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  • 1.
    Edmark, Lennart
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Clinical Research, County of Västmanland. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Reducing Atelectasis during General Anaesthesia – the Importance of Oxygen Concentration, End-Expiratory Pressure and Patient Factors: A Clinical Study Exploring the Prevention of Atelectasis in Adults2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: The use of pure oxygen during preoxygenation and induction of general anaesthesia is a major cause of atelectasis. The interaction between reduced lung volume, resulting in airway closure, and varying inspiratory fractions of oxygen (FIO2) in determining the risk of developing atelectasis is still obscure.

    Methods: In this thesis, computed tomography (in studies I and II during anaesthesia, in studies III and IV postoperatively) was used to investigate the area of atelectasis in relation to FIO2 and varying levels of continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP).

    Study I investigated the short-term influence of reducing FIO2 during preoxygenation and induction of general anaesthesia, and the time to hypoxia during apnoea.

    Study II focused on the long-term effect of an FIO2 of 0.8 for preoxygenation.

    Study III applied CPAP/PEEP with an FIO2 of 1.0 or 0.8 for pre- and postoxygenation until extubation. After extubation, CPAP with an FIO2 of 0.3 was applied before the end of mask ventilation.

    Study IV compared two groups given CPAP/PEEP during anaesthesia and an FIO2 of 1.0 or 0.3 during postoxygenation, but without CPAP after extubation.

    Results: Study I showed a reduction in atelectasis with an FIO2 of 0.8 or 0.6, compared with 1.0, but the time to hypoxia decreased. In study II, atelectasis evolved gradually after preoxygenation. In study III, atelectasis was reduced with an FIO2 of 1.0 and CPAP/PEEP compared with an FIO2 of 1.0 without CPAP/PEEP. The intervention failed in the group given an FIO2 of 0.8, this group had more smokers. Atelectasis and age were correlated. In study IV, no difference was found between the groups. Post hoc analysis showed that smoking and ASA class increased the risk for atelectasis.

    Conclusion, the effect of reducing FIO2 during preoxygenation to prevent atelectasis might be short-lived. A lower FIO2 shortened the time to the appearance of hypoxia. Increasing lung volume by using CPAP/PEEP also decreased the risk of atelectasis, but the method might fail; for example in patients who are heavy smokers. In older patients care must be taken to reduce a high FIO2 before ending CPAP.

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  • 2.
    Edmark, Lennart
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Clinical Research, County of Västmanland.
    Auner, U
    Lindbäck, Johan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, UCR-Uppsala Clinical Research Center.
    Enlund, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, UCR-Uppsala Clinical Research Center.
    Hedenstierna, Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Post-operative atelectasis: a randomised trial investigating a ventilatory strategy and low oxygen fraction during recovery2014In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 58, no 6, p. 681-688Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Atelectasis is common during and after general anaesthesia. We hypothesized that a ventilation strategy with a combination of 1) continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) and 2) a reduced end-expiratory oxygen concentration during recovery would reduce post-operative atelectasis.

    METHODS: Sixty patients were randomized into two groups. During anaesthesia induction, inspiratory oxygen fraction (FI O2 ) was 1.0, and depending on weight, CPAP 6, 7 or 8 cmH2 O was applied in both groups via facemask. During maintenance of anaesthesia, a laryngeal mask airway (LMA) was used, and PEEP was 6-8 cmH2 O in both groups. Before removal of the LMA, FI O2 was set to 0.3 in the intervention group and 1.0 in the control group. Atelectasis was studied by computed tomography (CT) approximately 14 min post-operatively.

    RESULTS: In one patient in the group given an FI O2 of 0.3 before removal of the LMA a CT scan could not be performed so the patient was excluded. The area of atelectasis was 5.5, 0-16.9 cm(2) (median and range), and 6.8, 0-27.5 cm(2) in the groups given FI O2 0.3 or FI O2 1.0 before removal of the LMA, a difference that was not statistically significant (P = 0.48). Post-hoc analysis showed dependence of atelectasis on smoking (despite all were clinically lung healthy) and American Society of Anesthesiologists class (P = 0.038 and 0.015, respectively).

    CONCLUSION: Inducing anaesthesia with CPAP/PEEP and FI O2 1.0 and deliberately reducing FI O2 during recovery before removal of the LMA did not reduce post-operative atelectasis compared with FI O2 1.0 before removal of the LMA.

