AJCC
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

American Journal of Critical Care. 2003;12: 454-460
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Respond to This Article
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Right arrow Take the CE Test
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Grap, M. J.
Right arrow Articles by Sessler, C. N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Grap, M. J.
Right arrow Articles by Sessler, C. N.

Collaborative Practice: Development, Implementation, and Evaluation of a Weaning Protocol for Patients Receiving Mechanical Ventilation

By Mary Jo Grap, RN, PhD, ACNP, Dale Strickland, RN, MS, Laura Tormey, RN, BS, Kim Keane, RN, BSN, Shannon Lubin, RN, BSN, Joanne Emerson, RN, BSN, Suzanne Winfield, RN, MS, Paul Dalby, RRT, Regina Townes, CRT and Curtis N. Sessler, MD. From Virginia Commonwealth University, Richmond, Va.


   Abstract
Top
 Abstract
Identification of Need and...
 Protocol Implementation
 Measuring Protocol Outcomes
 Sustaining Success
 Summary
 References
 
• Background Use of protocols to reduce weaning time for patients receiving mechanical ventilation helps reduce cost and length of stay. However, implementation of this type of protocol is not easy and requires a consistent collaborative effort.

• Objective To provide a systematic approach to the weaning process by developing, implementing, and evaluating a protocol for weaning patients from mechanical ventilation in a medical respiratory intensive care unit.

• Methods The weaning protocol used was a modification of a protocol developed by Ely et al. Modifications included a more aggressive approach in proceeding to the spontaneous breathing trial, inclusion of the Richmond Agitation-Sedation Scale, and documentation of the production of secretions.

• Results Implementation of the protocol significantly reduced the duration of mechanical ventilation as measured by 8-hour shifts and ventilator days. Although length of stay in the intensive care unit was not significantly reduced (P = .29), a continuing downward trend occurred, from a mean of 8.6 days before the protocol was implemented to 7.9 days during the last 6 months of data collection (P = .07).

• Conclusions The need to provide efficient care requires the collaboration of all disciplines involved in providing patients’ care. The weaning protocol introduced in this study demonstrates the benefits of using a collaborative team to identify best practices and implement them in a practice setting.

Use of mechanical ventilation is often lifesaving, but it has high associated healthcare costs and requires many hours of skilled nursing care. Costs for a patient in an intensive care unit (ICU) are approximately 4 times greater than costs for a patient who is not in an ICU,1 and much of the added costs are related to mechanical ventilation. Healthcare professionals today continually struggle to decrease the length of stay (LOS) of ICU patients.

More than one third of critically ill patients require mechanical ventilation, and 41% of the time required for mechanical ventilation is spent weaning patients from the treatment.2 Care of patients receiving mechanical ventilation is "high risk" and "high cost." High mortality rates and iatrogenic complications commonly associated with mechanical ventilation focus attention on finding ways to reduce the duration of mechanical ventilation by reducing the time required for weaning.

Conceptually, weaning from mechanical ventilation includes both the assessment of a patient’s readiness to breathe independently and the systematic reduction of ventilatory support. A variety of weaning strategies and approaches have been used to assess weaning readiness and to reduce ventilatory support with various degrees of success. In the past, determining a patient’s readiness to be weaned and reducing ventilatory support were based on the judgments of individual physicians, who considered objective indicators of gas exchange, respiratory mechanics, and the patient’s ability to protect the airway. Use and evaluation of these indicators often resulted in wide variations in weaning practices among providers. This variability in weaning practice may be magnified in academic medical centers because of the frequent turnover among attending physicians and house staff.


Patients receiving mechanical ventilation have shorter hospital stays and lower costs when a weaning protocol is used.

