decisions made by critical care nurses during

Critical Care Management

D

MADE BY CRITICAL CARE NURSES DURING MECHANICAL VENTILATION AND WEANING IN AN AUSTRALIAN INTENSIVE CARE UNIT ECISIONS

By Louise Rose, MN, Adult Ed Cert, BN, ICU Cert, Sioban Nelson, RN, PhD, Linda Johnston, RN, PhD, and Jeffrey J. Presneill, MBBS, PhD

C E 2.0 Hours Notice to CE enrollees: A closed-book, multiple-choice examination following this article tests your understanding of the following objectives: 1. Describe the role of critical care nurses in the management of mechanical ventilation. 2. Discuss critical care nurses’ decision-making role in weaning mechanically ventilated patients. 3. Identify advantages found in this study of critical care nurses managing mechanically ventilated patients. To read this article and take the CE test online, visit www.ajcconline.org and click “CE Articles in This Issue.” No CE test fee for AACN members.

EBR

Evidence-Based Review on pp 445-446.

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Background Responsibilities of critical care nurses for management of mechanical ventilation may differ among countries. Organizational interventions, including weaning protocols, may have a variable impact in settings that differ in nursing autonomy and interdisciplinary collaboration. Objective To characterize the role of Australian critical care nurses in the management of mechanical ventilation. Methods A 3-month, prospective cohort study was performed. All clinical decisions related to mechanical ventilation in a 24bed, combined medical-surgical adult intensive care unit at the Royal Melbourne Hospital, a university-affiliated teaching hospital in Melbourne, Victoria, Australia, were determined. Results Of 474 patients admitted during the 81-day study period, 319 (67%) received mechanical ventilation. Death occurred in 12.5% (40/319) of patients. Median durations of mechanical ventilation and intensive care stay were 0.9 and 1.9 days, respectively. A total of 3986 ventilation and weaning decisions (defined as any adjustment to ventilator settings, including mode change; rate or pressure support adjustment; and titration of tidal volume, positive end-expiratory pressure, or fraction of inspired oxygen) were made. Of these, 2538 decisions (64%) were made by nurses alone, 693 (17%) by medical staff, and 755 (19%) by nurses and staff in collaboration. Decisions made exclusively by nurses were less common for patients with predominantly respiratory disease or multiple organ dysfunction than for other patients. Conclusions In this unit, critical care nurses have high levels of responsibility for, and autonomy in, the management of mechanical ventilation and weaning. Revalidation of protocols for ventilation practices in other clinical contexts may be needed. (American Journal of Critical Care. 2007;16:434-446)

AJCC AMERICAN JOURNAL OF CRITICAL CARE, September 2007, Volume 16, No. 5

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A

lthough the literature on mechanical ventilation and weaning practices is extensive, data on the role of critical care nurses in managing these practices remain limited. Some evidence1 suggests that trained and qualified nurses can beneficially influence the weaning process and reduce the duration of mechanical ventilation. However, most available data on the clinical application of mechanical ventilation and weaning by nonphysicians focus on the implementation of protocols.

In certain contexts, such protocols implemented by either nurses or respiratory therapists can reduce the duration of ventilation and weaning.2-4 Protocols are advocated as a method of standardizing clinical practice and providing nurses with increased autonomy and accountability.5,6 Conversely, protocols may be perceived as restrictive, resulting in a lack of individualized care. Furthermore, according to Lyon,7 rather than increasing nursing autonomy, protocols are a form of delegation (written rather than verbal) by medical colleagues. Arguably, protocols might not be required in an organizational context with experienced bedside clinicians and interdisciplinary collaboration, a situation common in Australian intensive care units (ICUs). The role of critical care nurses in mechanical ventilation and weaning practices in this environmental context, in the absence of formalized protocols for ventilatory support and weaning, requires further exploration. The purpose of our investigation was to describe the role of critical care nurses in making decisions about mechanical ventilation and weaning in an ICU with a high proportion of critical care qualified nursing staff (75%) and a nurse to patient ratio of 1 to 1 for patients receiving ventilatory support. In particular, our aim was to determine which clinicians made the decisions; the type, frequency, and indications

