Anesth Analg 1999;88:268
© 1999 International Anesthesia Research Society
PEDIATRIC ANESTHESIA
Endobronchial Intubation Causes an Immediate Increase in Peak Inflation Pressure in Pediatric Patients
Carlos Campos, MD,
Sameh S. Naguib, MD,
Alice Z. Chuang, PhD,
Noreen A. Lemak, MD, and
Samia N. Khalil, MD
Department of Anesthesiology, The University of Texas Medical School at Houston, Houston, Texas
Address correspondence and reprint requests to Samia N. Khalil, MD, 6431 Fannin, MSB 5.020, Houston, TX 77030. Address e-mail to skhalil{at}anes1.med.uth.tmc.edu
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Abstract
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Our purpose was to determine whether endobronchial intubation always causes an immediate increase in peak inflation pressure and, if so, the magnitude of the increase. Fourteen children scheduled for central line placement for prolonged antibiotic administration comprised the study group. After routine premedication and induction of anesthesia (halothane in oxygen), an endotracheal tube was inserted, and its position was verified by auscultation and fluoroscopy. Children were mechanically ventilated using a preset volume pressure-limited ventilator with a 5-L fresh gas flow. All children received a constant tidal volume using a similar circuit, similar tubing, and a similar compression volume. The lowest peak inflation pressure to deliver a tidal volume of 15 mL/kg was used. After adjusting the respiratory rate (end-tidal CO2 30 mm Hg) and anesthetic level (halothane end-tidal 1.2%), the peak inflation pressure at this endotracheal position was re-corded. The endotracheal tube was advanced into a bronchus, the position was verified as above, and peak inflation pressure was recorded. The endobronchial tube was then pulled back into the trachea, and placement of the central line proceeded. The peak inflation pressure at the endobronchial position was significantly greater than the peak inflation pressure at the endotracheal position (P < 0.0001). The increase was instantaneous at the endobronchial position. Monitoring peak inflation pressure while inserting an endotracheal tube and during anesthesia can help to diagnose endobronchial intubation.
Implications: Monitoring peak inflation pressure while inserting an endotracheal tube and during anesthesia can help to diagnose endobronchial intubation.
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Introduction
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Life-threatening airway issues are common during pediatric surgery, and the incidence increases with duration of anesthesia (1). In one study of Ring, Adair, Elwyn (RAE) tubes in children, endobronchial intubation (EBI) was also a common event, and age recommendations on the side of the endotracheal tube can be misleading (2). Clinical examination to determine proper endotracheal tube tip placement may not be accurate, especially in newborns. The purpose of this study was to determine whether EBI always causes an increase in peak inflation pressure (PIP) and, if so, the magnitude of the increase.
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Methods
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After institutional approval, written, informed consent was obtained from the parents or guardians of children who were scheduled for central line placement for prolonged antibiotic treatment of osteomyelitis. Children with bleeding diathesis or advanced hepatic, renal, cardiac, or pulmonary disease were excluded. All children were fasted and premedicated with midazolam 0.50 mg/kg PO. Anesthesia induction consisted of halothane and oxygen administered via a mask with standard monitoring. After inserting an IV cannula, atropine 10 µg/kg IV, fentanyl 2 µg/kg IV, and vecuronium 0.1 mg/kg IV were administered.
An appropriately sized endotracheal tube was then inserted. Leak pressure around the endotracheal tube was recorded, and the tube's position was verified by auscultation and fluoroscopy. Children were mechanically ventilated using a volume-preset, time-cycled, pressure-limited ventilator with a 5-L fresh gas flow. All children received constant tidal volume using a similar circuit, similar tubing (Vital Signs, Totowa, NJ), and a similar compression volume.The lowest PIP to deliver a tidal volume of 15 mL/kg was used. The respiratory rate was adjusted to reach an end-tidal CO2 value of 30 mm Hg. The halothane level was adjusted to reach an end-tidal value of 1.2%. The PIP at the endotracheal position was then recorded. The endotracheal tube was advanced into a bronchus, and this position was verified by auscultation and fluoroscopy. The PIP at the endobronchial position was recorded. The endobronchial tube was then pulled back into the trachea, and placement of the central line proceeded.
Data were analyzed using paired t-tests to assess the change in PIP. P < 0.05 was considered to be significant.
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Results
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Fourteen ASA physical status II children were entered into the study. Age, weight, gender, endotracheal tube size, PIPs at the endotracheal and endobronchial positions, presence of a leak, and leak pressure are shown in Table 1.
