COPD: Changing and not the Same for all Sufferers

Heterogeneous Disease

COPD has shown to be a heterogeneous disease. As with any other disease, there seems to be very unique and common features to help physicians in the diagnostic process as well as in therapeutic decisions. Long time ago, COPD was considered to be a syndrome based on a reaction to the continuous aggression by cigarette smoking imposed against the beautiful lung airway structure. Patients were considered to have one of two typical expressions of consequences: chronic bronchitis or emphysema.

Santa Klaus maybe had COPD (because of the chimneys?)

There are some patients with more features of chronic bronchitis but we never forget the classical emphysematous patient: skinny, always smoking, with their head among shoulders instead of above them, dry cough, etc, etc. In the meantime, the chronic bronchitis patient was fatter, smiling, coughing and producing sputum, and breathing with difficulty (just imagine Santa Klaus after he inhaled smoke while working…).

Question

The big question is: why some patients show one or other predominant characteristic of the disease? why ones are emphysematous while others have predominant chronic bronchitis?

Some help but different

That reminds us that categories help but are not definite. That reminds physicians that each patient is different to the other although key features may be common. Not all patients respond the same to cigarette smoking injure so they maybe don’t have to respond equally to same therapeutic measures. They even neither have the same behavior nor have the same attitude during the medical office dialogue. Understanding the actual or potential differences may help support a better approach to disease management.

More differences

So, will everybody have same adverse events? will they have same set of surrounding diseases? (which we call comorbidities). Maybe not and perhaps some may be followed up with spirometry, while others need to be followed up with activity levels, or breathlessness (dyspnea) scales, or symptoms exacerbations, or oxygen levels changes, just for mentioning a few couple of parameters.

Changing focus of investigations

These considerations, fortunately, have led some investigators to start talking about different phenotypes of COPD. Although it challenges our current understanding of the disease, already considered complex and under continuous evaluation to make it look simpler, patients and multiple clinical trials have been shown that the damage is not as homogeneous as we could have thought in the population.

Similarities

We also know that in metabolic diseases some patients present different complications (e.g. diabetics with more renal impairment than neuropathy). In hypertension, some have stroke while other have heart predominant damage. They all have different medical approaches and require different directions: some need to loss weigh, others have to change diet, others respond to a drug better than others, etc.

A Disease in evolution

COPD is starting its own cycle of research, adjustment according to the evidence, natural evolution of the crowd of patients, new and contradictory trends in management, followed by more research and so forth. The present is here and now and the hope is increasing thanks to the investigators who have given passion to this issue. Each patient is different because, simply: individuals are not the same.

Lungs, Kidneys, Oxygen: an orchestrated response

Receiving all circulating blood

Lungs and Kidneys work in an orchestrated manner to maintain an appropriate level of oxygen in blood. Both organs receive all blood flow at one point. Lungs receive blood to facilitate gas exchange: CO2 released and oxygen caught from air. Kidneys filtrate the blood to clear from many residues of metabolism. Given these circumstances, these organs are perfect to carry on with all the blood during its circulation.

Filtering but controlling what’s being filtered

However, what about if lungs fail to catch oxygen and this gas is reduced in blood. Which organ should control the signal? If this task is deferred to the brain the consequences may be deleterious for the entire body. Then, the best option is to give this duty to kidneys.

The kidney’s erithropoyetin

When kidneys sense that the blood being filtered is lacking oxygen, they cooperate recommending the creation of more red cells with enough Hemoglobin (Hb) to catch up oxygen from lungs. The renal cooperation is provided with an hormone called erithropoyetin which works at the bone marrow to induce the formation of red blood cells (RBC) that may be able to take oxygen and bring it to the tissues.

Erithocytosis: increased red blood cells

This situation may take some time (when kidneys consider that the lack of oxygen seems to be serious). The resultant condition is an increased level of RBC with high levels of Hb. This effect is called erithrocytosis, erithremia, polyglobulia, secondary polycytemia, and so forth. Blood turns into thick and slow during its circulation leading to some dizziness and headaches.

Cardiovascular effect of erithrocytosis

With this type of blood, the heart needs to work harder: how to push this heavy luggage? The condition may generate a bigger heart in terms of walls with less space to fill.

Lung diseases as responsible of erithrocytosis

Many lung illnesses are signaled by the presence of secondary erithrocytosis due to difficulties in allowing the access of oxygen to the blood. Advanced stages of COPD are presented with high levels of Hb and RBC and this indicates distant complications from the lungs. The Chronic Bronchitis phenotype (constant cough and sputum production) is classically accompanied with erithrocytosis and increased Hb.

Not a healthy feature

The key fact is that secondary erithrocytosis with high Hb is not a healthy feature when they are seen in an adequate context. COPD and its eventual lung decrease in oxygen catch leads to kidney to send signals that create a huge confusion in the body with a consequence as the one described.

Final point

It’s good to assess oxygen levels and blood samples to evaluate further the lung and kidney cooperation in many pulmonary diseases. And this is just one of several joined efforts of lungs and kidneys preserving our corporal functions.