  • 3.
    Edmark, Lennart
    et al.
    Departments of Anaesthesiology and Intensive Care, Central Hospital, Västerås, Sweden.
    Auner, Udo
    Enlund, Mats
    Departments of Anaesthesiology and Intensive Care, Central Hospital, Västerås, Sweden.
    Östberg, Erland
    Hedenstierna, Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Oxygen concentration and characteristics of progressive atelectasis formation during anaesthesia2011In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 55, no 1, p. 75-81Article in journal (Refereed)
    Abstract [en]

    Background:

    Atelectasis is a common consequence of pre-oxygenation with 100% oxygen during induction of anaesthesia. Lowering the oxygen level during pre-oxygenation reduces atelectasis. Whether this effect is maintained during anaesthesia is unknown.

    Methods:

    During and after pre-oxygenation and induction of anaesthesia with 60%, 80% or 100% oxygen concentration, followed by anaesthesia with mechanical ventilation with 40% oxygen in nitrogen and positive end-expiratory pressure of 3 cmH2O, we used repeated computed tomography (CT) to investigate the early (0–14 min) vs. the later time course (14–45 min) of atelectasis formation.

    Results:

    In the early time course, atelectasis was studied awake, 4, 7 and 14 min after start of pre-oxygenation with 60%, 80% or 100% oxygen concentration. The differences in the area of atelectasis formation between awake and 7 min and between 7 and 14 min were significant, irrespective of oxygen concentration (P<0.05). During the late time course, studied after pre-oxygenation with 80% oxygen, the differences in the area of atelectasis formation between awake and 14 min, between 14 and 21 min, between 21 and 28 min and finally between 21 and 45 min were all significant (P<0.05).

    Conclusion:

    Formation of atelectasis after pre-oxygenation and induction of anaesthesia is oxygen and time dependent. The benefit of using 80% oxygen during induction of anaesthesia in order to reduce atelectasis diminished gradually with time.

  • 4.
    Edmark, Lennart
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Auner, Udo
    Hallén, Jan
    Lassinantti-Olowsson, Lena
    Hedenstierna, Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Enlund, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Clinical Research, County of Västmanland.
    A ventilation strategy during general anaesthesia to reduce postoperative atelectasis2014In: Upsala Journal of Medical Sciences, ISSN 0300-9734, E-ISSN 2000-1967, Vol. 119, no 3, p. 242-250Article in journal (Refereed)
    Abstract [en]

    Background:

    Atelectasis is common during and after general anaesthesia. We hypothesized that a ventilation strategy, without recruitment manoeuvres, using a combination of continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) and a reduced end-expiratory oxygen fraction (FETO2) before ending mask ventilation with CPAP after extubation would reduce the area of postoperative atelectasis.

    Methods:

    Thirty patients were randomized into three groups. During induction and emergence, inspiratory oxygen fractions (FIO2) were 1.0 in the control group and 1.0 or 0.8 in the intervention groups. No CPAP/PEEP was used in the control group, whereas CPAP/PEEP of 6 cmH2O was used in the intervention groups. After extubation, FIO2 was set to 0.30 in the intervention groups and CPAP was applied, aiming at FETO2 < 0.30. Atelectasis was studied by computed tomography 25 min postoperatively.

    Results:

    The median area of atelectasis was 5.2 cm(2) (range 1.6-12.2 cm(2)) and 8.5 cm(2) (3-23.1 cm(2)) in the groups given FIO2 1.0 with or without CPAP/PEEP, respectively. After correction for body mass index the difference between medians (2.9 cm(2)) was statistically significant (confidence interval 0.2-7.6 cm(2), p = 0.04). In the group given FIO2 0.8, in which seven patients were ex- or current smokers, the median area of atelectasis was 8.2 cm(2) (1.8-14.7 cm(2)).

    Conclusion:

    Compared with conventional ventilation, after correction for obesity, this ventilation strategy reduced the area of postoperative atelectasis in one of the intervention groups but not in the other group, which included a higher proportion of smokers.

  • 5.
    Edmark, Lennart
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Clinical Research, County of Västmanland. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Auner, Udo
    Hallén, Jan
    Lassinantti-Olowsson, Lena
    Hedenstierna, Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Enlund, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Clinical Research, County of Västmanland.
    Reduction in postoperative atelectasis by continuous positive airway pressure and low oxygen concentration after endotracheal extubationManuscript (preprint) (Other academic)
    Abstract [en]

    Background. Atelectasis is common during and after general anaesthesia. We hypothesized that a ventilation strategy using a combination of 1) continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) and 2) a reduced end-expiratory oxygen fraction (FETO2) before commencing mask ventilation with CPAP after extubation would reduce the area of postoperative atelectasis.

