CO2/Air Flow

is O₂ or CO₂ the bigger driver of respiration

CO₂; very important for the body to get rid of this

___________ is used synonymously w getting rid of CO₂

ventilation

what are some factors (5) that can increase the body’s CO₂ production

• exercise

• fever

• eating

• seizures

• hyperthyroidism

what are some factors (4) that can dec the body’s CO₂ production

• malnutrition

• hypotherimia

• antipyretic therapy

• neuromuscular blockade

what are the three means that CO₂ is carried in the blood, rank them by % of total CO₂ transport

conversion to bicarbonate 90% > dissolved in blood 6% > bound to Hb (carbamino) 4%

where does the conversion of CO₂ to bicarbonate (HCO₃^-) take place, by what enzyme

mostly in RBC via carbonic anhydrase

what is the Haldane effect

higher % of oxygen binding to Hb dec the ability/affinity of Hb to carry CO₂ as carbamino groups

what is the Bohr effect

higher % of CO₂ binding to Hb dec the ability/affinity of Hb to carry O₂

what is the Haldane-Bohr effect

these effects work together to onload and offload oxygen and carbon dioxide in the the lungs/tissues

describe the Haldane-Bohr effect in the lungs

Haldane: onloading O₂ to dec Hb affinity for CO₂

Bohr: offload CO₂ to inc Hb affinity for O₂

describe the Haldane-Bohr effect in the tissues

Haldane: offload O₂ to inc Hb affinity for CO₂

Bohr: onload CO₂ to dec Hb affinity for O₂

what is minute ventilation

the volume of gas exhaled per minute

what are the two variables that determine the minute ventilation

• the volume of gas exhaled per breath (tidal volume; V_T)

• the number of breaths per minute (frequency/respiratory rate; f)

what can inc minute ventilation (6)

• anxiety

• pain

• hypoxemia

• pregnancy

• liver disease

• metabolic acidosis

what can dec minute ventilation (4)

• opiate pain meds

• altered mental status

• neuromuscular weakness

• metabolic alkalosis

you might expect all the minute ventilation to be devoted to gas exchange in alveoli, but not all of it does! what are the two compartments that add up to minute ventilation

• dead space ventilation (V_D)

• alveolar ventilation (V_A)

what is dead space ventilation

areas that are receiving ventilation but there is no perfusion/blood flow in the area→ cannot participate in gas exchange

what are the two types of dead space

anatomic and alveolar dead space

what is anatomic dead space, give an ex

part of the ventilation is left behind in the conducting airways and does not make it to the alveoli to participate in gas exchange; conducting zone

what is alveolar dead space, give an ex

alveoli are ventilated but are not getting an perfusion to the area; pulmonary embolism

the sum of the anatomic and alveolar dead space =

physiologic dead space

what effect will an inc of dead space fraction have on minute ventilation

will also inc in trying to maintain alveolar ventilation

what effect will an inc minute ventilation and constant dead space have on alveolar ventilation

V_A will inc

if minute ventilation dec and the dead space fraction is constant what effect will this have on alveolar ventilation

V_A will dec

alterations in P_aCO₂ are due to changes in the balance of…

CO₂ production and V_A ; V_A is affected by V_E and V_D

in a person who has a respiratory rate of 6 (normal is 12-20) how does this affect their P_aCO₂

They are taking shallow breaths (low tidal volume) at a low rate → their tidal volume will dec→ this ultimately inc the volume of the anatomic dead space → V_A dec and VCO₂ is constant →P_aCO₂ will increase

in a person who is appearing nervous and diaphoretic (sweating) and breathing deeply at a respiratory rate of 20, how does this affect their P_aCO₂

This patient is taking deep breaths→ meaning the tidal volume is large and the anatomic dead space volume is relatively fixed→ the V_A goes up and VCO₂ is fixed → P_aCO₂ will decrease

define hypoventilation

the level of alveolar ventilation is insufficient for your metabolic needs; high P_ACO₂ and P_aCO₂ (>40 mmHg) but low P_AO₂

define hyperventilation

the level of alveolar ventilation is too much (in excess) for your metabolic needs; low P_ACO₂ and P_aCO₂ (>40 mmHg) and high P_AO₂

the _____________ is the center for respiration and it is driven by ____________ and NOT by ___________

brainstem; driven by P_aCO₂ and NOT by P_aO₂

how do we get air to come into the alveoli

negative pressure

how is negative pressure created

happens during inhalation when the diaphragm flattens and pushes against its surrounding structures, stretched everything around it to increase the volume → this decreases pressure that will cause the negative pressure

specifically, what are the two mechanisms that the diaphragm uses to cause the volume of the thorax to inc

1. inc intra-abdominal pressure → pushes against the lower rib cage in the “zone of apposition”

