One-Lung Ventilation :One-Lung Ventilation Richard Serianni, MD Department of Anesthesiology NMCP


Objectives :Objectives Indication/contraindication of OLV Options for OLV Physiology Management of common problems


Introduction :Introduction One-lung ventilation, OLV, means separation of the two lungs and each lung functioning independently OLV provides: Protection of healthy lung from infected/bleeding one Diversion of ventilation from damaged airway or lung Improved exposure of surgical field OLV causes: More manipulation of airway, more damage Significant physiologic change and easily development of hypoxemia


Indication :Indication Absolute Isolation of one lung from the other to avoid spillage or contamination Infection Massive hemorrhage Control of the distribution of ventilation Bronchopleural fistula Bronchopleural cutaneous fistula Surgical opening of a major conducting airway giant unilateral lung cyst or bulla Tracheobronchial tree disruption Life-threatening hypoxemia due to unilateral lung disease Unilateral bronchopulmonary lavage


Indication (continued) :Indication (continued) Relative Surgical exposure ( high priority) Thoracic aortic aneurysm Pneumonectomy Upper lobectomy Mediastinal exposure Thoracoscopy Surgical exposure (low priority) Middle and lower lobectomies and subsegmental resections Esophageal surgery Thoracic spine procedure Minimal invasive cardiac surgery (MID-CABG, TMR) Postcardiopulmonary bypass status after removal of totally occluding chronic unilateral pulmonary emboli Severe hypoxemia due to unilateral lung disease


Options to Isolate Lung :Options to Isolate Lung Double-lumen endotracheal tube, DLT Single-lumen ET with a built-in bronchial blocker, Univent Tube Single-lumen ET with an isolated bronchial blocker Arndt (wire-guided) endobronchial blocker set Balloon-tipped luminal catheters Endobronchial intubation of a single-lumen ET


DLT :DLT Type: Carlens, a left-sided + a carinal hook White, a right-sided Carlens tube Bryce-Smith, no hook but a slotted cuff/Rt Robertshaw, most widely used 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: 41,39, 37, 35, 28 French (ID=6.5, 6.0, 5.5, 5.0 and 4.5 mm respectively)


Left DLT… :Left DLT… Most commonly used The bronchial lumen is longer, and a simple round opening and symmetric cuff Better margin of safety than Rt DLT Easy to apply suction and/or CPAP to either lung Easy to deflate lung Lower bronchial cuff volumes and pressures Can be used Left lung isolation: clamp bronchial + ventilate/ tracheal lumen Right lung isolation: clamp tracheal + ventilate/bronchial lumen


…Left DLT :…Left DLT More difficult to insert (size and curve, cuff) Risk of tube change and airway damage if kept in position for post-op ventilation Contraindication: Presence of lesion along DLT pathway Difficult/impossible conventional direct vision intubation Critically ill patients with single lumen tube in situ who cannot tolerate even a short period of off mechanical ventilation Full stomach or high risk of aspiration Patients, too small (<25-35kg) or too young (< 8-12 yrs)


Univent Tube... :Univent Tube... Developed by Dr. Inoue Movable blocker shaft in external lumen of a single-lumen ET tube Easier 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


...Univent Tube :...Univent Tube Slow deflation (need suction) and inflation (short PPV or jet ventilation) Blockage of bronchial blocker lumen Higher endobronchial cuff volumes +pressure (just-seal volume recommended) Higher rate of intraoperative leak in the blocker cuff Higher failure rate if the blocker advanced blindly


Arndt Endobronchial Blocker set :Arndt Endobronchial Blocker set Invented by Dr. Arndt, an anesthesiologist Ideal for diff intubation, pre-existing ETT and postop ventilation needed Requires ETT > or = 8.0 mm Similar problems as Univent Inability to suction or ventilate the blocked lung


Other Methods of OLV :Other Methods of OLV Single-lumen ETT with a balloon-tipped catheter Including Fogarty embolectomy catheter, Magill or Foley, and Swan-Ganz catheter (children < 10 kg) Not reliable and may be more time-consuming Inability to suction or ventilate the blocked lung Endobronchial intubation of single-lumen ETT The easiest and quickest way of separating one lung from the other bleeding one, esp. from left lung More often used for pedi patients More likely to cause serious hypoxemia or severe bronchial damage


Physiology of OLV :Physiology of OLV The principle physiologic change of OLV is the redistribution of lung perfusion between the ventilated (dependent) and blocked (nondependent) lung Many factors contribute to the lung perfusion, the major determinants of them are hypoxic pulmonary vasoconstriction, HPV and gravity.


