March 2002 / Volume 47 / Number 2 / Page 247
Invasive Mechanical Ventilation in Adults: Implementation, Management, Weaning, & Follow-Up
Mechanical ventilation is ubiquitous to intensive care units around the world. In fact, it could be argued that intensive care units are simply the structures in which mechanical ventilation is practiced. The past decade has wrought a full-scale reevaluation of mechanical ventilation, from indications and management goals to ventilation parameter selection and discontinuation. Clearly these changes represent our improved understanding of the pathophysiology of respiratory failure and the application of knowledge gained from recent clinical trials. In an effort to keep pace with these changes, the American Respiratory Care Foundation convened this conference on invasive mechanical ventilation and RESPIRATORY CARE journal dedicates this and the following issue to the proceedings.
From 1980 to 1990 perhaps the greatest changes in mechanical ventilation were the ventilators. Microprocessor control allowed a wide array of breath types and breath delivery techniques. Ventilators became more sophisticated and more flexible, but also more complex and more costly. During that time the ventilator technique that produced the best blood gas values or improved some physiologic end point was clearly judged as “better.”1-3 In the last decade that idea has been placed aside and patient outcomes have become paramount. Just a simple list of the changes in mechanical ventilation spurred by research in the past 10 years is daunting.
- Noninvasive ventilation has become the first-line treatment for acute exacerbations of chronic obstructive pulmonary disease.4,5
- Selection of tidal volume (VT) during acute lung injury and acute respiratory distress syndrome (ARDS) is now based on patient height and calculated ideal body weight, and the new standard for VT is 6 mL/kg (range 4–8 mL/kg).6
- Positive end-expiratory pressure (PEEP) is no longer just for oxygenation. Mechanical properties of the respiratory system and preventing ventilator-induced lung injury are the new PEEP objectives.7,8
- Normal blood gases are for normal subjects. The goal of mechanical ventilation is no longer normal physiologic values. As with PEEP and VT, preventing lung injury is now the objective; PaCO2, PaO2, and pH are much less important. Nowhere is that more evident than in the ARDS Network trail, in which larger VT was associated with much better oxygenation on days 1–3, but with much worse outcome.6,9
- Weaning from mechanical ventilation, it turns out, may be something clinicians desire but that patients don’t need. New and expanding evidence suggests that when patients are ready to come off the ventilator, they will. Any amount of dial-twisting in the interim is an exercise in futility. How do we know when the patient is ready? Daily spontaneous breathing trials appears to be the answer.10-12
Those facts alone made this conference a necessity in an attempt to bring these changes to the forefront and to the attention of respiratory therapists everywhere.
The topics were chosen based on new research findings, and speakers were chosen to provide a broad and balanced view of the literature. David Pierson revisits the criteria for mechanical ventilation. As best we can tell, these have not changed in any textbook since the first edition of Egan.13 This topic now includes when to ventilate with a mask, when to ventilate with an artificial airway, and when not to
Turning to a more controversial topic, Ralf Kuhlen discusses the role of spontaneous breathing during ventilatory support and recent evidence supporting the use of spontaneous breathing.
Three conference papers evaluate topics to satisfy those looking for the cutting edge therapy. These include an evaluation of recruitment maneuvers (Dean Hess), a rapid-fire review of a host of ventilatory adjuncts (Robert Kacmarek), and an update on closed-loop ventilator modes (Richard Branson).
The remaining papers turn toward patient outcomes and weaning. William Hurford reviews the reasons for, monitoring of, and impact of pharmacologic sedation and paralysis on tolerance of mechanical ventilation and weaning. Weaning and extubation are expertly and succinctly reviewed by Scott Epstein. These topics could easily be the subject of an entire Journal conference. Dr Epstein summarizes the salient points and provides recommendations for appropriate weaning protocols. The relationship of tracheostomy to weaning is demystified by Charles Durbin, and myths regarding dead space and laminar flow are put to rest. The final paper attempts to put the conference into a human perspective. Randall Curtis evaluates the ultimate success of the therapy and techniques discussed in the rest of the conference by reviewing outcomes and patient quality of life after mechanical ventilation.
The emphasis of this conference is on adult patients and the use of mechanical ventilation via artificial airway. We apologize to our pediatric and neonatal colleagues in advance. However, we believe that these 2 issues of RESPIRATORY CARE represent the current state of the art on these topics and we hope that the information will be helpful to readers searching for answers. We are grateful to RESPIRATORY CARE journal and the American Respiratory Care Foundation for sponsoring this conference and look forward to the next decade of advances in mechanical ventilation.
Richard D Branson RRT FAARC
Charles G Durbin Jr MD FAARC
- Gurevitch MJ, Van Dyke J, Young ES, Jackson K. Improved oxygenation and lower peak airway pressures in severe adult respiratory distress syndrome: treatment with inverse ratio ventilation. Chest 1986;89(2):211–213.
- Cole AGH, Weller SF, Sykes MK. Inverse ratio ventilation compared with PEEP in adult respiratory failure. Intensive Care Med 1984;10(5):227–232.
- Stock MC, Downs JB. Airway pressure release ventilation: a new approach to ventilatory support during acute lung injury. Respir Care 1987;32(7):517–524.
- Brochard L, Mancebo J, Wysocki M, Lofaso F, Conti G, Rauss A, et al. Noninvasive ventilation for acute exacerbation of chronic obstructive pulmonary disease. N Engl J Med 1995;333(13):817–822.
- Meduri GU, Abou-Shala N, Fox RC, Jones CB, Leeper KV, Wunderink RG. Noninvasive face mask ventilation in patients with acute hypercapnia: respiratory failure. Chest 1991;100(2):445–454.
- The Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med 2000;342(18):1301–1308.
- Amato MB, Barbas CS, Medeiros DM, Magaldi RB, Schettino GP, Lorenzi-Filho G, et al. Effect of a protective ventilation strategy on mortality in acute respiratory distress syndrome. N Engl J Med 1998;338(6):347–354.
- Gattinoni L, Pelosi P, Crotti S, Valenza F. Effects of positive end-expiratory pressure on regional distribution of tidal volume and recruitment in adult respiratory distress syndrome. Am J Respir Crit Care Med 1995;151(6):1807–1814.
- Hickling KG, Walsh J, Henderson S, Jackson R. Low mortality rate in adult respiratory distress syndrome using low volume, pressure limited ventilation with permissive hypercapnia: a prospective study. Crit Care Med 1994;22(10):1568–1578.
- Esteban A, Frutos F, Tobin MJ, Alia I, Solsona JF, Valverdu I, et al. A comparison of four methods of weaning patients from mechanical ventilation. Spanish Lung Failure Collaborative Group. N Engl J Med 1995;332(6):345–350.
- Brochard L, Rauss A, Benito S, Conti G, Mancebo J, Rekik N, et al. Comparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation. Am J Respir Crit Care Med 1994;150(4):896–903.
- Ely EW. The utility of weaning protocols to expedite liberation from mechanical ventilation. Respir Care Clin N Am 2000;6(2):303–319.
- Egan DF. Fundamentals of inhalation therapy, 1st ed. St Louis: Mosby, 1969:432–437.