Does ultrasound measured distance from front of

abdomen to spine correlate with depth of breathing?

Dr John RutherfordDr Mahboob Khan

Dumfries & Galloway Royal Infirmary

Introduction

• To compare ventilation with facemask and LMA ventilation

• Need a method of assessing ventilation that is not dependent on measuring exhaled gas…

• Rechner et al. described measuring abdominal movement Paed Anesth 2007; 17: 609-610

• We didn’t have their equipment…

Methods

• Local research ethics approval

• Information sent to children and parents when booking for surgery

• Consent

• Age <16 years

• GA involving LMA

• Exclusions; reflux, language difficulties or lack of consent

• Age

• Weight

• Height

• IV or inhalational induction then LMA• Ventilated at 5, 10 and 15 cmH2O• M mode ultrasound with curvilinear probe

(Sonosite MicroMaxx) and pneumotachograph for tidal volumes with Datex Ohmeda Aestiva

Analysis

• Changes in upper abdominal distance analysed with paired T-tests using Microsoft Excel Office 2003

Results

• 31 children and parents approached

• 7 refused consent

• 1 not read the information

• 1 unable to communicate in English

• 1 active respiratory tract infection

• 21 consented but unable to see spine in one child

• Age range 1 – 11 years

• Male to female 9 to 12

• AP distances similar for pressure regardless of age of child

• T-test 5-10 cmH2O p< 0.005

– 10-15 cmH2O p< 0.0001

– 5-15 cmH2O p< 0.0001

• Difference in tidal volume +/- probe = 2.6%

Change in AP ventilation with 5, 10 and 15 cmH2O

0

1

2

3

4

5

6

7

8

9

10

Pressure ventilation

Ch

ang

e A

P d

ista

nce

mm

5 10 15

Limitations

• Same location of probe

• Same angle of probe

• However the equipment is widely available in the UK

Questions?

?

Acknowledgements

• Dr Petr Hrobar, consultant radiologist

• Dr Gwen Baxter, R&D department

• Dr Alastair Baxter, consultant paediatric anaesthetist

• We are not aware of any conflict of interest