Sleep disturbances and residual neuromuscular blockade: future research possibilities We read with great interest the article by Christensson et al. [1] investigating how partial neuromuscular blockade interferes with the regulation of breathing in patients with obstructive sleep apnoea (OSA). This was a physiological study performed in 10 unsedated male volunteers. These findings are very important, given the high prevalence of OSA and how it can influence the use of neuromuscular blocking drugs and reversal agents. Additionally, it highlights the importance of implementing 1 month of nightly home continuous positive airways pressure (CPAP) treatment in OSA patients before major surgery. However, we should like to make some observations regarding the methodology used by Christensson et al. and suggest how future studies might be designed in order to improve knowledge in this area, as well as to extend the discussion to include other factors that may also influence postoperative breathing regulation in patients. Although the methodology was sound, of the 10 patients recruited, only three completed the entire protocol and it would be interesting to replicate the protocol using a much larger sample. In a cohort study of 2646 patients with OSA, for example, it was shown that patients who had not been treated pre-operatively with CPAP (n=1465) were at increased risk for postoperative cardiopulmonary complications [2]. In addition, according to the study by Christensson et al., the patients were recruited and diagnosed by specialists in sleep medicine using the Embletta â (Embla, Broomfield, CO, USA) portable diagnostic system; In-lab polysomnography might have been used instead as it takes into account more variables and is more effective in diagnosing sleep disturbances than the Embletta. In addition to obstructive apnoea syndrome, central apnoea syndrome and hypoventilation/hypoxaemia associated with sleep [3] may also be related to postoperative hypoxaemia and might consequently interfere with breathing regulation in postoperative patients with residual neuromuscular blockade. Residual neuromuscular blockade is an important postoperative condition and is largely associated with pulmonary complications and critical respiratory events. In this context, considering and understanding how comorbidities may influence this can help, not only to improve therapeutic approaches to this condition, but also to prevent respiratory complications requiring tracheal re- intubation and unplanned admission to critical care. Sleep disturbances are particularly hazardous, can impair breathing control and, as the study itself demonstrates, may alter the effect of conditions such as residual neuromuscular blockade. Broader studies, focusing on OSA and other sleep disorders, would increase the understanding of breathing regulation changes in patients with residual neuromuscular blockade, including the dynamics of these conditions. Acknowledgements Our studies are supported by the Associac ß~ ao Fundo de Incentivo  a Pesquisa (AFIP). ST and MA also received support from the Conselho Nacional de Desenvolvimento Cient  ıfico e Tecnol  ogico (CNPq). No competing interests declared. M. Medina S. Tufik M. L. Andersen Universidade Federal de S~ ao Paulo, S~ ao Paulo, Brazil Email: ml.andersen12@gmail.com References 1. Christensson E, Ebberyd A, H  ardemark Cedborg A, et al. Hypoxic ventilatory response after rocuronium-induced partial neuromuscular blockade in men with obstructive sleep apnoea. Anaesthesia 2020; 75: 338–47. 2. Abdelsattar ZM, Hendren S, Wong SL, Campbell DA Jr, Ramachandran SK. The impact of untreated obstructive sleep apnea on cardiopulmonary complications in general and vascular surgery: a cohort study. Sleep 2015; 38: 1205–10. 3. American Academy of Sleep Medicine. International Classification of Sleep Disorders. 3rd ed. Darien, IL: American Academy of Sleep Medicine. doi:10.1111/anae.14912 552 © 2020 Association of Anaesthetists Anaesthesia 2020, 75, 550–559 Correspondence