| RESPIRATORY PHYSIOLOGY Problems : Respiratory Ventilation |
1. A patient has a VC of 4.8 L, an ERV of 1.2 L, and an FRC of 2.5 L. What are his RV, TLC, and IC? Are these volumes within the normal range? (Assume these are measurements on a young man of average size.)
2. After recovery from surgery involving cardiopulmonary bypass, patients often require positive pressure ventilation to assist their breathing. In a certain patient, a pressure of 30 cm H2O is needed for a tidal volume of 0.9L. Calculate respiratory system compliance, and decide whether the result of your calculation indicates the respiratory system is stiffer than normal, more compliant than normal, or within the normal range.
3. For the following three patients, indicate the classification of the ventilatory deficiency -- restrictive lung disease or obstructive -- and whether the condition appears acute or chronic. (Note: Isoproterenol is a bronchodilator which is effective in reducing airway resistance in acute conditions but is less effective in chronic obstructive disease.)
PATIENT A: Male, age 62, whose work was coating pipes with an asbestos compound. Smoked 30 cigarettes daily. Chest x-ray showed a massive shadow in the left lower lobe
| Predicted Value | Measured Value | Measured/Predicted | Value after dilator | |
| VC | 3.1 L | 0.9 L | 29% | 0.9 L |
| FEV-1 | 2.5 L | 0.8 L | 32% | 0.85 L |
| FRC | 3.2 L | 1.6 L | 50% | 1.6 L |
| TLC | 5.3 L | 2.2 L | 42% | 2.2 L |
| FEV-1/VC | >80% | 88% | 94% |
PATIENT B: Male, age 50. Smoked 2 packs of cigarettes a day for past 30 years. Chronic cough with sputum. Progressively increasing dyspnea.
| Predicted Value | Measured Value | Measured/Predicted | Value after dilator | |
| VC | 4.1 L | 4.1 L | 100% | 4.1 L |
| FEV-1 | 3.3 L | 1.4 L | 42% | 1.5 L |
| FRC | 2.4 L | 3.4 L | 142% | 3.4 L |
| TLC | 5.0 L | 6.0 L | 120% | 6.0 L |
| FEV-1/VC | >80% | 34% | 36% |
PATIENT C: Male, age 28. Recurrent attacks of wheezing since early twenties, precipitated by anxiety.
| Predicted Value | Measured Value | Measured/Predicted | Value after dilator | |
| VC | 4.9 L | 4.0 L | 82% | 4.5 L |
| FEV-1 | 3.9 L | 1.5 L | 39% | 3.0 L |
| FRC | 3.6 L | 4.0 L | 110% | 3.4 L |
| TLC | 6.0 L | 6.6 L | 110% | 6.6 L |
| FEV-1/VC | >80% | 38% | 67% |
4. In the figurer below are shown alveolar pressure, intrathoracic pressure, and lung volume for a typical respiratory cycle of a normal person at rest.
A. Explain the shape of the intrapleural and alveolar pressure curves.
B. How would these curves be expected to change during heavy exercise?
C. How would these curves be expected to change in a person with severe restrictive disease (e.g. fibrosis)?
D. How would these curves be expected to change in a person with severe emphysema?
5. A bright lad decides to lengthen his short snorkel with a 3 meter hose so he can dive deeper. Should you notify the life guard? (With credit to J Hildebrandt.)
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AC Brown 2004 |