The first breaths
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UNBEARABLE PAIN MORPHS QUICKLY INTO UNTARNISHED JOY for most women upon the successful delivery of a healthy baby. After months of growing anticipation on mom's part and increasing self-assertion on the part of the gradually-developing tiny person, the intense suspense melts away the instant the naked bundle of human potential draws its first breath, opens its eyes, and becomes an independent, real live human being. What greater earthly gift could an all-loving heavenly Father give to His children than the opportunity to participate personally in the miracle of new life? Many obstetricians, believing and unbelieving, feel a sense of wonder at the act of birth right up to their last delivery.
For those willing to go a step further and give thought to the process of birth and new life, gratitude turns into humble worship; the astounding sequence of wondrous changes that turns a suspended fetus with fluid in its lungs into a squalling babe that breathes air invariably imparts a sense of awe in all who learn about it. Of special note is the remarkable feat performed by a newborn babe when it inhales its first breaths of life. For many of us, taking that first breath may be the biggest challenge we successfully meet in our entire lives!
The miracle of breathing
How often do we stop to ponder what's going on when we breathe? Yet the exquisite apparatus by which infants and adults extract oxygen from the air and excrete carbon dioxide into it continues to reveal exciting new Eureka moments to investigators in spite of the many years of intense studies and experiments that have been applied to the system. David praised God for the brilliant design of his own body:
I will praise You, for I am fearfully and wonderfully made; marvelous are Your works, and that my soul knows very well (Ps. 139:14).
Every second endless amazing activities are going on in your body — most at the molecular level —of which you are utterly unconscious and over which you have no direct control. Breathing is one of the few stupendous activities of which you can be aware.
Most adults breathe about twelve times per minute at rest (the normal range being anywhere between 10 and 20 times), sucking in about 500 ml of air — the equivalent of eleven liquor jiggers — each time. A little investigation reveals that an entire suite of anatomical and physiological design features, ranging from the microstructure and chemical lining of tiny alveoli to the large-scale anatomy of ribs, is needed to make the breathing machinery work effectively. Large-scale features, such as the shape and composition (and therefore elasticity) of ribs, the placement and power of respiratory muscles such as the diaphragm, and the properties of the pleural membranes (see below) work harmoniously together to provide suction pressure for inhalation and “blow” pressure for exhalation, while the microstructure of lung tissue and the properties of chemicals lining the microscopic airways are contrived to give easy passage of air to the lung's internal extremities and to keep delicate airways open.
Critical to absorption of oxygen are the alveoli, which are tiny air sacs that act as the primary gas exchange units between air and blood. Millions of alveoli make up the lungs — about 25 million at birth reaching some 85 million by the time the baby reaches three months and about 300-700 million by adulthood. Such a huge number contained in a small volume leads to a simple deduction — alveoli are not just tiny, they are microscopically small. You cannot see them with the naked eye; cut open a lung and you would see what appears to be almost solid matter yet it is, in fact, like an extremely fine-grained, delicate sponge.
Of lungs and balloons
To better understand what happens when we breathe, we need a little basic knowledge about those masterpieces of precision engineering, lungs and chests. From a mechanical perspective, the lungs are a kind of collapsible hollow cylinder located inside a rigid, potentially hollow object, the chest wall, of which the rib cage comprises the key component. Both lungs and rib cage share a property known as elastance, meaning they are naturally “sprung” to attain to a specific shape and size when no external forces act on them to either distend or compress them, and that they will tend to “spring back” to their default dimensions after being distorted in any way, just like an inflated balloon which rockets around the room after being let go as it elastically recoils to normal.
Unlike kitchen sponges, which automatically “bounce back” to an expanded state after being squeezed, lung sponge, consisting of a mesh of alveolar epithelia, capillaries, and elastic and collagenous fibers is sprung like a balloon so as to go the other way; its springiness is “negative”, meaning that it would completely collapse and squeeze all the air out if surgically removed from inside the thorax which holds them partially open.
