AHQ Anesthesia Review 6th Ed SAMPLE PAGES

Anesthesia HQ

Anesthesia Review for board preparation6th Edition

Anesthesia HQ!

©ANESTHESIA HQ 2009! 1

Copyright © 2003-2009 by The Sock Lake Group, LLC

Notice of RightsAll rights reserved. No part of this publication may be reproduced in any form or by any electronic or mechanical means, including photocopying, recording, information storage and retrieval systems and otherwise, without permission in writing from the publisher. For information on obtaining permission for reprints and excerpts, contact the Sock Lake Group, LLC.

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Find us on the World Wide Web at: http://www.anesthesiahq.com

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2! ©ANESTHESIA HQ 2009

Preface to the 6th Edition

My motivation in creating Anesthesia HQ was to create a concise and comprehensive anesthesia study guide and an interactive, online exam web site for those preparing for the anesthesia board exams. During the past several years, I!ve had the opportunity to assist many examinees prepare and pass their anesthesia board exams. It is with feedback and critical input from many that I am able to continue to improve the board preparation materials and the web site. This sixth edition of the study guide maintains my initial goal and with the combination of the website, www.anesthesiahq.com, offers a unique learning experience for those preparing for the anesthesia board exams.

The study guide is still organized by topics and chapters in an easy to read outline format, which also will provide you with the opportunity to add your own knowledge, thoughts, and comments throughout the review process. The study guide is intended as a supplement and an aid to your previous years of study, diligence, and hard work. From the moment you begin preparing for the anesthesia board exam, you should read, reread, and review again, all of the topics and information contained in the study guide, web site, and additional textbooks.

My goal is to provide you with the tools to prepare, organize, and ultimately pass the anesthesia board exams. I wish you good luck and success in your studies and career.

Michael K Loushin, MDFounderAnesthesia HQ

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Dedication

To my loving family and friends for their patience and understanding.

Anesthesia HQ!


Notice of Liability

The information contained herein is only to be used as a study aide in preparation for the anesthesia board exams. Such information is not to replace any medical education, clinical experiences, or the study of textbooks and medical journals. The actual use of this information, including any medical concepts, facts, drug dosages, and methods, therefore is at the reader!s own risk. We assume NO responsibility for any injury or damages to any person or property that may result from such reliance on or use of any of this information.

We have taken all reasonable precautions to confirm the accuracy of the information presented herein and to describe generally accepted practices. However, we are not responsible for any inaccuracies, errors, and/or omissions or for any consequences from the use or application of any of the information contained herein and make no promise or warranty, express or implied, with respect thereto.

We have taken all reasonable precautions to ensure that the drug selection and dosages set forth in this text are in accordance with recommendations and practice current at the time of writing. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is solely responsible for reviewing and following the package insert for each drug for any change in indications and dosage and for any warnings and precautions. This is particularly important when the recommended agent is a new or infrequently employed drug.

Some drugs and medical devices presented in this publication have Food and Drug Administration (FDA) clearance for limited use in restricted research settings. It therefore is the sole responsibility of the reader to ensure that the applicable health care provider has ascertained the FDA status of each drug or device planned for use in their clinical practice.

THE READER ASSUMES ANY AND ALL RISKS ASSOCIATED WITH THE ACTUAL USE AND/OR RELIANCE ON ANY OF THE INFORMATION CONTAINED HEREIN THAT DEVIATES IN ANY WAY FROM THE INTENDED PURPOSE OF SUCH INFORMATION AS ONLY A STUDY AIDE IN PREPARATION OF THE ANESTHESIA BOARD EXAMS. TO THE EXTENT THE READER ULTIMATELY RELIES ON AND/OR OTHERWISE USES ANY SUCH INFORMATION FOR ANY OTHER PURPOSE, WHETHER INTENDED OR OTHERWISE, THE READER AGREES TO INDEMNIFY AND HOLD US HARMLESS FROM ANY AND ALL INJURIES, DAMAGES, COSTS, FEES AND EXPENSES (INCLUDING ATTORNEYS! FEES AND EXPENSES) THAT MAY OR DOES IN ANY WAY RESULT FROM SUCH ACTUAL USE AND/OR RELIANCE.

