflect the tip

Nylon wire loop that is coupled with the fiberoptic bronchoscope

None, preshaped tip

Smallest recommended ETT for coaxial use

9 Fr (8.0 ETT)

5 Fr (4.5 ETT), 7 Fr (7.0 ETT), 9 Fr (8.0 ETT)

9 Fr (8.0 ETT)

Murphy eye Present Present in 9 Fr Not present

Center channel 1.6 mm ID 1.4 mm ID 2.0 mm ID

Arndt Endobronchial Blocker setInvented by Dr. Arndt, an anesthesiologistIdeal for diff intubation, pre-existing ETT and postop ventilation

needed Requires ETT > or = 8.0 mmSimilar problems as UniventInability to suction or ventilate the

blocked lung

It is useful when it is not possible to place a DLT or in situations where the patient has already been intubated with a single lumen tube.

It has the appearance of a hollow bougie with a cuff.

The blocker has a guidewire in its lumen, the end of which can be hooked over a bronchoscope so the blocker can be inserted under direct vision into the

lung that is to be collapsed.

This guidewire needs to be removed before air can be withdrawn from the blocker and hence collapse the lung.

A disadvantage is that once the guidewire on the device has been withdrawn,

it cannot be reinserted so the blocker cannot be reused or repositioned in

the patient.

INSERTION TECHNIQUE

Univent TubeDeveloped by Dr. InoueMovable blocker shaft in external lumen of a

single-lumen ET tubeEasier to insert and properly position than

DLT (diff airway, C-s injury, pedi or critical pts)

No need to change the tube for postop ventilation

Selective blockade of some lobes of the lung Suction and delivery CPAP to the blocked

lung

Bronchial blockers (BB)

Arndt

Cohen

Fuji

Size selection rarely an issue

Easily added to regular ETT

Allows ventilation during placementEasier placement in patients with difficult airways and in childrenPostoperative two-lung ventilation by withdrawing blockerSelective lobar lung isolation possibleCPAP to isolated lung possible

More time needed for positioning

Repositioning needed more oftenBronchoscope essential for positioning

Non optimal right lung isolation due to RUL anatomyBronchoscopy to isolated lung impossibleMinimal suction to isolated lungDifficult to alternate OLV to either lung

AdvantagesDisadvantages

Univent tube Same as BBsLess repositioning compared with BBs

Same as for BBsETT portion has higher air flow resistance than regular ETTETT portion has larger diameter than regular ETT

Endobronchial tube

Like regular ETTs, easier placement in patients with difficult airways

Longer than regular ETT

Short cuff designed for lung isolation

Bronchoscopy necessary for placement

Does not allow for bronchoscopy, suctioning or CPAP to isolated lung

Advantages disadvantages

Positioning

The majority of thoracic procedures are performed with the patient in

the lateral position, most often the lateral decubitus position, but,

depending on the surgical technique, a supine, semisupine, or semiprone

lateral position may be used .These lateral positions

have specific implications for the anesthesiologist.

Complications associated with positionDependent Arm (Compression Injuries)    Arm directly under thorax   Pressure on clavicle into retroclavicular space   Cervical rib   Caudal migration of thorax padding into the axilla *

Nondependent Arm (Stretch Injuries)

  

Lateral flexion of cervical spine

  

Excessive abduction of arm (>90%)

  

S emiprone or semisupine repositioning after arm fixed to

a support

Neurovascular Injuries Specific to the Lateral Position:

Dependent eye

Brachial plexusCirculation

 

Dependent ear pinna

Cervical spine in line with thoracic spine

Dependent arm:

Nondependent arm * :

Dependent and nondependent suprascapular nerves

Nondependent leg: sciatic nerve

Dependent leg:

Peroneal nerve

Circulation

Predictive post-operative respiratory asseament

Calculated asPreoperative FEV1 х(1-nosegmentsremoved/19)A PPOfev1 < 1 lt= retention of sputum <800ml= contrindication( vent dependent)<40%= perioperative complication.

ppoDLCO= PREOPERATIVE DLCOх( 1- no segments removed/19)

SUMMARY

On conclusion ventilation of One Lung with 100%O2, the application of CPAP to Non ventilated lung and intermittent positive pressure to dependent lung counter act any drug mediated effects of HPV and maintain PaO2.

So maintaining uninhibited HPV is very important for maintaining normal V/Q and Pao2.

THANKYOU