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Atelectasis

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Goran Hedenstierna – One of the best experts on this subject based on the ideXlab platform.

  • higher age and obesity limit Atelectasis formation during anaesthesia an analysis of computed tomography data in 243 subjects
    BJA: British Journal of Anaesthesia, 2020
    Co-Authors: Goran Hedenstierna, Hans Ulrich Rothen, Leif Tokics, Henrik Reinius, Erland Ostberg, John Ohrvik

    Abstract:

    Abstract Background General anaesthesia is increasingly common in elderly and obese patients. Greater age and body mass index (BMI) worsen gas exchange. We assessed whether this is related to increasing Atelectasis during general anaesthesia. Methods This primary analysis included pooled data from previously published studies of 243 subjects aged 18–78 yr, with BMI of 18–52 kg m−2. The subjects had no clinical signs of cardiopulmonary disease, and they underwent computed tomography (CT) awake and during anaesthesia before surgery after preoxygenation with an inspired oxygen fraction (FIO2) of >0.8, followed by mechanical ventilation with FIO2 of 0.3 or higher with no PEEP. Atelectasis was assessed by CT. Results Atelectasis area of up to 39 cm2 in a transverse scan near the diaphragm was seen in 90% of the subjects during anaesthesia. The log of Atelectasis area was related to a quadratic function of (age+age2) with the most Atelectasis at ∼50 yr (r2=0.08; P Conclusions Atelectasis during general anaesthesia increased with age up to 50 yr and decreased beyond that. Atelectasis increased with BMI in normal and overweight patients, but showed no further increase in obese subjects (BMI ≥30 kg m−2). Therefore, greater age and obesity appear to limit Atelectasis formation during general anaesthesia.

  • oxygen concentration and characteristics of progressive Atelectasis formation during anaesthesia
    Acta Anaesthesiologica Scandinavica, 2011
    Co-Authors: Lennart Edmark, Erland Ostberg, Udo Auner, Mats Enlund, Goran Hedenstierna

    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.

  • mechanisms of Atelectasis in the perioperative period
    Best Practice & Research Clinical Anaesthesiology, 2010
    Co-Authors: Goran Hedenstierna, Lennart Edmark

    Abstract:

    Atelectasis appears in about 90% of all patients who are anaesthetised. Up to 15–20% of the lung is regularly collapsed at its base during uneventful anaesthesia prior to any surgery being carried out. Atelectasis can persist for several days in the 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 of Atelectasis. Ventilation of the lungs with pure oxygen after a vital capacity manoeuvre that had re-opened a previously collapsed lung tissue results in rapid reappearance of Atelectasis. If 40% O 2 in nitrogen is used for ventilation of the 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 of the anaesthesia followed by ventilation with 100% O 2 causes new Atelectasis before anaesthesia is terminated but not with ventilation with lower fraction of inspired oxygen (FIO 2 ). Thus, recruitment must be followed by ventilation with moderate FIO 2 .

Lennart Edmark – One of the best experts on this subject based on the ideXlab platform.

  • oxygen concentration and characteristics of progressive Atelectasis formation during anaesthesia
    Acta Anaesthesiologica Scandinavica, 2011
    Co-Authors: Lennart Edmark, Erland Ostberg, Udo Auner, Mats Enlund, Goran Hedenstierna

    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.

  • mechanisms of Atelectasis in the perioperative period
    Best Practice & Research Clinical Anaesthesiology, 2010
    Co-Authors: Goran Hedenstierna, Lennart Edmark

    Abstract:

    Atelectasis appears in about 90% of all patients who are anaesthetised. Up to 15–20% of the lung is regularly collapsed at its base during uneventful anaesthesia prior to any surgery being carried out. Atelectasis can persist for several days in the 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 of Atelectasis. Ventilation of the lungs with pure oxygen after a vital capacity manoeuvre that had re-opened a previously collapsed lung tissue results in rapid reappearance of Atelectasis. If 40% O 2 in nitrogen is used for ventilation of the 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 of the anaesthesia followed by ventilation with 100% O 2 causes new Atelectasis before anaesthesia is terminated but not with ventilation with lower fraction of inspired oxygen (FIO 2 ). Thus, recruitment must be followed by ventilation with moderate FIO 2 .

Hans Ulrich Rothen – One of the best experts on this subject based on the ideXlab platform.

  • higher age and obesity limit Atelectasis formation during anaesthesia an analysis of computed tomography data in 243 subjects
    BJA: British Journal of Anaesthesia, 2020
    Co-Authors: Goran Hedenstierna, Hans Ulrich Rothen, Leif Tokics, Henrik Reinius, Erland Ostberg, John Ohrvik

    Abstract:

    Abstract Background General anaesthesia is increasingly common in elderly and obese patients. Greater age and body mass index (BMI) worsen gas exchange. We assessed whether this is related to increasing Atelectasis during general anaesthesia. Methods This primary analysis included pooled data from previously published studies of 243 subjects aged 18–78 yr, with BMI of 18–52 kg m−2. The subjects had no clinical signs of cardiopulmonary disease, and they underwent computed tomography (CT) awake and during anaesthesia before surgery after preoxygenation with an inspired oxygen fraction (FIO2) of >0.8, followed by mechanical ventilation with FIO2 of 0.3 or higher with no PEEP. Atelectasis was assessed by CT. Results Atelectasis area of up to 39 cm2 in a transverse scan near the diaphragm was seen in 90% of the subjects during anaesthesia. The log of Atelectasis area was related to a quadratic function of (age+age2) with the most Atelectasis at ∼50 yr (r2=0.08; P Conclusions Atelectasis during general anaesthesia increased with age up to 50 yr and decreased beyond that. Atelectasis increased with BMI in normal and overweight patients, but showed no further increase in obese subjects (BMI ≥30 kg m−2). Therefore, greater age and obesity appear to limit Atelectasis formation during general anaesthesia.