The PIP (mean ± SD) was 23.6 ± 5.3 cm H2O at the endotracheal position and 31.4 ± 6.8 cm H2O at the endobronchial position. The PIP at the endobronchial position was significantly greater than the PIP at the endotracheal position (P < 0.0001). All children demonstrated an increase in PIP that was instantaneous at the endobronchial position. In all children, the advancement of the endotracheal tube into a bronchus resulted in a right EBI. No side effects were noted in our patients.
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Discussion
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Our study demonstrates that endotracheal intubation causes an instantaneous increase in PIP. The increase reflects the delivery of a relatively larger volume of gases to a smaller lung volume. In infants and young children, a minor change in the position of the head or the application of a tongue depressor may displace the endotracheal tube (3). The true situation may be overlooked because the clinical signs of an EBI may develop slowly and may be obscure or uncertain (4).
In a study of 196 children, 14 episodes of EBI occurred in 10 patients, and none of the episodes was recognized clinically. Clinical signs or symptoms occurred in only three of these episodes (4). Contrary to our findings, Rolf and Coté noted a change in PIP in only 3 of 10 children with EBI, and only after the patients developed desaturation. Their failure to detect EBI (either by an increase in PIP or a reduction in end-tidal CO2) in 13 of the 14 episodes was likely due to the fact that all of the EBIs occurred during manual ventilation (4).
The incidence of EBI in children has been reported in various studies as 1.2% (1), 20% (2), 5.1% (4), 50% (5), and 2.4% (6). It seems that the true incidence of accidental EBI in routine adult and pediatric anesthesia is not known (4).
In patients with severe trauma to the head, neck, or chest, ascertaining correct endotracheal tube position may present a major problem (7). Brunel et al. (8) confirmed the inaccuracy of physical examination to assess tube position. In 219 critically ill children and adults, 5% had mainstem intubations; 60% of these occurred despite equal breath sounds on examination. Other studies in children (1,4) have shown the fallibility of auscultation or assessment of chest expansion in determining tube position.
Expired CO2 monitoring by a capnograph provides an early warning of anesthetic mishaps (1). However, a study in children (4) comparing capnography with pulse oximetry showed that pulse oximetry provided the first diagnostic clue in 13 of 14 episodes of EBI; the one event diagnosed by capnography had concurrent oxygen desaturation.
In a 1997 publication from the Australian Incidence Monitoring Study (9), accidental bronchial intubation occurred in 154 of 3947 (3.7%) incidents, and capnography remained normal or unremarkable during 88.5% of the episodes. One third of the cases were associated with head or neck surgery and possible flexion of the patient's head. A RAE tube was used in 20% of the incidents, a frequency higher than that in the overall study.
RAE tubes are commonly used in children because it is presumed that they can be positioned more reliably than conventional endotracheal tubes. In a retrospective study of RAE tube use in 40 infants and children, there was a 32.5% incidence of intubation in which the tube was too long and a 20% incidence of EBI with no morbidity (2).
Under an adequate level of general anesthesia with mechanical ventilation, a sudden change in PIP can alert the anesthesiologist to a possible EBI. Other factors that can increase PIP, such as kinking of the endotracheal tube, a mucous plug, bronchospasm, pneumothorax, or light anesthesia, should be excluded.
Close monitoring of pulse oximetry, end-tidal CO2, and PIP can lead to a prompt recognition of accidental EBI. In our pediatric study population, monitoring PIP while placing the endotracheal tube and during anesthesia provided an instant warning of EBI in all cases.
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Footnotes
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AZC received partial support from a National Eye Institute vision core grant.
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References
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Coté CJ, Liu LMP, Szyfelbein SK, et al. Intraoperative events diagnosed by expired carbon dioxide monitoring in children. Anaesth Soc J 1986;33:315–20.
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Rolf N, Coté CJ. Diagnosis of clinically unrecognized endobronchial intubation in paediatric anaesthesia: which is more sensitive, pulse oximetry or capnography? Paediatr Anaesth 1992;2:31–5.
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Brunel W, Coleman DL, Schwartz DE, et al. Assessment of routine chest roentgenograms and the physical examination to confirm endotracheal tube position. Chest 1989;96:1043–5.[Abstract/Free Full Text]
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McCoy EP, Russell WJ, Webb RK. Accidental bronchial intubation: an analysis of AIMS incident reports from 1988 to 1994 inclusive. Anaesthesia 1997;52:24–31.[Web of Science][Medline]
Accepted for publication October 19, 1998.
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A. Mahajan, N. Hoftman, A. Hsu, R. Schroeder, and S. Wald
Continuous Monitoring of Dynamic Pulmonary Compliance Enables Detection of Endobronchial Intubation in Infants and Children
Anesth. Analg.,
July 1, 2007;
105(1):
51 - 56.
[Abstract]
[Full Text]
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Abstract
Introduction
