Comparing the ratio of respiratory dead space volume to tidal volume in supine and prone positions in patients under general anesthesia


Introduction: The prone position in the surgery room provides the surgeon with access to the area of surgery in various types of surgeries. The effects of prone position on respiratory gas exchanges are complex. Methods: This prospective cohort study was performed on 61 patients undergoing general anesthesia in prone and supine positions. Half an hour after intubation, 2 hours after anesthesia and before extubation in recovery, arterial blood gas changes, ETCO2, respiratory dead space volume to tidal volume ratio (VD / VT), and hemoglobin levels in both groups were measured and recorded. Findings: Sixty one patients (29 patients in supine and 32 patients in prone positions) were evaluated. There was no significant relationship between VD/VT ratio during anesthesia between the two groups (P = 0.16). In examining this ratio at different measurement times, the results showed that only in supine group, VD / VT relationship was statistically significant two hours after anesthesia onset and at the end of anesthesia (P=0.01). There were no significant differences in pH, PCO2, PECO2, Ppeak and PaO2 in the two groups at different time points. Hb levels were statistically significant in both groups at different time points; but the difference between the two groups was not significant. Conclusion: The ratio of respiratory dead space volume to tidal volume and oxygenation in the prone position compared to supine position was not changed in patients undergoing general anesthesia with mechanical ventilation. The process of oxygenation changes in the prone position has improved over time.


  • Bassampour S, Aliasgharpoor M, Mehran A, Prizad H (2008) Effect of Prone Position on Oxygenation in Patients Undergoing Mechanical Ventilation. Hayat 14.
  • Casati A, Salvo I, Torri G, Calderini E (1997) Arterial to end-tidal carbon dioxide gradient and physiological dead space monitoring during general anaesthesia: effects of patients’ position. Minerva anestesiologica 63(6): 177-82.
  • Charron C, Repesse X, Bouferrache K, Bodson L, Castro S, Page B, et al. (2011) PaCO 2 and alveolar dead space are more relevant than PaO 2/FiO 2 ratio in monitoring the respiratory response to prone position in ARDS patients: a physiological study. Critical Care 15(4): R175.
  • Cornejo RA, Díaz JC, Tobar EA, Bruhn AR, Ramos CA, González RA, et al. (2013) Effects of prone positioning on lung protection in patients with acute respiratory distress syndrome. American journal of respiratory and critical care medicine 188(4): 440-8.
  • Dalmedico MM, Salas D, Oliveira AMd, Baran FDP, Meardi JT, Santos MC (2017) Efficacy of prone position in acute respiratory distress syndrome: overview of systematic reviews. Revista da Escola de Enfermagem da USP 51.
  • Edgcombe H, Carter K, Yarrow S (2008) Anaesthesia in the prone position. British journal of anaesthesia 100(2): 165-83.
  • Haddam M, Zieleskiewicz L, Perbet S, Baldovini A, Guervilly C, Arbelot C, et al. (2016) Lung ultrasonography for assessment of oxygenation response to prone position ventilation in ARDS. Intensive care medicine 42(10): 1546-56.
  • Hu SL, He HL, Pan C, Liu AR, Liu SQ, Liu L, et al. (2014) The effect of prone positioning on mortality in patients with acute respiratory distress syndrome: a meta-analysis of randomized controlled trials. Critical care 18(3): R109.
  • Intagliata S, Rizzo A, Bhimji SS (2019) Physiology, Lung Dead Space. StatPearls [Internet]: StatPearls Publishing.
  • Jahani S, Soleymani ZH, Asadizaker M, Soltani F, Cheraghian B (2018) Determination of the Effects of Prone Position on Oxygenation in Patients with Acute Respiratory Failure Under Mechanical Ventilation in ICU. Journal of Medicine and Life 11(4): 274.
  • Johnson NJ, Luks AM, Glenny RW (2017) Gas exchange in the prone posture. Respiratory care 62(8): 1097-1100.
  • Knight DJ, Mahajan RP (2004) Patient positioning in anaesthesia. Continuing Education in Anaesthesia, Critical Care & Pain 4(5): 160-3.
  • Koulouras V, Papathanakos G, Papathanasiou A, Nakos G (2016) Efficacy of prone position in acute respiratory distress syndrome patients: a pathophysiology-based review. World journal of critical care medicine 5(2): 121.
  • Kozier B, Erb GL (2004) Kozier & Erb’s techniques in clinical nursing: Basic to intermediate skills: Prentice Hall.
  • Kwee MM Ho Y-H, Rozen WM (2015) The prone position during surgery and its complications: a systematic review and evidence-based guidelines. International surgery 100(2): 292-303.
  • Landi A, Corradetti E, Mancarella C, Delfini R (2013) Prevention of Complications Related to Patient Prone Positioning during Spinal Neurosurgical Care: A Nursing Point of View. J Spine Neurosurg 2: 2. of 4:2.
  • Mezidi M, Parrilla FJ, Yonis H, Riad Z, Böhm SH, Waldmann AD, et al. (2018) Effects of positive end-expiratory pressure strategy in supine and prone position on lung and chest wall mechanics in acute respiratory distress syndrome. Annals of intensive care 8(1): 86.
  • Palmese S, Manzi M, Scibilia A (2014) Changes in alveolar dead space during general anaesthesia in posterior spinal surgery. An observational study. Internet J Anaesthesiol 33: 1.
  • Reutershan J, Schmitt A, Dietz K, Unertl K, Fretschner R (2006) Alveolar recruitment during prone position: time matters. Clinical science 110(6): 655-63.
  • Robak O, Schellongowski P, Bojic A, Laczika K, Locker GJ, Staudinger T (2011) Short-term effects of combining upright and prone positions in patients with ARDS: a prospective randomized study. Critical Care 15(5): R230.
  • Santini A, Protti A, Langer T, Comini B, Monti M, Sparacino CC, et al. (2015) Prone position ameliorates lung elastance and increases functional residual capacity independently from lung recruitment. Intensive care medicine experimental 3(1):17.
  • Soro M, Garcia-Perez M, Belda F, Ferrandis R, Aguilar G, Tusman G, et al. (2007) Effects of prone position on alveolar dead space and gas exchange during general anaesthesia in surgery of long duration. European journal of anaesthesiology 24(5): 431-7.
  • St-Arnaud D, Paquin M-J (2008) Safe positioning for neurosurgical patients. AORN journal 87(6): 1156-72.
  • Tang R, Huang Y, Chen Q, Hui X, Li Y, Yu Q, et al. (2012) The effect of alveolar dead space on the measurement of end-expiratory lung volume by modified nitrogen wash-out/wash-in in lavage-induced lung injury. Respiratory care 57(12): 2074-81.
  • Wahba R, Tessler M, Kardash K (1998) Carbon dioxide tensions during anesthesia in the prone position. Anesthesia & Analgesia 86(3): 668-9.
  • Welch MB, Wahr J, Crowley M (2015) Patient positioning for surgery and anesthesia in adults. UpToDate; 2018. Kallet RH. A comprehensive review of prone position in ARDS. Respiratory care 60(11): 1660-87.
  • Yagui ACZ, Beppu OS (2007) Effect of prone position without PEEP on oxygenation and complacency in an experimental model of lung injury. Jornal de pediatria 83(4): 343-8.
  • Zhang Q, Li Y, Xin X, Yin C, Gao F, Guo Y, et al. (2017) Effects of prone position on lung function of patients undergoing mechanical ventilation under total intravenous anesthesia. Int J Clin Exp Med 10(4): 6769-74.


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