 

More recently, the use of multidisciplinary weaning protocols has markedly reduced the duration of mechanical ventilation.3–7 Cohen et al6 found that use of a multidisciplinary team that included physicians, respiratory therapists, and nurses reduced duration and costs of mechanical ventilation when compared with weaning done by critical care fellows. Costs of care were lower as a result of shorter ventilation time and a reduction in arterial blood gas levels and use of arterial catheters. Cohen et al found that the multidisciplinary team relied more on a systematic approach to weaning than did the house staff, who may rely more on expensive laboratory diagnostics. Ely et al5 found that daily screening of a patient’s respiratory function and subsequent trials of spontaneous breathing and notification of the patient’s physician when the trials were successful reduced the duration of mechanical ventilation and the cost of intensive care. Likewise, in a randomized, controlled trial of protocol-versus physician-directed weaning, Kollef et al3 found that protocol-guided weaning of patients from mechanical ventilation, as performed by nurses and respiratory therapists, was safe and led to extubation more rapidly than did physician-directed weaning. A systematic approach to weaning may prevent lapses in care that occur in ICUs, where emergencies have precedence over rehabilitative care.

The key to successful weaning may be that a protocol is used, rather than specifically how the protocol is constructed or what method of weaning is used.8 Kollef et al3 noted shorter weaning times in a study comparing use of protocols to no protocol. Burns et al9 compared the effects of an outcome approach that used critical pathways with effects of an approach in which outcomes were not managed. Outcome-managed patients had 1.3 fewer days of mechanical ventilation and an LOS 2.1 days shorter than did patients whose outcomes were not managed, with a cost savings of $3341 per case. The positive trends noted during the study interval persisted for 2 years, and the variables of cost, LOS, and ventilator duration continue to be favorably affected.10 Use of an outcomes-managed approach includes an outcome manager, a respected and valued member of the team who is central to the ongoing success of the approach. The protocol is an integral part of the process but is continually evaluated and changed as needed.9

These studies just described indicate that systematic methods of weaning patients from mechanical ventilation may result in beneficial outcomes. The use of protocols and interdisciplinary teams provides consistency in the weaning process across all types and levels of provider experience, allows for easy communication of weaning status, and ultimately assists patients in progressing to extubation in a timely fashion.10 Recently, in a consensus project11 to create a set of evidence-based clinical practice guidelines for weaning patients from mechanical ventilation, several important issues were identified. First, the evidence suggests that independent clinical judgment of or experience with patients’ readiness to be weaned is a relatively poor predictor of weaning success. Second, clinical assessments (respiratory pattern, cardiovascular response, comfort/anxiety, oxygenation) are better predictors of success than are more complex weaning parameters. Third, daily spontaneous breathing trials are superior to gradual reductions in ventilatory support (ie, gradual reduction in synchronized mandatory ventilation or pressure-support ventilation). Finally, it is clear that nurses and respiratory therapists can effectively achieve weaning goals by using protocols. Importantly, implementation of weaning protocols requires a consistent team effort that may be difficult to sustain in the complex critical care environment.


   Identification of Need and Protocol Development
Top
 Abstract
 Identification of Need and...
Protocol Implementation
 Measuring Protocol Outcomes
 Sustaining Success
 Summary
 References
 
The nursing practice committee in our 12-bed medical respiratory ICU (MRICU) at the Virginia Commonwealth University Health System, Richmond, Va, a large, urban, academic medical center, and the MRICU’s medical director identified weaning from mechanical ventilation as an opportunity to improve consistency in practice and patients’ outcomes. The MRICU nursing practice committee (a group of experienced nurse clinicians) and respiratory therapists reviewed the current procedure for weaning. In collaboration with the MRICU acute care nurse practitioner (ACNP), the MRICU respiratory therapists, and the MRICU medical director, team meetings were held to coordinate the activities and establish goals. The ACNP served as the liaison between the parties.

Protocol Development
The protocol was developed through a collaborative process among the MRICU ACNP, the medical director, the MRICU nursing practice committee, and the respiratory therapy staff after a thorough review of the literature. Once developed and critiqued by all participants, the protocol was presented to all MRICU attending physicians for review and feedback.