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Table of Contents

Anesthesia Circuits and Machines" 13

Bellows" 25

Vaporizers" 29

Scavenger System" 37

E Cylinders" 43

Carbon Dioxide Absorbers" 47

Electricity " 51

Capnography " 57

Blood Pressure Monitoring" 69

Central Venous Pressure Monitoring" 77

Pulmonary Artery Catheter" 85

Cardiac Output & Cardiac Index Monitoring" 95

Pulse Oximetry " 101

Mixed Venous Saturation Monitoring" 105

Cardiac Pressure-Volume Curves" 109

Inhalational Anesthetics" 117

Neuromuscular Blockers" 133

Local Anesthetics" 145

Obstetric Anesthesia: An Overview " 153

Obstetric Emergencies" 163

Pre-eclampsia" 171

Fetal Heart Tracing" 175

Myocardial Ischemia & Myocardial Infarction" 185

Valvular Diseases" 195

Pacemakers & Automated Implantable Cardiovertor Defibrillators" 209

Anesthetic Management of Pacemakers & AICDs" 215

Cardiac Reflexes" 219

Heart Transplant" 221

Abdominal Aortic Aneurysm" 223

Thoracic Aortic Aneurysm" 229

Intra-aortic Balloon Pump" 235

Cardiopulmonary Bypass Circuit" 239

Respiratory: An Overview" 245

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Hypoxemia" 259

Pulmonary Embolism" 263

Thoracic Anesthesia" 265

Mediastinoscopy " 275

Cystic Fibrosis" 277

Obstructive & Restrictive" 279

Lung Diseases" 279

Aspiration" 289

Acid-Base: An Overview " 293

Metabolic Acidosis" 301

Metabolic Alkalosis" 307

Respiratory Acidosis" 311

Respiratory Alkalosis" 317

Alpha-stat & pH-stat" 319

Blood Gas Management" 319

Neuroanesthesia" 321

Evoked Potentials " 333

Carotid Endarterectomy " 337

Arnold-Chiari Malformation" 341

Venous Air Embolism" 343

Spine Anatomy " 347

Spinal Cord Injury & Spinal Shock" 355

Tourniquet Pain" 359

Pediatric Anesthesia & Physiology " 361

Congenital Heart Disease" 371

Congenital Diaphragmatic Hernia" 377

Necrotizing Enterocolitis" 379

Ligation of a Patent Ductus Arteriosus" 381

Pyloric Stenosis" 385

Retinopathy of Prematurity " 389

Tracheo-esophageal Fistula" 391

Gastroschisis & Omphalocele" 395

Extracorporeal Membrane Oxygenation" 397

Ophthalmology & Eye Physiology " 399

Retrobulbar Block" 405

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Perioperative Eye Injury " 407

Endocrine" 411

Thyroid Hormone" 415

Parathyroid Hormone" 423

Pheochromocytoma" 427

Obesity " 433

Liver Physiology " 437

Geriatrics " 441

Temperature Regulation during Anesthesia" 443

Malignant Hyperthermia" 449

Neuroleptic Malignant Syndrome" 453

TURP Syndrome" 455

Extracorporeal Shock Wave Lithotripsy " 459

Coagulopathies" 461

Hemoglobinopathies" 467

Porphyrias" 473

Scleroderma" 477

Scoliosis" 479

Parkinson!s Disease" 483

Systemic Lupus Erythematosus " 485

Osteogenesis Imperfecta" 489

Myotonic Dystrophy " 491

Muscular Dystrophy " 495

Multiple Sclerosis" 497

Myasthenia Gravis" 499

Myasthenic (Lambert-Eaton) Syndrome" 502

Guillain-Barre Syndrome" 505

Amyotrophic Lateral Sclerosis" 507

Carcinoid Syndrome" 509

Coexisting Diseases" 513

Airway & ENT" 519

Acute Epiglottitis" 525

Blood Transfusion" 527

Transfusion Reaction" 537

Isovolemic Hemodilution" 541

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Heparin-Induced Thrombocytopenia" 545

