6.(20-22) Respiratory Tracts, Lungs/Asthm*a/COPD

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Includes Chapters 20 to 22 on Lungs & Air Quality - Scroll down for.

20.Respiratory Tract (RT) – Upper and Lower - Update 22 Aug. 2021 all chapters

The Respiratory Tract, or airway(s), starts at opening of nostrils and mouth, diverges from the food-tube at larynx; and as the upper airways is the trachea and larger bronchi (singular bronchus); then as lower airways it is the smaller bronchial tubes and terminal bronchioles; and ends in micro airways, or alveoli.

Below, the Terminal Bronchioles and Alveolar Air Sacs

The adult human trachea is 25 cm (c.10 in.) length and 2.5 cm (c.1 in.) diameter and gets rigidity by 15 to 20 cartilage rings, with open part facing rear, bridged by muscle. You can feel upper trachea by pressing into bony notch in lower neck front. Trachea divides into right main and left main bronchi and progressively smaller bronchi. Cartilage support continues until smallest bronchi. Small bronchi spasm causes asthma. The terminal bronchioles lack muscle. Each one serves as entry/exit for 3 or 4 Alveolar Ducts, and each duct ventilates 10 alveolar sacs from which oxygen is absorbed by the red blood cells and into which carbon dioxide is released for exhalation to outer air.

   Problems for the Respiratory Tract are constriction and obstruction. It is a mucous membrane exposed to infection and cancer-causing influence from air. And it is the source of troublesome cough and other breathing symptoms from airway hypersensitivity to irritants and from allergies. The epiglottis at base of tongue serves as a plug contra  windpipe entrance when food passes down from mouth and we use the epiglottis voluntarily to hold our breath against forced expiration in straining to push out constipated feces. (And also can be used to prevent ourselves from breathing-in toxic fumes or water in emergency for short periods.)

   Concerning foreign body obstruction (piece of food) at entrance to trachea, even if you do not know the Heimlich maneuver (Encircle the choking person’s body from behind with each of your arms with fist grinding into the choking person’s solar plexus and make sharp, jerking pressing motions), realize that the stuck particle may be dislodged by any increase in abdominal or thoracic pressure. If it happens to you, bend upper body and with head down, make powerful coughs repeatedly and try to vomit. Moderate blows to upper back with head down may also dislodge.

   The bronchial tract is of interest as cause of asthma due to bronchial constriction. The stress hormone epinephrine (adrenaline) relaxes the bronchial tubes and bronchioles and widens them, so increased epinephrine is good against asthma and good for easy breathing. Oppositely, acetylcholine, the neurotransmitter of the parasympathetic nerves, constricts bronchi and worsens asthma. Non selective beta-blocker-1 medication like Inderal (propranolol) by opposing the bronchus relaxation of epinephrine is pro-asthma and the parasympathetic blocker atropine, by opposing the bronchus constriction of acetylcholine, relieves asthma attack. Epinephrine injection is used to treat asthma attack. A natural, home treatment for asthma attack is to take a shockingly cold and then tolerably hot shower. In addition to flooding your system with epinephrine, it makes breathing easier by moisturizing air and thereby reducing friction of air passing back and forth in respiratory tract.

   Points to keep aware of: 1) Histamine, the neurotransmitter of allergy and hypersensitivity is bronchus constrictor so an antihistamine, given quickly in allergic asthma may neutralize histamine’s asthma-effect. 2) Aspirin and NSAID, by pushing prostaglandin into the lipooxygenase pathway each produces asthma-causing leukotriene and in 10%, can provoke asthma attack and in many more will worsen it.

Chronic Obstructive Pulmonary Disease (COPD) afflicts old age: it results from air pollution led by smoking. The COPD includes bronchial asthma, and causes right-side heart disease. This is the oldster you see in wheelchair holding gas can and with tube in nose for oxygen. Avoid that fate by paying attention to keeping breathed air clean and free of pollutants especially tobacco.