The MRICU Weaning Protocol
The protocol comprises weaning algorithms that were practical and evidence based as described by Esteban and Alia12 and Ely et al13,14 (Table 1Go). The final form of the protocol is a modification of the protocol originally developed by Ely et al.13,14 Several modifications deserve mention. First, the threshold for the ratio of PaO2 to fraction of inspired oxygen was decreased from 200 to 150 for proceeding to the next step. Our experience suggested that patients who had a PaO2 of 76 to 100 mm Hg at a fraction of inspired oxygen of 0.5 did not often require reintubation as a result of hypoxemia. We also included the rapid shallow breathing index (respiratory rate/tidal volume) as a separate, second screen, once the patient had passed all items on the first screen. We also liberalized the threshold for the rapid shallow breathing index from 105 to 125. Although not specifically tested in clinical trials, this somewhat more aggressive approach, we thought, would allow more patients to proceed to the spontaneous breathing trial, thus decreasing weaning time without increasing the risk of failed extubation.


View this table:
[in this window]
[in a new window]
  		Table 1 Weaning protocol for the medical respiratory intensive care unit

 
The level of sedation is a component of many weaning tools, including ours. During protocol development, the MRICU staff was testing a new sedation scale, the Richmond Agitation-Sedation Scale (RASS; Table 2Go). The RASS15 developed and validated by members of this team is a 10-point scale, from +4 (combative) through 0 (calm, alert) to -5 (unarousable). Patients are assessed at the bedside in 3 simple steps by using discrete criteria, for 30 to 60 seconds. In 202 adult ICU patients, interrater reliability (r = 0.96) was excellent among 5 physician, nurse, and pharmacist investigators. Interrater reliability (r = 0.92-0.98) was high for patients from medical, surgical, cardiac surgery, coronary, and neuroscience ICUs, patients receiving and patients not receiving mechanical ventilation, and patients with and without sedative medications.15 In validity testing, the RASS correlated highly (r = 0.97) with a visual analogue scale anchored by "combative" and "unresponsive," the Ramsay sedation scale16 (r = -0.85), and the Sedation Agitation Scale17 (r = 0.86).15 After implementation of the RASS in the MRICU, interrater reliability was 0.96 between a nurse investigator and 27 RASS-trained bedside nurses in 101 encounters with patients.15 In addition, the scale is used as part of a comprehensive confusion assessment method developed and validated in another institution.18,19 Because a critical part of the weaning protocol is an assessment of sedation, the RASS was included as part of the weaning protocol. During protocol pilot testing, nursing staff voiced concerns that the volume of patients’ respiratory secretions was not included as part of the protocol. Because excessive production of secretions may hamper a patient’s ability to sustain spontaneous breathing, this item was documented but was not a formal step in the protocol.


View this table:
[in this window]
[in a new window]
  		Table 2 Richmond Agitation-Sedation Scale

 
The protocol depends primarily on the actions of staff nurses and respiratory therapists, and these team members were key participants in the implementation and continuation of the protocol. Members of these groups both assessed whether patients were ready for a weaning trial by completing screens 1 and 2 (Table 1Go) and monitoring patients’ responses to the trial.


   Protocol Implementation
Top
 Abstract
 Identification of Need and...
 Protocol Implementation
Measuring Protocol Outcomes
 Sustaining Success
 Summary
 References
 
Extensive education of the unit’s critical care staff, including the nurses, respiratory therapists, and physicians, took place before the protocol was implemented. Presentations were given by the ACNP to groups of staff members on several occasions, and literature and posters were posted in the critical care area. The MRICU’s nursing practice committee met frequently to discuss concerns and areas for improvement. Each patient’s bedside nurse coordinated all activities of the protocol. Information related to the progress of protocol implementation and identification of areas for success and areas needing improvement were communicated frequently by charge nurses, in medical team rounds, through posters displayed in the unit, and discussions at staff meetings.


Weaning assessments were done every day.

 

Once the protocol was implemented, all patients receiving mechanical ventilation were assessed daily by using the screens outlined in the protocol (Table 1Go). Data for the screens were collected daily at 8 AM by a nurse or a respiratory therapist. After a few months, the collection time was changed to 6 AM because of conflicts with timeliness of completion of early morning tasks. During the first few months of use of the protocol, on the basis of staff comments, changes were made to the documentation sheet to enhance the clarity of the process.

