It may have escaped your notice, but the current series of one of 2010's best comedies quietly came to an end last night. Set in a careworn NHS geriatric ward, Getting On has drawn critical acclaim, but negligible viewing figures.

While I appreciate that a rawly naturalistic tragicomedy suffused with the stench of sickness and mortality will never be a ratings blockbuster, it would be nice to see more love for this overlooked gem.

Written by and starring Joanna Scanlan, Vicki Pepperdine and former psychiatric nurse Jo Brand, Getting On is the antithesis of your average mainstream medical confection: a defiantly unglamorous depiction of Britain's healthcare system, staffed not by selfless angels, but by flawed human beings muddling through as best they can under thankless circumstances. Skating deftly on a hairpin between comedy and pathos, it depicts a profession in which the abiding concerns are bureaucracy, people management and death.

This was never more strikingly illustrated than in the scenes in which the elderly Scottish woman who had been slowly dying throughout the series, finally, inevitably expired. Her poor daughter, unable to accept what had happened, tearfully and tetchily instructed her to wake up, as if it was all just a sick joke: a heartbreaking sketch of grief, emblematic of the programme's understatement.

Sister Den (Scanlan) and Nurse Kim (Brand) went through the practiced motions of comforting the bereaved and dealing with the deceased. But they also argued over what to do with the dead woman's untouched lunch.

Keen to vacate another much-needed bed, Den told the bewildered daughter that the body had to be moved immediately. She was bundled from the hospital to deal with her pain elsewhere, while her mother was abruptly wheeled away in full view of the other patients. As a blunt, desperately sad illustration of Getting On's core themes of life's cyclical grind and the pragmatic demands of NHS medical care, it couldn't have been bettered.

Director Peter Capaldi - Scanlan's co-star from The Thick of It, of which this is a spiritual relative - is to be commended for his sensitive handling of this material. His appropriately sickly, washed-out colour palette and the authentic performances from his excellent cast combine to create a bleakly enthralling atmosphere unlike any other British sitcom.

Doesn't sound like a laugh riot? Well no, it isn't, but nor is it trying to be. The humour arises naturally from character, the situations rooted in reality. Getting On is poignant, funny, profound even. Here's hoping for a speedy return.

The relentlessly deadpan comedy about life on a geriatric ward continues and as ever there are some uneasy and touching moments amid the scatological humour. In tonight's penultimate episode of the series, a graduate nurse causes friction between Den (Joanna Scanlan) and Kim (Jo Brand), and Beedy Fyvie (Lindy Whiteford), who has been travelling from Scotland to visit her dying mother, is once again pushed aside by the dismissive management staff. Elsewhere, Pippa (Vicki Pepperdine) suffers the humiliation of having to reapply for her own job.

Getting On review

Getting On would seem to scotch any lingering prejudice that women are less funny than men. Principals Jo Brand, Joanna Scanlan and Vicky Pepperdine also wrote the partly ad-libbed show, and bring to life a comedy of the half-resented, half-generous sacrifices of dedication.

Brand plays nursing auxiliary Kim, supervised by Scanlan as Sister Den Flixter; both engage in constant half-cock skirmishes with consultant Pippa Moore (Pepperdine). The show has grasped and exploits a deeper-than-surface reality: that the health service, shorn of a chain of clear command, is a place of overlapping baronies that must bargain with each other for time and resources.

Thus, in last week's episode, Kim has Sister Den assigned to assist her as a moonlighting agency nurse in the middle of the night - and the two struggle over who has the right to give orders.

At the same time, Dr Moore seeks Kim's aid as a witness to an "inappropriate incident" earlier and is stymied because Kim "doesn't like legal things". Where "do it because I say so" is absent, a low-level insubordination, which is also an assertion of dignity, spreads like a fungus - and in that is the comedy.

An extremely fragrant patient was heaved in to B4, where Jo Brand and Joanna Scanlan were discovering that the multi-disciplinary approach to care doesn't really work when beds, trolleys and the rest aren't multi at all. They write the show with Vicki Pepperdine, who steals the acting honours as the useless doctor. Director Peter Capaldi's wobbly camera appears to be mounted on a drip stand with a wheel missing.