   Useful data for COPD is its relation to “Forced Expiratory Ventilation in the first second” (FEV₁), the volume of breathed-in air in milliliters (mL) you can exhale in the first second after taking maximal inhalation and exhaling forcefully. It is measured by the spirometer that ought to be available in hospital or pulmonary specialist office. The FEV₁ test number shows in liters per second (L/s): 4 L/s is normal, 2 to 3 L/s is mildly weak, 1 to 2 L/s is moderately weak and <1 L/s is severe case. Even without the test, a try at estimation is useful. If you have normal heart and lungs, you ought be able to walk 5 miles in 1 to 2 hours at top speed (4 mph is very fast walk). As you find you are getting worse, you can judge your need to get a cardiovascular, respiratory and anemia check up. If there is discordance (i.e., you note severe exercise intolerance yet your FEV₁ is more than 3 L/s), it means your symptom is not due to COPD but may be caused by intrinsic lung disease, heart failure, or anemia or chemical blood poisoning interfering with respiration. The FEV₁ is the test for one who questions his lung capacity for sustained exercise as when going into an exercise program, because it is sensitive enough to pick up early worsening COPD in absence of symptom and therefore can head off trouble. Non-smoker respiratory deterioration shows by a decrease in FEV₁ at rate of 30 to 40 mL/year (1000 ml = 1 L) with aging. In a smoker, this rate of decline can worsen 4 times that of nonsmoker.

 A shortcut to an important test of respiratory function, The Vital Capacity (VC), is the maximum volume of air you can expel from lungs after a most deep inspiration. Do it now – breathe in maximally, hold for a few seconds, then start counting and allow breathing out. (You should be counting at a normal rapid count like 1, 2,, 3, etc.) The highest number you can count before you are forced to take your next breath multiplied by 100 gives your VC. My VC right now took a 1 to 51 count so I estimate my VC as 5.1 liters or 5100 ml. It is normal. A low VC is typical in COPD and also found in lung destructive diseases or after lung surgery.

21. The Lungs and Healthy Longevity

Most important for Healthy Longevity is to keep an edge in favor of the purity of your breathed air: No smoking (tobacco, marijuana, cocaine), no closed space with heater, and use surgical mask if small particulates in your air (powder soap, hayloft, cleaning where dust abounds) or a high probability of infectious germ (winter coughing, sneezing persons, today Covid-19 risk). In ideal world, you want to live where air is cleanest of pollutant.

   Cultivate a lifetime habit of keeping mouth shut and breathing by nostrils - a natural filter against pollutant.

Also cultivate preference for fresh air over air-conditioned, or heated or cooled air. So in summer, at home where appropriate, go naked instead of using a cooler and in winter wear warm clothing and no use of heater/aircon if you can manage that. 

   If apartment dweller, the higher up the better, purer, cleaner air. (Radioactive odorless radon gas is mostly in basements.)

The lungs, protected from air pollution, are surprisingly problem-free.

   Get immunized against pneumococcus (pneumovax) and hemophilus influenzae bacteria at 5 year interval from age 65, and every year in October get the latest flu vaccine. And, of course, ASAP, get your Covid-19 shots.

   With important respiratory ills (asthma, blood cough up, lung tumor) initially consult respiratory/lung specialist at top medical institution even if it means traveling and going without insurance benefit.

22. The Lungs and Respiration
   Chapter also contains useful scroll down or search & find headings in order of reading:  

Pleural Hole and Pneumothorax

Low Atmospheric Pressure Disease

Respiratory Tract Air Flow Resistance Lowering

Top: left lung, lateral view and medial view. In lateral view on your left, the obliquely diagonal line from top rear to bottom front of lung is the lobar fissure that divides the frontward-facing left upper lobe from the backward-facing left lower lobe. Note how front upper lobe is obliquely stacked on lower lobe, which acts as its diagonal partial base.