Chemotherapeutic" 547

& Immunosuppressant Drugs" 547

Electroconvulsive Therapy " 551

Burns" 555

Pain and Regional Anesthesia" 561

Intraoperative Awareness and Depth of Anesthesia" 583

Statistics " 585

Equations" 589

Anticholinergics " 599

Antiplatelets" 601

Barbiturates" 602

Benzodiazepines" 604

Beta Blockers" 606

Cholinesterase Inhibitors " 608

Clonidine" 610

Digoxin" 611

Dobutamine" 613

Dopamine" 614

Droperidol" 615

Ephedrine" 616

Epinephrine" 617

Etomidate" 618

Fenoldopam" 619

Fentanyl" 620

Glucagon" 621

H-2 Receptor Blockers" 622

Heparin" 623

Hydralazine" 624

Isoproterenol" 625

Ketamine" 626

Meperidine" 628

Metoclopramide" 629

Milrinone" 630

Morphine" 631

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Naloxone" 632

Nicardipine" 633

Nitric Oxide" 634

Nitroglycerin" 635

Nitroprusside" 636

Norepinephrine" 638

Phentolamine" 639

Phenylephrine" 640

Prazosin" 641

Propofol" 642

Succinylcholine" 644

Sufentanil & Remifentanil" 646

Sympathomimetics" 647

Trimethaphan" 648

Vasopressin" 649

Index" 653

Anesthesia HQ!


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! Anesthesia Circuits and Machines

A. Circle systems are complex anesthesia circuits where the components are arranged in a “circle”. Circle systems are utilized to prevent rebreathing of carbon dioxide (CO2) during low fresh gas flow. They also allow good conservation of respiratory heat and humidity.

B. Circle systems prevent rebreathing of carbon dioxide by means of a CO2 absorber. They allow rebreathing of exhaled gases (oxygen and anesthetic gases). A scavenger system removes any waste gases from the circle system.

C. A circle system can be semi-closed, semi-open, or closed.

1. Semi-open system does not allow rebreathing of gases and requires very high fresh gas flow rates.

2. Semi-closed system allows rebreathing of gases and can be used with low fresh gas flow rates.

3. Closed system allows rebreathing of gases, and the inspiratory and expiratory volumes are essentially matched. A semi-closed system can be converted into a closed system by closing the adjustable pressure limiting (APL) or “pop-off” valve.

D. A semi-closed system allows rebreathing of gases.

1. It is the most common anesthesia system used in the United States.

2. Due to circuit and multiple valves, a semi-closed system has more resistance to breathing during spontaneous ventilation.

3. Multiple valves are present in the breathing circuit of a semi-closed system.

4. Reservoir (breathing) bag is part of the breathing circuit.

5. With a semi-closed system, it is still possible to rebreathe CO2.

6. Administration of low fresh gas flow rate can be utilized with a semi-closed system.

E. A semi-open system does not allow rebreathing of gases and requires high fresh gas flow.

1. Mapleson systems are semi-open systems.

2. Semi-open systems are associated with increased loss of heat and humidity due to high fresh gas flow rates and absence of rebreathing.

3. It is difficult to scavenge waste gases with a semi-open system.

4. Since they do not contain valves, semi-open systems have less resistance to spontaneous breathing.

! Chapter: Anesthesia Circuits and Machines


F. A closed system has fresh inflow gas which nearly equals the amount of gas taken up by the patient.

1. The amount of inflow gas that needs to be replaced is the amount of oxygen consumed by the patient and the amount of anesthetic gas absorbed by the patient!s body and the anesthesia circuit.

2. There is complete rebreathing of gases (oxygen and inhalational anesthetic) after removal of CO2 by the carbon dioxide absorber.

3. There is no gas exiting through the scavenger.

4. The APL valve is also closed, preventing overflow of gases.

5. Some of the semi-closed systems may be turned into closed systems by turning the APL valve to the off/closed position.

