Prehospital Noninvasive Ventilation: A Viable ...

PREHOSPITAL NONINVASIVE VENTILATION: A VIABLE TREATMENT OPTION IN THE URBAN SETTING David McD. Taylor, MD, MPH, DRCOG, Stephen A. Bernard, MD, Kevin Masci, DipHealthSci, Catherine E. MacBean, BA, Marcus P. Kennedy, MBBS

INTRODUCTION

Prehosp Emerg Care Downloaded from informahealthcare.com by Monash University on 12/02/12 For personal use only.

ABSTRACT Objective. To determine the viability of prehospital noninvasive ventilation (NIV) as a prelude to a definitive clinical trial. Methods. This was a retrospective observational study of patients (aged >55 years, severe shortness of breath) transported to a tertiary emergency department (10/5/03– 12/28/04). Data were extracted from paramedic and hospital medical records. The primary outcome measure was the number of patients who could potentially benefit from prehospital NIV. They were defined as “conscious upon paramedic arrival and who required ventilatory support (bag/valve/mask ventilation [BVM], NIV or endotracheal intubation) during transport or within 30 minutes of arrival at the emergency department (ED).” The secondary outcome measures were the effectiveness of existing paramedic treatment regimens and paramedic management times. Results. Two hundred sixtyfour patients were enrolled (mean age 75.5 ± 8.7 years, 59.1% male). Sixty-seven patients (25.4%, 95% CI: 20.3–31.2) met the primary outcome measure: 31 (11.7%, 95% CI: 8.2–16.4) received prehospital BVM, an additional 35 (13.3%, 95% CI: 9.5– 18.1) received NIV in the ED and one (0.4%, 95% CI: 0.0–2.4) was intubated in the ED. Prehospital treatment resulted in significant (p < 0.001) improvements in systolic blood pressure (151.2 dropping to 144.2 mmHg), respiratory rate (29.4 dropping to 26.3 breaths/minute), and oxygen saturation (92.3% rising to 96.2%). Median paramedic management time was 33 minutes (IQR 29–40). Conclusion. Prehospital treatment significantly improved patient vital signs. However, a considerable proportion of patients still required ventilatory support either prehospital or early in their ED course. Further research is indicated to determine if these patients would benefit from prehospital NIV. Key words: emergency medical services; ventilation; continuous positive airways pressure.

Noninvasive ventilation (NIV) is the provision, via nasal or face mask, of continuous positive airways pressure (cPAP) or bilevel noninvasive ventilation (BiPAP). This treatment has been shownto be effective for patients with severe respiratory distress due to acute severe pulmonary edema (ASPE) or exacerbation of chronic obstructive pulmonarydisease (COPD).1 It is now routinely used in many emergency departments (ED) and intensive care units (ICU).1−3 The use of NIV has been shown to decrease the requirement for endotracheal intubation and may decrease hospital length of stay and mortality.1,2,4−6 It is not known, however, whether NIV is appropriate for patients with acute respiratory distress due to ASPE or COPD in the prehospital setting. Intuitively, the provision of a proven treatment modality like NIV, as soon as possible in the patients’ management, would be expected to result in improved patient outcomes. Indeed, it is possible that NIV may avoid the need for intubation in patients who do not respond to medical therapy. Because intubation is associated with considerable morbidity, mortality, and increased length of hospital stay, the potential for avoidance of intubation by using prehospital NIV would be of considerable clinical significance. The determination of whether prehospital NIV is a viable treatment option needs to include a consideration of the magnitude and clinical relevance of improved patient outcomes and the difficulties inherent in the provision of this treatment. The equipment can be expensive and requires additional gas (air and/or oxygen) usage and paramedic training. In addition, the incidence of failure of current optimized prehospital treatment regimens is not known. Several small studies7,8 have investigated prehospital NIV and, although the authors have demonstrated improvements in a range of clinical end points, they have not clarified the usefulness of this treatment in this setting. More recently, a nonrandomized prehospital trial of patients with ASPE showed that the addition of cPAP to standard pharmacological treatment significantly reduced intubation and mortality rates compared to standard treatment alone.6 We aimed to undertake a descriptive pilot study to explore the potential for prehospital NIV as a viable treatment option. Specifically, we aimed to determine

PREHOSPITAL EMERGENCY CARE 2008;12:42–45

Received December 10, 2006, from the Emergency Medicine Research, Austin Health, Australia (DMT); Medical Advisor, Metropolitan Ambulance Service, Melbourne, Australia (SAB); Paramedic Education and Training Metropolitan Ambulance Service, Melbourne, Australia (KM); Emergency Department, Royal Melbourne Hospital, Australia (CEM, MPK); Emergency Department, Bendigo Hospital, Australia (SZ). Revision received April 28, 2007; accepted for publication May 15, 2007. Address correspondence and reprint requests to: David Taylor, Department of Emergency Medicine, Austin Health, Studley Road, Heidelberg, Victoria Australia 3084. e-mail: [email protected] doi: 10.1080/10903120701710389

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the number of patients who were likely to benefit from prehospital NIV and the effectiveness of existing prehospital treatment regimens. It was planned that these data would inform the development of a large prehospital clinical trial examining the effectiveness of this treatment modality in this setting.