About the Authors When this article was written, Louise Rose was the critical care course coordinator at RMIT University, Bundoora, Melbourne, Australia, and a PhD candidate at the University of Melbourne and the Intensive Care Unit, the Royal Melbourne Hospital, Parkville, Victoria, Australia. She is now an assistant professor in the Lawrence S. Bloomberg Faculty of Nursing at the University of Toronto, Toronto, Canada. Sioban Nelson is the dean of nursing at the University of Toronto, Toronto, Ontario, Canada. Linda Johnston is the chair of Neonatal Nursing Research, School of Nursing, University of Melbourne, Royal Children’s Hospital, and Murdoch Children’s Research Institute, Parkville, Victoria, Australia. Jeffrey J. Presneill is a senior physician in the intensive care unit at the Royal Melbourne Hospital. Corresponding author: Louise Rose, Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, 155 College St, Room 276, Toronto, ON M5T 1P8, Canada (email: louise.rose@utoronto).

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for the decisions made; and who implemented the decisions by changing ventilator settings. Other important aspects included methods and duration of mechanical ventilation and weaning.

Methods Sample and Setting During a 3-month period in 2005, all patients admitted to the ICU of the Royal Melbourne Hospital, Victoria, Australia, who received mechanical ventilation were included in the study. This ICU is a 24-bed adult, combined medical-surgical unit in a universityaffiliated teaching hospital that also serves as the second trauma service for the state of Victoria. Approximately 100 patients per month receive mechanical ventilation in this ICU. Ethical Considerations Approval for this observational, noninterventional cohort study was obtained from the institutional review boards of both the hospital and the University of Melbourne, which together waived the need for informed consent from patients. Informed consent to participate in data collection was obtained from all nursing staff involved in the identification and description of decision making related to ventilatory support.

Although protocols enhance nurses’ autonomy and accountability, the presence of experienced bedside clinicians may render protocols less necessary.

Data Collection Definitions for demographic and ventilator information to be collected were based on previous international studies of ventilation practice.8 The data collection tool was developed in consultation with senior nursing staff experienced in management of mechanical ventilation and weaning who were not directly involved in the study. These staff members were asked to specify all clinically relevant indications for changes in ventilator support and all potential changes that could be made to ventilator settings. The final tool was further refined in a pilot study in the same ICU.


435

Before the study began, educational sessions on the aims and documentation requirements of the study were held for all staff involved in data collection. During each patient’s ICU admission, bedside nurses serially documented each decision episode. A decision episode was defined as any event that resulted in an adjustment to a patient’s ventilator settings, including a change in mode or rate; adjustment of tidal volume, pressure support, positive end-expiratory pressure, or fraction of inspired oxygen (FIO2); alteration in inspiratory pressure or time settings; and extubation. In addition, nurses documented the primary indication for the change of settings, which settings were changed, who initiated the change, and who physically changed the ventilator settings. Indications included results of arterial blood gas analysis; observed work of breathing; values for oxygen saturation (determined by pulse oximetry), minute ventilation, and inspiratory pressures; and weaning (defined as a decision that resulted in the reduction of ventilatory support for the purposes of weaning). For analytical purposes, decisions were categorized as made exclusively by nurses, made exclusively by medical staff, or collaborative. Decisions made exclusively by nurses or exclusively by medical staff were defined as decisions that did not involve interdisciplinary communication before the decision was implemented. A collaborative decision was defined as one for which both medical and nursing staff had input and shared responsibility in the decision-making process, as opposed to verbal delegation from medical to nursing staff. During the prospective audit, twice-daily rounds were made by the primary investigator (L. R.), timed to coincide with 12-hour shift changes. The purposes of the rounds were to ensure that information on all patients receiving mechanical ventilation was included in the data set, to answer queries about data collection, and to maximize compliance with the data collection tool. Patients receiving mechanical ventilation were monitored for reintubation and the use of noninvasive ventilatory support for up to 48 hours after extubation. Likewise, follow-up of patients with a tracheostomy stopped 48 hours after the discontinuation of any form of positive-pressure ventilation.