Physiology :Physiology Upright position LDP, lateral decubitus position


Physiology of the Lateral Decubitus Position :Physiology of the Lateral Decubitus Position


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


Physiology of One Lung Ventilation and Causes of Hypoxemia :Physiology of One Lung Ventilation and Causes of Hypoxemia The non-dependent lung is not ventilated which causes mismatch of ventilation and perfusion (VA/Q) Blood flow to the non-dependent lung is shunt flow Causes an obligatory right to left shunt P(A-a)O2 gradient is larger and PaO2 is lower than in two lung ventilation


Physiology of One Lung Ventilation and the Lateral Decubitus Position :Physiology of One Lung Ventilation and the Lateral Decubitus Position Blood flow distribution in both lungs in the lateral decubitus position (LDP) Gravity causes a vertical gradient as in the upright position Blood flow is greater to the dependent lung


The Ventilation to Perfusion Ratio :The Ventilation to Perfusion Ratio VA/Q best expresses the amount of ventilation relative to perfusion in any given lung region At the base of the lung VA/Q approaches zero At the apex of the lung VA/Q approaches infinity (dividing by zero) PaO2 gradients are much higher than PaCO2 gradients due to VA/Q mismatching


Oxygen Transport and Causes of Hypoxemia :Oxygen Transport and Causes of Hypoxemia Shunt fraction (Qs/QT) Shunt refers to right to left diversion of pulmonary blood flow Blood does not get oxygenated Perfusion of underventilated alveoli Bronchial blood flow Intra-arterial and intra-cardiac shunts Increasing FiO2 when Qs/QT is greater than 50% is not helpful


Shunt and OLV :Shunt and OLV Physiological (postpulmonary) shunt About 2-5% CO, Accounting for normal A-aD02, 10-15 mmHg Including drainages from Thebesian veins of the heart The pulmonary bronchial veins Mediastinal and pleural veins Transpulmonary shunt increased due to continued perfusion of the atelectatic lung and A-aD02 may increase


HPV :HPV HPV, a local response of pulmonary artery smooth muscle, decreases blood flow to the area of lung where a low alveolar oxygen pressure is sensed. The mechanism of HPV is not completely understood. Vasoactive substances released by hypoxia or hypoxia itself (K+ channel) cause pulmonary artery smooth muscle contraction HPV aids in keeping a normal V/Q relationship by diversion of blood from underventilated areas, responsible for the most lung perfusion redistribution in OLV HPV is graded and limited, of greatest benefit when 30% to 70% of the lung is made hypoxic. But effective only when there are normoxic areas of the lung available to receive the diverted blood flow


Two-lung Ventilation and OLV :Two-lung Ventilation and OLV


Physiology of One Lung Ventilation and Causes of Hypoxemia :Physiology of One Lung Ventilation and Causes of Hypoxemia The non-dependent lung is not ventilated which causes mismatch of ventilation and perfusion (VA/Q) Blood flow to the non-dependent lung is shunt flow Causes an obligatory right to left shunt P(A-a)O2 gradient is larger and PaO2 is lower than in two lung ventilation


Physiology of One Lung Ventilation and the Lateral Decubitus Position :Physiology of One Lung Ventilation and the Lateral Decubitus Position During one lung ventilation blood flow to the non-dependent lung is decreased by 50 percent due to HPV Blood flow to the dependent lung is increased by 33 percent (from 60% to 80%) Ratio of non-dependent to dependent lung blood flow is 20% : 80% Shunt flow is therefore 20% and PaO2 is 280mm Hg (100% O2)


Management of OLV... :Management of OLV... Initial management of OLV anesthesia: Maintain two-lung ventilation as long as possible Use FIO2 = 1.0 Tidal volume, 10 ml/kg (8-12 ml/kg) Adjust RR (increasing 20-30%) to keep PaCO2 = 40 mmHg No PEEP (or very low PEEP, < 5 cm H2O) Continuous monitoring of oxygenation and ventilation (SpO2, ABG and ET CO2)