6. Since there is nearly complete rebreathing of gases, a closed system offers maximum conservation of heat and humidity.

7. A change in gas concentration occurs very slowly, due to low fresh gas flows.

G. A circle system requires the following components.

1. Fresh gas inlet

2. Tubing for expiratory and inspiratory limbs

3. Reservoir (ventilating) bag

4. Adjustable pressure limiting (APL) valve

5. Unidirectional valves on expiratory and inspiratory limbs

6. Carbon dioxide absorber

7. Y-piece that connects the inspiratory and expiratory limbs of the circuit

Chapter: Anesthesia Circuits and Machines "


H. The components of the circle system may be arranged in multiple ways, but certain criteria must be met in order to prevent rebreathing of carbon dioxide.

1. The fresh gas inlet must be between the CO2 absorber and inspiratory valve. It cannot be on the expiratory limb.

2. The adjustable pressure limiting valve (APL) must be between the CO2 absorber and expiratory valve. It cannot be in the inspiratory limb.

3. The unidirectional valves must be present between the reservoir bag/bellows and the patient (Y-piece).

4. Other components of the circle system may have varying configurations.

I. Advantages of a circle system include the following:

1. Conservation of respiratory heat and humidity

2. Ability to scavenge waste gases

3. More constant concentration of inspired anesthetic gases

4. Allows administration of very low fresh gas flow without causing rebreathing CO2

5. Economical since it allows rebreathing of exhaled oxygen and volatile anesthetics



J. Disadvantages of a circle system include the following:

1. Greater potential for system leaks and disconnections

2. Risk of malfunctioning unidirectional valves (stuck open or closed)

3. Due to multiple valves and components of the anesthesia circuit, there is increased resistance and work of breathing during spontaneous ventilation.

K. During spontaneous ventilation with a circle system, the APL valve is fully open.

L. In a circle system, the ventilation dead space is distal to the Y–piece of the breathing circuit.

1. The length of the separate inspiratory and expiratory limbs of the tubing does not affect dead space caused by the anesthesia circuit.

2. For example, increasing the length of the inspiratory and expiratory limbs does not increase the dead space distal to the Y-piece.

M. The compliance of the circuit tubing will affect the tidal volume that is delivered to the patient. A portion of a set tidal volume can be lost to distending the circuit tubing.

1. A less compliant tubing results in smaller distention of the circuit tubing with each inspiratory volume.

a. Pediatric and neonatal circuit tubing are less compliant. This minimizes the amount of tidal volume lost to distending the tubing with each delivered ventilation.

b. Anesthesia circuit tubing with low compliance should be used for neonates and infants.

2. For example, if the circuit tubing has a compliance of 5 mL/cm H2O, and the inspiratory pressure is 20 cm H2O, the amount of volume lost to distending the tubing is 100 mL (5 mL/cm H2O multiplied by 20 cm H2O).

a. One can see from the above example how tubing compliance can cause hypoventilation issues in small children and neonates. Depending on the compliance of the lungs, majority of the set tidal volume may be used to just distend the tubing.

b. Using the above example, let!s say a neonate required a tidal volume of 80 mL. Since 100 mL is lost to distending the tubing, the neonate may not receive any lung ventilation. Instead, the set tidal volume would only distend the circuit tubing.

3. Some of the newer anesthesia machines compensate for tubing compliance. The compensatory mechanism allows better matching of set tidal volume to actual delivered tidal volume.

N. Oxygen flush valve is connected inline with the inspiratory limb of the breathing circuit.

1. When the oxygen flush valve is open, fresh gas (oxygen) flows at approximately 50 psi and greater than 30 L/min.

2. Opening the oxygen flush valve can result in the following:



a. Dilute the concentration of an anesthetic gas delivered to the patient.

b. Acutely increase the fraction inspired oxygen (FIO2).

c. When the inspiratory valve is open, activating the oxygen flush valve can increase the risk of barotrauma and pneumothorax.



