Page 604 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

424 PART 4: Pulmonary Disorders

KEY REFERENCES • The patient with severe airflow obstruction often develops hypo-
• Coussa, ML, Guérin C, Eissa NT, et al. Partitioning of work of perfusion after institution of positive-pressure ventilation as a result
breathing in mechanically ventilated COPD patients. J Appl of autoPEEP; this responds to temporary cessation of ventilation
Physiol. 1993;75:1711-1719. and vigorous volume resuscitation, while measures are employed to
• Grasso S, Stripoli T, de Michele M, et al. ARDSnet ventilatory pro- reduce airflow obstruction and reduce the total minute ventilation.
tocol and alveolar hyperinflation: role of positive end-expiratory • The patient with acute hypoxemic respiratory failure (AHRF)
pressure. Am J Respir Crit Care Med. 2007;176:761-767. resulting from pulmonary edema benefits from lung-protective
• Marini JJ, Capps JS, Culver BH. The inspiratory work of breathing ventilation (6 mL/kg ideal body weight and rate approximately 30
during assisted mechanical ventilation. Chest. 1985;87:612-618. breaths/min). The initial Fi O 2 of 1.0 can be lowered to nontoxic
• Nassar BS, Collett ND, Schmidt GA. The flow-time waveform levels by raising positive end-expiratory pressure (PEEP), guided
predicts respiratory system resistance and compliance. J Crit Care. by pulse oximetry or measures of recruitment.
2012;27:418.e7-418.e14.
• Pepe PE, Marini JJ. Occult positive end-expiratory pressure in
mechanically ventilated patients with airflow obstruction. Am Rev
Respir Dis. 1982;126:166-170.
• Pohlman MC, McCallister KE, Schweickert WD, et al. Excessive Regardless of the underlying process leading to mechanical venti-
lation, several principles guide ventilator settings and associated
tidal volume from breath stacking during lung-protective ventila- management. This chapter emphasizes preventing complications by
tion for acute lung injury. Crit Care Med. 2008;36:3019-3023. using the “ventilator bundle”; avoiding lung injury (through overdis-
• Ranieri VM, Zhang H, Mascia L, et al. Pressure-time curve pre- tention or autoPEEP); limiting ventilator-induced diaphragm dysfunc-
dicts minimally injurious ventilatory strategy in an isolated rat tion (VIDD); understanding cardiopulmonary interactions; choosing
lung model. Anesthesiology. 2000;93:1320-1328. modes and settings in relation to the underlying cause of respiratory
• Tuxen DV. Detrimental effects of positive end-expiratory pressure failure; ensuring synchrony between patient and ventilator; and
during controlled mechanical ventilation of patients with severe responding to crises.
airflow obstruction. Am Rev Respir Dis. 1989;140:5-9. Other chapters of this book are complementary to the information
presented here. The pathophysiology of respiratory failure is broadly
reviewed in Chap. 43; monitoring respiratory system waveforms of pres-
sure and flow is delineated in Chap. 48; noninvasive ventilation is cov-
REFERENCES ered in Chap. 44; ventilator-induced lung injury is discussed in Chap. 51;
and finally, several chapters (eg, Chap. 52, Acute Respiratory Distress
Complete references available online at www.mhprofessional.com/hall Syndrome; Chap. 54, Acute on Chronic Respiratory Failure; Chap. 55,
Status Asthmaticus; Chap. 58, Restrictive Disease of the Respiratory System)
discuss ventilatory support for specific problems.

CHAPTER Management of the PREVENTION: THE “VENTILATOR BUNDLE”
49 Ventilated Patient Mechanically ventilated patients are at risk for numerous complica-
tions related to the presence of the endotracheal tube, most notably
Gregory A. Schmidt ventilator-associated pneumonia (VAP), as well as adverse consequences
Jesse B. Hall of sedatives, paralytics, and immobilization. In response, the Institute for
Healthcare Improvement promulgated the concept of “bundles,” a struc-
tured set of processes that, when performed collectively and reliably,
KEY POINTS improve outcomes (head of bed elevation; daily sedative interruption
and readiness assessment; and steps to prevent venous thromboembo-
• Effective preventive measures in ventilated patients include raising the lism and gastrointestinal hemorrhage). Ideally, these are evidence-based
head of the bed, employing measures to prevent venous thromboem- interventions but, in actual fact, include tactics with an uncertain impact
bolism, avoiding unnecessary changes of the ventilator circuit, reduc- on VAP. Effective preventive measures are more fully discussed in
ing the amount of sedation, and providing oral care with chlorhexidine. Chaps. 3, 4, 5, and 22, but are briefly summarized here.
• Even patients with normal lungs may benefit from limited tidal Noninvasive ventilation should be used in appropriate candidates,
volumes to reduce the risk of ventilator-induced lung injury caus- since this reduces the risk of VAP in COPD patients and perhaps those
1
ing progression to acute respiratory distress syndrome. in an immunocompromised state. For intubated patients, the head of
2
3
• Critical illness and mechanical ventilation combine to impair the bed should be elevated to 30° to 45°. This intervention may or may
4
strength of respiratory muscles and produce atrophy. This ten- not be effective in reducing VAP, but has the virtues of being simple,
dency can be reduced by setting the ventilator in a way as to pre- inexpensive, and logical, since much VAP is thought to arise from
serve inspiratory muscle contraction. aspiration of gastric contents. Ventilator tubing should be changed
only when the tubing is visibly soiled or malfunctioning, rather than
• Whenever the adequacy of oxygen exchange is in question, the on a time-based schedule. Sedative use should be limited and patients
5
) should be 1.0; this will be
initial fraction of inspired oxygen (Fi O 2 should be allowed to wake up daily, as discussed below and in Chap. 22.
diagnostic as well as therapeutic, since failure to achieve full arterial Ideally, the “wake-up” should be coordinated with a spontaneous
hemoglobin saturation identifies a significant right-to-left shunt. breathing trial (SBT) to judge readiness for extubation. Prophylaxis
6
• The choice of ventilator mode is relatively unimportant: more against venous thromboembolism is indicated in most patients. Oral
relevant is to use the ventilator with full understanding of the care with chlorhexidine is probably effective. There is no consensus
7
principles of lung protection, ventilator-induced diaphragm dys- regarding the effectiveness of selective decontamination of the diges-
function, autoPEEP, and patient-ventilator synchrony. tive tract, subglottic suctioning, or avoidance of antiacid therapies for
prevention of VAP.

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