Each patient’s progress on the protocol was presented in multidisciplinary rounds that occurred every morning. The results of screens 1 and 2 were reported. Initially, decisions to initiate the spontaneous breathing trial were made during these rounds; however, as the nursing and respiratory therapy staff became more familiar with the protocol, and ICU physicians were comfortable with the process, the spontaneous breathing trial was often well under way at the time of rounds, further reducing the duration of mechanical ventilation. A senior physician (attending or fellow) made the decision to extubate on the basis of the results of the spontaneous breathing trial.


   Measuring Protocol Outcomes
Top
 Abstract
 Identification of Need and...
 Protocol Implementation
 Measuring Protocol Outcomes
Sustaining Success
 Summary
 References
 
The objective of the weaning protocol was to provide a systematic approach to the weaning process to reduce the durations of mechanical ventilation and stay in the ICU. Initially, we thought that we could collect data about the day-to-day process of protocol implementation, documenting every aspect of the protocol. However, after several months of data collection, and without any additional resources for this project, we realized that even though the protocol was in place and patients were being weaned from mechanical ventilation through use of the process, documentation of each step was difficult. Respiratory therapists and bedside nurses were primarily responsible for the documentation. Although compliance was high for the respiratory therapists, the nurses’ compliance level was not adequate. Screens 1 and 2 were often complete, but the outcome of the spontaneous breathing trial and the extubation date often were not recorded on the weaning assessment form. Therefore, to evaluate the outcomes in a more systematic fashion, data were obtained from the medical center’s decision support department. This data provided information about all patients whose hospital bill included a charge for mechanical ventilation and were cared for in the MRICU. Information about the duration of mechanical ventilation (by 8-hour shifts), LOS in the MRICU, and ventilator costs were obtained. For comparison, similar data were obtained for the 14 months before the weaning protocol was implemented.


Use of the weaning protocol reduced duration of mechanical ventilation.

 

Although this analysis and evaluation procedure did not include controls for extraneous events that may have affected the weaning process in the MRICU, the length of data collection and the sample size should reduce these effects. In addition, no obvious major changes occurred in the weaning processes (new procedures, equipment, or change in attending physicians). However, the protocol progress documentation and data collection times did change during this period. Because this protocol was developed and implemented primarily as a clinical tool, rather than as a rigorous research tool, these intervening variables may have affected the outcomes presented here. In clinical projects, it is often not possible to control for all variables that may affect outcomes. However, protocols intended for clinical use must be practical and efficient as well as responsive to the needs of patients and staff.

The primary purpose for protocol use was realized. Implementation of the protocol significantly reduced the duration of mechanical ventilation as measured by 8-hour shifts and ventilator days (Table 3Go). Although LOS in the MRICU was not significantly reduced (P = .29), a continuing downward trend occurred, from a mean of 8.6 days before the protocol was implemented to 7.9 days during the last 6 months of data collection (P = .07).


View this table:
[in this window]
[in a new window]
  		Table 3 Comparison of weaning outcomes before and after protocol implementation*

 

   Sustaining Success
Top
 Abstract
 Identification of Need and...
 Protocol Implementation
 Measuring Protocol Outcomes
 Sustaining Success
Summary
 References
 
The significant reduction in duration of mechanical ventilation was a beneficial outcome and is similar to the data found in other trials3,5,7,20 in which a weaning protocol was used. A major challenge in implementing any protocol is the ability to sustain the protocol process. The MRICU has a monthly turnover in house staff, and new interns and residents begin working each year. Therefore, it was especially important to continue education about the weaning process to ensure consistency in use of the protocol. However, a major benefit in this unit is the limited number of attending physicians (5) who are responsible for the management of all MRICU patients. Implementation of new processes can be more easily communicated and maintained with a small group of providers. The continued success of the protocol over time is evidenced in Table 3Go by the continued decreases in duration of mechanical ventilation and LOS in the MRICU.


Use of a nurse-directed weaning protocol may increase nurses’ knowledge and sense of autonomy.