Nurses initiated 64% of ventilator setting changes; decisions to extubate were mostly collaborative.

Data Analysis Continuous data, including age and severity of illness scores, as indicated by the Acute Physiology

436

and Chronic Health Evaluation II and the total maximum Sequential Organ Failure Assessment (SOFAmax), derived from the sum of the score for the worst finding of each of the 6 subcategories during the patient’s ICU admission,9 were summarized as means and standard deviations. Interval or nonnormally distributed data were summarized as medians and interquartile ranges (IQRs). In several other investigations,8,10,11 the duration of ventilation was described by using summary statistics for data for which the censoring process of time-to-event data was ignored. In this study, the median times to successful weaning and to ICU discharge for various categories of disease were calculated by using simple time-to-event methods (survival analysis), with deaths regarded as censored observations of the weaning process. Summary statistics for data in which censoring was ignored also are provided for selected data in order to facilitate comparisons with previously published reports. Categorical data, including sex, type of admission, clinical diagnostic category, indications for mechanical ventilation and decision episodes, changes in ventilator settings, weaning method, and weaning outcome, were expressed as proportions. Relative risk ratios were calculated to determine the probability of decisions made exclusively by nurses compared with decisions made exclusively by medical staff or as the result of collaborative discussion (a binary alternative), according to the indication for ventilation, the duration of ventilation, and the patient’s severity of illness (SOFAmax score). P values less than .05 were considered significant. All analyses were performed by using Minitab, Version 14 (Minitab Inc, State College, Pennsylvania), or Stata, Version 9.0 (StataCorp LP, College Station, Texas).

Results Demographic Characteristics A total of 474 patients were admitted during the 81-day study period; of these, 319 (67%) received some form of mechanical ventilation. Most commonly, the patients who received ventilatory support were men and were admitted for surgery (Table 1). According to the categories of the Mechanical Ventilation International Study Group,8 the most frequent indications for commencement of mechanical ventilation were postoperative respiratory failure, coma, and trauma (Figure 1). When cardiac surgery patients were excluded, the single most frequent indication for mechanical ventilation was coma caused by loss of consciousness due to


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216 103

(68) (32)

Age, y Mean (SD) Median (range)

58 (18.2) 63 (18-91)

APACHE II score Mean (SD) Median (range)

14 (6.9) 13 (2-36)

SOFAmax score Mean (SD) Median (range)

8.1 (3.8) 7 (2-22)

Type of admission, No. (%) Surgical Medical Trauma

174 85 60

(54) (27) (19)

Clinical diagnostic category, No. (%) Cardiovascular Cardiac surgery Other Neurological Multitrauma Respiratory Othera

161 128 33 74 50 16 18

(50) (40) (10) (23) (16) (5) (6)

Abbreviations: APACHE, Acute Physiology and Chronic Health Evaluation; SOFAmax, total maximum Sequential Organ Failure Assessment.

a Patients with gastrointestinal, genitourinary, hematologic, or metabolic primary disorders.

160 140 120 100 80 60 40 20

S H ea eps is rt fa ilu re CO PD A RD A S sp N eu irat io ro n m us di cu se la as r e