Mechanical Ventilation: Inspiration

• During mechanical inspiration, the bag/bellows switch is closed to the ventilator bag.

• The scavenger valve is closed during inspiration.

• The inspiratory valve is open.

• The expiratory valve is closed during inspiration.

• Gases from the bellows flows through the CO2 absorber prior to going to the patient.

• The fresh gas inlet also provides fresh oxygen and volatile anesthetics.



Mechanical Ventilation: Expiration

• During mechanical expiration, the bag/bellows switch is closed to the ventilator bag.

• The expiratory valve is open.

• The inspiratory valve is closed during expiration.

• Gases from the patient flow into the bellows.

• The fresh gas also provides the bellows with oxygen and volatile anesthetics.

• Once the ventilation bellows is filled, excess gases are vented to the scavenger.



Manual (Bag) Ventilation: Inspiration

• During manual (bag) ventilation, the bag/bellows switch is open to the ventilator bag and closed to the bellows.

• Once the ventilator bag fills with gases, the excess gases are vented to the scavenger by adjusting the APL valve.

• When the ventilator bag is squeezed, the gases flow through the CO2

absorber and to the patient.

• The fresh gas inlet provides additional oxygen and volatile anesthetics.

• Expiratory valve is closed during inspiration.



Manual (Bag) Ventilation: Expiration

• During manual (bag) ventilation, the bag/bellows switch is open to the ventilator bag and closed to the bellows.

• The exhaled gases from the patient fill the ventilator bag.

• The fresh gas inlet provides additional oxygen and volatile anesthetics to the ventilator bag.

• Once the ventilator bag is completely filled, excess gases are vented to the scavenger by adjusting the APL valve.

• Inspiratory valve is closed during expiration.



O. Currently used anesthesia machines have evolved from simple anesthesia delivery machines into complex ventilators with specialized anesthetic delivery mechanisms that are controlled by powerful computers.

1. Even with the evolution of the complex anesthesia machine, the basic components of an anesthesia machine have not significantly changed. The basic components include the following:

a. Gas supply (oxygen, nitrous oxide, air) is provided by central and E-cylinder sources.

b. Pressure regulators to control the supply of gases from the central and E-cylinder gas sources.

c. Multiple alarms and monitors

d. Gas flow meters

e. Anesthetic agent vaporizers

2. The central gas supply has a safety device called a diameter index safety system (DISS) that helps prevent connection of improper gas lines to the central gas supply source.

a. For example, the DISS helps prevent connection of the oxygen gas line to the nitrous oxide central gas supply. Connection of the nitrous oxide line to the oxygen central supply is also prohibited.

b. The central gas supply has a pressure around 45-55 psi.

3. All E-cylinders also have a safety system that helps prevent connection of the incorrect gas cylinder to the anesthesia machine. This is called the pin index safety system (PISS).

4. The pressure regulators in the anesthesia machine lower the pressure of the delivered gases prior to administration to the patient.

a. Low pressure system includes the components of the flow meters, control valves, and vaporizer to the common gas outlet to the patient.

b. Intermediate pressure system includes the down-regulated E-cylinders pressure (~45-50 psi) to the flow meters and control valves.

(1) Recall, the normal pressure from the oxygen E-cylinders is approximately 2200 psi and the nitrous oxide pressure is about 740 psi.

(2) The oxygen line from the high pressure wall supply is about 50 psi.

5. The fail-safe valve is one of the key safety components of an anesthesia machine. The purpose of the fail-safe valve is to help detect and protect from the delivery of hypoxic mixtures of gases. The 2000 ASTM F1850-00 standard requires the following



for all anesthesia machines: the delivered oxygen concentration shall not decrease below 19% at the common gas outlet; an alarm shall activate within five seconds when pressure decreases below manufacturers specified threshold. Current anesthesia machines have alarms that activate when the pressure falls below 30 psi. There are two types of fail-safe valves, depending on the manufacturer of the anesthesia machine.

a. The Datex Ohmeda anesthesia machines utilizes a pressure sensor shut off valve. With this system, the fail-safe valve is either open or closed. When the pressure of oxygen falls to a set threshold (20 psi), the valve closes and shuts off flow of all gases except oxygen to help detect and protect from the delivery of hypoxic mixture of gases.