METHODS

demographics, first sets of vital signs (paramedic and ED), management, time interval between paramedic arrival at the patient and arrival at the ED, diagnoses (paramedic and ED), and outcomes. One investigator (DT) extracted all data from the PCRs. A second investigator (CM) extracted all data from the hospital medical records. For both datasets, a reexamination of random samples of 10% of records confirmed the accuracy of the data extracted.

Study Design This was a retrospective observational pilot study.


Study Population and Setting Patients transported by paramedics of the Metropolitan Ambulance Service (MAS) to the ED of an inner-city hospital (10/5/03–12/28/04, inclusive) were eligible for enrolment. Inclusion criteria were age greater than 55 years, the call to MAS recorded a chief complaint of severe breathing difficulty, treatment provided by a MAS paramedic, and transportation to the study ED. There were no exclusion criteria. The ED is a tertiary referral and trauma centre in Melbourne, Australia, with an annual census of approximately 55,000 patients.

Human Subject Committee Review The hospital’s Human Research and Ethics Committee (Institutional Review Board) and the Research Committee of MAS approved the study. The requirement for written informed patient consent was waived.

Experimental Protocol The MAS is the provider of emergency medical services for the city of Melbourne, an Australian city of almost 4 million people. The service is two tier, with mobile intensive care (MICA) paramedics trained in advanced life support including endotracheal intubation and venous cannulation, and authorized to administer a wide range of drugs according to medically determined standing orders.9 In addition to medical therapy, patients with coma due to respiratory failure may be intubated by using sedative agents, if needed. Calls to MAS are triaged by the Emergency Services Telecommunication Authority (ESTA) using the Advanced Medical Priority Dispatch System (AMPDS). At least one MICA paramedic is dispatched to patients with a chief complaint of severe breathing difficulty. The ESTA provided a list of patients who met the study entrance criteria. The paramedic patient care records (PCRs) and the corresponding hospital medical records were then retrieved. Data were extracted by using explicit data collection documents that had been designed specifically for the study, trialed, and revised prior to use. Extracted data included patient

Key Outcome Measures The primary outcome measure was the number of patients who could potentially benefit from prehospital NIV. They were defined as “conscious upon paramedic arrival and who required ventilatory support (bag/valve/mask ventilation [BVM], NIV or endotracheal intubation) prehospital or within 30 minutes of arrival at the ED.” The secondary outcome measures were the effectiveness of existing paramedic treatment regimens and paramedic management times.

Analytical Methods Most results are reported descriptively, with 95% confidence intervals (CI) fitted around simple proportions. Comparison of vital signs data used the Wilcoxon signed rank test, because data were not normally distributed. Epicalc 200010 and SPSS for Windows software11 were used for all analyses.

Sample Size Determination The sample size calculation was based on an expected clinically significant improvement in oxygen saturation after paramedic treatment. To demonstrate a 5% (SD 10%) increase between the arrival of the paramedics and arrival at the ED, at least 63 patients had to be enrolled (each patient acting as his/her own control, level of significance 0.05, power 0.8). However, it was planned to enroll approximately 300 consecutive patients as this number was expected to provide more meaningful data relating to the primary outcome measure that would inform the development of subsequent studies in this area.

RESULTS A total of 301 patients meeting the entry criteria were identified. Five were ultimately transported to another hospital, and the records of 32 patients were unavailable from the hospital. Hence, 264 patients comprised the final study sample. These patients had a mean age of 75.5 ± 8.7 years (median 76) and 156 (59.1%, 95% CI: 52.9–65.0) were male. Sixty-seven (25.4%, 95% CI: 20.3–31.2) patients met the primary outcome measure. Thirty-one (11.7%, 95%

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JANUARY/MARCH 2008

VOLUME 12 / NUMBER 1

TABLE 1. The First Set of Vital Signs Recorded by Paramedics and the Emergency Department Paramedics


Heart rate (beats/min) Blood pressure (mmHg) Respiratory rate (breaths/min) Oxygen saturation (%) Glascow coma score

Median (IQ range)

Missing

Median (IQ range)

Missing

p value

100 (84–120) 150 (120–180) 30 (22–36) 95.5 (88.75–98) 15 (15–15)

5 8 4 58 4

100 (80–123.25) 144 (122–162) 24 (20–30.5) 98 (95–99) 15 (15–15)

3 2 3 4 1

0.061