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Effect of common airway manoeuvres on upper airway dimensions and clinical signs in anaesthetized, spontaneously breathing children

2001; Elsevier BV; Volume: 86; Issue: 2 Linguagem: Inglês

10.1093/bja/86.2.217

1471-6771

A. Reber, Reto Paganoni, Franz J. Frei,

Tracheal and airway disorders

Chin lift, jaw thrust and these manoeuvres combined with continuous positive airway pressure (CPAP) can be used to improve the patency of the upper airway during general anaesthesia. We used video endoscopy and measurement of stridor to compare the efficacy of these manoeuvres in 24 children (3–10 yr) with adenotonsillar hyperplasia. A bronchofibrescope was passed via the nose while the children were breathing spontaneously, to identify (i) the shortest transverse distance between the tonsils during inspiration and during expiration and (ii) the distance from the tip of the epiglottis to the posterior pharyngeal wall. Chin lift or jaw thrust lifted the epiglottis and, when combined with CPAP (10 cm H2O), there was a significant lateral displacement of the tonsils. Both chin lift plus CPAP and jaw thrust plus CPAP reduced stridor significantly compared with the unsupported condition. In conclusion, in spontaneously breathing children with large tonsils, chin lift plus CPAP is recommended, whereas jaw thrust plus CPAP is no better and may cause post-operative discomfort. Chin lift, jaw thrust and these manoeuvres combined with continuous positive airway pressure (CPAP) can be used to improve the patency of the upper airway during general anaesthesia. We used video endoscopy and measurement of stridor to compare the efficacy of these manoeuvres in 24 children (3–10 yr) with adenotonsillar hyperplasia. A bronchofibrescope was passed via the nose while the children were breathing spontaneously, to identify (i) the shortest transverse distance between the tonsils during inspiration and during expiration and (ii) the distance from the tip of the epiglottis to the posterior pharyngeal wall. Chin lift or jaw thrust lifted the epiglottis and, when combined with CPAP (10 cm H2O), there was a significant lateral displacement of the tonsils. Both chin lift plus CPAP and jaw thrust plus CPAP reduced stridor significantly compared with the unsupported condition. In conclusion, in spontaneously breathing children with large tonsils, chin lift plus CPAP is recommended, whereas jaw thrust plus CPAP is no better and may cause post-operative discomfort. Maintenance of the airway is an important aspect of the safe administration of anaesthesia to children. Failure to maintain a patent airway can result in hypoxaemia despite an increase in inspired oxygen fraction. The airway obstruction associated with general anaesthesia is generally attributed to reduced genioglossus activity and consequent posterior displacement of the tongue.1Safar P Escarraga LA Chang F Upper airway obstruction in the unconscious patient.J Appl Physiol. 1959; 14: 760-764Crossref PubMed Scopus (223) Google Scholar 2Morikawa S Safar P DeCarlo J Influence of the head–jaw position upon airway patency.Anesthesiology. 1961; 22: 265-270Crossref PubMed Scopus (153) Google Scholar Any drug that reduces the activity of the pharyngeal muscles can reduce airway patency and thereby increase upper airway resistance.3Montravers P Dureuil B Desmondt JM Effects of i.v. midazolam on upper airway resistance.Br J Anaesth. 1991; 66: 157-162Crossref PubMed Scopus (196) Google Scholar Obstruction can be caused by occlusion of the oropharynx by the tongue4Fink BR Roentgenographic studies of the oropharyngeal airway.Anesthesiology. 1957; 18: 711-718Crossref PubMed Scopus (10) Google Scholar or by the epiglottis or soft palate.5Mathru M Esch O Lang J et al.Magnetic resonance imaging of the upper airway. Effects of propofol anesthesia and nasal continuous positive airway pressure in humans.Anesthesiology. 