Mr Siphо Dlаmini, а 28-yeаr-оld prоfessional rugby player, sustains a serious abdominal injury during a match and undergoes emergency abdominal surgery. Before the injury, he had no known cardiovascular or respiratory disease and regularly participated in intensive training. Following surgery, he is admitted to the intensive care unit, where he is sedated and receives controlled invasive mechanical ventilation. The multidisciplinary team assesses his breathing while he is sitting upright. As his condition improves and he receives medical clearance, his rehabilitation progresses from sitting and walking to supervised exercise on a stationary bicycle. The physiotherapist reduces the workload and encourages slower, deeper breaths. Later in his rehabilitation, he tolerates progressively higher workloads as he prepares to return to professional sport. Discuss how Mr Dlamini’s respiratory and cardiovascular systems maintained oxygen delivery to active muscles and remove carbon dioxide produced during the cycling session. Include alveolar ventilation, arterial PO₂ and PCO₂, muscle oxygen delivery and extraction, and the Bohr effect. [BLANK-1]
Mr Thembа Mоkоenа, а 64-year-оld man with a long smoking history and diagnosed with an obstructive disease, attends a preoperative assessment before elective hernia repair. He reports progressive breathlessness and a persistent cough. At rest, he breathes rapidly with a reduced tidal volume and has prolonged expiration. Pulmonary function testing produces the following results: Measurement & ResultTotal lung capacity (TLC): Within the normal rangeResidual volume (RV): IncreasedFEV₁: ReducedPost-bronchodilator FEV₁/FVC: 55%Arterial PO₂ (on room air): 55 mmHg (reference: 80–100 mmHg)Arterial PCO₂ (on room air): 55 mmHg (reference: 35–45 mmHg)Explain why Mr Mokoena’s rapid shallow breathing is inefficient despite his increased respiratory rate. [BLANK-1]