Unlike lungs, ribs and attendant cartilage are beautifully and precisely designed to spring open a little, and thus draw in a little air. Paradoxically, in this respect they are more like a kitchen sponge than spongy lungs are!
Sprung just right
When breathing apparatus is totally relaxed it is said to be at rest. In the breathing cycle, relaxation occurs at the end of exhalation. At that moment the opposing forces — the “force of collapse” exerted by the lungs and the tendency of the chest wall to spring open — exactly balance each other; no muscles are working. At that point, both lungs and rib cage are under a degree of stress since neither is exactly the way it would like to be, neither is at default.
An obvious implication of this friendly antagonism is that some air will remain in the lungs after expiration; the tendency of the rib cage to expand prevents the lungs from squeezing all the air out. The volume of air that remains in your lungs after you have exhaled is known as the functional residual capacity (FRC). Life without this ever-present bank account of gas would be impossible. In addition to the critical function of keeping the airways propped open, the FRC makes some more mundane things possible, as one expert notes:
Without this air, eating, drinking, talking and other essential activities would be severely limited by the necessity of continuous breathing.
May we praise and thank our Creator for making us thus.
Mechanics of breathing
What mechanism causes air to enter and leave the lungs? As we have seen, lung tissue is like a sponge. Covering the sponge is a two-layered membrane known as the pleura, the two membranes (pleurae) being separated by a potential space. We can liken the entire setup to a sponge surrounded by two balloons, the one balloon inside the other. What sort of mechanism would you rig up to suck air into sponge-filled balloons? The answer lies in placing the sponge-balloons inside a rigid container, gluing or stitching the balloons to the inner walls of the container, and then contriving a means of making the container expand, pulling on the outer balloon which sets up suction in the gap separating it from the inner balloon, which pulls on the inner balloon which reduces pressure inside the sponge's air spaces and… well, you can imagine the rest. The ribs provide the required rigidity.
The force to expand the chest cavity is generated by the muscles of respiration. The workhorse muscle is the diaphragm, but it needs the assistance of other precision muscles to tug gently on other parts of the rib cage to harness the diaphragm's horsepower in such a way as to have the desired effect. By contrast with inhalation, the diaphragm and other respiratory muscles relax during exhalation when breathing at rest so that breathing out is passively caused by the elastic tendency of lung tissue to collapse.
Breathing in the newborn infant
Significant differences occur between infant and adult breathing phenomena which reflect underlying differences in their respective respiratory systems. Though such differences may come as no great surprise, they nevertheless attest to the wisdom and ingenuity of the Creator of all things, Who not only had to design the respiratory system of adults, but also had to ensure that the gradual changes on the way to maturity all matched the gradually changing needs of the individual.
These comments raise a fundamental truism about human development — the change from babyhood to adulthood involves much more than merely growing bigger. Critical developmental changes must occur in all bodily systems day by day. Lungs and chests don't just get bigger, they develop. The first days of life are the most critical. Millions of microscopically-narrow tunnels (bronchioles) must quickly “learn” to allow the efficient passage of air into the millions of alveoli which, having been charged with air in the first breaths, must then inflate and deflate in perfect harmony and rapid succession, a process known as ventilation. (Asthmatics don't take the ability of bronchioles to let air squeeze through them for granted.) Efficient ventilation takes a few days to establish. The supple chest wall, having been released from its fetal straitjacket, must stiffen ever so slightly to increase its recoil strength sufficient to force the lungs to hold on to a little air after exhaling. Regular breathing patterns must be established, and so on.
Sighing is a short-lived reflex in newborns. At least once every five minutes, a newborn “sighs”, that is, takes a deep breath that sucks in slightly more than double the normal breath intake. By the fifth day the incidence of sighing has dropped in most infants, but still occurs periodically (see graph below). Detailed study has shown that what appears to be one continuous, prolonged intake of air actually consists of a normal breath, interrupted momentarily by a pause or even a very slight exhalation followed by a second, bigger renewed inspiratory flow often called a “gasp”. This phenomenon is called a “breath on top of a breath”. The second gasp is initiated by a reflex that is activated when, for reasons that seem unclear, the first breath is ever so slightly larger or faster than normal. The subtle deviation from normal of the first breath triggers the next intake. The changed first breath may be caused by a response in the central nervous system to changes in blood chemistry, perhaps related to levels of oxygen or carbon dioxide in the blood.