1996; 84: 273-279Crossref PubMed Scopus (150) Google Scholar Although the positions of the head and mandible affect upper airway obstruction, knowledge of the respiratory changes in airway dimensions is still only fragmentary in spontaneously breathing, anaesthetized infants and children. The chin lift manoeuvre is considered to produce a satisfactory upper airway in subjects with a flaccid upper airway.6Ruben HM Elam JO Ruben AM Greene DG Investigation of upper airway problems in resuscitation. 1. Studies of pharyngeal X-rays and performance by laymen.Anesthesiology. 1961; 22: 271-279Crossref PubMed Scopus (80) Google Scholar Airway patency is also improved by jaw thrust with continuous positive airway pressure (CPAP) to dilate or splint the upper airway, but little is known about how these techniques work. We studied airway patency using clinical signs and endoscopy to describe the effects of common airway manoeuvres on airway patency in children. We studied 24 children (3–10 yr) scheduled for elective adenotonsillectomy. Children with craniofacial abnormalities, deformities of the chest or spine, and myopathies were excluded. The study was approved by the Ethics Committee of the Children's Hospital, Basel, and parents gave written informed consent. Each patient was premedicated with midazolam 0.3 mg kg−1 rectally 15 min before anaesthesia. Anaesthesia was induced with ≤3 vol% halothane via a face mask, with oxygen in 50% nitrous oxide from a circle system. Inspired halothane concentration was adjusted to give an end-tidal concentration of 1.0 vol%. Electrocardiogram, pulse oximetry and capnography with breathing frequency were recorded (Capnomac Ultima; Datex, Helsinki, Finland). The head position was standardized. The head was slightly extended using a special pillow, to obtain an angle of 110° between the horizontal plane of the operating table and a line connecting the lateral corner of the eye and the tragus of the ear, with neither the occiput of the head nor the shoulders raised above the operating table. We used this angle because a study of adults by Boidin7Boidin MP Airway patency in the unconscious patient.Br J Anaesth. 1985; 57: 306-310Crossref PubMed Scopus (130) Google Scholar and our own clinical observations in anaesthetized children (unpublished) suggest that this allows maximal widening of the upper airways. We adapted a special airway endoscopy mask8Frei FJ Wengen DF Rutishauser M Ummenhofer W The airway endoscopy mask; useful device for fiberoptic evaluation and intubation of the pediatric airway.Paediatr Anaesth. 1995; 5: 319-324Crossref PubMed Scopus (48) Google Scholar and a standardized fixation system (Secutape; TechniMed Ltd, Basel, Switzerland) to tailor the mask to each patient. A bronchofibrescope with an outer diameter of 3.5 mm (Olympus Optical, Volketswil, Switzerland) was inserted through the mask and one nostril into the nasopharynx, leaving the other nostril patent. The tongue and laryngeal structures were examined while the child was breathing spontaneously. The light source for the endoscopy was a xenon lamp (CLV-U40, Olympus Optical Co., Tokyo, Japan). For all measurements, the tip of the fibrescope was kept at the edge of the soft palate to give comparable views at baseline (chin unsupported) and during the subsequent manoeuvres. The manoeuvres were standardized and performed by the same investigator in all children to eliminate inter-investigator variability. A baseline measurement was made with the adapted facemask with the patient's chin unsupported. Then chin lift was done with one hand without making the mandible protrude. The teeth were in light contact and the lips remained open, so the mouth was not completely closed. Then, in addition to chin lift, CPAP of 10 cm H2O was applied from the circle system to dilate or splint the upper airway. Jaw thrust was applied with both hands, displacing the jaw upwards and anteriorly (Esmarch manoeuvre), which allowed the mouth to remain open. This was done with maximal mandibular protrusion at zero end-expiratory airway pressure and then with CPAP of 10 cm H2O. After the measurements, the patient's trachea was intubated for subsequent surgery. Airway patency was assessed clinically as follows: stridor score 1, normal breathing sounds detected by auscultation over the trachea; 2, stridor over the trachea detected by stethoscope; 3, stridor detected without auscultation (audible); 