Breathing in Depth: Spirograms, Curves and Calculations | StemPy Lab
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“Breathing in Depth: Spirograms, Curves and Calculations” is available to Standard subscribers.
Beyond the textbook: reading spirometer graphs of healthy and diseased lungs, working out ventilation and dead space, calculating partial pressures and the oxygen carried by blood, and reasoning about every shift of the dissociation curve. Twelve harder problems and a full timed mock exam.
3Lessons12Problems2Python Labs1Question Set1Mock Test
Reading and using spirograms: A spirogram is read by taking differences of levels, and the levels are measured from an empty lung. Diseases change the picture in known ways: air is trapped in emphysema, and stiff lungs hold less in fibrosis. The conducting part is a dead space, so the air that reaches the alveoli is less than the air moved. This lesson goes beyond the textbook.
Partial pressures and gas calculations: The partial pressure of oxygen in the air in the windpipe is lower than in dry air, because water vapour takes a share of the pressure. The alveolar pO2 can be estimated from it. The oxygen content of blood depends on the haemoglobin as well as on the saturation. Diffusion depends on area, gradient and thickness. This lesson goes beyond the textbook.
Reading shifts of the dissociation curve: The curve can shift, and a shift is read in two ways: at the same pO2 the saturation changes, or the same saturation needs another pO2. A shift to the right releases oxygen more easily, and a shift to the left holds it more tightly, as in foetal haemoglobin. Carbon monoxide blocks the haemoglobin. The Bohr and Haldane effects link oxygen and carbon dioxide. This lesson goes beyond the textbook.