2. lifts the rib margins up and outward

how are the lungs connected to the chest wall

the pleural space

what muscles are needed for inhalation, put asterisks (*) by the ones that are the most essential

diaphragm*, external intercostals*, scalene, sternocleidomastoid

what accessory muscles are used for forced inhalation

SCM, pectoralis major and minor, serratus anterior, latissimus dorsi

exhalation during quite breathing is entirely a ____________ (passive/active) process, therefore, there is _________ (no active/active) contraction of muscles

passive; no active

what muscles are used for tidal exhalation

none

what muscles are used for forced exhalation

internal intercostals, rectus abdominus, internal/external obliques, transverse thoracis/abdominis

what are the factors that most affect resistance (3), put an asterisk by the factor that affects resistance most

caliber*, length, and viscosity

what is caliber in Poiseulle’s Law

radius of the airway

what are the three main factors that can affect caliber

bronchoconstriction, edema (inflammation), airway secretions (mucous)

what are two other factors (aside from constriction, secretions, inflammation) that can affect caliber, explain

lung volume: more tethering inc the radius

pattern of flow: turbulent flow requires higher driving pressure→ dec radius

why does the volume of the lung impact the resistance in the airways

as lung volume inc, airway resistance decreases due to radial traction (tethering) from surrounding alveoli; the alveoli pull on the small airways making them wider thus reducing resistance (and you can think about it vise versa if there is dec lung volume → less alveolar tethering → inc airway resistance)

what is functional residual capacity

the resting volume of the respiratory system

FRC is determined by…

the balance of inward recoil of the lung and the outward recoil of the chest wall

A

TV- tidal volume

B

FRC- functional residual capacity

C

RV- residual volume

D

TLC- total lung capacity

what two factors contribute to the work of breathing

resistance and compliance

what is compliance

refers to how easily the lungs/chest respond to pressure

what are the three factors of compliance

lung parenchyma, pleural space, chest wall/abdomen

if there is a loss of lung tissue (general ex: emphysema), how does this affect FRC and compliance

there would be less elastic recoil meaning the lungs wouldn’t “snap back” as much leading to air trapping and a higher resting lung volume → inc FRC and compliance

if there is excess lung tissue (fibrosis), how does this affect FRC

there would be inc elastic recoil causing the lungs to collapse more therefore reducing the amount of air left after exhalation → dec FRC and compliance

what is transmural pressure

refers to the pressure difference across any hollow structure’s wall (inside pressure - outside pressure)

what is transpulmonary pressure

is a specific type of transmural pressure but applied to the lungs

the greater the distension away from resting volume (the more you blow the balloon up) the ________ (higher/lower) the transmural pressure

higher

FRC is determined by the balance of…

the inward recoil of the lung and the outward recoil of the chest wall

what is surfactant and how does this help alveoli

it dec surface tension in alveoli → dec tendency for alveoli to collapse → this overall inc compliance

what cells produce surfactant

type II pneumocytes

a patient w a fast respiratory rate is referred to as…

tachypneic

ventilation describes the ____ status, NOT the ___________

PCO₂; respiratory rate

is pt presents w shortness of breath, fever, chills, and hypoxemia and it not responding well to supplemental oxygen, what is the likely cause

pneumonia; most common is viral but also can be bacterial Strep

what is the purpose of a ventilator

allows us to control many aspects of breathing that a fatigued and ill person cannot control by changing the TV, RR, and F_IO₂ concentration

in a pt w pneumonia, this acts as a dead space, why

because the sick alveoli cannot participate in gas exchange

normal PCO₂ is ______ mmHg

40

we know in a pt w pneumonia, we can manipulate their PCO₂ through a ventilator, how do we manipulate (inc) their P_aO₂

we will inc the P_iO₂ specifically by inc the F_iO₂ by bumping the standard 21% to 100% O₂

in a person w pneumonia, how do we convert the alveoli that are not ventilating (dead space alveoli) to alveoli that can participate in gas exchange

killing off the offending agent w antibiotics to antivirals

in a pt w asthma, what is the primary problem

there is inc airway resistance due to bronchial smooth muscle contraction and hypertrophy, airway mucosal edema- overall narrowing the airway which will greatly impact exhalation

in a pt w asthma, why can accessory muscles be recruited for passive exhalation

pt is trying to maintain airflow normally on exhalation but due to the inc in resistance, the body needs to compensate by inc pressure gradient (driving pressure) between the alveolar space and atmosphere, this can be done by contracting abdominal muscles

is there anything wrong w this pts diaphragm

no, this is healthy!

is there anything wrong w this pts diaphragm

this is hyperinflated

what does hyperinflated mean when referring to the diaphragm

diaphragm is flat due to and inc in lung volume → air trapping

hyperinflation is a response mechanism to…

deal w inc resistance caused but can also be problematic in causing flattening of the diaphragm → dec diaphragms contractile efficiency → makes it more difficult for the pt to initiate breathing

what can cause air trapping in reference to hyperinflation

during an asthma episode, pt cannot completely exhale air with each breath so pt continues to retain air in his lungs, thus inc his lung volume