RESPIRATORY MEASUREMENT

Normal Respiratory Rates

AGE BREATHS/MIN

Newborn to 6 weeks 30 - 60

Infant (6 weeks to 6 months) 25 - 40

Toddler ( 1 to 3 years) 20 - 30

Young Children ( 3 to 6 years) 20 - 25

Older Children (10 to 14 years) 15 - 20

Adults 12 - 20

(Mosby’s Critical Care Nursing Reference, 2002; Perry & Potter, 2006)

1. Pulmonary ventilation- transport of gases to alveoli

2. Pulmonary diffusion- factors determining gas transport across the membrane

3. Perfusion

4. Ventilation/perfusion ratio

Gas transport in lungs

1. Partial pressure

2. Lung volumes and capacities

3. Alveolar ventilation

4. Anatomical and functional death space, effective ventilation

Pulmonary ventilation

Partial pressure of the gas

- in determined by its concentration in the mixture and by the overall pressure of the gas mixture

PatmO2 = Patm * FO2

PatmO2 = 740 torr * 0,21

- in the liquid - partial pressure of the gas component, which is balanced with the liquid

The partial pressure of a gas in a mixture is directly

related to its concentration. So since 0.04% of the gas

is CO2, its pressure will be 0.04% of the total pressure.

Convert 0.04% to its decimal equivalent by dividing 0.04

by 100, and then multiply that by 760 mmHg:

0.0004 X 760 = 0.304 mmHg is the partial pressure of

CO2.

O2 =21%

N2=78%

Lung volumes and capacities

tidal volume

inspiratory reserve volume

expiratory reserve volume

residual volume


• DEFINITION

• Lung volumes and lung capacities refers to the amount of air in the lungs during the different phases of respiratory cycle.

Lung volumes and capacities1. Lung volumes are directly measured.

2. Lung capacities are inferred from lung volumes.

• Lung volumes and capacities are measured

by SPIROMETER


• Lung volumes

• There are 4 lung volumes

• They do not mixup with each other.

• They can not be further divided

• When added together equal total lung capacity

Lung volumes and capacities• Basic Lung Volumes

• 1. Tidal Volume: TV

The amount of gas inspired or expired with each normal breath


• 2. Inspiratory Reserve Volume:

• (IRV)

Maximum amount of additional air that can be

inspired from the end of a normal inspiration.


• 3. Expiratory Reserve Volume: • (ERV)

The maximum volume of additional air that can be expired from the end of a normal expiration.


• 4. Residual Volume:

• (RV)

– The volume of air remaining in the lung after a maximal expiration.

– This is the only lung volume which cannot be measured


• Factors affecting lung volumes

• Several factors affect the lung volumes ,some important are the following

• Height of the person

• Altitude at which person lives

• Obesity


• Larger volumes

• taller people

• who live at higher altitudes

• non obese

• Smaller volumes

• shorter people

• people who live at lower altitudes

• obese

Lung volumes and capacities• 1. Total Lung Capacity:

• (TLC)

– The volume of air contained in the lungs at the end of a maximal inspiration.

– Called a capacity because it is the sum of the 4 basic lung volumes

– TLC= RV+IRV+TV+ERV

Lung volumes and capacities• 2. Vital Capacity: VC

– The maximum volume of air that can be forcefully expelled from the lungs following a maximal inspiration.

– It is the sum of inspiratory reserve volume, tidal volume and expiratory reserve volume.

– VC= IRV+TV+ERV

= TLC - RV

Lung volumes and capacities• 3. Functional Residual Capacity (FRC):

– The volume of air remaining in the lung at the end of a normal expiration.

– FRC= RV+ERV


• 4. Inspiratory Capacity (IC) :

–Maximum volume of air that can be inspired from end expiratory position.

– IC= TV+IRV


• IMPORTANT TO REMEMBER1. Tidal volume,

2. Expiratory reserve volume

3. Vital capacity,

4. Inspiratory capacity

• can be measured directly with a SPIROMETER

• These are the basic elements of a PULMONARY FUNCTION TEST


• IMPORTANCE OF LUNG VOLUMES AND CAPACITIES

• Clinically lung volumes and capacities are important in diagnosis of various pulmonary problems but more significant in diagnosis of obstructive and restrictive diseases.


OBSTRUCTIVE DISEASES

• In obstructive diseases patient is unable to exhale all the air out of lungs which results in INCREASED RESIDUAL VOLUME


RESTRICTIVE LUNG DISEASES

• In restrictive lung diseases patient is unable to take the sufficient air into the lungs which results in DECREASE TOTAL

LUNG CAPACITY


Spirometer - measurement of lung volumes- measurement of the oxygen consumption

Measurement of residual volume and FRC- helium equilibration method

Uneven ventilation Inaccurate measurement

C1 * V1 C2 * (V1 + V2)

Measurement of functional residual capacity- pletysmograph

Boyl´s law: P * V = const

P1* V1 = P1´* (V1 - dV)

P2* V2 = P2´* (V2 + dV)

V2 = FRC

P1* V1

P2* V2

Alveolar ventilation

02

C02

ventilation of anatomic dead space

inspiration expiration

Alveolar ventilation. = (tidal volume - dead space) * respiratory rate.

Alveolar ventilation

Relationship between tidal volume, frequency and effective ventilation

Minuteventilation

ml/min

Tidalvolume

ml

Frekvencyc/s

AlveolarVentilation

ml/min

VentilationAnat. dead

spaceml/min

Effectiveventilation

%

8000 250 32 3200 4800 40

8000 500 16 5600 2400 70

8000 1000 8 6800 1200 85

Why not to breathe with minimal frequency?

Work of breathing

Physiologic dead spaceventilated but not perfused alveoli

PECO2 PACO2 PaCO2

VT

VA

VAeff

ventilation of anatomic dead space

ventilation of physiologic dead space

VD

VT

=PaCO2 PECO2

PaCO2

-Bohr equation

Uneven ventilation

The worst ventilation - apical parts

- lung volumes measurable by spirometer (VT,IRV,ERV)

- RV, FRC - measurable by He, plethysmograph

- anatomic dead space

- effective ventilation and respiratory frequency, work of breathing

- physiologic dead space,

Summary

RESPIRATORY MEASUREMENT

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