Neural control of respiration from Fishman

The respiratory control system, broadly speaking, comprises a controller, sensors, and a plan. This hierarchical structure, in which there is central processing of afferent input, is important for coordinating respiratory movements with behaviors such as eating, speaking, and moving. The controller is a neuronal network within the central nervous system (CNS), which is responsible for generating and modulating individual breaths and the overall breathing pattern. Often referred to as the respiratory central pattern generator (rCPG), the controller comprises reciprocally connected neuronal populations in the medulla and pons. Neural output from the rCPG drives the activity of various motor neuron pools. Motor neurons in the spinal cord (e.g., phrenic and intercostal) innervate the respiratory pump muscles, while brain stem motorneurons innervate upper airway muscles. The so-called “plant” is animportant component of breathing control and includes the CO2stores, which are made up of lung stores and circulating blood volume including hemoglobin. Closed loop feedback to the controller is supplied by chemoreceptors and mechanoreceptors. The consistent cycling of the ventilatory pattern is generated spontaneously from the spatial and functional architecture of the rCPG. Intrinsic membrane properties of rhythmically active neurons within the rCPG are capable of producing automatic periodicity.4 In addition, reciprocal (excitatory and inhibitory) synaptic connections between neuronal populations in the medulla and pons are believed to be critical for the automatic generation of the respiratory rhythm.

The neural respiratory cycle comprises three phases

Inspiration (I) involves ramp-like increases in inspiratory motor neuron firing, which drive phrenic nerve activity throughout this phase. The first phase of expiration (E1) is often called post-inspiration because inspiratory motor neurons are still active. Persistent inspira-
tory motor activity during E1, which declines throughout this phase, acts to slow the exit of air from the lungs. Finally, during the second phase of expiration (E2), expiratory muscles are typically electrically silent. During this phase of passive relaxation, gas is expelled as the
lungs and chest wall return to their equilibrium state (i.e., functional residual capacity). However, under conditions where respiratory drive is increased, expiratory muscles including the internal intercostal and abdominal muscles become active during E2. This notion is an
example of how the central controller, influenced by sensory feedback, modulates and alters the integrated motor response of the system.

SYSTEMIC SCLEROSIS - Diagnostic criteria

ACR/EULAR classification criteria for systemic sclerosis:

A total score of 9 or more is required for classification as systemic sclerosis.

1. Skin thickening of the fingers:

   - Proximal to the metacarpophalangeal joints (9 points).

2. Fingertip lesions:

   - Digital tip ulcers (2 points).

   - Fingertip pitting scars (3 points).

3. Telangiectasia (2 points).

4. Abnormal nailfold capillaries (2 points).

5. Pulmonary involvement:

   - Interstitial lung disease or pulmonary arterial hypertension (2 points).

6. Raynaud's phenomenon (3 points).

7. SSc-specific autoantibodies:

   - Anti-centromere, anti-topoisomerase I (Scl-70), or anti-RNA polymerase III (3 points).

SLE

SLE (American College of Rheumatology criteria )

1)Malar rash

2)Discoid rash

3)Photosensitivity skin rash

4)Oral or nasopharyngeal ulceration

5)Non erosive arthritis involving ≥ 2 peripheral joints

6)Serositis (pleuritis or pericarditis)

7)Renal disorder (persistent proteinuria or cellular casts)

8)Neurologic disorder (unexplained seizures or psychosis)

9)Hematologic disorder (hemolytic anemia, leukopenia, lymphopenia,or thrombocytopenia)

10)Immunologic disorder (positive LE cell, anti-DNA antibody, anti-Sm antibody, false-positive syphilis serology)

11)Elevated antinuclear antibodies

*Minimum of 4 criteria required

SJÖGREN SYNDROME

 sicca symptoms are mandatory

 supportive evidence including ocular signs (positive Schirmer test testing reduced tear formation, rose bengal score > 3 for staining of conjunction and cornea)

 typical histologic appearances salivary gland biopsy

antibodies to Ro (SS-A) or La (SS-B) or

 reduced salivary flow.