4, no airway sound detectable over the trachea. Records were made for 1 min during each of the different airway manoeuvres on a Super VHS tape (SV-9500 MDP; Sony, Tokyo, Japan). The video sequences were transferred to a Macintosh computer using a frame grabber card (miroMotion DC 20; Miro Computer Products, Braunschweig, Germany). Video information (72 dots per inch, 25 frames per second) was transposed to a PICT format (Adobe Premiere 4.2.1; Adobe Systems Inc., San Jose, CA, USA) and analysed with an image analysis software package (Adobe Photoshop 4.0; Adobe Systems Inc.). The person who performed the image analysis was blinded as to a patient's group. The images with the most narrowed and widened airway dimensions (corresponding to end-inspiration and end-expiration) were identified for the different conditions. The shortest distance between the tonsils (transverse dimension) and the distance between the tip of the epiglottis and the posterior pharyngeal wall (anteroposterior dimension) were measured. These are the most important pharyngeal airway distances during breathing in anaesthetized children.9Reber A Paganoni R Frei FJ Dynamic imaging of the pediatric upper airway during general anesthesia.J Clin Monit. 1998; 14: 199-202Crossref Google Scholar Airway dimensions were expressed as a percentage of distance from baseline, with the chin unsupported. Percentages instead of absolute values were used to reduce the problems of different distance and characteristics between subjects and radial distortion of images caused by the optical characteristics of the fibrescope.10Forkert L Watanabe H Sutherland K Vincent S Fisher JT Quantitative videobronchoscopy: a new technique to assess airway calibre.Am J Respir Crit Care Med. 1996; 154: 1794-1803Crossref PubMed Scopus (37) Google Scholar The different conditions were compared by repeated-measures analysis of variance. For post hoc comparisons, Tukey's test was applied and probability values calculated. Score values were analysed by means of the non-parametric Friedman's test for repeated-measures analysis. Spearman's rank correlation coefficient (rs) was applied to analyse possible relationships between variables. A P value of <0.05 was considered significant. For all calculations, Statistica/w 4.5 software (StatSoft, Tulsa, OK, USA) was used. Patient characteristics are presented in Tables 1 and 2. There was no relationship between patient characteristics and subsequent findings.Table 1Patient characteristics. Data for age, weight and height are mean (sd) (range)Age (yr)5.8 (1.8) (3–10)Body weight (kg)19.6 (4.7) (12.5–25.8)Height (cm)112 (12) (90–126)History of snoring (n)18/24History of apnoea (n)8/24 Open table in a new tab Table 2Effect of airway manoeuvres on heart rate and breathing frequency. Data are mean (sd) (range). CPAP, continuous positive airway pressureBaselineChin liftChin lift + CPAPJaw thrustJaw thrust + CPAPHeart rate, beats min−194 (21) (58–150)92 (19) (62–146)91 (19) (63–146)99 (21) (61–146)98 (23) (64–157)Breathing frequency, bpm35 (7) (22–53)33 (7) (22–49)36 (8) (22–61)34 (8) (21–50)38 (8) (24–62) Open table in a new tab Both chin lift with CPAP and jaw thrust with CPAP reduced stridor (median score 1.0 (25%–75% interquartile range 0.0) for both) significantly compared with baseline (2.0 (1.5)) and chin lift (2.0 (1.0)) (Figure 1). There was no relationship between inspiratory airway dimensions and stridor scoring, except for the jaw thrust with a CPAP condition (rs –0.46, P<0.05). All manoeuvres lifted the epiglottis significantly during inspiration (Figure 2). The inspiratory and expiratory dimension changes were significantly correlated during all the manoeuvres (P<0.001): chin lift: rs=0.92; chin lift with CPAP: rs=0.88; jaw thrust: rs=0.86; jaw thrust with CPAP: rs=0.92. Chin lift with CPAP and jaw thrust with CPAP increased the transverse dimension best and were equally effective. Chin lift and jaw thrust manoeuvres without CPAP reduced the transverse distance during inspiration in 10 and six patients, respectively (Figure 3). The inspiratory and expiratory dimension changes were significantly correlated during all the manoeuvres (P<0.001): chin lift: rs=0.74; chin lift with CPAP: rs=0.88; jaw thrust: rs=0.81; jaw thrust with CPAP: rs=0.77. We found that in spontaneously breathing children with large tonsils, chin lift or jaw thrust lifted the epiglottis. When combined with CPAP, the tonsils were moved apart. During anaesthesia, a collapsible segment in the upper airway may narrow or close during inspiration.11Hwang J St John WM Barlett Jr, D Respiratory-related hypoglossal nerve activity: influence of anesthetics.J Appl Physiol. 