0 Co m a Tr au Pn m a eu m on ia O th er

Duration of Ventilation and ICU Stay Patients were admitted to the ICU for a median duration of 1.9 days (IQR 1-4 days); when the censoring effect of mortality was ignored, median duration was 1.8 days. The duration of mechanical ventilation was 0.9 days (IQR 0.4-3 days; median without censoring 0.8 days). When cardiac surgery patients were excluded from analysis, the median duration of ICU stay increased to 3.3 days (IQR 1.7-6.1 days; median without censoring 2.8 days). For the 191 patients who did not have cardiac surgery, the median duration of ventilation was 2.1 days (IQR 0.8-4.9 days; median without censoring 1.8 days), of which 67% was taken up with the weaning process. In comparison, for the 128 cardiac surgery patients, median duration of ventilation was 0.4 days (IQR 0.2-0.8 days, median without censoring 0.4 days), of which approximately 50% was taken up with weaning. Durations of ICU stay, ventilation, and weaning differed substantially according to the indication for mechanical ventilation in patients who did not have cardiac surgery (Tables 2 and 3). Patients who had ventilatory support because of COPD, pneumonia, sepsis, heart failure, neuromuscular disorders, or acute respiratory distress syndrome tended to be treated with mechanical ventilation for durations greater than the overall median duration.

Value

Sex, No. (%) Men Women

Po st op

Modes of Ventilation Synchronized intermittent mandatory ventilation with volume control and pressure support was the most frequently used mode on initiation of mechanical ventilation. This mode was used for 294 of 319 patients (92%). A total of 15 patients (5%) initially had pressure-support ventilation. Only 10 patients (3%) were treated with synchronized intermittent mandatory ventilation with pressure control or biphasic intermittent positive airway pressure (referred to as bilevel for the Puritan Bennett 840 ventilator; Puritan Bennett, Pleasanton, California). Of the 306 patients who underwent weaning during the study, the majority (75%) were weaned by using a rapid transition from volume- or pressurecontrolled mandatory modes to pressure-support ventilation with no other reduction in support (Figure 2).

Characteristic

No. of patients

cerebral hemorrhage (42%), seizures (20%), intentional overdose (16%), undefined neurological cause (11%), hepatic encephalopathy (1.5%), neurological infection (1.5%), or neurological sequelae after cardiac arrest (8%). In contrast, chronic obstructive pulmonary disease (COPD) was an uncommon primary reason for ventilation; only 3 patients (1%) had this indication.

Table 1 Demographics of patients treated with mechanical ventilation (N = 319)

Indication

Figure 1 Indications for mechanical ventilation. Categories are based on definitions from Esteban et al.8 Coma includes patients with loss of consciousness due to cerebral hemorrhage, seizures, intentional overdose, undefined neurological causes, hepatic encephalopathy, neurological infection, and neurological sequelae after cardiac arrest. Abbreviations: ARDS, acute respiratory distress syndrome; COPD, chronic obstructive pulmonary disease; postop, postoperative respiratory failure.


437

No. of patients

250

Patients’ Outcomes Among the 319 patients, 269 (84%) were weaned during the first episode of mechanical ventilation. Reintubation occurred in 22 of the 319 patients (7%); 20 of these patients subsequently were weaned successfully. Overall, death occurred in 40 patients (12.5%): before weaning in 13 patients (4%), during weaning in 17 patients (5%), and more than 48 hours after successful extubation in 10 patients (3%). Noninvasive ventilatory support after extubation was implemented in 28 patients (9%). Only 3 patients (1%) self-extubated; of these, 2 required reintubation.

200

150

100

50

w ea ni ng

(d ie d)

ΔP SV +H /F

N oΔ

V ↓P S+ ΔP S

↓P S

Mechanical Ventilation and Weaning Decisions An overall total of 3986 decisions on mechanical ventilation and weaning were identified, a median of 6 decisions per patient per day of mechanical ventilation. A decision episode, as previously described, was defined as a decision that resulted in adjustment of ventilator settings. Among the 3986 decision episodes, 2790 (70%) occurred during the weaning phase of ventilation. Among the recorded decisions, 2538 (64%) were made exclusively by nurses, 693 (17%) were made exclusively by medical staff, and 755 (19%)

N o

ΔP SV +

ΔP S

V

0

Method

Figure 2 Methods of weaning. Symbols and abbreviations: Δ, change; ↓, decrease; H/F, high-flow oxygen via tracheostomy; PS, pressure support; PSV, pressure-support ventilation.