Bottom: right lung, lateral view  and medial view. In lateral view on your left the obliquely lateral front-back lobar fissure line  is almost bisected  by a nearly horizontal anteriorly running line making for the 3-lobe division of right lung - right upper lobe, right middle lobe and right lower lobe.  (The front-back body direction of the lungs are reversed compared to views of left lung)

   The jigsaw-puzzle-like lines divide the lungs into small sublobar segments. Note in both lungs the apical upper segments. These are the most frequent sites of tuberculosis cavity and also of bronchiectasis in cystic fibrosis, owing to their poorer ventilation and lesser amount of blood they receive due to gravity on the blood circulation when standing and due to poor drainage. The opposite effect is seen in patient with mitral stenosis (Narrowing of heart valve from left atrium to ventricle). TB of upper lungs is not seen with mitral stenosis because of the mitral-stenosis-induced increased blood flow in upper lungs.

   Note the medial views of both lungs shown in figures on your right side. These are views as if you could separate the right and left lungs at center of body and look at each lung in the cut body’s mid-vertical plane. The respiratory tract system of bronchial tubes can be seen at the root of each lung with main left and right bronchus each cut at right angle. The heart and great vessels normally fit in a frontward indentation between the two medial sides of the lungs.

   The bases, or bottoms of the lungs show the dome-like indentation where the diaphragm muscle separates the thorax chest cavity with the lungs above from the peritoneal abdominal cavity with its organs below. 

In looking at the lungs in the above figures, keep in mind that in actual life the lungs in a chest are spongy elastic organs that, during an inhalation will expand like spongy balloons taking the shape of the inner thorax and that at exhalation will collapse by elastic recoil to smaller size, greater compactness, and less shaped.

   Also, in describing breathing it is important to keep aware that each lung is enclosed in an air-sealed cavity whose volume is controlled by the bony thorax shown in the Figure below:

The bony thorax viewed from front. Note the rib pairs that enclose the thorax can be numbered right or left, 1 to 10 from above down, and also the floating 11^th and 12^th ribs behind (Not obvious in the figure). The transition between the bony and the cartilage part of each rib is seen in the darker cartilage in front. Most rib fractures involve the ribs on the sides. Note the center breast bone, or sternum, with its lower xiphoid bone attachment that you can easily feel beneath your breastbone. It often gets fractured during CPR (cardiopulmonary resuscitation) chest compression. Also note the posterior connecting backbone or vertebrae (Mostly hidden in the figure) which are all the 12 thoracic vertebrae and numbered T1, T2, …(Alternatively, D for dorsal;  D1, D2. ...) based on the rib each connects with.

In a living body the bottom of the thorax is closed off by the domed diaphragm, a voluntary muscle that singers and sports professionals get trained to use well. Spaces between the ribs are closed off by muscles and may be narrowed by the muscles' contraction. 

The act of breathing-in (inhalation) is dependent on the difference in air pressure between the negative pressure pleural cavity (space between the outer surface of the lungs and the inner surface of the thorax) and the outer atmosphere when there is an unobstructed respiratory tract that transmits the atmospheric pressure to all air sacs inside the lungs. When we decide to take a normal-effort breath, we voluntarily contract the muscles connecting to our ribs and our diaphragm. The muscles increase the pleural cavity thorax volume by widening the front to back, the side to side and the up to down of the thorax cavity and creating negative pressure in the pleural cavity. The elastic lungs immediately start to stretch to fill the negative pressure space, and air is pulled into the mouth and nostrils, down the throat and into the trachea and bronchi to all the air sacs in both lungs, and the lungs expand. It may seem to us that we actually “take a breath” in the sense of consciously sucking in air but what actually is happening is that the multiple-muscles coordinated activity from upper chest to abdomen creates the breathing motion. In case we need to increase the depth of our breathing, then the accessory muscles of respiration in neck can further increase the negative pressure and the depth of breathing. If you will watch an athlete at the extremes of exercise you will see the muscles from his neck tensing and relaxing with each breath.

   So that is breathing-in! What about breathing-out, expiration or exhalation?

   In contrast to the positive action of breathing-in, the normal-effort exhalation is just a relaxing of the muscles and letting elastic recoil take care of squeezing the inspired air from the lungs and out the mouth and nostrils. When an inspiration is ended, we voluntarily stop contracting the muscles and they relax. The thorax has been expanded by the muscles of inspiration and, when the muscles relax, the thorax gets smaller in volume. By its own elastic inward recoil pull it assumes the smaller space it occupied before, increasing the pressure inside the pleural cavity. Then, the lungs collapse in elastic recoil and shoot the previously breathed-in air out the mouth and nostrils. In heavy exercise, when we need to breathe rapidly, we may assist and speed the exhaling by tightening our upper abdominal muscles so as to push the diaphragm more rapidly up into the chest and get the air out quicker.