Of considerable interest to respiratory experts is the purpose of sighing in infants. They recognize that it doesn't just happen because it just happens. Many ideas have been proposed. Some suspect that it plays a role in maintaining the vital suppleness (preserving compliance) of the lungs. A recent study suggests that sighs, “… play an important role in resetting the mechanical properties of the lung tissue and airway walls”. Still others believe it plays a role in solving the potential problem of lung collapse by blasting open isolated segments that get blocked. Keeping the staggering labyrinth of airways open and allowing air to move around evenly requires brilliant innovations; sighing is probably one of them. In short, sighing appears to play a number of vital roles; experts are still busily at work discovering new things about a seemingly incidental feature of breathing in babies.
The first breath
Of all the amazing post-natal events that occur over the course of a few days, the gold medal for sheer drama must go to the act of taking the very first breath. At the moment of birth, a newborn infant doesn't have a molecule of gas in her lungs. The airways are filled with a small amount of fluid containing a vital wetting agent that is pumped into the lungs before birth by means of hydraulic pressure.
The first breath, then, must overcome huge obstacles. First, you have the natural resistance posed by the narrowness of the airways in the tiny lungs. Illustrating this problem is easy enough. Open your mouth wide and suck in a lungful. Now put a straw in your mouth and try to do the same thing. Smaller passageways mean more resistance to the flow of air. That we adults can breathe is marvelous enough — that a tiny package of new life can do so for the first time should be enough to blow us away. Researchers have found that even more resistance (about 70% of the total) comes from the peculiar elastic properties of alveoli and airways and the liquid lining them.
But there is more. Imagine the straws just mentioned were filled with water — the resistance to drawing in air makes the task so much harder. Further, the first breath meets resistance from the tissues of the lungs themselves. In sum, for a newborn, “the pressure required to inhale is very large”. Yet as a newborn baby, because of the planning and preparation of your Maker, you succeeded in pushing that fluid in your airways out of the way in that very first breath!
For this first inspiration of air, the diaphragm, assisted by upper airway muscles, marshals all its resources to make one Herculean effort. Though its action may be assisted by a swallowing action of the tongue and throat resembling the forced swallowing breathing of a frog, the evidence supports the contention that almost all the air that enters the lungs in the first breath does so through the contraction of the respiratory muscles. As the first breathing movement begins air begins to enter the pharynx, and then, a third of a second later, a considerable amount of air reaches the lungs. The resistance the air meets from surface tension at the air-liquid interface as it passes into the deepest portions of the lungs, the bronchioles and alveoli, is considerably offset by the natural wetting agent mentioned above. When they have received all the air the newborn can force in, the diaphragm relaxes and the first exhalation occurs. The very first breath succeeds in stocking the lungs with a small amount of residual air; never again will they be completely empty. Many more breaths are required to ventilate all the internal airways and alveoli evenly. But never again will as much effort be required as was necessary for that first breath.
When one has some grasp of the sophistication of design of the human breathing apparatus, and what it takes to activate the first breath after birth, the allusion to breath in Isaiah 42:5 takes on a whole new meaning:
Thus says God the Lord, Who created the heavens and stretched them out, Who spread forth the earth and that which comes from it, Who gives breath to the people on it, and spirit to those who walk on it…
Those tiny bundles aren't just cute, cuddly and adorable; they sing the praises of the Father and Jesus Christ Who not only care passionately for each one — even more than her mother does — but Who spared no effort to ensure that they can conquer the mile-high hurdles confronting them when they emerge into their wondrous new world of adventure and excitement.
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