Pulmonology Pulmonology
Rev Port Pneumol 2014;20:51-2 - Vol. 20 Num.1 DOI: 10.1016/j.rppneu.2013.12.002
Letter to editor
Reply to “Obstructive sleep apnea prevalence and adverse respiratory events in surgical patients”
Resposta a “Prevalência de apneia obstrutiva do sono e eventos respiratórios adversos em pacientes cirúrgicos”
Helder Pereiraa, Daniela Xaráa, Júlia Mendonçaa, Alice Santosa, Fernando Abelhaa,b,,
a Department of Anesthesiology, Centro Hospitalar de São João, Porto, Portugal
b Anesthesiology and Perioperative Care Unit, Surgical Department of Medical School of Porto, Porto, Portugal

We thank Dr. Ricardo Reis and Ana Antunes for their interest in our manuscript and for the comments related to our observational study.1 We agree that not having done polysomnography on our patients was a limitation of the study but as it is stated by Chung et al.2: “owing to its high sensitivity at a score of ≥3, the STOP Bang questionnaire is considered very helpful to rule out patients having moderate and severe OSA.” As we state in introduction section although polysomnography (PSG) is considered the gold standard for the diagnosis of OSA it is not performed as a routine preoperative assessment tool for OSA patients in our hospital because it is an expensive and labor-intensive test. We choose STOP questionnaire because it has been considered a practical step forward in identifying patients with OSA and because of the known sensitivity and specificity in diagnosing OSA. We agree that we may have a lower incidence of OSA patients compared to the report incidence of High Risk of OSA patients. That is why we reported the results of our study considering a group of patients we have named specifically High Risk of OSA because we agree we could not confirm the OSA diagnosis in all patients.

Indeed HR-OSA was not a risk factor for Acute Respiratory Events considered as a unique group; in our study only mild/moderate hypoxia had a higher incidence in HR-OSA patients. We agree with you and that is stated in discussion section “there was a greater risk of postoperative hypoxemia in HR-OSA patients in comparison with those without the diagnosis. However, in our study…analysis of perioperative adverse events did not show significant respiratory morbidity in HR-OSA patients compared to the LR-OSA patients. In fact in our study we did not find that HR-OSA was a determinant for ARE.”

We think that we should be little cautious concluding “previous papers have shown that OSA itself is associated with a statistically significant higher incidence of respiratory complications” or at least understand some limitations of these studies. In fact there are studies (by Liao Pu3 and Gupta RM4) that apparently have succeeded in demonstrating that patients with OSA have a higher incidence of postoperative complications compared with matched non-OSA surgical patients. In the study by Liao PU3 Oxygen desaturation with SpO2 < 90% was also the most common complication but this study has also a limitation with the sampling methodology for group selection that should be addressed.

In the study of Gupta RM4 the authors concluded that adverse outcomes were more common in OSA patients but the considered outcomes included other complications and even in what concerns respiratory complications they too failed to demonstrate that respiratory complications were more frequent in OSA group of patients. In their study even episodic hypoxia was not more frequent in OSA patients.

In the study by Memtsoudis S5 OSA was considered an independent risk factor for perioperative pulmonary complications although their considered outcomes were clearly different and the studied respiratory complications were pneumonia, ARDS and respiratory failure. We may think that it is fundamental to verify if these acute events occurring at PACU are related to respiratory failure occurring after discharge from the PACU and perhaps this could be a challenge to future investigation.

Conflicts of interest

The authors have no conflicts of interest to declare.

H. Pereira,D. Xara,J. Mendonca,A. Santos,Abelha FJ:
Patients with a high risk for obstructive sleep apnea syndrome: Postoperative respiratory complications
Rev Port Pneumol, 19 (2013), pp. 144-151 http://dx.doi.org/10.1016/j.rppneu.2013.01.003
F. Chung,R. Subramanyam,P. Liao,E. Sasaki,C. Shapiro,Sun Y:
High STOP-Bang score indicates a high probability of obstructive sleep apnoea
Br J Anaesth, 108 (2012), pp. 768-775 http://dx.doi.org/10.1093/bja/aes022
P. Liao,B. Yegneswaran,S. Vairavanathan,P. Zilberman,Chung F:
Postoperative complications in patients with obstructive sleep apnea: a retrospective matched cohort study
Can J Anaesth, 56 (2009), pp. 819-828 http://dx.doi.org/10.1007/s12630-009-9190-y
R.M. Gupta,J. Parvizi,A.D. Hanssen,Gay PC:
Postoperative complications in patients with obstructive sleep apnea syndrome undergoing hip or knee replacement: a case-control study
Mayo Clin Proc, 76 (2001), pp. 897-905 http://dx.doi.org/10.4065/76.9.897
S. Memtsoudis,S.S. Liu,Y. Ma,Y.L. Chiu,J.M. Walz,L.K. Gaber-Baylis,Mazumdar M:
Perioperative pulmonary outcomes in patients with sleep apnea after noncardiac surgery
Anesth Analg, 112 (2011), pp. 113-121 http://dx.doi.org/10.1213/ANE.0b013e3182009abf
Corresponding author. (Fernando Abelha fernando.abelha@gmail.com)
Copyright © 2013. Sociedade Portuguesa de Pneumologia
Rev Port Pneumol 2014;20:51-2 - Vol. 20 Num.1 DOI: 10.1016/j.rppneu.2013.12.002
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