Meta-analyses of Bland–Altman-style cardiac output validation studies: good, but do they provide answers to all our questions?

<span class="paragraphSection">No one would deny the need for safe, reliable, and non-invasive cardiac output (CO) monitoring in anaesthesia and acute medicine. Measuring CO, or better still stroke volume (SV), adds a further dimension to haemodynamic monitoring as it completes the circulatory equation BP=CO×PR, where BP is blood pressure, PR is peripheral resistance, CO=SV×HR, and HR is heart rate. Clinical use of the pulmonary artery thermodilution catheter has been in decline since the 1990s,<a href="#aew442-B1" class="reflinks">¹</a> and newer, less invasive technologies have been developed that still need clinical evaluation.<a href="#aew442-B2" class="reflinks">²</a> Since its first description in 1986, the Bland–Altman method of determining accuracy and precision against a reference method, such as thermodilution, has become the gold standard in validation statistics.<a href="#aew442-B3" class="reflinks">³</a> In this month's edition of the Journal, one finds a 'state-of-the-art' systematic review and meta-analysis by Joosten and colleagues<a href="#aew442-B4" class="reflinks">⁴</a> that focuses on totally non-invasive and continuous CO monitoring technology and analyses published data extracted from Bland–Altman-style CO validation studies. It is one of a number of recent reviews published by this group that uses 'state-of-the-art' literature searches, paper selection, and statistical analysis technics to determine the overall accuracy and precision of the monitoring methods they review.<a href="#aew442-B5" class="reflinks">^5–7</a></span>

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