Table 2 Duration of intensive care unit stay and mechanical ventilation in patients who did not have cardiac surgery (n = 191) Duration, d

Indication Aspiration

Intensive care unit

No. of patients

Staya

Time to dischargeb

Mechanical ventilation Durationa

Time to weaningc

1

1.5

(1.5-1.5)

1.5

(1.5-1.5)

1.5

(1.5-1.5)

1.5

(1.5-1.5)

Coma

64

1.9

(0.9-3.7)

2.2

(1.1-3.8)

1.0

(0.5-2.6)

1.5

(0.6-3.0)

Postoperative respiratory failure

19

1.9

(1.0-3.8)

1.9

(1.0-3.8)

0.7

(0.3-2.6)

0.7

(0.3-3.6)

Trauma

51

3.2

(1.6-6.3)

4.1

(2.0-6.9)

2.0

(1.0-4.9)

2.8

(1.2-5.0)

7

5.1

(0.4-5.7)

5.7

(5.5-7.1)

2.3

(0.4-4.9)

3.8

(2.3-5.2)

17

5.5

(2.1-8.1)

6.0

(2.4-8.2)

4.2

(1.2-6.4)

5.0

(1.7-6.5)

3

6.7

(0.3-12)

12.0

(0.3-12)

4.9

(0.7-8.6)

8.6

(0.7-8.6)

Heart failure Pneumonia Chronic obstructive pulmonary disease Sepsis

12

6.7 (3.3-13.6)

7.6 (3.4-14.6)

4.5 (1.8-12.2)

4.5 (2.6-13.4)

Neuromuscular cause

1

11.8 (11.8-11.8)

11.8 (11.8-11.8)

10.4 (10.4-10.4)

10.4 (10.4-10.4)

Acute respiratory distress syndromed

2

15.1 (15.1-15.1)

Othere

14

3

(0.7-10.5)

Not applicable 2.7

(1.5-3.8)

12.5 (12.5-12.5) 1.8

(0.5-3.9)

Not applicable 1.7

(0.5-3.6)

a Values are median (interquartile range). b Values denote time to successful discharge from the intensive care unit in 50% of patients (25%-75%) according to analysis when data were treated as censored, with successful discharge as the outcome of interest and death as the censoring event. c Values denote time to successful weaning in 50% of patients (25%-75%) according to analysis when data were treated as censored, with successful weaning as the outcome of interest and death as the censoring event. d Data for both patients were censored because of death. e Other causes of respiratory failure include asthma, empyema, pulmonary emboli, anaphylaxis, and near-drowning.

438


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were made by collaboration. In the collaborative decisions, the patient’s bedside nurse discussed the situation with a medical colleague and nursing input was considered and used in the decisionmaking process. Overall, the most frequent indications for a change in ventilator settings were the process of weaning itself and the results of arterial blood gas analysis. In decisions made exclusively by nurses, results of arterial blood gas analysis and weaning were the primary indicators for changes in ventilator settings (Table 4). On the basis of the 3986 decision episodes, 4638 changes in ventilator settings were made; the most frequent were alterations in FIO2 and changes in mode (Table 5). Nurses initiated the majority of all types of changes, from changes in mode to titration of FIO2. A notable exception was the decision to extubate, which was predominantly collaborative. Decisions for changes in FIO2, respiratory rate, tidal volume, and pressure support were more likely to be made by a nurse than by medical staff; the decision to adjust positive end-expiratory pressure was mostly made by medical staff. A nurse initiated the onset of weaning in 249 of the 306 patients (81%) who underwent weaning. Decisions made exclusively by nurses accounted for 896 of the 1196 decisions that occurred before the commencement of weaning (75%) and 1642 of the 2790 decisions that occurred during weaning (59%). Of the 4638 physical changes to the ventilator settings, nurses made 4518 (97%) and medical staff made 120 (3%). Ventilator settings most commonly changed by medical staff were positive end-expiratory pressure and pressure support. Decisions made by nurses, both before and during weaning, often were associated with patients whose indication for ventilation was postoperative respiratory failure, aspiration, or other causes and with patients whose duration of ventilation was 7 days or less (Table 6). In patients with predominantly respiratory disease (pneumonia, acute respiratory distress syndrome, COPD) or multiple organ dysfunction (higher SOFAmax score), decisions made exclusively by nurses were less common. However, for all indications except COPD, decisions make exclusively by nurses were more common than decisions made exclusively by medical staff or in collaboration. Decision making for patients with COPD was more collaborative, and for patients with higher SOFAmax scores, more decisions were made exclusively by medical staff (Table 6).