(1) The Datex Ohmeda machines also have a second-stage oxygen regulator that allows flow of oxygen from the flow valve control to be constant when the pressure is greater than 12-14 psi.

b. The Drager anesthesia machines use a proportioning system called an oxygen failure protection device (OFPD).

(1) The proportioning system decreases the supply of nitrous oxide as the pressure of oxygen supply decreases. At a critical level, the nitrous oxide supply is shut off.

c. The fail-safe valve does not prevent the delivery of an hypoxic mixture of gases. The oxygen analyzer on the distal end of the anesthesia circuit is the last line of defense in detecting the delivery of hypoxic mixture of gases.

d. Recall that the fail-safe monitor is pressure sensitive and not flow sensitive.



Recommended Reading & Reference:Andrews, JJ, Inhaled Anesthetic Delivery Systems, Anesthesia 5th Edition (Miller R, ed),

Churchill Livingstone, Philadelphia, PA, p.174-206Clinical Anesthesia 3rd Edition (Barash P, Cullen B, Stoelting R, ed), Lippincott Williams &

Wilkins, Philadelphia, PA, p.551-554Miller!s Anesthesia 6th Edition (Miller R, ed), Churchill Livingstone, Philadelphia, PA, p.

273-316.



! E Cylinders

A. Anesthesia machines have backup gas cylinders (E cylinders). The E cylinders connect directly to an anesthesia machine and are available in the event of a central gas supply failure.

B. The intrinsic pressures of the E cylinders (oxygen ~2200 psi; nitrous oxide ~745 psi) are regulated down to approximately 45 psi by pressure regulators on the E cylinders and anesthesia machine.

1. The down-regulated E cylinder pressure is less than the central gas pressure, which allows preferential gas flow from the central gas source.

2. When the central gas pressure falls below 45 psi, the E cylinder gas becomes available to the anesthesia machine.

3. All E cylinders must be checked prior to each anesthetic.

C. The Pin Index Safety System (PISS) was developed to safeguard against connecting incorrect E cylinders to the anesthesia machine.

1. For example, an oxygen E cylinder cannot be easily connected to the E cylinder yolk for nitrous oxide on the anesthesia machine.

E cylinder Form Capacity (L)

Pressure (psi)

Color (USA)

Color (Intl) Critical Temp (C)

Oxygen Gas ~625~2000-220

0Green White -119

Nitrous Oxide

Liquid/Gas ~1600 ~745 Blue Blue 36

Air Gas ~625 ~2000 Yellow White + Black -140

Nitrogen Gas ~625 ~2000 Black Black -149

Carbon Dioxide

Liquid/Gas ~845 ~1600 Gray Gray 31

Helium Gas ~500~1600-200

0Brown Brown -268

D. Critical temperature for a gas is the temperature at which a gas can be liquefied under pressure. Above the critical temperature, a gas cannot be liquefied regardless of pressure; distinct gas and liquid states do not exist.

1. For example, the critical temperature for oxygen is –119o C. This means that oxygen can be liquefied under pressure if the temperature is colder than -119o. Above this temperature, it exists only as a gas.

! Chapter: E Cylinders


2. The critical temperature for nitrous oxide is 36o C. This explains why nitrous oxide exists as a liquid at room temperature.

E. Nitrous oxide exists as a liquid at room temperature and the volume of gas remaining in the cylinder is not proportional to the cylinder pressure.

1. The nitrous oxide tank pressure usually does not begin to decrease until the liquid is exhausted and only gas remains in the tank.