Virtue has been rewarded with a return to the schedules for BBC4's dark and unglamorous hospital comedy Getting On, launched last year with three superbly measured episodes of low-key wit and broad hilarity. Who (of the 19 people who saw it) can forget the fun had with the self-important Dr Moore's faecal stool research programme or the eloquently brief wrangling over the ethics of eating a dead woman's birthday cake, or those oases of tedium, ticking with wicked purpose.

The first thing I noticed, though - even as the great Richard Hawley title song lulled us into the new series - was how healthily Daz blue everything looked. Here came the familiar cameras, zooming and retreating in homage to The Thick of It (courtesy of director Peter Capaldi), but where was the bilious washed-out decor and bad complexions and air of neglect? Had the MRSA police been in with the Mr Muscle and a lick of paint? Had someone been ironing the uniforms?

It soon began to ooze some of the old malodorous promise with the arrival of a comatose female of no fixed abode smelling like "an every-orifice cocktail", as dogsbody nurse Kim (mistress of droll, Jo Brand) put it, vying with ward sister Den (Joanna Scanlan) for best evocative observation of human pungency. Something was rotten down there...

There was more laughter to be milked out of it with the entrance of no-nonsense consultant Dr Moore (the excellent Vicki Pepperdine), blind to preposterousness as she urged her retinue of horrified dimwit trainees to peer into the poor woman's back passage and see a valuable learning opportunity. "So... perineal abscess? Rectal prolapse? Anal fistulae?" It was funny, but it did start to dribble away into a dull scene about the new gerontology wing, only to be picked up again by Donald the porter, trying to offload the offending patient on other unwilling departments, his gurney journeying back and forth with diminishing comic power. By the time he parked it in the corridor the only smell I could detect was the new lino.

To be fair there were entertaining skirmishes but they lacked the friction that gave the last series its crackling energy. Den has lost her fear of the officious Dr Moore. Sexually bi-curious matron Hilary - a monster of neuroses held in check by self-help psychobabble - has been stripped of his menace (like Samson before him, I believe) by the blowjob Den gave him in the back of a taxi. And where were the delicious lingual infelicities, the absurdities of NHS jargon, the workplace correctness that left Kim floundering in useless common sense - the whole pickle of moral compromise without which drama can be neither funny nor tragic? Perhaps it will all be back next week. I hope so.

The wobbly camerawork, as if shot by a team of four-year-olds who have run off with the digicam; the mournfully drab municipal setting; the absence, God forbid, of a laugh track; the studiedly natural dialogue. The Office begat The Thick Of It which begat this, a downbeat comedy set on an anonymous NHS ward. It came as no surprise that this, the first episode of the second series (I've come to it late), was directed by Peter Capaldi and starred Joanna Scanlan - each a first-class honours graduate of the Armando Iannucci school of comedy.

And this, being the series opener, it was appropriate that this most self-effacing of entertainments kept the action to the bare minimum. An unconscious old homeless person was admitted whom neither Nurse Den Flixter (Joanna Scanlan) nor her underling Kim Wilde (Jo Brand) really wanted to deal with. A little later, a woman visited her ailing mother and challenges Dr Pippa Moore (Vicki Pepperdine) about the level of pain relief available. That was it. The comedy, such as it was, peeped out from the fraught exchanges between Den, Dr Moore and the male Matron Hilary (Ricky Grover) as they tussled for the upper hand among the dank beds and grey windows. Kim meanwhile rolled her eyes and tried to keep out of trouble.

Yet, days later, it's not the comedy that stays with you, but the show's portrait of the NHS in miniature. Brand, Pepperdine and Scanlan are co-writers, and one assumes Brand's early career as a psychiatric nurse keeps the tone right, if not the up-to-the-minute detail. The passage of the homeless woman from Kim and Den, to the reluctant care of a junior house officer, to the corridor as they try to offload her on another ward was as understandable as it was distressing. Similarly, a well-informed woman's request that her mother's meds be amped up wasn't so much wryly amusing as it was useful - so that, you thought, is how you get someone to pay you proper attention: bone up on the internet, be endlessly polite and don't let them off the hook.

Getting On is notable for its delicacy. Set in a geriatric ward, it's astonishingly bleak for a comedy and comes shot in wintry shades of blue and grey. However, it never revels in its grimness, but rather uses the proximity of disease and death as a wall to bounce its humour off.

