I found the recent article on pelvic angle during caesarean section (CS) by Kinsella and Harvey  extremely interesting. I believe it introduces a third variable for consideration during positioning for CS that other studies have not previously focused on. The actual tilt of the pelvis is, after all, the aim of tilting operating tables and using a wedge in this setting.
The first consideration is that of the optimal degree of tilt required to reduce clinically relevant aortocaval compression. This question has been the subject of numerous studies, and the National Institute for Health and Clinical Excellence recommendation is that a 15° tilt be applied during CS . However, there is likely to be inter-patient variability, with factors such as high body mass index, multiple pregnancy and polyhydramnios potentially impacting on aortocaval compression and thus the tilt required.
Second, the anaesthetist must decide how to achieve adequate tilt. Kinsella and Harvey suggest that both a wedge and table tilt achieve an adequate tilted position; however, the pelvic angle was significantly greater than the table tilt applied. I conducted a study (Petsas A, Smallman B. Use of lateral tilt during caesarean section: a survey of current practice amongst anaesthetists, obstetricians and operating department practitioners in a district general hospital. AAGBI Group of Anaesthetists in Training Annual Scientific Meeting, June 2011) at a district general hospital whereby 53 anaesthetists, obstetricians and operating department practitioners were asked to apply tilt to the operating table independently following spinal blockade for elective CS. They were then asked to estimate the degree of tilt they had applied and the actual tilt was measured using the iHandy Level© iPhone app. As in a prior study , my study reiterated that the perceived tilt applied to the operating tilt was grossly overestimated. Interestingly, in our study the degree of overestimation was greatest amongst obstetricians compared with anaesthetists, with a median (IQR) error of 14° (10°–25°) compared with 12° (5°–22°), respectively. This may reflect the fact that the obstetricians are considering the pelvic angle (which, as Kinsella and Harvey demonstrate, is greater than that applied to the table), whereas anaesthetists are placing more emphasis on the operating table tilt, assuming this to be aligned with the pelvic angle.
The final and most important consideration, therefore, is that of the actual tilt applied to the pelvis. In view of my study and in light of this recent article, it is apparent that any application of tilt thought to be applied to the pelvis is, at best, an educated estimate. I believe it emphasises the importance of re-evaluation of the patient's position during periods of haemodynamic instability. We must remain aware that the perceived tilt may not represent the actual pelvic tilt and aortocaval compression may still be a contributing factor. Possible methods of improving the adequacy of tilt are to liaise with the operating surgeon as to the perceived pelvic angle, use of a smartphone to assess the degree of table tilt, and the incorporation of a ‘tilt applied’ check box to the maternity World Health Organization checklist.