  • Atelectasis Formation During Anesthesia: Causes and Measures to Prevent It
    Journal of Clinical Monitoring and Computing, 2000
    Co-Authors: Goran Hedenstierna, Hans Ulrich Rothen

    Abstract:

    Pulmonary gas exchange is regularly impaired during general anaesthesia with mechanical ventilation. This results in decreased oxygenation of blood. A major cause is collapse of lung tissue (Atelectasis), which can be demonstrated by computed tomography but not by conventional chest x-ray. Collapsed lung tissue is present in 90% of all subjects, both during spontaneous breathing and after muscle paralysis, and whether intravenous or inhalational anaesthetics are used. There is a correlation between the amount of Atelectasis and pulmonary shunt. Shunt does not increase with age. In obese patients, larger atelectatic areas are present than in lean ones. Finally, patients with chronic obstructive lung disease may show less or even no Atelectasis. There are different procedures that can be used in order to prevent Atelectasis or to reopen collapsed lung tissue. The application of positive end-expiratory pressure (PEEP) has been tested in several studies. On the average, arterial oxygenation does not improve markedly, and Atelectasis may persist. Further, reopened lung units re-collapse rapidly after discontinuation of PEEP. Inflation of the lungs to an airway pressure of 40 cm H_2O, maintained for 7–8 seconds (recruitment or “vital capacity” manoeuvre), re-expands all previously collapsed lung tissue. During induction of anaesthesia, the use of a gas mixture, that includes a poorly absorbed gas such as nitrogen, may prevent the early formation of Atelectasis. During ongoing anaesthesia, pulmonary collapse reappears slowly if a low fraction of oxygen in nitrogen is used for the ventilation of the lungs after a previous VC-manoeuvre. On the other hand, ventilation of the lungs with pure oxygen results in a rapid reappearance of Atelectasis. Thus, ventilation during anaesthesia should be done if possible with a moderate fraction of inspired oxygen (FIO_2, e.g. 0.3–0.4). Alternatively, if the lungs are ventilated with a high inspiratory fraction of oxygen, the use of PEEP may be considered. In summary, Atelectasis is present in most humans during anaesthesia and is a major cause of impaired oxygenation. Avoiding high fractions of oxygen in inspired gas during induction and maintenance of anaesthesia may prevent formation of Atelectasis. Finally, intermittent “vital capacity”-manoeuvres together with PEEP reduces the amount of Atelectasis and pulmonary shunt.

  • Atelectasis Formation During Anesthesia: Causes and Measures to Prevent It
    Journal of Clinical Monitoring and Computing, 2000
    Co-Authors: Goran Hedenstierna, Hans Ulrich Rothen

    Abstract:

    Pulmonary gas exchange is regularly impaired during general anaesthesia with mechanical ventilation. This results in decreased oxygenation of blood. A major cause is collapse of lung tissue (Atelectasis), which can be demonstrated by computed tomography but not by conventional chest x-ray. Collapsed lung tissue is present in 90% of all subjects, both during spontaneous breathing and after muscle paralysis, and whether intravenous or inhalational anaesthetics are used. There is a correlation between the amount of Atelectasis and pulmonary shunt. Shunt does not increase with age. In obese patients, larger atelectatic areas are present than in lean ones. Finally, patients with chronic obstructive lung disease may show less or even no Atelectasis. There are different procedures that can be used in order to prevent Atelectasis or to reopen collapsed lung tissue. The application of positive end-expiratory pressure (PEEP) has been tested in several studies. On the average, arterial oxygenation does not improve markedly, and Atelectasis may persist. Further, reopened lung units re-collapse rapidly after discontinuation of PEEP. Inflation of the lungs to an airway pressure of 40 cm H_2O, maintained for 7–8 seconds (recruitment or “vital capacity” manoeuvre), re-expands all previously collapsed lung tissue. During induction of anaesthesia, the use of a gas mixture, that includes a poorly absorbed gas such as nitrogen, may prevent the early formation of Atelectasis. During ongoing anaesthesia, pulmonary collapse reappears slowly if a low fraction of oxygen in nitrogen is used for the ventilation of the lungs after a previous VC-manoeuvre. On the other hand, ventilation of the lungs with pure oxygen results in a rapid reappearance of Atelectasis. Thus, ventilation during anaesthesia should be done if possible with a moderate fraction of inspired oxygen (FIO_2, e.g. 0.3–0.4). Alternatively, if the lungs are ventilated with a high inspiratory fraction of oxygen, the use of PEEP may be considered. In summary, Atelectasis is present in most humans during anaesthesia and is a major cause of impaired oxygenation. Avoiding high fractions of oxygen in inspired gas during induction and maintenance of anaesthesia may prevent formation of Atelectasis. Finally, intermittent “vital capacity”-manoeuvres together with PEEP reduces the amount of Atelectasis and pulmonary shunt.