RHEUMATOID ARTHRITIS - Diagnostic criteria

American Rheumatism Association revised criteria

1)Morning stiffness (lasting at least 1 hr)

2)Arthritis (soft tissue swelling or fluid) of 3 or more joints (PIP, MCP,wrist, elbow, knee, ankle, MTP joints)

3)Arthritis of hand joints (swelling of at least 1 wrist, MCP, or PIP joint)

4)Symmetrical arthritis (i.e., simultaneous arthritis of the same joints on both sides of the body)

5)Rheumatoid nodules

6)Serum rheumatoid factor positivity (at a level such that < 5% of normal controls are positive)

7)Radiographic hand or wrist changes typical of rheumatoid arthritis

At least 4 criteria for a minimum of 6 weeks

Sjogren's syndrome

Classification criteria for sjogren's syndrome 

1) Labial salivary gland with focal lymphocytic sialadenitis and focus score of > 1 foci/4mm²    

        3 points

2) Anti-SS-A/Ro positive

        3 points

3) Ocular Staining Score 5 (or van Bijsterveld score > 4) in at least one eye

         1 point

4) Schirmer's test < 5 mm/5 minutes in at least one eye

         1 point

5) Unstimulated whole saliva flow rate < 0.1 ml/minute

          1 point

A score of 4 classifies a patient who meets the inclusion criteria:

⁃ ocular and/or oral dryness or suspicion of SjS according to EULAR SjS Disease Activity Index (ESSDAI)

and does not have any of the exclusion criteria:

⁃ history of head and neck radiation, active HCV infection, AIDS, sarcoidosis, amyloidosis, graft-versus-host disease, IgG4-related disease.

* ACR/EULAR classification criteria

AGGRAVATING FACTORS OF CARDINAL SYMPTOMS- MNEMONICS:

COUGH:

PDFCE 

Pollution, Pollen, Posture

Drugs, Diurnal, Dry air

Food

Cold weather, Common cold

Exercise

SPUTUM

 "DRIVE DUST"

 

D – Dust exposure

R – Respiratory infections

I – Irritants (e.g., smoke, fumes)

V – Viral infections

E – Exercise or exertion

D – Dry air

U – Upper respiratory tract conditions (e.g., postnasal drip)

S – Smoking

T – Temperature changes (cold air or sudden temperature drops)

Breathlessness: 

 "BREATHE HARD"

 

B – Body position (e.g., lying flat in orthopnea)

R – Respiratory infections

E – Exercise or exertion

A – Anxiety or emotional stress

T – Temperature extremes (cold or heat)

H – Hypoxia or high altitude

E – Environmental triggers (allergens, pollutants)

H – Heart failure or fluid overload

A – Anemia

R – Reflux (gastroesophageal reflux disease)

D – Drugs (e.g., beta-blockers, 

WHEEZE:

“BREATHE WHEEZE”

B – Bronchial irritants (smoke, pollution)

R – Respiratory infections (viral or bacterial)

E – Exercise

A – Allergens (pollen, dust mites, animal dander)

T – Temperature changes (cold air)

H – Hormonal changes (pregnancy, menstruation)

E – Emotions (stress, anxiety)

W – Workplace irritants (occupational exposures)

H – Household triggers (perfumes, cleaning agents)

E – Environmental changes (high altitude)

E – Exposure to drugs (NSAIDs, beta-blockers)

Z – Zzz… sleep (nocturnal asthma triggers)

E – Eating (GERD-induced wheeze)

CHEST PAIN:

“CHEST PAINS”

C – Coughing or deep breathing (pleuritic pain)

H – Heat or cold exposure (vasospastic angina)

E – Emotion or stress (psychogenic pain, angina)

S – Swallowing (esophageal causes like GERD or spasm)

T – Trauma or movement (musculoskeletal pain, costochondritis)

