Acute Respiratory Distress Syndrome (ARDS) is a serious form of lung injury that can affect patients who require mechanical ventilation. This can be fatal, especially when the lower airway and alveoli fail to exchange oxygen and carbon dioxide for a sustained period of time due to collapse or excess fluid accumulation. ARDS is managed using a variety of strategies including Lung Recruitment Maneuvers (LRM). LRM’s come in many forms, but in general they use multiple ventilator modes, pressures, and respiration patterns in an attempt to open collapsed alveoli. Demonstrating the effectiveness of LRM with an objective measurement has been a challenge and because of this the technique is not without controversy.
In a new paper, Brian Walsh, RRT-NPS, FAARC, and Michael Davis, RRT, demonstrate that monitoring the acidity of the exhaled breath condensate from mechanically ventilated patients can provide an objective measurement and furthermore, this measurement may be useful as an indicator of LRM effectiveness. Their paper entitled “The Effects of Lung Recruitment Maneuvers on Exhaled Breath Condensate pH” is now in press in the Journal of Breath Research.
Both Mr. Walsh and Mr. Davis have been active breath biomarker researchers for over a decade, as well as registered respiratory therapists. Mr. Walsh is a Clinical Research Coordinator at Boston Children’s and active member of the American Association of Respiratory Care; Mr. Davis works with the Breath Research Laboratory at Virginia Commonwealth University and sits on the International Association of Breath Researchers Task Force for Breath Collection and Analysis Standardization. They have each focused their careers on clinical and translational research and are authors on numerous publications.
Mr. Walsh, an inventor of the Airway Lining Fluid Acidity Monitor (ALFA), used this device to monitor the exhalate exiting the ventilator at the exhaust port. As the exhalate passes through the ALFA, it is condensed, gas-standardized to remove dissolved carbon dioxide, and analyzed using a computerized pH measurement system. The results are recorded and compared to determine the correlation of pH changes in relationship to stage of the LRM. Breath pH is one of the most validated biomarkers in exhaled breath and is widely accepted as an indication of lung acidification due to lung injury and disease.
The data showed a clear correlation between LRMs and lung acidification. While there are several possible interpretations of these data; the leading theory is that LRM’s do in fact open collapsed alveoli as gas exchange improves from baseline. When these previously-closed and stressed alveoli open, they likely release acids which had been trapped. As more studies characterize these changes in acidity and validate these hypotheses, the LRM that opens the lung while doing the least amount of harm may gain wider acceptance as a method of managing patients with ARDS. This could in turn improve time to therapeutic goals, reduce length of stay on the mechanical ventilator and possibly improve survival rates for these very sick patients.