1. LUNG FUNCTION IN F-18 PILOTS USING   POSITIVE PRESSURE BREATHING SYSTEM Matti Mäntysaari, Ville Mattila and Tuomo Leino Aeromedical Centre, Helsinki and Air Force Command, Tikkakoski, The Finnish Defence Forces, Finland

2. Disclosure Information 88th Annual Scientific Meeting Matti Mäntysaari
I have no financial relationships to disclose.
I will not discuss off-label use and/or investigational use in my presentation.

3. Background
In fighter manoeuvring great inertial forces in head-to-foot direction cause large hydrostatic pressure gradients
At +9 Gz sufficient blood pressure at head level requires about 300 mmHg blood pressure at heart level

4. Introduction
In the Finnish Air Force the positive pressure breathing system of F-18 is used during high G maneuvers:
Starts at +4 Gz
12 mmHg linear increase per +1 Gz
Maximum 60 mmHg at +9 Gz

5. Positive Pressure Breathing for Anti-G F/A-18C/D Hornet, Finnish Air Force
pressure regulator
chest counter pressure vest
oxygen mask and helmet with automatic mask tensioning
extended coverage anti-G suit

6. Transmission of upper airway pressure to thorax
Grönkvist et al. 2008

7. Aim of Study
Does the positive pressure breathing system of F-18 have negative effects on pilots’ ventilatory lung function?
Possible mechanisms:
pressure load on lung structures?
dry cough – inflammation?

8. Study Desing Cross sectional study
Data from annual aeromedical examinations
Flow-volume spirometry
F-18 pilots compared to age-matched controls

9. Subjects
40 pilots with more than 1000 F-18 flight hours were compared to an age-matched group of pilots not flying F-18 (control group).

10. Methods
Lung function was measured using flow-volume spirometry with test of bronchodilator response. Data are given as mean ± SD and T-test was used in statistical analysis.

11. Flow-volume spirometry
ATS/ERS 2005 Standardisation of Spirometry
Salbutamol 0.4 mg with spacer device for testing airflow-limitation reversibility

12. Subjects: Basic characteristics
F-18 pilots Controls p Total flt hrs 1978 ± ± Height (cm) 180 ± ± * Weight (kg) 82 ± 9 83 ± Age (yrs) 39 ± 4 37 ± (mean ± SD) Use of tobacco products was not significantly different in the two groups.

13. Results – Flow-volume spirometry
F-18 pilots Controls p FVC (l) 5.80 ± ± FEV1(l) 4.43 ± ± MEF50% (l/s) 4.59 ± ± PEF (l/s) ± ± (mean ± SD) Age, height and weight as co-variates: no effect on significance of between-group difference

14. Results – Brochodilator response
F-18 pilots Controls p dFVC (%) ± ± dFEV1(%) 4.41 ± ± dMEF50%(%) ± ± dPEF (%) 2.55 ± ± (mean ± SD) Age, height and weight as co-variates: no effect on significance of between-group difference

15. Conclusions (1)
The lung function was not significantly different in F-18 pilots with more than 1000 flight hours as compared to an age matched control group without F-18 experience.

16. Conclusions (2)
Our findings suggest that the positive pressure breathing system used in F-18 does not affect negatively pilots’ ventilatory lung function.

17. Thank you

18. Forced vital capacity (FVC)
Forced expiratory volume in one second (FEV1)
Maximal instantaneous forced expiratory flow at 50% of FVC (MEF50% )
Peak expiratory flow ( PEF)