Marathoners' Breathing Pattern Protects Against Lung Injury by Mechanical Ventilation: A Pilot Study

Background Breathing during a marathon is often done empirically in a so-called “2:2 breathing rhythm”. This breathing rhythm is based on cycles composed of four phases: the 1st inspiratory period, 2nd inspiratory period, 1st expiratory period, and, finally, the 2nd expiratory period. We developed a prototype ventilator that can perform intermittent positive pressure ventilation, mimicking the breathing cycle of the 2:2 breathing rhythm. This mode of ventilation was named the marathoners’ breathing rhythm ventilation (MBV) and we hypothesized that MBV may have a lung protective effect.Methods We examined the effects of the MBV on the pulmonary pre-edema model in isolated perfused rabbit lungs. The pulmonary pre-edema state was induced using bloodless perfusate with low colloid osmotic pressure. The fourteen isolated rabbit lung preparations were randomly divided into the inversed ratio ventilation (IRV) group and the MBV group, (both had an inspiratory:expiratory ratio of 1:1). In the IRV group, seven rabbit lungs were ventilated using a Harvard Ventilator 683 with a tidal volume (TV) of 8 mL/kg, a respiratory rate (RR) of 30 cycles/min, and a positive-end expiratory pressure (PEEP) of 2 cmH2O for 60 min. In the MBV group, seven rabbit lungs were ventilated using the prototype ventilator with a TV of 6 mL/kg, an RR of 30 cycles/min, and a PEEP of 4 cmH2O (first step) and 2 cmH2O (second step) for 60 min. The time allocation of the MBV for one cycle was as follows: 1st inspiratory period, 2nd inspiratory period, 1st expiratory period, and 2nd expiratory period (all 0.3 s long), with intermittent resting periods (all 0.2 s).Results Peak airway pressure and lung wet-to-dry ratio after 60 min ventilation were lower in the MBV group than in the IRV group.Conclusion MBV was considered to have a lung protective effect compared to the IRV method.