1983; 55: 785-792Crossref PubMed Scopus (200) Google Scholar In a study of thoracoabdominal motion in children, clinically significant upper airway obstruction was found at 2 MAC (minimal alveolar concentration) sevoflurane.12Motoyama EK Inspiratory muscle incoordination and upper airway obstruction during inhalation anesthesia.Int Anesthesiol Clin. 1997; 35: 45-47Crossref PubMed Scopus (5) Google Scholar We identified airway collapse during late inspiration, which is similar to reports of collapse during sleep.13Woodson BT Wooten MR Comparison of upper-airway evaluations during wakefulness and sleep.Laryngoscope. 1994; 104: 821-828Crossref PubMed Scopus (69) Google Scholar Severe inspiratory collapse may be associated with a marked decrease in intraluminal pressure.13Woodson BT Wooten MR Comparison of upper-airway evaluations during wakefulness and sleep.Laryngoscope. 1994; 104: 821-828Crossref PubMed Scopus (69) Google Scholar The distal pharynx is 'sucked' in and may even obstruct. The lateral walls of the pharynx have a complex architecture, with a number of muscles that have different biomechanical relationships with each other and with other pharyngeal structures.14Drummond GB Influence of thiopentone on upper airway muscles.Br J Anaesth. 1989; 63: 12-21Crossref PubMed Scopus (71) Google Scholar 15Schwab RJ Gupta KB Gefter WB et al.Upper airway and soft tissue anatomy in normal subjects and patients with sleep-disordered breathing. Significance of the lateral pharyngeal walls.Am J Respir Crit Care Med. 1995; 152: 1673-1689Crossref PubMed Scopus (625) Google Scholar In addition to the depression of the activity of upper airway muscles with halothane,16Ochiai R Guthrie RD Motoyama EK Differential sensitivity to halothane anesthesia of the genioglossus, intercostals, and diaphragm in kittens.Anesth Analg. 1992; 74: 338-344PubMed Google Scholar other factors, such as the thickness of the lateral pharyngeal wall, may play a critical role.15Schwab RJ Gupta KB Gefter WB et al.Upper airway and soft tissue anatomy in normal subjects and patients with sleep-disordered breathing. Significance of the lateral pharyngeal walls.Am J Respir Crit Care Med. 1995; 152: 1673-1689Crossref PubMed Scopus (625) Google Scholar 17Shelton KE Woodson H Gay S Suratt PM Pharyngeal fat in obstructive sleep apnea.Am Rev Respir Dis. 1993; 148: 462-466Crossref PubMed Scopus (359) Google Scholar Large tonsils also seem to increase airway collapsibility during inhalational anaesthesia. Our study also supports previous findings that the position of the epiglottis in relation to the posterior pharyngeal wall affects airway patency.18Reber A Wetzel SG Schnabel K Bongartz G Frei FJ Effect of combined mouth closure and chin lift on upper airway dimensions during routine magnetic resonance imaging in pediatric patients sedated with propofol.Anesthesiology. 1999; 90: 1617-1623Crossref PubMed Scopus (81) Google Scholar However, lateral narrowing and posterior displacement of the epiglottis cannot be assessed clinically, for example by airway sounds. We found that chin lift did not improve the patency of the airway. Upper airway narrowing during inspiration results from an imbalance between inspiratory muscle activity and the negative intraluminal pressure generated during inspiration. Halothane anaesthesia affects phasic activity of inspiratory muscles in a dose-dependent manner.16Ochiai R Guthrie RD Motoyama EK Differential sensitivity to halothane anesthesia of the genioglossus, intercostals, and diaphragm in kittens.Anesth Analg. 