[RS] Q.14 What is FEV1 ?

Ans.

FEV1 (Forced expiratory volume):

Definition : The volume of air expired forcefully at one second is called forced expiratory volume. It is also know as timed vital capacity.

Normal value: (In a normal person FEV1 is more than 80% in one second):

1.     FEV1 is – 80% of vital capacity in first second (FEV1 /FVC %).

2.     FEV1 is – 93% of vital capacity in 2 second.

3.     FEV1 is – 97% of vital capacity in 3 second.

[RS] Q.13 Define vital capacity(VC), factors affecting vital capacity

 Ans.

Vital capacity: (FVC or FEV)

The maximum amount of air that a person can expire forcefully after a forceful inspiration is called vital capacity (VC).

Amount – about 4600 ml.

Factors affecting vital capacity:

       1)    Age – It more in young.

       2)    Sex – 20-25% less is female.

       3)    Surface area – It is proportional to surface area.

       4)    Posture – Lying – Lowest (↑ Pulmonary blood volume)

                             Sitting – More than lying

                             Standing – Highest

5)          Strength of respiratory muscles - More the strength, more vital capacity such as athletes.

6)          Disease in the lungs and pleura causes decrease vital capacity such as-

·  Tuberculosis

·  Ch. Asthma

·  Ch. Bronchitis

·  Pulmonary edema, etc.

Importance:

It is an index of lung function and provides useful information about-

a)           Abnormal ventilation due to airway obstruction, fibrosis of lungs.

b)          Mechanical interference with chest expansion and compression.

c)           Strength of respiratory muscles.

[RS] Q.12 Types of dead space.

Ans.

1)  Anatomical dead space: (By fowler’s method)

The volume of gas that remains in all space of respiratory system other than the alveoli and other closely related gas exchange areas, this space is called anatomical dead space.

2)    Physiological dead space: (By Bohr’s equation)

When the alveolar dead space is included with total measurement of dead space is called physiological dead space.

Normally the anatomical and physiological dead space are equal but in person with partially functional or nonfunctional alveoli is some parts of lungs, the physiological dead space will be greater than anatomical dead space. (10 times or 1 to 2 liters).

[RS] Q.11 What is Dead space and Dead space air?

 Ans.

Dead space:

The space in the respiratory passage occupied by gas but does not take part in gaseous exchange but only acts as a reservoir of air is called dead space.

Dead space air:

The amount of air remains in the respiratory passages and does not part in gaseous exchange called dead space air. It is about 150 ml.

[RS] Q.10 What is Pulmonary ventilation, alveolar ventilation, minute respiratory volume ?

Ans.

i)     Pulmonary ventilation:

It means the inflow and out flow of air between the atmosphere and lungs alveoli per minute.

ii)    Alveolar ventilation:

It means the volume of air that enters into the respiratory zone per minute and participates in the gas exchange.

VA   = (VT-VD) Freq.

       = (500-150) × 12      

     = 4200 ml/min.

     = 4.2 L /min.

VA= Alveolar ventilation

VT = Tidal volume= 500ml

VD= Dead space volume (physiological)=150ml

Freq.= Frequency of respiration per minute (respiratory rate)= avg. 12 breaths/min.)

  

iii)   Minute respiratory volume:

It is the total amount of new air moved into the respiratory passages each minute.

Minute res. Volume       = V_T × RR   ( Here, Tidal vol. = 500 ml, Res. rate = 12 breaths/min)

                                      = 500 × 12

                                      = 6000 ml/min.

                                      = 6 Liters/min.

[RS] Q.9 Some terms:

Eupnoea – Means normal breathing.

Tachypnoea – Means rapid breathing than normal.

Bradypnoea – Means slow breathing than normal.

Apnoea – Means temporary cessation of breathing.

Dyspnoea – Means difficulty in breathing.

Hypoxia – Means lack of O2 at tissue level.

Anoxia – Means total lack of O2.

Hypercapnia – Means excess CO2 is blood.

Hypocapnia – Means decrease CO2 is blood.

[RS] Q.8 What is Respiratory distress syndrome (Hyaline membrane disease)?

 Ans.

Many premature babies have little or no surfactant in the alveoli when they are born and their lungs have an extreme tendency to collapse, sometimes as great as six to eight times that in a normal adult person this condition is called respiratory distress syndrome.

[RS]Q.7 What is surfactant give its composition and important

Ans.

Surfactant:

It is a surface active agent in water of lung alveoli which greatly reduces the surface tension of the fluid lining the lung alveoli, composed of several phospholipid, proteins and ions and secreted by special surfactant secreting epithelial cells called type-II alveolar cells.

Composition:

·  Phospholipid – dipalmitoyl phosphatidycholine.

·  Surfactant apoproteins

·  Calcium ions

Importance:

Ø                 Surfactant decrease the surface tension of the fluid lining the alveoli          thus prevents the lungs collapse.

Ø                 It helps in the expansion of lungs of a new born babies.

Ø                 It stabilizes the size of alveoli.

Ø                 It prevents the accumulation of edema fluid in alveoli.

[RS]Q.6 Compliance of the Lungs:

 Ans.

The extent to which the lungs will expand for each unit increase in transpulmonary pressure is called lung compliance.

It is about 200 ml of air/cm of H2O transpulmonary pressure. That is, every time the trauspulmonary pressure increase 1cm of H2O, the lung volume will expand 200 ml.

Importance:

·  In restrictive lung disease, lung compliance reduced.

·  In obstructive lung disease, lung compliance Increased.