Purpose of breathing

 Purpose of breathing

Breathing brings in oxygen necessary for cellular respiration and eliminates the resulting carbon dioxide. If oxygen supply does not meet demand, desperate cells revert to anaerobic metabolism, resulting in lactic acidosis.1 Our oxygen requirement depends on the metabolic rate, but for a resting individual 3 mL O2/kg/min, should suffice. Meanwhile, we generate CO2 at a rate dependent on the respiratory quotient “R:”


where V˙C O2 and V˙O2 are the minute production of carbon dioxide and consump-tion of oxygen, respectively. R depends on the energy source (carbohydrates, proteins, fat). R approaches 1 in several conditions including pregnancy and patients on total peripheral nutrition (TPN), but we usually peg it at 0.8.

Comments

Post a Comment

Popular posts from this blog

Anesthesia and the lung

  Anesthesia and the lung And the Lord God formed man from the dust of the ground and breathed into his nostrils the breath of life; and man became a living soul  (Genesis 2;7) The concept of breath and soul reverberates through many languages in which spirit and breath share overlapping meanings. For example, in English, to  inspire  can have a physiological or psychological connotation, while to  expire  can mean nothing more than to exhale, or it can describe the moment when your spirit leaves you with your last breath. In anesthesia, we deal with both; on the one hand, the breath that needs to be provided for patients who cannot breathe by themselves and, on the other hand, the spirit – in a larger sense – which we subdue with drugs. Small wonder, then, that the linkage of breath and life gives us awesome responsibilities. In our practice no function is more important than ventilation, and no organ more integral to our practice than the lungs. Failure o...
Read more

Pre-operative evaluation - Clinical management

Image
  Pre-operative evaluation Surgery and anesthesia cause major perturbations to a patient’s homeostasis. The risk of potentially life-threatening complications can be reduced with appropriate pre-operative evaluation and therapy. Because cost concerns have virtually elim-inated pre-operative hospital admission, today the visit may occur just moments before the operation in the case of an emergency or a healthy outpatient, but is better managed in pre-anesthesia clinics to which patients report one or several days before their operation. Surgeons and primary-care physicians can do much to avoid operative delays and cancellations, as well as to reduce the patient’s cost and risk by identifying patients who need a pre-operative anesthesia consulta-tion and by sending all pertinent information, e.g., recent ECG, echo studies, etc., with the patient. The pre-anesthetic evaluation appears to be just another rou-tine of eliciting a history, reviewing all systems, performing a physical exam...
Read more

Single-valve system with gas storage - The anesthesia machine

Image
  Single-valve system with gas storage In order to save gas, we can provide for storage of the gas. Well known is the Mapleson system, often used during resuscitation and during transport of a  patient who requires mechanical ventilation.   The system shown in Fig.  8.3 is properly called a Mapleson  D  (as there are different arrangements lettered A through F). Figure  8.4 shows the real thing. It is light and deceptively simple. To prevent rebreathing of exhaled carbon dioxide requires a relatively high fresh gas flow, both to meet inspiratory demand and to wash exhaled CO 2  out of the tubing. Here, the excess gas escapes through an adjustable one-way (pop-off ) valve that prevents entrainment of room air. The pressure required to open the spring-loaded valve can be varied, enabling us to generate enough pressure (by squeezing the bag) to inflate the patient’s lungs. Slow respiratory rates help because, during a long pause between inspirat...
Read more