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Variation in size of laryngoscope blades used in preterm newborns
  1. Emily A Kieran1,2,3,
  2. Colm P F O’ Donnell1,2,3
  1. 1Department of Neonatology, The National Maternity Hospital, Dublin, Ireland
  2. 2National Children's Research Centre, Dublin, Ireland
  3. 3School of Medicine and Medical Science, University College Dublin, Dublin, Ireland
  1. Correspondence to Dr Emily Kieran, Department of Neonatology, The National Maternity Hospital, Holles Street, Dublin 2, Ireland; emilykieran{at}

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Many preterm infants are intubated for breathing support and/or surfactant administration. Intubation attempts in newborns are often unsuccessful.1 ,2 Laryngoscopes are used to visualise the vocal cords when attempting intubation. To successfully intubate a baby, the operator needs a good view of the larynx and vocal cords. If the blade of the laryngoscope is too short, the vocal cords will not be visualised.3 If the blade is too long, it may cause trauma to fragile structures in the oropharynx. Inadequate views of the vocal cords have been identified as the reason for the majority of failed intubation attempts in the delivery room.1 Poor visualisation of the vocal cords can also increase the duration of intubation attempts, even in the hands of experienced operators.2 Longer intubation times are associated with adverse events, including hypoxaemia, bradycardia and increased intracranial pressure.2 ,3

The size of laryngoscope blade used depends on the size of the infant. Three sizes of blades are used when intubating newborns: 1, 0 and 00. The Newborn Life Support Course recommends using a size 1 blade for term infants, a size 0 for preterm infants and consideration of a size 00 blade for extremely preterm newborns.4 Other guidelines suggest the size of the laryngoscope blade used should be determined by the infants weight (size 1 for infants >3 kg, size 0 for infants 1–3 kg and size 00 for infants <1 kg).3

During attempted intubation of an extremely preterm infant at our hospital, we found that a size 00 blade seemed very large and mostly obscured the view in the infant's oropharynx. The same operator found it much easier to visualise the same infant's vocal cords during the subsequent attempt when he used a size 00 blade made by a different manufacturer. We thus suspected that the size of laryngoscope blades marked as the same ‘size’ may vary between manufacturers and measured one size 0 and one size 00 laryngoscope blade of each of three models used at our hospital (Heine Classic, Heine Optotechnik, Herrsching, Germany; KaWe standard Miller, Kilrchner & Wilhelm, Asperg, Germany; and Welch Allyn Halogen Fiber Optic, Welch Allyn, Skaneateles Falls, New York, USA). We recorded the length, height and width of the portion of the laryngoscope blade that is inserted into the mouth for each type of blade. All measurements were taken with the same dividers and calculated in millimetres using the same metal ruler.

Though the size 0 blades we measured did not vary greatly between manufacturers, there were substantial differences in the size 00 blades (table 1 and figure 1). We found a 13 mm (greater than one-third) difference in the length of blades made by two different manufacturers. We believe it is important that operators who have difficulty in visualising the vocal cords of extremely preterm infants despite using a blade of an appropriate size are aware that laryngoscope blades of the same ‘size’ made by different manufacturers may vary substantially in size.

Table 1

Measurement of size 00 and 0 laryngoscope blades

Figure 1

Size 00 Heine (top), KaWe (middle) and Welch Allyn (bottom) laryngoscope blades with the measurements of (A) length, (B) height and (C) width indicated.


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  • Contributors EAK was involved in study design, data collection and interpretation and wrote the first draft of the manuscript. CPFO'D was involved in study design, helped in data collection and interpretation and critically revised the manuscript for intellectual content. Both authors approved the final draft of the manuscript.

  • Competing interests None.

  • Provenance and peer review Not commissioned; internally peer reviewed.