2. When only N2O gas exists in the tank, there is usually less than 400 L of gas remaining.

3. The most accurate way to determine remaining N2O volume is to weigh the E cylinder.

a. The tare weight (empty weight) is stamped on the cylinder.

b. The volume of nitrous oxide can be calculated by knowing the three components:

(1) the mass (g) of nitrous oxide in the cylinder,

(2) molecular weight of nitrous oxide (44 g/mol), and

(3) one mole of gas at standard temperature and pressure is 22.4L.

c. A simple estimate is that 1000g (1kg) of nitrous oxide is about 550 L of free gas at 20oC. (At STP, the volume would be about 512 L)

Nitrous Oxide E Cylinder Sample Calculation

A nitrous oxide E cylinder has a tare weight of 7 kg. The pressure gauge reads 740 psi and now weighs 8.8 kg. How many liters of nitrous oxide are remaining in the cylinder at standard temperature and pressure (STP)?

Three known components:- Mass of nitrous oxide = 1800 g (1.8 kg)- Molecular weight of nitrous oxide = 44 g/mol- One mole of nitrous oxide at STP = 22.4 L

Volume = (1800g/44g/mol) x 22.4 L/mol = 40.9 mol x 22.4 L/mol = 916 L at STP (standard temperature and pressure)

F. Boyle!s Law describes the relationship between pressure (P) and volume (V) of a gas.

1. At a constant mass of gas and temperature, the product of pressure and volume is constant (P1V1 = k).

2. As the volume of gas decreases, the pressure inside the E cylinder also decreases in proportion to the volume of gas.

Chapter: E Cylinders"


a. The exception is nitrous oxide, since it is both liquid and gas inside an E cylinder.

G. Charles! Law describes the relationship between volume and temperature. Charles! Law states that V/T = k at a constant pressure and quantity.

1. Under constant pressure and quantity, the volume of a gas varies directly with temperature (degrees Kelvin).

2. As the temperature of a gas increases, the volume also increases.

H. The Boyle!s and Charles! laws can be combined. The combined gas law is as follows: (P1V1)/T1 = (P2V2)/T2

I. Dalton!s Law states that total pressure is equal to the sum of the partial pressures.

J. Recall that standard temperature and pressure (STP) are assumed for these equations. The standard temperature is 273oK (0oC) and pressure is 14.7 psi. Normal room temperature is around 20oC or 293oK.

Gas LawsGas Laws

Boyle!s Law P1V1 = k

Charles! Law V1/T1 = k

Combined Gas Law P1V1/T1 = P2V2/T2

Ideal Gas Law PV = nRT

Dalton!s Law Ptotal = P1 + P2 + P3...+Pn

where P = pressure (atm), V = volume (liters), T = temperature (Kelvin), n = mol, R = gas constantwhere P = pressure (atm), V = volume (liters), T = temperature (Kelvin), n = mol, R = gas constant

Pressure ConversionsPressure Conversions

1 atm = 14.7 psi

14.7 psi = 760 mmHg

1 mmHg = 1.36 cm H2O

1 mole of gas =(at standard temperature and pressure)

22.4 L

! Chapter: E Cylinders


One can calculate the availability of a gas from an E cylinder by utilizing the the gas laws.

Oxygen E Cylinder Sample Calculation

A previously full oxygen E cylinder with an initial pressure of 2000 psi now reads 1000 psi. How long will the oxygen last when the patient is receiving 6 L/minute via a face mask?

P1V1 = P2V2

P1 = 1000 psiV1 = 5 L (approximate internal volume of an E cylinder)P2 = 14.7 psi (atmospheric pressure)V2 = needs to be solved with the above equation

V2 = (1000 psi x 5 L) / 14.7 psi = 340 L

Therefore, approximately 340 L of oxygen is remaining in the tank. The E cylinder oxygen source will last about 57 minutes (340 L divided by the flow rate, 6 L/min).

Recommended Reading & Reference:Andrews JJ, Delivery Systems for Inhaled Anesthetics, Clinical Anesthesia 3rd Edition (Barash

P, Cullen B, Stoelting R, ed), Lippincott Williams & Wilkins, Philadelphia, PA, p.535-537Clinical Anesthesiology 3rd Edition (Morgan G, Mikhail M, Murray M, ed), Lange Medical

Books/McGraw-Hill, New York, NY, p.16-19

Chapter: E Cylinders"


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