RT Journal Article SR Electronic T1 Pulse oximetry during saline challenge in vocal cord dysfunction and airway hyper-responsiveness JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP p2165 VO 38 IS Suppl 55 A1 Allyson Upward A1 Jeffrey Pretto A1 Michael Hensley YR 2011 UL http://erj.ersjournals.com/content/38/Suppl_55/p2165.abstract AB The hypertonic saline challenge (HSC) is a commonly used diagnostic tool to assess airway hyper-responsiveness (AHR) and vocal cord dysfunction (VCD). Dyspnoea during testing is not uncommon and we postulated that oxygen desaturation may be a causative factor.Aim: To document the degree of arterial desaturation during saline challenge and compare SpO2 changes in AHR, VCD and negative responses.Method: SpO2 (Nellcor N595) was continuously recorded during 78 consecutive HSCs. SpO2 data was averaged over 32 seconds and minimum values used for analysis. Change in dyspnoea score (Borg) during the challenge was also recorded. Results were classified as AHR (change in FEV1 ≥15%), as VCD (change in MIF ≥20%) or negative otherwise.Results: Mean (SD) FEV1 was 86 (15)% predicted for AHR (n=20), 92 (18)% for VCD (n=18) and 94 (18)% for negative results (n=40). There was a consistent trend in SpO2 for all subject groups with significant desaturation during the final doses of saline and during bronchodilatation (ANOVA p<0.001), and consistent resaturation during spirometric efforts. Mean (SD) maximum falls in SpO2 of 4.3% (2.7) were observed for AHR, 4.1% (2.0) for VCD and 4.4% (2.7) for negative results. There was no relationship between change in dyspnoea and degree of desaturation (p=0.43).Conclusion: Hypertonic saline challenge causes a significant and reproducible pattern of arterial desaturation irrespective of the test response. These data would be consistent with progressive hypoventilation during HSC rather than indicating desaturation due to worsening ventilation-perfusion mismatching. Hypoxaemia does not appear to be the primary cause of dyspnoea during HSC.