Discussion This study was designed to describe the role of critical care nurses in mechanical ventilation and

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Table 3 Duration of weaning in patients who did not have cardiac surgery (n = 177) Duration, median (interquartile range), d No. of patients

Indication

Without censoring a

With censoring b

Postoperative respiratory failure

18

0.5

(0.1-1.5)

0.5

(0.1-1.2)

Coma

60

0.8

(0.1-2.2)

0.9

(0.1-2.4)

Trauma

48

1.2

(0.3-3.0)

1.3

(0.4-3.3)

Aspiration

1

1.5

(1.5-1.5)

1.5

(1.5-1.5)

Heart failure

5

1.7

(1.6-4.1)

1.7

(1.6-3.4)

Pneumonia

16

2.7

(1.1-6.1)

2.9

(1.0-6.4)

Sepsis

11

4.1 (1.6-12.0)

4.1 (1.6-12.0)

Chronic obstructive pulmonary disease

2

4.3

(4.3-4.3)

0.3

Acute respiratory distress syndromec

2

8.3

(8.3-8.3)

Not applicable

Neuromuscular cause

1

10.3 (10.3-10.3)

10.3 (10.3-10.3)

Other d

14

1.2

(0.3-2.6)

0.8

(0.3-8.4)

(0.3-2.4)

a Values were calculated without censoring for death or loss to follow-up, as done in previous studies.8,10,11 b Values were calculated according to time-to-event analysis, with successful weaning as the outcome and death as a censored event. c Data for both patients were censored because of death. d Other causes of respiratory failure include neoplasm, empyema, pulmonary emboli, gastrointestinal bleeding or inflammatory disease, and disturbances in cardiac rhythm.

Table 4 Indications for decision episodes (N = 3986) according to professional group No. (%) of decisions

Indication Arterial blood gas analysis

Made by Total nurses (N = 3986) (n = 2538)

Made by medical staff (n = 693)

Collaborative (n = 755)

130 (19)

104 (14)

1348 (34)

1114 (44)

Arterial oxygen saturation

454 (11)

395 (16)

40 (6)

Minute ventilationa

138 (3)

112 (4)

18 (3)

8 (1)

Work of breathingb

143 (4)

100 (4)

25 (4)

18 (2)

41 (1)

20 (1)

11 (2)

10 (1)

Peak inspiratory pressurea Weaningc

19 (3)

1395 (35)

665 (26)

270 (39)

460 (61)

Transportd

226 (6)

25 (1)

103 (15)

98 (13)

Othere

241 (6)

107 (4)

96 (14)

38 (5)

a As displayed on the ventilator. b Determined by visual assessment of increased activation of respiratory muscles. c Reduction of ventilator support made for the purposes of weaning. d Changes in ventilation required for the purposes of transporting the patient. e Other indications requiring decisions about changes in ventilator settings, including apnea, chest radiography, use of increased sedation or a paralyzing agent, worsening clinical picture, increased tidal volume, positive end-expiratory pressure recruitment maneuver, ventilator-patient dysynchrony, withdrawal of treatment, and tests for brain death.


439

Table 5 Changes in ventilator settings initiated exclusively by nurses Decisions made exclusively by nurses

Changes made in

Total No. of changes

No.