 

Discussions with the MRICU nursing staff clearly indicated that the use of a weaning protocol has created additional benefits. Nurses feel a greater sense of autonomy and responsibility for their patients’ care. The protocol has increased their direct involvement in decisions related to patients’ care and has provided an additional avenue for communication with the health-care team. Further, through education and use of the protocol, the nurses have gained comprehensive and valuable knowledge of respiratory assessment and mechanics that allows them to actively contribute to good outcomes for patients.


Multidisciplinary collaboration is critical to success.

 


   Summary
Top
 Abstract
 Identification of Need and...
 Protocol Implementation
 Measuring Protocol Outcomes
 Sustaining Success
 Summary
References
 
The need to provide efficient care requires the collaboration of all disciplines involved in providing patients’ care. The weaning protocol we introduced in the MRICU is an excellent example of the benefits of using a collaborative team to identify a best practice and then implement it in a practice setting. Successful implementation of a protocol such as described here requires the full commitment of all members of the healthcare team and can have a significant effect on patients’ outcomes.

To purchase reprints, contact The InnoVision Group, 101 Columbia, Aliso Viejo, CA 92656. Phone, (800) 809-2273 or (949) 362-2050 (ext 532); fax, (949) 362-2049; e-mail, reprints{at}aacn.org.


   REFERENCES
Top
 Abstract
 Identification of Need and...
 Protocol Implementation
 Measuring Protocol Outcomes
 Sustaining Success
 Summary
 References
 

  1. Kite-Powell DM, Sabau D, Ideno KT, Hartgraves D, Dahlberg CG. Optimizing outcomes in ventilator-dependent patients: challenging critical care practice. Crit Care Nurs Q. November 1996;19:77–90.[Medline]
  2. Esteban A, Alia I, Ibanez J, Benito S, Tobin MJ. Modes of mechanical ventilation and weaning: a national survey of Spanish hospitals. The Spanish Lung Failure Collaborative Group. J Hosp Infect. 1994;106:1188–1193.
  3. Kollef MH, Shapiro SD, Silver P, et al. A randomized, controlled trial of protocol-directed versus physician-directed weaning from mechanical ventilation [see comments]. Crit Care Med. 1997;25:567–574.[Medline]
  4. Ibrahim EH, Kollef MH. Using protocols to improve the outcomes of mechanically ventilated patients: focus on weaning and sedation. Crit Care Clin. 2001;17:989–1001.[Medline]
  5. Ely EW, Baker AM, Dunagan DP, et al. Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med. 1996;335:1864–1869.[Abstract/Free Full Text]
  6. Cohen IL, Bari N, Strosberg MA, et al. Reduction of duration and cost of mechanical ventilation in an intensive care unit by use of a ventilatory management team. Crit Care Med. 1991;19:1278–1284.[Medline]
  7. Henneman E, Dracup K, Ganz T, Molayeme O, Cooper C. Effect of a collaborative weaning plan on patient outcome in the critical care setting. Crit Care Med. 2001;29:297–303.[Medline]
  8. Kollef MH, Horst HM, Prang L, Brock WA. Reducing the duration of mechanical ventilation: three examples of change in the intensive care unit. New Horiz. 1998;6:52–60.[Medline]
  9. Burns SM, Marshall M, Burns JE, et al. Design, testing, and results of an outcomes-managed approach to patients requiring prolonged mechanical ventilation. Am J Crit Care. 1998;7:45–57.[Abstract]
  10. Burns SM. The long-term mechanically ventilated patient: an outcomes management approach. Crit Care Nurs Clin North Am. 1998;10:87–99.[Medline]
  11. MacIntyre NR, Cook DJ, Ely EW Jr, et al. Evidence-based guidelines for weaning and discontinuing ventilatory support: a collective task force facilitated by the American College of Chest Physicians; the American Association for Respiratory Care; and the American College of Critical Care Medicine. Chest. 2001;120(6 suppl):375S–395S.[Free Full Text]
  12. Esteban A, Alia I. Clinical management of weaning from mechanical ventilation. Intensive Care Med. 1998;24:999–1008.[Medline]
  13. Ely EW, Bennett PA, Bowton DL, Murphy SM, Florance AM, Haponik EF. Large scale implementation of a respiratory therapist-driven protocol for ventilator weaning. Am J Respir Crit Care Med. 1999;159:439–446.[Abstract/Free Full Text]
  14. Ely EW, Baker AM, Evans GW, Haponik EF. The prognostic significance of passing a daily screen of weaning parameters. Intensive Care Med. 1999;25:581–587.[Medline]
  15. Sessler CN, Gosnell MS, Grap MJ, et al. The Richmond Agitation-Sedation Scale: validity and reliability in adult intensive care unit patients. Am J Respir Crit Care Med. 2002;166:1338–1344.[Abstract/Free Full Text]
  16. Ramsay MA, Savage TM, Simpson BR, Goodwin R. Controlled sedation with alphaxalone-alphadolone. Br Med J. 1974;2:656–659.[Medline]
  17. Riker RR, Picard JT, Fraser GL. Prospective evaluation of the Sedation-Agitation Scale for adult critically ill patients. Crit Care Med. 1999; 27:1325–1329.[Medline]
  18. Ely EW, Margolin R, Francis J, et al. Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Crit Care Med. 2001;29:1370–1379.[Medline]
  19. Ely EW, Inouye SK, Bernard GR, et al. Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU). JAMA. 2001;286:2703–2710.[Abstract/Free Full Text]
  20. Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. Spanish Lung Failure Collaborative Group [see comments]. N Engl J Med. 1995;332:345–350.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 Crit Care NurseHome page
T. Unoki, A. Serita, and M. J. Grap
Automatic Tube Compensation During Weaning From Mechanical Ventilation: Evidence and Clinical Implications
Crit. Care Nurse, August 1, 2008; 28(4): 34 - 42.
[Full Text] [PDF]

