Jaden Hunter, 11 years old, stumbled into his parents’ bedroom. It was 4 a.m. and completely dark. Unable to talk, he simply grabbed his mother’s foot to get her attention. His mom awoke immediately and shouted “Brandon, get up!” Without explanation, she knew what the problem was. She helped Jaden onto the bed next to her husband, then raced down the stairs and grabbed the backpack full of medical equipment they used when things got this bad. When she returned Jaden was sitting on the bed being comforted by his father. She then slipped a mask over his face to deliver nebulized albuterol.

The Oxygen-Hemoglobin Dissociation Curve

Following his nebulizer treatment, Jaden was breathing a little better and able to talk. “I used my rescue inhaler all night . . . it didn’t help!” He paused for a breath and then said, “We used my nebulizer right before bed . . . I still couldn’t sleep . . . My chest feels tight.” “Do you feel like we need to go to the hospital?” his mom gently asked. Jaden looked down and simply nodded his head yes. Having suffered from asthma since the age of four, he understood that his symptoms had reached a point where they couldn’t be adequately managed at home. Luckily, the hospital was just a short drive away. It wasn’t the first time they had made this trip in the middle of the night. In fact, it seemed like every time Jaden had breathing problems severe enough to warrant an emergency room trip it was in the middle of the night. As they arrived at the hospital Jaden’s chest tightness was once again beginning to increase and he was unable to take deep breaths. The panic this caused him lead to tears, which only made his breathing problems worse. His mom knew that the best thing she could do to help him was to stay calm herself and gently guide him through breathing exercises, so she set aside her own fears and panic, and started to do just that as she checked him into the ER. Once back in the examining room a pulse oximeter was immediately placed on Jaden’s finger and vital signs monitored. Jaden’s oxygen saturation (So2) was 82%.

The Effects of Air Flow on Po2 and Pco2

Because asthma is an obstructive respiratory disease caused by a decreased diameter in the respiratory passageways, Jaden was having problems both with breathing in and with breathing out. Air flow through the respiratory passageways can be calculated by using the following formula:

F = ΔP / R Where: F = air flow, ΔP = the difference between atmospheric and intrapulmonary pressure

R = resistance

Questions

1. How does the body create a difference between atmospheric and intrapulmonary pressures to cause air flow to and from the lungs?

2. In Jaden’s case, which factor in the above equation changed, causing air flow to and from his lungs to decrease?

3. Without medication or treatment, how could Jaden compensate to maintain airflow to and from his lungs despite his narrowed airways? Hint: think about how the muscles in the chest help expand and contract the chest cavity. Explain why asthma exacerbations and other obstructive lung diseases that make it difficult for air to move into and out of the lungs can be exhausting for the sufferer.

5. The Pco2 of venous blood is normally 45 mmHg. How would you expect Jaden’s current Pco2 level to compare to the normal level? Explain your answer.

6. How would Jaden’s Pco2 level affect the rate at which his oxygen is dissociating from hemoglobin? In your answer, be sure to also include how co2 levels affect ph