A Snapshot of the Oxygenation of Mechanically Ventilated Patients in One Australian Intensive Care Unit

Abstract

Hyperoxaemia in patients undergoing mechanical ventilation (MV) has been found to be an independent predictor of worse outcome and in-hospital mortality in some conditions. Data suggests that a fraction of inspired oxygen (FiO 2 ) of 0.4 or lower may produce hyperoxaemia although it is commonly accepted without adjustment in ventilator settings. The primary aim of this study was to observe current practice at one Australian tertiary intensive care unit (ICU) with regard to prescription and titration of oxygen (O 2 ) in patients undergoing MV, in particular whether they received higher FiO 2 than required according to arterial blood gas (ABG) results, and whether there was FiO 2 titration as a response to initial ABG results during the 12 hours following. A retrospective observational study of 151 ICU patients undergoing MV between November 2013 and February 2014 was conducted, with ABGs as the primary outcome measure. There were 250 ABG measures, with mean FiO 2 0.38 (range 0.3-1.0) and mean PaO 2 114 mmHg (standard deviation 36). Over all observations, 197 (79%) were of FiO 2 ≤0.4, however no patients were ventilated on room air (FiO 2 0.21) and 114 (46%) were in the hyperoxaemic range. Oxygen titration (up or down) occurred in 31% of patients. Morning ABGs were taken at a time suggested by ICU guidelines, and on review of these measures, the mean FiO 2 was lower than that purported to create toxicity. Subsequently, almost one-third of the cohort had their FiO 2 titrated, however there was a floor effect whereby 39%-43% of the cohort received an FiO 2 of 0.3.

Handling Oxygenation Targets in the Intensive Care Unit (HOT‐ICU)—Protocol for a randomised clinical trial comparing a lower vs a higher oxygenation target in adults with acute hypoxaemic respiratory failure

“…A recent meta‐analysis of trials in acutely ill patients overall underlined the potential detrimental effect of hyperoxaemia. Nevertheless, the tendency in ICUs is towards a liberal use of oxygen therapy and noteworthy, despite self‐reported restrictive preferences among ICU nurses and physicians . Importantly, hypoxaemia is associated with increased mortality as it may lead to a low tissue oxygen tension (PO 2 ).…”

“…This emphasises the importance of continuous pulse oximetry during restrictive oxygenation practices, and vigilance of the nursing staff to avoid or minimise episodes of definitive hypoxaemia. When such precautions are taken however, an oxygenation target of 8 kPa may be superior to the conventional liberal approach of oxygen supplementation observed in current clinical practice . Restrictive oxygenation is recommended in patients with chronic obstructive pulmonary disease (COPD) outside the ICUs targeting an arterial oxygen saturation measured by pulse oximetry (SpO 2 ) of 88% to 92%; in ICU patients with acute respiratory distress syndrome (ARDS) ‘low normoxaemia’’ defined as an arterial partial pressure of oxygen (PaO 2 ) from 7.3 to 10.7 kPa is often targeted, however, not recommended in current clinical guidelines due to lack of evidence …”

Arterial oxygen tensions in mechanically ventilated ICU patients and mortality: a retrospective, multicentre, observational cohort study

“…32e35 However, several observational studies report that the fraction of inspired oxygen (FIO 2 ) frequently remains unchanged even when the arterial blood gas (ABG) sample analysis indicated the presence of hyperoxaemia. 2,4,5,7,8,34,36 We conducted an observational study aiming to describe variations of PaO 2 and FIO 2 throughout the duration of invasive mechanical ventilation, and to assess the possible associations between degrees of hyperoxaemia and mortality in adult patients admitted to ICUs in the North Denmark Region. We hypothesised that hyperoxaemia would be associated with increased mortality.…”

Hyperoxemia among Pediatric Intensive Care Unit Patients Receiving Oxygen Therapy

“…12 In another study of mechanically ventilated adults, FiO 2 was never below 0.3. 14 We also found only 8.4% of FiO 2 values at 0.21, suggesting that clinicians may consider a low FiO 2 (0.21–0.30) as innocuous.…”