Importance of both Hemidiaphragms in Maintaining Optimal Breathing Mechanics, Respiratory Rate, and Hemoglobin Oxygen Saturation: a Case Study

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Background: The mechanical process of breathing consists of the abdominal breathing (AB) driven/generated by the diaphragm, and thoracic breathing (TB) generated by the intercostal muscles. The coordinated movements of the two portions of diaphragm account for 80% of the inspiration, although their exact roles are still investigated. While bilateral diaphragmatic paralysis causes severe shortness of breath, unilateral hemidiaphragm paralysis is asymptomatic at rest, making it challenging to diagnose. Objective: To measure and compare the amplitudes of abdominal and chest movements in different body positions between a healthy individual and an individual with unilateral diaphragmatic paralysis (phrenic nerve injury). Methods: Changes in the circumference of the abdomen and chest were measured during inhalation and exhalation with respiratory plethysmography belts (placed on standardized reproducible positions on the chest, and abdomen) in different body positions: sitting (SI), standing (ST), lying (SU) and prone (PR) in a healthy (H) individual and an individual with unilateral diaphragmatic paralysis. (Ph). Breathing frequency and other parameters were calculated from the measured signals. Furthermore, the blood oxygen saturation (SpO2) was measured with a pulse oximeter. Results: Percent (%) contribution of abdominal breathing H/Ph: SI: 29.6/16.0; ST: 72.8/50.3; SU: 90.6/-53.5; PR: 32.8/1.1. A negative sign shows paradoxical breathing. Respiratory rate (1/min) H/Ph: SI:18.7/19.4; ST: 19.0/15.0; SU: 15.9/37.5; PR: 16.6/35.9. Phase angle of abdominal and thoracic breathing curves (degrees) H/Ph: SI: 4.09/-5.73; ST: -20.82/-9.48; SU: 3.68/184.29; PR: 25.08/-26.51. In case of a negative sign, chest breathing precedes abdominal expansion, and vice versa in the case of a positive sign. A value around 180 degrees indicates paradoxical breathing, seen in Ph, when SpO2 significantly decreased: SI: 93% vs. SU: 82%. Conclusions: In different body positions, the amplitude changes of the abdomen and chest differed substantially during the complete respiratory cycle. Both portions of diaphragm are important because in unilateral phrenic nerve injury, abdominal breathing markedly decreased in most body positions compared to a healthy individual. Furthermore, paradoxical breathing occurred in a supine position, as indicated by a change in the phase angle. The lowest respiratory rate was measured in standing position (15/min), in which the participation of the abdomen/chest ratio was 50.3%, / 49.7%, while the highest value was obtained in supine position (38 breaths/min), which coincided by a decreased hemoglobin oxygen saturation / i.e. oxygen intake. In case of hemidiaphragm paralysis, the diminished mechanical breathing effciency requires a higher respiratory rate to sustain/maintain hemoglobin oxygen saturation. However, this elevated respiratory rate also increases energy consumption, potentially resulting in dyspnea during physical exertion / exercise. Ministry of Innovation and Technology (MIT) of Hungary-NRDI TKP2020-NKA-17, TKP2021-EGA-37, and National Research, Development, and Innovation Offce (NKFIH) OTKA K 132596 K_19, and Hungarian Academy of Sciences, Post-Covid 2021-34, and HUN-REN-SE: 02068 of Hungary. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.