Question: A 58-year-old woman attended the consultation due to dyspnea of ​​medium effort, muscle weakness in the upper extremities and dysphagia to solids of three months of evolution. Physical examination revealed a loss of strength in the upper limbs with preserved sensitivity. Pulmonary auscultation shows generalized hypophisis. A chest x-ray is performed, showing uninspired lungs and laminar atelectasis in the lung bases. Gasometry shows pH 7.39, PCO2 48 mmHg, PO2 63 mmHg, HCO3 28 mmol / L, SatO2 93%. The combination of physiological mechanisms that best explain this gasometry is: 
 Options:  <1> Decrease in FiO2 (inspired fraction of oxygen) and alteration of diffusion. <2> Alteration of diffusion and disturbance of the ventilation / perfusion relationship. <3> Alveolar hypoventilation and decrease in FiO2. <4> Disorder of the ventilation / perfusion relationship and alveolar hypoventilation. <5> Increased pulmonary artery pressure and decreased diffusion.
4