1992; 74: 338-344PubMed Google Scholar Both anaesthetic agent and the chin-lift manoeuvre affect upper airway muscle tension. The action of negative intraluminal pressure is no longer balanced by the action of the upper airway dilator muscles19Schwab RJ Gefter WB Pack AI Hoffman EA Dynamic imaging of the upper airway during respiration in normal subjects.J Appl Physiol. 1993; 74: 1504-1514Crossref PubMed Scopus (121) Google Scholar and severe collapse, with or without complete obstruction, may occur. Lifting the chin could increase pharyngeal compliance so that the tonsils are 'sucked in' without counterbalance from muscle activity. During propofol anaesthesia, chin lift alone could preserve airway patency;18Reber A Wetzel SG Schnabel K Bongartz G Frei FJ Effect of combined mouth closure and chin lift on upper airway dimensions during routine magnetic resonance imaging in pediatric patients sedated with propofol.Anesthesiology. 1999; 90: 1617-1623Crossref PubMed Scopus (81) Google Scholar however, these children had normal tonsils and this study used magnetic resonance imaging, which did not follow dynamic airway changes. Compared with chin lift, jaw thrust has the advantage that the tension from the tongue and suprahyoid muscles is greater, thus pulling the hyoid ventrally against the root of the tongue and actively widening the pharynx. In addition, the mouth is opened and breathing becomes easier than during chin lift.20Pickering DN Beardsmore CS Nasal flow limitation in children.Pediatr Pulmonol. 1999; 27: 32-36Crossref PubMed Scopus (22) Google Scholar However, there is no correlation between the degree of the mandibular protrusion and the widening of the pharynx in adults.21Hochban W Neumann I Ziegler A Mechanisch-/prothetische Unterkieferprotrusion: Auswirkungen auf den Pharynx [Mechanical/prosthetic protrusion of the mandible].Pneumologie. 1996; 50: 919-923PubMed Google Scholar Mouth opening without mandibular protrusion increases upper airway collapsibility during sleep.22Meurice J-C Marc I Carrier G Sériès F Effects of mouth opening on airway collapsibility in normal sleep subjects.Am J Respir Crit Care Med. 1996; 153: 255-259Crossref PubMed Scopus (191) Google Scholar We found that jaw thrust manoeuvres, which may cause post-operative discomfort, worsened airway calibre during inspiration, although impairment of airway patency occurred in fewer patients during jaw thrust (six patients) compared with chin lift (10 patients). Continuous positive airway pressure may have several effects, including interactions between changes in chest wall stability, pulmonary mechanics, lung volume and respiratory muscle dynamics.23Deegan PC Nolan P Carey M McNicholas WT Effects of positive airway pressure on upper airway dilator muscle activity and ventilatory timing.J Appl Physiol. 1996; 81: 470-479PubMed Google Scholar 24Locke R Greenspan JS Shaffer TH Rubenstein SD Wolfson MR Effect of nasal CPAP on thoracoabdominal motion in neonates with respiratory insufficiency.Pediatr Pulmonol. 1991; 11: 259-264Crossref PubMed Scopus (78) Google Scholar Continuous positive airway pressure increases airway volume and airway area within the retropalatal and retroglossal regions and increases lateral dimensions more than anterior–posterior dimensions.15Schwab RJ Gupta KB Gefter WB et al.Upper airway and soft tissue anatomy in normal subjects and patients with sleep-disordered breathing. Significance of the lateral pharyngeal walls.Am J Respir Crit Care Med. 1995; 152: 1673-1689Crossref PubMed Scopus (625) Google Scholar In our study, CPAP restored airway patency in children with large tonsils during chin lift and jaw thrust by dilating or splinting the upper airway. In conclusion, in spontaneously breathing children with adenotonsillar hyperplasia, chin lift plus CPAP is recommended; jaw thrust plus CPAP is no better and may cause post-operative discomfort. Although little is known about the biomechanics of the upper airway and how the various soft tissues interact mechanically to control the dimensions of the upper airway, the degree of stridor may indicate the efficacy of airway manoeuvres. We thank Ursula Schaller for video transformation and Joan Etlinger for editorial work. This study was supported by the Swiss National Science Foundation (3200-056034.98).