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Breathing Patterns Associated with Pursed Lips Breathing - Impact on CO2 Elimination: A Single Breath VCO2 Bench Model
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A7065 - Breathing Patterns Associated with Pursed Lips Breathing - Impact on CO2 Elimination: A Single Breath VCO2 Bench Model
Author Block: B. L. Tiep, M. Barnett; Pulmonary, Respiratory Disease Management Inst, Monrovia, CA, United States.
Rationale: Pursed lips breathing (PLB) relieves dyspnea, increases arterial oxygenation, improves CO2 elimination, and enhances ventilatory efficiency. Multiple factors that vary widely and unpredictably are altered by PLB including breath rate, tidal volume (VT), pattern, and dead-space (VD). This study addresses the impact of upper airway bypass and expiratory retard on CO2 elimination (VCO2). We designed a bench breathing model that keeps breath rate, tidal volume (Vt) and alveolar CO2 constant while studying the effect of upper airway bypass via nasal-to-oral (N-O) breathing vs nasal-to-nasal (N-N) breathing. Also studied was the impact of expiratory retard on N-O and N-N breathing. Phases of the VCO2 loop: I: first part of exhalation (no CO2); II: mixed gas; III: alveolar plateau; IV: inhalation.
Methods: The breathing simulator comprised motorized bellows fed by a constant CO2 infusion; 150 ml of airway VD: upper airway (40ml) + lower airway (110 ml). VCO2/Volume comprised single breath VCO2 loop - measuring CO2 re-uptake VD at beginning inhalation. The CO2 probe positioned at the junction between upper and lower VD (larynx) determined the effect of bypassing upper airway VD. Constants were CO2 in the bellows, breath rate, Vt. We compared VCO2/breath: 1.) VD upper airway bypass via N-O vs N-N; 2.) expiratory retard; 3.) VCO2 loop pattern, and 4. calculated ventilatory efficiency (Ve) [e.g. NO - NN]/NN]
Results: VCO2 measurements were the enclosed loop volumes. Breath rate = 15; Vt = 500 ml. 1. Upper airway bypass via N-O: VCO2 = 13.7 ml vs N-N 11 ml. Ve = + 22.%. 2. Expiratory retard for N-N: VCO2 = 12.6 ml vs 11 ml. Ve = +14.5%. Expiratory retard for N-O VCO2 = 14.1 ml vs 13.7 ml Ve = +3%. Loop Observations: N-O widens the loop at inspiratory phase IV; expiratory retard increases the slope of phase II while raising the alveolar plateau phase III. Each intervention increases CO2 elimination.
Discussion/Conclusions: Breathing pattern may directly impact CO2 elimination. Upper airway bypass, and slowing exhalation while maintaining the same Vt and rate increases CO2 elimination. PLB taught to patients often includes slower exhalation and inhaling nasally/exhaling orally. These strategies are addressed in this model. Many patients discover PLB by relief of dyspnea. This bench model with its advantages and limitation was designed identify strategies to enhance CO2 elimination. Further studies are recommended.
Clinical implications: Bench modeling may provide insights to improve gas exchange and ventilatory efficiency.
Author Block: B. L. Tiep, M. Barnett; Pulmonary, Respiratory Disease Management Inst, Monrovia, CA, United States.
Rationale: Pursed lips breathing (PLB) relieves dyspnea, increases arterial oxygenation, improves CO2 elimination, and enhances ventilatory efficiency. Multiple factors that vary widely and unpredictably are altered by PLB including breath rate, tidal volume (VT), pattern, and dead-space (VD). This study addresses the impact of upper airway bypass and expiratory retard on CO2 elimination (VCO2). We designed a bench breathing model that keeps breath rate, tidal volume (Vt) and alveolar CO2 constant while studying the effect of upper airway bypass via nasal-to-oral (N-O) breathing vs nasal-to-nasal (N-N) breathing. Also studied was the impact of expiratory retard on N-O and N-N breathing. Phases of the VCO2 loop: I: first part of exhalation (no CO2); II: mixed gas; III: alveolar plateau; IV: inhalation.
Methods: The breathing simulator comprised motorized bellows fed by a constant CO2 infusion; 150 ml of airway VD: upper airway (40ml) + lower airway (110 ml). VCO2/Volume comprised single breath VCO2 loop - measuring CO2 re-uptake VD at beginning inhalation. The CO2 probe positioned at the junction between upper and lower VD (larynx) determined the effect of bypassing upper airway VD. Constants were CO2 in the bellows, breath rate, Vt. We compared VCO2/breath: 1.) VD upper airway bypass via N-O vs N-N; 2.) expiratory retard; 3.) VCO2 loop pattern, and 4. calculated ventilatory efficiency (Ve) [e.g. NO - NN]/NN]
Results: VCO2 measurements were the enclosed loop volumes. Breath rate = 15; Vt = 500 ml. 1. Upper airway bypass via N-O: VCO2 = 13.7 ml vs N-N 11 ml. Ve = + 22.%. 2. Expiratory retard for N-N: VCO2 = 12.6 ml vs 11 ml. Ve = +14.5%. Expiratory retard for N-O VCO2 = 14.1 ml vs 13.7 ml Ve = +3%. Loop Observations: N-O widens the loop at inspiratory phase IV; expiratory retard increases the slope of phase II while raising the alveolar plateau phase III. Each intervention increases CO2 elimination.
Discussion/Conclusions: Breathing pattern may directly impact CO2 elimination. Upper airway bypass, and slowing exhalation while maintaining the same Vt and rate increases CO2 elimination. PLB taught to patients often includes slower exhalation and inhaling nasally/exhaling orally. These strategies are addressed in this model. Many patients discover PLB by relief of dyspnea. This bench model with its advantages and limitation was designed identify strategies to enhance CO2 elimination. Further studies are recommended.
Clinical implications: Bench modeling may provide insights to improve gas exchange and ventilatory efficiency.
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