Everything about it feels carefully - and perfectly - judged: the ghastly patronising doctor (Vicki Pepperdine) telling one of her juniors to 'have a root around' in the prostate form of a very smelly tramp, the ward sister (Joanna Scanlan) bossily refusing to admit the sister of a patient outside visiting hours, and then almost swooning in the presence of the lavishly camp male nurse, Hilary (Ricky Grover). Here is human nature - in its frailties, its contradictions and its efforts to keep desperation at bay.

It doesn't happen very often that we invent new ways of laughing at ourselves, but I think you could make a case that the awkward silence is a peculiarly contemporary mode of comedy. It's not that you can't find any antique instances of the humour of speechless embarrassment. It's just that it's only recently become one of the standard forms for which a sitcom can reach. It has its own associated visual style - that of hand-held documentary realism - and carries its own implication, which is that any programme that employs it is operating in that fertile (and upmarket) borderland between sitcom and drama. And Getting On - Jo Brand, Joanna Scanlan and Vicki Pepperdine's comedy about life on a geriatric ward - is a perfect example. It even has one of the style's most characteristic markers: a signature tune that is ostentatiously melancholy and distinctly retro (in this case Richard Hawley's "Roll River Roll"). Where a traditional sitcom tune would unleash the bassoons and brass and try to parp you into hilarity, this kind of theme song gives you permission to laugh ruefully - which will sometimes mean not laughing at all, but simply adopting an expression which sits somewhere between a grin and a wince.

None of this is meant to imply that Getting On is anything but excellent, only that it follows the trail blazed by a comedy like The Office, where the punchline often lay in the fact that a character couldn't think of what to say next and the dialogue dribbled to an excruciating halt. There was a textbook example here, in a scene where Pepperdine's odiously brisk Doctor Moore was sparring with a patient's relative over a course of treatment. Why isn't she being given Drug X, asks the anxious relative. Because it's not an appropriate drug at this point and I will make the clinical decisions, replies Doctor Moore, professional affront expanding like a lizard's neck ruff. Drug X is quite unsuitable for her current condition, she insists pompously. At which point, Sister Den (Scanlan) interjects to point out that the patient is actually being given Drug X and the scene ends in stammering damage limitation. Getting On is full of such embarrassments, beautifully acted and excruciatingly awkward.

There are more straightforward writing pleasures, too, last night mostly centring on a homeless patient with a perianal abscess, who arrives accompanied by an odour strong enough to discolour the curtains. "It's a kind of every-orifice cocktail," gasps Nurse Kim (Brand), blinking in the fumes as they undress her. "Can we just stop there and get used to that layer?" Then she pauses, distracted by a moment of nostalgia when it turns out that one of the patient's undergarments is a sheet of tabloid newspaper describing Dirty Den's webcam sex scandal (a story that broke in 2004). And if that sounds cruel, it wasn't - just an entirely plausible blend of black humour and grim reality, delivered with a fine grasp of understatement. Sometimes it's a beat or two before you even notice that a joke has been made.

Three episodes were simply not enough for the first series of Jo Brand, Joanna Scanlan and Vicki Pepperdine's beautifully observed black comedy set in a NHS geriatric ward. Now it's back with a series that's twice as long, opening with the three once again running around straitjacketed by pointless protocol as a pongy homeless woman is wheeled through the doors of B4.

As an antidote to the glamour, heroics and sexual intrigue of Holby City, Getting On's black hospital humour is as startling as a cold bed pan.

Fans who clamoured for more of this hospital sitcom after the first mini-dose of just three episodes will be delighted to know it's back for six more weeks of agonising mirth.

Tonight opens with a typical patient dilemma for Nurse Kim Wilde and Sister Flixter (Jo Brand and Joanna Scanlan). An unidentified woman has been brought in who, in medical terms, can only be described as a stinky old tramp. Or, as the briskly ineffectual Dr Moore (Vicki Pepperdine) describes her condition: "Odour Plus, Plus".

Dr Moore is also eager to show her terrifyingly gormless student doctors the designs for the gleaming new hospital wing - complete with sculptures by Antony Gormley - that will make not one scrap of difference to the suffering of the patients and their families - or, indeed, any of the staff.

While Holby's eye-liner budget alone would probably pay a nurse's salary for a year, Getting On's depiction of life on ward B4 is so grimly realistic that you feel you should keep a bottle of anti-bacterial hand-wash next to the remote.

What it's doing languishing in a sideroom on BBC4 while Reggie Perrin basks in the private-ward comfort of BBC1 is frankly a mystery.