% (95% confi- Relative risk a (95% dence interval) confidence interval)

1725

1480

86 (84-87)

1

80

62

78 (67-86)

0.90 (0.80-1.02)

Rate

296

223

75 (70-80)

0.88 (0.82-0.94)

Pressure support

536

Fraction of inspired oxygen Tidal volume

367

68 (64-72)

0.80 (0.75-0.85)

60

30

50 (37-63)

0.58 (0.45-0.75)

1238

613

50 (47-52)

0.58 (0.54-0.61)

Positive endexpiratory pressure

341

159

47 (41-52)

0.54 (0.48-0.61)

Extubation

307

4

1 (0.3-3)

0.02 (0.01-0.04)

55

22

40 (27-54)

0.47 (0.34-0.64)

Inspiratory pressure Mode

Other b

a Relative risk of a decision being made exclusively by a nurse. b Other changes in ventilator settings included inspiratory time, automatic tube compensation, sensitivity, apnea interval, flow rate, and reintubation.

weaning practices in an Australian ICU with a closed ICU model. In this setting, clinical services were delivered by trained and experienced nursing staff practicing in collaboration with house and consultant staff assigned exclusively to this ICU. In addition, the unit had no formalized protocols for mechanical ventilation and weaning and no respiratory therapists. Our results indicate that within this context, critical care nurses had a high level of responsibility for, and autonomy in, the management of mechanical ventilation and weaning. Critical care nurses were responsible for the majority of the decision episodes that resulted in a change to ventilator settings, ranging in complexity from the simple titration of FIO2 to a decision to commence weaning. Furthermore, on the basis of international norms,8,10,11 this type of clinical care resulted in weaning outcomes and duration of ventilation that were generally acceptable. Traditionally, decision making associated with mechanical ventilation has been the responsibility of medical staff, with nurses involved in the process but not directly responsible for the initiation of ventilator changes.12-16 Experienced nurse clinicians are well positioned to continuously monitor a patient’s pathophysiological parameters and rapidly intervene with alterations in ventilatory support if required.

Seventy-five percent of these nurses held critical care qualification; the unit had a nurse to patient ratio of 1 to 1 for patients receiving mechanical ventilation.

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For ICU teams to function to the best of their ability, the skills and input of each team member must be recognized. Enabling nurses to practice with a degree of autonomy in managing mechanical ventilation and weaning, as occurred in the unit in our study, acknowledges the important contribution nurses can make. Most of the published data2,17-19 on the clinical management of mechanical ventilation and weaning by nonphysicians describes the implementation of weaning protocols in non-Australian ICUs. Protocols have been advocated as an effective and efficient method for providing ventilatory support and timely weaning, resulting in reductions in the duration of mechanical ventilation.20 According to Hess,21 these shorter durations may be due to the early recognition of a patient’s ability to breathe and therefore a faster reduction in ventilatory support. However, the advantage of weaning protocols in organizational settings that favor adequate numbers of skilled and experienced staff in expediting discontinuation of mechanical ventilation has been questioned.22 In studies conducted in Australia, the use of both weaning23 and sedation24 protocols resulted in a prolonged duration of mechanical ventilation rather than in the dramatic reductions found in similar studies done in North America. These findings suggest that imposing a protocol that introduces multiple steps with fixed time points may not be beneficial in existing Australian practice. The nurses in our study had marked autonomy in making decisions about mechanical ventilation and practiced in an environment in which 75% of nursing staff held a tertiary-level critical care qualification and the nurse to patient ratio was 1 to 1 for patients receiving mechanical ventilation. In many Australian ICUs, nurses administer both invasive and pharmacological treatments in the context of an overall ICU management plan without the direct input of medical staff.25 Moreover, the proportion of nurses with a postgraduate critical care qualification in Australia is higher than in other countries.26 Recommendations from both the Australian Health Workforce Advisory Committee and The Australian College of Critical Care Nurses recommend that a minimum of 50% of nursing staff employed within an individual ICU have a postgraduate qualification.25 These characteristics, including comprehensive nursing education support, independent nursing responsibilities, and excellent nurse-physician communication, have been associated with high-performance ICUs with excellent outcomes for patients.27 Another important feature in the workforce profile of Australian ICUs is the absence of respiratory


