Mechanical Ventilation Prelimes.indd 1 6/16/2015 4:20:52 PM Prelimes.indd 2 6/16/2015 4:20:52 PM Series Editors Anupam Sachdeva Krishan Chugh Ajay Gambhir Satinder Aneja AP Dubey Shyam Kukreja Guest Editors Sanjeev Kumar Krishan Chugh Soonu Udani New Delhi | London | Philadelphia | Panama The Health Sciences Publisher Mechanical Ventilation Prelimes.indd 3 6/16/2015 4:20:53 PM Jaypee Brothers Medical Publishers (P) Ltd Headquarters Jaypee Brothers Medical Publishers (P) Ltd 4838/24, Ansari Road, Daryaganj New Delhi 110 002, India Phone: +91-11-43574357 Fax: +91-11-43574314 Email: firstname.lastname@example.org Overseas O\ufffd ces J.P. 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Inquiries for bulk sales may be solicited at: firstname.lastname@example.org Mechanical Ventilation First Edition: 2015 ISBN: 978-93-5152-771-8 Printed at Prelimes.indd 4 6/16/2015 4:20:53 PM Contributors Amit Vij Sanjeev Kumar Vikas Taneja Manish Kori Prelimes.indd 5 6/16/2015 4:20:53 PM Prelimes.indd 6 6/16/2015 4:20:53 PM Preface Mechanical Ventilation, while not a primary treatment application for disease states, is an extremely valuable respiratory support system. Every Pediatrician, who is confronted with critically ill children, needs to be familiar with the basics of intubation, bag mask ventilation, and the principles of stabilisation and transfer of a child. With a growing number of independent Intensive Care Units in the country, the basic tools, language and culture of \u201cventilation\u201d has become rather widespread. Now there is a keen desire to move forward and \ufffd ne-tune old skills and learn new ones. \ufffd is workshop is designed with just that in mind. \ufffd e importance of using noninvasive ventilation, wherever feasible, will be emphasised. \ufffd is is actually seen as a step up rather than a step down in the intensivists\u2019 skill in ventilation technique. High frequency still exists in the armamentarium of the intensivist as a rescue measure, where advanced ventilation techniques are considered and shall be covered. Besides this, a number of advanced modes of ventilation have also come in with the sole purpose of making the ventilation gentle and avoid asynchrony. \ufffd e use of ventilatory graphics has also put us in a better position to understand the physiology and mechanics of patient ventilator interactions in the diseased lung. \ufffd is manual is intended for intensivists and pediatricians, who wish to delve into details. Special focus has been kept on ventilatory graphics, high frequency ventilation as well as noninvasive ventilation. We hope it meets with your expectations. Prelimes.indd 7 6/16/2015 4:20:53 PM Prelimes.indd 8 6/16/2015 4:20:53 PM Contents 1. Basics of Mechanical Ventilation 1 2. Pediatric Airways and Oxygen Delivery Devices 14 3. Disease Speci\ufffd c Ventilation 29 4. Interpretation of Graphic Displays on Ventilators 37 Amit Vij 5. High Frequency Ventilation 50 Sanjeev Kumar 6. Non-invasive Ventilation in Children 59 7. \u201cBubble CPAP\u201d for Neonates 64 8. Newer Modes of Ventilation 71 9. Humidi\ufffd cation and Mechanical Ventilation 86 10. Complications of Mechanical Ventilation 93 Vikas Taneja 11. Troubleshooting and Monitoring During Mechanical Ventilation 104 12. Extracorporeal Membrane Oxygenation 109 Manish Kori Prelimes.indd 9 6/16/2015 4:20:53 PM Applied Physiology of Ventilation Mechanical ventilation in children and neonates is different from adults. While basic principles of physics and gas flow apply to all age groups, anatomical and physiological differences play a significant role in selecting the type of ventilator as well as ventilatory modes and settings. The upper airway in infants is cephalad, funnel shaped with its narrowest area being at the subglottic region (at the level of cricoid ring as compared to the relatively tubular adult airway. Airway resistance increases inversely by 4th power of the radius; i.e. in an already small airway even 1 mm of edema or secretions will increase the airway resistance and turbulent flow markedly necessitating treatment of airway edema, suctioning of secretion, measures to control secretions. Low functional residual capacity (FRC: Volume of air in the lungs at end of expiration) reduces the oxygen reserve and hence the time that apnea can be tolerated by a child. Respirations are shallow and rapid due to predominant diaphragmatic breathing, and inadequate chest expansion due to the more horizontal alignment of the ribs in infancy giving less play in the bucket handle movement of the ribs during inspiration. Therefore, a child tends to get tachypneic rather than increasing the depth of respiration in response to hypoxemia. Oxygen consumption per kg body weight is higher therefore tolerance to hypoxemia is lower. Susceptibility to bradycardia in response to hypoxemia is also higher due to high vagal tone. Pores of Kohn and channels of Lambert (bronchoalveolar and interalveolar collaterals) are inadequately developed making regional atelectasis more frequent. Closing volumes are lower and airway collapse due to inadequate strength of the cartilage in the airways is common making a child particularly susceptible to laryngomalacia, and tracheobronchomalacia as well as lower airways closure.