| 1. |
- Edmark, Lennart, 1954-, et al.
(author)
-
Optimal Oxygen Concentration during Induction of General Anesthesia
- 2003
-
In: Anesthesiology. - 0003-3022 .- 1528-1175. ; 98:1, s. 28-33
-
Journal article (other academic/artistic)abstract
- 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.
|
|
| 2. |
- Edmark, Lennart, 1954-, et al.
(author)
-
Oxygen concentration and characteristics of progressive atelectasis formation during anaesthesia
- 2011
-
In: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 55:1, s. 75-81
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 3. |
- Edmark, Lennart, 1954-, et al.
(author)
-
Pressure-controlled versus manual facemask ventilation for anaesthetic induction in adults : A randomised controlled non-inferiority trial
- 2023
-
In: Acta Anaesthesiologica Scandinavica. - : John Wiley & Sons. - 0001-5172 .- 1399-6576. ; 67:10, s. 1356-1362
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 4. |
- Edmark, Lennart, 1954-
(author)
-
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 Adults
- 2013
-
Doctoral thesis (other academic/artistic)abstract
- 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.
|
|
| 5. |
- Edmark, Lennart, 1954-, et al.
(author)
-
Reduction in postoperative atelectasis by continuous positive airway pressure and low oxygen concentration after endotracheal extubation
-
Other publication (other academic/artistic)abstract
- 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. |
|
|
| 7. |
- Larsson, Alexander, et al.
(author)
-
Arterial partial pressure of oxygen as a marker of airway closure does not correlate with the efficacy of pre-oxygenation : A prospective cohort study
- 2023
-
In: European Journal of Anaesthesiology. - : Ovid Technologies (Wolters Kluwer Health). - 0265-0215 .- 1365-2346. ; 40:9, s. 699-706
-
Journal article (peer-reviewed)abstract
- 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.
|
|