Home page
 Eur Respir JHome page
J-M. Boles, J. Bion, A. Connors, M. Herridge, B. Marsh, C. Melot, R. Pearl, H. Silverman, M. Stanchina, A. Vieillard-Baron, et al.
Weaning from mechanical ventilation
Eur. Respir. J., May 1, 2007; 29(5): 1033 - 1056.
[Abstract] [Full Text] [PDF]

Home page
 Am J Crit CareHome page
K. McCauley and R. S. Irwin
Changing the Work Environment in Intensive Care Units to Achieve Patient-Focused Care: The Time Has Come
Am. J. Crit. Care., November 1, 2006; 15(6): 541 - 548.
[Abstract] [Full Text] [PDF]

Home page
 ChestHome page
K. McCauley and R. S. Irwin
Changing the Work Environment in ICUs to Achieve Patient-Focused Care: The Time Has Come.
Chest, November 1, 2006; 130(5): 1571 - 1578.
[Abstract] [Full Text] [PDF]

Home page
 Am J Crit CareHome page
S. E. McLean, L. A. Jensen, D. G. Schroeder, N. R. T. Gibney, and N. M. Skjodt
Improving Adherence to a Mechanical Ventilation Weaning Protocol for Critically Ill Adults: Outcomes After an Implementation Program
Am. J. Crit. Care., May 1, 2006; 15(3): 299 - 309.
[Abstract] [Full Text] [PDF]

Home page
 ThoraxHome page
A K Simonds
Streamlining weaning: protocols and weaning units
Thorax, March 1, 2005; 60(3): 175 - 182.
[Full Text] [PDF]

Home page
 Am. J. Respir. Crit. Care Med.Home page
J. A. Krishnan, D. Moore, C. Robeson, C. S. Rand, and H. E. Fessler
A Prospective, Controlled Trial of a Protocol-based Strategy to Discontinue Mechanical Ventilation
Am. J. Respir. Crit. Care Med., March 15, 2004; 169(6): 673 - 678.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Respond to This Article
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Right arrow Take the CE Test
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Grap, M. J.
Right arrow Articles by Sessler, C. N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Grap, M. J.
Right arrow Articles by Sessler, C. N.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS