On mountains about 8000ft. from the sea level one feels difficulty in breathing due to considerable decrease in the oxygen in the air. Consequently, the alveolar pO₂ reduces and oxygen cannot be diffused into the blood. Thus, the process of oxygenation of blood is progressively gets decreased to such an extent that the person feels mountain sickness. It produces a number of symptoms like breathlessness, headache, dizziness, nausea, vomiting and a bluishness of skin, nails and lips. This is because of lack of adequate oxygen. People suffering from heart ailment or blood pressure should not go to such a height.