    Methods. Thirty patients were randomized into three groups. During induction and emergence, inspiratory oxygen fractions (FIO2) were 1.0 in the control group and 1.0 or 0.8 in the intervention groups. No CPAP/PEEP was used in the control group, whereas CPAP/PEEP of 6 cmH2O was used in the intervention groups. After extubation, FIO2 was set to 0.30 in the intervention groups and CPAP was applied via a facemask, aiming at a FETO2 < 0.30. Atelectasis was studied by computed tomography 25 min postoperatively.

    Results. The median area of atelectasis was 5.2 cm2 (range 1.6–12.2 cm2) and 8.5 cm2 (3–23.1 cm2) in the groups given FIO2 1.0 with or without CPAP/PEEP, respectively. In the group given FIO2 0.8, in which 7 patients were ex- or current smokers, the median area of atelectasis was 8.2 cm2 (1.8–14.7 cm2). After correction for body mass index and age, the difference between the two groups given FIO2 1.0 was statistically significant (P = 0.016).

    Conclusion. Compared with conventional ventilation, this ventilation strategy reduced the area of postoperative atelectasis in one of the intervention groups but not in the other group, which included a higher proportion of smokers.

  • 6.
    Edmark, Lennart
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Clinical Research, County of Västmanland. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Auner, Udo
    Lindbäck, Johan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, UCR-Uppsala Clinical Research Center.
    Enlund, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Clinical Research, County of Västmanland. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
    Hedenstierna, Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Atelectasis after anaesthesia: a randomised trial of positive airway pressure and low oxygen2013Article in journal (Other academic)
    Abstract [en]

    Background:

    Atelectasis is common during and after general anaesthesia. We hypothesized that a ventilation strategy with a combination of 1) continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) and 2) a reduced end-expiratory oxygen fraction (FETO2) before extubation would reduce postoperative atelectasis.

    Methods:

    Sixty patients were randomized into two groups. During anaesthesia induction, inspiratory oxygen fractions (FIO2) were 1.0, and depending on weight, CPAP 6–8 cm H2O was applied in both groups via face mask. During maintenance of anaesthesia, a laryngeal mask airway was used, and depending on weight, PEEP was 6–8 cm H2O in both groups. Before extubation, FIO2 was set to 0.3 in the intervention groups and 1.0 in the control group. Atelectasis was studied by computed tomography approximately 13 min postoperatively.

    Results:

    The area of atelectasis was 5.5, 0–16.9 cm2 (median and range), and 6.8, 0–27.5 cm2 in the groups given FIO2 0.3 or FIO2 1.0 before extubation, a difference that was not statistically significant.

    Conclusion:

    Inducing anaesthesia with CPAP/PEEP and FIO2 1.0 and deliberately reducing FIO2 before extubation did not reduce postoperative atelectasis compared with FIO2 1.0 before extubation.

  • 7.
    Edmark, Lennart
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Disciplinary Domain of Medicine and Pharmacy, research centers etc., Centre for Clinical Research, County of Västmanland. Vastmanland Hosp Koping, Dept Anaesthes & Intens Care, Koping, Sweden..
    Englund, Emma-Karin
    Vastmanland Hosp Koping, Dept Anaesthes & Intens Care, Koping, Sweden..
    Jonsson, Alexandra Schottle
    Vastmanland Hosp Koping, Dept Anaesthes & Intens Care, Koping, Sweden..
    Zilic, Almira Teskeredzic
    Vastmanland Hosp Koping, Dept Anaesthes & Intens Care, Koping, Sweden..
    Cajander, Per
    Örebro Univ, Örebro Univ Hosp, Sch Med Sci, Dept Anaesthes & Intens Care, Örebro, Sweden..
    Östberg, Erland
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Disciplinary Domain of Medicine and Pharmacy, research centers etc., Centre for Clinical Research, County of Västmanland. Vastmanland Hosp Koping, Dept Anaesthes & Intens Care, Koping, Sweden.;Reg Vastmanland Uppsala Univ, Vastmanland Hosp Västerås, Ctr Clin Res, Västerås, Sweden..
    Pressure-controlled versus manual facemask ventilation for anaesthetic induction in adults: A randomised controlled non-inferiority trial2023In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 67, no 10, p. 1356-1362Article in journal (Refereed)
    Abstract [en]

    Background: Pressure-controlled face mask ventilation (PC-FMV) with positive end-expiratory pressure (PEEP) after apnoea following induction of general anaesthesia prolongs safe apnoea time and reduces atelectasis formation. However, depending on the set inspiratory pressure, a delayed confirmation of a patent airway might occur. We hypothesised that by lowering the peak inspiratory pressure (PIP) when using PC-FMV with PEEP, confirmation of a patent airway would not be delayed as studied by the first return of CO2, compared with manual face mask ventilation (Manual FMV).