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therapists. In North America, respiratory therapists, rather than critical care nurses, play a major role in managing and making decisions about mechanical ventilation and weaning.28 Nurse to patient ratios for patients receiving ventilatory support also differ internationally. In Australia, the nurse to patient ratio for patients receiving mechanical ventilation is 1 to 1, as recommended by the minimum standards of the Australasian Joint Faculty of Intensive Care Medicine.29 In contrast, the reported nurse to patient ratio in North America is 1 to 2, and the respiratory therapist to patient ratio may be 1 to 8.30 The results of several studies31-33 suggest that greater numbers of nursing staff improve patients’ outcomes within the ICU environment. Conversely, increased length of stay and rates of reintubation, pneumonia, and sepsis are associated with reduced nurse to patient ratios.31,34 Therefore, recommendations from studies done in North America may have limited application to the Australian setting because of substantial differences in workforce profile and organizational structures. In our study, the durations of ICU stay, mechanical ventilation, and weaning compare favorably with those from international reports of ventilatory support and weaning practices and from studies of implementation of weaning protocols.2,4,8,10,11,20 In a study8,35 by the Mechanical Ventilation International Study Group of 412 ICUs in North America, South America, Spain, and Portugal, the median duration of mechanical ventilation was 7 days. In randomized controlled trials3,22,30,36 of weaning protocols, median duration of ventilation ranged from 2.8 to 4.5 days. In our study the median duration of mechanical ventilation was 1.9 days for patients who did not have cardiac surgery. Our study sample had substantially more patients receiving mechanical ventilation because of postoperative respiratory failure and coma and fewer patients because of COPD and acute respiratory distress syndrome than reported by the Mechanical Ventilation International Study Group.8 In our study, only a few patients received mechanical ventilation because of COPD and acute respiratory distress syndrome, a situation that may have contributed to short overall durations of mechanical ventilation and ICU stay in the study cohort. However, previously reported studies8,11 do not appear to have accounted for the effect of censoring due to death on the calculation of median durations of mechanical ventilation, making direct comparison of our findings with the published literature somewhat problematic. Decisions made exclusively by nurses were less common for patients receiving ventilatory support for long periods. Arguably, the short duration of

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Table 6 Decisions made exclusively by nurses during mechanical ventilation

Indication for decision

Decisions made exclusively by nurses Total % (95% confi- Relative risk a (95% No. of decisions No. dence interval) confidence interval)

Reason for ventilation 1009

716

71 (68-74)

1

6

5

83 (36-99)

1.17 (0.82-1.68)

Other

214

154

72 (65-78)

1.01 (0.92-1.11)

Coma

733

475

65 (61-68)

0.91 (0.85-0.98)

Trauma

986

629

64 (61-67)

0.9 (0.85-0.96)

Sepsis

403

228

56 (52-61)

0.8 (0.73-0.88)

Postoperative respiratory failure Aspiration

63

35

56 (42-68)

0.78 (0.63-0.98)

Pneumoniab

420

233

55 (51-59)

0.78 (0.71-0.86)

Heart failure

66

35

53 (40-65)

0.75 (0.59-0.94)

Acute respiratory distress syndrome

14

7

50 (23-77)

0.70 (0.42-1.19)

Chronic obstructive pulmonary diseaseb

72

21

29 (19-41)

0.41 (0.28-0.61)

2749 1852

67 (66-69)

1

Neuromuscular cause

Duration of ventilation, d 0-7 7.1-14

537

274

51 (47-55)

0.76 (0.69-0.83)

14.1-28

278

157

56 (50-62)

0.83 (0.75-0.93)

>28

422

255

60 (56-65)

0.90 (0.83-0.97)