Oxygen levels in preterm babies are monitored with the aim of ensuring both adequate tissue oxygenation and to minimise the risk of oxygen toxicity and oxidative stress, and oxygen delivery is adjusted to achieve a certain target oxygen level. Liberal (higher oxygen level targeting) and restrictive (lower oxygen level targeting) in preterm babies are both thought to be associated with increased morbidity and mortality, and there is variation in practice regarding the optimal target oxygen range which will minimise these competing risks. This review will look at the evidence for the effectiveness of higher versus lower oxygen saturation target ranges in preterm babies, including the incidence of mortality, retinopathy of prematurity, bronchopulmonary dysplasia (BPD), necrotising enterocolitis, and neurodevelopmental impairment, to determine the optimal target oxygen range. Preterm babies frequently require oxygen therapy in order to maintain oxygen levels which are considered to be in the normal range. The goal of treatment is to maintain normoxia because there is evidence to show that both too much oxygen (hyperoxia) and too little oxygen (hypoxia) carry risks, and ideally babies should be monitored continually with an accurate non-invasive method. The gold standard method of measuring oxygen levels in preterm babies is through blood gas sampling from an arterial specimen. However, this technique has risks associated with the need for indwelling arterial lines, and removal of multiple blood samples, and it is not generally possible to maintain this method over long periods of time. The alternative methods of non-invasive oxygen monitoring include transcutaneous measurement, and measuring oxygen saturation using pulse oximetry. Transcutaneous monitors use a small probe which contains an oxygen sensing electrode attached to the skin. The skin has to be “arterialised” by warming in order to ensure that the oxygen tension between the superficial skin and that of the tissue supplied by the capillaries below comes into equilibrium, allowing sampling of the gas which lies just above the skin surface. This method produces a result which is expressed (like a blood gas) in terms of the partial pressure of oxygen (PaO). This method requires more user knowledge to calibrate and set up, and the probes require frequent re-siting to avoid marking the fragile skin of the preterm baby. Pulse oximeters use a combination of two wavelengths of light which are passed through tissue (e.g. the finger, earlobe, or infant foot) and then detected as they emerge. The absorption of the electromagnetic energy by the interrogated tissue varies according to the percentage of oxygen which is bound to haemoglobin. The value of peripheral capillary oxygen saturation (SpO) is calculated from the ratio of the absorption at the two wavelengths. The absorption also varies with the cardiac rhythm, and this is used to extract only the portion which is “pulsatile”. Pulse oximetry is a safe technique but there is a degree of uncertainty over its accuracy, particularly in the higher range of oxygen saturations. The aim of this review is to determine which method of measuring oxygen levels is the most accurate at detecting hyperoxia and hypoxia and to evaluate the risks and benefits associated with each method, in order to determine which is the most appropriate for use in various clinical situations. Carbon dioxide is cleared by healthy lung tissue, and can build up when there is respiratory failure. Cerebral blood flow is affected by carbon dioxide levels, and alterations in cerebral blood flow predispose a preterm baby’s vulnerable brain to peri/intraventricular haemorrhage (P/IVH) and/or periventricular leukomalacia (PVL). Monitoring of carbon dioxide levels is crucial during artificial ventilation, but evidence of lung injury induced by volutrauma has led to efforts to reduce this damage, with “permissive hypercapnia” (allowing elevated carbon dioxide levels in the blood) becoming a common lung protective strategy in ventilated preterm babies. However, the safety and the optimal range of carbon dioxide values for permissive hypercapnia are not clear. This review aims to identify the optimal levels of carbon dioxide in the management of preterm babies in order to improve outcomes. Preterm babies are regularly monitored to ensure adequate systemic perfusion (oxygen supply to tissues). In combination with clinical observations, biochemical parameters, urine output and clinical examination, blood pressure (BP) can be used as a surrogate marker for systemic perfusion. Depending on the clinical condition of the baby, blood pressure may be continuously monitored via an indwelling arterial catheter placed in either an umbilical or peripheral artery, and in more stable babies it may be measured non-invasively using the oscillometric (cuff-reading) technique. The optimal target range for BP in babies of different gestational ages and weights is not precisely known, but observational studies have defined a “normal” range present in babies who have an uncomplicated course. Identifying babies with reduced tissue oxygen supply who would benefit from intervention is clinically difficult, as it is not known what specific BP range is associated with adequate perfusion and better long term outcomes. This review aims to compare outcomes with the use of invasive monitoring versus oscillometric measurements, and between different target blood pressure ranges in preterm babies on invasive respiratory support, to identify if a specific approach to both blood pressure monitoring and blood pressure management is associated with better outcomes.