Physiology of One Lung Ventilation :Physiology of One Lung Ventilation Effects of anesthetics on HPV Inhaled anesthetics inhibit HPV experimentally Nitrous Oxide has only a small effect on HPV Injectable anesthetics have no effect Variability of effects experimentally likely related to the mechanism of HPV which is unknown Mechanism of HPV probably due to reaction of individual arterial smooth muscle cells to local O2 conditions


Physiology of One Lung Ventilation and Causes of Hypoxemia :Physiology of One Lung Ventilation and Causes of Hypoxemia Factors that decrease blood flow distribution to the non-dependent lung Surgical compression Retraction Ligation of pulmonary vessels Amount of disease in the non-dependent lung Hypoxic pulmonary vasoconstriction


Physiology of One Lung Ventilation in the Lateral Decubitus Position :Physiology of One Lung Ventilation in the Lateral Decubitus Position Distribution of perfusion Two lung ventilation One lung ventilation Distribution of ventilation Two lung ventilation One Lung ventilation


Physiology of One Lung Ventilation and Causes of Hypoxemia :Physiology of One Lung Ventilation and Causes of Hypoxemia Factors that increase blood flow distribution to the dependent lung Gravitational effects (zones of perfusion) Hypoxic pulmonary vasoconstriction in the non-dependent lung


Physiology of One Lung Ventilation in the Lateral Decubitus Position :Physiology of One Lung Ventilation in the Lateral Decubitus Position Effects of anesthetics on HPV Inhibition of HPV by 1 MAC isoflurane is about 21% Inhibition of HPV causes an increase in blood flow to the non-dependent lung of about 4% of total blood flow This 4% increase in shunt causes PaO2 to drop from 280 to 205 This 4% increase in shunt flow is not usually clinically detectable Inhaled anesthetics actually have little clinical effect on HPV


...Management of OLV :...Management of OLV If severe hypoxemia occurs, following steps be taken Check DLT position with FOB Check hemodynamic status CPAP (5-10 cm H2O, 5 L/min) to nondependent lung, most effective PEEP (5-10 cm H2O) to dependent lung, least effective Intermittent two-lung ventilation Clamp pulmonary artery ASAP Other causes of hypoxemia in OLV Mechanical failure of 02 supply or airway blockade Hypoventilation Resorption of residual 02 from the clamped lung Factors that decrease Sv02 (CO, 02 consumption)


Broncho-Cath CPAP System :Broncho-Cath CPAP System


Oxygen Transport and Causes of Hypoxemia :Oxygen Transport and Causes of Hypoxemia Calculation of Shunt Fraction Fick Equation Qs/Qt=[Cco2 - Cao2] / [Cco2 - Cvo2] Cao2 = (1.39)(Hb)(%sat) + (0.003)(Pao2) Estimation using P(A-a)O2 P(A-a)O2 / 20 If cardiac output is normal and Pao2 is > 175


Causes of Hypoxemia During Anesthesia :Causes of Hypoxemia During Anesthesia Equipment malfunction Hypoventilation Hyperventilation Decreased FRC Decreased cardiac output Inhibition of HPV Increased right to left shunt


One Lung Ventilation and Causes of Hypoxemia :One Lung Ventilation and Causes of Hypoxemia Factors that decrease ventilation to the dependent lung Reduced lung volumes Absorption atelectasis Difficulty of secretion removal LDP for long period can increase transudation Increases in HPV


Treatment of Hypoxemia During One Lung Ventilation :Treatment of Hypoxemia During One Lung Ventilation Conventional management Increase FiO2 to dependent lung Helps to increase the PaO2 Causes vasodilation which increases blood flow to dependent lung Tidal volume of 10ml/kg and RR to keep CO2 at 40mm Hg Lower tidal volume can cause atelectasis Greater tidal volume may increase airway pressures Selective dependent lung PEEP


Treatment of Hypoxemia During One Lung Ventilation :Treatment of Hypoxemia During One Lung Ventilation Differential management of one lung ventilation Intermittent inflation of the non-dependent lung Selective dependent lung PEEP Selective non-dependent lung CPAP


Summary :Summary OLV widely used in cardiothoracic surgery Many methods can be used for OLV. Each of them have advantages + disadvantages. Optimal methods depends on indication, patient factors, equipment, skills + training FOB is the key equipment for OLV Principle physiologic change of OLV is the redistribution of pulmonary blood flow to keep an appropriate V/Q match Management of OLV is a challenge for the anesthesiologist, requiring knowledge, skill, vigilance, experience, and practice