Volume 189 - Issue 9
Respiratory rate: the neglected vital sign
Authors: Allen C Cheng, James F Black and Kirsty L Buising
Med J Aust 2008; 189 (9): 531-532. || doi: 10.5694/j.1326-5377.2008.tb02163.x
Published online: 3 November 2008
Published online: 3 November 2008
To the Editor: We note with interest the recent commentary by Cretikos et al on the predictive value of a high respiratory rate for adverse outcomes.1 We wish to provide empirical evidence from Australian patients with pneumonia in support of their view that simple clinical parameters are good predictors of adverse outcomes.
We examined data from a prospective cohort of consecutive patients presenting to the Royal Melbourne Hospital Emergency Department with radiologically confirmed, community-acquired pneumonia between 2003 and 2006.2 In an earlier study of a subset of these patients,3 we found that hypotension and tachypnoea were strongly associated with death and/or the need for respiratory/inotropic support (odds ratios, 8.0 and 3.5, respectively).
In the full cohort (n = 740), we examined factors associated with either admission to the intensive care unit (ICU) or mortality (106 patients were in one of these two categories). Respiratory rate was documented in 712 patients (96%). A combination of tachypnoea (≥ 24 breaths/min) and/or hypotension (systolic blood pressure ≤ 90 mmHg) had similar predictive value for the risk of ICU admission and/or death to the recommended system of risk stratification, the Pneumonia Severity Index (PSI)4 (Box). The combination of respiratory rate and systolic blood pressure performed better than either sign alone in ruling out at-risk patients if both were normal (ie, a high negative predictive value), although almost a quarter of patients with either clinical sign had adverse outcomes.
The PSI is based on 20 individual clinical and laboratory parameters, and evidence suggests that it is poorly documented in patients’ records.5 Our data relate to patients with community-acquired pneumonia from a single centre and thus have limited statistical power for making comparisons. However, they suggest that these two routinely measured clinical parameters can be used to stratify patients at risk of adverse outcomes at the time of presentation. We support efforts to incorporate simple clinical indicators into systems that can identify seriously unwell patients early in the course of illness.
Summary statistics for tachypnoea, hypotension and PSI class as predictors of ICU admission and/or death from community-acquired pneumonia*
References
- Cretikos MA, Bellomo R, Hillman K, et al. Respiratory rate: the neglected vital sign. Med J Aust 2008; 188: 657-659.
- Buising KL, Thursky KA, Black JF, et al. A prospective comparison of severity scores for identifying patients with severe community acquired pneumonia: reconsidering what is meant by severe pneumonia. Thorax 2006; 61: 419-424. 0_i1091914
- Buising KL, Thursky KA, Black JF, et al. Identifying severe community-acquired pneumonia in the emergency department: a simple clinical prediction tool. Emerg Med Australas 2007; 19: 418-426. 0_i1091916
- Fine MJ, Auble TE, Yealy DM, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med 1997; 336: 243-250. 0_i1091918
- Maxwell DJ, McIntosh KA, Pulver LK, Easton KL. Empiric management of community-acquired pneumonia in Australian emergency departments. Med J Aust 2005; 183: 520-524. 0_i1091920