Comparison of S/T mode with iVAPS mode for a COPD patient¹

A case study

Hideki Ishihara, Director of the Department of Respiratory Medicine and Intensive Care Osaka Prefectural Medical Centre for Respiratory and Allergic Diseases, Japan.

Patient history

• Eighty-three year old male with COPD.
• Eight years of NIV therapy (with Mirage QuattroTM mask) to treat hypoventilation, in addition to having long term oxygen therapy.
• Nocturnal desaturation was observed so patient was re-admitted to adjust NIV settings.

Challenges with initial treatment:

• The patient reported discomfort and felt that the air was being “pushed in” despite the need to exhale.
• He also experienced discomfort when falling asleep.
• ResScan shows intermittent leak.
• Despite these settings, desaturation was observed during REM sleep.
• Therefore, a means to improve desaturation while addressing patient comfort, was required.

Switch to iVAPS mode

Basis for settings

• The target alveolar ventilation volume was calculated at 5.1 L/min using tidal volume measured in S/T mode and using the Va calculator.
• Min PS was kept at the default of 2 cm H₂O. Max PS was set to IPAP from S/T mode plus 1 cm HO.
• Overall, there was an improvement in several parameters, as shown in the figures below.
• On iVAPS mode, there was increased spontaneous breathing and target alveolar ventilation was achieved.
• Patient no longer complained of high pressure when falling asleep. Due to improved comfort, there was better therapy adherence.
• More spontaneous triggering and cycling.

 Limitations

• It would be recommended to set iBR to the patient’s spontaneous respiratory rate (i.e. 16 bpm) and re-evaluate Ti Max.
• SpO₂ was not normalised despite pressure reaching Max PS. Therefore consider increasing Max PS and EPAP.

Conclusions

• COPD patient who had nocturnal desaturations was treated on both S/T mode and iVAPS mode.
• iVAPS mode improved patient comfort and ventilation.
• However, care needs to be taken when adjusting settings from S/T mode to iVAPS mode.
• By optimising settings, normalised gas exchange is expected to be achieved in this patient.