   Bad for breathing is a low air pressure (living by Lake Titicaca in Peru atmospheric pressure is 1/2 of sea-level), a high external water pressure on the chest (deep scuba diving – each 33 feet adds 1 atmosphere pressure on chest to be overcome in breathing), or a respiratory tract obstruction.(Aspiration of piece of food into windpipe in a restaurant from eating too quickly) Also, as in bronchial asthma, bronchial constriction and in emphysema, loss of lung elasticity.

   Good for breathing is air high pressure (high-pressure mask breathing), low pressure on chest wall only (iron lung respirator used for polio victim, now obsolete), and low airway-resistance. (Maximally reduced respiratory tract resistance to airflow is done by moisturizing breathed-in air, by use of broncho-dilating medicine, or, in emergency, by making a breathing hole in the trachea as tracheotomy)

Pleural Hole and Pneumothorax: Any event that allows air into the pleural cavity is a potential catastrophe. Most commonly it is result of a strong cough that bursts a small surface bleb-bubble on a lung surface and produces pneumothorax, collapsing the lung on that side. In bilateral (right and left) pneumothorax, death is quick because both lungs collapse and cannot expand. With the more usual partial pneumothorax a person may notice shortness of breath and pain after cough and will do OK while getting to emergency where a chest x-ray will confirm the pneumothorax and a chest tube inserted between ribs into the pleural space and giving 24-hr suction will allow the hole in the pleura to seal. It is most common in young men on commercial aircraft that are changing altitude rapidly.

   Another type of pleural hole is external from knife stab or bullet in chest. Immediately there may be sucking sound and the person gets short of breath. Lifesaving is to slap flat of hand tightly against the external wound, sealing it off from air while helper calls for medical assistance. A tight elastic bandage or plaster tape is temporary and life saving.

Low Atmospheric Pressure Disease: At sea level the pressure of oxygen (P_O2) is 160 mm Hg; but drops to 100 mm Hg ascending to altitude 10,000 feet and down to 80 mm Hg at 14,000 feet. (Highest ascent for usual tourist in Rocky Mountains or Peru Andes or Nepal Himalayas) The oxygen content of the arterial blood does not drop significantly until above 10,000 feet (3,048 meters). At that altitude some individuals will show impairment in memory, judgment and ability to calculate on testing. At 13,000 feet (nearly so for Lake Titicaca in Peru Andes Mountains and high in USA Rocky Mtns) un-acclimatized individuals develop convulsion, loss of consciousness, delirium; pulmonary edema. Exposure to high altitude occurs most commonly (but people are least aware of it) on commercial intercontinental jet where, while aircraft aloft at 35,000 feet, the cabin pressure is like at 8,000 feet altitude. Regulations require that flight crew use oxygen mask when cabin pressure drops to the equivalent of being at 10,000 feet altitude and passengers receive it at equivalent of 15,000. Most persons tolerate atmospheric oxygen equivalents up to 10,000 feet altitude well as long they do not exercise. But subtle brain function may be affected even at altitude as little as 1 mile (5,280 feet) high (Denver Colorado). So if you have choice to take your college SAT test, choose Seattle over Denver.

Respiratory Tract Air Flow Resistance Lowering: A long-distance runner wants to minimize air flow resistance along respiratory tract. First, is to be well hydrated because a moist mucous membrane has least air resistance; second, is to have some broncho-dilator substance (theophylline from tea) and no broncho-constrictor substance (as you might get taking Inderal, aspirin or NSAIDs - No-No’s for a runner); third is to keep slightly open mouth while running; and fourth is to not have restraining garment around thorax, abdomen or neck.

End of Section with Chapters 20 to 22. To read next now, click 6.23 Cough, Short of Breath, Wheezing,Cough Blood...

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