Chapter 18- Mechanics of Breathing

Pathway of Air through the Airway

Mouth/Nasal Cavity, pharynx, larynx, trachea, primary bronchi, broncheoles, alveoli

Difference between pulmonary structures and cardiovascular structures

pulmonary tract has less resistance and lower overall pressure due to being a shorter circuit

pleural fluid purpose

lowers friction between membranes, holds lungs against thoracic wall

What is negative pressure breathing?

muscle contraction expands the internal volume of the lungs, creating a vaccuum and dropping the internal pressure, drawing air into the lungs

What is physiologically different in people with cystic fibrosis?

chloride transporters are defective, leading to thickened mucus that gets stuck in the respiratory tract

pulonary edema

fluid buildup between alveoli and capillaries increases the diffusion difference and repulses O2, lowering the diffusion rate

type 1 alveolar cells

facilitate gas exchange

type 2 alveolar cells

produce surfactant

purpose of surfactant

keeps alveoli from collapsing by decreasing the surface tension of the water molecules within them

consequence of the absence of surfactant

lungs will collapse since the alveoli cannot maintain their structure

Dalton’s Law

total pressure equals the sum of all partial pressures

what percent of atmospheric air is oxygen?

21%

Boyle’s Law

P1V1=P2V2

Concentration of a gas is the same as its

partial pressure

calculate the partial pressure of oxygen in standard temperature (25*C) air with 100% humidity

(Patm-P H2O)* %gas: (760-24)*.21= ~155 mmHG

directionality of moving gasses

higher to lower pressure

tidal volume (VT)

volume that moves during one respiratory cycle (ave 500mL)

inspiratory reserve volume (IRV)

additional volume above tidal volumee (ave 3000mL)

expiratory reserve volume (ERV)

forcefully exhaled after the end of a normal expiration (ave 1100mL)

residual volume (RV)

volume of air in the respiratory system after maximal exhalation; always in the lungs to prevent them from collapsing (ave 1200mL)

vital capacity (VC)

only calculated; IRV+ERV+VT; measures how much functional air is available to the body on one breath

total lung capacity (TLC)

only calculated; IRV+ERV+VT+RV; all the possible air the lungs can hold

what type of breathing is quiet breathing?

passive

when are the two types the body is active breathing

coughing, exercising (raised breathing rate)

difference between active and passive breathing

active breathing utilizes the abs and obliques

passive breathing

breathing out is the relaxation of muscles and the end of an action potential; the elastic capacity of the lungs pushes air out

active breathing

internal intercostals and abdominal muscles contract to push air out of the lungs; raises the vital capacity

normal intrapleural pressure, in comparison to the atmosphere

negative, around -3 mm Hg

Pneumothorax

damage to pleural membrane causes pressure in intrapleural space to be the same as atmospheric pressure, causing a “collapsed lung”, or volume falls to minimum possible because of the lung’s natural elasticity; extra internal air pushes organs away from the site of damage

compliance

the lung’s ability to stretchhig

high compliance

easy stretch and expand- think walmart bag

low compliance

requires more force to inflate- think latex balloon; the cause of restrictive lung disease

eslasticity

ability for the lungs to return to a resting volume when stretching force is released

negative pressure breathing

pull air into the systemp

positive pressure breathing

push air into the system; think CPAP machine

makeup of surfactants

mixture of proteins and phospholipids

effect of resistance on an airway

higher resistance, lower flow; inversely proportional

bronchoconstriction

making diameter of the airways smaller; triggered by histamine

bronchodilation

making the diameter of the airways larger; triggered by epinephrine

anatomical deadspace

parts of the airway that does not facilitate gas exchange- trachea, bronchioli, bronchioles (ave 150mL)

Eupnea

normal quiet breathing

hyperpnea

increased respiratory rate and/or volume IN RESPONSE to increased metabolism

hyperventilation

increased respiratory rate and/or volume WITHOUT increased metabolism

hypoventilation

decreased alveolar ventilation (shallow breathing)

tachypnea

rapid breathing; usually increased respiratory rate with decreased depth (panting)

dyspnea

difficulty breathing as a subjective feeling, described as “air hunger”a

apnea

cessation of breathing

prefix eup-

real or authentic

suffix -pnea

breath or breathing

normal total pulmonary ventilation

6 L/mint

normal total alveolar ventilation

4.2 L/min

normal max voluntary ventilation

125-170 L/min

normal respiration rate

12-20 breaths/min

Obstructive Lung Disease

increase in airway resistance; asthma, obstructive sleep apnea, emphysema, COPD

Restrictive Lung Disease

reduced lung compliance (no lung stretching), increased resistance in the lungs; pulmonary fibrosis (scare tissue from smoking, cancer, TB), scoliosis (misshapen spine- smaller volume of thoracic cavity)

forced vital capacity (FVC)

taking in as much air as possible and breathing it out as quickly as possible

FEV1

forced exhalatory volume after one second

FEV1/FVC ratio

distinguishes obstructive and restrictive lung disease

FEV1/FVC ratio in restrictive lung disease

does not change; both values decrease

FEV1/FVC ratio

decreases because the top volume decreases; less than 80%

phrenic nerve

sends signals that cause the diaphragm to expan and contract allowing the lungs to inhale and exale air