    Methods: This was a single-centre, randomised controlled non-inferiority trial. Seventy adult patients scheduled for elective day-case surgery under general anaesthesia with body mass index between 18.5 and 29.9 kg m(-2), American Society of Anesthesiologists (ASA) classes I-III, and without anticipated difficult FMV, were included. Before the start of pre-oxygenation and induction of general anaesthesia, participants were randomly allocated to receive ventilation with either PC-FMV with PEEP, at a PIP of 11 and a PEEP of 6 cmH(2)O or Manual FMV, with the adjustable pressure-limiting valve set at 11 cmH(2)O. The primary outcome variable was the number of ventilatory attempts needed until confirmation of a patent airway, defined as the return of at least 1.3 kPa CO2.

    Results: The return of >= 1.3 kPa CO2 on the capnography curve was observed after mean +/- SD, 3.6 +/- 4.2 and 2.5 +/- 1.9 ventilatory attempts/breaths with PC-FMV with PEEP and Manual FMV, respectively. The difference in means (1.1 ventilatory attempts/breaths) had a 99% CI of similar to 1.0 to 3.1, within the accepted upper margin of four breaths for non-inferiority.

    Conclusion: Following induction of general anaesthesia, PC-FMV with PEEP was used without delaying a patent airway as confirmed with capnography, if moderate pressures were used.

  • 8.
    Edmark, Lennart
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Kostova-Aherdan, Kamelia
    Enlund, Mats
    Department of Anesthesiology and Intensive Care, Central Hospital, Västerås, Sweden.
    Hedenstierna, Göran
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Optimal Oxygen Concentration during Induction of General Anesthesia2003In: Anesthesiology, ISSN 0003-3022, E-ISSN 1528-1175, Vol. 98, no 1, p. 28-33Article in journal (Other academic)
    Abstract [en]

    BACKGROUND:

    The use of 100% oxygen during induction of anesthesia may produce atelectasis. The authors investigated how different oxygen concentrations affect the formation of atelectasis and the fall in arterial oxygen saturation during apnea.

    METHODS:

    Thirty-six healthy, nonsmoking women were randomized to breathe 100, 80, or 60% oxygen for 5 min during the induction of general anesthesia. Ventilation was then withheld until the oxygen saturation, assessed by pulse oximetry, decreased to 90%. Atelectasis formation was studied with computed tomography.

    RESULTS:

    Atelectasis in a transverse scan near the diaphragm after induction of anesthesia and apnea was 9.8 +/- 5.2 cm2 (5.6 +/- 3.4% of the total lung area; mean +/- SD), 1.3 +/- 1.2 cm2 (0.6 +/- 0.7%), and 0.3 +/- 0.3 cm2 (0.2 +/- 0.2%) in the groups breathing 100, 80, and 60% oxygen, respectively (P < 0.01). The corresponding times to reach 90% oxygen saturation were 411 +/- 84, 303 +/- 59, and 213 +/- 69 s, respectively (P < 0.01).

    CONCLUSION:

    During routine induction of general anesthesia, 80% oxygen for oxygenation caused minimal atelectasis, but the time margin before unacceptable desaturation occurred was significantly shortened compared with 100% oxygen.

  • 9.
    Hedenstierna, Göran
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Edmark, Lennart
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Does high oxygen concentration reduce postoperative infection?2014In: Anesthesiology, ISSN 0003-3022, E-ISSN 1528-1175, Vol. 120, no 4, p. 1050-1050Article in journal (Refereed)
  • 10.
    Hedenstierna, Göran
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Edmark, Lennart
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    In reply to: Calculating Ideal Body Weight: Keep It Simple Reply2017In: Anesthesiology, ISSN 0003-3022, E-ISSN 1528-1175, Vol. 127, no 1, p. 204-204Article in journal (Other academic)
  • 11.
    Hedenstierna, Göran
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Edmark, Lennart
    Mechanisms of atelectasis in the perioperative period2010In: Best Practice & Research: Clinical Anaesthesiology, ISSN 1521-6896, E-ISSN 1532-169X, Vol. 24, no 2, p. 157-169Article in journal (Refereed)
    Abstract [en]

