Airway Closure, Gas Trapping, and the Functional Residual Capacity during Anesthesia

Don, H. F.; Wahba, W. M.; Craig, Douglas B.

doi:10.1097/00000542-197206000-00003

Cited by 122 publications

(36 citation statements)

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“…This corroborates findings in spontaneously breathing adults showing that the changes of functional residual capacity develop a short time after induction of anaesthesia and stabilise thereafter [32]. The changes of functional residual capacity and ventilation distribution observed in this study after caudal block with bupivacaine are therefore related to this intervention and not to time.…”

Section: Discussionsupporting

confidence: 92%

The effect of caudal block on functional residual capacity and ventilation homogeneity in healthy children*

Ungern‐Sternberg¹,

Regli²,

Frei³

et al. 2006

Anaesthesia

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SummaryCaudal block results in a motor blockade that can reduce abdominal wall tension. This could interact with the balance between chest wall and lung recoil pressure and tension of the diaphragm, which determines the static resting volume of the lung. On this rationale, we hypothesised that caudal block causes an increase in functional residual capacity and ventilation distribution in anaesthetised children. Fifty-two healthy children (15-30 kg, 3-8 years of age) undergoing elective surgery with general anaesthesia and caudal block were studied and randomly allocated to two groups: caudal block or control. Following induction of anaesthesia, the first measurement was obtained in the supine position (baseline). All children were then turned to the left lateral position and patients in the caudal block group received a caudal block with bupivacaine. No intervention took place in the control group. After 15 min in the supine position, the second assessment was performed. Functional residual capacity and parameters of ventilation distribution were calculated by a blinded reviewer. Functional residual capacity was similar at baseline in both groups. In the caudal block group, the capacity increased significantly (p < 0.0001) following caudal block, while in the control group, it remained unchanged. In both groups, parameters of ventilation distribution were consistent with the changes in functional residual capacity. Caudal block resulted in a significant increase in functional residual capacity and improvement in ventilation homogeneity in comparison with the control group. This indicates that caudal block might have a beneficial effect on gas exchange in anaesthetised, spontaneously breathing preschool-aged children with healthy lungs. Various anaesthetic agents, airway instrumentations and ventilation strategies are used in infants and children undergoing anaesthesia. Each of these factors may affect functional residual capacity (FRC), which is one of the most important respiratory parameters of gas exchange. There is very little information available on the magnitude and the relative contribution of these different factors (e.g. neuroaxial blockade with local anaesthetics) on functional residual capacity in anaesthetised children [1][2][3][4].Muscle relaxation induced by caudal epidural anaesthesia with bupivacaine decreases abdominal muscle tone while sparing the muscles of the respiratory system (diaphragm, intercostal muscles). This could interact with the balance between chest wall and lung recoil pressure and tension of the diaphragm, which determines the static resting volume of the lung. This alteration of the equilibrium between the thoracal and abdominal compartments might affect the functional residual capacity and ventilation homogeneity of the lungs. This study

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Section: Discussionsupporting

confidence: 92%

The effect of caudal block on functional residual capacity and ventilation homogeneity in healthy children*

Ungern‐Sternberg¹,

Regli²,

Frei³

et al. 2006

Anaesthesia

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“…In COPD, TODD et al [33] EELV and FRC measurements with helium dilution may be affected by airway closure, which may interfere with correct mixing of helium between the anaesthesia bag and lung [26]. The current authors employed high VTs (1.0-1.5 L), which resulted in PL .20 cmH 2 O and probable re-opening of closed airways [26,34,35]. Low respiratory rates were also used, which resulted in a prolonged expiratory time of ,12 s, in order to augment expiratory helium mixing between anaesthesia bag and lung and minimise helium trapping.…”

Section: Prone Position and Airway Resistance In Copd Sd Mentzelopomentioning

confidence: 96%

Prone position improves expiratory airway mechanics in severe chronic bronchitis

Mentzelopoulos¹

2005

European Respiratory Journal

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Based on lung parenchyma-airways' interdependence, the present authors hypothesised that prone positioning may reduce airway resistance in severe chronic bronchitis.A total of 10 anaesthetised/mechanically ventilated patients were enrolled. Partitioned respiratory system (RS) mechanics during iso-flow experiments (flow50.91 L?s In severe chronic bronchitis, prone positioning reduces airway resistance and dynamic hyperinflation.

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“…However, FRC and LCI have been shown to remain constant in preschool children under propofol anesthesia (F i O 2 = 0.5) during a study period of similar duration [43]. Additionally, FRC decreases immediately after induction of anesthesia in adults but then remains stable for at least 1 h [41]. Therefore, in the present study a time effect was unlikely to have been a confounding factor for the observed changes in FRC, LCI, and MDN.…”

Section: Discussionmentioning

confidence: 45%

“…Most anesthetic agents promote atelectasis formation shortly after induction, leading to a decrease in FRC and ventilation homogeneity and potentially to hypoxemia [39][40][41][42]. Therefore, prevention of atelectasis during anesthesia or sedation is important in all children as atelectasis persists well into the postinterventional period and can have a negative impact on patient recovery [42].…”

Section: Discussionmentioning

confidence: 99%

Prone equals prone? Impact of positioning techniques on respiratory function in anesthetized and paralyzed healthy children

et al. 2007

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Objectives: Although the prone position is effectively used to improve oxygenation, its impact on functional residual capacity is controversial. Different techniques of body positioning might be an important confounding factor. The aim of this study was to determine the impact of two different prone positioning techniques on functional residual capacity and ventilation distribution in anesthetized, preschool-aged children. Design: Functional residual capacity and lung clearance index, a measure of ventilation homogeneity, were calculated using a sulfur-hexafluoride multibreath washout technique. After intubation, measurements were taken in the supine position and, in random order, in the flat prone position and the augmented prone position (gel pads supporting the pelvis and the upper thorax). Setting: Pediatric anesthesia unit of university hospital. Patients and participants: Thirty preschool children without cardiopulmonary disease undergoing elective surgery. Measurements and results: Mean (range) age was 48.5 (24-80) months, weight 17.2 (10.5-26.9) kg, functional residual capacity (mean ± SD) 22.9 ± 6.2 ml.kg -1 in the supine position and 23.3 ± 5.6 ml.kg -1 in the flat prone position, while lung clearance indices were 8.1 ± 2.3 vs. 7.9 ± 2.3, respectively. In contrast, functional residual capacity increased to 27.6 ± 6.5 ml.kg -1 (p< 0.001) in the augmented prone position while at the same time the lung clearance index decreased to 6.7 ± 0.9 (p< 0.001). Conclusions: Functional residual capacity and ventilation distribution were similar in the supine and flat prone positions, while these parameters improved significantly in the augmented prone position, suggesting that the technique of prone positioning has major implications for pulmonary function.

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Airway Closure, Gas Trapping, and the Functional Residual Capacity during Anesthesia

Cited by 122 publications

References 0 publications

The effect of caudal block on functional residual capacity and ventilation homogeneity in healthy children*

The effect of caudal block on functional residual capacity and ventilation homogeneity in healthy children*

Prone position improves expiratory airway mechanics in severe chronic bronchitis

Prone equals prone? Impact of positioning techniques on respiratory function in anesthetized and paralyzed healthy children

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