P – Physical exertion (angina, cardiac ischemia)

A – Alcohol or large meals (GERD or esophageal spasm)

I – Infections (pleuritis, pericarditis, pneumonia)

N – Nighttime (GERD-related pain due to supine position)

S – Specific postures (pericarditis, GERD, musculoskeletal pain)

HEMOPTYSIS:

“COUGH BLOOD”

C – Coughing (increases airway pressure, ruptures small vessels)

O – Overexertion (exacerbates vascular stress)

U – Upper respiratory tract infections

G – GERD or vomiting (irritation of airways)

H – High altitude (pulmonary hypertension)

B – Bronchial infections (bronchitis, bronchiectasis)

L – Lung malignancy (coughing or irritation)

O – Operations (post-procedural bleeding, e.g., bronchoscopy)

O – Oral anticoagulants (worsen bleeding)

D – Deep breaths or physical strain (ruptures fragile capillaries)

Aggravating and relieving factors for cough , breathlessness, chest pain:

 1. COUGH

Aggravating factors:

Pollution, Pollen, Posture

Drugs, Diurnal, Dry air

Cold weather, Common cold

Food, Exercise

Relieving Factors:

Using cough suppressants or expectorants

Drinking warm fluids, Humidified air or steam inhalation

Avoiding triggers, Rest

2. BREATHLESSNESS:

Aggravating factors:

Exercise, 

Pollens,dust,smoke,cold air

Drugs- Aspirin,NSAIDs can aggravate breathlessness in asthmatics

Orthopnea- LV failure, large pleural effusion,massive ascites, morbid obesity and any severe lung disease.

Platypnea- ASD, patent foramen ovale, large intrapulmonary shunt,hepatopulmonary syndrome

Trepopnea- Due to large unilateral lung disease(patient prefers healthy lung down), dilated cardiomyopathy (pt prefers right side down)

Tumors compressing major airways/blood vessels 

Relieving Factors:

Rest or reducing physical activity

Oxygen therapy 

Bronchodilators 

Calm breathing techniques 

Elevating the head or upper body in severe cases

3. CHEST PAIN

Aggravating Factors:

Deep breathing, coughing, sneezing (if pleuritic)

Physical exertion (if cardiac in nature)

Stress or anxiety

Movement or pressure on the chest area

acid reflux

Relieving Factors:

Rest 

Pain medication

Positioning (e.g., lying on one side for pleuritic pain)

Relaxation or stress-reduction techniques

Oxygen therapy

Aggravating and relieving factors for pedal edema

 Aggravating and relieving factors for pedal edema

Aggravating factor

Prolonged immobility

Dietary- excess fluid 

Reliving factor

Compression 

Limb elevation

Diet- fluid and sodium restriction 

Reference: Hutchison and macleod

Causes of orthopnoea

 CAUSES OF ORTHOPNEA :

1. Left ventricular failure.

2. Asthma

3. COPD

4. Bilateral diaphragmatic paralysis in the absence of heart disease.

Ref : Fraser 4th edition page no. 388

Breathlessness aggravating and relieving factors

 Breathlessness aggravated by exercise - exercise induced asthma

Aggravated by Pollens,dust,smoke,cold air, drugs, animals - Asthma 

Drugs- Aspirin,NSAIDs can aggravate breathlessness in asthmatics

Aggravated by lying down- orthopnea(relieved by sitting)- LV failure, large pleural effusion,massive ascites, morbid obesity and any severe lung disease.

Aggravated by sitting up- platypnea (relieved by lying down)- ASD, patent foramen ovale, large intrapulmonary shunt,hepatopulmonary syndrome 

Aggravated by lying on oneside - trepopnea

Due to large unilateral lung disease(patient prefers healthy lung down), dilated cardiomyopathy (pt prefers right side down)

Tumors compressing major airways/blood vessels 

Referrence - Macleod's 13 th edition 

Respiratory system page no-142