    Atelectasis appears in about 90% of all patients who are anaesthetised. Up to 15–20% ofthe lung is regularly collapsed at its base during uneventful anaesthesia prior to any surgery being carried out. Atelectasis can persist for several days inthe postoperative period. It is likely to be a focus of infection and may contribute to pulmonary complications. A major cause of anaesthesia-induced lung collapse is the use of high oxygen concentration during induction and maintenance of anaesthesia together with the use of anaesthetics that cause loss of muscle tone and fall in functional residual capacity (a common action of almost all anaesthetics). This causes absorption atelectasis behind closed airways. Compression of lung tissue and loss of surfactant or surfactant function are additional potential causes ofatelectasis. Ventilation ofthe lungs with pure oxygen after a vital capacity manoeuvre that had re-opened a previously collapsed lung tissue results in rapid reappearance ofatelectasis. If 40% O2in nitrogen is used for ventilation ofthe lungs, atelectasis reappears slowly. A post-oxygenation manoeuvre is regularly performed to reduce the risk of hypoxaemia during awakening. However, a combination of oxygenation and airway suctioning will most likely cause new atelectasis. Recruitment at the end ofthe anaesthesia followed by ventilation with 100% O2 causes new atelectasis before anaesthesia is terminated but not with ventilation with lower fraction of inspired oxygen (FIO2). Thus, recruitment must be followed by ventilation with moderate FIO2.

  • 12.
    Hedenstierna, Göran
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
    Edmark, Lennart
    Vasteras Hosp, Dept Anesthesia & Intens Care, Vasteras, Sweden..
    Protective Ventilation during Anesthesia Is It Meaningful?2016In: Anesthesiology, ISSN 0003-3022, E-ISSN 1528-1175, Vol. 125, no 6, p. 1079-1082Article in journal (Refereed)
  • 13.
    Larsson, Alexander
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Disciplinary Domain of Medicine and Pharmacy, research centers etc., Centre for Clinical Research, County of Västmanland.
    Östberg, Erland
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Disciplinary Domain of Medicine and Pharmacy, research centers etc., Centre for Clinical Research, County of Västmanland.
    Edmark, Lennart
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Disciplinary Domain of Medicine and Pharmacy, research centers etc., Centre for Clinical Research, County of Västmanland.
    Arterial partial pressure of oxygen as a marker of airway closure does not correlate with the efficacy of pre-oxygenation: A prospective cohort study2023In: European Journal of Anaesthesiology, ISSN 0265-0215, E-ISSN 1365-2346, Vol. 40, no 9, p. 699-706Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The prerequisites for the early formation of anaesthesia-related atelectasis are pre-oxygenation with its resulting high alveolar oxygen content, and airway closure. Airway closure increases with age, so it seems counterintuitive that atelectasis formation during anaesthesia does not. One proposed explanation is that pre-oxygenation is impaired in the elderly by airway closure present in the waking state. The extent of airway closure cannot be assessed at the bedside, but arterial partial pressure of oxygen (PaO2) as a surrogate variable of the resulting ventilation to perfusion mismatch can.

    OBJECTIVE: The primary aim was to test the hypothesis that a decreased efficacy of pre-oxygenation, measured as the fraction of end-tidal oxygen (FE'O2) after 3 min of pre-oxygenation, correlates with decreased PaO2 on room air. We also re-investigated the influence on FE'O2 by age.

    DESIGN: Prospective observational study.

    SETTING: Two regional hospitals, Vasteras and Koping County Hospitals, Vastmanland, Sweden, between 30 October 2018 and 17 September 2021.PARTICIPANTSWe included 120 adults aged 40 to 79 years presenting for elective noncardiac surgery.

    INTERVENTION: An arterial blood gas was sampled before commencing pre-oxygenation.

    RESULTS: No linear correlation was found between FE'O2 at 3 min and PaO2 or age (Pearson's r = -0.038, P = 0.684; and Pearson's r = -0.113, P = 0.223, respectively). The mean & PLUSMN; SD FE'O2 at 3 min for the population studied was 0.87 & PLUSMN; 0.05.

    CONCLUSION: The lack of correlation between FE'O2 at 3 min and PaO2 or age during pre-oxygenation has implications for further studies concerning the interaction between airway closure and atelectasis. After 3 min of pre-oxygenation, FE'O2, even in the elderly, indicated a high enough alveolar oxygen concentration to promote atelectasis after induction, therefore, it is still unclear why atelectasis formation diminishes after middle age.

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