Oxygen as indicator of lung disease

Importance of energy

Making our organs to work implies the transformation of energy from different instances. Each organ require a provition of nutrients to accomplish its functions. The most visible function is seen in muscles. Muscular actions are designed to help in life with almost every activity. Our muscles take a big part of nutrients and transform them into energy and subsequent physical actions.

Oxygen: a combustible

For the transformation of nutrients at celular muscular level, the combustible “gas” is Oxygen. It is brought to that level bound to Iron in Hemoglobin (Hb) of the red blood cells. Oxygen binds to iron in Hb at lungs where blood is exposed to oxygen. In the lungs, the thin barrier between blood and air is amazingly wide to allow this fuction.

Lung illness and oxygen change

Respiratory diseases affecting the surface for exchange will have an eventual impact in the take over of oxygen from atmospheric air. Acute and chronic conditions will (depending on their severity) reduce the healthy surface for exchange. The good news is that most of acute conditions will reverse or let minimal sequelae. Chronic conditions like extensive scaring, wide destruction of alveolar walls will manifest oxygen reduction in blood at some point of the course of the disease.

Reduced oxygen

Preserving the surface available for a healthy gas exchange provides with an adequate field for physical activities. Exercise requires, not only a healthy lung but also some physical (progressive training). Curiously, lung reserve for gas exchange is big and delay clinical manifestations of reduced blood oxygen (also called hypoxemia). When hypoxemia occurs something severe and serious may be happening and physical activities will be affected.

COPD and reduced oxygen

COPD is characterized by progressive destruction of alveolar walls as well as persistent bronchoconstriction that impedes air of leaving the alveoli. Under these circumstances oxygenated air can not reach the surface that allow access to blood and the surface that can be reached it’s already reduced.

What we can expect from COPD effects at some point of the disease development is hypoxemia. COPD patients with advanced disease will have their physical activities impacted due to hypoxemia especially when the energy requirements are increased (exercise).

Oxygen reduction in other lung diseases: a few examples

These effects may be seen during some asthma crisis. In a set of pulmonary disease called interstitial lung diseases the gas exchange surface is severely affected. In some cases of pneumonia the infectio may lead to pus accumulation in air spaces limiting air access into the lungs.

From Oxygen to where?

Oxygen measurement may be required in many respiratory symptoms assessments. If oxygen is reduced it may be necessary to consider levels of other gases like CO2 as well as levels of acidity. This is for having a more complete profile of the gas exchange and the responses of the body due to this effect.

Percussion of the Thorax during physical exam: some comments

An empty thorax?

Percussion of the thorax is a maneuver used by physicians to assess part of the integrity of lungs: their emptiness. As the lungs should be filled with air enough to be ventilated and proceed with the local gas exchange.

Lungs are like a huge sponge with a big difference from the typical ones: their dividing walls are full of blood and their spaces are full of air. The amount of air inside lungs is a big one: around 5 liters. Imagine 5 bottles of 1 liter each one inside the thorax and containing only air.

Just touching with two fingers

When percussion is performed hitting the tip of one middle finger on dorsal side of last joint in the other middle finger there is no special sound but some dullness. However, if the second finger is put over the thorax (not in the cardiac area) the sound is like the one on an empty box, similar to a drum, or the body of a guitar.

Some lung divisions

Lungs are composed by lobules (like having more than 2 sponges together). The right lung has 3 sponges together and the left has 2 and small one to give some space to the heart. The right has a big almost pyramidal that goes from the base of the thorax toward the whole back. Over its front there are the two other lobules: one bottom and other top. Here it was described right lung’s lobules: lower, middle, and upper.

For the purpose of this explanation, let’s avoid the left lung description.

Sonority vs dullness

The percussion of the thorax is normally sonorous (resonant). However, it’s not like an empty stomach but with some muffling (due to local blood circulation).

Some variety may be heard according to individuals. The resonance may be softer in an obese person than in the skinny. The expert will find normal sonority in each normal patient.

Changes in the back of right side of the thorax implies changes in the right lower lobe. In the front but bottom, percussion explores middle lobe while in the top front, it talks about upper right lobe.

Obvious changes of percussion in COPD

In COPD, the trapped air tend to increase the sonority of the thorax. It also happens in the symptomatic asthmatic as well as in other different circumstances. However, percussion of thorax is made with the purpose of looking for dullness like in pneumonia (when areas of the lung are filled with pus), pleural effusion (when the space between lung and rib cage is filled with more liquid that necessary to allow the breathing movement).

Granularities of COPD percussion

When a COPD patient has more emphysema than chronic bronchitis, the sonority by percussion is increased. It is also increased when the emphysema has led to creation of big bubbles called bullae. Its localized pattern may lead to clues about the severity of emphysema in precise areas.

A fact on percussion of the thorax

Percussion is a very helpful maneuver during physical exam of symptomatic respiratory patients. It completes the auscultation when it is abnormal. Not all patients will be explored with percussion but some of them may require this type of assessment when it’s necessary to confirm the excess presence of air, or a condition associated with dullness.

Don’t expect your general practitioner to do percussion in a routine manner. It’s just a confirmatory maneuver.